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RFC 4171 - Internet Storage Name Service (iSNS)


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Network Working Group                                           J. Tseng
Request for Comments: 4171                           Riverbed Technology
Category: Standards Track                                     K. Gibbons
                                                      McDATA Corporation
                                                           F. Travostino
                                                                  Nortel
                                                             C. Du Laney
                                             Rincon Research Corporation
                                                                J. Souza
                                                               Microsoft
                                                          September 2005

                 Internet Storage Name Service (iSNS)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document specifies the Internet Storage Name Service (iSNS)
   protocol, used for interaction between iSNS servers and iSNS clients,
   which facilitates automated discovery, management, and configuration
   of iSCSI and Fibre Channel devices (using iFCP gateways) on a TCP/IP
   network.  iSNS provides intelligent storage discovery and management
   services comparable to those found in Fibre Channel networks,
   allowing a commodity IP network to function in a capacity similar to
   that of a storage area network.  iSNS facilitates a seamless
   integration of IP and Fibre Channel networks due to its ability to
   emulate Fibre Channel fabric services and to manage both iSCSI and
   Fibre Channel devices.  iSNS thereby provides value in any storage
   network comprised of iSCSI devices, Fibre Channel devices (using iFCP
   gateways), or any combination thereof.

Table of Contents

   1.  Introduction................................................... 6
       1.1.  Conventions Used in This Document........................ 6
       1.2.  Purpose of This Document................................. 6
   2.  iSNS Overview.................................................. 6
       2.1.  iSNS Architectural Components ........................... 7
             2.1.1.  iSNS Protocol (iSNSP) ........................... 7
             2.1.2.  iSNS Client...................................... 7
             2.1.3.  iSNS Server...................................... 7
             2.1.4.  iSNS Database ................................... 7
             2.1.5.  iSCSI............................................ 7
             2.1.6.  iFCP............................................. 7
       2.2.  iSNS Functional Overview................................. 8
             2.2.1.  Name Registration Service........................ 8
             2.2.2.  Discovery Domain and Login Control Service....... 8
             2.2.3.  State Change Notification Service............... 10
             2.2.4.  Open Mapping between
                     Fibre Channel and iSCSI Devices................. 11
       2.3.  iSNS Usage Model........................................ 11
             2.3.1.  iSCSI Initiator................................. 12
             2.3.2.  iSCSI Target.................................... 12
             2.3.3.  iSCSI-FC Gateway................................ 12
             2.3.4.  iFCP Gateway.................................... 12
             2.3.5.  Management Station.............................. 12
       2.4.  Administratively Controlled iSNS Settings............... 13
       2.5.  iSNS Server Discovery .................................. 14
             2.5.1.  Service Location Protocol (SLP)................. 14
             2.5.2.  Dynamic Host Configuration Protocol (DHCP)...... 14
             2.5.3.  iSNS Heartbeat Message.......................... 14
       2.6.  iSNS and Network Address Translation (NAT).............. 14
       2.7.  Transfer of iSNS Database Records between iSNS Servers.. 15
       2.8.  Backup iSNS Servers..................................... 17
       2.9.  Transport Protocols..................................... 19
             2.9.1.  Use of TCP for iSNS Communication............... 19
             2.9.2.  Use of UDP for iSNS Communication............... 20
             2.9.3.  iSNS Multicast and Broadcast Messages........... 20
       2.10. Simple Network Management Protocol (SNMP) Requirements.. 21
   3.  iSNS Object Model............................................. 21
       3.1.  Network Entity Object .................................. 22
       3.2.  Portal Object .......................................... 22
       3.3.  Storage Node Object..................................... 22
       3.4.  Portal Group Object..................................... 23
       3.5.  FC Device Object........................................ 24
       3.6.  Discovery Domain Object................................. 24
       3.7.  Discovery Domain Set Object............................. 24
       3.8.  iSNS Database Model..................................... 24
   4.  iSNS Implementation Requirements.............................. 25

       4.1.  iSCSI Requirements...................................... 25
             4.1.1.  Required Attributes for Support of iSCSI........ 26
             4.1.2.  Examples: iSCSI Object Model Diagrams........... 28
             4.1.3.  Required Commands and
                     Response Messages for Support of iSCSI.......... 30
       4.2.  iFCP Requirements....................................... 31
             4.2.1.  Required Attributes for Support of iFCP......... 31
             4.2.2.  Example: iFCP Object Model Diagram.............. 32
             4.2.3.  Required Commands and
                     Response Messages for Support of iFCP........... 34
   5.  iSNSP Message Format.......................................... 35
       5.1.  iSNSP PDU Header........................................ 35
             5.1.1.  iSNSP Version................................... 36
             5.1.2.  iSNSP Function ID............................... 36
             5.1.3.  iSNSP PDU Length................................ 36
             5.1.4.  iSNSP Flags..................................... 36
             5.1.5.  iSNSP Transaction ID............................ 36
             5.1.6.  iSNSP Sequence ID............................... 37
       5.2.  iSNSP Message Segmentation and Reassembly............... 37
       5.3.  iSNSP PDU Payload....................................... 37
             5.3.1.  Attribute Value 4-Byte Alignment................ 38
       5.4.  iSNSP Response Status Codes............................. 39
       5.5.  Authentication for iSNS Multicast and Broadcast Messages 39
       5.6.  Registration and Query Messages......................... 41
             5.6.1.  Source Attribute................................ 42
             5.6.2.  Message Key Attributes.......................... 42
             5.6.3.  Delimiter Attribute............................. 42
             5.6.4.  Operating Attributes............................ 43
             5.6.5.  Registration and Query Request Message Types ... 44
       5.7.  Response Messages....................................... 66
             5.7.1.  Status Code..................................... 66
             5.7.2.  Message Key Attributes in Response.............. 66
             5.7.3.  Delimiter Attribute in Response................. 67
             5.7.4.  Operating Attributes in Response................ 67
             5.7.5.  Registration and Query Response Message Type.... 67
       5.8.  Vendor-Specific Messages................................ 72
   6.  iSNS Attributes............................................... 73
       6.1.  iSNS Attribute Summary.................................. 73
       6.2.  Entity Identifier-Keyed Attributes...................... 76
             6.2.1.  Entity Identifier (EID)......................... 76
             6.2.2.  Entity Protocol................................. 76
             6.2.3.  Management IP Address .......................... 77
             6.2.4.  Entity Registration Timestamp .................. 77
             6.2.5.  Protocol Version Range.......................... 77
             6.2.6.  Registration Period............................. 78
             6.2.7.  Entity Index.................................... 78
             6.2.8.  Entity Next Index............................... 79
             6.2.9.  Entity ISAKMP Phase-1 Proposals................. 79

             6.2.10. Entity Certificate.............................. 79
       6.3.  Portal-Keyed Attributes................................. 80
             6.3.1.  Portal IP Address............................... 80
             6.3.2.  Portal TCP/UDP Port............................. 80
             6.3.3.  Portal Symbolic Name............................ 80
             6.3.4.  Entity Status Inquiry Interval.................. 81
             6.3.5.  ESI Port........................................ 82
             6.3.6.  Portal Index.................................... 82
             6.3.7.  SCN Port........................................ 82
             6.3.8.  Portal Next Index............................... 83
             6.3.9.  Portal Security Bitmap.......................... 83
             6.3.10. Portal ISAKMP Phase-1 Proposals................. 84
             6.3.11. Portal ISAKMP Phase-2 Proposals................. 84
             6.3.12. Portal Certificate.............................. 84
       6.4.  iSCSI Node-Keyed Attributes............................. 84
             6.4.1.  iSCSI Name...................................... 85
             6.4.2.  iSCSI Node Type................................. 85
             6.4.3.  iSCSI Node Alias................................ 86
             6.4.4.  iSCSI Node SCN Bitmap .......................... 86
             6.4.5.  iSCSI Node Index................................ 87
             6.4.6.  WWNN Token...................................... 87
             6.4.7.  iSCSI Node Next Index .......................... 89
             6.4.8.  iSCSI AuthMethod................................ 89
       6.5.  Portal Group (PG) Object-Keyed Attributes............... 89
             6.5.1.  Portal Group iSCSI Name......................... 90
             6.5.2.  PG Portal IP Addr............................... 90
             6.5.3.  PG Portal TCP/UDP Port.......................... 90
             6.5.4.  Portal Group Tag (PGT).......................... 90
             6.5.5.  Portal Group Index.............................. 90
             6.5.6.  Portal Group Next Index......................... 91
       6.6.  FC Port Name-Keyed Attributes .......................... 91
             6.6.1.  FC Port Name (WWPN)............................. 91
             6.6.2.  Port ID (FC_ID)................................. 91
             6.6.3.  FC Port Type.................................... 92
             6.6.4.  Symbolic Port Name.............................. 92
             6.6.5.  Fabric Port Name (FWWN)......................... 92
             6.6.6.  Hard Address.................................... 92
             6.6.7.  Port IP Address................................. 92
             6.6.8.  Class of Service (COS).......................... 93
             6.6.9.  FC-4 Types...................................... 93
             6.6.10. FC-4 Descriptor................................. 93
             6.6.11. FC-4 Features .................................. 93
             6.6.12. iFCP SCN Bitmap................................. 93
             6.6.13. Port Role....................................... 94
             6.6.14. Permanent Port Name (PPN)....................... 95
       6.7.  Node-Keyed Attributes .................................. 95
             6.7.1.  FC Node Name (WWNN)............................. 95
             6.7.2.  Symbolic Node Name.............................. 95

             6.7.3.  Node IP Address................................. 95
             6.7.4.  Node IPA........................................ 96
             6.7.5.  Proxy iSCSI Name................................ 96
       6.8.  Other Attributes........................................ 96
             6.8.1.  FC-4 Type Code.................................. 96
             6.8.2.  iFCP Switch Name................................ 96
             6.8.3.  iFCP Transparent Mode Commands.................. 97
       6.9.  iSNS Server-Specific Attributes......................... 97
             6.9.1.  iSNS Server Vendor OUI.......................... 98
       6.10. Vendor-Specific Attributes.............................. 98
             6.10.1. Vendor-Specific Server Attributes............... 98
             6.10.2. Vendor-Specific Entity Attributes............... 98
             6.10.3. Vendor-Specific Portal Attributes............... 99
             6.10.4. Vendor-Specific iSCSI Node Attributes........... 99
             6.10.5. Vendor-Specific FC Port Name Attributes......... 99
             6.10.6. Vendor-Specific FC Node Name Attributes......... 99
             6.10.7. Vendor-Specific Discovery Domain Attributes..... 99
             6.10.8. Vendor-Specific Discovery Domain Set Attributes. 99
             6.10.9. Other Vendor-Specific Attributes................ 99
       6.11. Discovery Domain Registration Attributes............... 100
             6.11.1. DD Set ID Keyed Attributes..................... 100
             6.11.2. DD ID Keyed Attributes......................... 101
   7.  Security Considerations...................................... 103
       7.1.  iSNS Security Threat Analysis ......................... 103
       7.2.  iSNS Security Implementation and Usage Requirements.... 104
       7.3.  Discovering Security Requirements of Peer Devices...... 105
       7.4.  Configuring Security Policies of iFCP/iSCSI Devices.... 106
       7.5.  Resource Issues........................................ 107
       7.6.  iSNS Interaction with IKE and IPSec.................... 107
   8.  IANA Considerations.......................................... 107
       8.1.  Registry of Block Storage Protocols.................... 107
       8.2.  Registry of Standard iSNS Attributes .................. 108
       8.3.  Block Structure Descriptor (BSD) Registry.............. 108
   9.  Normative References......................................... 109
   10. Informative References....................................... 110
   Appendix A: iSNS Examples........................................ 112
       A.1.  iSCSI Initialization Example........................... 112
             A.1.1.  Simple iSCSI Target Registration............... 112
             A.1.2.  Target Registration and DD Configuration....... 114
             A.1.3.  Initiator Registration and Target Discovery.... 117
   Acknowledgements................................................. 121

1.  Introduction

1.1.  Conventions Used in This Document

   "iSNS" refers to the storage network model and associated services
   covered in the text of this document.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   All frame formats are in big endian network byte order.

   All unused fields and bitmaps, including those that are RESERVED,
   SHOULD be set to zero when sending and ignored when receiving.

1.2.  Purpose of This Document

   This is a standards track document containing normative text
   specifying the iSNS Protocol, used by iSCSI and iFCP devices to
   communicate with the iSNS server.  This document focuses on the
   interaction between iSNS servers and iSNS clients; interactions among
   multiple authoritative primary iSNS servers are a potential topic for
   future work.

2.  iSNS Overview

   iSNS facilitates scalable configuration and management of iSCSI and
   Fibre Channel (FCP) storage devices in an IP network by providing a
   set of services comparable to that available in Fibre Channel
   networks.  iSNS thus allows a commodity IP network to function at a
   level of intelligence comparable to a Fibre Channel fabric.  iSNS
   allows the administrator to go beyond a simple device-by-device
   management model, where each storage device is manually and
   individually configured with its own list of known initiators and
   targets.  Using the iSNS, each storage device subordinates its
   discovery and management responsibilities to the iSNS server.  The
   iSNS server thereby serves as the consolidated configuration point
   through which management stations can configure and manage the entire
   storage network, including both iSCSI and Fibre Channel devices.

   iSNS can be implemented to support iSCSI and/or iFCP protocols as
   needed; an iSNS implementation MAY provide support for one or both of
   these protocols as desired by the implementor.  Implementation
   requirements within each of these protocols are further discussed in
   Section 5.  Use of iSNS is OPTIONAL for iSCSI and REQUIRED for iFCP.

2.1.  iSNS Architectural Components

2.1.1.  iSNS Protocol (iSNSP)

   The iSNS Protocol (iSNSP) is a flexible and lightweight protocol that
   specifies how iSNS clients and servers communicate.  It is suitable
   for various platforms, including switches and targets as well as
   server hosts.

2.1.2.  iSNS Client

   iSNS clients initiate transactions with iSNS servers using the iSNSP.
   iSNS clients are processes that are co-resident in the storage
   device, and that can register device attribute information, download
   information about other registered clients in a common Discovery
   Domain (DD), and receive asynchronous notification of events that
   occur in their DD(s).  Management stations are a special type of iSNS
   client that have access to all DDs stored in the iSNS.

2.1.3.  iSNS Server

   iSNS servers respond to iSNS protocol queries and requests, and
   initiate iSNS protocol State Change Notifications.  Properly
   authenticated information submitted by a registration request is
   stored in an iSNS database.

2.1.4.  iSNS Database

   The iSNS database is the information repository for the iSNS
   server(s).  It maintains information about iSNS client attributes.  A
   directory-enabled implementation of iSNS may store client attributes
   in an LDAP directory infrastructure.

2.1.5.  iSCSI

   iSCSI (Internet SCSI) is an encapsulation of SCSI for a new
   generation of storage devices interconnected with TCP/IP [iSCSI].

2.1.6.  iFCP

   iFCP (Internet FCP) is a gateway-to-gateway protocol designed to
   interconnect existing Fibre Channel and SCSI devices using TCP/IP.
   iFCP maps the existing FCP standard and associated Fibre Channel
   services to TCP/IP [iFCP].

2.2.  iSNS Functional Overview

   There are four main functions of the iSNS:

   1)  A Name Service Providing Storage Resource Discovery

   2)  Discovery Domain (DD) and Login Control Service

   3)  State Change Notification Service

   4)  Open Mapping of Fibre Channel and iSCSI Devices

2.2.1.  Name Registration Service

   The iSNS provides a registration function to allow all entities in a
   storage network to register and query the iSNS database.  Both
   targets and initiators can register in the iSNS database, as well as
   query for information about other initiators and targets.  This
   allows, for example, a client initiator to obtain information about
   target devices from the iSNS server.  This service is modeled on the
   Fibre Channel Generic Services Name Server described in FC-GS-4, with
   extensions, operating within the context of an IP network.

   The naming registration service also provides the ability to obtain a
   network-unique Domain ID for iFCP gateways when one is required.

2.2.2.  Discovery Domain and Login Control Service

   The Discovery Domain (DD) Service facilitates the partitioning of
   Storage Nodes into more manageable groupings for administrative and
   login control purposes.  It allows the administrator to limit the
   login process of each host to the more appropriate subset of targets
   registered in the iSNS.  This is particularly important for reducing
   the number of unnecessary logins (iSCSI logins or Fibre Channel Port
   Logins), and for limiting the amount of time that the host spends
   initializing login relationships as the size of the storage network
   scales up.  Storage Nodes must be in at least one common enabled DD
   in order to obtain information about each other.  Devices can be
   members of multiple DDs simultaneously.

   Login Control allows targets to delegate their access
   control/authorization policies to the iSNS server.  This is
   consistent with the goal of centralizing management of those storage
   devices using the iSNS server.  The target node or device downloads
   the list of authorized initiators from the iSNS.  Each node or device
   is uniquely identified by an iSCSI Name or FC Port Name.  Only

   initiators that match the required identification and authorization
   provided by the iSNS will be allowed access by that target Node
   during session establishment.

   Placing Portals of a Network Entity into Discovery Domains allows
   administrators to indicate the preferred IP Portal interface through
   which storage traffic should access specific Storage Nodes of that
   Network Entity.  If no Portals of a Network Entity have been placed
   into a DD, then queries scoped to that DD SHALL report all Portals of
   that Network Entity.  If one or more Portals of a Network Entity have
   been placed into a DD, then queries scoped to that DD SHALL report
   only those Portals that have been explicitly placed in the DD.

   DDs can be managed offline through a separate management workstation
   using the iSNSP or SNMP.  If the target opts to use the Login Control
   feature of the iSNS, the target delegates management of access
   control policy (i.e., the list of initiators allowed to log in to
   that target) to the management workstations that are managing the
   configuration in the iSNS database.

   If administratively authorized, a target can upload its own Login
   Control list.  This is accomplished using the DDReg message and
   listing the iSCSI name of each initiator to be registered in the
   target's DD.

   An implementation MAY decide that newly registered devices that have
   not explicitly been placed into a DD by the management station will
   be placed into a "default DD" contained in a "default DDS" whose
   initial DD Set Status value is "enabled".  This makes them visible to
   other devices in the default DD.  Other implementations MAY decide
   that they are registered with no DD, making them inaccessible to
   source-scoped iSNSP messages.

   The iSNS server uses the Source Attribute of each iSNSP message to
   determine the originator of the request and to scope the operation to
   a set of Discovery Domains.  In addition, the Node Type (specified in
   the iFCP or iSCSI Node Type bitmap field) may also be used to
   determine authorization for the specified iSNS operation.  For
   example, only Control Nodes are authorized to create or delete
   discovery domains.

   Valid and active Discovery Domains (DDs) belong to at least one
   active Discovery Domain Set (DDS).  Discovery Domains that do not
   belong to an activated DDS are not enabled.  The iSNS server MUST
   maintain the state of DD membership for all Storage Nodes, even for
   those that have been deregistered.  DD membership is persistent
   regardless of whether a Storage Node is actively registered in the
   iSNS database.

2.2.3.  State Change Notification Service

   The State Change Notification (SCN) service allows the iSNS Server to
   issue notifications about network events that affect the operational
   state of Storage Nodes.  The iSNS client may register for
   notifications on behalf of its Storage Nodes for notification of
   events detected by the iSNS Server.  SCNs notify iSNS clients of
   explicit or implicit changes to the iSNS database; they do not
   necessarily indicate the state of connectivity to peer storage
   devices in the network.  The response of a storage device to receipt
   of an SCN is implementation-specific; the policy for responding to
   SCNs is outside of the scope of this document.

   There are two types of SCN registrations: regular registrations and
   management registrations.  Management registrations result in
   management SCNs, whereas regular registrations result in regular
   SCNs.  The type of registration and SCN message is indicated in the
   SCN bitmap (see Sections 6.4.4 and 6.6.12).

   A regular SCN registration indicates that the Discovery Domain
   Service SHALL be used to control the distribution of SCN messages.
   Receipt of regular SCNs is limited to the discovery domains in which
   the SCN-triggering event takes place.  Regular SCNs do not contain
   information about discovery domains.

   A management SCN registration can only by requested by Control Nodes.
   Management SCNs resulting from management registrations are not bound
   by the Discovery Domain service.  Authorization to request management
   SCN registrations may be administratively controlled.

   The iSNS server SHOULD be implemented with hardware and software
   resources sufficient to support the expected number of iSNS clients.
   However, if resources are unexpectedly exhausted, then the iSNS
   server MAY refuse SCN service by returning an SCN Registration
   Rejected (Status Code 17).  The rejection might occur in situations
   where the network size or current number of SCN registrations has
   passed an implementation-specific threshold.  A client not allowed to
   register for SCNs may decide to monitor its sessions with other
   storage devices directly.

   The specific notification mechanism by which the iSNS server learns
   of the events that trigger SCNs is implementation-specific, but can
   include examples such as explicit notification messages from an iSNS
   client to the iSNS server, or a hardware interrupt to a switch-hosted
   iSNS server as a result of link failure.

2.2.4.  Open Mapping between Fibre Channel and iSCSI Devices

   The iSNS database stores naming and discovery information about both
   Fibre Channel and iSCSI devices.  This allows the iSNS server to
   store mappings of a Fibre Channel device to a proxy iSCSI device
   "image" in the IP network.  Similarly, mappings of an iSCSI device to
   a "proxy WWN" can be stored under the WWNN Token field for that iSCSI
   device.

   Furthermore, through use of iSCSI-FC gateways, Fibre Channel-aware
   management stations can interact with the iSNS server to retrieve
   information about Fibre Channel devices, and use this information to
   manage Fibre Channel and iSCSI devices.  This allows management
   functions such as Discovery Domains and State Change Notifications to
   be applied seamlessly to both iSCSI and Fibre Channel devices,
   facilitating integration of IP networks with Fibre Channel devices
   and fabrics.

   Note that Fibre Channel attributes are stored as iFCP attributes, and
   that the ability to store this information in the iSNS server is
   useful even if the iFCP protocol is not implemented.  In particular,
   tag 101 can be used to store a "Proxy iSCSI Name" for Fibre Channel
   devices registered in the iSNS server.  This field is used to
   associate the FC device with an iSCSI registration entry that is used
   for the Fibre Channel device to communicate with iSCSI devices in the
   IP network.  Conversely, tag 37 (see Section 6.1) contains a WWNN
   Token field, which can be used to store an FC Node Name (WWNN) value
   used by iSCSI-FC gateways to represent an iSCSI device in the Fibre
   Channel domain.

   By storing the mapping between Fibre Channel and iSCSI devices in the
   iSNS server, this information becomes open to any authorized iSNS
   client wishing to retrieve and use this information.  In many cases,
   this provides advantages over storing the information internally
   within an iSCSI-FC gateway, where the mapping is inaccessible to
   other devices except by proprietary mechanisms.

2.3.  iSNS Usage Model

   The following is a high-level description of how each type of device
   in a storage network can utilize iSNS.  Each type of device interacts
   with the iSNS server as an iSNS client and must register itself in
   the iSNS database in order to access services provided by the iSNS.

2.3.1.  iSCSI Initiator

   An iSCSI initiator will query the iSNS server to discover the
   presence and location of iSCSI target devices.  It may also request
   state change notifications (SCNs) so that it can be notified of new
   targets that appear on the network after the initial bootup and
   discovery.  SCNs can also inform the iSCSI initiator of targets that
   have been removed from or no longer available in the storage network,
   so that incomplete storage sessions can be gracefully terminated and
   resources for non-existent targets can be reallocated.

2.3.2.  iSCSI Target

   An iSCSI target allows itself to be discovered by iSCSI initiators by
   registering its presence in the iSNS server.  It may also register
   for SCNs in order to detect the addition or removal of initiators for
   resource allocation purposes.  The iSCSI target device may also
   register for Entity Status Inquiry (ESI) messages, which allow the
   iSNS to monitor the target device's availability in the storage
   network.

2.3.3.  iSCSI-FC Gateway

   An iSCSI-FC gateway bridges devices in a Fibre Channel network to an
   iSCSI/IP network.  It may use the iSNS server to store FC device
   attributes discovered in the FC name server, as well as mappings of
   FC device identifiers to iSCSI device identifiers.  iSNS has the
   capability to store all attributes of both iSCSI and Fibre Channel
   devices; iSCSI devices are managed through direct interaction using
   iSNS, while FC devices can be indirectly managed through iSNS
   interactions with the iSCSI-FC gateway.  This allows both iSCSI and
   Fibre Channel devices to be managed in a seamless management
   framework.

2.3.4.  iFCP Gateway

   An iFCP gateway uses iSNS to emulate the services provided by a Fibre
   Channel name server for FC devices in its gateway region.  iSNS
   provides basic discovery and zoning configuration information to be
   enforced by the iFCP gateway.  When queried, iSNS returns information
   on the N_Port network address used to establish iFCP sessions between
   FC devices supported by iFCP gateways.

2.3.5.  Management Station

   A management station uses iSNS to monitor storage devices and to
   enable or disable storage sessions by configuring discovery domains.
   A management station usually interacts with the iSNS server as a

   Control Node endowed with access to all iSNS database records and
   with special privileges to configure discovery domains.  Through
   manipulation of discovery domains, the management station controls
   the scope of device discovery for iSNS clients querying the iSNS
   server.

2.4.  Administratively Controlled iSNS Settings

   Some important operational settings for the iSNS server are
   configured using administrative means, such as a configuration file,
   a console port, an SNMP, or another implementation-specific method.
   These administratively-controlled settings cannot be configured using
   the iSNS Protocol, and therefore the iSNS server implementation MUST
   provide for such an administrative control interface.

   The following is a list of parameters that are administratively
   controlled for the iSNS server.  In the absence of alternative
   settings provided by the administrator, the following specified
   default settings MUST be used.

   Setting                                  Default Setting
   -------                                  ---------------
   ESI Non-Response Threshold                     3     (see 5.6.5.13)
   Management SCNs (Control Nodes only)        enabled  (see 5.6.5.8)
   Default DD/DDS                              disabled
   DD/DDS Modification
      - Control Node                           enabled
      - iSCSI Target Node Type                 disabled
      - iSCSI Initiator Node Type              disabled
      - iFCP Target Port Role                  disabled
      - iFCP Initiator Port Role               disabled
   Authorized Control Nodes                      N/A

   ESI Non-Response Threshold: determines the number of ESI messages
                   sent without receiving a response before the network
                   entity is deregistered from the iSNS database.

   Management SCN for Control Node: determines whether a registered
                   Control Node is permitted to register to receive
                   Management SCNs.

   Default DD/DDS: determines whether a newly registered device not
                   explicitly placed into a discovery domain (DD) and
                   discovery domain set (DDS) is placed into a default
                   DD/DDS.

   DD/DDS Modification: determines whether the specified type of Node is
                   allowed to add, delete or update DDs and DDSs.

   Authorized Control Nodes: a list of Nodes identified by iSCSI Name or
                   FC Port Name WWPN that are authorized to register as
                   Control Nodes.

2.5.  iSNS Server Discovery

2.5.1.  Service Location Protocol (SLP)

   The Service Location Protocol (SLP) provides a flexible and scalable
   framework for providing hosts with access to information about the
   existence, location, and configuration of networked services,
   including the iSNS server.  SLP can be used by iSNS clients to
   discover the IP address or FQDN of the iSNS server.  To implement
   discovery through SLP, a Service Agent (SA) should be cohosted in the
   iSNS server, and a User Agent (UA) should be in each iSNS client.
   Each client multicasts a discovery message requesting the IP address
   of the iSNS server(s).  The SA responds to this request.  Optionally,
   the location of the iSNS server can be stored in the SLP Directory
   Agent (DA).

   Note that a complete description and specification of SLP can be
   found in [RFC2608], and is beyond the scope of this document.  A
   service template for using SLP to locate iSNS servers can be found in
   [iSCSI-SLP].

2.5.2.  Dynamic Host Configuration Protocol (DHCP)

   The IP address of the iSNS server can be stored in a DHCP server to
   be downloaded by iSNS clients using a DHCP option.  The DHCP option
   number to be used for distributing the iSNS server location is found
   in [iSNSOption].

2.5.3.  iSNS Heartbeat Message

   The iSNS heartbeat message is described in Section 5.6.5.14.  It
   allows iSNS clients within the broadcast or multicast domain of the
   iSNS server to discover the location of the active iSNS server and
   any backup servers.

2.6.  iSNS and Network Address Translation (NAT)

   The existence of NAT will have an impact upon information retrieved
   from the iSNS server.  If the iSNS client exists in an addressing
   domain different from that of the iSNS server, then IP address
   information stored in the iSNS server may not be correct when
   interpreted in the domain of the iSNS client.

   There are several possible approaches to allow operation of iSNS
   within a NAT network.  The first approach is to require use of the
   canonical TCP port number by both targets and initiators when
   addressing targets across a NAT boundary, and for the iSNS client not
   to query for nominal IP addresses.  Rather, the iSNS client queries
   for the DNS Fully Qualified Domain Name stored in the Entity
   Identifier field when seeking addressing information.  Once
   retrieved, the DNS name can be interpreted in each address domain and
   mapped to the appropriate IP address by local DNS servers.

   A second approach is to deploy a distributed network of iSNS servers.
   Local iSNS servers are deployed inside and outside NAT boundaries,
   with each local server storing relevant IP addresses for their
   respective NAT domains.  Updates among the network of decentralized,
   local iSNS servers are handled using LDAP and appropriate NAT
   translation rules implemented within the update mechanism in each
   server.

   Finally, note that it is possible for an iSNS server in the private
   addressing domain behind a NAT boundary to exclusively support iSNS
   clients that are operating in the global IP addressing domain.  If
   this is the case, the administrator only needs to ensure that the
   appropriate mappings are configured on the NAT gateways to allow the
   iSNS clients to initiate iSNSP sessions to the iSNS server.  All
   registered addresses contained in the iSNS server are thus public IP
   addresses for use outside the NAT boundary.  Care should be taken to
   ensure that there are no iSNS clients querying the server from inside
   the NAT boundary.

