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RFC 2602 - ILMI-Based Server Discovery for MARS

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Network Working Group                                       M. Davison
Request for Comments: 2602                               Cisco Systems
Category: Standards Track                                    June 1999

                  ILMI-Based Server Discovery for MARS

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 (1999).  All Rights Reserved.


   This memo defines how ILMI-based Server Discovery, which provides a
   method for ATM-attached hosts and routers to dynamically determine
   the ATM addresses of servers, shall be used to locate MARS servers.

1. Introduction

   Presently, configuring a host or router to use MARS [1] is cumbersome
   and error-prone since it requires at least one ATM address to be
   statically configured on each host or router in the network.
   Further, it is impossible to implement a diskless host to use MARS
   since local configuration is required.  ILMI-based Server Discovery,
   hereafter referred to as "server discovery," provides a solution to
   these problems.

   A brief overview of the Integrated Local Management Interface (ILMI)
   and the Service Registry MIB, as defined by the ATM Forum, are
   provided in this memo. The reader should consult [2] for a complete
   description of ILMI and this MIB, but the information contained here
   is sufficient for an understanding of its use to support MARS server

2. Integrated Local Management Interface

   The Integrated Local Management Interface (ILMI) [2] provides a
   mechanism for ATM-attached devices, such as hosts, routers, and ATM
   switches, to transfer management information. It is based on the
   Simple Network Management Protocol (SNMP), Version 1, and supports
   get, get-next, set and trap operations.

   The ILMI specification designates the switch side of the ATM link as
   the 'network side' and the host/router side of the ATM link as the '
   user side.' The Service Registry MIB, which is outlined in Section 3,
   is implmented on the network side and is queried from the user side.

3. ILMI 4.0 Service Registry MIB

   Server discovery utilizes the Service Registry MIB defined by the ATM
   Forum in ILMI Specification Version 4.0 [2]. To support the existing
   framework for IP over ATM, as embodied by ATMARP and MARS, ATM
   switches must support the Service Registry MIB.

   A row in the service registry table [2] is defined as:

              AtmfSrvcRegEntry ::= SEQUENCE {
                  atmfSrvcRegPort          INTEGER,
                  atmfSrvcRegServiceID     OBJECT IDENTIFIER,
                  atmfSrvcRegATMAddress    AtmAddress,
                  atmfSrvcRegAddressIndex  INTEGER,
                  atmfSrvcRegParm1         OCTET STRING

The definition of each field in this structure is:

      atmfSrvcRegPort - The ATM port number for which this entry
          contains management information. The value of zero may be used
          to indicate the ATM interface over which a management request
          was received.

      atmfSrvcRegServiceID - This is the service identifier that
          uniquely identifies the type of service at the address
          provided in the table. (See Section 3.2 for MARS OID.)

      atmfSrvcRegATMAddress - This is the full address of the service.
          The ATM client will use this address to establish a connection
          with the service.

      atmfSrvcRegAddressIndex - An arbitrary integer to differentiate
          multiple rows containing different ATM addresses for the same
          service on the same port.

      atmfSrvcRegParm1 - An octet string whose size and meaning is
          determined by the value of atmfSrvcRegServiceID.

   The service registry table is indexed by atmfSrvcRegPort,
   atmfSrvcRegServiceID and atmfSrvcRegAddressIndex.

3.1 Service Parameter String

   A generic parameter string is defined in the service registry table,
   thus allowing protocol-specific parameters to be specified. To be
   consistent with [1], the parameter string for MARS shall be:

       mar$pro.type   16   bits     Protocol type
       mar$pro.snap   40   bits     Optional extension to protocol type
       mar$plen        8   bits     Length of protocol address
       mar$addr       plen octets   Network address
       mar$mask       plen octets   Network mask


       mar$pro.type   - See [1]. (IPv4 is 0x0800, IPv6 is 0x86DD)

       mar$pro.snap   - See [1]. (IPv4 and IPv6 are 0)

       mar$plen       - Length of the protocol address.
                        (IPv4 is 4, IPv6 is 16)

       mar$addr       - Network address represented in network byte

       mar$mask       - Network mask represented in network byte order

3.2 Service Object Identifier

   This OID, assigned in the ATM Forum Service Registry MIB, names MARS
   within the context of server discovery.

     atmfSrvcRegMARS   OBJECT IDENTIFIER ::= { }

   It does not name any managed objects, rather is used to locate
   appropriate rows in the service registery table.

