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rfc:rfc4564

Network Working Group S. Govindan, Ed. Request for Comments: 4564 H. Cheng Category: Informational Panasonic

                                                               ZH. Yao
                                                                Huawei
                                                              WH. Zhou
                                                          China Mobile
                                                               L. Yang
                                                                 Intel
                                                             July 2006
                          Objectives for
    Control and Provisioning of Wireless Access Points (CAPWAP)

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

Abstract

 This document presents objectives for an interoperable protocol for
 the Control and Provisioning of Wireless Access Points (CAPWAP).  The
 document aims to establish a set of focused requirements for the
 development and evaluation of a CAPWAP protocol.  The objectives
 address architecture, operation, security, and network operator
 requirements that are necessary to enable interoperability among
 Wireless Local Area Network (WLAN) devices of alternative designs.

Govindan, et al. Informational [Page 1] RFC 4564 CAPWAP Objectives July 2006

Table of Contents

 1. Introduction ....................................................3
 2. Terminology .....................................................3
 3. Requirements Notation ...........................................4
 4. Objectives Overview .............................................4
 5. Objectives ......................................................5
    5.1. Mandatory and Accepted Objectives ..........................5
         5.1.1. Logical Groups ......................................5
         5.1.2. Support for Traffic Separation ......................6
         5.1.3. Wireless Terminal Transparency ......................8
         5.1.4. Configuration Consistency ...........................8
         5.1.5. Firmware Trigger ....................................9
         5.1.6. Monitoring and Exchange of System-wide
                Resource State .....................................10
         5.1.7. Resource Control Objective .........................11
         5.1.8. CAPWAP Protocol Security ...........................12
         5.1.9. System-wide Security ...............................14
         5.1.10. IEEE 802.11i Considerations .......................15
         5.1.11.  Interoperability Objective .......................17
         5.1.12.  Protocol Specifications ..........................18
         5.1.13.  Vendor Independence ..............................19
         5.1.14.  Vendor Flexibility ...............................19
         5.1.15.  NAT Traversal ....................................20
    5.2. Desirable Objectives ......................................21
         5.2.1. Multiple Authentication Mechanisms .................21
         5.2.2. Support for Future Wireless Technologies ...........21
         5.2.3. Support for New IEEE Requirements ..................22
         5.2.4. Interconnection Objective ..........................23
         5.2.5.  Access Control ....................................24
    5.3. Non-Objectives ............................................25
         5.3.1. Support for Non-CAPWAP WTPs ........................25
         5.3.2. Technical Specifications ...........................26
    5.4. Operator Requirements .....................................27
         5.4.1. AP Fast Handoff ....................................27
 6. Summary and Conclusion .........................................27
 7. Security Considerations ........................................28
 8. Acknowledgements ...............................................29
 9. Normative References ...........................................29
 10. Informative References ........................................29

Govindan, et al. Informational [Page 2] RFC 4564 CAPWAP Objectives July 2006

1. Introduction

 The growth in large-scale Wireless Local Area Network (WLAN)
 deployments has brought into focus a number of technical challenges.
 Among them is the complexity of managing large numbers of Wireless
 Termination Points (WTPs), which is further exacerbated by variations
 in their design.  Another challenge is the maintenance of consistent
 configurations among the numerous WTPs of a system.  The dynamic
 nature of the wireless medium is also a concern together with WLAN
 security.  The challenges affecting large-scale WLAN deployments have
 been highlighted in [RFC3990].
 Many vendors have addressed these challenges by developing new
 architectures and solutions.  A survey of the various developments
 was conducted to better understand the context of these challenges.
 This survey is a first step towards designing interoperability among
 the solutions.  The Architecture Taxonomy [RFC4118] is a result of
 this survey in which major WLAN architecture families are classified.
 Broadly, these are the autonomous, centralized WLAN, and distributed
 mesh architectures.
 The Architecture Taxonomy identified the centralized WLAN
 architecture as one in which portions of the wireless medium access
 control (MAC) operations are centralized in a WLAN controller.  This
 centralized WLAN architecture is further classified into remote-MAC,
 split-MAC, and local-MAC designs.  Each differs in the degree of
 separation of wireless MAC layer capabilities between WTPs and WLAN
 controller.
 This document puts forward critical objectives for achieving
 interoperability in the CAPWAP framework.  It presents requirements
 that address the challenges of controlling and provisioning large-
 scale WLAN deployments.  The realization of these objectives in a
 CAPWAP protocol will ensure that WLAN equipment of major design types
 may be integrally deployed and managed.