2.7.  Transfer of iSNS Database Records between iSNS Servers

   Transfer of iSNS database records between iSNS servers has important
   applications, including the following:

   1)  An independent organization needs to transfer storage information
       to a different organization.  Each organization independently
       maintains its own iSNS infrastructure.  To facilitate discovery
       of storage assets of the peer organization using IP, iSNS
       database records can be transferred between authoritative iSNS
       servers from each organization.  This allows storage sessions to
       be established directly between devices residing in each
       organization's storage network infrastructure over a common IP
       network.

   2)  Multiple iSNS servers are desired for redundancy.  Backup servers
       need to maintain copies of the primary server's dynamically
       changing database.

   To support the above applications, information in an iSNS server can
   be distributed to other iSNS servers either using the iSNS protocol,
   or through out-of-band mechanisms using non-iSNS protocols.  The
   following examples illustrate possible methods for transferring data
   records between iSNS servers.  In the first example, a back-end LDAP
   information base is used to support the iSNS server, and the data is
   transferred using the LDAP protocol.  Once the record transfer of the
   remote device is completed, it becomes visible and accessible to
   local devices using the local iSNS server.  This allows local devices
   to establish sessions with remote devices (provided that firewall
   boundaries can be negotiated).

   +-------------------------+           +-------------------------+
   |+------+ iSNSP           |           |           iSNSP +-----+ |
   ||dev A |<----->+------+  |           |  +------+<----->|dev C| |
   |+------+       |      |  |           |  |      |       +-----+ |
   |+------+ iSNSP |local |  |           |  |remote| iSNSP +-----+ |
   ||dev B |<----->| iSNS |  |           |  | iSNS |<----->|dev D| |
   |+------+       |server|  |           |  |server|       +-----+ |
   |........       +--+---+  |   WAN     |  +---+--+               |
   |.dev C'.          |      |   Link    |      |                  |
   |........          |      =============      |                  |
   |                  |      |           |      |                  |
   |               +--+---+  |           |  +---+--+               |
   |               | local|<--- <--- <--- <-|remote|               |
   |               | LDAP |  |  LDAP:    |  | LDAP |               |
   |               +------+  Xfer "dev C"|  +------+               |
   +-------------------------+           +-------------------------+
          Enterprise                           Enterprise
          Network A                            Network B

   In the above diagram, two business partners wish to share storage
   "dev C".  Using LDAP, the record for "dev C" can be transferred from
   Network B to Network A.  Once accessible to the local iSNS server in
   Network A, local devices A and B can now discover and connect to "dev
   C".

   +-------------------------+           +-------------------------+
   |+------+ iSNSP           |           |           iSNSP +-----+ |
   ||dev A |<----->+------+  |           |  +------+<----->|dev C| |
   |+------+       |      |  |           |  |      |       +-----+ |
   |+------+ iSNSP |local |  |           |  |remote| iSNSP +-----+ |
   ||dev B |<----->| iSNS |  |           |  | iSNS |<----->|dev D| |
   |+------+       |server|  |           |  |server|       +-----+ |
   |........       +------+  |   WAN     |  +---+--+               |
   |.dev C'.          ^      |   Link    |      |                  |
   |........          |      =============      v                  |
   |                  |      |           |      |SNMP              |
   |                  |      |           |      |                  |
   |               +--+----+ |           |      v                  |
   |               | SNMP  |<--- <--- <--- <----                   |
   |               | Mgmt  | |  SNMP: Xfer "dev C"                 |
   |               |Station| |           |                         |
   |               +-------+ |           |                         |
   +-------------------------+           +-------------------------+
          Enterprise                           Enterprise
          Network A                            Network B

   The above diagram illustrates a second example of how iSNS records
   can be shared.  This method uses an SNMP-based management station to
   retrieve (GET) the desired record for "dev C" manually, and then to
   store (SET) it on the local iSNS server directly.  Once the record is
   transferred to the local iSNS server in Network A, "dev C" becomes
   visible and accessible (provided that firewall boundaries can be
   negotiated) to other devices in Network A.

   Other methods, including proprietary protocols, can be used to
   transfer device records between iSNS servers.  Further discussion and
   explanation of these methodologies is beyond the scope of this
   document.

2.8.  Backup iSNS Servers

   This section offers a broad framework for implementation and
   deployment of iSNS backup servers.  Server failover and recovery are
   topics of continuing research, and adequate resolution of issues such
   as split brain and primary server selection is dependent on the
   specific implementation requirements and deployment needs.  The
   failover mechanisms discussed in this document focus on the
   interaction between iSNS clients and iSNS servers.  Specifically,
   what is covered in this document includes the following:

   -  iSNS client behavior and the iSNS protocol interaction between the
      client and multiple iSNS servers, some of which are backup
      servers.

   -  Required failover behaviors of the collection of iSNS servers that
      includes active and backup servers.

   However, note that this document does not specify the complete
   functional failover requirements of each iSNS server.  In particular,
   it does not specify the complete set of protocol interactions among
   the iSNS servers that are required to achieve stable failover
   operation in an interoperable manner.

   For the purposes of this discussion, the specified backup mechanisms
   pertain to interaction among different logical iSNS servers.  Note
   that it is possible to create multiple physical iSNS servers to form
   a single logical iSNS server cluster, and thus to distribute iSNS
   transaction processing among multiple physical servers.  However, a
   more detailed discussion of the interactions between physical servers
   within a logical iSNS server cluster is beyond the scope of this
   document.

   Multiple logical iSNS servers can be used to provide redundancy in
   the event that the active iSNS server fails or is removed from the
   network.  The methods described in Section 2.7 above can be used to
   transfer name server records to backup iSNS servers.  Each backup
   server maintains a redundant copy of the name server database found
   in the primary iSNS server, and can respond to iSNS protocol messages
   in the same way as the active server.  Each backup server SHOULD
   monitor the health and status of the active iSNS server, including
   checking to make sure its own database is synchronized with the
   active server's database.  How each backup server accomplishes this
   is implementation-dependent, and may (or may not) include using the
   iSNS protocol.  If the iSNS protocol is used, then the backup server
   MAY register itself in the active server's iSNS database as a Control
   Node, allowing it to receive state-change notifications.

   Generally, the administrator or some automated election process is
   responsible for initial and subsequent designation of the primary
   server and each backup server.

   A maximum of one logical backup iSNS server SHALL exist at any
   individual IP address, in order to avoid conflicts from multiple
   servers listening on the same canonical iSNS TCP or UDP port number.

   The iSNS heartbeat can also be used to coordinate the designation and
   selection of primary and backup iSNS servers.

   Each backup server MUST note its relative precedence in the active
   server's list of backup servers.  If its precedence is not already
   known, each backup server MAY learn it from the iSNS heartbeat
   message, by noting the position of its IP address in the ordered list

   of backup server IP addresses.  For example, if it is the first
   backup listed in the heartbeat message, then its backup precedence is
   1.  If it is the third backup server listed, then its backup
   precedence is 3.

   If a backup server establishes that it has lost connectivity to the
   active server and other backup servers of higher precedence, then it
   SHOULD assume that it is the active server.  The method of
   determining whether connectivity has been lost is implementation-
   specific.  One possible approach is to assume that if the backup
   server does not receive iSNS heartbeat messages for a period of time,
   then connectivity to the active server has been lost.  Alternatively,
   the backup server may establish TCP connections to the active server
   and other backup servers, with loss of connectivity determined
   through non-response to periodic echo or polling messages (using
   iSNSP, SNMP, or other protocols).

   When a backup server becomes the active server, it SHALL assume all
   active server responsibilities, including (if used) transmission of
   the iSNS heartbeat message.  If transmitting the iSNS heartbeat, the
   backup server replaces the active Server IP Address and TCP/UDP Port
   entries with its own IP address and TCP/UDP Port, and begins
   incrementing the counter field from the last known value from the
   previously-active iSNS server.  However, it MUST NOT change the
   original ordered list of backup server IP Address and TCP/UDP Port
   entries.  If the primary backup server or other higher-precedence
   backup server returns, then the existing active server is responsible
   for ensuring that the new active server's database is up-to-date
   before demoting itself to its original status as backup.

   Since the primary and backup iSNS servers maintain a coordinated
   database, no re-registration by an iSNS Client is required when a
   backup server takes the active server role.  Likewise, no re-
   registration by an iSNS Client is required when the previous primary
   server returns to the active server role.

2.9.  Transport Protocols

   The iSNS Protocol is transport-neutral.  Query and registration
   messages are transported over TCP or UDP.  iSNS heartbeat messages
   are transported using IP multicast or broadcast.

2.9.1.  Use of TCP for iSNS Communication

   It MUST be possible to use TCP for iSNS communication.  The iSNS
   server MUST accept TCP connections for client registrations.  To
   receive Entity Status Inquiry (ESI) (see Section 5.6.5.13) monitoring
   the use of TCP, the client registers the Portal ESI Interval and the

   port number of the TCP port that will be used to receive ESI
   messages.  The iSNS server initiates the TCP connection used to
   deliver the ESI message.  This TCP connection does not need to be
   continuously open.

   To receive SCN notifications using TCP, the client registers the
   iSCSI or iFCP SCN Bitmap and the port number of the TCP port in the
   Portal used to receive SCNs.  The iSNS server initiates the TCP
   connection used to deliver the SCN message.  This TCP connection does
   not need to be continuously open.

   It is possible for an iSNS client to use the same TCP connection for
   SCN, ESI, and iSNS queries.  Alternatively, separate connections may
   be used.

2.9.2.  Use of UDP for iSNS Communication

   The iSNS server MAY accept UDP messages for client registrations.
   The iSNS server MUST accept registrations from clients requesting
   UDP-based ESI and SCN messages.

   To receive UDP-based ESI monitoring messages, the client registers
   the port number of the UDP port in at least one Portal to be used to
   receive and respond to ESI messages from the iSNS server.  If a
   Network Entity has multiple Portals with registered ESI UDP Ports,
   then ESI messages SHALL be delivered to every Portal registered to
   receive such messages.

   To receive UDP-based SCN notification messages, the client registers
   the port number of the UDP port in at least one Portal to be used to
   receive SCN messages from the iSNS server.  If a Network Entity has
   multiple Portals with registered SCN UDP Ports, then SCN messages
   SHALL be delivered to each Portal registered to receive such
   messages.

   When using UDP to transport iSNS messages, each UDP datagram MUST
   contain exactly one iSNS PDU (see Section 5).

2.9.3.  iSNS Multicast and Broadcast Messages

   iSNS multicast messages are transported using IP multicast or
   broadcast.  The iSNS heartbeat is the only iSNS multicast or
   broadcast message.  This message is originated by the iSNS server and
   sent to all iSNS clients that are listening on the IP multicast
   address allocated for the iSNS heartbeat.

2.10.  Simple Network Management Protocol (SNMP) Requirements

   The iSNS Server may be managed via the iSNS MIB [iSNSMIB] using an
   SNMP management framework [RFC3411].  For a detailed overview of the
   documents that describe the current Internet-Standard Management
   Framework, please refer to Section 7 of RFC 3410 [RFC3410].  The iSNS
   MIB provides the ability to configure and monitor an iSNS server
   without using the iSNS protocol directly.  SNMP management frameworks
   have several requirements for object indexing in order for objects to
   be accessed or added.

   SNMP uses an Object Identifier (OID) for object identification.  The
   size of each OID is restricted to a maximum of 128 sub-identifiers.
   Both the iSCSI and iFCP protocol contain identifiers, such as the
   iSCSI Name, that are greater the 128 characters in length.  Using
   such identifiers as an index would result in more than 128 sub-
   identifiers per OID.  In order to support objects that have key
   identifiers whose maximum length is longer than the maximum SNMP-
   supported length, the iSNS server provides secondary non-zero integer
   index identifiers.  These indexes SHALL be persistent for as long as
   the server is active.  Furthermore, index values for recently
   deregistered objects SHOULD NOT be reused in the short term.  Object
   attributes, including indexes, are described in detail in Section 6.

   For SNMP based management applications to create a new entry in a
   table of objects, a valid OID must be available to specify the table
   row.  The iSNS server supports this by providing, for each type of
   object that can be added via SNMP, an object attribute that returns
   the next available non-zero integer index.  This allows an SNMP
   client to request an OID to be used for registering a new object in
   the server.  Object attributes, including next available index
   attributes, are described in detail in Section 6.

3.  iSNS Object Model

   iSNS provides the framework for the registration, discovery, and
   management of iSCSI devices and Fibre Channel-based devices (using
   iFCP).  This architecture framework provides elements needed to
   describe various storage device objects and attributes that may exist
   on an IP storage network.  Objects defined in this architecture
   framework include Network Entity, Portal, Storage Node, FC Device,
   Discovery Domain, and Discovery Domain Set.  Each of these objects is
   described in greater detail in the following sections.

3.1.  Network Entity Object

   The Network Entity object is a container of Storage Node objects and
   Portal objects.  It represents the infrastructure supporting access
   to a unique set of one or more Storage Nodes.  The Entity Identifier
   attribute uniquely distinguishes a Network Entity, and is the key
   used to register a Network Entity object in an iSNS server.  All
   Storage Nodes and Portals contained within a single Network Entity
   object operate as a cohesive unit.

   Note that it is possible for a single physical device or gateway to
   be represented by more than one logical Network Entity in the iSNS
   database.  For example, one of the Storage Nodes on a physical device
   may be accessible from only a subset of the network interfaces (i.e.,
   Portals) available on that device.  In this case, a logical network
   entity (i.e., a "shadow entity") is created and used to contain the
   Portals and Storage Nodes that can operate cooperatively.  No object
   (Portals, Storage Nodes, etc.) can be contained in more than one
   logical Network Entity.

   Similarly, it is possible for a logical Network Entity to be
   supported by more than one physical device or gateway.  For example,
   multiple FC-iSCSI gateways may be used to bridge FC devices in a
   single Fibre Channel network.  Collectively, the multiple gateways
   can be used to support a single logical Network Entity that is used
   to contain all the devices in that Fibre Channel network.

3.2.  Portal Object

   The Portal object is an interface through which access to Storage
   Nodes within the Network Entity can be obtained.  The IP address and
   TCP/UDP Port number attributes uniquely distinguish a Portal object,
   and combined are the key used to register a Portal object in an iSNS
   server.  A Portal is contained in one and only one Network Entity,
   and may be contained in one or more DDs (see Section 3.6).

3.3.  Storage Node Object

   The Storage Node object is the logical endpoint of an iSCSI or iFCP
   session.  In iFCP, the session endpoint is represented by the World
   Wide Port Name (WWPN).  In iSCSI, the session endpoint is represented
   by the iSCSI Name of the device.  For iSCSI, the iSCSI Name attribute
   uniquely distinguishes a Storage Node, and is the key used to
   register a Storage Node object in an iSNS Server.  For iFCP, the FC
   Port Name (WWPN) attribute uniquely distinguishes a Storage Node, and
   is the key used to register a Storage Node object in the iSNS Server.
   Storage Node is contained in only one Network Entity object and may
   be contained in one or more DDs (see Section 3.6).

3.4.  Portal Group Object

   The Portal Group (PG) object represents an association between a
   Portal and an iSCSI Node.  Each Portal and iSCSI Storage Node
   registered in an Entity can be associated using a Portal Group (PG)
   object.  The PG Tag (PGT), if non-NULL, indicates that the associated
   Portal provides access to the associated iSCSI Storage Node in the
   Entity.  All Portals that have the same PGT value for a specific
   iSCSI Storage Node allow coordinated access to that node.

   A PG object MAY be registered when a Portal or iSCSI Storage Node is
   registered.  Each Portal to iSCSI Node association is represented by
   one and only one PG object.  In order for a Portal to provide access
   to an iSCSI Node, the PGT of the PG object MUST be non-NULL.  If the
   PGT value registered for a specified Portal and iSCSI Node is NULL,
   or if no PGT value is registered, then the Portal does not provide
   access to that iSCSI Node in the Entity.

   The PGT value indicates whether access to an iSCSI Node can be
   coordinated across multiple Portals.  All Portals that have the same
   PGT value for a specific iSCSI Node can provide coordinated access to
   that iSCSI Node.  According to the iSCSI Specification, coordinated
   access to an iSCSI node indicates the capability of coordinating an
   iSCSI session with connections that span these Portals [iSCSI].

   The PG object is uniquely distinguished by the iSCSI Name, Portal IP
   Address, and Portal TCP Port values of the associated Storage Node
   and Portal objects.  These are represented in the iSNS Server by the
   PG iSCSI Name, PG Portal IP Address, and PG Portal TCP/UDP Port
   attributes, respectively.  The PG object is also uniquely
   distinguished in the iSNS Server by the PG Index value.

   A new PG object can only be registered by referencing its associated
   iSCSI Storage Node or Portal object.  A pre-existing PG object can be
   modified or queried by using its Portal Group Index as message key,
   or by referencing its associated iSCSI Storage Node or Portal object.
   A 0-length Tag, Length, Value TLV is used to register a PGT NULL
   value.

   The PG object is deregistered if and only if its associated iSCSI
   Node and Portal objects are both removed.

3.5.  Device Object

   The FC Device represents the Fibre Channel Node.  This object
   contains information that may be useful in the management of the
   Fibre Channel device.  The FC Node Name (WWNN) attribute uniquely
   distinguishes an FC Device, and is the key used to register an FC
   Device object in the iSNS Server.

   The FC Device is contained in one or more Storage Node objects.

3.6.  Discovery Domain Object

   Discovery Domains (DD) are a security and management mechanism used
   to administer access and connectivity to storage devices.  For query
   and registration purposes, they are considered containers for Storage
   Node and Portal objects.  A query by an iSNS client that is not from
   a Control Node only returns information about objects with which it
   shares at least one active DD.  The only exception to this rule is
   with Portals; if Storage Nodes of a Network Entity are registered in
   the DD without Portals, then all Portals of that Network Entity are
   implicit members of that DD.  The Discovery Domain ID (DD_ID)
   attribute uniquely distinguishes a Discovery Domain object, and is
   the key used to register a Discovery Domain object in the iSNS
   Server.

   A DD is considered active if it is a member of at least one active DD
   Set.  DDs that are not members of at least one enabled DDS are
   considered disabled.  A Storage Node can be a member of one or more
   DDs.  An enabled DD establishes connectivity among the Storage Nodes
   in that DD.

3.7.  Discovery Domain Set Object

   The Discovery Domain Set (DDS) is a container object for Discovery
   Domains (DDs).  DDSs may contain one or more DDs.  Similarly, each DD
   can be a member of one or more DDSs.  DDSs are a mechanism to store
   coordinated sets of DD mappings in the iSNS server.  Active DDs are
   members of at least one active DD Set.  Multiple DDSs may be
   considered active at the same time.  The Discovery Domain Set ID
   (DDS_ID) attribute uniquely distinguishes a Discovery Domain Set
   object, and is the key used to register a Discovery Domain Set object
   in the iSNS Server.

3.8.  Database Model

   As presented to the iSNS client, each object of a specific type in
   the iSNS database MUST have an implicit internal linear ordering
   based on the key(s) for that object type.  This ordering provides the

   ability to respond to DevGetNext queries (see Section 5.6.5.3).  The
   ordering of objects in the iSNS database SHOULD NOT be changed with
   respect to that implied ordering, as a consequence of object
   insertions and deletions.  That is, the relative order of surviving
   object entries in the iSNS database SHOULD be preserved so that the
   DevGetNext message encounters generally reasonable behavior.

   The following diagram shows the various objects described above and
   their relationship to each other.

                    +--------------+    +-----------+
                    |    NETWORK   |1  *|           |
                    |    ENTITY    |----|  PORTAL   |
                    |              |    |           |
                    +--------------+    +-----------+
                            |1            |1  |*
                            |             |   |
                            |             |*  |
                            |   +----------+  |
                            |   |  PORTAL  |  |
                            |   |  GROUP   |  |
                            |   +----------+  |
                            |    |*           |
                            |    |            |
                            |*   |1           |*
   +-----------+    +--------------+    +-----------+    +-----------+
   |    FC     |1  *|   STORAGE    |*  *| DISCOVERY |*  *| DISCOVERY |
   |  DEVICE   |----|    NODE      |----|  DOMAIN   |----|  DOMAIN   |
   |           |    |              |    |           |    |    SET    |
   +-----------+    +--------------+    +-----------+    +-----------+

                * represents 0 to many possible relationships

4.  iSNS Implementation Requirements

   This section details specific requirements for support of each of
   these IP storage protocols.  Implementation requirements for security
   are described in Section 7.

4.1.  iSCSI Requirements

   Use of iSNS in support of iSCSI is OPTIONAL.  iSCSI devices MAY be
   manually configured with the iSCSI Name and IP address of peer
   devices, without the aid or intervention of iSNS.  iSCSI devices may
   also use SLP [RFC2608] to discover peer iSCSI devices.  However, iSNS
   is useful for scaling a storage network to a larger number of iSCSI
   devices.

4.1.1.  Required Attributes for Support of iSCSI

   The following attributes are available to support iSCSI.  Attributes
   indicated in the REQUIRED for Server column MUST be implemented by an
   iSNS server used to support iSCSI.  Attributes indicated in the
   REQUIRED for Client column MUST be implemented by an iSCSI device
   that elects to use the iSNS.  Attributes indicated in the K (Key)
   column uniquely identify the object type in the iSNS Server.  A more
   detailed description of each attribute is found in Section 6.

                                                        REQUIRED for:
   Object             Attribute                    K    Server  Client
   ------             ---------                    -    ------  ------
   NETWORK ENTITY     Entity Identifier            *      *        *
                      Entity Protocol                     *        *
                      Management IP Address               *
                      Timestamp                           *
                      Protocol Version Range              *
                      Registration Period                 *
                      Entity Index                        *
                      Entity IKE Phase-1 Proposal
                      Entity Certificate

   PORTAL             IP Address                   *      *        *
                      TCP/UDP Port                 *      *        *
                      Portal Symbolic Name                *
                      ESI Interval                        *
                      ESI Port                            *
                      Portal Index                        *
                      SCN Port                            *
                      Portal Security Bitmap              *
                      Portal IKE Phase-1 Proposal
                      Portal IKE Phase-2 Proposal
                      Portal Certificate

   PORTAL GROUP       PG iSCSI Name                *      *        *
                      PG IP Address                *      *        *
                      PG TCP/UDP Port              *      *        *
                      PG Tag                              *        *
                      PG Index                            *

   STORAGE NODE       iSCSI Name                   *      *        *
                      iSCSI Node Type                     *        *
                      Alias                               *
                      iSCSI SCN Bitmap                    *
                      iSCSI Node Index                    *
                      WWNN Token
                      iSCSI AuthMethod
                      iSCSI Node Certificate

   DISCOVERY DOMAIN   DD ID                        *      *        *
                      DD Symbolic Name                    *
                      DD Member iSCSI Node Index          *
                      DD Member iSCSI Name                *
                      DD Member Portal Index              *
                      DD Member Portal IP Addr            *
                      DD Member Portal TCP/UDP            *
                      DD Features                         *

   DISCOVERY DOMAIN   DDS Identifier                *     *
   SET                DDS Symbolic Name                   *
                      DDS Status                          *

   All iSCSI user-specified and vendor-specified attributes are OPTIONAL
   to implement and use.

4.1.2.  Examples: iSCSI Object Model Diagrams

   The following diagram models how a simple iSCSI-based initiator and
   target is represented using database objects stored in the iSNS
   server.  In this implementation, each target and initiator is
   attached to a single Portal.

   +----------------------------------------------------------------+
   |                         IP Network                             |
   +------------+--------------------------------------+------------+
                |                                      |
                |                                      |
   +-----+------+------+-----+            +-----+------+------+-----+
   |     | PORTAL      |     |            |     | PORTAL      |     |
   |     | -IP Addr 1  |     |            |     | -IP Addr 2  |     |
   |     | -TCP Port 1 |     |            |     | -TCP Port 2 |     |
   |     +-----+ +-----+     |            |     +-----+ +-----+     |
   |           | |           |            |           | |           |
   |     +-----+ +-----+     |            |     +-----+ +-----+     |
   |     | PORTAL GROUP|     |            |     | PORTAL GROUP|     |
   |     | -Prtl Tag 1 |     |            |     | -Prtl Tag 2 |     |
   |     +-----+ +-----+     |            |     +-----+ +-----+     |
   |           | |           |            |           | |           |
   |  +--------+ +--------+  |            |   +-------+ +--------+  |
   |  |                   |  |            |   |                  |  |
   |  |  STORAGE NODE     |  |            |   |  STORAGE NODE    |  |
   |  |  -iSCSI Name      |  |            |   |   -iSCSI Name    |  |
   |  |  -Alias: "server1"|  |            |   |   -Alias: "disk1"|  |
   |  |  -Type: initiator |  |            |   |   -Type: target  |  |
   |  |                   |  |            |   |                  |  |
   |  +-------------------+  |            |   +------------------+  |
   |                         |            |                         |
   |    NETWORK ENTITY       |            |    NETWORK ENTITY       |
   |   -Entity ID (FQDN):    |            |   -Entity ID (FQDN):    |
   |    "strg1.example.com"  |            |    "strg2.example.net"  |
   |   -Protocol: iSCSI      |            |   -Protocol: iSCSI      |
   |                         |            |                         |
   +-------------------------+            +-------------------------+

   The object model can be expanded to describe more complex devices,
   such as an iSCSI device with more than one storage controller, in
   which each controller is accessible through any of multiple Portal
   interfaces, possibly using multiple Portal Groups.  The storage
   controllers on this device can be accessed through alternate Portal
   interfaces if any original interface should fail.  The following
   diagram describes such a device:

      +---------------------------------------------------------------+
      |                         IP Network                            |
      +-------------------+-----------------------+-------------------+
                          |                       |
                          |                       |
      +------------+------+------+---------+------+------+------------+
      |            | PORTAL 1    |         | PORTAL 2    |            |
      |            | -IP Addr 1  |         | -IP Addr 2  |            |
      |            | -TCP Port 1 |         | -TCP Port 2 |            |
      |            +-----+ +-----+         +-----+ +-----+            |
      |                  | |                     | |                  |
      |  +---------------+ +---------------------+ +---------------+  |
      |  +-------+ +----------------+ +-------------------+ +------+  |
      |          | |                | |                   | |         |
      |  +-------+ +-------+ +------+ +--------+ +--------+ +------+  |
      |  |                 | |                 | |                 |  |
      |  | STORAGE NODE 1  | | STORAGE NODE 2  | | STORAGE NODE 3  |  |
      |  |  -iSCSI Name 1  | |  -iSCSI Name 2  | |  -iSCSI Name 3  |  |
      |  |  -Alias: "disk1"| |  -Alias: "disk2"| |  -Alias: "disk3"|  |
      |  |  -Type: target  | |  -Type: target  | |  -Type: target  |  |
      |  |                 | |                 | |                 |  |
      |  +-----------------+ +-----------------+ +-----------------+  |
      |                                                               |
      |                         NETWORK ENTITY                        |
      |                    -Entity ID (FQDN): "dev1.example.com"      |
      |                    -Protocol: iSCSI                           |
      |                                                               |
      |                   Portal Group Object Table                   |
      |           Storage-Node Portal Portal-Group-Tag                |
      |                1         1           10                       |
      |                1         2         NULL (no access permitted) |
      |                2         1           20                       |
      |                2         2           20                       |
      |                3         1           30                       |
      |                3         2           10                       |
      |                                                               |
      +---------------------------------------------------------------+

   Storage Node 1 is accessible via Portal 1 with a PGT of 10.  It does
   not have a Portal Group Tag (PGT) assigned for Portal 2, so Storage
   Node 1 cannot be accessed via Portal 2.

   Storage Node 2 can be accessed via both Portal 1 and Portal 2.  Since
   Storage Node 2 has the same PGT value assigned to both Portal 1 and
   Portal 2, in this case 20, coordinated access via the Portals is
   available [iSCSI].

   Storage Node 3 can be accessed via Portal 1 or Portal 2.  However,
   since Storage Node 3 has different PGT values assigned to each
   Portal, in this case 10 and 30, access is not coordinated [iSCSI].
   Because PGTs are assigned within the context of a Storage Node, the
   PGT value of 10 used for Storage Node 1 and Storage Node 3 are not
   interrelated.

4.1.3.  Required Commands and Response Messages for Support of iSCSI

   The following iSNSP messages and responses are available in support
   of iSCSI.  Messages indicated in the REQUIRED for Server column MUST
   be implemented in iSNS servers used for iSCSI devices.  Messages
   indicated in the REQUIRED for Client column MUST be implemented in
   iSCSI devices that elect to use the iSNS server.