4. MARS Client Behavior

   A MARS client will access the service registry table via ILMI using
   the SNMP GetNext operator to "sweep" (SNMP parlance for a linear
   search) beginning with {Port = 0, ServiceID = <see Section 3.2>,
   Index = 0} while holding the port number and the serviceID constant.

   (Port number 0 is used within ILMI to indicate "this port.")

   An MARS client with no local configuration, such as a diskless
   workstation, must use the row with the lowest index value if multiple
   MARS servers, possibly for multiple networks, are listed.

   MARS clients that have local IP configuration must use a row that has
   the appropriate IP address.  For example, consider the case where an
   IP router has 3 logical interfaces defined on a single physical
   interface with IP addresses, and The router will sweep the service registry table
   looking for rows that have atmfSrvcRegParm1 values as shown below:

     Net number/mask  atmfSrvcRegParm1
     ---------------- --------------------------------------------------        08 00 00 00 00 00 00  04  01 00 00 00  ff 00 00 00    08 00 00 00 00 00 00  04  80 0a 00 00  ff ff 00 00  08 00 00 00 00 00 00  04  ab 45 96 00  ff ff ff 00

   When the correct atmfSrvcRegParm1 values are located, the router may
   then establish an SVC to the selected server and perform the
   appropriate protocol operations.

   Redundant MARS servers are supported with multiple rows in the
   service registry table. This list of MARS servers is ordered with the
   primary MARS server having the lowest index value. The MARS client
   must attempt to utilize the primary MARS server before utilizing a
   secondary MARS server. Administrators must ensure that the listed
   MARS servers are synchronized.

5. MARS Server Behavior

   An MARS server shall be locally configured. The MARS server may
   retrieve the MARS service registry data to validate the results. If
   an incorrect row is retrieved the error may be flagged in a locally
   significant way.

6. Relationship with PNNI Augmented Routing

   An augmented version PNNI ("PNNI Augmented Routing," or PAR) [3] has
   been developed by the ATM Forum. PAR can distribute data such as MARS
   server addresses. Further, the ATM Forum is developing a proxy
   mechanism for PAR (Proxy PAR) that would allow a UNI-attached host or
   router to access PAR data without a full PAR implementation.

   These mechanisms offer a promising way to manage the service registry
   tables maintained on each switch in an ATM network, yet would not
   require changes to the mechanism defined in this memo. Hosts and
   routers can continue to utilize ILMI-based or Proxy PAR-based server
   discovery and network administrators could manage the service
   registry data with local configuration or via PAR and Proxy PAR.

7. Security Considerations

   The server discovery mechanism is built on the ILMI managment
   framework and the security embodied in that framework. Access, to
   user- or network-side information is controlled by MIB design rather
   than protocol security mechanisms.

   The service registery MIB, the table containing information for
   server discovery, is defined in [2] with read-only access. This means
   that any user-side device may query the service registry, but may not
   modify the service registry via ILMI. Instead, the sevice registry
   table must be modified via local configuration on the ATM switch.


   [1]  Armitage, G., "Support for Multicast over UNI 3.0/3.1 based ATM
        Networks", RFC 2022, November 1996.

   [2]  ATM Forum, "Integrated Local Management Interface (ILMI)
        Specification Version 4.0," af-ilmi-0065.000, September 1996.

   [3]  ATM Forum, "PNNI Augmented Routing (PAR) Version 1.0," af-ra-
        0104, January 1999.

Author's  Address

   Mike Davison
   Cisco Systems
   170 West Tasman Drive
   San Jose, California 95134

   Phone: (408) 526-4000
   EMail: mike.davison@cisco.com

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