2. Terminology

 This document uses terminology defined in [RFC4118], [802.11],
 [802.11i], and [802.11e].  Additionally, the following terms are
 defined.
 Centralized WLAN: A WLAN based on the centralized WLAN Architecture
 [RFC4118].
 Switching Segment: Those aspects of a centralized WLAN that primarily
 deal with switching or routing of control and data information
 between Wireless Termination Points (WTPs) and the WLAN controller.

Govindan, et al. Informational [Page 3] RFC 4564 CAPWAP Objectives July 2006

 Wireless Medium Segment: Those aspects of a centralized WLAN that
 primarily deal with the wireless interface between WTPs and wireless
 terminals.  The Wireless Medium Segment is specific to layer 2
 wireless technology, such as IEEE 802.11.
 CAPWAP Framework: A term that covers the local-MAC and split-MAC
 designs of the Centralized WLAN Architecture.  Standardization
 efforts are focused on these designs.
 CAPWAP Protocol: The protocol between WLAN controller and WTPs in the
 CAPWAP framework.  It facilitates control, management, and
 provisioning of WTPs in an interoperable manner.
 Logical Group: A logical separation of a physical WTP is termed
 logical group.  So a single physical WTP will operate a number of
 logical groups.  Virtual access points (APs) are examples of logical
 groups.  Here, each Basic Service Set Identifier (BSSID) and
 constituent wireless terminals' radios are denoted as distinct
 logical groups of a physical WTP.  Logical groups are maintained
 without conflicting with the CAPWAP objectives, particularly the
 'Wireless Terminal Transparency' objective.

3. Requirements Notation

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

4. Objectives Overview

 The objectives for CAPWAP have been broadly classified to address
 architecture, operation, and security requirements of managing
 large-scale WLAN deployments.
 Architecture objectives deal with system-level aspects of the CAPWAP
 protocol.  They address issues of protocol extensibility, diversity
 in network deployments and architecture designs, and differences in
 transport technologies.
 Operational objectives address the control and management features of
 the CAPWAP protocol.  They deal with operations relating to WLAN
 monitoring, resource management, Quality of Service (QoS), and access
 control.
 Security objectives address potential threats to WLANs and their
 containment.  In the CAPWAP context, security requirements cover the
 protocol between the WLAN controller and WTPs and also the WLAN
 system as a whole.

Govindan, et al. Informational [Page 4] RFC 4564 CAPWAP Objectives July 2006

 Additionally, a general classification is used for objectives
 relating to the overall impact of the CAPWAP protocol specifications.

5. Objectives

 The objectives described in this document have been prioritized based
 on their immediate significance in the development and evaluation of
 a control and provisioning protocol for large-scale WLAN deployments.
 The priorities are:
 i.  Mandatory and Accepted Objectives
 ii.  Desirable Objectives
 iii.  Non-Objectives
 The priorities have been assigned to individual objectives in
 accordance with working group discussions.
 Furthermore, a distinct category of objectives is provided based on
 requirements gathered from network service operators.  These are
 specific needs that arise from operators' experiences in deploying
 and managing large-scale WLANs.
 a. Operator Requirements

5.1. Mandatory and Accepted Objectives

 Objectives prioritized as mandatory and accepted have been deemed
 crucial for the control and provisioning of WTPs.  They directly
 address the challenges of large-scale WLAN deployments and MUST be
 realized by a CAPWAP protocol.

5.1.1. Logical Groups

 Classification: Architecture
 Description:
 Large WLAN deployments are complex and expensive.  Furthermore,
 enterprises deploying such networks are under pressure to improve the
 efficiency of their expenditures.
 Shared WLAN deployments, where a single physical WLAN infrastructure
 supports a number of logical networks, are increasingly used to
 address these two issues of large-scale WLANs.  These are popular as
 they allow deployment and management costs to be spread across
 businesses.