                                                     REQUIRED for:
   Message Description       Abbreviation  Func_ID   Server  Client
   -------------------       ------------  -------   ------  ------
   RESERVED                                0x0000
   Device Attr Reg Request   DevAttrReg    0x0001       *       *
   Dev Attr Query Request    DevAttrQry    0x0002       *       *
   Dev Get Next Request      DevGetNext    0x0003       *
   Deregister Dev Request    DevDereg      0x0004       *       *
   SCN Register Request      SCNReg        0x0005       *
   SCN Deregister Request    SCNDereg      0x0006       *
   SCN Event                 SCNEvent      0x0007       *
   State Change Notification SCN           0x0008       *
   DD Register               DDReg         0x0009       *       *
   DD Deregister             DDDereg       0x000A       *       *
   DDS Register              DDSReg        0x000B       *       *
   DDS Deregister            DDSDereg      0x000C       *       *
   Entity Status Inquiry     ESI           0x000D       *
   Name Service Heartbeat    Heartbeat     0x000E
   RESERVED                                0x000F-0x00FF
   Vendor Specific                         0x0100-0x01FF
   RESERVED                                0x0200-0x7FFF

   The following are iSNSP response messages used in support of iSCSI:

                                                      REQUIRED for:
   Response Message Desc     Abbreviation  Func_ID    Server  Client
   ---------------------     ------------  -------    ------  ------
   RESERVED                                0x8000
   Device Attr Register Rsp  DevAttrRegRsp 0x8001       *       *
   Device Attr Query Rsp     DevAttrQryRsp 0x8002       *       *
   Device Get Next Rsp       DevGetNextRsp 0x8003       *
   Device Dereg Rsp          DevDeregRsp   0x8004       *       *
   SCN Register Rsp          SCNRegRsp     0x8005       *

   SCN Deregister Rsp        SCNDeregRsp   0x8006       *
   SCN Event Rsp             SCNEventRsp   0x8007       *
   SCN Response              SCNRsp        0x8008       *
   DD Register Rsp           DDRegRsp      0x8009       *       *
   DD Deregister Rsp         DDDeregRsp    0x800A       *       *
   DDS Register Rsp          DDSRegRsp     0x800B       *       *
   DDS Deregister Rsp        DDSDeregRsp   0x800C       *       *
   Entity Stat Inquiry Rsp   ESIRsp        0x800D       *
   RESERVED                                0x800E-0x80FF
   Vendor Specific                         0x8100-0x81FF
   RESERVED                                0x8200-0xFFFF

4.2.  iFCP Requirements

   In iFCP, use of iSNS is REQUIRED.  No alternatives exist for support
   of iFCP Naming & Discovery functions.

4.2.1.  Required Attributes for Support of iFCP

   The following table displays attributes that are used by iSNS to
   support iFCP.  Attributes indicated in the REQUIRED for Server column
   MUST be implemented by the iSNS server that supports iFCP.
   Attributes indicated in the REQUIRED for Client column MUST be
   supported by iFCP gateways.  Attributes indicated in the K (Key)
   column uniquely identify the object type in the iSNS Server.  A more
   detailed description of each attribute is found in Section 6.

                                                       REQUIRED for:
   Object             Attribute                   K    Server  Client
   ------             ---------                   -    ------  ------
   NETWORK ENTITY     Entity Identifier           *       *       *
                      Entity Protocol                     *       *
                      Management IP Address               *
                      Timestamp                           *
                      Protocol Version Range              *
                      Registration period
                      Entity Index
                      Entity IKE Phase-1 Proposal
                      Entity Certificate

   PORTAL             IP Address                  *       *       *
                      TCP/UDP Port                *       *       *
                      Symbolic Name                       *
                      ESI Interval                        *
                      ESI Port                            *
                      SCN Port                            *
                      Portal IKE Phase-1 Proposal
                      Portal IKE Phase-2 Proposal

                      Portal Certificate
                      Security Bitmap                     *

   STORAGE NODE       FC Port Name (WWPN)         *       *       *
   (FC Port)          Port_ID                             *       *
                      FC Port Type                        *       *
                      Port Symbolic Name                  *
                      Fabric Port Name (FWWN)             *
                      Hard Address                        *
                      Port IP Address                     *
                      Class of Service                    *
                      FC FC-4 Types                       *
                      FC FC-4 Descriptors                 *
                      FC FC-4 Features                    *
                      SCN Bitmap                          *
                      iFCP Port Role                      *
                      Permanent Port Name                 *

   FC DEVICE          FC Node Name (WWNN)         *       *       *
   (FC Node)          Node Symbolic Name                  *
                      Node IP Address                     *
                      Node IPA                            *
                      Proxy iSCSI Name

   DISCOVERY DOMAIN   DD ID                       *       *       *
                      DD Symbolic Name                    *
                      DD Member FC Port Name              *
                      DD Member Portal Index              *
                      DD Member Portal IP Addr            *
                      DD Member Portal TCP/UDP            *

   DISCOVERY DOMAIN   DDS ID                      *       *
   SET                DDS Symbolic Name                   *
                      DDS Status                          *

   OTHER              Switch Name
                      Preferred_ID
                      Assigned_ID
                      Virtual_Fabric_ID

   All iFCP user-specified and vendor-specified attributes are OPTIONAL
   to implement and use.

4.2.2.  Example: iFCP Object Model Diagram

   The iFCP protocol allows native Fibre Channel devices or Fibre
   Channel fabrics connected to an iFCP gateway to be directly
   internetworked using IP.

   When supporting iFCP, the iSNS server stores Fibre Channel device
   attributes, iFCP gateway attributes, and Fibre Channel fabric switch
   attributes that might also be stored in an FC name server.

   The following diagram shows a representation of a gateway supporting
   multiple Fibre Channel devices behind it.  The two Portal objects
   represent IP interfaces on the iFCP gateway that can be used to
   access any of the three Storage Node objects behind it.  Note that
   the FC Device object is not contained in the Network Entity object.
   However, each FC Device has a relationship to one or more Storage
   Node objects.

   +--------------------------------------------------------+
   |                         IP Network                     |
   +--------+-----------------+-----------------------------+
            |                 |
   +-+------+------+---+------+------+----------------------+
   | | PORTAL      |   | PORTAL      | NETWORK ENTITY       |
   | | -IP Addr 1  |   | -IP Addr 2  | -Entity ID (FQDN):   |
   | | -TCP Port 1 |   | -TCP Port 2 |  "gtwy1.example.com" |
   | +-----+ +-----+   +-----+ +-----+ -Protocol: iFCP      |
   |       | |               | |                            |
   | +-----+ +---------------+ +----------------------+     |
   | +-----+ +---------------+ +-------------+ +------+     |
   |       | |               | |             | |            |
   | +-----+ +-----+    +----+ +------+ +----+ +------+     |
   | |STORAGE NODE |    |STORAGE NODE | |STORAGE NODE |     |
   | | -WWPN 1     |    | -WWPN 2     | | -WWPN 3     |     |
   | | -Port ID 1  |    | -Port ID 2  | | -Port ID 3  |     |
   | | -FWWN 1     |    | -FWWN 2     | | -FWWN 3     |     |
   | | -FC COS     |    | -FC COS     | | -FC COS     |     |
   | +------+------+    +-------+-----+ +----+--------+     |
   +--------|-------------------|------------|--------------+
            |                   |            |
     +------+------+        +---+------------+---+
     | FC DEVICE   |        |    FC DEVICE       |
     | -WWNN 1     |        |   -WWNN 2          |
     |             |        |                    |
     +-------------+        +--------------------+

4.2.3.  Required Commands and Response Messages for Support of iFCP

   The iSNSP messages and responses displayed in the following tables
   are available to support iFCP gateways.  Messages indicated in the
   REQUIRED TO IMPLEMENT column MUST be supported by the iSNS server
   used by iFCP gateways.  Messages indicated in the REQUIRED TO USE
   column MUST be supported by the iFCP gateways themselves.

                                                     REQUIRED for:
   Message Description       Abbreviation  Func ID   Server   Client
   -------------------       ------------  -------   ------   ------
   RESERVED                                0x0000
   Device Attr Reg Request   DevAttrReg    0x0001       *       *
   Device Attr Query Request DevAttrQry    0x0002       *       *
   Device Get Next Request   DevGetNext    0x0003       *
   Device Dereg Request      DevDereg      0x0004       *       *
   SCN Register Request      SCNReg        0x0005       *
   SCN Deregister Request    SCNDereg      0x0006       *
   SCN Event                 SCNEvent      0x0007       *
   State Change Notification SCN           0x0008       *
   DD Register               DDReg         0x0009       *       *
   DD Deregister             DDDereg       0x000A       *       *
   DDS Register              DDSReg        0x000B       *       *
   DDS Deregister            DDSDereg      0x000C       *       *
   Entity Status Inquiry     ESI           0x000D       *
   Name Service Heartbeat    Heartbeat     0x000E       *
   Reserved                  Reserved      0x000F-0x0010
   Request FC_DOMAIN_ID      RqstDomId     0x0011
   Release FC_DOMAIN_ID      RlseDomId     0x0012
   Get FC_DOMAIN_IDs         GetDomId      0x0013
   RESERVED                                0x0014-0x00FF
   Vendor Specific                         0x0100-0x01FF
   RESERVED                                0x0200-0x7FFF

   The following are iSNSP response messages in support of iFCP:

                                                     REQUIRED for:
   Response Message Desc     Abbreviation  Func_ID   Server   Client
   ---------------------     ------------  -------   ------   ------
   RESERVED                                0x8000
   Device Attr Reg Rsp       DevAttrRegRsp 0x8001       *       *
   Device Attr Query Rsp     DevAttrQryRsp 0x8002       *       *
   Device Get Next Rsp       DevGetNextRsp 0x8003       *
   Device Deregister Rsp     DevDeregRsp   0x8004       *       *
   SCN Register Rsp          SCNRegRsp     0x8005       *
   SCN Deregister Rsp        SCNDeregRsp   0x8006       *
   SCN Event Rsp             SCNEventRsp   0x8007       *
   SCN Rsp                   SCNRsp        0x8008       *

   DD Register Rsp           DDRegRsp      0x8009       *       *
   DD Deregister Rsp         DDDeregRsp    0x800A       *       *
   DDS Register Rsp          DDSRegRsp     0x800B       *       *
   DDS Deregister Rsp        DDSDeregRsp   0x800C       *       *
   Entity Status Inquiry Rsp ESIRsp        0x800D       *
   NOT USED                                0x800E
   RESERVED                                0x800F-0x8010
   Request FC_DOMAIN_ID Rsp  RqstDomIdRsp  0x8011
   Release FC_DOMAIN_ID Rsp  RlseDomIdRsp  0x8012
   Get FC_DOMAIN_IDs         GetDomIdRsp   0x0013
   RESERVED                                0x8014-0x80FF
   Vendor Specific                         0x8100-0x81FF
   RESERVED                                0x8200-0xFFFF

5.  iSNSP Message Format

   The iSNSP message format is similar to the format of other common
   protocols such as DHCP, DNS and BOOTP.  An iSNSP message may be sent
   in one or more iSNS Protocol Data Units (PDU).  Each PDU is 4-byte
   aligned.  The following describes the format of the iSNSP PDU:

   Byte   MSb                                        LSb
   Offset 0                   15 16                   31
          +---------------------+----------------------+
        0 |   iSNSP VERSION     |    FUNCTION ID       | 4 Bytes
          +---------------------+----------------------+
        4 |     PDU LENGTH      |       FLAGS          | 4 Bytes
          +---------------------+----------------------+
        8 |   TRANSACTION ID    |    SEQUENCE ID       | 4 Bytes
          +---------------------+----------------------+
       12 |                                            |
          |                PDU PAYLOAD                 | N Bytes
          |                    ...                     |
          +--------------------------------------------+
     12+N | AUTHENTICATION BLOCK (Multicast/Broadcast) | L Bytes
          +--------------------------------------------+
                   Total Length = 12 + N + L

5.1.  iSNSP PDU Header

   The iSNSP PDU header contains the iSNSP VERSION, FUNCTION ID, PDU
   LENGTH, FLAGS, TRANSACTION ID, and SEQUENCE ID fields as defined
   below.

5.1.1.  iSNSP Version

   The iSNSP version described in this document is 0x0001.  All other
   values are RESERVED.  The iSNS server MAY reject messages for iSNSP
   version numbers that it does not support.

5.1.2.  iSNSP Function ID

   The FUNCTION ID defines the type of iSNS message and the operation to
   be executed.  FUNCTION_ID values with the leading bit cleared
   indicate query, registration, and notification messages, whereas
   FUNCTION_ID values with the leading bit set indicate response
   messages.

   See Section 4 under the appropriate protocol (i.e., iSCSI or iFCP)
   for a mapping of the FUNCTION_ID value to the iSNSP Command or
   Response message.  All PDUs comprising an iSNSP message must have the
   same FUNCTION_ID value.

5.1.3.  iSNSP PDU Length

   The iSNS PDU Length specifies the length of the PDU PAYLOAD field in
   bytes.  The PDU Payload contains TLV attributes for the operation.

   Additionally, response messages contain a success/failure code.  The
   PDU Length MUST be 4-byte aligned.

5.1.4.  iSNSP Flags

   The FLAGS field indicates additional information about the message
   and the type of Network Entity that generated the message.  The
   following table displays the valid flags:

          Bit Position      Enabled (1) means:
          ------------      -----------------
           16               Sender is the iSNS client
           17               Sender is the iSNS server
           18               Authentication block is present
           19               Replace flag (for DevAttrReg)
           20               Last PDU of the iSNS message
           21               First PDU of the iSNS message
           22-31            RESERVED

5.1.5.  iSNSP Transaction ID

   The TRANSACTION ID MUST be set to a unique value for each
   concurrently outstanding request message.  Replies MUST use the same
   TRANSACTION ID value as the associated iSNS request message.  If a

   message is retransmitted, the original TRANSACTION ID value MUST be
   used.  All PDUs comprising an iSNSP message must have the same
   TRANSACTION ID value.

5.1.6.  iSNSP Sequence ID

   The SEQUENCE ID has a unique value for each PDU within a single
   transaction.  The SEQUENCE_ID value of the first PDU transmitted in a
   given iSNS message MUST be zero (0), and each SEQUENCE_ID value in
   each PDU MUST be numbered sequentially in the order in which the PDUs
   are transmitted.  Note that the two-byte SEQUENCE ID allows for up to
   65536 PDUs per iSNS message.

5.2.  iSNSP Message Segmentation and Reassembly

   iSNS messages may be carried in one or more iSNS PDUs.  If only one
   iSNS PDU is used to carry the iSNS message, then bit 21 (First PDU)
   and bit 20 in the FLAGS field (Last PDU) SHALL both be set.  If
   multiple PDUs are used to carry the iSNS message, then bit 21 SHALL
   be set in the first PDU of the message, and bit 20 SHALL be set in
   the last PDU.

   All PDUs comprising the same iSNSP message SHALL have the same
   FUNCTION_ID and TRANSACTION_ID values.  Each PDU comprising an iSNSP
   message SHALL have a unique SEQUENCE_ID value.

5.3.  iSNSP PDU Payload

   The iSNSP PDU PAYLOAD is of variable length and contains attributes
   used for registration and query operations.  The attribute data items
   use a format similar to that of other protocols, such as DHCP
   [RFC2131] options.  Each iSNS attribute is specified in the PDU
   Payload using Tag-Length-Value (TLV) data format, as shown below:

   Byte   MSb                                        LSb
   Offset 0                                           31
          +--------------------------------------------+
        0 |               Attribute Tag                | 4 Bytes
          +--------------------------------------------+
        4 |            Attribute Length (N)            | 4 Bytes
          +--------------------------------------------+
        8 |                                            |
          |              Attribute Value               | N Bytes
          |                                            |
          +--------------------------------------------+
                   Total Length = 8 + N

   Attribute Tag:    a 4-byte field that identifies the attribute as
                     defined in Section 6.1.  This field contains the
                     tag value from the indicated table.

   Attribute Length: a 4-byte field that indicates the length, in bytes,
                     of the value field to follow in the TLV.  For
                     variable-length attributes, the value field MUST
                     contain padding bytes, if necessary, in order to
                     achieve 4-byte alignment.  A "zero-length TLV"
                     contains only the attribute tag and length fields.

   Attribute Value:  a variable-length field containing the attribute
                     value and padding bytes (if necessary).

   The above format is used to identify each attribute in the PDU
   Payload.  Note that TLV boundaries need not be aligned with PDU
   boundaries; PDUs may carry one or more TLVs, or any fraction thereof.
   The Response Status Code, contained in response message PDU Payloads
   and described below, is not in TLV format.  PDU Payloads for messages
   that do not contain iSNS attributes, such as the Name Service
   Heartbeat, do not use the TLV format.

5.3.1.  Attribute Value 4-Byte Alignment

   All attribute values are aligned to 4-byte boundaries.  For variable
   length attributes, if necessary, the TLV length MUST be increased to
   the next 4-byte boundary through padding with bytes containing zero
   (0).  If an attribute value is padded, a combination of the tag and
   attribute value itself is used to determine the actual value length
   and number of pad bytes.  There is no explicit count of the number of
   pad bytes provided in the TLV.

5.4.  iSNSP Response Status Codes

   All iSNSP response messages contain a 4-byte Status Code field as the
   first field in the iSNSP PDU PAYLOAD.  If the original iSNSP request
   message was processed normally by the iSNS server, or by the iSNS
   client for ESI and SCN messages, then this field SHALL contain a
   status code of 0 (Successful).  A non-zero status code indicates
   rejection of the entire iSNS client request message.

          Status Code      Status Description
          -----------      -----------------
            0              Successful
            1              Unknown Error
            2              Message Format Error
            3              Invalid Registration
            4              RESERVED
            5              Invalid Query
            6              Source Unknown
            7              Source Absent
            8              Source Unauthorized
            9              No Such Entry
           10              Version Not Supported
           11              Internal Error
           12              Busy
           13              Option Not Understood
           14              Invalid Update
           15              Message (FUNCTION_ID) Not Supported
           16              SCN Event Rejected
           17              SCN Registration Rejected
           18              Attribute Not Implemented
           19              FC_DOMAIN_ID Not Available
           20              FC_DOMAIN_ID Not Allocated
           21              ESI Not Available
           22              Invalid Deregistration
           23              Registration Feature Not Supported
           24 and above    RESERVED

5.5.  Authentication for iSNS Multicast and Broadcast Messages

   For iSNS multicast and broadcast messages (see Section 2.9.3), the
   iSNSP provides authentication capability.  The following section
   details the iSNS Authentication Block, which is identical in format
   to the SLP authentication block [RFC2608]. iSNS unicast messages
   SHOULD NOT include the authentication block, but rather should rely
   upon IPSec security mechanisms.

   If a message contains an authentication block, then the
   "Authentication block present" bit in the iSNSP PDU header FLAGS
   field SHALL be enabled.

   If a PKI is available with an [X.509] Certificate Authority (CA),
   then public key authentication of the iSNS server is possible.  The
   authentication block leverages the DSA with SHA-1 algorithm, which
   can easily integrate into a public key infrastructure.

   The authentication block contains a digital signature for the
   multicast message.  The digital signature is calculated on a per-PDU
   basis.  The authentication block contains the following information:

   1.  A time stamp, to prevent replay attacks.
   2.  A structured authenticator containing a signature calculated over
       the time stamp and the message being secured.
   3.  An indicator of the cryptographic algorithm that was used to
       calculate the signature.
   4.  An indicator of the keying material and algorithm parameters,
       used to calculate the signature.

   The authentication block is described in the following figure:

      Byte   MSb                              LSb
      Offset 0                                 31
             +----------------------------------+
         0   |    BLOCK STRUCTURE DESCRIPTOR    |     4 Bytes
             +----------------------------------+
         4   |   AUTHENTICATION BLOCK LENGTH    |     4 Bytes
             +----------------------------------+
         8   |           TIMESTAMP              |     8 Bytes
             +----------------------------------+
        16   |       SPI STRING LENGTH          |     4 Bytes
             +----------------------------------+
        20   |           SPI STRING             |     N Bytes
             +----------------------------------+
    20 + N   |     STRUCTURED AUTHENTICATOR     |     M Bytes
             +----------------------------------+
                Total Length = 20 + N + M

   BLOCK STRUCTURE DESCRIPTOR (BSD): Defines the structure and algorithm
              to use for the STRUCTURED AUTHENTICATOR.  BSD values from
              0x00000000 to 0x00007FFF are assigned by IANA, while
              values 0x00008000 to 0x00008FFF are for private use.

   AUTHENTICATION BLOCK LENGTH: Defines the length of the authentication
              block, beginning with the BSD field and running through
              the last byte of the STRUCTURED AUTHENTICATOR.

   TIMESTAMP: This is an 8-byte unsigned, fixed-point integer giving the
              number of seconds since 00:00:00 GMT on January 1, 1970.

   SPI STRING LENGTH: The length of the SPI STRING field.

   SPI STRING (Security Parameters Index): Index to the key and
              algorithm used by the message recipient to decode the
              STRUCTURED AUTHENTICATOR field.

   STRUCTURED AUTHENTICATOR: Contains the digital signature.  For the
              default BSD value of 0x0002, this field SHALL contain the
              binary ASN.1 encoding of output values from the DSA with
              SHA-1 signature calculation as specified in Section 2.2.2
              of [RFC3279].

5.6.  Registration and Query Messages

   The iSNSP registration and query message PDU Payloads contain a list
   of attributes, and have the following format:

             +----------------------------------------+
             |     Source Attribute (Requests Only)   |
             +----------------------------------------+
             |  Message Key Attribute[1] (if present) |
             +----------------------------------------+
             |  Message Key Attribute[2] (if present) |
             +----------------------------------------+
             |               . . .                    |
             +----------------------------------------+
             |       - Delimiter Attribute -          |
             +----------------------------------------+
             |   Operating Attribute[1] (if present)  |
             +----------------------------------------+
             |   Operating Attribute[2] (if present)  |
             +----------------------------------------+
             |   Operating Attribute[3] (if present)  |
             +----------------------------------------+
             |                 . . .                  |
             +----------------------------------------+

   Each Source, Message Key, Delimiter, and Operating attribute is
   specified in the PDU Payload using the Tag-Length-Value (TLV) data
   format. iSNS Registration and Query messages are sent by iSNS Clients

   to the iSNS server IP Address and well-known TCP/UDP Port.  The iSNS
   Responses will be sent to the iSNS Client IP address and TCP/UDP port
   number from the original request message.

5.6.1.  Source Attribute

   The Source Attribute is used to identify the Storage Node to the iSNS
   server for queries and other messages that require source
   identification.  The Source Attribute uniquely identifies the source
   of the message.  Valid Source Attribute types are shown below.

          Valid Source Attributes
          -----------------------
           iSCSI Name
           FC Port Name WWPN

   For a query operation, the Source Attribute is used to limit the
   scope of the specified operation to the Discovery Domains of which
   the source is a member.  Special Control Nodes, identified by the
   Source Attribute, may be administratively configured to perform the
   specified operation on all objects in the iSNS database without
   scoping to Discovery Domains.

   For messages that change the contents of the iSNS database, the iSNS
   server MUST verify that the Source Attribute identifies either a
   Control Node or a Storage Node that is a part of the Network Entity
   containing the added, deleted, or modified objects.

5.6.2.  Message Key Attributes

   Message Key attributes are used to identify matching objects in the
   iSNS database for iSNS query and registration messages.  If present,
   the Message Key MUST be a Registration or Query Key for an object as
   described in Sections 5.6.5 and 6.1.  A Message Key is not required
   when a query spans the entire set of objects available to the Source
   or a registration is for a new Entity.

   iSCSI Names used in the Message Key MUST be normalized according to
   the stringprep template [STRINGPREP].  Entity Identifiers (EIDs) used
   in the Message Key MUST be normalized according to the nameprep
   template [NAMEPREP].

5.6.3.  Delimiter Attribute

   The Delimiter Attribute separates the Message Key attributes from the
   Operating Attributes in a PDU Payload.  The Delimiter Attribute has a
   tag value of 0 and a length value of 0.  The Delimiter Attribute is
   always 8 bytes long (a 4-byte tag field and a 4-byte length field,

   all containing zeros).  If a Message Key is not required for a
   message, then the Delimiter Attribute immediately follows the Source
   Attribute.

5.6.4.  Operating Attributes

   The Operating Attributes are a list of one or more key and non-key
   attributes related to the actual iSNS registration or query operation
   being performed.

   Operating Attributes include object key attributes and non-key
   attributes.  Object key attributes uniquely identify iSNS objects.
   Key attributes MUST precede the non-key attributes of each object in
   the Operating Attributes.  The tag value distinguishes the attribute
   as an object key attribute (i.e., tag=1, 16&17, 32, 64, and 96) or a
   non-key attribute. iSCSI Names used in the Operating Attributes MUST
   be normalized according to the stringprep template [STRINGPREP].
   Entity Identifiers (EIDs) used in the Operating Attributes MUST be
   normalized according to the nameprep template [NAMEPREP].

   The ordering of Operating Attributes in the message is important for
   determining the relationships among objects and their ownership of
   non-key attributes.  iSNS protocol messages that violate these
   ordering rules SHALL be rejected with the Status Code of 2 (Message
   Format Error).  See the message descriptions for proper operating
   attribute ordering requirements.

   Some objects are keyed by more than one object key attribute value.
   For example, the Portal object is keyed by attribute tags 16 and 17.
   When describing an object keyed by more than one key attribute, every
   object key attribute of that object MUST be listed sequentially by
   tag value in the message before non-key attributes of that object and
   key attributes of the next object.  A group of key attributes of this
   kind is treated as a single logical key attribute when identifying an
   object.

   Non-key attributes that immediately follow key attributes MUST be
   attributes of the object referenced by the key attributes.  All non-
   key attributes of an object MUST be listed before the object key
   attributes introducing the next object.

   Objects MUST be listed in inheritance order, according to their
   containment order.  Storage Node and Portal objects and their
   respective attributes MUST follow the Network Entity object to which
   they have a relationship.  Similarly, FC Device objects MUST follow
   the Storage Node object to which they have a relationship.

   Vendor-specific objects defined by tag values in the range 1537-2048
   have the same requirements described above.

5.6.4.1.  Operating Attributes for Query and Get Next Requests

   In Query and Get Next request messages, TLV attributes with length
   value of 0 are used to indicate which Operating Attributes are to be
   returned in the corresponding response.  Operating Attribute values
   that match the TLV attributes in the original message are returned in
   the response message.

5.6.5.  Registration and Query Request Message Types

   The following describes each query and message type.

5.6.5.1.  Device Attribute Registration Request (DevAttrReg)

   The DevAttrReg message type is 0x0001.  The DevAttrReg message
   provides the means for iSNS clients to update existing objects or
   register new objects.  The value of the replace bit in the FLAGs
   field determines whether the DevAttrReg message updates or replaces
   an existing registration.

   The Source Attribute identifies the Node initiating the registration
   request.

   The Message Key identifies the object the DevAttrReg message acts
   upon.  It MUST contain the key attribute(s) identifying an object.
   This object MUST contain all attributes and related subordinate
   object attributes that will be included in the Operating Attributes
   of the DevAttrReg PDU Payload.  The key attribute(s) identifying this
   object MUST also be included among the Operating Attributes.

   If the Message Key contains an EID and no pre-existing objects match
   the Message Key, then the DevAttrReg message SHALL create a new
   Entity with the specified EID and any new object(s) specified by the
   Operating Attributes.  The replace bit SHALL be ignored.

   If the Message Key does not contain an EID, and no pre-existing
   objects match the Message Key, then the DevAttrReg message SHALL be
   rejected with a status code of 3 (Invalid Registration).

   If the Message Key is not present, then the DevAttrReg message
   implicitly registers a new Network Entity.  In this case, the replace
   bit SHALL be ignored; a new Network Entity SHALL be created.
   Existing entities, their objects, and their relationships remain
   unchanged.

   The replace bit determines the kind of operation conducted on the
   object identified in the DevAttrReg Message Key.  The replace bit
   only applies to the DevAttrReg message; it is ignored for all other
   message types.

   If the replace bit is set, then the objects, attributes, and
   relationships specified in the Operating Attributes SHALL replace the
   object identified by the Message Key.  The object and all of its
   subordinate objects SHALL be deregistered, and the appropriate SCNs
   SHALL be sent by the iSNS server for the deregistered objects.  The
   objects listed in the Operating Attributes are then used to replace
   the just-deregistered objects.  Note that additional SCNs SHALL be
   sent for the newly-registered objects, if appropriate.  Existing
   objects and relationships that are not identified or that are
   subordinate to the object identified by the Message Key MUST NOT be
   affected or changed.

   If the replace bit is not set, then the message updates the
   attributes of the object identified by the Message Key and its
   subordinate objects.  Existing object containment relationships MUST
   NOT be changed.  For existing objects, key attributes MUST NOT be
   modified, but new subordinate objects MAY be added.

   The Operating Attributes represent objects, attributes, and
   relationships that are to be registered.  Multiple related objects
   and attributes MAY be registered in a single DevAttrReg message.  The
   ordering of the objects in this message indicates the structure of,
   and associations among, the objects to be registered.  At least one
   object MUST be listed in the Operating Attributes.  Additional
   objects (if any) MUST be subordinate to the first object listed.  Key
   attributes MUST precede non-key attributes of each object.  A given
   object may only appear a maximum of once in the Operating Attributes
   of a message.  If the Node identified by the Source Attribute is not
   a Control Node, then the objects in the operating attributes MUST be
   members of the same Network Entity as the Source Node.

   For example, to establish relationships between a Network Entity
   object and its Portal and Storage Node objects, the Operating
   Attributes list the key and non-key attributes of the Network Entity
   object, followed by the key and non-key attributes of each Portal and
   Storage Node object to be linked to that Network Entity.  Similarly,
   an FC Device object that follows a Storage Node object is considered
   subordinate to that Storage Node.

   New PG objects are registered when an associated Portal or iSCSI Node
   object is registered.  An explicit PG object registration MAY follow
   a Portal or iSCSI Node object registration in a DevAttrReg message.

   When a Portal is registered, the Portal attributes MAY immediately be
   followed by a PGT attribute.  The PGT attribute SHALL be followed by
   the set of PG iSCSI Names representing nodes that will be associated
   to the Portal using the indicated PGT value.  Additional sets of PGTs
   and PG iSCSI Names to be associated to the registered Portal MAY
   follow.  Indicated PGT values are assigned to the PG object
   associated with the newly registered Portal and to the iSCSI Storage
   Node(s) referenced immediately following the PGT attribute in the
   operating attributes.

   When an iSCSI Storage Node is registered, the Storage Node attributes
   MAY immediately be followed by a PGT attribute.  The PGT attribute
   SHALL be followed by the set of PG Portal IP-Address, PG TCP/UDP Port
   pairs representing Portal objects that will be associated with the
   Storage Node using the indicated PGT value.  Additional sets of PGTs
   and PG Portal IP-Address PG TCP/UDP Port pairs to be associated with
   the registered Storage Node MAY follow.  Indicated PGT values are
   assigned to the PG object associated with the newly registered iSCSI
   Storage Node and Portal object(s) referenced immediately following
   the PGT attribute in the operating attributes.

