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RFC 5414 - Wireless LAN Control Protocol (WiCoP)


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Independent Submission                                           S. Iino
Request for Comments: 5414                                   S. Govindan
Obsoleted by: 5415                                            M. Sugiura
Category: Historic                                              H. Cheng
ISSN: 2070-1721                                                Panasonic
                                                           February 2010

                 Wireless LAN Control Protocol (WiCoP)

Abstract

   The popularity of wireless local area networks (WLANs) has led to
   widespread deployments across different establishments.  It has also
   translated into an increasing scale of the WLANs.  Large-scale
   deployments made of large numbers of wireless termination points
   (WTPs) and covering substantial areas are increasingly common.

   The Wireless LAN Control Protocol (WiCoP) described in this document
   allows for the control and provisioning of large-scale WLANs.  It
   enables central management of these networks and realizes the
   objectives set forth for the Control And Provisioning of Wireless
   Access Points (CAPWAP).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for the historical record.

   This document defines a Historic Document for the Internet community.
   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5414.

IESG Note

   This RFC documents the WiCoP protocol as it was when submitted to the
   IETF as a basis for further work in the CAPWAP Working Group, and
   therefore it may resemble the CAPWAP protocol specification in RFC
   5415, as well as other IETF work.  This RFC is being published solely
   for the historical record.  The protocol described in this RFC has
   not been thoroughly reviewed and may contain errors and omissions.

   RFC 5415 documents the standards track solution for the CAPWAP
   Working Group and obsoletes any and all mechanisms defined in this
   RFC.  This RFC itself is not a candidate for any level of Internet
   Standard and should not be used as a basis for any sort of Internet
   deployment.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http:trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1. Introduction ....................................................4
   2. Terminology .....................................................6
   3. Protocol Overview ...............................................6
   4. WiCoP Format ....................................................7
      4.1. WiCoP Header ...............................................8
      4.2. WiCoP Control Packet ......................................11
           4.2.1. WiCoP Control Messages .............................12
           4.2.2. WiCoP Control Message Elements .....................12
           4.2.3. WiCoP Control Message Description ..................27
      4.3. WiCoP Data Packet .........................................36
      4.4. WiCoP Timers ..............................................37
           4.4.1. Active Presence Timer ..............................37
           4.4.2. Feedback Interval ..................................37
           4.4.3. Response Timer .....................................37
           4.4.4. Wireless Connectivity Timer ........................38
   5. WiCoP Processes ................................................38
      5.1. Initialization ............................................38
      5.2. Capabilities Exchange .....................................38
      5.3. Connection ................................................39
      5.4. Configuration .............................................40
           5.4.1. Logical Groups .....................................41
           5.4.2. Resource Control ...................................41
      5.5. Operation .................................................41
           5.5.1. Updates ............................................42
           5.5.2. Feedback and Statistics ............................42
           5.5.3. Non-Periodic Events ................................43
           5.5.4. Firmware Trigger ...................................43
           5.5.5. Wireless Terminal Management .......................43
           5.5.6. Key Configuration ..................................46
   6. WiCoP Performance ..............................................51
      6.1. Operational Efficiency ....................................51
      6.2. Semantic Efficiency .......................................51
   7. Summary and Conclusion .........................................51
   8. Security Considerations ........................................52
   9. Informative References .........................................53

1.  Introduction

   The popularity of wireless local area networks (WLANs) has led to
   numerous but incompatible designs and solutions.  The CAPWAP
   Architecture Taxonomy [RFC4118] describes major variations of these
   designs.  Among them, the Local MAC (Media Access Control) and Split
   MAC architecture designs are notable categories.

   Wireless LAN Control Protocol (WiCoP) recognizes the major
   architecture designs and presents a common platform on which WLAN
   entities of different designs can be accommodated.  This enables
   interoperability among wireless termination points (WTPs) and WLAN
   access controllers (ACs) of distinct architecture designs.  WiCoP
   therefore allows for cost-effective WLAN expansions.  It can also
   accommodate future developments in WLAN technologies.  Figure 1
   illustrates the WiCoP operational structure in which distinct control
   elements are utilized for Local MAC and Split MAC WTPs.

   WiCoP also addresses the increasing trend of shared infrastructure
   WLANs.  Here, WLAN management needs to distinguish and isolate
   control for the different logical groups sharing a single physical
   WLAN.  WiCoP manages WLANs through a series of tunnels that separate
   traffic based on logical groups.

   The WiCoP operational structure in Figure 1 shows that each WTP uses
   a number of tunnels to distinguish and separate traffic for control
   and for each logical group.  The protocol allows for managing WLANs
   in a manner consistent with the logical groups that share the
   physical infrastructure.

                                 Local MAC WTP

   +-------+                       +-------+
   |       |                       |       |    Logical Groups
   |      (=====Control Tunnel======)      |
   |       |                       |       |       ~~~~~~~
   |       |                       |       |      /       /
   |      <=====Logical Group A=====>      |      /   A   /~~~~
   |       |                       |       |      /       /    /
   |      <=====Logical Group B=====>      |       ~~~~~~~     /~~~~
   |       |                       |       |           /    B  /    /
   |      <=====Logical Group C=====>      |            ~~~~~~~     /
   |       |                       |       |                /    C  /
   |       |                       +-------+                 ~~~~~~~
   |       |
   |       |
   |  AC   |
   |       |
   |       |                     Split MAC WTP
   |       |
   |       |                       +-------+    Logical Groups
   |       |                       |       |
   |      [=====Control Tunnel======]      |      ~~~~~~~
   |       |                       |       |     /       /
   |       |                       |       |     /   1   /~~~~
   |      <=====Logical Group 1=====>      |     /       /    /
   |       |                       |       |      ~~~~~~~     /
   |      <=====Logical Group 2=====>      |          /    2  /
   |       |                       |       |           ~~~~~~~
   +-------+                       +-------+

                                 Figure 1

   In Figure 1, WiCoP establishes and operates control tunnels and
   logical group tunnels between the AC and two types of WTPs.  The
   control tunnels are used to transport WiCoP messages dealing with the
   configuration, monitoring, and management of WTPs as a physical
   whole.  The logical group tunnels serve to separate traffic among
   each of the logical groups constituting a physical WTP.

2.  Terminology

   This document follows the terminologies of [RFC4118] and [RFC4564].

3.  Protocol Overview

   The Wireless LAN Control Protocol (WiCoP) focuses on enabling
   interoperability in shared infrastructure WLANs.  It is designed for
   use with different wireless technologies.  This document provides
   both the general operations of WiCoP and also specific use-cases with
   respect to IEEE 802.11-based systems.

   The state machine for WiCoP is illustrated in Figure 2.

                                    +--------------------------------+
                                    |                                |
                                    |   +------------------+         |
                                    V   V                  |         |
    +-------------+         +-------------+         +-------------+  |
    |             |         |             |         |             |  |
    | Initial-    |-------->| Capabilities|-------->|  Connection |  |
    |    ization  |         |   Exchange  |         |             |  |
    |             |         |             |         |             |  |
    +-------------+         +-------------+         +-------------+  |
           A                       A                       |         |
           |                       |                       |         |
           |                       |                       |         |
           |                       |                       |         |
           |                       |                       V         |
           |                       |                +-------------+  |
           |                       |                |             |  |
           |                       +----------------| Configur-   |  |
           |                                        |     ation   |  |
           |                                        |             |  |
           |                                        +-------------+  |
           |                                               |         |
           |                                               |         |
           |                                               |         |
           |                                               |         |
           |                                               V         |
           |                                        +--------------+ |
           |                                        |              | |
           +----------------------------------------|              |-+
                                                    |  Operation   |
                                                    |              |
                                                    +--------------+
                                  Figure 2

   The Initialization state represents the initial states of WTPs and
   AC.  A WTP or AC in this state powers on, clears internal registers,
   runs hardware self-tests, and resets network interfaces.

   The Capabilities Exchange state represents initial protocol exchange
   between a WTP and AC.  A WTP in this state determines possible ACs
   from which it can receive management services.  An AC in this state
   determines the capabilities of the WTP and the WTP's compatibility
   with the management services it offers.

   The Connection state represents the creation of a security
   infrastructure between a WTP and AC.  This involves mutual
   authentication and the establishment of a secure connection between
   the WiCoP entities.

   The Configuration state represents the exchange of long-term
   operational parameters and settings between a WTP and AC.  A WTP in
   this state receives configuration information to allow it to operate
   consistently within the WLAN managed by the AC.  An AC in this state
   provides configuration information to the WTP based on the WTP's
   capabilities and network policies.

   The Operation state represents the active exchange of WiCoP
   monitoring and management messages.  WTPs send regular status updates
   to and receive corresponding management instructions from the AC.
   This state also involves firmware and configuration updates arising
   from changes in network conditions and administrative policies.

4.  WiCoP Format

   WiCoP uses separate packets for control and data message transfer
   between the AC and WTPs.  A common header is used for both types of
   packets in which a single-bit flag distinguishes between them.  This
   section presents the packet formats for WiCoP packets.

4.1.  WiCoP Header

   Figure 3 illustrates the WiCoP common header for control and data
   packets.

   0                                                              31
   |                7               15              23             |
   |-------|-------|-------|-------|-------|-------|-------|-------|
   |                                                               |

   +---------------+-+-+-+-+-+-+-+-+-------------------------------+
   |    Version    |M|D|C|R|E|F|L| |           Reserve             |
   +---------------+-+-+-+-+-+-+-+-+-------------------------------+
   |  Fragment ID  | Fragment No.  |           Length              |
   +---------------+---------------+-------------------------------+

                                 Figure 3

   Version Field

   This field indicates the protocol version.