Govindan, et al. Informational [Page 5] RFC 4564 CAPWAP Objectives July 2006

 In traditional WLANs, each physical WTP represents one complete
 subset of a larger WLAN system.  Shared WLANs differ in that each
 physical WTP represents a number of logical subsets of possibly a
 number of larger WLAN systems.  Each logical division of a physical
 WTP is referred to as a logical group (see definition in Section 2).
 So WLANs are managed in terms of logical groups instead of physical
 WTPs.  Logical groups are based on BSSIDs and other types of virtual
 APs.
 Protocol Requirement:
 The CAPWAP protocol MUST be capable of controlling and managing
 physical WTPs in terms of logical groups including BSSID-based
 groups.
 For all operating modes, including those in which the WTP performs
 local bridging and those in which the Access Controller (AC) performs
 centralized bridging, the protocol MUST provide provisions for
 configuring logical groups at the WTP.
 Motivation and Protocol Benefits:
 Commercial realities necessitate that WLANs be manageable in terms of
 their logical groups.  This allows separation of logical services and
 underlying infrastructure management.  A protocol that realizes this
 need ensures simpler and cost-effective WLANs, which directly address
 the requirements of network service operators.
 Relation to Problem Statement:
 This objective addresses the problem of management complexity in
 terms of costs.  Cost complexity is reduced by sharing WLAN
 deployments.  Consequently, deployment and management cost-
 efficiencies are realized.

5.1.2. Support for Traffic Separation

 Classification: Operations
 Description:
 The centralized WLAN architecture simplifies complexity associated
 with large-scale deployments by consolidating portions of wireless
 MAC functionality at a central WLAN controller and distributing the
 remaining across WTPs.  As a result, WTPs and WLAN controller
 exchange control and data information between them.  This objective

Govindan, et al. Informational [Page 6] RFC 4564 CAPWAP Objectives July 2006

 states that control and data aspects of the exchanges be mutually
 separated for further simplicity.  This will allow solutions for each
 type of exchange to be independently optimized.
 Furthermore, in the context of shared WLAN deployments, the mutual
 separation of control and data also addresses security concerns.  In
 particular, given the likelihood of different logical groups, such as
 those established by different virtual APs, being managed by
 different administrators, separation of control and data is a first
 step towards individually containing and securing the logical groups.
 It is also important to ensure that traffic from each logical group
 is mutually separated to maintain the integrity and independence of
 the logical groups.
 Protocol Requirement:
 The CAPWAP protocol MUST define transport control messages such that
 the transport of control messages is separate from the transport of
 data messages.
 Motivation and Protocol Benefits:
 The aim of separating data and control aspects of the protocol is to
 simplify the protocol.  It also allows for the flexibility of
 addressing each type of traffic in the most appropriate manner.
 Furthermore, this requirement will help remotely located WTPs to
 handle data traffic in alternative ways without the need for
 forwarding them across a wide network to the WLAN controller.
 Separation of WTP control and data also aids in the secure
 realization of shared WLAN deployments.
 Relation to Problem Statement:
 Broadly, this objective relates to the challenge of managing
 complexity in large-scale WLANs.  The requirement for traffic
 separation simplifies control as this is separated from the task of
 data transport.

Govindan, et al. Informational [Page 7] RFC 4564 CAPWAP Objectives July 2006

5.1.3. Wireless Terminal Transparency

 Classification: Operations
 Description:
 The CAPWAP protocol is applicable between a centralized WLAN
 controller and a number of WTPs; i.e., it affects only the switching
 segment of the centralized WLAN architecture.  Its operations should
 therefore be independent of the wireless terminal.  Wireless
 terminals should not be required to be aware of the existence of the
 CAPWAP protocol.
 Protocol Requirement:
 Wireless terminals MUST NOT be required to recognize or be aware of
 the CAPWAP protocol.
 Motivation and Protocol Benefits:
 IEEE 802.11-based wireless terminals are mature and widely available.
 It would be beneficial for CAPWAP not to impose new requirements on
 these wireless terminals.  In effect, this requirement ensures that
 the setup cost of the protocol is reduced as the numerous existing
 wireless terminals need not be altered.
 Relation to Problem Statement:
 The Problem Statement highlights the challenges faced by large WLANs
 consisting of many WTPs.  It does not refer to the operations of
 wireless terminals and this objective emphasizes the independence.