   If the PGT value is not included in the Storage Node or Portal object
   registration, and if a PGT value was not previously registered for
   the relationship, then the PGT for the corresponding PG object SHALL
   be registered with a value of 0x00000001.  If the PGT attribute is
   included in the registration message as a 0-length TLV, then the PGT
   value for the corresponding PG object SHALL be registered as NULL.  A
   0-length TLV for the PGT in an update registration message overwrites
   the previous PGT value with NULL, indicating that there is no
   relationship between the Storage Node and Portal.

   A maximum of one Network Entity object can be created or updated with
   a single DevAttrReg message.  Consequently, the Operating Attributes
   MUST NOT contain more than one Network Entity object.  There is no
   limit to the number of Portal, Storage Node, and FC Device objects
   that can listed in the Operating Attributes, provided they are all
   subordinate to the listed Network Entity object.

   If the Message Key and Operating Attributes do not contain an EID
   attribute, or if the EID attribute has a length of 0, then a new
   Network Entity object SHALL be created and the iSNS server SHALL
   supply a unique EID value for it.  The assigned EID value SHALL be
   included in the DevAttrReg Response message.  If the Message Key and
   Operating Attributes contain an EID that does not match the EID of an
   existing Network Entity in the iSNS database, then a new Network
   Entity SHALL be created and assigned the value contained in that EID
   attribute.  Finally, if the Message Key and Operating Attributes
   contain an EID that matches the EID of an existing object in the iSNS

   database, then the objects, attributes, and relationships specified
   in the Operating Attributes SHALL be appended to the existing Network
   Entity identified by the EID.

   A registration message that creates a new Network Entity object MUST
   contain at least one Portal or one Storage Node.  If the message does
   not, then it SHALL be considered invalid and result in a response
   with Status Code of 3 (Invalid Registration).

   If an iSNS Server does not support a registration feature, such as
   explicit PG object registration, then the server SHALL return a
   Status Code of 23 (Registration Feature Not Supported).

   Note that the iSNS server may modify or reject the registration of
   certain attributes, such as ESI Interval.  In addition, the iSNS
   server may assign values for additional Operating Attributes that are
   not explicitly registered in the original DevAttrReg message, such as
   the EID and WWNN Token.

5.6.5.2.  Device Attribute Query Request (DevAttrQry)

   The DevAttrQry message type is 0x0002.  The DevAttrQry message
   provides an iSNS client with the means to query the iSNS server for
   object attributes.

   The Source Attribute identifies the Node initiating the request.  For
   non-Control Nodes initiating the DevAttrQry message, the query is
   scoped to the Discovery Domains of which the initiating Node is a
   member.  The DevAttrQry message SHALL only return information on
   Storage Nodes and their related parent and subordinate objects, where
   the Storage Node has a common Discovery Domain with the Node
   identified in the Source Attribute.

   The Message Key may contain key or non-key attributes or no
   attributes at all.  If multiple attributes are used as the Message
   Key, then they MUST all be from the same object type (e.g., IP
   address and TCP/UDP Port are attributes of the Portal object type).
   A Message Key with non-key attributes may match multiple instances of
   the specific object type.  A Message Key with zero-length TLV(s) is
   scoped to every object of the type indicated by the zero-length
   TLV(s).  An empty Message Key field indicates the query is scoped to
   the entire database accessible by the source Node.

   The DevAttrQry response message returns attributes of objects listed
   in the Operating Attributes that are related to the Message Key of
   the original DevAttrQry message.  The Operating Attributes of the
   DevAttrQry message contain zero-length TLVs that specify the
   attributes that are to be returned in the DevAttrQryRsp message.  A

   Message Key containing zero-length TLVs indicates that the set of
   attributes specified in the Operating Attributes are to be returned
   for each object matching the type indicated by the Message Key.

   If the Message Key contains non-zero length TLVs, then Operating
   Attributes for the object matching the Message Key SHALL be returned
   in the DevAttrQryRsp message.  Each attribute type (i.e., zero-length
   TLV) in the Operating Attributes indicates an attribute from the
   object matching the Message Key, or from other objects in the same
   Entity having a relationship to the object matching the Message Key,
   is to be returned in the response.  The ordering of the object keys
   and associated attributes returned in the DevAttrQry response message
   SHALL be the same as in the original query message.  If no objects
   match the Message Key, then the DevAttrQryRsp message SHALL NOT
   return any operating attributes.  Such a message and its
   corresponding response SHALL NOT be considered an error.

   The Portal Group object determines whether a relationship exists
   between a given Storage Node and Portal object.  If the PGT of the
   Portal Group is not NULL, then a relationship exists between the
   indicated Storage Node and Portal; if the PGT is NULL, then no
   relationship exists.  Therefore, the value (NULL or not NULL) of the
   PGT attribute of each Portal Group object determines the structure
   and ordering of the DevAttrQry response to a query for Storage Nodes
   and Portals.

   For example, an iSNS database contains a Network Entity having two
   Portals and two Nodes.  Each Storage Node has two Portal Groups, one
   with a NULL PGT value for one Portal and another with a non-NULL PGT
   value for the other Portal.  The DevAttrQry message contains a
   Message Key entry matching one of the Nodes, and Operating Attributes
   with zero-length TLVs listing first the Node attributes, Portal
   attributes, and then the PG attributes.  The response message SHALL
   therefore return first the matching Node object, then the requested
   attributes of the one Portal object that can be used to access the
   Storage Node (as indicated by the PGT), and finally the requested
   attributes of the PG object used to access that Storage Node.  The
   order in which each object's attributes are listed is the same as the
   ordering of the object's attributes in the Operating Attributes of
   the original request message.

   If the Message Key Attribute contains zero-length TLV(s), then the
   query returns requested attributes for all objects matching the
   Message Key type (DD restrictions SHALL apply for non-Control Nodes).
   If multiple objects match the Message Key type, then the attributes
   for each object matching the Message Key MUST be listed before the
   attributes for the next matching object are listed in the query

   response.  In other words, the process described above must be
   iterated in the message response for each object that matches the
   Message Key type specified by the zero-length TLV(s).

   For example, an iSNS database contains only one Network Entity having
   two Portals and three Nodes.  All PG objects in the Entity have a PGT
   value of 0x00000001.  In the DevAttrQry message, the Message Key
   contains a zero-length TLV specifying a Node type, and Operating
   Attributes listing first the Node attributes, and then the Portal
   attributes.  The response message will return, in the following
   order, the attributes for the first, next, and last Node objects,
   each followed by attributes for both Portals.  If that same
   DevAttrQry message had instead contained a zero-length TLV specifying
   the Network Entity type, then the response message would have
   returned attributes for all three Node objects, followed by
   attributes for the two Portals.

   If there is no Message Key Attribute, then the query returns all
   attributes in the iSNS database (once again, DD restrictions SHALL
   apply for non-Control Nodes).  All attributes matching the type
   specified by each zero-length TLV in the Operating Attributes SHALL
   be listed.  All attributes of each type SHALL be listed before the
   attributes matching the next zero-length TLV are listed.

   For example, an iSNS database contains two Entities, each having two
   Nodes and two Portals.  The DevAttrQry message contains no Message
   Key attribute, and Operating Attributes list first the Portal
   attributes, and then the Node attributes.  The Operating Attributes
   of the response message will return attributes from each of the four
   Portals, followed by attributes from each of the four nodes.

   If a DevAttrQry message requests an attribute for which the iSNS
   server has no value, then the server SHALL NOT return the requested
   attribute in the query response.  Such query and response messages
   SHALL NOT be considered errors.

   Registration and query messages for iSNS server-specific attributes
   (i.e., tags in the range 132 to 384) SHALL be formatted using the
   identifying key attribute of the Storage Node originating the query
   (i.e., iSCSI Name or FC Port Name WWPN) for both the Source Attribute
   and Message Key attribute.  Operating Attributes SHALL include the
   TLV of the server-specific attribute being requested.

   DD membership can be discovered through the DevAttrQry message by
   including either DD member attributes (i.e., DD Member iSCSI Index,
   DD Member iSCSI Node, DD Member iFCP Node, DD Member Portal Index, DD
   Member Portal IP Addr, and DD Member Portal TCP/UDP) or the object
   key of the Storage Node or Portal (i.e., iSCSI Name, iSCSI Index,

   Portal IP Addr, Portal TCP/UDP Port, and Portal Index) in the
   Operating Attributes.  Using DD member attributes SHALL return both
   registered and unregistered member Storage Nodes and/or Portals of a
   DD.  DevAttrQry messages using the Storage Node and/or Portal object
   key SHALL return only member Storage Nodes or Portals that are
   currently registered in the iSNS database.

   The DevAttrQry message SHALL support the following minimum set of
   Message Key Attributes:

          Valid Message Key Attributes for Queries
          ----------------------------------------
           Entity Identifier
           Entity Protocol
           Portal IP-Address & Portal TCP/UDP Port
           Portal Index
           iSCSI Node Type
           iSCSI Name
           iSCSI Index
           PG Index
           FC Port Name WWPN
           FC Port Type
           FC-4 Type
           Discovery Domain ID
           Discovery Domain Set ID
           Source Attribute (for server-specific attributes)
           Switch Name (FC Device WWNN--for Virtual_Fabric_ID queries)

5.6.5.3.  Device Get Next Request (DevGetNext)

   The DevGetNext message type is 0x0003.  This message provides the
   iSNS client with the means to retrieve each and every instance of an
   object type exactly once.

   The Source Attribute identifies the Node initiating the DevGetNext
   request, and is used to scope the retrieval process to the Discovery
   Domains of which the initiating Node is a member.

   The Message Key Attribute may be an Entity Identifier (EID), iSCSI
   Name, iSCSI Index, Portal IP Address and TCP/UDP Port, Portal Index,
   PG Index, FC Node Name WWNN, or FC Port Name WWPN.  If the TLV length
   of the Message Key Attribute(s) is zero, then the first object entry
   in the iSNS database matching the Message Key type SHALL be returned
   in the Message Key of the corresponding DevGetNextRsp message.  If
   non-zero-length TLV attributes are contained in the Message Key, then
   the DevGetNext response message SHALL return the next object stored
   after the object identified by the Message Key in the original
   DevGetNext request message.

   If the Message Key provided matches the last object instance in the
   iSNS database, then the Status Code of 9 (No Such Entry) SHALL be
   returned in the response.

   The Operating Attributes can be used to specify the scope of the
   DevGetNext request, and to specify the attributes of the next object,
   which are to be returned in the DevGetNext response message.  All
   Operating Attributes MUST be attributes of the object type identified
   by the Message Key.  For example, if the Message Key is an Entity_ID
   attribute, then the Operating Attributes MUST NOT contain attributes
   of Portals.

   Non-zero-length TLV attributes in the Operating Attributes are used
   to scope the DevGetNext message.  Only the next object with attribute
   values that match the non-zero-length TLV attributes SHALL be
   returned in the DevGetNext response message.

   Zero-length TLV attributes MUST be listed after non-zero-length
   attributes in the Operating Attributes of the DevGetNext request
   message.  Zero-length TLV attributes specify the attributes of the
   next object which are to be returned in the DevGetNext response
   message.

   Note that there are no specific requirements concerning the order in
   which object entries are retrieved from the iSNS database; the
   retrieval order of object entries using the DevGetNext message is
   implementation specific.

   The iSNS client is responsible for ensuring that information acquired
   through use of the DevGetNext message is accurate and up-to-date.
   There is no assurance that the iSNS database will not change between
   successive DevGetNext request messages.  If the Message Key provided
   does not match an existing database entry, then attributes for the
   next object key following the provided Message Key SHALL be returned.
   For example, an object entry may have been deleted between successive
   DevGetNext messages.  This may result in a DevGetNext request in
   which the Message Key does not match an existing object entry.  In
   this case, attributes for the next object stored in the iSNS database
   are returned.

5.6.5.4.  Device Deregister Request (DevDereg)

   The DevDereg message type is 0x0004.  This message is used to remove
   object entries from the iSNS database.  One or more objects may be
   removed through a single DevDereg message.  Note that deregistered
   Storage Node objects will retain membership in their Discovery
   Domain(s) until explicit deregistration of the membership(s) or
   Discovery Domain(s).

   Upon receiving the DevDereg, the iSNS server removes all objects
   identified by the Operating Attribute(s), and all subordinate objects
   that are solely dependent on those identified objects.  For example,
   removal of a Network Entity also results in removal of all associated
   Portal, Portal Group, Storage Node, and FC Device objects associated
   with that Network Entity.  FC Device objects SHALL not be
   deregistered in this manner unless all Storage Nodes associated with
   them have been deregistered.

   The DevDereg request PDU Payload contains a Source Attribute and
   Operating Attribute(s); there are no Message Key Attributes.  If the
   Node identified by the Source Attribute is not a Control Node, then
   it MUST be from the same Network Entity as the object(s) identified
   for removal by the Operating Attribute(s).  Valid Operating
   Attributes are shown below:

          Valid Operating Attributes for DevDereg
          ---------------------------------------
           Entity Identifier
           Portal IP-Address & Portal TCP/UDP Port
           Portal Index
           iSCSI Name
           iSCSI Index
           FC Port Name WWPN
           FC Node Name WWNN

   The removal of the object may result in SCN messages to the
   appropriate iSNS clients.

   Attempted deregistration of non-existing entries SHALL not be
   considered an error.

   If all Nodes and Portals associated with a Network Entity are
   deregistered, then the Network Entity SHALL also be removed.

   If both the Portal and iSCSI Storage Node objects associated with a
   Portal Group object are removed, then that Portal Group object SHALL
   also be removed.  The Portal Group object SHALL remain registered as
   long as either of its associated Portal or iSCSI Storage Node objects
   remain registered.  If a deleted Storage Node or Portal object is
   subsequently re-registered, then a relationship between the re-
   registered object and an existing Portal or Storage Node object
   registration, indicated by the PG object, SHALL be restored.

5.6.5.5.  SCN Register Request (SCNReg)

   The SCNReg message type is 0x0005.  The State Change Notification
   Registration Request (SCNReg) message allows an iSNS client to
   register a Storage Node to receive State Change Notification (SCN)
   messages.

   The SCN notifies the Storage Node of changes to any Storage Nodes
   within any DD of which it is a member.  If the Storage Node is a
   Control Node, it SHALL receive SCN notifications for changes in the
   entire network.  Note that whereas SCNReg sets the SCN Bitmap field,
   the DevAttrReg message registers the UDP or TCP Port used by each
   Portal to receive SCN messages.  If no SCN Port fields of any Portals
   of the Storage Node are registered to receive SCN messages, then the
   SCNReg message SHALL be rejected with Status Code 17 (SCN
   Registration Rejected).

   The SCNReg request PDU Payload contains a Source Attribute, a Message
   Key Attribute, and an Operating Attribute.  Valid Message Key
   Attributes for a SCNReg are shown below:

          Valid Message Key Attributes for SCNReg
          ---------------------------------------
           iSCSI Name
           FC Port Name WWPN

   The node with the iSCSI Name or FC Port Name WWPN attribute that
   matches the Message Key in the SCNReg message is registered to
   receive SCNs using the specified SCN bitmap.  A maximum of one Node
   SHALL be registered for each SCNReg message.

   The SCN Bitmap is the only operating attribute of this message, and
   it always overwrites the previous contents of this field in the iSNS
   database.  The bitmap indicates the SCN event types for which the
   Node is registering.

   Note that the settings of this bitmap determine whether the SCN
   registration is for regular SCNs or management SCNs.  Control Nodes
   MAY conduct registrations for management SCNs; iSNS clients that are
   not supporting Control Nodes MUST NOT conduct registrations for
   management SCNs.  Control Nodes that register for management SCNs
   receive a copy of every SCN message generated by the iSNS server.  It
   is recommended that management registrations be used only when needed
   in order to conserve iSNS server resources.  In addition, a Control
   Node that conducts such registrations should be prepared to receive
   the anticipated volume of SCN message traffic.

5.6.5.6.  SCN Deregister Request (SCNDereg)

   The SCNDereg message type is 0x0006.  The SCNDereg message allows an
   iSNS client to stop receiving State Change Notification (SCN)
   messages.

   The SCNDereg request message PDU Payload contains a Source Attribute
   and Message Key Attribute(s).  Valid Message Key Attributes for a
   SCNDereg are shown below:

          Valid Message Key Attributes for SCNDereg
          -----------------------------------------
           iSCSI Name
           FC Port Name WWPN

   The node with an iSCSI Name or FC Port Name WWPN attribute that
   matches the Message Key Attributes in the SCNDereg message is
   deregistered for SCNs.  The SCN bitmap field of such Nodes are
   cleared.  A maximum of one Node SHALL be deregistered for each
   SCNDereg message.

   There are no Operating Attributes in the SCNDereg message.

5.6.5.7.  SCN Event (SCNEvent)

   The SCNEvent message type is 0x0007.  The SCNEvent is a message sent
   by an iSNS client to request generation of a State Change
   Notification (SCN) message by the iSNS server.  The SCN, sent by the
   iSNS server, then notifies iFCP, iSCSI, and Control Nodes within the
   affected DD of the change indicated in the SCNEvent.

   Most SCNs are automatically generated by the iSNS server when Nodes
   are registered or deregistered from the directory database.  SCNs are
   also generated when a network management application or Control Node
   makes changes to the DD membership in the iSNS server.  However, an
   iSNS client can trigger an SCN by using SCNEvent.

   The SCNEvent message PDU Payload contains a Source Attribute, a
   Message Key Attribute, and an Operating Attribute.  Valid Key
   Attributes for a SCNEvent are shown below:

          Valid Message Key Attributes for SCNEvent
          -----------------------------------------
           iSCSI Name
           FC Port Name WWPN

   The Operating Attributes section SHALL contain the SCN Event Bitmap
   attribute.  The bitmap indicates the event that caused the SCNEvent
   to be generated.

5.6.5.8.  State Change Notification (SCN)

   The SCN message type is 0x0008.  The SCN is a message generated by
   the iSNS server, notifying a registered Storage Node of changes.
   There are two types of SCN registrations: regular registrations and
   management registrations.  Regular SCNs notify iSNS clients of events
   within the discovery domain.  Management SCNs notify Control Nodes
   that register for management SCNs of events occurring anywhere in the
   network.

   If no active TCP connection to the SCN recipient exists, then the SCN
   message SHALL be sent to one Portal of the registered Storage Node
   that has a registered TCP or UDP Port value in the SCN Port field.
   If more than one Portal of the Storage Node has a registered SCN Port
   value, then the SCN SHALL be delivered to any one of the indicated
   Portals, provided that the selected Portal is not the subject of the
   SCN.

   The types of events that can trigger an SCN message, and the amount
   of information contained in the SCN message, depend on the registered
   SCN Event Bitmap for the Storage Node.  The iSCSI Node SCN Bitmap is
   described in Section 6.4.4.  The iFCP SCN Bitmap is described in
   Section 6.6.12.

   The format of the SCN PDU Payload is shown below:

          +----------------------------------------+
          |         Destination Attribute          |
          +----------------------------------------+
          |               Timestamp                |
          +----------------------------------------+
          |          Source SCN Bitmap 1           |
          +----------------------------------------+
          |          Source Attribute [1]          |
          +----------------------------------------+
          |    Source Attribute [2](if present)    |
          +----------------------------------------+
          |    Source Attribute [3](if present)    |
          +----------------------------------------+
          |    Source Attribute [n](if present)    |
          +----------------------------------------+
          |    Source SCN Bitmap 2 (if present)    |
          +----------------------------------------+
          |                 . . .                  |
          +----------------------------------------+

   All PDU Payload attributes are in TLV format.

   The Destination Attribute is the Node identifier that is receiving
   the SCN.  The Destination Attribute can be an iSCSI Name or FC Port
   Name.

   The Timestamp field, using the Timestamp TLV format, described in
   Section 6.2.4, indicates the time the SCN was generated.

   The Source SCN Bitmap field indicates the type of SCN notification
   (i.e., regular or management SCN), and the type of event that caused
   the SCN to be generated; it does not necessarily correlate with the
   original SCN bitmap registered in the iSNS server.

   Following the timestamp, the SCN message SHALL list the SCN bitmap,
   followed by the key attribute (i.e., iSCSI Name or FC Port Name) of
   the Storage Node affected by the SCN event.  If the SCN is a
   Management SCN, then the SCN message SHALL also list the DD_ID and/or
   DDS_ID of the Discovery Domains and Discovery Domain Sets (if any)
   that caused the change in state for that Storage Node.  These
   additional attributes (i.e., DD_ID and/or DDS_ID) shall immediately
   follow the iSCSI Name or FC Port Name and precede the next SCN bitmap
   for the next notification message (if any).  The SCN bitmap is used
   as a delineator for SCN messages providing multiple state change
   notifications.

   For example, a regular SCN for notifying an iSNS client of a new
   Portal available for a particular iSCSI target would contain the SCN
   bitmap followed by the iSCSI Name of the target device as the source
   attribute.  If the SCN were a management SCN, then the iSCSI Name
   would be followed by the DD_ID(s) of the shared Discovery Domains
   that allow the destination Storage Node to have visibility to the
   affected Storage Node.  If a Discovery Domain Set (DDS) was enabled
   in order to provide this visibility, then the appropriate DDS_ID
   would be included as well.

   A management SCN is also generated to notify a Control Node of the
   creation, deletion, or modification of a Discovery Domain or
   Discovery Domain Set.  In this case, the DD_ID and/or DDS_ID of the
   affected Discovery Domain and/or Discovery Domain Set would follow
   the SCN bitmap.

   For example, a management SCN to notify a Control Node of a new DD
   within a Discovery Domain Set would contain both the DD_ID and the
   DDS_ID of the affected Discovery Domain and Discovery Domain Set
   among the Source Attributes.

   See Sections 6.4.4 and 6.6.12 for additional information on the SCN
   Bitmap.

5.6.5.9.  DD Register (DDReg)

   The DDReg message type is 0x0009.  This message is used to create a
   new Discovery Domain (DD), to update an existing DD Symbolic Name
   and/or DD Features attribute, and to add DD members.

   DDs are uniquely defined using DD_IDs.  DD registration attributes
   are described in Section 6.11.

   The DDReg message PDU Payload contains the Source Attribute and
   optional Message Key and Operating Attributes.

   The Message Key, if used, contains the DD_ID of the Discovery Domain
   to be registered.  If the Message Key contains a DD_ID of an existing
   DD entry in the iSNS database, then the DDReg message SHALL attempt
   to update the existing entry.  If the DD_ID in the Message Key (if
   used) does not match an existing DD entry, then the iSNS server SHALL
   reject the DDReg message with a status code of 3 (Invalid
   Registration).  If the DD_ID is included in both the Message Key and
   Operating Attributes, then the DD_ID value in the Message Key MUST be
   the same as the DD_ID value in the Operating Attributes.

   A DDReg message with no Message Key SHALL result in the attempted
   creation of a new Discovery Domain (DD).  If the DD_ID attribute
   (with non-zero length) is included among the Operating Attributes in
   the DDReg message, then the new Discovery Domain SHALL be assigned
   the value contained in that DD_ID attribute.  Otherwise, if the DD_ID
   attribute is not contained among the Operating Attributes of the
   DDReg message, or if the DD_ID is an operating attribute with a TLV
   length of 0, then the iSNS server SHALL assign a DD_ID value.  The
   assigned DD_ID value is then returned in the DDReg Response message.
   The Operating Attributes can also contain the DD Member iSCSI Node
   Index, DD Member iSCSI Name, DD Member FC Port Name, DD Member Portal
   IP Address, DD Member Portal TCP/UDP Port Number, or DD Member Portal
   Index of members to be added to the DD.  It may also contain the
   DD_Symbolic_Name and/or DD_Features of the DD.

   This message SHALL add any DD members listed as Operating Attributes
   to the Discovery Domain specified by the DD_ID.  If the DD_Features
   attribute is an Operating Attribute, then it SHALL be stored in the
   iSNS server as the feature list for the specified DD.  If the
   DD_Symbolic_Name is an operating attribute and its value is unique
   (i.e., it does not match the registered DD_Symbolic_Name for another
   DD), then the value SHALL be stored in the iSNS database as the
   DD_Symbolic_Name for the specified Discovery Domain.  If the value
   for the DD_Symbolic_Name is not unique, then the iSNS server SHALL
   reject the attempted DD registration with a status code of 3 (Invalid
   Registration).

   When creating a new DD, if the DD_Symbolic_Name is not included in
   the Operating Attributes, or if it is included with a zero-length
   TLV, then the iSNS server SHALL provide a unique DD_Symbolic_Name
   value for the created DD.  The assigned DD_Symbolic_Name value SHALL
   be returned in the DDRegRsp message.

   When creating a new DD, if the DD_Features attribute is not included
   in the Operating Attributes, then the iSNS server SHALL assign the
   default value.  The default value for DD_Features is 0.

   DD Member iSCSI Name, DD Member iFCP Node, DD Member Portal IP
   Address, and DD Member TCP/UDP Port Number attributes included in the
   Operating Attributes need not match currently existing iSNS database
   entries.  This allows, for example, a Storage Node to be added to a
   DD even if the Storage Node is not currently registered in the iSNS
   database.  A Storage Node or Portal can thereby be added to a DD at
   the time of the DDs creation, even if the Storage Node or Portal is
   not currently active in the storage network.

   If the Operating Attributes contain a DD Member iSCSI Name value for
   a Storage Node that is currently not registered in the iSNS database,
   then the iSNS server MUST allocate an unused iSCSI Node Index for
   that Storage Node.  The assigned iSCSI Node Index SHALL be returned
   in the DDRegRsp message as the DD Member iSCSI Node Index.  The
   allocated iSCSI Node Index value SHALL be assigned to the Storage
   Node if and when it registers in the iSNS database.

   If the Operating Attributes contain a DD Member Portal IP Addr and DD
   Member Portal TCP/UDP value for a Portal that is not currently
   registered in the iSNS database, then the iSNS server MUST allocate
   an unused Portal Index value for that Portal.  The assigned Portal
   Index value SHALL be returned in the DDRegRsp message as the DD
   Member Portal Index.  The allocated Portal Index value SHALL be
   assigned to the Portal if and when it registers in the iSNS database.

   DD Member iSCSI Node Index and DD Member Portal Index attributes that
   are provided in the Operating Attributes MUST match a corresponding
   iSCSI Node Index or Portal Index of an existing Storage Node or
   Portal entry in the iSNS database.  Furthermore, the DD Member iSCSI
   Node Index and DD Member Portal Index SHALL NOT be used to add
   Storage Nodes or Portals to a DD unless those Storage Nodes or
   Portals are actively registered in the iSNS database.

5.6.5.10.  DD Deregister (DDDereg)

   The DDDereg message type is 0x000A.  This message allows an iSNS
   client to deregister an existing Discovery Domain (DD) and to remove
   members from an existing DD.

   DDs are uniquely identified using DD_IDs.  DD registration attributes
   are described in Section 6.11.

   The DDDereg message PDU Payload contains a Source Attribute, Message
   Key Attribute, and optional Operating Attributes.

   The Message Key Attribute for a DDDereg message is the DD ID for the
   Discovery Domain being removed or having members removed.  If the DD
   ID matches an existing DD and there are no Operating Attributes, then
   the DD SHALL be removed and a success Status Code returned.  Any
   existing members of that DD SHALL remain in the iSNS database without
   membership in the just-removed DD.

   If the DD ID matches an existing DD and there are Operating
   Attributes matching DD members, then the DD members identified by the
   Operating Attributes SHALL be removed from the DD and a successful
   Status Code returned.

   If a DD Member iSCSI Name identified in the Operating Attributes
   contains an iSCSI Name for a Storage Node that is not currently
   registered in the iSNS database or contained in another DD, then the
   association between that Storage Node and its pre-assigned iSCSI Node
   Index SHALL be removed.  The pre-assigned iSCSI Node Index value no
   longer has an association to a specific iSCSI Name and can now be
   re-assigned.

   If a DD Member Portal IP Address and DD Member TCP/UDP Port
   identified in the Operating Attributes reference a Portal that is not
   currently registered in the iSNS database or contained in another DD,
   then the association between that Portal and its pre-assigned Portal
   Index SHALL be removed.  The pre-assigned Portal Index value can now
   be reassigned.

   The attempted deregistration of non-existent DD entries SHALL not be
   considered an error.

5.6.5.11.  DDS Register (DDSReg)

   The DDSReg message type is 0x000B.  This message allows an iSNS
   client to create a new Discovery Domain Set (DDS), to update an
   existing DDS Symbolic Name and/or DDS Status, or to add DDS members.

   DDSs are uniquely defined using DDS_IDs.  DDS registration attributes
   are described in Section 6.11.1.

   The DDSReg message PDU Payload contains the Source Attribute and,
   optionally, Message Key and Operating Attributes.

   The Message Key, if used, contains the DDS_ID of the Discover Domain
   Set to be registered or modified.  If the Message Key contains a
   DDS_ID of an existing DDS entry in the iSNS database, then the DDSReg
   message SHALL attempt to update the existing entry.  If the DDS_ID in
   the Message Key (if used) does not match an existing DDS entry, then
   the iSNS server SHALL reject the DDSReg message with a status code of
   3 (Invalid Registration).  If the DDS_ID is included in both the
   Message Key and Operating Attributes, then the DDS_ID value in the
   Message Key MUST be the same as the DDS_ID value in the Operating
   Attributes.