   'M' Field

   The MAC-type field, 'M', distinguishes between Local MAC WTPs and
   Split MAC WTPs.  It is used to efficiently realize interoperability
   between WTPs of the two different designs.  A '0' value indicates
   WiCoP exchanges with a Split MAC WTP while a '1' value indicates
   WiCoP exchanges with a Local MAC WTP.

   The presence of this classification bit in the WiCoP common header
   serves to expedite processing of WiCoP and WLAN traffic at the AC.
   With a single parsing of the WiCoP common header once, the AC will be
   able to determine the appropriate processing required for the
   particular WiCoP packet.

   'D' Field

   The differentiator field, 'D', is used to distinguish between WTP
   variants within a type of WTP design.  The CAPWAP Architecture
   Taxonomy [RFC4118] illustrates that the Split MAC design allows
   encryption/decryption to be performed at either the WTP or the AC.
   The Architecture Taxonomy also indicates that the Local MAC design
   allows authentication to take place at either the WTP or the AC.

   WiCoP acknowledges these major variants and accommodates them using
   the 'D' field in conjunction with the 'M' field.  For a Split MAC
   WTP, the 'D' field is used to indicate location of
   encryption/decryption while for a Local MAC WTP, the 'D' field is
   used to indicate location of authentication.  The following table
   highlights their usage.

   'M'             'D'             Description

    0               0              Split MAC WTP - Encryption/decryption
                                   is performed at WTP
    0               1              Split MAC WTP - Encryption/decryption
                                   is performed at AC
    1               0              Local MAC WTP - Authentication is
                                   performed by WTP
    1               1              Local MAC WTP - Authentication is
                                   performed by AC

   Similar to the 'M' field, the presence of this classification in the
   WiCoP common header helps expedite processing at the AC with a single
   parsing.  By incorporating the classification bits in the WiCoP
   common header, where it is available for all packets of a session,
   the AC processing can be expedited.  Alternatively, the AC would have
   to check each arriving packet against an internal register and
   consequently delay processing.

   'C' Field

   This field distinguishes between a WiCoP control and WiCoP data
   packet.  Each type of information is tunneled separately across the
   WiCoP tunnel interfaces between WTPs and the AC.  A '0' value for the
   'C' field indicates a data packet, while a '1' value indicates a
   control packet.

   The 'C' field is also used to assign WiCoP packets to distinct data
   and control tunnels between the AC and WTP.  WiCoP also maintains
   logical groups in WLANs with the 'C' field.

   'R' Field

   The retransmission field, 'R', is used to differentiate between the
   first and subsequent transmissions of WiCoP packets.  The 'R' field
   is used for critical WiCoP packets such as those relating to security
   key exchanges.  A '0' value for the 'R' field indicates the first
   transmission of a WiCoP packet, while a '1' value indicates a
   retransmission.

   'E' Field

   The encryption field, 'E', is used to indicate if the WiCoP packet is
   encrypted between the AC and WTPs.  The 'E' field is used for those
   WiCoP packets that are exchanged during initialization.  A '0' value
   indicates the WiCoP packet is unencrypted, while a '1' value
   indicates the packet is encrypted.

   'F' Field

   The fragmentation field indicates if the packet is a fragment of a
   larger packet.  A '0' value indicates a non-fragmented packet while a
   '1' value indicates a fragmented packet.  The 'F', 'L', 'Fragment
   ID', and 'Fragment No.' fields are used together.

   'L' Field

   This field is used to indicate the last fragment of a larger packet.
   It is only valid when the 'F' field has a '1' value.  A '0' value for
   the 'L' field indicates the last fragment of a larger packet while a
   '1' value indicates an intermediate fragment of a larger packet.  The
   'F', 'L', 'Fragment ID', and 'Fragment No.' fields are used together.

   Fragment ID Field

   The Fragment ID identifies the larger packet that has been
   fragmented.  It is used to distinguish between fragments of different
   large packets.  This field is valid only when the 'F' field has a '1'
   value.  The 'F', 'L', 'Fragment ID', and 'Fragment No.' fields are
   used together.

   Fragment No.  Field

   The fragment number field identifies the sequence of fragments of a
   larger packet.  The value of the Fragment No. field is incremented
   for each fragment of a larger packet so as to show the order of
   fragments.  This field is valid only when the 'F' field has a '1'
   value.  The 'F', 'L', 'Fragment ID', and 'Fragment No.' fields are
   used together.

   Length Field

   This field specifies the length of the WiCoP payload following the
   header.

4.2.  WiCoP Control Packet

   The WiCoP control header follows the WiCoP common header.  It is
   highlighted in Figure 5.

   0                                                              31
   |                7               15              23             |
   |-------|-------|-------|-------|-------|-------|-------|-------|
   |                                                               |

   +---------------+---------------+-------------------------------+
   |   Msg Type    |   Reserve     |           Seq Num             |
   +---------------+---------------+-------------------------------+
   |       Msg Element Length      |
   +-------------------------------+

                                 Figure 5

   The control packet adds four additional fields to the common header.
   These are described below:

   Msg Type Field

   The message type field specifies the type of control message
   transported in the packet.  The list of control messages is presented
   in Section 5.2.1.

   Seq Num Field

   The sequence number field is used to map WiCoP request and response
   sequences.  The initiator of a WiCoP request message increments the
   Seq Num field for each new request message.  The responder then uses
   these values of the Seq Num fields in its corresponding response
   messages.

   Msg Element Length Field

   This field specifies the length in bytes of the subsequent WiCoP
   control message element.

4.2.1.  WiCoP Control Messages

   The list of WiCoP control messages is shown below:

   Message                                 Msg Type
   ------------------------------------------------------------

   Capabilities                            1
   Capabilities Response                   2
   Connection                              3
   Connection Response                     4
   Configuration Request                   5
   Configuration Response                  6
   Configuration Data                      7
   Configuration Data Response             8
   Configuration Trigger                   9
   Configuration Trigger Response          10
   Feedback                                11
   Feedback Response                       12
   Reset                                   13
   Reset Response                          14
   Firmware Download                       15
   Firmware Download Response              16
   Terminal Addition                       17
   Terminal Addition Response              18
   Terminal Deletion                       19
   Terminal Deletion Response              20
   Key Configuration                       21
   Key Configuration Response              22
   Notification                            23
   Notification Response                   24

4.2.2.  WiCoP Control Message Elements

   WiCoP control messages each include a control message header followed
   by one or more message elements.  The message elements are shown in
   the following table:

   +-----------------+-----------+-------------------------------------+
   | Message Element | Type      | Description                         |
   +-----------------+-----------+-------------------------------------+
   | WTP-Info        | 1         | Information regarding WTPs, such as |
   |                 |           | manufacturer ID, MAC address, etc.  |
   |                 |           |                                     |
   | Cap-from-WTP    | 2         | Quality-of-Service (QoS) abilities  |
   |                 |           | (WME-Wireless Multimedia Extension) |
   |                 |           |  and security abilities             |
   |                 |           | (IEEE 802.11i) are included         |
   |                 |           |                                     |
   | Conf-If-Data    | 3         | Physical Layer (PHY) information for|
   |                 |           | each wireless interface             |
   |                 |           |                                     |
   | Conf-WTP-Data   | 4         | Information regarding logical       |
   |                 |           | groups on a per-logical group basis |
   |                 |           | (e.g., per-virtual AP)              |
   |                 |           |                                     |
   | Cap-to-WTP      | 5         | Setup data sent to WTPs by an AC on |
   |                 |           | a per-logical group basis           |
   |                 |           |                                     |
   | QoS-Value       | 6         | QoS setup (access categories)       |
   |                 |           |                                     |
   |Timer-Init-Value | 7         | Initial values of timers such as    |
   |                 |           | aging, echo interval, etc.          |
   |                 |           |                                     |
   | Terminal-Data   | 8         | Information relevant to wireless    |
   |                 |           | terminals - Basic Service Set       |
   |                 |           | Identifier (BSSID), association ID, |
   |                 |           | etc.                                |
   |                 |           |                                     |
   | BSSID           | 9         | BSSID, and terminal MAC address     |
   |                 |           |                                     |
   | Encryption-Data | 10        | Details of the security framework - |
   |                 |           | cipher suit, operation mode, etc.   |
   |                 |           |                                     |
   | EAP-Frame       | 11        | Extensible Authentication Protocol  |
   |                 |           | (EAP) frame                         |
   |                 |           |                                     |
   | Statistics      | 12        | Various statistics information -    |
   |                 |           | transmission attempts, Frame Check  |
   |                 |           | Sequence (FCS) errors, etc.         |
   |                 |           |                                     |
   | Interface-Error | 13        | Type of wireless interface failure  |
   |                 |           |                                     |
   | FROM-Error      | 14        | Flash ROM Error information         |
   |                 |           |                                     |
   | QoS-Capability  | 15        | Network congestion information      |

   |                 |           |                                     |
   | TFTP-Data       | 16        | Firmware-related details            |
   |                 |           |                                     |
   | Result          | 17        | Result of protocol operations -     |
   |                 |           | success or failure                  |
   |                 |           |                                     |
   | OID             | 18        | Simple Network Management Protocol  |
   |                 |           | (SNMP) Object Identifiers (OIDs)    |
   |                 |           |                                     |
   | GTK-Flag        | 19        | Determines type of Group Temporal   |
   |                 |           | Key (GTK) - new or existing         |
   +-----------------+-----------+-------------------------------------+

   Each message element comprises a number of information items that are
   detailed below.  The length of each information item is specified in
   bytes.