5.1.4. Configuration Consistency

 Classification: Operations
 Description:
 WLANs in the CAPWAP framework contain numerous WTPs, each of them
 needing to be configured and managed in a consistent manner.  The
 main concern in ensuring consistency is availability of appropriate
 information corresponding to WTP configuration states.  So
 configuration consistency can be achieved by providing the
 centralized WLAN controller with regular updates on the state of WTP
 operations.  The centralized WLAN controller can in turn apply
 information from the regular updates to ensure consistently among the
 WTPs.

Govindan, et al. Informational [Page 8] RFC 4564 CAPWAP Objectives July 2006

 Protocol Requirement:
 The CAPWAP protocol MUST include support for regular exchanges of
 state information between WTPs and the WLAN controller.  Examples of
 state information include WTP processing load and memory utilization.
 Motivation and Protocol Benefits:
 A protocol that provides access to regular state information can in
 turn be used to enhance WLAN configuration and performance.  The
 CAPWAP protocol will be better equipped to address configuration-
 related problems with the regularly available state information.  So
 with greater state information, control and management operations can
 be improved.
 Relation to Problem Statement:
 One of the major challenges described in the Problem Statement is
 that of maintaining consistent configuration across the numerous WTPs
 of a WLAN.  This objective addresses the fundamental issue behind
 this -- availability of timely state information.

5.1.5. Firmware Trigger

 Classification: Operations
 Description:
 One specific aspect of configuration consistency is the firmware used
 by various WTPs.  The scale of large WLANs introduces possibilities
 for variations in the firmware used among WTPs.  This objective
 highlights the need for the CAPWAP protocol to trigger the delivery
 of appropriate versions of firmware to WTPs.  The actual delivery of
 firmware need not be inclusive to the protocol.
 Protocol Requirement:
 The CAPWAP protocol MUST support a trigger for delivery of firmware
 updates.
 Motivation and Protocol Benefits:
 The CAPWAP protocol interfaces many WTPs to a centralized WLAN
 controller.  Firmware distribution allows these interfaces to be
 compatible.  This in turn results in consistent configuration and
 simplified management.  So the protocol benefits by including
 triggers for the distribution of firmware updates.

Govindan, et al. Informational [Page 9] RFC 4564 CAPWAP Objectives July 2006

 Relation to Problem Statement:
 Inconsistencies in the configuration of WTPs have been identified as
 a major challenge for large-scale WTPs.  This objective helps
 overcome the challenge by providing a way for the CAPWAP protocol to
 initiate delivery of firmware updates that are compatible among all
 WTPs.

5.1.6. Monitoring and Exchange of System-wide Resource State

 Classification: Operations
 Description:
 The centralized WLAN architecture is made up of a switching segment
 and wireless medium segment.  In the switching segment, network
 congestion, WTP status, and firmware information have to be
 monitored.  In the wireless medium segment, the dynamic nature of the
 medium itself has to be monitored.  Overall, there are also various
 statistics that need to be considered for efficient WLAN operation.
 The CAPWAP protocol should be capable of monitoring the various
 information sources and deliver the resulting information to the
 relevant WLAN devices -- either WTPs or the WLAN controller.
 Moreover, given the relationship among information sources, the
 CAPWAP protocol should combine state information from them.  For
 example, statistics information and status signals from WTPs may be
 merged before being exchanged.
 Examples of statistics information that the CAPWAP protocol should
 monitor and exchange include congestion state, interference levels,
 loss rates, and various delay factors.
 Protocol Requirement:
 The CAPWAP protocol MUST allow for the exchange of statistics,
 congestion, and other WLAN state information.
 Motivation and Protocol Benefits:
 The effectiveness of a protocol is based on the relevance of
 information on which it operates.  This requirement for resource
 monitoring and exchange can provide the appropriate information to
 the CAPWAP protocol.

Govindan, et al. Informational [Page 10] RFC 4564 CAPWAP Objectives July 2006

 Relation to Problem Statement:
 The Problem Statement highlights the challenge of dealing with large
 numbers of WTPs and the dynamic nature of the wireless medium.
 Information on the state of WTPs and the medium is important to deal
 with them effectively.  So this objective relates to the problem of
 managing consistency in large WLANs.