   A DDSReg message with no Message Key SHALL result in the attempted
   creation of a new Discovery Domain Set (DDS).  If the DDS_ID
   attribute (with non-zero length) is included among the Operating
   Attributes in the DDSReg message, then the new Discovery Domain Set
   SHALL be assigned the value contained in that DDS_ID attribute.
   Otherwise, if the DDS_ID attribute is not contained among the
   Operating Attributes of the DDSReg message, or if the DDS_ID is an

   operating attribute with a TLV length of 0, then the iSNS server
   SHALL assign a DDS_ID value.  The assigned DDS_ID value is then
   returned in the DDSReg Response message.  The Operating Attributes
   can also contain the DDS_Symbolic_Name, the DDS Status, and the
   DD_IDs of Discovery Domains to be added to the DDS.

   When creating a new DDS, if the DDS Symbolic Name is included in the
   Operating Attributes and its value is unique (i.e., it does not match
   the registered DDS Symbolic Name for another DDS), then the value
   SHALL be stored in the iSNS database as the DDS Symbolic Name for
   that DDS.  If the value for the DDS Symbolic Name is not unique, then
   the iSNS server SHALL reject the attempted DDS registration with a
   status code of 3 (Invalid Registration).

   When creating a new DDS, if the DDS Symbolic Name is not included in
   the Operating Attributes, or if it is included with a zero-length
   TLV, then the iSNS server SHALL provide a unique DDS Symbolic Name
   value for the created DDS.  The assigned DDS Symbolic Name value
   SHALL be returned in the DDSRegRsp message.

   This message SHALL add any DD_IDs listed as Operating Attributes to
   the Discovery Domain Set specified by the DDS_ID Message Key
   Attribute.  In addition, if the DDS_Symbolic_Name is an operating
   attribute and the value is unique, then it SHALL be stored in the
   iSNS database as the DDS_Symbolic_Name for the specified Discovery
   Domain Set.

   If a DD_ID listed in the Operating Attributes does not match an
   existing DD, then a new DD using the DD_ID SHALL be created.  In this
   case for the new DD, the iSNS server SHALL assign a unique value for
   the DD Symbolic Name and SHALL set the DD Features attribute to the
   default value of 0.  These assigned values SHALL be returned in the
   DDSRegRsp message.

5.6.5.12.  DDS Deregister (DDSDereg)

   The DDSDereg message type is 0x000C.  This message allows an iSNS
   client to deregister an existing Discovery Domain Set (DDS) or to
   remove some DDs from an existing DDS.

   The DDSDereg message PDU Payload contains a Source Attribute, a
   Message Key Attribute, and optional Operating Attributes.

   The Message Key Attribute for a DDSDereg message is the DDS ID for
   the DDS being removed or having members removed.  If the DDS ID
   matches an existing DDS and there are no Operating Attributes, then

   the DDS SHALL be removed and a success Status Code returned.  Any
   existing members of that DDS SHALL remain in the iSNS database
   without membership in the just-removed DDS.

   If the DDS ID matches an existing DDS, and there are Operating
   Attributes matching DDS members, then the DDS members SHALL be
   removed from the DDS and a success Status Code returned.

   The attempted deregistration of non-existent DDS entries SHALL not be
   considered an error.

5.6.5.13.  Entity Status Inquiry (ESI)

   The ESI message type is 0x000D.  This message is sent by the iSNS
   server, and is used to verify that an iSNS client Portal is reachable
   and available.  The ESI message is sent to the ESI UDP port provided
   during registration, or to the TCP connection used for ESI
   registration, depending on which communication type that is being
   used.

   The ESI message PDU Payload contains the following attributes in TLV
   format and in the order listed: the current iSNS timestamp, the EID,
   the Portal IP Address, and the Portal TCP/UDP Port.  The format of
   this message is shown below:

          +----------------------------------------+
          |               Timestamp                |
          +----------------------------------------+
          |               Entity_ID                |
          +----------------------------------------+
          |           Portal IP Address            |
          +----------------------------------------+
          |          Portal TCP/UDP Port           |
          +----------------------------------------+

   The ESI response message PDU Payload contains a status code, followed
   by the Attributes from the original ESI message.

   If the Portal fails to respond to an administratively-determined
   number of consecutive ESI messages, then the iSNS server SHALL remove
   that Portal from the iSNS database.  If there are no other remaining
   ESI-monitored Portals for the associated Network Entity, then the
   Network Entity SHALL also be removed.  The appropriate State Change
   Notifications, if any, SHALL be triggered.

5.6.5.14.  Name Service Heartbeat (Heartbeat)

   This message, if used, is only sent by the active iSNS server.  It
   allows iSNS clients and backup servers listening to a broadcast or
   multicast address to discover the IP address of the primary and
   backup iSNS servers.  It also allows concerned parties to monitor the
   health and status of the primary iSNS server.

   This message is NOT in TLV format.  There is no response message to
   the Name Service Heartbeat.

          MSb                                            LSb
          0                                               31
          +------------------------------------------------+
          |            Active Server IP-Address            | 16 Bytes
          +------------------------------------------------+
          |     iSNS TCP Port     |      iSNS UDP Port     | 4 Bytes
          +------------------------------------------------+
          |                   Interval                     | 4 Bytes
          +------------------------------------------------+
          |                    Counter                     | 4 Bytes
          +------------------------------------------------+
          |      RESERVED         |    Backup Servers      | 4 Bytes
          +------------------------------------------------+
          |    Primary Backup Server IP Address(if any)    | 16 Bytes
          +------------------------------------------------+
          |Backup TCP Port(if any)|Backup UDP Port(if any) | 4 Bytes
          +------------------------------------------------+
          |      2nd Backup Server IP Address(if any)      | 16 Bytes
          +------------------------------------------------+
          |Backup TCP Port(if any)|Backup UDP Port(if any) | 4 Bytes
          +------------------------------------------------+
          |                     . . .                      |
          +------------------------------------------------+
          |                VENDOR SPECIFIC                 |
          +------------------------------------------------+

   The heartbeat PDU Payload contains the following:

   Active Server IP Address: the IP Address of the active iSNS server in
                    IPv6 format.  When this field contains an IPv4
                    value, it is stored as an IPv4-mapped IPv6 address.
                    That is, the most significant 10 bytes are set to
                    0x00, with the next two bytes set to 0xFFFF
                    [RFC2373].  When this field contains an IPv6 value,
                    the entire 16-byte field is used.

   Active TCP Port: the TCP Port of the server currently in use.

   Active UDP Port: the UDP Port of the server currently in use,
                    otherwise 0.

   Interval:        the interval, in seconds, of the heartbeat.

   Counter:         a count that begins at 0 when this server becomes
                    active.  The count increments by one for each
                    heartbeat sent since this server became active.

   Backup Servers:  the number of iSNS backup servers.  The IP address,
                    TCP Port, and UDP Port of each iSNS backup server
                    follow this field.  Note that if backup servers are
                    used, then the active iSNS server SHOULD be among
                    the list of backup servers.

   The content of the remainder of this message after the list of backup
   servers is vendor-specific.  Vendors may use additional fields to
   coordinate between multiple iSNS servers, and/or to identify vendor-
   specific features.

5.6.5.15.  Request FC_DOMAIN_ID (RqstDomId)

   The RqstDomId message type is 0x0011.  This message is used for iFCP
   Transparent Mode to allocate non-overlapping FC_DOMAIN_ID values
   between 1 and 239.  The iSNS server becomes the address assignment
   authority for the entire iFCP fabric.  To obtain multiple
   FC_DOMAIN_ID values, this request must be repeated to the iSNS server
   multiple times.  iSNS clients that acquire FC_DOMAIN_ID values from
   an iSNS server MUST register for ESI monitoring from that iSNS
   server.

   The RqstDomId PDU Payload contains three TLV attributes in the
   following order: the requesting Switch Name (WWN) as the Source
   Attribute, the Virtual_Fabric_ID as the Message Key Attribute, and
   Preferred ID as the operating attribute.  The Virtual_Fabric_ID is a
   string identifying the domain space for which the iSNS server SHALL
   allocate non-overlapping integer FC_DOMAIN_ID values between 1 and
   239.  The Preferred_ID is the nominal FC_DOMAIN_ID value requested by
   the iSNS client.  If the Preferred_ID value is available and has not
   already been allocated for the Virtual_Fabric_ID specified in the
   message, the iSNS server SHALL return the requested Preferred_ID
   value as the Assigned_ID to the requesting client.

   The RqstDomId response contains a Status Code, and the TLV attribute
   Assigned ID, which contains the integer value in the space requested.
   If no further unallocated values are available from this space, the
   iSNS server SHALL respond with the Status Code 18 "FC_DOMAIN_ID Not
   Available".

   Once a FC_DOMAIN_ID value has been allocated to an iSNS client by the
   iSNS server for a given Virtual_Fabric_ID, that FC_DOMAIN_ID value
   SHALL NOT be reused until it has been deallocated, or until ESI
   monitoring detects that the iSNS client no longer exists on the
   network and objects for that client are removed from the iSNS
   database.

   The iSNS server and client SHALL use TCP to transmit and receive
   RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.6.5.16.  Release FC_DOMAIN_ID (RlseDomId)

   The RlseDomId message type is 0x0012.  This message may be used by
   iFCP Transparent Mode to release integer identifier values used to
   assign 3-byte Fibre Channel PORT_ID values.

   The RlseDomId message contains three TLV attributes in the following
   order: the requesting EID as the Source Attribute, the
   Virtual_Fabric_ID as the Message Key Attribute, and Assigned_ID as
   the operating attribute.  Upon receiving the RlseDomId message, the
   iSNS server SHALL deallocate the FC_DOMAIN_ID value contained in the
   Assigned_ID attribute for the Virtual_Fabric_ID attribute specified.
   Upon deallocation, that FC_DOMAIN_ID value can then be requested by
   and assigned to a different iSNS client.

   The iSNS server and client SHALL use TCP to transmit and receive
   RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.6.5.17.  Get FC_DOMAIN_IDs (GetDomId)

   The GetDomId message type is 0x0013.  This message is used to learn
   the currently-allocated FC_DOMAIN_ID values for a given
   Virtual_Fabric_ID.

   The GetDomId message PDU Payload contains a Source Attribute and
   Message Key Attribute.

   The Message Key Attribute for the GetDomId message is the
   Virtual_Fabric_ID.  The response to this message returns all the
   FC_DOMAIN_ID values that have been allocated for the
   Virtual_Fabric_ID specified.

5.7.  Messages

   The iSNSP response message PDU Payloads contain a Status Code,
   followed by a list of attributes, and have the following format:

          MSb                                    LSb
          0                                       31
          +----------------------------------------+
          |          4-byte STATUS CODE            |
          +----------------------------------------+
          |  Message Key Attribute[1] (if present) |
          +----------------------------------------+
          |  Message Key Attribute[2] (if present) |
          +----------------------------------------+
          |                 . . .                  |
          +----------------------------------------+
          |  - Delimiter Attribute - (if present)  |
          +----------------------------------------+
          |   Operating Attribute[1] (if present)  |
          +----------------------------------------+
          |   Operating Attribute[2] (if present)  |
          +----------------------------------------+
          |   Operating Attribute[3] (if present)  |
          +----------------------------------------+
          |                 . . .                  |
          +----------------------------------------+

   The iSNSP Response messages SHALL be sent to the iSNS Client IP
   Address and the originating TCP/UDP Port that was used for the
   associated registration and query message.

5.7.1.  Status Code

   The first field in an iSNSP response message PDU Payload is the
   Status Code for the operation that was performed.  The Status Code
   encoding is defined in Section 5.4.

5.7.2.  Message Key Attributes in Response

   Depending on the specific iSNSP request, the response message MAY
   contain Message Key Attributes.  Message Key Attributes generally
   contain the interesting key attributes that are affected by the
   operation specified in the original iSNS registration or query
   message.

5.7.3.  Delimiter Attribute in Response

   The Delimiter Attribute separates the key and Operating Attributes in
   a response message, if they exist.  The Delimiter Attribute has a tag
   value of 0 and a length value of 0.  The Delimiter Attribute is
   effectively 8 bytes long: a 4-byte tag containing 0x00000000, and a 4
   Byte length field containing 0x00000000.

5.7.4.  Operating Attributes in Response

   The Operating Attributes in a response are the results related to the
   iSNS registration or query operation being performed.  Some response
   messages will not have Operating Attributes.

5.7.5.  Registration and Query Response Message Types

   The following sections describe each query and message type.

5.7.5.1.  Device Attribute Registration Response (DevAttrRegRsp)

   The DevAttrRegRsp message type is 0x8001.  The DevAttrRegRsp message
   contains the results for the DevAttrReg message with the same
   TRANSACTION ID.

   The Message Key in the DevAttrRegRsp message SHALL return the Message
   Key in the original registration message.  If the iSNS server
   assigned the Entity Identifier for a Network Entity, then the Message
   Key Attribute field SHALL contain the assigned Entity Identifier.

   The Operating Attributes of the DevAttrRegRsp message SHALL contain
   the affected object's key and non-key attributes that have been
   explicitly modified or created by the original DevAttrReg message.
   Among the Operating Attributes, each modified or added non-key
   attribute SHALL be listed after its key attribute(s) in the
   DevAttrRegRsp message.  Implicitly registered attributes MUST NOT be
   returned in the DevAttrRegRsp message.  Implicitly registered
   attributes are those that are assigned a fixed default value or
   secondary index value by the iSNS server.

   Implicitly registered PG objects (i.e., PG objects that are not
   explicitly included in the registration or replace message) MUST NOT
   have their key or non-key attributes returned in the DevAttrRegRsp
   message.  However, explicitly registered PG objects (i.e., those with
   PGT values that are explicitly included in the registration or
   replace message) SHALL have their PGT values returned in the
   DevAttrRegRsp message.

   For example, three Portals are registered in the original DevAttrReg
   request message.  Due to lack of resources, the iSNS server needs to
   modify the registered ESI Interval value of one of those Portals.  To
   accomplish this, the iSNS server returns the key attributes
   identifying the Portal, followed by the non-key modified ESI Interval
   attribute value, as Operating Attributes of the corresponding
   DevAttrRegRsp message.

   If the iSNS server rejects a registration due to invalid attribute
   values or types, then the indicated status code SHALL be 3 (Invalid
   Registration).  If this occurs, then the iSNS server MAY include the
   list of invalid attributes in the Operating Attributes of the
   DevAttrRsp message.

   Some attributes values (e.g., ESI Interval, Registration Period) in
   the original registration message MAY be modified by the iSNS server.
   This can occur only for a limited set of attribute types, as
   indicated in the table in Section 6.1.  When this occurs, the
   registration SHALL be considered a success (with status code 0), and
   the changed value(s) indicated in the Operating Attributes of the
   DevAttrRsp message.

5.7.5.2.  Device Attribute Query Response (DevAttrQryRsp)

   The DevAttrQryRsp message type is 0x8002.  The DevAttrQryRsp message
   contains the results for the DevAttrQry message with the same
   TRANSACTION ID.

   The Message Key in the DevAttrQryRsp message SHALL return the Message
   Key in the original query message.

   If no Operating Attributes are included in the original query, then
   all Operating Attributes SHALL be returned in the response.

   For a successful query result, the DevAttrQryRsp Operating Attributes
   SHALL contain the results of the original DevAttrQry message.

5.7.5.3.  Device Get Next Response (DevGetNextRsp)

   The DevGetNextRsp message type is 0x8003.  The DevGetNextRsp message
   contains the results for the DevGetNext message with the same
   TRANSACTION ID.

   The Message Key Attribute field returns the object keys for the next
   object after the Message Key Attribute in the original DevGetNext
   message.

   The Operating Attribute field returns the Operating Attributes of the
   next object as requested in the original DevGetNext message.  The
   values of the Operating Attributes are those associated with the
   object identified by the Message Key Attribute field of the
   DevGetNextRsp message.

5.7.5.4.  Deregister Device Response (DevDeregRsp)

   The DevDeregRsp message type is 0x8004.  This message is the response
   to the DevDereg request message.

   This message response does not contain a Message Key, but MAY contain
   Operating Attributes.

   In the event of an error, this response message contains the
   appropriate status code as well as a list of objects from the
   original DevDereg message that were not successfully deregistered
   from the iSNS database.  This list of objects is contained in the
   Operating Attributes of the DevDeregRsp message.  Note that an
   attempted deregistration of a non-existent object does not constitute
   an error, and non-existent entries SHALL not be returned in the
   DevDeregRsp message.

5.7.5.5.  SCN Register Response (SCNRegRsp)

   The SCNRegRsp message type is 0x8005.  This message is the response
   to the SCNReg request message.

   The SCNRegRsp message does not contain any Message Key or Operating
   Attributes.

5.7.5.6.  SCN Deregister Response (SCNDeregRsp)

   The SCNDeregRsp message type is 0x8006.  This message is the response
   to the SCNDereg request message.

   The SCNDeregRsp message does not contain any Message Key or Operating
   Attributes.

5.7.5.7.  SCN Event Response (SCNEventRsp)

   The SCNEventRsp message type is 0x8007.  This message is the response
   to the SCNEvent request message.

   The SCNEventRsp message does not contain any Message Key or Operating
   Attributes.

5.7.5.8.  SCN Response (SCNRsp)

   The SCNRsp message type is 0x8008.  This message is sent by an iSNS
   client, and provides confirmation that the SCN message was received
   and processed.

   The SCNRsp response contains the SCN Destination Attribute
   representing the Node identifier that received the SCN.

5.7.5.9.  DD Register Response (DDRegRsp)

   The DDRegRsp message type is 0x8009.  This message is the response to
   the DDReg request message.

   The Message Key in the DDRegRsp message SHALL return the Message Key
   in the original query message.  If the original DDReg message did not
   have a Message Key, then the DDRegRsp message SHALL not have a
   Message Key.

   If the DDReg operation is successful, the DD ID of the DD created or
   updated SHALL be returned as an operating attribute of the message.

   If the DD Symbolic Name attribute or DD Features attribute was
   assigned or updated during the DDReg operation, then any new values
   SHALL be returned as an operating attribute of the DDRegRsp message.

   If the iSNS server rejects a DDReg due to invalid attribute values or
   types, then the indicated status code SHALL be 3 (Invalid
   Registration).  If this occurs, then the iSNS server MAY include the
   list of invalid attributes in the Operating Attributes of the
   DDRegRsp message.

5.7.5.10.  DD Deregister Response (DDDeregRsp)

   The DDDeregRsp message type is 0x800A.  This message is the response
   to the DDDereg request message.

   The DDDeregRsp message does not contain any Message Key or Operating
   Attributes.

5.7.5.11.  DDS Register Response (DDSRegRsp)

   The DDSRegRsp message type is 0x800B.  This message is the response
   to the DDSReg request message.

   The Message Key in the DDSRegRsp message SHALL contain the Message
   Key of the original DDSReg message.  If the original DDSReg message
   did not have a Message Key, then the DDSRegRsp message SHALL NOT have
   a Message Key.

   If the DDSReg operation is successful, the DDS ID of the DDS created
   or updated SHALL be returned as an operating attribute of the
   message.

   If the DDS Symbolic Name attribute or DDS Status attribute was
   assigned or updated during the DDSRegRsp operation, then any new
   values SHALL be returned as an operating attribute of the DDSRegRsp
   message.

   If the iSNS server rejects a DDSReg due to invalid attribute values
   or types, then the indicated status code SHALL be 3 (Invalid
   Registration).  If this occurs, then the iSNS server MAY include the
   list of invalid attributes in the Operating Attributes of the
   DDSRegRsp message.

5.7.5.12.  DDS Deregister Response (DDSDeregRsp)

   The DDSDeregRsp message type is 0x800C.  This message is the response
   to the DDSDereg request message.

   The DDSDeregRsp message does not contain any Message Key or Operating
   Attributes.

5.7.5.13.  Entity Status Inquiry Response (ESIRsp)

   The ESIRsp message type is 0x800D.  This message is sent by an iSNS
   client and provides confirmation that the ESI message was received
   and processed.

   The ESIRsp response message PDU Payload contains the attributes from
   the original ESI message.  These attributes represent the Portal that
   is responding to the ESI.  The ESIRsp Attributes are in the order
   they were provided in the original ESI message.

   Upon receiving the ESIRsp from the iSNS client, the iSNS server SHALL
   update the timestamp attribute for that Network Entity and Portal.

5.7.5.14.  Request FC_DOMAIN_ID Response (RqstDomIdRsp)

   The RqstDomIdRsp message type is 0x8011.  This message provides the
   response for RqstDomId.

   The RqstDomId response contains a Status Code and the TLV attribute
   Assigned ID, which contains the integer value in the space requested.
   If no further unallocated values are available from this space, the
   iSNS server SHALL respond with the Status Code 19 "FC_DOMAIN_ID Not
   Available".

   Once a FC_DOMAIN_ID value is allocated by the iSNS server, it SHALL
   NOT be reused until it has been deallocated by the iSNS client to
   which the value was assigned, or until the ESI message detects that
   the iSNS client no longer exists on the network.

   The iSNS server and client SHALL use TCP to transmit and receive
   RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.7.5.15.  Release FC_DOMAIN_ID Response (RlseDomIdRsp)

   The RlseDomIdRsp message type is 0x8012.  This message provides the
   response for RlseDomId.  The response contains an Error indicating
   whether the request was successful.  If the Assigned_ID value in the
   original RlseDomId message is not allocated, then the iSNS server
   SHALL respond with this message using the Status Code 20
   "FC_DOMAIN_ID Not Allocated".

   The iSNS server and client SHALL use TCP to transmit and receive
   RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.7.5.16.  Get FC_DOMAIN_IDs Response (GetDomIdRsp)

   The GetDomIdRsp message type is 0x8013.  This message is used to
   determine which FC_DOMAIN_ID values have been allocated for the
   Virtual_Fabric_ID specified in the original GetDomId request message.

   The GetDomId response message PDU Payload contains a Status Code
   indicating whether the request was successful, and a list of the
   Assigned IDs from the space requested.  The Assigned_ID attributes
   are listed in TLV format.

5.8.  Vendor-Specific Messages

   Vendor-specific iSNSP messages have a functional ID of between 0x0100
   and 0x01FF, whereas vendor-specific responses have a functional ID of
   between 0x8100 and 0x81FF.  The first Message Key Attribute in a

   vendor-specific message SHALL be the company OUI (tag=256)
   identifying the original creator of the proprietary iSNSP message.
   The contents of the remainder of the message are vendor-specific.

6.  iSNS Attributes

   Attributes can be stored in the iSNS server using iSNSP registration
   messages, and they can be retrieved using iSNSP query messages.
   Unless otherwise indicated, these attributes are supplied by iSNS
   clients using iSNSP registration messages.

6.1.  iSNS Attribute Summary

   The complete registry of iSNS attributes is maintained by IANA, and
   the following table summarizes the initial set of iSNS attributes
   available at the time of publication of this document.

   Attributes               Length   Tag   Reg Key   Query Key
   ----------               ------   ---   -------   ---------
   Delimiter                 0        0      N/A        N/A
   Entity Identifier (EID) 4-256      1       1     1|2|16&17|32|64
   Entity Protocol           4        2       1     1|2|16&17|32|64
   Management IP Address     16       3       1     1|2|16&17|32|64
   Timestamp                 8        4      --     1|2|16&17|32|64
   Protocol Version Range    4        5       1     1|2|16&17|32|64
   Registration Period       4        6       1     1|2|16&17|32|64
   Entity Index              4        7       1     1|2|16&17|32|64
   Entity Next Index         4        8      --     1|2|16&17|32|64
   Entity ISAKMP Phase-1    var       11      1     1|2|16&17|32|64
   Entity Certificate       var       12      1     1|2|16&17|32|64
   Portal IP Address         16       16      1     1|16&17|32|64
   Portal TCP/UDP Port       4        17      1     1|16&17|32|64
   Portal Symbolic Name    4-256      18    16&17   1|16&17|32|64
   ESI Interval              4        19    16&17   1|16&17|32|64
   ESI Port                  4        20    16&17   1|16&17|32|64
   Portal Index              4        22    16&17   1|16&17|32|64
   SCN Port                  4        23    16&17   1|16&17|32|64
   Portal Next Index         4        24     --     1|16&17|32|64
   Portal Security Bitmap    4        27    16&17   1|16&17|32|64
   Portal ISAKMP Phase-1    var       28    16&17   1|16&17|32|64
   Portal ISAKMP Phase-2    var       29    16&17   1|16&17|32|64
   Portal Certificate       var       31    16&17   1|16&17|32|64
   iSCSI Name              4-224      32      1     1|16&17|32|33
   iSCSI Node Type           4        33     32     1|16&17|32
   iSCSI Alias             4-256      34     32     1|16&17|32
   iSCSI SCN Bitmap          4        35     32     1|16&17|32
   iSCSI Node Index          4        36     32     1|16&17|32
   WWNN Token                8        37     32     1|16&17|32

   iSCSI Node Next Index     4        38     --     1|16&17|32
   iSCSI AuthMethod         var       42     32     1|16&17|32
   PG iSCSI Name           4-224      48   32|16&17 1|16&17|32|52
   PG Portal IP Addr        16        49   32|16&17 1|16&17|32|52
   PG Portal TCP/UDP Port    4        50   32|16&17 1|16&17|32|52
   PG Tag (PGT)              4        51   32|16&17 1|16&17|32|52
   PG Index                  4        52   32|16&17 1|16&17|32|52
   PG Next Index             4        53     --     1|16&17|32|52
   FC Port Name WWPN         8        64     1     1|16&17|64|66|96|128
   Port ID                   4        65     64     1|16&17|64
   FC Port Type              4        66     64     1|16&17|64
   Symbolic Port Name      4-256      67     64     1|16&17|64
   Fabric Port Name          8        68     64     1|16&17|64
   Hard Address              4        69     64     1|16&17|64
   Port IP-Address          16        70     64     1|16&17|64
   Class of Service          4        71     64     1|16&17|64
   FC-4 Types               32        72     64     1|16&17|64
   FC-4 Descriptor         4-256      73     64     1|16&17|64
   FC-4 Features            128       74     64     1|16&17|64
   iFCP SCN bitmap           4        75     64     1|16&17|64
   Port Role                 4        76     64     1|16&17|64
   Permanent Port Name       8        77     --     1|16&17|64
   FC-4 Type Code            4        95     --     1|16&17|64
   FC Node Name WWNN         8        96     64     1|16&17|64|96
   Symbolic Node Name      4-256      97     96     64|96
   Node IP-Address           16       98     96     64|96
   Node IPA                  8        99     96     64|96
   Proxy iSCSI Name        4-256     101     96     64|96
   Switch Name               8       128     128    128
   Preferred ID              4       129     128    128
   Assigned ID               4       130     128    128
   Virtual_Fabric_ID       4-256     131     128    128
   iSNS Server Vendor OUI    4       256     --     SOURCE Attribute
   Vendor-Spec iSNS Srvr          257-384    --     SOURCE Attribute
   Vendor-Spec Entity             385-512     1     1|2|16&17|32|64
   Vendor-Spec Portal             513-640   16&17   1|16&17|32|64
   Vendor-Spec iSCSI Node         641-768    32     16&17|32
   Vendor-Spec FC Port Name       769-896    64     1|16&17|64
   Vendor-Spec FC Node Name       897-1024   96     64|96
   Vendor-Specific DDS           1025-1280   2049   2049
   Vendor-Specific DD            1281-1536   2065   2065
   Other Vendor-Specific         1537-2048
   DD_Set ID                 4      2049     2049   1|32|64|2049|2065
   DD_Set Sym Name         4-256    2050     2049   2049
   DD_Set Status             4      2051     2049   2049
   DD_Set_Next_ID            4      2052     --     2049
   DD_ID                     4      2065     2049   1|32|64|2049|2065
   DD_Symbolic Name        4-256    2066     2065   2065

   DD_Member iSCSI Index     4      2067     2065   2065
   DD_Member iSCSI Name    4-224    2068     2065   2065
   DD_Member FC Port Name    8      2069     2065   2065
   DD_Member Portal Index    4      2070     2065   2065
   DD_Member Portal IP Addr 16      2071     2065   2065
   DD_Member Portal TCP/UDP  4      2072     2065   2065
   DD_Features               4      2078     2065   2065
   DD_ID Next ID             4      2079     --     2065

   The following are descriptions of the columns used in the above
   table:

   Length:    indicates the attribute length in bytes used for the TLV
              format.  Variable-length identifiers are NULL-terminated
              and 4-byte aligned (NULLs are included in the length).

   Tag:       the IANA-assigned integer tag value used to identify the
              attribute.  All undefined tag values are reserved.

   Reg Key:   indicates the tag values for the object key in DevAttrReg
              messages for registering a new attribute value in the
              database.  These tags represent attributes defined as
              object keys in Section 4.

   Query Key: indicates the possible tag values for the Message Key and
              object key that are used in the DevAttrQry messages for
              retrieving a stored value from the iSNS database.

   The following is a summary of iSNS attribute tag values available for
   future allocation by IANA at the time of publication:

   Tag Values           Reg Key          Query Key
   ----------           -------          ---------
   9-10, 13-15          1                1|2|16&17|32|64
   21, 25-26, 30        16&17            1|16&17|32|64
   39-41, 44-47         32               1|16&17|32
   54-63                32|16&17         1|16&17|32|52
   78-82, 85-94         64               1|16&17|64
   102-127              96               64|96
   132-255              --               SOURCE Attribute
   2053-2064            2049             2049
   2073-2077            2065             2065
   2080-65535           To be assigned   To be assigned

   Registration and query keys for attributes with tags in the range
   2080 to 65535 are to be documented in the RFC introducing the new
   iSNS attributes.  IANA will maintain registration of these values as
   required by the new RFC.

   New iSNS attributes with any of the above tag values MAY also be
   designated as "read-only" attributes.  The new RFC introducing these
   attributes as "read-only" SHALL document them as such, and IANA will
   record their corresponding Registration Keys (Reg Keys) as "--".

6.2.  Entity Identifier-Keyed Attributes

   The following attributes are stored in the iSNS server using the
   Entity Identifier attribute as the key.