   WTP-Info:

   Information included in the WTP-Info message element is provided on a
   per-WTP basis, i.e., each WTP exchanges one WTP-Info message element.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | Manufacturer | 8        | DisplayString  | Manufacturer ID        |
   | ID           |          |                |                        |
   |              |          |                |                        |
   | MAC Address  | 6        | PhyAddress     | WTP MAC Address        |
   |              |          |                |                        |
   | Firmware     | 8        | DisplayString  | Firmware version of    |
   | Version      |          |                | WTP                    |
   |              |          |                |                        |
   | Start Time   | 4        | TimeTicks      | Starting time of WTP   |
   |              |          |                | (UNIX Time)            |
   +--------------+----------+----------------+------------------------+

   Cap-from-WTP:

   Information included in the Cap-from-WTP message element is provided
   on a per-WTP basis, i.e., each WTP exchanges one Cap-from-WTP message
   element.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | 802.11e Cap  | 2        | Integer        | Length of 802.11e      |
   | Length       |          |                | capabilities           |
   |              |          |                |                        |
   | 802.11e      | Variable | OCTETString    | 802.11e capabilities   |
   | Capabilities |          |                | of WTP. If WTP does    |
   |              |          |                | not have such          |
   |              |          |                | capabilities, this     |
   |              |          |                | field is filled with   |
   |              |          |                | '0'                    |
   |              |          |                |                        |
   | 802.11i Cap  | 2        | Integer        | Length of 802.11i      |
   | Length       |          |                | capabilities           |
   |              |          |                |                        |
   | 802.11i      | Variable | OCTETString    | 802.11i capabilities   |
   | Capabilities |          |                | of WTP. If WTP does    |
   |              |          |                | not have such          |
   |              |          |                | capabilities,this      |
   |              |          |                | field is filled with   |
   |              |          |                | '0'                    |
   |              |          |                |                        |
   | AuthType     | 2        | OCTETString    | Type of authentication |
   |              |          |                | mechanism used between |
   |              |          |                | WTPs and the AC        |
   +--------------+----------+----------------+------------------------+

   Conf-If-Data

   The Conf-If-Data message element relates to the wireless interface.
   A WTP with many interfaces will include corresponding numbers of
   Conf-If-Data message elements within its control messages to the AC.
   Conf-If-Data message elements are indexed by the If ID information
   item.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | If ID        | 1        | Integer        | Denotes identification |
   |              |          |                | of a wireless          |
   |              |          |                | interface              |
   |              |          |                |                        |
   | Current      | 1        | Integer        | Current Power Level    |
   | Power        |          |                | ('1' = Max; '2' = 1/2; |
   |              |          |                | '3' = 1/4; '4' = 1/8   |
   |              |          |                |                        |
   | Radio        | 1        | Integer        | Radio channel of       |
   | Channel      |          |                | operation              |
   |              |          |                |                        |
   | 2Dot4Mode    | 1        | Integer        | Interface mode in      |
   |              |          |                | 2.4GHz. ('1' = IEEE    |
   |              |          |                | 802.11b; '2' = IEEE    |
   |              |          |                | 802.11g; '3' = Both)   |
   +--------------+----------+----------------+------------------------+

   Conf-WTP-Data

   Configuration information is provided on the basis of logical groups
   such as virtual APs.  There are multiple Conf-WTP-Data message
   elements to address the many logical groups within a WLAN managed by
   WiCoP.  Conf-WTP-Data message elements are indexed by the BSSID
   information item.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | OCTETString    | BSSID                  |
   |              |          |                |                        |
   | ESSID        | 32       | OCTETString    | Extended Service Set   |
   |              |          |                | Identifier (ESSID)     |
   |              |          |                |                        |
   | BSSID -      | 32       | OCTETString    | Mapping for logical    |
   | TunnelID     |          |                | groups across BSSID    |
   |              |          |                | and WiCoP tunnels      |
   |              |          |                |                        |
   | Beacon       | 1        | Integer        | Time interval between  |
   | Period       |          |                | Beacon transmissions   |
   |              |          |                |                        |
   | DTIM Period  | 1        | Integer        | Delivery Traffic       |
   |              |          |                | Indication Message     |
   |              |          |                | (DTIM) period of       |
   |              |          |                | Beacon transmissions   |
   |              |          |                |                        |

   | AnyRejectFla | 1        | Integer        | Flag indicating WTP    |
   | g            |          |                | rejection of any Probe |
   |              |          |                | Request within any     |
   |              |          |                | SSID - ('1' =          |
   |              |          |                | Rejected; '2' = Not    |
   |              |          |                | Rejected)              |
   |              |          |                |                        |
   | SSID Stealth | 1        | Integer        | Flag indicating        |
   | Flag         |          |                | inclusion of ESSID     |
   |              |          |                | within Beacon Frames   |
   |              |          |                | ('1' = ESSID included; |
   |              |          |                | '2' = ESSID not        |
   |              |          |                | included)              |
   |              |          |                |                        |
   | Operation    | 2        | Integer        | Data rates supported   |
   | Rate Set     |          |                | by WTP for terminal    |
   |              |          |                | being added using a    |
   |              |          |                | 12-bit format for 1.1, |
   |              |          |                | 2.2, 3.55, 4.6, 5.9,   |
   |              |          |                | 6.11, 7.12, 8.18,      |
   |              |          |                | 9.24, 10.36, 11.48,    |
   |              |          |                | and 12.54 Mbps         |
   |              |          |                |                        |
   | Encryption   | 1        | Integer        | Encryption Type -      |
   | Type         |          |                | &#65288;'1' = OFF; '2' |
   |              |          |                | = WEP40; '3' = WEP104; |
   |              |          |                | '4' = WEP128)          |
   |              |          |                |                        |
   | Encryption   | 16       | OCTETString    | Static Encryption Key  |
   | Key          |          |                |                        |
   +--------------+----------+----------------+------------------------+

   Cap-to-WTP:

   Capabilities information is provided on the basis of logical groups
   such as virtual APs.  So, there are multiple Cap-to-WTP message
   elements to address the many logical groups within a WLAN managed by
   WiCoP.  Conf-to-WTP message elements are indexed by the BSSID
   information item.  If logical groups are created by other means,
   their corresponding identifier is used as the index.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | OCTETString    | BSSID                  |
   |              |          |                |                        |
   | 802.11e Cap  | 2        | Integer        | Length of 802.11e      |
   | Length       |          |                | capabilities           |
   |              |          |                |                        |
   | 802.11e      | Variable | OCTETString    | 802.11e capabilities   |
   | Capabilities |          |                | of WTP. If WTP does    |
   |              |          |                | not have such          |
   |              |          |                | capabilities, this     |
   |              |          |                | field is filled with   |
   |              |          |                | '0'                    |
   |              |          |                |                        |
   | 802.11i Cap  | 2        | Integer        | Length of 802.11i      |
   | Length       |          |                | capabilities           |
   |              |          |                |                        |
   | 802.11i      | Variable | OCTETString    | 802.11i capabilities   |
   | Capabilities |          |                | of WTP.  If WTP does   |
   |              |          |                | not have such          |
   |              |          |                | capabilities, this     |
   |              |          |                | field is filled with   |
   |              |          |                | '0'                    |
   +--------------+----------+----------------+------------------------+

   QoS-Value:

   QoS parameters are assigned for each logical group to address their
   respective individual conditions and requirements.  QoS-Value message
   elements are provided on a per-logical group basis.  They are indexed
   by the BSSID information item.  If logical groups are created by
   other means, their corresponding identifier is used as the index.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | OCTETString    | BSSID                  |
   |              |          |                |                        |
   | WTP AC_BE    | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_BE in WTP           |
   |              |          |                |                        |
   | WTP AC_BK    | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_BK in WTP           |
   |              |          |                |                        |
   | WTP AC_VI    | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_VI in WTP           |
   |              |          |                |                        |
   | WTP AC_VO    | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_VO in WTP           |
   |              |          |                |                        |
   | TE AC_BE     | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_BE in terminals     |
   |              |          |                |                        |
   | TE AC_BK     | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_BK in terminals     |
   |              |          |                |                        |
   | TE AC_VI     | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_VI in terminals     |
   |              |          |                |                        |
   | TE AC_VO     | 2        | Integer        | AC Parameters Record   |
   |              |          |                | AC_VO in terminals     |
   +--------------+----------+----------------+------------------------+

   Timer-Init-Value:

   WiCoP timers are used for the WTP as a whole.  So, the Timer-Init-
   Value message element is provided on a per-WTP basis.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | OCTETString    | BSSID                  |
   |              |          |                |                        |
   | Response     | 4        | Integer        | Initial value of       |
   | Timer        |          |                | Response Timer         |
   |              |          |                |                        |
   | Active       | 4        | Integer        | Initial value of       |
   | Presence     |          |                | Active Presence Timer  |
   | Timer        |          |                |                        |
   |              |          |                |                        |
   | Feedback     | 4        | Integer        | Initial value of       |
   | Interval     |          |                | Feedback Interval      |
   | Timer        |          |                | Timer                  |
   +--------------+----------+----------------+------------------------+

   Terminal-Data:

   The Terminal-Data message element is applicable for both Local MAC
   and Split MAC WTP designs.  In the case of Local MAC, Terminal-Data
   is sent from WTPs to the AC.  In the case of Split MAC, Terminal-Data
   is sent from the AC to WTPs.  So, the direction of usage depends on
   the type of WTP at which wireless terminal operations are performed.
   Some information items may be optional for use with specific WTP
   designs.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | PhyAddress     | BSSID in which         |
   |              |          |                | terminal is being      |
   |              |          |                | added                  |
   |              |          |                |                        |
   | MAC Address  | 6        | PhyAddress     | MAC address of         |
   |              |          |                | terminal being added   |
   |              |          |                |                        |
   | Association  | 2        | Integer        | Association ID of      |
   | ID           |          |                | terminal being added   |
   |              |          |                |                        |
   | Operation    | 2        | Integer        | Data rates supported   |
   | Rate Set     |          |                | by WTP for terminal    |
   |              |          |                | being added using a    |
   |              |          |                | 12-bit format for 1.1, |
   |              |          |                | 2.2, 3.55, 4.6, 5.9,   |
   |              |          |                | 6.11, 7.12, 8.18,      |
   |              |          |                | 9.24, 10.36, 11.48,    |
   |              |          |                | and 12.54 Mbps         |
   |              |          |                |                        |
   | Listen       | 2        | Integer        | Listen period          |
   | Period       |          |                |                        |
   +--------------+----------+----------------+------------------------+

   BSSID:

   The BSSID message element is used to identify logical groups within a
   WLAN.  WiCoP may be extended for other types of logical groups by
   simply including additional message elements.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | BSSID        | 6        | PhyAddress     | BSSID in which         |
   |              |          |                | terminal is being      |
   |              |          |                | added                  |
   |              |          |                |                        |
   | MAC Address  | 6        | PhyAddress     | MAC address of         |
   |              |          |                | terminal being added   |
   +--------------+----------+----------------+------------------------+

   Encryption-Data:

   The Encryption-Data message element contains information relevant for
   configuring security keys at WTPs.  It is used in architectures in
   which the authentication and encryption points are located in
   distinct WLAN entities.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | MAC Address  | 6        | PhyAddress     | MAC address of         |
   |              |          |                | terminal               |
   |              |          |                |                        |
   | Operation    | 1        | Integer        | Operational Mode ('1'  |
   |              |          |                | = Set Key; '2' =       |
   |              |          |                | Delete Key)            |
   |              |          |                |                        |
   | Key Index    | 1        | Integer        | Key Index - valid when |
   |              |          |                | Operational Mode = Set |
   |              |          |                | Key                    |
   |              |          |                |                        |
   | Key Flag     | 1        | Integer        | Key Flag ('1' =        |
   |              |          |                | Unicast Key or PTK;    |
   |              |          |                | '2' = Broadcast Key or |
   |              |          |                | GTK) - valid only when |
   |              |          |                | Operational Mode = Set |
   |              |          |                | Key                    |
   |              |          |                |                        |
   | Cipher Suit  | 1        | Integer        | Encryption Type ('1' = |
   |              |          |                | WEP40; '2' = WEP104;   |
   |              |          |                | '3' = WEP128; '4' =    |
   |              |          |                | TKIP; '5' = AES) -     |
   |              |          |                | valid only when        |
   |              |          |                | Operational Mode = Set |
   |              |          |                | Key                    |
   |              |          |                |                        |
   | Key          | 32       | OCTETString    | Key body - valid only  |
   |              |          |                | when Operational Mode  |
   |              |          |                | = Set Key              |
   +--------------+----------+----------------+------------------------+

   EAP-Frame:

   The EAP-Frame message element is used to carry EAP frames used in the
   configuration and management of the WLAN.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | MAC Address  | 6        | PhyAddress     | MAC address of         |
   |              |          |                | terminal               |
   |              |          |                |                        |
   | EAP          | Variable | OCTETString    | EAP Frames             |
   +--------------+----------+----------------+------------------------+

   Statistics:

   Statistics information covers all aspects of WTPs.  As such, this
   message element is provided on a per-WTP basis.  WiCoP messages
   containing the Statistics message element simultaneously serve as
   keepalive signals between WTPs and the AC.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | OutOctet     | 4        | Counter 32     | Octet number of frame  |
   |              |          |                | WTP transmits          |
   |              |          |                |                        |
   | Transmit     | 4        | Counter 32     | Total number of frames |
   | Count        |          |                | transmitted by WTP     |
   |              |          |                |                        |
   | Successful   | 4        | Counter 32     | Total number of ACKs   |
   | Transmit     |          |                | received               |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | ACK Failure  | 4        | Counter 32     | Total number of failed |
   | Count        |          |                | ACKs                   |
   |              |          |                |                        |
   | InOctets     | 4        | Counter 32     | Octet number of frame  |
   |              |          |                | WTP receives           |
   |              |          |                |                        |
   | Receive      | 4        | Counter 32     | Total number of frames |
   | Count        |          |                | received by WTP        |
   |              |          |                |                        |
   | Receive      | 4        | Counter 32     | Total number of        |
   | Discard      |          |                | received frames that   |
   |              |          |                | are discarded          |
   |              |          |                |                        |
   | Retransmissi | 4        | Counter 32     | Number of WTP          |
   | on Count     |          |                | retransmission         |
   |              |          |                | attempts"              |
   |              |          |                |                        |

   | Duplicate    | 4        | Counter 32     | Number of duplicate    |
   | Receive      |          |                | frames received by WTP |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | FCS Error    | 4        | Counter32      | Number of frames       |
   | Receive      |          |                | received with FCS      |
   | Count        |          |                | errors                 |
   |              |          |                |                        |
   | Unknown      | 4        | Counter 32     | Number of unknown      |
   | Frame        |          |                | protocol frames        |
   | Receive      |          |                | received               |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | Beacon       | 4        | Counter 32     | Number of transmitted  |
   | Transmit     |          |                | Beacon frames          |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | Probe        | 4        | Counter 32     | Number of transmitted  |
   | Transmit     |          |                | Probe Response frames  |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | Probe        | 4        | Counter 32     | Number of received     |
   | Receive      |          |                | Probe Response frames  |
   | Count        |          |                |                        |
   |              |          |                |                        |
   | Decrypt CRC  | 4        | Counter 32     | Number of received     |
   | Error Count  |          |                | frames that cannot     |
   |              |          |                | decrypt                |
   +--------------+----------+----------------+------------------------+

   Interface-Error:

   This message element is used to exchange information on error
   conditions related to the wireless interface.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | Interface    | 1        | Integer        | Interface ID           |
   | Index        |          |                |                        |
   |              |          |                |                        |
   | Error Type   | 1        | Integer        | Type of error ('1' =   |
   |              |          |                | Unrecoverable; '2' =   |
   |              |          |                | Recoverable)           |
   +--------------+----------+----------------+------------------------+

   FROM-Error:

   The FROM-Error message element is used to exchange information on
   error conditions related to flash ROMs in WTPs or the AC.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | FROM Index   | 1        | Integer        | FROM ID                |
   |              |          |                |                        |
   | Error Type   | 1        | Integer        | Type of error ('1' =   |
   |              |          |                | Unrecoverable; '2' =   |
   |              |          |                | Recoverable)           |
   +--------------+----------+----------------+------------------------+

   QoS Capability:

   The QoS-Capability message element is used to exchange information
   concerning the Enhanced Distributed Channel Access (EDCA) and HCF
   Controlled Channel Access (HCCA) capabilities of WTPs.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | EDCA         | 1        | Integer        | EDCA Capability ('1' = |
   |              |          |                | Capable; '2' = Not     |
   |              |          |                | capable)               |
   |              |          |                |                        |
   | HCCA         | 1        | Integer        | HCCA Capability ('1' = |
   |              |          |                | Capable; '2' = Not     |
   |              |          |                | capable)               |
   +--------------+----------+----------------+------------------------+

   TFTP-Data:

   This message element is for firmware data from an AC to WTPs.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | TFTP Data    | Variable | OCTETString    | Details of Trivial File|
   |              |          |                | Transfer Protocol      |
   |              |          |                | (TFTP)                 |
   +--------------+----------+----------------+------------------------+

   Result:

   The Result message element is used in all WiCoP response messages to
   indicate the status of WiCoP request messages.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | Result Code  | 1        | Integer        | '1' = OK; '2' = NG     |
   +--------------+----------+----------------+------------------------+

   OID:

   The OID message element is used for general configuration information
   specified by OIDs.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | Length       | 1        | Integer        | Length of OID String   |
   |              |          |                | and OID Value          |
   |              |          |                |                        |
   | OID String   | Variable | OCTETString    | Object Identifier that |
   |              |          |                | is assigned according  |
   |              |          |                | to Basic Encoding      |
   |              |          |                | Rules (BER)            |
   |              |          |                |                        |
   | Value        | Variable | OCTETString    | Value                  |
   +--------------+----------+----------------+------------------------+

   GTK-Flag:

   The GTK-Flag message element is used to inform the WTP on the type of
   GTK used and correspondingly how the KeyMIC is to be computed.

   +--------------+----------+----------------+------------------------+
   | Item         | Length   | Syntax         | Description            |
   +--------------+----------+----------------+------------------------+
   | GTK Flag     | 1        | Integer        | Determines the type of |
   |              |          |                | GTK ('1' = New; '2' =  |
   |              |          |                | Existing)              |
   +--------------+----------+----------------+------------------------+

4.2.3.  WiCoP Control Message Description

   Message: Capabilities
   Direction: WTP -> AC
   Type: Request

   Description: WTPs send a Capabilities message upon transitioning from
   the Initialization state to the Capabilities Exchange state.  The
   message serves to discover and identify the controlling AC of the
   WLAN and to provide it with identification and capabilities
   information.  In the IEEE 802.11 use-case, the Capabilities message
   also specifies the WTP's IEEE 802.11e and IEEE 802.11i features.