6.2.1.  Entity Identifier (EID)

   The Entity Identifier (EID) is variable-length UTF-8 encoded NULL-
   terminated text-based description for a Network Entity.  This key
   attribute uniquely identifies each Network Entity registered in the
   iSNS server.  The attribute length varies from 4 to 256 bytes
   (including the NULL termination), and is a unique value within the
   iSNS server.

   If the iSNS client does not provide an EID during registration, the
   iSNS server SHALL generate one that is unique within the iSNS
   database.  If an EID is to be generated, then the EID attribute value
   in the registration message SHALL be empty (0 length).  The generated
   EID SHALL be returned in the registration response.

   In environments where the iSNS server is integrated with a DNS
   infrastructure, the Entity Identifier may be used to store the Fully
   Qualified Domain Name (FQDN) of the iSCSI or iFCP device.  FQDNs of
   greater than 255 bytes MUST NOT be used.

   If FQDNs are not used, the iSNS server can be used to generate EIDs.
   EIDs generated by the iSNS server MUST begin with the string "isns:".
   iSNS clients MUST NOT generate and register EIDs beginning with the
   string "isns:".

   This field MUST be normalized according to the nameprep template
   [NAMEPREP] before it is stored in the iSNS database.

6.2.2.  Entity Protocol

   The Entity Protocol is a required 4-byte integer attribute that
   indicates the block storage protocol used by the registered NETWORK
   ENTITY.  Values used for this attribute are assigned and maintained
   by IANA.  The initial set of protocols supported by iSNS is as
   follows:

          Value          Entity Protocol Type
          -----          --------------------
           1             No Protocol
           2             iSCSI
           3             iFCP
           All others    To be assigned by IANA

   'No Protocol' is used to indicate that the Network Entity does not
   support an IP block storage protocol.  A Control Node or monitoring
   Node would likely (but not necessarily) use this value.

   This attribute is required during initial registration of the Network
   Entity.

6.2.3.  Management IP Address

   This field contains the IP Address that may be used to manage the
   Network Entity and all Storage Nodes contained therein via the iSNS
   MIB [iSNSMIB].  Some implementations may also use this IP address to
   support vendor-specific proprietary management protocols.  The
   Management IP Address is a 16-byte field that may contain an IPv4 or
   IPv6 address.  When this field contains an IPv4 value, it is stored
   as an IPv4-mapped IPv6 address.  That is, the most significant 10
   bytes are set to 0x00, with the next two bytes set to 0xFFFF
   [RFC2373].  When this field contains an IPv6 value, the entire 16-
   byte field is used.  If this field is not set, then in-band
   management through the IP address of one of the Portals of the
   Network Entity is assumed.

6.2.4.  Entity Registration Timestamp

   This field indicates the most recent time when the Network Entity
   registration occurred or when an associated object attribute was
   updated or queried by the iSNS client registering the Network Entity.
   The time format is, in seconds, the update period since the standard
   base time of 00:00:00 GMT on January 1, 1970.  This field cannot be
   explicitly registered.  This timestamp TLV format is also used in the
   SCN and ESI messages.

6.2.5.  Protocol Version Range

   This field contains the minimum and maximum version of the block
   storage protocol supported by the Network Entity.  The most
   significant two bytes contain the maximum version supported, and the
   least significant two bytes contain the minimum version supported.
   If a range is not registered, then the Network Entity is assumed to

   support all versions of the protocol.  The value 0xffff is a wildcard
   that indicates no minimum or maximum.  If the Network Entity does not
   support a protocol, then this field SHALL be set to 0.

6.2.6.  Registration Period

   This 4-byte unsigned integer field indicates the maximum period, in
   seconds, that the registration SHALL be maintained by the server
   without receipt of an iSNS message from the iSNS client that
   registered the Network Entity.  Entities that are not registered for
   ESI monitoring MUST have a non-zero Registration Period.  If a
   Registration Period is not requested by the iSNS client and Entity
   Status Inquiry (ESI) messages are not enabled for that client, then
   the Registration Period SHALL be set to a non-zero value by the iSNS
   server.  This implementation-specific value for the Registration
   Period SHALL be returned in the registration response to the iSNS
   client.  The Registration Period may be set to zero, indicating its
   non-use, only if ESI messages are enabled for that Network Entity.

   The registration SHALL be removed from the iSNS database if an iSNS
   Protocol message is not received from the iSNS client before the
   registration period has expired.  Receipt of any iSNS Protocol
   message from the iSNS client automatically refreshes the Entity
   Registration Period and Entity Registration Timestamp.  To prevent a
   registration from expiring, the iSNS client should send an iSNS
   Protocol message to the iSNS server at intervals shorter than the
   registration period.  Such a message can be as simple as a query for
   one of its own attributes, using its associated iSCSI Name or FC Port
   Name WWPN as the Source attribute.

   For an iSNS client that is supporting a Network Entity with multiple
   Storage Node objects, receipt of an iSNS message from any Storage
   Node of that Network Entity is sufficient to refresh the registration
   for all Storage Node objects of the Network Entity.

   If ESI support is requested as part of a Portal registration, the ESI
   Response message received from the iSNS client by the iSNS server
   SHALL refresh the registration.

6.2.7.  Entity Index

   The Entity Index is an unsigned non-zero integer value that uniquely
   identifies each Network Entity registered in the iSNS server.  Upon
   initial registration of a Network Entity, the iSNS server assigns an
   unused value for the Entity Index.  Each Network Entity in the iSNS
   database MUST be assigned a value for the Entity Index that is not

   assigned to any other Network Entity.  Furthermore, Entity Index
   values for recently deregistered Network Entities SHOULD NOT be
   reused in the short term.

   The Entity Index MAY be used to represent the Network Entity in
   situations when the Entity Identifier is too long or otherwise
   inappropriate.  An example of this is when SNMP is used for
   management, as described in Section 2.10.

6.2.8.  Entity Next Index

   This is a virtual attribute containing a 4-byte integer value that
   indicates the next available (i.e., unused) Entity Index value.  This
   attribute may only be queried; the iSNS server SHALL return an error
   code of 3 (Invalid Registration) to any client that attempts to
   register a value for this attribute.  A Message Key is not required
   when exclusively querying for this attribute.

   The Entity Next Index MAY be used by an SNMP client to create an
   entry in the iSNS server.  SNMP requirements are described in Section
   2.10.

6.2.9.  Entity ISAKMP Phase-1 Proposals

   This field contains the IKE Phase-1 proposal, listing in decreasing
   order of preference the protection suites acceptable to protect all
   IKE Phase-2 messages sent and received by the Network Entity.  This
   includes Phase-2 SAs from the iSNS client to the iSNS server as well
   as to peer iFCP and/or iSCSI devices.  This attribute contains the SA
   payload, proposal payload(s), and transform payload(s) in the ISAKMP
   format defined in [RFC2408].

   This field should be used if the implementer wishes to define a
   single phase-1 SA security configuration used to protect all phase-2
   IKE traffic.  If the implementer desires to have a different phase-1
   SA security configuration to protect each Portal interface, then the
   Portal Phase-1 Proposal (Section 6.3.10) should be used.

6.2.10.  Entity Certificate

   This attribute contains one or more X.509 certificates that are bound
   to the Network Entity.  This certificate is uploaded and registered
   to the iSNS server by clients wishing to allow other clients to
   authenticate themselves and to access the services offered by that
   Network Entity.  The format of the X.509 certificate is found in
   [RFC3280].  This certificate MUST contain a Subject Name with an
   empty sequence and MUST contain a SubjectAltName extension encoded

   with the dNSName type.  The Entity Identifier (Section 6.2.1) of the
   identified Entity MUST be stored in the SubjectAltName field of the
   certificate.

6.3.  Portal-Keyed Attributes

   The following Portal attributes are registered in the iSNS database
   using the combined Portal IP-Address and Portal TCP/UDP Port as the
   key.  Each Portal is associated with one Entity Identifier object
   key.

6.3.1.  Portal IP Address

   This attribute is the IP address of the Portal through which a
   Storage Node can transmit and receive storage data.  The Portal IP
   Address is a 16-byte field that may contain an IPv4 or IPv6 address.
   When this field contains an IPv4 address, it is stored as an IPv4-
   mapped IPv6 address.  That is, the most significant 10 bytes are set
   to 0x00, with the next 2 bytes set to 0xFFFF [RFC2373].  When this
   field contains an IPv6 address, the entire 16-byte field is used.
   The Portal IP Address and the Portal TCP/UDP Port number (see 6.3.2
   below) are used as a key to identify a Portal uniquely.  It is a
   required attribute for registration of a Portal.

6.3.2.  Portal TCP/UDP Port

   The TCP/UDP port of the Portal through which a Storage Node can
   transmit and receive storage data.  Bits 16 to 31 represents the
   TCP/UDP port number.  Bit 15 represents the port type.  If bit 15 is
   set, then the port type is UDP.  Otherwise it is TCP.  Bits 0 to 14
   are reserved.

   If the field value is 0, then the port number is the implied
   canonical port number and type of the protocol indicated by the
   associated Entity Type.

   The Portal IP Address and the Portal TCP/UDP Port number are used as
   a key to identify a Portal uniquely.  It is a required attribute for
   registration of a Portal.

6.3.3.  Portal Symbolic Name

   A variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 256 bytes.  The Portal Symbolic Name is a user-
   readable description of the Portal entry in the iSNS server.

6.3.4.  Entity Status Inquiry Interval

   This field indicates the requested time, in seconds, between Entity
   Status Inquiry (ESI) messages sent from the iSNS server to this
   Network Entity.  ESI messages can be used to verify that a Portal
   registration continues to be valid.  To request monitoring by the
   iSNS server, an iSNS client registers a non-zero value for this
   Portal attribute using a DevAttrReg message.  The client MUST
   register an ESI Port on at least one of its Portals to receive the
   ESI monitoring.

   If the iSNS server does not receive an expected response to an ESI
   message, it SHALL attempt an administratively configured number of
   re-transmissions of the ESI message.  The ESI Interval period begins
   with the iSNS server's receipt of the last ESI Response.  All re-
   transmissions MUST be sent before twice the ESI Interval period has
   passed.  If no response is received from any of the ESI messages,
   then the Portal SHALL be deregistered.  Note that only Portals that
   have registered a value in their ESI Port field can be deregistered
   in this way.

   If all Portals associated with a Network Entity that have registered
   for ESI messages are deregistered due to non-response, and if no
   registrations have been received from the client for at least two ESI
   Interval periods, then the Network Entity and all associated objects
   (including Storage Nodes) SHALL be deregistered.

   If the iSNS server is unable to support ESI messages or the ESI
   Interval requested, it SHALL either reject the ESI request by
   returning an "ESI Not Available" Status Code or modify the ESI
   Interval attribute by selecting its own suitable value and returning
   that value in the Operating Attributes of the registration response
   message.

   If at any time an iSNS client that is registered for ESI messages has
   not received an ESI message to any of its Portals as expected, then
   the client MAY attempt to query the iSNS server using a DevAttrQry
   message using its Entity_ID as the key.  If the query result is the
   error "no such entry", then the client SHALL close all remaining TCP
   connections to the iSNS server and assume that it is no longer
   registered in the iSNS database.  Such a client MAY attempt re-
   registration.

6.3.5.  ESI Port

   This field contains the TCP or UDP port used for ESI monitoring by
   the iSNS server at the Portal IP Address.  Bits 16 to 31 represent
   the port number.  If bit 15 is set, then the port type is UDP.
   Otherwise, the port is TCP.  Bits 0 to 14 are reserved.

   If the iSNS client registers a valid TCP or UDP port number in this
   field, then the client SHALL allow ESI messages to be received at the
   indicated TCP or UDP port.  If a TCP port is registered and a pre-
   existing TCP connection from that TCP port to the iSNS server does
   not already exist, then the iSNS client SHALL accept new TCP
   connections from the iSNS server at the indicated TCP port.

   The iSNS server SHALL return an error if a Network Entity is
   registered for ESI monitoring and none of the Portals of that Network
   Entity has an entry for the ESI Port field.  If multiple Portals have
   a registered ESI port, then the ESI message may be delivered to any
   one of the indicated Portals.

6.3.6.  Portal Index

   The Portal Index is a 4-byte non-zero integer value that uniquely
   identifies each Portal registered in the iSNS database.  Upon initial
   registration of a Portal, the iSNS server assigns an unused value for
   the Portal Index of that Portal.  Each Portal in the iSNS database
   MUST be assigned a value for the Portal Index that is not assigned to
   any other Portal.  Furthermore, Portal Index values for recently
   deregistered Portals SHOULD NOT be reused in the short term.

   The Portal Index MAY be used to represent a registered Portal in
   situations where the Portal IP-Address and Portal TCP/UDP Port is
   unwieldy to use.  An example of this is when SNMP is used for
   management, as described in Section 2.10.

6.3.7.  SCN Port

   This field contains the TCP or UDP port used by the iSNS client to
   receive SCN messages from the iSNS server.  When a value is
   registered for this attribute, an SCN message may be received on the
   indicated port for any of the Storage Nodes supported by the Portal.
   Bits 16 to 31 contain the port number.  If bit 15 is set, then the
   port type is UDP.  Otherwise, the port type is TCP.  Bits 0 to 14 are
   reserved.

   If the iSNS client registers a valid TCP or UDP port number in this
   field, then the client SHALL allow SCN messages to be received at the
   indicated TCP or UDP port.  If a TCP port is registered and a pre-

   existing TCP connection from that TCP port to the iSNS server does
   not already exist, then the iSNS client SHALL accept new TCP
   connections from the iSNS server at the indicated TCP port.

   The iSNS server SHALL return an error if an SCN registration message
   is received and none of the Portals of the Network Entity has an
   entry for the SCN Port.  If multiple Portals have a registered SCN
   Port, then the SCN SHALL be delivered to any one of the indicated
   Portals of that Network Entity.

6.3.8.  Portal Next Index

   This is a virtual attribute containing a 4-byte integer value that
   indicates the next available (i.e., unused) Portal Index value.  This
   attribute may only be queried; the iSNS server SHALL return an error
   code of 3 (Invalid Registration) to any client that attempts to
   register a value for this attribute.  A Message Key is not required
   when exclusively querying for this attribute.

   The Portal Next Index MAY be used by an SNMP client to create an
   entry in the iSNS server.  SNMP requirements are described in Section
   2.10.

6.3.9.  Portal Security Bitmap

   This 4-byte field contains flags that indicate security attribute
   settings for the Portal.  Bit 31 (Lsb) of this field must be 1
   (enabled) for this field to contain significant information.  If Bit
   31 is enabled, this signifies that the iSNS server can be used to
   store and distribute security policies and settings for iSNS clients
   (i.e., iSCSI devices).  Bit 30 must be 1 for bits 25-29 to contain
   significant information.  All other bits are reserved for non-
   IKE/IPSec security mechanisms to be specified in the future.

   Bit Position        Flag Description
   ------------        ----------------
      25               1 = Tunnel Mode Preferred; 0 = No Preference
      26               1 = Transport Mode Preferred; 0 = No Preference
      27               1 = Perfect Forward Secrecy (PFS) Enabled;
                       0 = PFS Disabled
      28               1 = Aggressive Mode Enabled; 0 = Disabled
      29               1 = Main Mode Enabled; 0 = MM Disabled
      30               1 = IKE/IPSec Enabled; 0 = IKE/IPSec Disabled
      31 (Lsb)         1 = Bitmap VALID; 0 = INVALID
      All others       RESERVED

6.3.10.  Portal ISAKMP Phase-1 Proposals

   This field contains the IKE Phase-1 proposal listing in decreasing
   order of preference of the protection suites acceptable to protect
   all IKE Phase-2 messages sent and received by the Portal.  This
   includes Phase-2 SAs from the iSNS client to the iSNS server as well
   as to peer iFCP and/or iSCSI devices.  This attribute contains the SA
   payload, proposal payload(s), and transform payload(s) in the ISAKMP
   format defined in [RFC2408].

   This field should be used if the implementer wishes to define phase-1
   SA security configuration on a per-Portal basis, as opposed to on a
   per-Network Entity basis.  If the implementer desires to have a
   single phase-1 SA security configuration to protect all phase-2
   traffic regardless of the interface used, then the Entity Phase-1
   Proposal (Section 6.2.9) should be used.

6.3.11.  Portal ISAKMP Phase-2 Proposals

   This field contains the IKE Phase-2 proposal, in ISAKMP format
   [RFC2408], listing in decreasing order of preference the security
   proposals acceptable to protect traffic sent and received by the
   Portal.  This field is used only if bits 31, 30, and 29 of the

   Security Bitmap (see 6.3.9) are enabled.  This attribute contains the
   SA payload, proposal payload(s), and associated transform payload(s)
   in the ISAKMP format defined in [RFC2408].

6.3.12.  Portal Certificate

   This attribute contains one or more X.509 certificates that are a
   credential of the Portal.  This certificate is used to identify and
   authenticate communications to the IP address and TCP/UDP Port
   supported by the Portal.  The format of the X.509 certificate is
   specified in [RFC3280].  This certificate MUST contain a Subject Name
   with an empty sequence and MUST contain a SubjectAltName extension
   encoded with the iPAddress type.  The Portal IP Address (Section
   6.3.1) of the identified Portal SHALL be stored in the SubjectAltName
   field of the certificate.

6.4.  iSCSI Node-Keyed Attributes

   The following attributes are stored in the iSNS database using the
   iSCSI Name attribute as the key.  Each set of Node-Keyed attributes
   is associated with one Entity Identifier object key.

   Although the iSCSI Name key is associated with one Entity Identifier,
   it is unique across the entire iSNS database.

6.4.1.  iSCSI Name

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 224 bytes.  This key attribute is required for
   iSCSI Storage Nodes and is provided by the iSNS client.  The
   registered iSCSI Name MUST conform to the format described in [iSCSI]
   for iSCSI Names.  The maximum size for an iSCSI Name is 223 bytes.
   Including the NULL character and 4-byte alignment (see Section
   5.3.1), the maximum iSCSI Name field size is 224 bytes.

   If an iSCSI Name is registered without an EID key, then a Network
   Entity SHALL be created and an EID assigned.  The assigned EID SHALL
   be returned in the registration response as an operating attribute.

   This field MUST be normalized according to the stringprep template
   [STRINGPREP] before it is stored in the iSNS database.

6.4.2.  iSCSI Node Type

   This required 32-bit field is a bitmap indicating the type of iSCSI
   Storage Node.  The bit positions are defined below.  A set bit (1)
   indicates that the Node has the corresponding characteristics.

          Bit Position    Node Type
          ------------    ---------
           29             Control
           30             Initiator
           31 (Lsb)       Target
           All others     RESERVED

   If the Target bit is set to 1, then the Node represents an iSCSI
   target.  The Target bit MAY be set by iSNS clients using the iSNSP.

   If the Initiator bit is set to 1, then the Node represents an iSCSI
   initiator.  The Initiator bit MAY be set by iSNS clients using the
   iSNSP.

   If the control bit is set to 1, then the Node represents a gateway, a
   management station, a backup iSNS server, or another device that is
   not an initiator or target, but that requires the ability to send and
   receive iSNSP messages, including state change notifications.
   Setting the control bit is an administrative task that MUST be
   performed on the iSNS server; iSNS clients SHALL NOT be allowed to
   change this bit using the iSNSP.

   This field MAY be used by the iSNS server to distinguish among
   permissions by different iSCSI Node types for accessing various iSNS
   functions.  More than one Node Type bit may be simultaneously
   enabled.

6.4.3.  iSCSI Node Alias

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 256 bytes.  The Alias is a user-readable
   description of the Node entry in the iSNS database.

6.4.4.  iSCSI Node SCN Bitmap

   The iSCSI Node SCN Bitmap indicates events for which the registering
   iSNS client wishes to receive a notification message.  The following
   table displays events that result in notifications, and the bit field
   in the SCN Bitmap that, when enabled, results in the corresponding
   notification.

   Note that this field is of dual use: it is used in the SCN
   registration process to define interested events that will trigger an
   SCN message, and it is also contained in each SCN message itself, to
   indicate the type of event that triggered the SCN message.  A set bit
   (1) indicates the corresponding type of SCN.

          Bit Position       Flag Description
          ------------       ----------------
           24                INITIATOR AND SELF INFORMATION ONLY
           25                TARGET AND SELF INFORMATION ONLY
           26                MANAGEMENT REGISTRATION/SCN
           27                OBJECT REMOVED
           28                OBJECT ADDED
           29                OBJECT UPDATED
           30                DD/DDS MEMBER REMOVED (Mgmt Reg/SCN only)
           31 (Lsb)          DD/DDS MEMBER ADDED (Mgmt Reg/SCN only)
           All others        RESERVED

   DD/DDS MEMBER REMOVED indicates that an existing member of a
   Discovery Domain and/or Discovery Domain Set has been removed.

   DD/DDS MEMBER ADDED indicates that a new member was added to an
   existing DD and/or DDS.

   OBJECT REMOVED, OBJECT ADDED, and OBJECT UPDATED indicate a Network
   Entity, Portal, Storage Node, FC Device, DD, and/or DDS object was
   removed from, added to, or updated in the Discovery Domain or in the
   iSNS database (Control Nodes only).

   Regular SCNs provide information about objects that are updated in,
   added to or removed from Discovery Domains of which the Storage Node
   is a member.  An SCN or SCN registration is considered a regular SCN
   or regular SCN registration if the MANAGEMENT REGISTRATION/SCN flag
   is cleared.  All iSNS clients may register for regular SCNs.

   Management SCNs provide information about all changes to the network,
   regardless of discovery domain membership.  Registration for
   management SCNs is indicated by setting bit 26 to 1.  Only Control
   Nodes may register for management SCNs.  Bits 30 and 31 may only be
   enabled if bit 26 is set to 1.

   TARGET AND SELF INFORMATION ONLY SCNs (bit 25) provides information
   only about changes to target devices, or if the iSCSI Storage Node
   itself has undergone a change.  Similarly, INITIATOR AND SELF
   INFORMATION ONLY SCNs (bit 24) provides information only about
   changes to initiator Nodes, or to the target itself.

6.4.5.  iSCSI Node Index

   The iSCSI Node Index is a 4-byte non-zero integer value used as a key
   that uniquely identifies each iSCSI Storage Node registered in the
   iSNS database.  Upon initial registration of the iSCSI Storage Node,
   the iSNS server assigns an unused value for the iSCSI Node Index.
   Each iSCSI Node MUST be assigned a value for the iSCSI Node Index
   that is not assigned to any other iSCSI Storage Node.  Furthermore,
   iSCSI Node Index values for recently deregistered iSCSI Storage Nodes
   SHOULD NOT be reused in the short term.

   The iSCSI Node Index may be used as a key to represent a registered
   Node in situations where the iSCSI Name is too long to be used as a
   key.  An example of this is when SNMP is used for management, as
   described in Section 2.10.

   The value assigned for the iSCSI Node Index SHALL persist as long as
   the iSCSI Storage Node is registered in the iSNS database or a member
   of a Discovery Domain.  An iSCSI Node Index value that is assigned
   for a Storage Node SHALL NOT be used for any other Storage Node as
   long as the original node is registered in the iSNS database or a
   member of a Discovery Domain.

6.4.6.  WWNN Token

   This field contains a globally unique 64-bit integer value that can
   be used to represent the World Wide Node Name of the iSCSI device in
   a Fibre Channel fabric.  This identifier is used during the device
   registration process and MUST conform to the requirements in [FC-FS].

   The FC-iSCSI gateway uses the value found in this field to register
   the iSCSI device in the Fibre Channel name server.  It is stored in
   the iSNS server to prevent conflict when "proxy" WWNN values are
   assigned to iSCSI initiators establishing storage sessions to devices
   in the FC fabric.

   If the iSNS client does not assign a value for WWNN Token, then the
   iSNS server SHALL provide a value for this field upon initial
   registration of the iSCSI Storage Node.  The process by which the
   WWNN Token is assigned by the iSNS server MUST conform to the
   following requirements:

   1.  The assigned WWNN Token value MUST be unique among all WWN
       entries in the existing iSNS database, and among all devices that
       can potentially be registered in the iSNS database.

   2.  Once the value is assigned, the iSNS server MUST persistently
       save the mapping between the WWNN Token value and registered
       iSCSI Name.  That is, successive re-registrations of the iSCSI
       Storage Node keyed by the same iSCSI Name maintain the original
       mapping to the associated WWNN Token value in the iSNS server.
       Similarly, the mapping SHALL be persistent across iSNS server
       reboots.  Once assigned, the mapping can only be changed if a
       DevAttrReg message from an authorized iSNS client explicitly
       provides a different WWNN Token value.

   3.  Once a WWNN Token value has been assigned and mapped to an iSCSI
       name, that WWNN Token value SHALL NOT be reused or mapped to any
       other iSCSI name.

   4.  The assigned WWNN Token value MUST conform to the formatting
       requirements of [FC-FS] for World Wide Names (WWNs).

   An iSNS client, such as an FC-iSCSI gateway or the iSCSI initiator,
   MAY register its own WWNN Token value or overwrite the iSNS Server-
   supplied WWNN Token value, if it wishes to supply its own iSCSI-FC
   name mapping.  This is accomplished using the DevAttrReg message with
   the WWNN Token (tag=37) as an operating attribute.  Once overwritten,
   the new WWNN Token value MUST be stored and saved by the iSNS server,
   and all requirements specified above continue to apply.  If an iSNS
   client attempts to register a value for this field that is not unique
   in the iSNS database or that is otherwise invalid, then the
   registration SHALL be rejected with an Status Code of 3 (Invalid
   Registration).

   There MAY be matching records in the iSNS database for the Fibre
   Channel device specified by the WWNN Token.  These records may
   contain device attributes for that FC device registered in the Fibre
   Channel fabric name server.

6.4.7.  iSCSI Node Next Index

   This is a virtual attribute containing a 4-byte integer value that
   indicates the next available (i.e., unused) iSCSI Node Index value.
   This attribute may only be queried; the iSNS server SHALL return an
   error code of 3 (Invalid Registration) to any client that attempts to
   register a value for this attribute.  A Message Key is not required
   when exclusively querying for this attribute.

   The iSCSI Node Next Index MAY be used by an SNMP client to create an
   entry in the iSNS server.  SNMP requirements are described in Section
   2.10.

6.4.8.  iSCSI AuthMethod

   This attribute contains a NULL-terminated string of UTF-8 text
   listing the iSCSI authentication methods enabled for this iSCSI
   Storage Node, in order of preference.  The text values used to
   identify iSCSI authentication methods are embedded in this string
   attribute and delineated by a comma.  The text values are identical
   to those found in the main iSCSI document [iSCSI]; additional
   vendor-specific text values are also possible.

          Text Value       Description                   Reference
          ----------       -----------                   ---------
           KB5             Kerberos V5                   [RFC1510]
           SPKM1           Simple Public Key GSS-API     [RFC2025]
           SPKM2           Simple Public Key GSS-API     [RFC2025]
           SRP             Secure Remote Password        [RFC2945]
           CHAP            Challenge Handshake Protocol  [RFC1994]
           none            No iSCSI Authentication

6.5.  Portal Group (PG) Object-Keyed Attributes

   The following attributes are used to associate Portal and iSCSI
   Storage Node objects.  PG objects are stored in the iSNS database
   using the PG iSCSI Name, the PG Portal IP Address, and the PG Portal
   TCP/UDP Port as keys.  New PG objects are implicitly or explicitly
   created at the time that the corresponding Portal and/or iSCSI
   Storage Node objects are registered.  Section 3.4 has a general
   discussion of PG usage.  For further details on use of Portal Groups,
   see [iSCSI].

6.5.1.  Portal Group iSCSI Name

   This is the iSCSI Name for the iSCSI Storage Node that is associated
   with the PG object.  This name MAY represent an iSCSI Storage Node
   not currently registered in the server.

6.5.2.  PG Portal IP Addr

   This is the Portal IP Address attribute for the Portal that is
   associated with the PG object.  This Portal IP Address MAY be that of
   a Portal that is not currently registered in the server.

6.5.3.  PG Portal TCP/UDP Port

   This is the Portal TCP/UDP Port attribute for the Portal that is
   associated with the PG object.  This Portal TCP/UDP Port MAY be that
   of a Portal that is not currently registered in the server.

6.5.4.  Portal Group Tag (PGT)

   This field is used to group Portals in order to coordinate
   connections in a session across Portals to a specified iSCSI Node.
   The PGT is a value in the range of 0-65535, or NULL.  A NULL PGT
   value is registered by using 0 for the length in the TLV during
   registration.  The two least significant bytes of the value contain
   the PGT for the object.  The two most significant bytes are reserved.
   If a PGT value is not explicitly registered for an iSCSI Storage Node
   and Portal pair, then the PGT value SHALL be implicitly registered as
   0x00000001.

6.5.5.  Portal Group Index

   The PG Index is a 4-byte non-zero integer value used as a key that
   uniquely identifies each PG object registered in the iSNS database.
   Upon initial registration of a PG object, the iSNS server MUST assign
   an unused value for the PG Index.  Furthermore, PG Index values for
   recently deregistered PG objects SHOULD NOT be reused in the short
   term.

   The PG Index MAY be used as the key to reference a registered PG in
   situations where a unique index for each PG object is required.  It
   MAY also be used as the message key in an iSNS message to query or
   update a pre-existing PG object.  An example of this is when SNMP is
   used for management, as described in Section 2.10.  The value
   assigned for the PG Index SHALL persist as long as the server is
   active.

6.5.6.  Portal Group Next Index

   The PG Next Index is a virtual attribute containing a 4-byte integer
   value that indicates the next available (i.e., unused) PG Index
   value.  This attribute may only be queried; the iSNS server SHALL
   return an error code of 3 (Invalid Registration) to any client that
   attempts to register a value for this attribute.  A Message Key is
   not required when exclusively querying for this attribute.

   The Portal Group Next Index MAY be used by an SNMP client to create
   an entry in the iSNS server.  SNMP requirements are described in
   Section 2.10.