   TLV: The Capabilities message includes message elements of types 1
   and 2.

                           +----------------+
                           |  Capabilities  |
                           +----------------+
                           |    WTP-Info    |
                           |                |
                           |  Cap-from-WTP  |
                           +----------------+

   Message: Capabilities Response
   Direction: AC -> WTP
   Type: Response

   Description: This message is sent by an AC after examining the
   compatibility of the WTP and its capabilities.  The compatibility is
   with respect to the MAC architecture that can be supported by the AC.
   If the WTP is determined to be compatible, the Capabilities Response
   message also contains information on the capabilities of the AC.

   TLV: The Capabilities Response message includes message elements of
   types 5 and 17.  The Cap-to-WTP message elements are distinguished
   based on BSSIDs to represent different logical groups.

                       +-----------------------+
                       | Capabilities Response |
                       +-----------------------+
                       |      Cap-to-WTP 1     |
                       |                       |
                       |     Cap-to-WTP ...    |
                       |                       |
                       |      Cap-to-WTP n     |
                       |                       |
                       |        Result         |
                       +-----------------------+

   Message: Connection
   Direction: WTP -> AC
   Type: Request

   Description: The Connection message initiates the mutual security
   association between an AC and WTPs.  This message carries the first
   message of the chosen security protocol.  The specific security
   mechanism for the authentication is out of scope of the WiCoP
   specifications.

   TLV: The Connection message includes message elements of type 2.

                           +---------------+
                           |   Connection  |
                           +---------------+
                           | Cap-from-WTP  |
                           +---------------+

   Message: Connection Response
   Direction: AC -> WTP
   Type: Response

   Description: After completion of the security protocol exchange, this
   message indicates the result of the WTP-AC security association.  If
   successful, it also represents the admission of the WTP into the
   WLAN.

   TLV: Type 17 message element is included.

                        +---------------------+
                        | Connection Response |
                        +---------------------+
                        |       Result        |
                        +---------------------+

   Message: Configuration Request
   Direction: WTP -> AC
   Type: Request

   Description: This message starts the Configuration state for the WTP.
   It is a request for configuration information from the WTPs to the
   AC.

   Message: Configuration Response
   Direction: AC -> WTP
   Type: Response

   Description: This is an acknowledgement for the Configuration Request
   message.

   TLV: Type 17 message element is included.

                       +------------------------+
                       | Configuration Response |
                       +------------------------+
                       |         Result         |
                       +------------------------+

   Message: Configuration Data
   Direction: AC -> WTP
   Type: Request

   Description: Configuration information including operational
   parameters, QoS settings, and timer values is sent using the
   Configuration Data message.  This message is also used for
   configuration updates in the Operation state of WiCoP.

   TLV: This message includes message elements of types 3, 4, 5, 6, and
   7.  The Conf-WTP-Data and QoS-Value message elements are identified
   by BSSIDs to denote logical groups, while the Conf-If-Data message
   elements are identified by If-IDs to denote multiple wireless radios.

                        +---------------------+
                        |  Configuration Data |
                        +---------------------+
                        |   Conf-If-Data 1    |
                        |                     |
                        |  Conf-If-Data ...   |
                        |                     |
                        |   Conf-If-Data n    |
                        |                     |
                        |   Conf-WTP-Data 1   |
                        |                     |
                        |  Conf-WTP-Data ...  |
                        |                     |
                        |   Conf-WTP-Data n   |
                        |                     |
                        |     Cap-to-WTP 1    |
                        |                     |
                        |    Cap-to-WTP ...   |
                        |                     |
                        |     Cap-to-WTP n    |
                        |                     |
                        |     QoS-Value 1     |
                        |                     |
                        |    QoS-Value ...    |
                        |                     |
                        |     QoS-Value n     |
                        |                     |
                        |  Timer-Init-Value   |
                        +---------------------+

   Message: Configuration Data Response
   Direction: WTP -> AC
   Type: Response

   Description: This is an acknowledgement for the Configuration Data
   message.

   TLV: Type 17 message element is included.

                    +-----------------------------+
                    | Configuration Data Response |
                    +-----------------------------+
                    |           Result            |
                    +-----------------------------+

   Message: Configuration Trigger
   Direction: AC -> WTP
   Type: Request

   Description: This message is used to trigger the activation of the
   configuration information sent in earlier Configuration messages.

   Message: Configuration Trigger Response
   Direction: WTP -> AC
   Type: Response

   Description: This is an acknowledgement of the Configuration Trigger.
   This response message is sent before activation of the configuration
   information.

   TLV: Message elements of type 17 are included.

                   +--------------------------------+
                   | Configuration Trigger Response |
                   +--------------------------------+
                   |             Result             |
                   +--------------------------------+

   Message: Reset
   Direction: AC -> WTP
   Type: Request

   Description: This message from the AC instructs the WTP to clear
   registers and revert to initial conditions.

   Message: Reset Response
   Direction: WTP -> AC
   Type: Response

   Description: This is an acknowledgement for the Reset message to the
   AC.

   TLV: Message elements of type 17 are included.

                           +----------------+
                           | Reset Response |
                           +----------------+
                           |     Result     |
                           +----------------+

   Message: Feedback
   Direction: WTP <-> AC
   Type: Request

   Description:
        WTP: The Feedback message is used to send regular statistics
             information to the AC.  It also serves as a keepalive
             indicator used to update the Active Presence Timer
             maintained by the AC.
        AC:  The Feedback message is used to determine the active state
             of WTPs.

   TLV: This message includes message elements of type 12.

                            +-------------+
                            |   Feedback  |
                            +-------------+
                            | Statistics  |
                            +-------------+

   Message: Feedback Response
   Direction: WTP <-> AC
   Type: Response

   Description: This is an acknowledgement for Feedback messages.

   TLV: Message elements of type 17 are included.

                         +-------------------+
                         | Feedback Response |
                         +-------------------+
                         |      Result       |
                         +-------------------+

   Message: Firmware Download
   Direction: AC -> WTP
   Type: Request

   Description: This message is used to instruct WTPs to update their
   firmware.  The message element contains information regarding the new
   firmware.

   TLV: Message elements of type 16 are included.

                         +-------------------+
                         | Firmware Download |
                         +-------------------+
                         |     TFTP-Data     |
                         +-------------------+

   Message: Firmware Download Response
   Direction: WTP -> AC
   Type: Request Response

   Description: This is an acknowledgement for the Firmware Download
   message.

   TLV: Message elements of type 17 are included.

                     +----------------------------+
                     | Firmware Download Response |
                     +----------------------------+
                     |           Result           |
                     +----------------------------+

   Message: Notification
   Direction: WTP <-> AC
   Type: Request

   Description: This message is used to indicate non-periodic events.
   It may be sent by either WTPs or the AC.  Notification messages
   indicate failures, non-periodic changes, etc.

   TLV: Message elements of types 13 and 14 are included.

                          +------------------+
                          |   Notification   |
                          +------------------+
                          | Interface-Error  |
                          |                  |
                          |    FROM-Error    |
                          +------------------+

   Message: Notification Response
   Direction: WTP <-> AC
   Type: Response

   Description: This is an acknowledgement for the Notification message.
   It may be followed by Configuration messages to rectify errors.

   TLV: Message elements of type 17 are included.

                       +-----------------------+
                       | Notification Response |
                       +-----------------------+
                       |        Result         |
                       +-----------------------+

   Message: Terminal Addition
   Direction: WTP <-> AC
   Type: Request

   Description: This message may be sent from WTPs or the AC, depending
   on the WTP type in consideration.  In both cases, it is sent in
   response to an IEEE 802.11 association frame.

   For Split MAC WTPs, Terminal Addition is sent from the AC to the WTPs
   and includes information on the wireless terminal relevant to the
   WTP.

   For Local MAC WTPs, Terminal Addition is sent from a WTP to the AC
   and contains information on the wireless terminal relevant to the AC.

   TLV: Message elements of type 8 are included.

                         +-------------------+
                         | Terminal Addition |
                         +-------------------+
                         |   Terminal-Data   |
                         +-------------------+

   Message: Terminal Addition Response
   Direction: WTP <-> AC
   Type: Response

   Description: This is an acknowledgement sent from either WTPs or the
   AC, depending on the WTP type in consideration.

   TLV: Message elements of type 17 are included.

                     +----------------------------+
                     | Terminal Addition Response |
                     +----------------------------+
                     |           Result           |
                     +----------------------------+

   Message: Terminal Deletion
   Direction: WTP <-> AC
   Type: Request

   Description: This message is sent in response to a disconnection of a
   wireless terminal.  It can be sent from WTPs or the AC.  In both
   cases, Terminal Deletion instructs the recipient to remove any state
   information relating to the specific wireless terminal.  The message

   is sent in response to an IEEE 802.11 disassociation frame, IEEE
   802.11 deauthentication frame, or due to the expiration of the Active
   Presence Timer.

   For Split MAC WTPs, Terminal Deletion is sent from the AC to the
   WTPs.

   For Local MAC WTPs, Terminal Deletion is sent from the WTPs to the
   AC.

   TLV: Message elements of type 9 are included.

                         +-------------------+
                         | Terminal Deletion |
                         +-------------------+
                         |       BSSID       |
                         +-------------------+

   Message: Terminal Deletion Response
   Direction: WTP <-> AC
   Type: Response

   Description: This is an acknowledgement sent from either WTPs or the
   AC, depending on the WiCoP interface.