6.6.  FC Port Name-Keyed Attributes

   The following attributes are registered in the iSNS database using
   the FC Port World Wide Name (WWPN) attribute as the key.  Each set of
   FC Port-Keyed attributes is associated with one Entity Identifier
   object key.

   Although the FC Port World Wide Name is associated with one Entity
   Identifier, it is also globally unique.

6.6.1.  FC Port Name (WWPN)

   This 64-bit identifier uniquely defines the FC Port, and it is the
   World Wide Port Name (WWPN) of the corresponding Fibre Channel
   device.  This attribute is the key for the iFCP Storage Node.  This
   globally unique identifier is used during the device registration
   process, and it uses a value conforming to IEEE EUI-64 [EUI-64].

6.6.2.  Port ID (FC_ID)

   The Port Identifier is a Fibre Channel address identifier assigned to
   an N_Port or NL_Port during fabric login.  The format of the Port
   Identifier is defined in [FC-FS].  The least significant 3 bytes
   contain this address identifier.  The most significant byte is
   RESERVED.

6.6.3.  FC Port Type

   Indicates the type of FC port.  Encoded values for this field are
   listed in the following table:

          Type              Description
          ----              -----------
           0x0000           Unidentified/Null Entry
           0x0001           Fibre Channel N_Port
           0x0002           Fibre Channel NL_Port
           0x0003           Fibre Channel F/NL_Port
           0x0004-0080      RESERVED
           0x0081           Fibre Channel F_Port
           0x0082           Fibre Channel FL_Port
           0x0083           RESERVED
           0x0084           Fibre Channel E_Port
           0x0085-00FF      RESERVED
           0xFF11           RESERVED
           0xFF12           iFCP Port
           0xFF13-FFFF      RESERVED

6.6.4.  Symbolic Port Name

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 256 bytes that is associated with the iSNS-
   registered FC Port Name in the network.

6.6.5.  Fabric Port Name (FWWN)

   This 64-bit identifier uniquely defines the fabric port.  If the port
   of the FC Device is attached to a Fibre Channel fabric port with a
   registered Port Name, then that fabric Port Name SHALL be indicated
   in this field.

6.6.6.  Hard Address

   This field is the requested hard address 24-bit NL Port Identifier,
   included in the iSNSP for compatibility with Fibre Channel Arbitrated
   Loop devices and topologies.  The least significant 3 bytes of this
   field contain the address.  The most significant byte is RESERVED.

6.6.7.  Port IP Address

   The Fibre Channel IP address associated with the FC Port.  When this
   field contains an IPv4 value, it is stored as an IPv4-mapped IPv6
   address.  That is, the most significant 10 bytes are set to 0x00,
   with the next two bytes set to 0xFFFF [RFC2373].  When an IPv6 value
   is contained in this field, then the entire 16-byte field is used.

6.6.8.  Class of Service (COS)

   This 32-bit bit-map field indicates the Fibre Channel Class of
   Service types that are supported by the registered port.  In the
   following table, a set bit (1) indicates a Class of Service
   supported.

          Bit Position       Description
          ------------       -----------
           29                Fibre Channel Class 2 Supported
           28                Fibre Channel Class 3 Supported

6.6.9.  FC-4 Types

   This 32-byte field indicates the FC-4 protocol types supported by the
   associated port.  This field can be used to support Fibre Channel
   devices and is consistent with FC-GS-4.

6.6.10.  FC-4 Descriptor

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 256 bytes that is associated with the iSNS-
   registered device port in the network.  This field can be used to
   support Fibre Channel devices and is consistent with FC-GS-4.

6.6.11.  FC-4 Features

   This is a 128-byte array, 4 bits per type, for the FC-4 protocol
   types supported by the associated port.  This field can be used to
   support Fibre Channel devices and is consistent with FC-GS-4.

6.6.12.  iFCP SCN Bitmap

   This field indicates the events the iSNS client is interested in.
   These events can cause SCNs to be generated.  SCNs provide
   information about objects that are updated in, added to or removed
   from Discovery Domains of which the source and destination are a
   member.  Management SCNs provide information about all changes to the
   network.  A set bit (1) indicates the type of SCN for the bitmap as
   follows:

          Bit Position       Flag Description
          ------------       ----------------
           24                INITIATOR AND SELF INFORMATION ONLY
           25                TARGET AND SELF INFORMATION ONLY
           26                MANAGEMENT REGISTRATION/SCN
           27                OBJECT REMOVED
           28                OBJECT ADDED
           29                OBJECT UPDATED
           30                DD/DDS MEMBER REMOVED (Mgmt Reg/SCN only)
           31 (Lsb)          DD/DDS MEMBER ADDED (Mgmt Reg/SCN only)
           All others        RESERVED

   Further information on the use of the bit positions specified above
   can be found in Section 6.4.4.

6.6.13.  Port Role

   This required 32-bit field is a bitmap indicating the type of iFCP
   Storage Node.  The bit fields are defined below.  A set bit indicates
   the Node has the corresponding characteristics.

          Bit Position       Node Type
          ------------       ---------
           29                Control
           30                FCP Initiator
           31 (Lsb)          FCP Target
           All Others        RESERVED

   If the 'Target' bit is set to 1, then the port represents an FC
   target.  Setting of the 'Target' bit MAY be performed by iSNS clients
   using the iSNSP.

   If the 'Initiator' bit is set to 1, then the port represents an FC
   initiator.  Setting of the 'Initiator' bit MAY be performed by iSNS
   clients using the iSNSP.

   If the 'Control' bit is set to 1, then the port represents a gateway,
   a management station, an iSNS backup server, or another device.

   This is usually a special device that is neither an initiator nor a
   target, which requires the ability to send and receive iSNSP
   messages, including state-change notifications.  Setting the control
   bit is an administrative task that MUST be administratively
   configured on the iSNS server; iSNS clients SHALL NOT be allowed to
   change this bit using the iSNSP.

   This field MAY be used by the iSNS server to distinguish among
   permissions by different iSNS clients.  For example, an iSNS server
   implementation may be administratively configured to allow only
   targets to receive ESIs, or to permit only Control Nodes to add,
   modify, or delete discovery domains.

6.6.14.  Permanent Port Name (PPN)

   The Permanent Port Name can be used to support Fibre Channel devices
   and is consistent with the PPN description in FC-GS-4 [FC-GS-4].  The
   format of the PPN is identical to the FC Port Name WWPN attribute
   format.

6.7.  Node-Keyed Attributes

   The following attributes are registered in the iSNS database using
   the FC Node Name (WWNN) attribute as the key.  Each set of FC Node-
   Keyed attributes represents a single device and can be associated
   with many FC Ports.

   The FC Node Name is unique across the entire iSNS database.

6.7.1.  FC Node Name (WWNN)

   The FC Node Name is a 64-bit identifier that is the World Wide Node
   Name (WWNN) of the corresponding Fibre Channel device.  This
   attribute is the key for the FC Device.  This globally unique
   identifier is used during the device registration process, and it
   uses a value conforming to IEEE EUI-64 [EUI-64].

6.7.2.  Symbolic Node Name

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   description of up to 256 bytes that is associated with the iSNS-
   registered FC Device in the network.

6.7.3.  Node IP Address

   This IP address is associated with the device Node in the network.
   This field is included for compatibility with Fibre Channel.  When
   this field contains an IPv4 value, it is stored as an IPv4-mapped
   IPv6 address.  That is, the most significant 10 bytes are set to
   0x00, with the next two bytes set to 0xFFFF [RFC2373].  When an IPv6
   value is contained in this field, the entire 16-byte field is used.

6.7.4.  Node IPA

   This field is the 8-byte Fibre Channel Initial Process Associator
   (IPA) associated with the device Node in the network.  The initial
   process associator is used for communication between Fibre Channel
   devices.

6.7.5.  Proxy iSCSI Name

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   field that contains the iSCSI Name used to represent the FC Node in
   the IP network.  It is used as a pointer to the matching iSCSI Name
   entry in the iSNS server.  Its value is usually registered by an FC-
   iSCSI gateway connecting the IP network to the fabric containing the
   FC device.

   Note that if this field is used, there SHOULD be a matching entry in
   the iSNS database for the iSCSI device specified by the iSCSI name.
   The database entry should include the full range of iSCSI attributes
   needed for discovery and management of the "iSCSI proxy image" of the
   FC device.

6.8.  Other Attributes

   The following are not attributes of the previously-defined objects.

6.8.1.  FC-4 Type Code

   This is a 4-byte field used to provide a FC-4 type during a FC-4 Type
   query.  The FC-4 types are consistent with the FC-4 Types as defined
   in FC-FS.  Byte 0 contains the FC-4 type.  All other bytes are
   reserved.

6.8.2.  iFCP Switch Name

   The iFCP Switch Name is a 64-bit World Wide Name (WWN) identifier
   that uniquely identifies a distinct iFCP gateway in the network.
   This globally unique identifier is used during the switch
   registration/FC_DOMAIN_ID assignment process.  The iFCP Switch Name
   value used MUST conform to the requirements stated in [FC-FS] for
   World Wide Names.  The iSNS server SHALL track the state of all
   FC_DOMAIN_ID values that have been allocated to each iFCP Switch
   Name.  If a given iFCP Switch Name is deregistered from the iSNS
   database, then all FC_DOMAIN_ID values allocated to that iFCP Switch
   Name SHALL be returned to the unused pool of values.

6.8.3.  iFCP Transparent Mode Commands

6.8.3.1.  Preferred ID

   This is a 4-byte unsigned integer field, and it is the requested
   value that the iSNS client wishes to use for the FC_DOMAIN_ID.  The
   iSNS server SHALL grant the iSNS client the use of the requested
   value as the FC_DOMAIN_ID, if the requested value has not already
   been allocated.  If the requested value is not available, the iSNS
   server SHALL return a different value that has not been allocated.

6.8.3.2.  Assigned ID

   This is a 4-byte unsigned integer field that is used by an iFCP
   gateway to reserve its own unique FC_DOMAIN_ID value from the range 1
   to 239.  When a FC_DOMAIN_ID is no longer required, it SHALL be
   released by the iFCP gateway using the RlseDomId message.  The iSNS
   server MUST use the Entity Status Inquiry message to determine
   whether an iFCP gateway is still present on the network.

6.8.3.3.  Virtual_Fabric_ID

   This is a variable-length UTF-8 encoded NULL-terminated text-based
   field of up to 256 bytes.  The Virtual_Fabric_ID string is used as a
   key attribute to identify a range of non-overlapping FC_DOMAIN_ID
   values to be allocated using RqstDomId.  Each Virtual_Fabric_ID
   string submitted by an iSNS client SHALL have its own range of non-
   overlapping FC_DOMAIN_ID values to be allocated to iSNS clients.

6.9.  iSNS Server-Specific Attributes

   Access to the following attributes may be administratively
   controlled.  These attributes are specific to the iSNS server
   instance; the same value is returned for all iSNS clients accessing
   the iSNS server.  Only query messages may be performed on these
   attributes.  Attempted registrations of values for these attributes
   SHALL return a status code of 3 (Invalid Registration).

   A query for an iSNS Server-Specific attribute MUST contain the
   identifying key attribute (i.e., iSCSI Name or FC Port Name WWPN) of
   the Node originating the registration or query message as the Source
   and Message Key attributes.  The Operating Attributes are the
   server-specific attributes being registered or queried.

6.9.1.  iSNS Server Vendor OUI

   This attribute is the OUI (Organizationally Unique Identifier)
   [802-1990] identifying the specific vendor implementing the iSNS
   server. This attribute can only be queried; iSNS clients SHALL NOT be
   allowed to register a value for the iSNS Server Vendor OUI.

6.10.  Vendor-Specific Attributes

   iSNS server implementations MAY define vendor-specific attributes for
   private use.  These attributes MAY be used to store optional data
   that is registered and/or queried by iSNS clients in order to gain
   optional capabilities.  Note that any implementation of vendor-
   specific attributes in the iSNS server SHALL NOT impose any form of
   mandatory behavior on the part of the iSNS client.

   The tag values used for vendor-specific and user-specific use are
   defined in Section 6.1.  To avoid misinterpreting proprietary
   attributes, the vendor's own OUI (Organizationally Unique Identifier)
   MUST be placed in the upper three bytes of the attribute value field
   itself.

   The OUI is defined in IEEE Std 802-1990 and is the same constant used
   to generate 48 bit Universal LAN MAC addresses.  A vendor's own iSNS
   implementation will then be able to recognize the OUI in the
   attribute field and be able to execute vendor-specific handling of
   the attribute.

6.10.1.  Vendor-Specific Server Attributes

   Attributes with tags in the range 257 to 384 are vendor-specific or
   site-specific attributes of the iSNS server.  Values for these
   attributes are administratively set by the specific vendor providing
   the iSNS server implementation.  Query access to these attributes may
   be administratively controlled.  These attributes are unique for each
   logical iSNS server instance.  Query messages for these attributes
   SHALL use the key identifier (i.e., iSCSI Name or FC Port Name WWPN)
   for both the Source attribute and Message Key attribute.  These
   attributes can only be queried; iSNS clients SHALL NOT be allowed to
   register a value for server attributes.

6.10.2.  Vendor-Specific Entity Attributes

   Attributes in the range 385 to 512 are vendor-specific or site-
   specific attributes used to describe the Network Entity object.
   These attributes are keyed by the Entity Identifier attribute
   (tag=1).

6.10.3.  Vendor-Specific Portal Attributes

   Attributes in the range 513 to 640 are vendor-specific or site-
   specific attributes used to describe the Portal object.  These
   attributes are keyed by the Portal IP-Address (tag=16) and Portal
   TCP/UDP Port (tag=17).

6.10.4.  Vendor-Specific iSCSI Node Attributes

   Attributes in the range 641 to 768 are vendor-specific or site-
   specific attributes used to describe the iSCSI Node object.  These
   attributes are keyed by the iSCSI Name (tag=32).

6.10.5.  Vendor-Specific FC Port Name Attributes

   Attributes in the range 769 to 896 are vendor-specific or site-
   specific attributes used to describe the N_Port Port Name object.
   These attributes are keyed by the FC Port Name WWPN (tag=64).

6.10.6.  Vendor-Specific FC Node Name Attributes

   Attributes in the range 897 to 1024 are vendor-specific or site-
   specific attributes used to describe the FC Node Name object.  These
   attributes are keyed by the FC Node Name WWNN (tag=96).

6.10.7.  Vendor-Specific Discovery Domain Attributes

   Attributes in the range 1025 to 1280 are vendor-specific or site-
   specific attributes used to describe the Discovery Domain object.
   These attributes are keyed by the DD_ID (tag=104).

6.10.8.  Vendor-Specific Discovery Domain Set Attributes

   Attributes in the range 1281 to 1536 are vendor-specific or site-
   specific attributes used to describe the Discovery Domain Set object.
   These attributes are keyed by the DD Set ID (tag=101)

6.10.9.  Other Vendor-Specific Attributes

   Attributes in the range 1537 to 2048 can be used for key and non-key
   attributes that describe new vendor-specific objects specific to the
   vendor's iSNS server implementation.

6.11.  Discovery Domain Registration Attributes

6.11.1.  DD Set ID Keyed Attributes

6.11.1.1.  Discovery Domain Set ID (DDS ID)

   The DDS ID is an unsigned non-zero integer identifier used in the
   iSNS directory database as a key to indicate a Discovery Domain Set
   uniquely.  A DDS is a collection of Discovery Domains that can be
   enabled or disabled by a management station.  This value is used as a
   key for DDS attribute queries.  When a Discovery Domain is
   registered, it is initially not in any DDS.

   If the iSNS client does not provide a DDS_ID in a DDS registration
   request message, the iSNS server SHALL generate a DDS_ID value that
   is unique within the iSNS database for that new DDS.  The created DDS
   ID SHALL be returned in the response message.  The DDS ID value of 0
   is reserved, and the DDS ID value of 1 is used for the default DDS
   (see Section 2.2.2).

6.11.1.2.  Discovery Domain Set Symbolic Name

   A variable-length UTF-8 encoded NULL-terminated text-based field of
   up to 256 bytes.  This is a user-readable field used to assist a
   network administrator in tracking the DDS function.  When a client
   registers a DDS symbolic name, the iSNS server SHALL verify it is
   unique.  If the name is not unique, then the DDS registration SHALL
   be rejected with an "Invalid Registration" Status Code.  The invalid
   attribute(s), in this case the DDS symbolic name, SHALL be included
   in the response.

6.11.1.3.  Discovery Domain Set Status

   The DDS_Status field is a 32-bit bitmap indicating the status of the
   DDS.  Bit 0 of the bitmap indicates whether the DDS is Enabled (1) or
   Disabled (0).  The default value for the DDS Enabled flag is Disabled
   (0).

          Bit Position    DDS Status
          ------------    ---------
           31  (Lsb)      DDS Enabled (1) / DDS Disabled (0)
           All others     RESERVED

6.11.1.4.  Discovery Domain Set Next ID

   This is a virtual attribute containing a 4-byte integer value that
   indicates the next available (i.e., unused) Discovery Domain Set
   Index value.  This attribute may only be queried; the iSNS server

   SHALL return an error code of 3 (Invalid Registration) to any client
   that attempts to register a value for this attribute.  A Message Key
   is not required when exclusively querying for this attribute.

   The Discovery Domain Set Next Index MAY be used by an SNMP client to
   create an entry in the iSNS server.  SNMP requirements are described
   in Section 2.10.

6.11.2.  DD ID Keyed Attributes

6.11.2.1.  Discovery Domain ID (DD ID)

   The DD ID is an unsigned non-zero integer identifier used in the iSNS
   directory database as a key to identify a Discovery Domain uniquely.
   This value is used as the key for any DD attribute query.  If the
   iSNS client does not provide a DD_ID in a DD registration request
   message, the iSNS server SHALL generate a DD_ID value that is unique
   within the iSNS database for that new DD (i.e., the iSNS client will
   be registered in a new DD).  The created DD ID SHALL be returned in
   the response message.  The DD ID value of 0 is reserved, and the DD
   ID value of 1 is used for the default DD (see Section 2.2.2).

6.11.2.2.  Discovery Domain Symbolic Name

   A variable-length UTF-8 encoded NULL-terminated text-based field of
   up to 256 bytes.  When a client registers a DD symbolic name, the
   iSNS server SHALL verify it is unique.  If the name is not unique,
   then the DD registration SHALL be rejected with an "Invalid
   Registration" Status Code.  The invalid attribute(s), in this case
   the DD symbolic name, SHALL be included in the response.

6.11.2.3.  Discovery Domain Member: iSCSI Node Index

   This is the iSCSI Node Index of a Storage Node that is a member of
   the DD.  The DD may have a list of 0 to n members.  The iSCSI Node
   Index is one alternative representation of membership in a Discovery
   Domain, the other alternative being the iSCSI Name.  The Discovery
   Domain iSCSI Node Index is a 4-byte non-zero integer value.

   The iSCSI Node Index can be used to represent a DD member in
   situations where the iSCSI Name is too long to be used.  An example
   of this is when SNMP is used for management, as described in Section
   2.10.

   The iSCSI Node Index and the iSCSI Name stored as a member in a DD
   SHALL be consistent with the iSCSI Node Index and iSCSI Name
   attributes registered for the Storage Node object in the iSNS server.

6.11.2.4.  Discovery Domain Member: iSCSI Name

   A variable-length UTF-8 encoded NULL-terminated text-based field of
   up to 224 bytes.  It indicates membership for the specified iSCSI
   Storage Node in the Discovery Domain.  Note that the referenced
   Storage Node does not need to be actively registered in the iSNS
   database before the iSNS client uses this attribute.  There is no
   limit to the number of members that may be in a DD.  Membership is
   represented by the iSCSI Name of the iSCSI Storage Node.

6.11.2.5.  Discovery Domain Member: FC Port Name

   This 64-bit identifier attribute indicates membership for an iFCP
   Storage Node (FC Port) in the Discovery Domain.  Note that the
   referenced Storage Node does not need to be actively registered in
   the iSNS database before the iSNS client uses this attribute.  There
   is no limit to the number of members that may be in a DD.  Membership
   is represented by the FC Port Name (WWPN) of the iFCP Storage Node.

6.11.2.6.  Discovery Domain Member: Portal Index

   This attribute indicates membership in the Discovery Domain for a
   Portal.  It is an alternative representation for Portal membership to
   the Portal IP Address and Portal TCP/UDP Port.  The referenced Portal
   MUST be actively registered in the iSNS database before the iSNS
   client uses this attribute.

6.11.2.7.  Discovery Domain Member: Portal IP Address

   This attribute and the Portal TCP/UDP Port attribute indicate
   membership in the Discovery Domain for the specified Portal.  Note
   that the referenced Portal does not need to be actively registered in
   the iSNS database before the iSNS client uses this attribute.

6.11.2.8.  Discovery Domain Member: Portal TCP/UDP Port

   This attribute and the Portal IP Address attribute indicate
   membership in the Discovery Domain for the specified Portal.  Note
   that the referenced Portal does not need to be actively registered in
   the iSNS database before the iSNS client uses this attribute.

6.11.2.9.  Discovery Domain Features

   The Discovery Domain Features is a bitmap indicating the features of
   this DD.  The bit positions are defined below.  A bit set to 1
   indicates the DD has the corresponding characteristics.

          Bit Position     DD Feature
          ------------     ----------
           31 (Lsb)        Boot List Enabled (1)/Boot List Disabled (0)
           All others      RESERVED

   Boot List: this feature indicates that the target(s) in this DD
   provides boot capabilities for the member initiators, as described in
   [iSCSI-boot].

6.11.2.10.  Discovery Domain Next ID

   This is a virtual attribute containing a 4-byte integer value that
   indicates the next available (i.e., unused) Discovery Domain Index
   value.  This attribute may only be queried; the iSNS server SHALL
   return an error code of 3 (Invalid Registration) to any client that
   attempts to register a value for this attribute.  A Message Key is
   not required when exclusively querying for this attribute.

7.  Security Considerations

7.1.  iSNS Security Threat Analysis

   When the iSNS protocol is deployed, the interaction between iSNS
   server and iSNS clients is subject to the following security threats:

   a)  An attacker could alter iSNS protocol messages, such as to direct
       iSCSI and iFCP devices to establish connections with rogue peer
       devices, or to weaken/eliminate IPSec protection for iSCSI or
       iFCP traffic.

   b)  An attacker could masquerade as the real iSNS server using false
       iSNS heartbeat messages.  This could cause iSCSI and iFCP devices
       to use rogue iSNS servers.

   c)  An attacker could gain knowledge about iSCSI and iFCP devices by
       snooping iSNS protocol messages.  Such information could aid an
       attacker in mounting a direct attack on iSCSI and iFCP devices,
       such as a denial-of-service attack or outright physical theft.

   To address these threats, the following capabilities are needed:

   a)  Unicast iSNS protocol messages may need to be authenticated.  In
       addition, to protect against threat c), confidentiality support
       is desirable and is REQUIRED when certain functions of iSNS
       server are utilized.

   b)  Multicast iSNS protocol messages such as the iSNS heartbeat
       message may need to be authenticated.  These messages need not be
       confidential since they do not leak critical information.

7.2.  iSNS Security Implementation and Usage Requirements

   If the iSNS server is used to distribute authorizations for
   communications between iFCP and iSCSI peer devices, IPsec ESP with
   null transform MUST be implemented, and non-null transform MAY be
   implemented.  If a non-null transform is implemented, then the DES
   encryption algorithm SHOULD NOT be used.

   If the iSNS server is used to distribute security policy for iFCP and
   iSCSI devices, then authentication, data integrity, and
   confidentiality MUST be supported and used.  Where confidentiality is
   desired or required, IPSec ESP with non-null transform SHOULD be
   used, and the DES encryption algorithm SHOULD NOT be used.

   If the iSNS server is used to provide the boot list for clients, as
   described in Section 6.11.2.9, then the iSCSI boot client SHOULD
   implement a secure iSNS connection.

   In order to protect against an attacker masquerading as an iSNS
   server, client devices MUST support the ability to authenticate
   broadcast or multicast messages such as the iSNS heartbeat.  The iSNS
   authentication block (which is identical in format to the SLP
   authentication block) SHALL be used for this purpose.  iSNS clients
   MUST implement the iSNS authentication block and MUST support BSD
   value 0x002.  If the iSNS server supports broadcast or multicast iSNS
   messages (i.e., the heartbeat), then the server MUST implement the
   iSNS authentication block and MUST support BSD value 0x002.  Note
   that the authentication block is used only for iSNS broadcast or
   multicast messages and MUST NOT be used in unicast iSNS messages.

   There is no requirement that the communicating identities in iSNS
   protocol messages be kept confidential.  Specifically, the identity
   and location of the iSNS server is not considered confidential.

   For protecting unicast iSNS protocol messages, iSNS servers
   supporting security MUST implement ESP in tunnel mode and MAY
   implement transport mode.

   All iSNS implementations supporting security MUST support the replay
   protection mechanisms of IPsec.

   iSNS security implementations MUST support both IKE Main Mode and
   Aggressive Mode for authentication, negotiation of security
   associations, and key management, using the IPSec DOI [RFC2407].

   Manual keying SHOULD NOT be used since it does not provide the
   necessary rekeying support.  Conforming iSNS security implementations
   MUST support authentication using a pre-shared key, and MAY support
   certificate-based peer authentication using digital signatures.  Peer
   authentication using the public key encryption methods outlined in
   IKEs Sections 5.2 and 5.3 [RFC2409] SHOULD NOT be supported.

   Conforming iSNS implementations MUST support both IKE Main Mode and
   Aggressive Mode.  IKE Main Mode with pre-shared key authentication
   SHOULD NOT be used when either of the peers use dynamically assigned
   IP addresses.  Although Main Mode with pre-shared key authentication
   offers good security in many cases, situations where dynamically
   assigned addresses are used force the use of a group pre-shared key,
   which is vulnerable to man-in-the-middle attack.  IKE Identity
   Payload ID_KEY_ID MUST NOT be used.

   When digital signatures are used for authentication, either IKE Main
   Mode or IKE Aggressive Mode MAY be used.  In all cases, access to
   locally stored secret information (pre-shared key or private key for
   digital signing) MUST be suitably restricted, since compromise of the
   secret information nullifies the security properties of the IKE/IPsec
   protocols.

   When digital signatures are used to achieve authentication, an IKE
   negotiator SHOULD use IKE Certificate Request Payload(s) to specify
   the certificate authority (or authorities) that are trusted in
   accordance with its local policy.  IKE negotiators SHOULD check the
   pertinent Certificate Revocation List (CRL) before accepting a PKI
   certificate for use in IKE's authentication procedures.

   When the iSNS server is used without security, IP block storage
   protocol implementations MUST support a negative cache for
   authentication failures.  This allows implementations to avoid
   continually contacting discovered endpoints that fail authentication
   within IPsec or at the application layer (in the case of iSCSI
   Login).  The negative cache need not be maintained within the IPsec
   implementation, but rather within the IP block storage protocol
   implementation.

7.3.  Discovering Security Requirements of Peer Devices

   Once communication between iSNS clients and the iSNS server has been
   secured through use of IPSec, the iSNS client devices have the
   capability to discover the security settings that they need to use
   for their peer-to-peer communications using the iSCSI and/or iFCP
   protocols.  This provides a potential scaling advantage over device-
   by-device configuration of individual security policies for each
   iSCSI and iFCP device.

   The iSNS server stores security settings for each iSCSI and iFCP
   device interface.  These security settings, which can be retrieved by
   authorized hosts, include use or non-use of IPSec, IKE, Main Mode,
   and Aggressive Mode.  For example, IKE may not be enabled for a
   particular interface of a peer device.  If a peer device can learn of
   this in advance by consulting the iSNS server, it will not need to
   waste time and resources attempting to initiate an IKE phase 1
   session with that peer device interface.

   If iSNS is used for this purpose, then the minimum information that
   should be learned from the iSNS server is the use or non-use of IKE
   and IPSec by each iFCP or iSCSI peer device interface.  This
   information is encoded in the Security Bitmap field of each Portal of
   the peer device, and is applicable on a per-interface basis for the
   peer device.  iSNS queries for acquiring security configuration data
   about peer devices MUST be protected by IPSec/ESP authentication.

7.4.  Configuring Security Policies of iFCP/iSCSI Devices

   Use of iSNS for distribution of security policies offers the
   potential to reduce the burden of manual device configuration, and to
   decrease the probability of communications failures due to
   incompatible security policies.  If iSNS is used to distribute
   security policies, then IPSec authentication, data integrity, and
   confidentiality MUST be used to protect all iSNS protocol messages.

   The complete IKE/IPSec configuration of each iFCP and/or iSCSI device
   can be stored in the iSNS server, including policies that are used
   for IKE Phase 1 and Phase 2 negotiations between client devices.  The
   IKE payload format includes a series of one or more proposals that
   the iSCSI or iFCP device will use when negotiating the appropriate
   IPsec policy to use to protect iSCSI or iFCP traffic.

   In addition, the iSCSI Authentication Methods used by each iSCSI
   device can also be stored in the iSNS server.  The iSCSI AuthMethod
   field (tag=42) contains a null-terminated string embedded with the
   text values indicating iSCSI authentication methods to be used by
   that iSCSI device.

   Note that iSNS distribution of security policy is not necessary if
   the security settings can be determined by other means, such as
   manual configuration or IPsec security policy distribution.  If a
   network entity has already obtained its security configuration via
   other mechanisms, then it MUST NOT request security policy via iSNS.

7.5.  Resource Issues

   The iSNS protocol is lightweight and will not generate a significant
   amount of traffic.  iSNS traffic is characterized by occasional
   registration, notification, and update messages that do not consume
   significant amounts of bandwidth.  Even software-based IPSec
   implementations should not have a problem handling the traffic loads
   generated by the iSNS protocol.