   TLV: Message elements of type 17 are included.

                     +----------------------------+
                     | Terminal Addition Response |
                     +----------------------------+
                     |           Result           |
                     +----------------------------+

   Message: Key Configuration
   Direction: AC -> WTP
   Type: Request

   Description: This message is used when authentication and encryption
   points are located in distinct WLAN entities.  WiCoP uses it in cases
   where 'M' = 0 and 'D' = 0 or where 'M' = 1 and 'D' = 1.  It is used
   to configure security key information from the AC to the WTPs.

   TLV: The following message elements are included for Key
   Configuration.

                         +-------------------+
                         | Key Configuration |
                         +-------------------+
                         |     GTK-Flag      |
                         |                   |
                         |  Encryption-Data  |
                         |                   |
                         |     EAP-Frame     |
                         +-------------------+

   Message: Key Configuration Response
   Direction: WTP -> AC
   Type: Response

   Description: This is an acknowledgement for the Key Configuration
   message.

   TLV: Message elements of type 17 are included.

                     +----------------------------+
                     | Key Configuration Response |
                     +----------------------------+
                     |           Result           |
                     +----------------------------+

4.3.  WiCoP Data Packet

   WiCoP data packets include the WiCoP common header followed by a
   payload.  Data packets are used to distinguish traffic from control
   when both control and data paths are identical.  Such a scenario
   would involve data traffic of the WTPs traversing the AC.  However,
   given the diversity of large-scale WLAN deployments, there are
   scenarios in which data and control paths are distinct.  WiCoP can be
   used in both cases.

   The WiCoP data packet format is illustrated below in Figure 7,
   together with the WiCoP common header.

   0                                                              31
   |                7               15              23             |
   |-------|-------|-------|-------|-------|-------|-------|-------|
   |                                                               |

   +---------------+-+-+-+-+-+-+-+-+-------------------------------+
   |    Version    |M|D|C|R|E|F|L| |           Reserve             |
   +---------------+-+-+-+-+-+-+-+-+-------------------------------+
   |  Fragment ID  | Fragment No.  |           Length              |
   +---------------+---------------+-------------------------------+
   |                            Payload                            |
   +---------------------------------------------------------------+

                                 Figure 7

4.4.  WiCoP Timers

   WiCoP uses a number of timers to determine WLAN status and maintain
   system performance.  Timers are maintained by all WiCoP entities.

4.4.1.  Active Presence Timer

   The Active Presence Timer is used by each WiCoP entity -- AC and WTPs
   -- to verify the presence of each other.  The absence of a reply to
   the Feedback message within the expiration of the Active Presence
   Timer indicates the corresponding entity is inactive.  Contingency
   operations such as reset are used in this case.  The value of the
   Active Presence Timer ranges from 10 to 300 seconds with a default
   value of 30 seconds.

4.4.2.  Feedback Interval

   Feedback messages are periodic with the frequency defined by the
   Feedback Interval.  The interval is set during WTP configuration.  It
   has a value ranging from 1 to 100 seconds and a default value of 10
   seconds.

   The Feedback Interval timer sets the periodicity of WLAN system
   audits.  So with this timer, the WLAN controller receives regular
   information on the state of the WLAN and all its WTPs.

4.4.3.  Response Timer

   This is a general-purpose timer used to limit the elapsed time
   between transmission of a request message and receipt of a
   corresponding response message.  The value of this timer ranges from
   1 to 3 seconds with a default value of 1 second.

4.4.4.  Wireless Connectivity Timer

   This timer triggers any changes in wireless connectivity.  WiCoP uses
   this timer to send Notification and other messages relating to
   wireless conditions.  It is also used to trigger the disconnection of
   mobile terminals without disassociation.  The value of the Wireless
   Connectivity Timer ranges from 1 minute to 86,400 minutes with a
   default value of 10 minutes.

5.  WiCoP Processes

   The processes of the Wireless LAN Control Protocol are described in
   this section with respect to the operational state in which they
   occur.

5.1.  Initialization

   The Initialization state represents the initial conditions of WiCoP
   entities.  WTPs and ACs in this state are powered on, run hardware
   self-check tests, and reset network interfaces.

   State transition: Initialization -> Capabilities Exchange
        WTP: Automatically upon detecting an active network interface
         AC: Upon receiving a Capabilities message from a WTP

5.2.  Capabilities Exchange

   The Capabilities Exchange state allows WTPs to first find an AC and
   then to exchange capabilities information with it.

   WiCoP is designed to control WLANs with both Local MAC and Split MAC
   WTPs.  The differences in their respective functional characteristics
   are determined in this state.

   The WTP first broadcasts a Capabilities message as soon as it
   transitions from its Initialization state.  The Capabilities message
   serves to discover ACs and contains information on its identity and
   capabilities.

   The AC receiving the Capabilities message transitions from its
   Initialization state.  It examines compatibility with respect to the
   WTP type, its capabilities, and responds with an appropriate
   Capabilities Response message.

   The WTP continues to send Capabilities messages at an interval
   specified by the Response Timer until it receives a Capabilities
   Response message from an AC.

   The AC maintains a count of Capabilities messages received from a
   given WTP, which it uses to ignore WTPs after a limit.  This is to
   ensure that rogue WTPs that are not compatible with the AC do not
   repeatedly attempt connections.  The limit of connection attempts is
   3 within 60 seconds.

   State transition: Capabilities Exchange -> Connection
        WTP: Upon receiving a positive Capabilities Response message
             from an AC
         AC: Upon receiving a Connection Request message from a WTP

5.3.  Connection

   The Connection state involves establishing a security infrastructure
   between WTPs and an AC.

   The WTP sends a Connection message to trigger the authentication and
   security mechanism, i.e., this message initiates an IPsec security
   association.

   The AC sends a positive Connection Response message after
   establishment of the security association or a negative Connection
   Response message if an error occurs.  The AC also monitors the
   receipt of WiCoP control messages to prevent replay attacks.

   The security association between an AC and WTPs covers mutual
   authentication and also protection for integrity, confidentiality,
   and modification protection for subsequent traffic exchanges.

   In order to avoid forceful disconnections of legitimate WTPs after a
   successful Connection, the AC ignores Capabilities messages received
   with a previously registered WTP identification.

   State transition: Connection -> Configuration
        WTP: Upon successful establishment of security infrastructure
             marked by sending of a Configuration Request message
         AC: Upon receiving Configuration Request message from a WTP
             after successful establishment of security infrastructure

   State transition: Connection -> Capabilities Exchange
        WTP: Upon expiry of the WTP Response Timer before receipt of a
             positive Connection Response message from an AC or upon
             receipt of a negative Connection Response message
         AC: Upon expiry of AC Response Timer before receipt of
             Configuration Request message from WTP

5.4.  Configuration

   The Configuration state is one in which relatively long-term
   operational parameters, such as those for identification and logical
   groups, are exchanged.  These parameters are based on previously
   exchanged capabilities information and network policies.

   The WTP sends a Configuration Request message to the AC.

   The AC first acknowledges the WTP's Configuration Request, after
   which it sends appropriate configuration information in subsequent
   Configuration Data messages.  WiCoP includes MIB objectives as
   message elements in some Configuration Data messages so as to
   simplify WTP configuration.

   The WTP acknowledges Configuration Data messages individually or en
   bloc with Configuration Data Response messages.  The Response Timer
   is maintained at both WTP and AC to track the exchanges.

   The AC also establishes relevant processing schedules according to
   the WTP's architecture design.  For example, for Split MAC WTPs, the
   AC arranges its processing schedule to parse IEEE 802.11 control and
   management messages while for Local MAC WTPs, the AC arranges
   schedules processing so as to bypass parsing of IEEE 802.11
   management messages.

   The AC sends a Configure Trigger message after sending all relevant
   configuration information to the WTP.

   The WTP acknowledges a Configure Trigger message with a Configure
   Trigger Response message before activating the previously exchanged
   configuration parameters.

   In order to avoid forceful disconnections of legitimate WTPs after
   successful Configuration, the AC ignores Capabilities messages
   received with a previously registered WTP identification.

   State transition: Configuration -> Operation
        WTP: After receiving final Configuration Data message from the
             AC marked by receipt of a Configure Trigger message from
             the AC
         AC: Upon receiving acknowledgement for Configure Trigger
             message marked by receipt of a Configure Trigger Response
             message from WTP

   State transition: Configuration -> Capabilities Exchange
        WTP: Upon expiry of the WTP Response Timer before receipt of a
             Configure Trigger message from the AC

         AC: Upon expiry of the AC Response Timer before receipt of
             Configure Data Response message or Configure Trigger
             Response message

   The following describes major configuration aspects of WiCoP.

5.4.1.  Logical Groups

   Configuration Data messages are used to establish logical groups in
   the WLAN and also to separate traffic among them.  The logical groups
   are established based on network administrative policies and other
   external considerations.  In the IEEE 802.11 use-case, logical groups
   are established with BSSID-based virtual APs and are separated over
   the WiCoP interface using tunnels.

   The AC assigns particular BSSIDs of the WTP to specific VLAN tunnels.
   This assignment is specified to the WTP using the BSSID-TunnelID
   parameter in the Configuration Data message.  The logical group
   mapping therefore works across the wireless and WiCoP interfaces.

   The WTP then identifies the specified BSSID and VLAN tunnel as
   corresponding to one logical group.  It creates internal state such
   that traffic belonging to the logical group is kept distinct from
   that of other logical groups.

   The AC and WTP also use distinct VLAN tunnels for data and control
   traffic.  The 'C' field in the WiCoP header is used to distinguish
   and assign WiCoP packets to particular data and control VLAN tunnels.

5.4.2.  Resource Control

   The AC sends QoS information using QoS-Value message elements in
   Configuration Data messages.  The QoS-Value message element contains
   values for EDCA and HCCA parameters.  This information is specified
   for each of the logical groups.  In the IEEE 802.11 use-case, QoS-
   Value message elements are specified for each BSSID.

   The WTP configures QoS parameters locally and also forwards relevant
   settings to wireless terminals in appropriate encapsulations.  In the
   IEEE 802.11 use-case, QoS parameters are sent to wireless terminals
   in corresponding Beacon or Probe Response frames.

5.5.  Operation

   This is the active operation state of the WLAN in which short-term
   dynamics are examined.

   The WTP begins operations according to the operational parameters
   exchanged in the previous Configuration state.

   The AC monitors WTPs according to network administrative policies and
   configurations.

   In order to avoid forceful disconnections of legitimate WTPs after
   successful Operation setup, the AC ignores Capabilities messages
   received with a previously registered WTP identification.

   State transition: Operation -> Capabilities Exchange
        WTP: Upon expiry of the WTP Active Presence Timer before receipt
             of a Feedback Response message from the AC
         AC: Upon expiry of the AC Active Presence Timer before receipt
             of a Feedback message from the WTP

   State transition: Operation -> Initialization
        WTP: Upon receipt of a Reset message from an AC
         AC: Upon receipt of a Reset Response message from a WTP

   The following describes major operation aspects of WiCoP.

5.5.1.  Updates

   The dynamic nature of WLAN systems requires regular updates to
   network operations.

   The AC sends additional configuration information in the
   Configuration Data messages.  This is applicable to establishment of
   new logical groups, changes to existing logical groups, changes in
   QoS settings, etc.  Configuration information is followed by a
   Configure Trigger message.

   The WTP sends a Configure Trigger Response before activating the
   additional configuration information.

   Configuration updates can be used to clear statistics information by
   reflecting initial values.

   An extreme case of a configuration update involves use of the Reset
   message from the AC, which instructs the WTP to revert to initial
   conditions.  The WTP replies with a Reset Response message before
   reverting to its initial state.

5.5.2.  Feedback and Statistics

   The Operation state also sees regular feedback being sent by WTPs to
   the AC.

   The WTP sends Feedback messages to indicate various statistics and
   congestion condition information.  Feedback also includes information
   on the state of the WTP and wireless medium such as queue levels and
   channel interference.  Feedback messages are sent with a frequency
   defined by the Feedback Interval.  In addition to statistics, the
   Feedback message also serves as a WTP keepalive indicator to the AC.
   Feedback messages combine statistics information together with WTP
   status information.

   The AC monitors Feedback messages for their statistics value and
   implicit indication of WTP activity.  The AC also tracks the state of
   congestion at wireless terminals and WTPs.  This information enables
   the AC to adapt its downstream transmissions, such as scheduling
   transmission away from congested WTPs, so as to relieve congestion.

   The AC additionally uses the Feedback message to randomly determine
   the active state of WTPs.  An active WTP replies with a corresponding
   Feedback Response message.

5.5.3.  Non-Periodic Events

   The WTP and AC use the Notification message for non-periodic events.
   They send Notification messages to indicate error conditions or
   drastic changes in congestion state.

   The recipient of the Notification message acknowledges with a
   Notification Response message.  The response may contain information
   on rectifying the error or may simply be an acknowledgement of the
   Notification.

5.5.4.  Firmware Trigger

   The AC sends a Firmware Download message to update firmware at WTPs.
   The Firmware Download message contains TFTP information, which the
   WTP uses to refresh its firmware.  This is used when a new version of
   firmware is available for the WTPs.

   The WTP acknowledges new firmware with a Firmware Download Response
   message after which it is activated.

5.5.5.  Wireless Terminal Management

   The Operation state of WiCoP also involves configuration of WTPs and
   the AC with wireless terminal-specific information.

   Here the Terminal Addition message is used in response to a new
   wireless terminal entering the WLAN.  This message may be sent by
   either the WTPs or the AC, depending on the WiCoP interface being
   used.  The recipient of this message replies with the Terminal
   Addition Response message.

   The Terminal Deletion message is used when a wireless terminal leaves
   the WLAN.  This is used to delete state information that was
   maintained by either the WTPs or the AC.  It is acknowledged with the
   Terminal Deletion Response message.

   Figure 8 below illustrates the exchange of Terminal Addition and
   Terminal Deletion messages for both Local-MAC- and Split-MAC-based
   WiCoP interfaces.

   Here the WiCoP Terminal Addition message is triggered as a response
   to an IEEE 802.11 Association message.  In the case of Local MAC
   architecture, the WTP sends the message to the AC.  However, in the
   Split MAC architecture, Terminal Addition is sent from an AC to the
   WTP.

   +----------+           +---------------+                 +------+
   | Terminal |           | Local MAC WTP |                 |  AC  |
   +----------+           +---------------+                 +------+
        |                          |                            |
        |                          |                            |
        | IEEE 802.11 Association  |           WiCoP            |
        |------------------------->|     Terminal Addition      |
        |                          |===========================>|
        |                          |                            |
        |                          |      WiCoP Terminal        |
        |                          |<===========================|
        | IEEE 802.11 Association  |    Addition Response       |
        |<-------------------------|                            |
        |      Response            |                            |
        |                          |                            |
        |                          |                            |
        |                                                       |
        |                                                       |
        |                                                       |
        |                  +---------------+                    |
        |                  | Split MAC WTP |                    |
        |                  +---------------+                    |
        |                          |                            |
        |                          |                            |
        | IEEE 802.11 Association  |                            |
        |------------------------->|                            |
        |                          |  IEEE 802.11 Association   |
        |                          |===========================>|
        |                          |       (Over WiCoP)         |
        |                          |                            |
        |                          |                            |
        |                          |           WiCoP            |
        |                          |      Terminal Addition     |
        |                          |<===========================|
        |                          |                            |
        |                          |                            |
        |                          |      WiCoP Terminal        |
        |                          |===========================>|
        |                          |    Addition Response       |
        |                          |                            |
        |                          |                            |
        |                          |  IEEE 802.11 Association   |
        |                          |<===========================|
        |                          |   Response (Over WiCoP)    |
        | IEEE 802.11 Association  |                            |
        |<-------------------------|                            |
        |       Response           |                            |
                                 Figure 8

5.5.6.  Key Configuration

   One of the differences between Split MAC and Local MAC WTPs is the
   location of the over-the-air encryption.  Some Split MAC and Local
   MAC WTPs perform encryption locally while others leave it to the AC.
   WiCoP accommodates these differences by enabling security key
   configuration in those cases where encryption is performed at the
   WTP.  The encryption setup process is therefore contingent on the
   WiCoP protocol interface.

   When dynamic WEP is used, the WiCoP Key Configuration message is used
   to notify WTPs of encryption keys for each associated wireless
   terminal.  Here, the EAP over LAN (EAPoL) Key frame is encapsulated
   in the Key Configuration message and sent to a WTP.  Upon receiving
   the Key Configuration message, the WTP sets the encryption key in its
   local security table, decapsulates the EAPOL Key frame and forwards
   it to the wireless terminal.  This is illustrated in Figure 9.

   +----------+                 +-----+                     +------+
   | Terminal |                 | WTP |                     |  AC  |
   +----------+                 +-----+                     +------+
        |                          |                            |
        |                    802.1x Authentication              |
        |<=====================================================>|
        |                          |                            |
        |                          |                            |
       PMK                         |                           PMK
        |                          |                            |
        |                          |                            |
        |<-------------------------|<===========================|
        |       EAPoL Packet       |     WiCoP Control Packet   |
        |                          |      (Key Configuration)   |
        |                          |      | +-----------------------+
        |                          |       \|- Encryption-Data      |
        |                          |        |    Unicast-Key        |
       Set                      Receive     |- EAP-Frame            |
     Unicast-Key              Unicast-Key   |    Key Signature      |
        |                          |        +-----------------------+
        |                          |                            |
        |                          |===========================>|
        |                          |     WiCoP Control Packet   |
        |                          |      (Key Configuration    |
        |                          |       Response )           |
        |                          |                            |
        |                          |                            |
        |                          |                            |
        |                          |                            |
        |<-------------------------|<===========================|
        |       EAPoL Packet       |     WiCoP Control Packet   |
        |                          |      (Key Configuration)   |
        |                          |      | +-----------------------+
        |                          |       \|- Encryption-Data      |
        |                          |        |     Broadcast-Key     |
       Set                      Receive     |- EAP-Frame            |
     Broadcast-Key            Broadcast-Key |    Key Signature      |
        |                          |        |    Broadcast Key      |
        |                          |        +-----------------------+
        |                          |                            |
        |                          |===========================>|
        |                          |     WiCoP Control Packet   |
        |                          |      (Key Configuration    |
        |                          |       Response )           |

                                 Figure 9

   When WPA or IEEE 802.11i is used in WLAN architectures in which the
   authenticator is located at the AC and encryption points at WTPs, the
   exchanges of the 4-way handshake are managed distinctly.  This is
   because the AC is no longer in a position to calculate the KeyMIC as
   it is not aware of the KeyRSC sequence counter.  So here, a WiCoP Key
   Configuration message is used to transport the 3rd message of the
   4-way handshake -- containing the EAPoL-Key -- with unassigned KeyRSC
   and KeyMIC fields.  When the WTP receives the WiCoP Key Configuration
   message, it first assigns the sequence number value to the KeyRSC
   field.  Then, the WTP calculates the KeyMIC value using the PTK and
   KeyRSC.  So, the WiCoP Key Configuration message allows the KeyMIC to
   be calculated at the WTPs instead of the AC.  The GTK-Flag message
   element is used to determine how the KeyMIC is calculated -- in case
   of a new GTK, KeyMIC is computed with a KeyRSC value of 0 and in case
   of an existing GTK, KeyMIC is computed with a KeyRSC value
   corresponding to the actual counter.