   To fulfill iSNS security requirements, the only additional resources
   needed beyond what is already required for iSCSI and iFCP involve the
   iSNS server.  Because iSCSI and iFCP end nodes are already required
   to implement IKE and IPSec, these existing requirements can also be
   used to fulfill IKE and IPSec requirements for iSNS clients.

7.6.  iSNS Interaction with IKE and IPSec

   When IPSec security is enabled, each iSNS client with at least one
   Storage Node that is registered in the iSNS database SHALL maintain
   at least one phase-1 security association with the iSNS server.  All
   iSNS protocol messages between iSNS clients and the iSNS server SHALL
   be protected by a phase-2 security association.

   When a Network Entity is removed from the iSNS database, the iSNS
   server SHALL send a phase-1 delete message to the associated iSNS
   client IKE peer, and tear down all phase-1 and phase-2 SAs associated
   with that iSNS client.

8.  IANA Considerations

   The well-known TCP and UDP port number for iSNS is 3205.

   The standards action of this RFC creates two registries to be
   maintained by IANA in support of iSNSP and assigns initial values for
   both registries.  The first registry is of Block Storage Protocols
   supported by iSNS.  The second registry is a detailed registry of
   standard iSNS attributes that can be registered to and queried from
   the iSNS server.  Note that this RFC uses the registry created for
   Block Structure Descriptor (BSD) in Section 15 of Service Location
   Protocol, Version 2 [RFC2608].

8.1.  Registry of Block Storage Protocols

   In order to maintain a registry of block storage protocols supported
   by iSNSP, IANA will assign a 32-bit unsigned integer number for each
   block storage protocol supported by iSNS.  This number is stored in
   the iSNS database as the Entity Protocol.  The initial set of values
   to be maintained by IANA for Entity Protocol is indicated in the

   table in Section 6.2.2.  Additional values for new block storage
   protocols to be supported by iSNS SHALL be assigned by the IPS WG
   Chairperson, or by a Designated Expert [RFC2434] appointed by the
   IETF Transport Area Director.

8.2.  Registry of Standard iSNS Attributes

   IANA is responsible for creating and maintaining the Registry of
   Standard iSNS Attributes.  The initial list of iSNS attributes is
   described in Section 6.  For each iSNS attribute this information
   MUST include, its tag value, the attribute length, and the tag values
   for the set of permissible registration and query keys that can be
   used for that attribute.  The initial list of iSNS attributes to be
   maintained by IANA is indicated in Section 6.1.

   Additions of new standard attributes to the Registry of Standard iSNS
   Attributes SHALL require IETF Consensus [RFC2434].  The RFC required
   for this process SHALL specify use of tag values reserved for IANA
   allocation in Section 6.1.  The RFC SHALL specify as a minimum, the
   new attribute tag value, attribute length, and the set of permissible
   registration and query keys that can be used for the new attribute.
   The RFC SHALL also include a discussion of the reasons for the new
   attribute(s) and how the new attribute(s) are to be used.

   As part of the process of obtaining IETF Consensus, the proposed RFC
   and its supporting documentation SHALL be made available to the IPS
   WG mailing list or, if the IPS WG is disbanded at the time, to a
   mailing list designated by the IETF Transport Area Director.  The
   review and comment period SHALL last at least three months before the
   IPS WG Chair or a person designated by the IETF Transport Area
   Director decides either to reject the proposal or to forward the
   draft to the IESG for publication as an RFC.  When the specification
   is published as an RFC, then IANA will register the new iSNS
   attribute(s) and make the registration available to the community.

8.3.  Block Structure Descriptor (BSD) Registry

   Note that IANA is already responsible for assigning and maintaining
   values used for the Block Structure Descriptor for the iSNS
   Authentication Block (see Section 5.5).  Section 15 of [RFC2608]
   describes the process for allocation of new BSD values.

9.  Normative References

   [iSCSI]      Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M.,
                and E. Zeidner, "Internet Small Computer Systems
                Interface (iSCSI)", RFC 3720, April 2004.

   [iFCP]       Monia, C., Mullendore, R., Travostino, F., Jeong, W.,
                and M. Edwards, "iFCP - A Protocol for Internet Fibre
                Channel Storage Networking", RFC 4172, September 2005.

   [iSNSOption] Monia, C., Tseng, J., and K. Gibbons, The IPv4 Dynamic
                Host Configuration Protocol (DHCP) Option for the
                Internet Storage Name Service, RFC 4174, September 2005.

   [RFC2608]    Guttman, E., Perkins, C., Veizades, J., and M. Day,
                "Service Location Protocol, Version 2 ", RFC 2608, June
                1999.

   [iSCSI-SLP]  Bakke, M., Hufferd, J., Voruganti, K., Krueger, M., and
                T. Sperry, "Finding Internet Small Computer Systems
                Interface (iSCSI) Targets and Name Servers by Using
                Service Location Protocol version 2 (SLP), RFC 4018,
                April 2005.

   [iSCSI-boot] Sarkar, P., Missimer, D., and C. Sapuntzakis,
                "Bootstrapping Clients using the Internet Samll Computer
                System Interface (iSCSI) Protocol", RFC 4173, September
                2005.

   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [STRINGPREP] Bakke, M., "String Profile for Internet Small Computer
                Systems Interface (iSCSI) Names", RFC 3722, April 2004.

   [NAMEPREP]   Hoffman, P. Nameprep: A Stringprep Profile for
                Internationalized Domain Names, July 2002.

   [RFC2407]    Piper, D., "The Internet IP Security Domain of
                Interpretation for ISAKMP", RFC 2407, November 1998.

   [RFC2408]    Maughan, D., Schertler, M., Schneider, M., and J.
                Turner, "Internet Security Association and Key
                Management Protocol (ISAKMP)", RFC 2408, November 1998.

   [RFC2409]    Harkins, D. and D. Carrel, "The Internet Key Exchange
                (IKE)", RFC 2409, November 1998.

   [EUI-64]     Guidelines for 64-bit Global Identifier (EUI-64)
                Registration Authority, May 2001, IEEE

   [RFC3279]    Bassham, L., Polk, W., and R. Housley, "Algorithms and
                Identifiers for the Internet X.509 Public Key
                Infrastructure Certificate and Certificate Revocation
                List (CRL) Profile", RFC 3279, April 2002.

   [RFC3280]    Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
                X.509 Public Key Infrastructure Certificate and
                Certificate Revocation List (CRL) Profile", RFC 3280,
                April 2002.

   [802-1990]   IEEE Standards for Local and Metropolitan Area Networks:
                Overview and Architecture, Technical Committee on
                Computer Communications of the IEEE Computer Society,
                May 31, 1990

   [FC-FS]      Fibre Channel Framing and Signaling Interface, NCITS
                Working Draft Project 1331-D

10.  Informative References

   [iSNSMIB]    Gibbons, K., et al., "Definitions of Managed Objects for
                iSNS (Internet Storage name Service)", Work in Progress,
                July 2003.

   [X.509]      ITU-T Recommendation X.509 (1997 E): Information
                Technology - Open Systems Interconnection - The
                Directory: Authentication Framework, June 1997

   [FC-GS-4]    Fibre Channel Generic Services-4 (work in progress),
                NCITS Working Draft Project 1505-D

   [RFC1510]    Kohl, J. and C. Neuman, "The Kerberos Network
                Authentication Service (V5)", RFC 1510, September 1993.

   [RFC2025]    Adams, C., "The Simple Public-Key GSS-API Mechanism
                (SPKM)", RFC 2025, October 1996.

   [RFC2434]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
                IANA Considerations Section in RFCs", BCP 26, RFC 2434,
                October 1998.

   [RFC2945]    Wu, T., "The SRP Authentication and Key Exchange
                System", RFC 2945, September 2000.

   [RFC1994]    Simpson, W., "PPP Challenge Handshake Authentication
                Protocol (CHAP)", RFC 1994, August 1996.

   [RFC2131]    Droms, R., "Dynamic Host Configuration Protocol", RFC
                2131, March 1997.

   [RFC3410]    Case, J., Mundy, R., Partain, D., and B. Stewart,
                "Introduction and Applicability Statements for
                Internet-Standard Management Framework", RFC 3410,
                December 2002.

   [RFC3411]    Harrington, D., Presuhn, R., and B. Wijnen, "An
                Architecture for Describing Simple Network Management
                Protocol (SNMP) Management Frameworks", STD 62, RFC
                3411, December 2002.

Appendix A: iSNS Examples

A.1.  iSCSI Initialization Example

   This example assumes an SLP Service Agent (SA) has been implemented
   on the iSNS host, and an SLP User Agent (UA) has been implemented on
   the iSNS initiator.  See [RFC2608] for further details on SAs and
   UAs.  This example also assumes that the target is configured to use
   the iSNS server, and have its access control policy subordinated to
   the iSNS server.

A.1.1.  Simple iSCSI Target Registration

   In this example, a simple target with a single iSCSI name registers
   with the iSNS server.  The target is represented in the iSNS by an
   Entity containing one Storage Node, one Portal, and an implicitly
   registered Portal Group that provides a relationship between the
   Storage Node and Portal.  The target has not been assigned a Fully
   Qualified Domain Name (FQDN) by the administrator.  In this example,
   because a PG object is not explicitly registered, a Portal Group with
   a PGT of 1 is implicitly registered.  In this example SLP is used to
   discover the location of the iSNS Server.  An alternative is to use
   the iSNS DHCP option [iSNSOption] to discover the iSNS server.

   +--------------------------+------------------+-------------------+
   |    iSCSI Target Device   |    iSNS Server   |Management Station |
   +--------------------------+------------------+-------------------+
   |Discover iSNS--SLP------->|                  |/*mgmt station is  |
   |                          |<--SLP--iSNS Here:| administratively  |
   |                          |      192.0.2.100 | authorized to view|
   |                          |                  | all DDs.  Device  |
   |      DevAttrReg--------->|                  | NAMEabcd was      |
   |Src:(tag=32) "NAMEabcd"   |                  | previously placed |
   |Key: <none present>       |                  | into DDabcd along |
   |Oper Attrs:               |                  | with devpdq and   |
   |tag=1: NULL               |                  | devrst.           |
   |tag=2: "iSCSI"            |                  |                   |
   |tag=16: 192.0.2.5         |                  |                   |
   |tag=17: 5001              |                  |                   |
   |tag=32: "NAMEabcd"        |                  |                   |
   |tag=33: target            |                  |                   |
   |tag=34: "disk 1"          |                  |                   |
   |                          |<---DevAttrRegRsp |                   |
   |                          |SUCCESS           |                   |
   |                          |Key:(tag=1) "isns:0001"               |
   |                          |Oper Attrs:       |                   |
   |                          |tag=1: "isns:0001"|                   |
   |                          |tag=2: "iSCSI"    |                   |

   |                          |tag=16: 192.0.2.5 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32: "NAMEabcd"|/* previously      |
   |                          |tag=33: target    | placed in a DD */ |
   |                          |tag=34: "disk 1"  |                   |
   |                          |                  |                   |
   |                          |      SCN-------->|                   |
   |                          |(or SNMP notification)                |
   |                          |dest:(tag=32):"MGMTname1"             |
   |                          |time:(tag=4): <current time>          |
   |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
   |                          |tag=32: "NAMEabcd"|                   |
   |                          |                  |<-------SCNRsp     |
   |      DevAttrQry--------->|                  |                   |
   |Src:(tag=32) "NAMEabcd"   |                  |                   |
   |Key:(tag=33) "initiator"  |                  |                   |
   |Oper Attrs:               |                  |                   |
   |tag=16:  NULL             |                  |                   |
   |tag=17:  NULL             |                  |                   |
   |tag=32:  NULL             |                  |                   |
   |/*Query asks for all initr|                  |                   |
   |devices' IP address, port |<---DevAttrQryRsp |                   |
   |number, and Name*/        |SUCCESS           |                   |
   |                          |tag=16:192.0.2.1  |                   |
   |                          |tag=17:50000      |                   |
   |                          |tag=32:"devpdq"   |                   |
   |                          |tag=16:192.0.2.2  |                   |
   |                          |tag=17:50000      |                   |
   |                          |tag=32:"devrst"   |                   |
   |/*************************|                  |<-----DevAttrQry   |
   |Our target "NAMEabcd"     |                  |src: "MGMTname1"   |
   |discovers two initiators  |                  key:(tag=32)"NAMEabcd"
   |in shared DDs.  It will   |                  |Op Attrs:          |
   |accept iSCSI logins from  |                  |tag=16:  NULL      |
   |these two identified      |                  |tag=17:  NULL      |
   |initiators presented by   |                  |tag=32:  NULL      |
   |iSNS                      |                  |                   |
   |*************************/| DevAttrQryRsp--->|                   |
   |                          |SUCCESS           |                   |
   |                          |tag=16: 192.0.2.5 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32: "NAMEabcd"|                   |
   +--------------------------+------------------+-------------------+

A.1.2.  Target Registration and DD Configuration

   In this example, a more complex target, with two Storage Nodes and
   two Portals using ESI monitoring, registers with the iSNS.  This
   target has been configured with a Fully Qualified Domain Name (FQDN)
   in the DNS servers, and the user wishes to use this identifier for
   the device.  The target explicitly registers Portal Groups to
   describe how each Portal provides access to each Storage Node.  One
   target Storage Node allows coordinated access through both Portals.
   The other Storage Node allows access, but not coordinated access,
   through both Portals.

   +--------------------------+------------------+-------------------+
   |    iSCSI Target Device   |    iSNS Server   |Management Station |
   +--------------------------+------------------+-------------------+
   |Discover iSNS--SLP-->     |                  |/*mgmt station is  |
   |                          |<--SLP--iSNS Here:| administratively  |
   |                          |      192.0.2.100 | authorized to view|
   | DevAttrReg-->            |                  | all DDs */        |
   |Src:                      |                  |                   |
   |tag=32: "NAMEabcd"        |                  |                   |
   |Msg Key:                  |                  |                   |
   |tag=1: "jbod1.example.com"|                  |                   |
   |Oper Attrs:               |                  |                   |
   |tag=1: "jbod1.example.com"|                  |                   |
   |tag=2: "iSCSI"            |                  |                   |
   |tag=16: 192.0.2.4         |                  |                   |
   |tag=17: 5001              |                  |                   |
   |tag=19: 5                 |                  |                   |
   |tag=20: 5002              |                  |                   |
   |tag=16: 192.0.2.5         |                  |                   |
   |tag=17: 5001              |                  |                   |
   |tag=19: 5                 |                  |                   |
   |tag=20: 5002              |                  |                   |
   |tag=32: "NAMEabcd"        |                  |                   |
   |tag=33: "Target"          |                  |                   |
   |tag=34: "Storage Array 1" |                  |                   |
   |tag=51: 10                |                  |                   |
   |tag=49: 192.0.2.4         |                  |                   |
   |tag=50: 5001              |                  |                   |
   |tag=49: 192.0.2.5         |                  |                   |
   |tag=50: 5001              |                  |                   |
   |tag=32: "NAMEefgh"        |                  |                   |
   |tag=33: "Target"          |                  |                   |
   |tag=34: "Storage Array 2" |/*****************|                   |
   |tag=51: 20                |jbod1.example.com is                  |
   |tag=49: 192.0.2.4         |now registered in |                   |
   |tag=50: 5001              |iSNS, but is not  |                   |

   |tag=51: 30                |in any DD. Therefore,                 |
   |tag=49: 192.0.2.5         |no other devices  |                   |
   |tag=50: 5001              |can "see" it.     |                   |
   |                          |*****************/|                   |
   |                          |<--DevAttrRegRsp  |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=1: "jbod1.example.com"            |
   |                          |Oper Attrs:       |                   |
   |                          |tag=1: "jbod1.example.com"            |
   |                          |tag=2: "iSCSI"    |                   |
   |                          |tag=16: 192.0.2.4 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=19: 5         |                   |
   |                          |tag=20: 5002      |                   |
   |                          |tag=16: 192.0.2.5 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=19: 5         |                   |
   |                          |tag=20: 5002      |                   |
   |                          |tag=32: "NAMEabcd"|                   |
   |                          |tag=33: "Target"  |                   |
   |                          |tag=34: "Storage Array 1"             |
   |                          |tag=48: "NAMEabcd"|                   |
   |                          |tag=49: 192.0.2.4 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 10        |                   |
   |                          |tag=48: "NAMEabcd"|                   |
   |                          |tag=49: 192.0.2.5 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 10        |                   |
   |                          |tag=32: "NAMEefgh"|                   |
   |                          |tag=33: "Target"  |                   |
   |                          |tag=34: "Storage Array 2"             |
   |                          |tag=43: X.509 cert|                   |
   |                          |tag=48: "NAMEefgh"|                   |
   |                          |tag=49: 192.0.2.4 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 20        |                   |
   |                          |tag=48: "NAMEefgh"|                   |
   |                          |tag=49: 192.0.2.5 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 30        |                   |
   |                          |                  |                   |
   |                          | SCN------>       |                   |
   |                          | (or SNMP notification)               |
   |                          |dest:(tag=32)"mgmt.example.com"       |
   |                          |time:(tag=4): <current time>          |
   |                          |tag=35: "MGT-SCN, OBJ-ADD"            |

   |                          |tag=32: "NAMEabcd"|                   |
   |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
   |                          |tag=32: "NAMEefgh"|                   |
   |                          |                  |<--SCNRsp          |
   |                          |                  |SUCCESS            |
   |                          |             tag=32:"mgmt.example.com"|
   |                          |                  |                   |
   |                          |                  |<--DevAttrQry      |
   |                          |                  |Src:               |
   |                          |               tag=32:"mgmt.example.com"
   |                          |                  |Msg Key:           |
   |                          |                  |tag=32: "NAMEabcd" |
   |                          |                  |Oper Attrs:        |
   |                          |                  |tag=16: <0-length> |
   |                          |                  |tag=17: <0-length> |
   |                          |                  |tag=32: <0-length> |
   |                          |                  |                   |
   |                          | DevAttrQryRsp--> |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=32: "NAMEabcd"|                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=16: 192.0.2.4 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32:"NAMEabcd" |                   |
   |                          |tag=16: 192.0.2.5 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32:"NAMEabcd" |                   |
   |                          |                  |Src:               |
   |                          |               tag=32:"mgmt.example.com"
   |                          |                  |Msg Key:           |
   |                          |                  |tag=32: "NAMEefgh" |
   |                          |                  |Oper Attrs:        |
   |                          |                  |tag=16: <0-length> |
   |                          |                  |tag=17: <0-length> |
   |                          |                  |tag=32: <0-length> |
   |                          |                  |                   |
   |                          | DevAttrQryRsp--> |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=32: "NAMEefgh"|                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=16: 192.0.2.4 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32:"NAMEefgh" |                   |
   |                          |tag=16: 192.0.2.5 |/**Mgmt Station ***|
   |                          |tag=17: 5001      |displays device,   |
   |                          |tag=32:"NAMEefgh" |the operator decides

   |                          |                  |to place "NAMEabcd"|
   |                          |                  |into Domain "DDxyz"|
   |/*************************|                  |******************/|
   |Target is now registered  |                  |                   |
   |in iSNS. It is then placed|                  |<--DDReg           |
   |in a pre-existing DD with |                  |Src:               |
   |DD_ID 123 by a management |               tag=32:"mgmt.example.com"
   |station.                  |                  |Msg Key:           |
   |*************************/|                  |tag=2065: 123      |
   |                          |                  |Oper Attrs:        |
   |                          |                  |tag=2068: "NAMEabcd"
   |                          | DDRegRsp----->   |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=2065: 123     |                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=2065: 123     |                   |
   +--------------------------+------------------+-------------------+

A.1.3.  Initiator Registration and Target Discovery

   The following example illustrates a new initiator registering with
   the iSNS, and discovering the target NAMEabcd from the example in
   A.1.2.

   +--------------------------+------------------+-------------------+
   |    iSCSI Initiator       |    iSNS          |Management Station |
   +--------------------------+------------------+-------------------+
   |Discover iSNS--SLP-->     |                  |/*mgmt station is  |
   |                          |<--SLP--iSNS Here:| administratively  |
   |                          |      192.36.53.1 | authorized to view|
   |DevAttrReg-->             |                  | all DDs ********/ |
   |Src:                      |                  |                   |
   |tag=32: "NAMEijkl"        |                  |                   |
   |Msg Key:                  |                  |                   |
   |tag=1: "svr1.example.com" |                  |                   |
   |Oper Attrs:               |                  |                   |
   |tag=1: "svr1.example.com" |                  |                   |
   |tag=2: "iSCSI"            |                  |                   |
   |tag=16: 192.20.3.1        |/*****************|                   |
   |tag=17: 5001              |Device not in any |                   |
   |tag=19: 5                 |DD, so it is      |                   |
   |tag=20: 5002              |inaccessible by   |                   |
   |tag=32: "NAMEijkl"        |other devices     |                   |
   |tag=33: "Initiator"       |*****************/|                   |
   |tag=34: "Server1"         |                  |                   |
   |tag=51: 11                |                  |                   |
   |tag=49: 192.20.3.1        |                  |                   |

   |tag=50: 5001              |                  |                   |
   |                          |<--DevAttrRegRsp  |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=1: "svr1.example.com"             |
   |                          |Oper Attrs:       |                   |
   |                          |tag=1: "svr1.example.com"             |
   |                          |tag=2: "iSCSI"    |                   |
   |                          |tag=16: 192.20.3.1|                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=19: 5         |                   |
   |                          |tag=20: 5002      |                   |
   |                          |tag=32: "NAMEijkl"|                   |
   |                          |tag=33: "Initiator"                   |
   |                          |tag=34: "Server1" |                   |
   |                          |tag=48: "NAMEijkl"|                   |
   |                          |tag=49: 192.20.3.1|                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 11        |                   |
   |                          |                  |                   |
   |                          |       SCN------> |                   |
   |                          |  (or SNMP notification)              |
   |                          |dest:(tag=32)"mgmt.example.com"       |
   |                          |time:(tag=4): <current time>          |
   |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
   |                          |tag=32: "NAMEijkl"|                   |
   |                          |                  |                   |
   |                          |                  |<------SCNRsp      |
   |                          |                  |SUCCESS            |
   |                          |               tag=32:"mgmt.example.com"
   |                          |                  |                   |
   |SCNReg-->                 |                  |                   |
   |Src:                      |                  |                   |
   |tag=32: "NAMEijkl"        |                  |                   |
   |Msg Key:                  |                  |                   |
   |tag=32: "NAMEijkl"        |                  |                   |
   |Oper Attrs:               |                  |                   |
   |tag=35: <TARG&SELF, OBJ-RMV/ADD/UPD>         |                   |
   |                          |<--SCNRegRsp      |                   |
   |                          |SUCCESS           |                   |
   |                          |                  |                   |
   |                          |                  |<----DevAttrQry    |
   |                          |                  |Src:               |
   |                          |               tag=32:"mgmt.example.com"
   |                          |                  |Msg Key:           |
   |                          |                  |tag=32: "NAMEijkl" |
   |                          |                  |Oper Attrs:        |
   |                          |                  |tag=16: <0-length> |

   |                          |                  |tag=17: <0-length> |
   |                          |                  |tag=32: <0-length> |
   |                          | DevAttrQryRsp--->|                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=32: "NAMEijkl"|                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=16:192.20.3.1 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32:"NAMEijkl" |                   |
   |                          |                  |/**Mgmt Station ***|
   |                          |                  |displays device, the
   |                          |                  |operator decides to|
   |                          |                  |place "NAMEijkl" into
   |                          |                  |pre-existing Disc  |
   |                          |                  |Domain "DDxyz" with|
   |                          |                  |device NAMEabcd    |
   |                          |                  |******************/|
   |                          |                  |<--DDReg           |
   |                          |                  |Src:               |
   |                          |               tag=32:"mgmt.example.com"
   |                          |                  |Msg Key:           |
   |                          |                  |tag=2065: 123      |
   |                          |                  |Oper Attrs:        |
   |                          |                  |tag=2068: "NAMEijkl"
   |                          |                  |                   |
   |                          |     DDRegRsp---->|                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=2065: 123     |                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=2065: 123     |/******************|
   |                          |                  |"NAMEijkl" has been|
   |                          |                  |moved to "DDxyz"   |
   |                          |                  |******************/|
   |                          |        SCN------>|                   |
   |                          |dest:(tag=32)"mgmt.example.com"       |
   |                          |time:(tag=4): <current time>          |
   |                          |tag=35: <MGT-SCN, DD/DDS-MBR-ADD>     |
   |                          |tag=2065: 123     |                   |
   |                          |tag=2068: "NAMEijkl"                  |
   |                          |                  |                   |
   |                          |                  |<------SCNRsp      |
   |                          |                  |SUCCESS            |
   |                          |               tag=32:"mgmt.example.com"
   |                          |<-----SCN         |                   |
   |                          |dest:(tag=32)"NAMEijkl"               |
   |                          |time:(tag=4): <current time>          |

   |                          |tag=35: <TARG&SELF, OBJ-ADD>          |
   |                          |tag=32: "NAMEijkl"|                   |
   |    SCNRsp------>         |                  |                   |
   |SUCCESS                   |                  |                   |
   |tag=32:"NAMEijkl"         |                  |                   |
   |                          |                  |                   |
   |                          |/*****************|                   |
   |                          |Note that NAMEabcd|                   |
   |                          |also receives an  |                   |
   |                          |SCN that NAMEijkl |                   |
   |                          |is in the same DD |                   |
   |                          |*****************/|                   |
   |           (to "NAMEabcd")|<-----SCN         |                   |
   |                          |dest:(tag=32)"NAMEabcd"               |
   |                          |time:(tag=4): <current time>          |
   |                          |tag=35: <INIT&SELF, OBJ-ADD>          |
   |                          |tag=32: "NAMEijkl"|                   |
   |    SCNRsp------>         |                  |                   |
   |SUCCESS                   |                  |                   |
   |tag=32:"NAMEabcd"         |                  |                   |
   |                          |                  |                   |
   |    DevAttrQry----------->|                  |                   |
   |Src:                      |                  |                   |
   |tag=32: "NAMEijkl"        |                  |                   |
   |Msg Key:                  |                  |                   |
   |tag=33: "Target"          |                  |                   |
   |Oper Attrs:               |                  |                   |
   |tag=16: <0-length>        |                  |                   |
   |tag=17: <0-length>        |                  |                   |
   |tag=32: <0-length>        |                  |                   |
   |tag=34: <0-length>        |                  |                   |
   |tag=43: <0-length>        |                  |                   |
   |tag=48: <0-length>        |                  |                   |
   |tag=49: <0-length>        |                  |                   |
   |tag=50: <0-length>        |                  |                   |
   |tag=51: <0-length>        |                  |                   |
   |                          |<--DevAttrQryRsp  |                   |
   |                          |SUCCESS           |                   |
   |                          |Msg Key:          |                   |
   |                          |tag=33:"Target"   |                   |
   |                          |Oper Attrs:       |                   |
   |                          |tag=16: 192.0.2.4 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32: "NAMEabcd"|                   |
   |                          |tag=34: "Storage Array 1"             |
   |                          |tag=16: 192.0.2.5 |                   |
   |                          |tag=17: 5001      |                   |
   |                          |tag=32: "NAMEabcd"|                   |

   |                          |tag=34: "Storage Array 1"             |
   |                          |tag=43: X.509 cert|                   |
   |                          |tag=48: "NAMEabcd"|                   |
   |                          |tag=49: 192.0.2.4 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 10        |                   |
   |                          |tag=48: "NAMEabcd"|                   |
   |                          |tag=49: 192.0.2.5 |                   |
   |                          |tag=50: 5001      |                   |
   |                          |tag=51: 10        |                   |
   |                          |                  |                   |
   |/***The initiator has discovered             |                   |
   |the target, and has everything               |                   |
   |needed to complete iSCSI login               |                   |
   |The same process occurs on the               |                   |
   |target side; the SCN prompts the             |                   |
   |target to download the list of               |                   |
   |authorized initiators from the               |                   |
   |iSNS (i.e., those initiators in the          |                   |
   |same DD as the target.************/          |                   |
   +--------------------------+------------------+-------------------+

Acknowledgements

   Numerous individuals contributed to the creation of this document
   through their careful review and submissions of comments and
   recommendations.  We acknowledge the following persons for their
   technical contributions to this document: Mark Bakke (Cisco), John
   Hufferd (IBM), Julian Satran (IBM), Kaladhar Voruganti(IBM), Joe Czap
   (IBM), John Dowdy (IBM), Tom McSweeney (IBM), Jim Hafner (IBM), Chad
   Gregory (Intel), Yaron Klein (Sanrad), Larry Lamers (Adaptec), Jack
   Harwood (EMC), David Black (EMC), David Robinson (Sun), Alan Warwick
   (Microsoft), Bob Snead (Microsoft), Fa Yoeu (Intransa), Joe White
   (McDATA), Charles Monia (McDATA), Larry Hofer (McDATA), Ken Hirata
   (Vixel), Howard Hall (Pirus), Malikarjun Chadalapaka (HP), Marjorie
   Krueger (HP), Siva Vaddepuri (McDATA), and Vinai Singh (American
   Megatrends).

Authors' Addresses

   Josh Tseng
   Riverbed Technology
   501 2nd Street, Suite 410
   San Francisco, CA 94107

   Phone:  (650)274-2109
   EMail:  joshtseng@yahoo.com

   Kevin Gibbons
   McDATA Corporation
   4555 Great America Parkway
   Santa Clara, CA 95054-1208

   Phone: (408) 567-5765
   EMail: kevin.gibbons@mcdata.com

   Franco Travostino
   Nortel
   600 Technology Park Drive
   Billerica, MA 01821 USA

   Phone: (978) 288-7708
   EMail: travos@nortel.com

   Curt du Laney
   Rincon Research Corporation
   101 North Wilmot Road, Suite 101
   Tucson AZ 85711

   Phone: (520) 519-4409
   EMail: cdl@rincon.com

   Joe Souza
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052-6399

   Phone: (425) 706-3135
   EMail: joes@exmsft.com

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