   Figure 10 illustrates this case where the WiCoP common header is
   either 'M' = 0 and 'D' = 0 or 'M' = 1 and 'D' = 1.

   +----------+                 +-----+                     +------+
   | Terminal |                 | WTP |                     |  AC  |
   +----------+                 +-----+                     +------+
        |                          |                            |
        |                    802.1x Authentication              |
        |<=====================================================>|
        |                          |                            |
       PMK                         |                           PMK
        |                          |                            |
      Generate                     |                        Generate
       SNonce                      |                         ANonce
        |                          |                            |
        |                          |                            |
        |                      Message 1                        |
        |<-------------------------|<---------------------------|
        |       EAPoL Packet       |      WiCoP Data Packet     |
      Receive                      |                            |
       ANonce                      |                            |
      Generate                     |                            |
       PTK                         |                            |
        |                          |                            |
        |                      Message 2                        |
        |------------------------->|--------------------------->|
        |       EAPoL Packet       |      WiCoP Data Pakcet     |
        |                          |                        Receive
        |                          |                        SNonce
        |                          |                            |
        |                          |                       Generate
        |                          |                          PTK
        |                          |                          GTK
        |                      Message 3                        |
        |<-------------------------|<===========================|
        |       EAPoL Packet       |     WiCoP Control Packet   |
        |                          |      (Key Configuration)   |
        |                          |      | +-----------------------+
        |                          |       \|- GTK-Flag             |
      Receive                    Receive    |- Encryption-Data(PTK) |
       GTK                        PTK       |- Encryption-Data(GTK) |
        |                         GTK       |- EAP-Frame            |
        |                          |        +-----------------------+
        |                          |                            |
        |                          |                            |
        |                          |                            |
        |                      Message 4                        |
        |------------------------->|--------------------------->|
        |       EAPoL Packet       |      WiCoP Data Pakcet     |
        |                          |                            |
                                 Figure 10

   The 1st, 2nd, and 4th messages of the 4-way handshake are transported
   in WiCoP data packets that are assigned priorities similar to that of
   WiCoP control packets.

   Similarly, for the group key handshake in WPA and IEEE 802.11i, the
   1st message of the handshake is transported using the WiCoP Key
   Configuration message with unassigned KeyRSC.  The WTP again assigns
   the sequence number value to the KeyRSC and then calculates the
   KeyMIC.  The 2nd message of the handshake however is transported in
   WiCoP data packets with priorities similar to that of WiCoP control
   packets.  This is illustrated in Figure 11.

   +----------+                 +-----+                     +------+
   | Terminal |                 | WTP |                     |  AC  |
   +----------+                 +-----+                     +------+
        |                          |                            |
        |                      Message 1                        |
        |<-------------------------|<===========================|
        |       EAPoL Packet       |     WiCoP Control Packet   |
        |                          |      (Key Configuration)   |
        |                          |      | +-----------------------+
        |                          |       \|- GTK-Flag             |
      Receive                    Receive    |- Encryption-Data(GTK) |
       GTK                        GTK       |- EAP-Frame            |
        |                          |        +-----------------------+
        |                          |                            |
        |                          |                            |
        |                          |                            |
        |                          |                            |
        |                      Message 2                        |
        |------------------------->|--------------------------->|
        |       EAPoL Packet       |      WiCoP Data Pakcet     |
        |                          |                            |

                                 Figure 11

   The Key Configuration Response message is used by the WTP to notify
   the AC of the encryption setup process.

6.  WiCoP Performance

   WiCoP is an efficient protocol.  This section illustrates various
   examples of its efficiency.

6.1.  Operational Efficiency

   The fact that WiCoP requires a single operation to distinguish and
   manage WTPs of different designs makes it operationally efficient.
   Because WiCoP assigns dedicated classification bits in the common
   header, an AC needs to parse incoming packets only once to determine
   the particular manner in which it is to be processed.  Without the
   dedicated classifications in the common header, an AC would have to
   perform a lookup after parsing every incoming packet, which would
   result in delaying processing.  The scale and sensitivity of large-
   scale deployments require that WLAN control protocols be efficient in
   operation.

6.2.  Semantic Efficiency

   In certain cases, WiCoP combines utilities in a single operation.
   One particular case is that of statistics and activity feedback.
   Here, WTPs regularly send a single Feedback message containing
   statistics and other state information, which also acts as an
   implicit keepalive mechanism.  This helps to reduce the number of
   message exchanges and also simplifies protocol implementation.
   Similarly, the Capabilities messages serve the purpose of finding ACs
   as well as informing them of WTP capabilities and design.

7.  Summary and Conclusion

   The Wireless LAN Control Protocol presents a solution for managing
   large-scale WLANs with diverse elements.  It addresses the challenges
   presented in the CAPWAP Problem Statement [RFC3990] and realizes the
   requirements of the CAPWAP Objectives [RFC4564].

   WiCoP enables integral control of Split MAC and Local MAC WTPs by
   defining appropriate differentiators within the protocol message
   exchanges and processes.  It addresses architecture designs in which
   the authenticator and encryption points are located on distinct
   entities.  In doing so, WiCoP realizes the interoperability objective
   and its benefits.

   WiCoP also addresses shared WLAN deployments by configuring and
   managing WTPs on a logical group basis.  It is further provisioned to
   separate control and data traffic within WLANs.  So, the protocol
   addresses the objectives of logical groups and traffic separation.

   Overall, the specifications presented in this document allow for an
   effective WLAN control and provisioning protocol.

8.  Security Considerations

   Illegitimate WTPs and ACs pose a significant threat to WLAN security.
   This can be mitigated by requiring all WiCoP entities to be mutually
   authenticated before initiating critical protocol exchanges.  WiCoP
   includes a trigger for a suitable authentication mechanism.  This is
   to accommodate a different security mechanism that may be used
   between WTPs and the AC, depending on the nature of the deployment.

   In extension to mutual authentication, the subsequent exchange of
   protocol information between WTPs and the AC need to be protected.
   The exchanges have to be protected against alterations of any sort
   and Denial-of-Service (DoS) attacks.  Also, the information should
   not be accessible to any third party.  Encryption of protocol
   exchanges is therefore necessary.  WiCoP includes appropriate
   procedures to select and establish a security association between
   WTPs and the AC in the Connection state.

   Architecture designs in which authentication is performed at the AC
   and encryption at the WTPs can be exposed to the threat of replay
   attacks.  Since the AC will not be aware of the exact value of the
   sequence counter, it will not make the corresponding assignment
   within the 4-way handshake.  This leaves the wireless terminal to
   accept all incoming frames, including illegitimate frames, as it
   cannot verify the sequence counter value.  Such a threat needs to
   protected against by allowing the WTP to assign the correct value of
   the sequence counter.  WiCoP accomplishes this by sending the 3rd
   message of the 4-way handshake within a control message to the WTP,
   which then updates the sequence counter field before forwarding it to
   the wireless terminals.

   Another issue to consider is that of rogue WTPs using identifiers
   similar to that of legitimate WTPs.  In such instances, a rogue WTP
   can send a Capabilities message to the AC, thereby causing
   disconnection of the existing legitimate WTP of the same identifier.
   It is important for the AC to ignore Capabilities messages received
   with existing identifiers.

9. Informative References

   [RFC4118]  Yang, L., Zerfos, P., and E. Sadot, "Architecture Taxonomy
              for Control and Provisioning of Wireless Access Points
              (CAPWAP)", RFC 4118, June 2005.

   [RFC4564]  Govindan, S., Ed., Cheng, H., Yao, ZH., Zhou, WH., and L.
              Yang, "Objectives for Control and Provisioning of Wireless
              Access Points (CAPWAP)", RFC 4564, July 2006.

   [RFC3990]  O'Hara, B., Calhoun, P., and J. Kempf, "Configuration and
              Provisioning for Wireless Access Points (CAPWAP) Problem
              Statement", RFC 3990, February 2005.

Authors' Addresses

   Satoshi Iino
   Panasonic Mobile Communications
   600, Saedo-cho
   Tsuzuki-ku
   Yokohama  224 8539
   Japan

   Phone: +81 45 938 3789
   EMail: iino.satoshi@jp.panasonic.com

   Saravanan Govindan
   Panasonic Singapore Laboratories
   Block 1022, Tai Seng Industrial Estate
   #06-3530, Tai Seng Avenue
   Singapore  534 415
   Singapore

   Phone: +65 6550 5441
   EMail: saravanan.govindan@sg.panasonic.com

   Mikihito Sugiura
   Panasonic Mobile Communications
   600, Saedo-cho
   Tsuzuki-ku
   Yokohama  224 8539
   Japan

   Phone: +81 45 938 3789
   EMail: sugiura.mikihito@jp.panasonic.com

   Hong Cheng
   Panasonic Singapore Laboratories
   Block 1022, Tai Seng Industrial Estate
   #06-3530, Tai Seng Avenue
   Singapore  534 415
   Singapore

   Phone: +65 6550 5447
   EMail: hong.cheng@sg.panasonic.com

 

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