5.1.7. Resource Control Objective

 Classification: Operations
 Description:
 Integral to the success of any wireless network system is the
 performance and quality it can offer its subscribers.  Since CAPWAP-
 based WLANs combine a switching segment and a wireless medium
 segment, performance and quality need to be coordinated across both
 of these segments.  So QoS performance must be enforced system-wide.
 This objective highlights QoS over the entire WLAN system, which
 includes the switching segment and the wireless medium segment.
 Given the fundamental differences between the two, it is likely that
 there are alternate QoS mechanisms between WTPs and wireless service
 subscribers and between WTPs and WLAN controllers.  For instance, the
 former will be based on IEEE 802.11e, whereas the latter will be an
 alternative.  So resources need to be adjusted in a coordinated
 fashion over both segments.  The CAPWAP protocol should ensure that
 these adjustments are appropriately exchanged between WLAN
 controllers and WTPs.
 In addition to IEEE 802.11e, there are a number of other IEEE 802.11
 task groups that may affect network resources.  These include IEEE
 802.11 TGk, TGu, and TGv, which are currently in progress.  CAPWAP
 should therefore not be restricted to IEEE 802.11e-based mapping.
 Protocol Requirement:
 The CAPWAP protocol MUST map the IEEE 802.11e QoS priorities to
 equivalent QoS priorities across the switching and wireless medium
 segments.

Govindan, et al. Informational [Page 11] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 A protocol that addresses QoS aspects of WLAN systems will deliver
 high performance thereby being beneficial for subscribers and for
 resource utilization efficiency.  Since CAPWAP deals with WTPs
 directly and with the wireless medium indirectly, both of these must
 be considered for performance.
 For the wireless medium segment, QoS aspects in the protocol enable
 high-quality communications within the domain of a WLAN controller.
 Since each domain generally covers an enterprise or a group of
 service providers, such protocol performance has wide-ranging
 effects.
 Within the switching segment of CAPWAP, a QoS-enabled protocol
 minimizes the adverse effects of dynamic traffic characteristics so
 as to ensure system-wide performance.
 Relation to Problem Statement:
 QoS control is critical to large WLANs and relates to a number of
 aspects.  In particular, this objective can help address the problem
 of managing dynamic conditions of the wireless medium.
 Furthermore, traffic characteristics in large-scale WLANs are
 constantly varying.  So network utilization becomes inefficient, and
 user experience is unpredictable.
 The interaction and coordination between the two aspects of system-
 wide QoS are therefore critical for performance.

5.1.8. CAPWAP Protocol Security

 Classification: Security
 Description:
 This objective addresses the security of the CAPWAP protocol.
 The CAPWAP protocol MUST first provide for the participating entities
 -- the WLAN controller and WTPs -- to be explicitly mutually
 authenticated.  This is to ensure that rogue elements do not gain
 access to the WLAN system.  Rogue WTPs should not be allowed to
 breach legitimate WLANs, and at the same time rogue WLAN controllers
 should not be allowed to gain control of legitimate WTPs.  For
 example, WTPs may need to regularly renew their authentication state
 with the WLAN controller and similarly for WLAN controllers.

Govindan, et al. Informational [Page 12] RFC 4564 CAPWAP Objectives July 2006

 If authentication is performed via an authenticated key exchange,
 future knowledge of derived keys is not sufficient for
 authentication.
 Any session keys used between the WLAN controller and WTPs MUST be
 mutually derived using entropy contributed by both parties.  This
 ensures that no one party has control over the resulting session
 keys.
 Once WTPs and the WLAN controller have been mutually authenticated,
 information exchanges between them must be secured against various
 security threats.  So the CAPWAP protocol MUST provide integrity
 protection and replay protection.  The protocol SHOULD provide
 confidentiality through encryption.  This should cover illegitimate
 modifications to protocol exchanges, eavesdropping, and Denial of
 Service (DoS) attacks, among other potential compromises.  So the
 protocol must provide confidentiality, integrity, and authenticity
 for those exchanges.
 As a result of realizing this objective, it should not be possible
 for individual WTP breaches to affect the security of the WLAN as a
 whole.  So WTP misuse will be protected against.
 Additionally, the key establishment protocol for authentication and
 securing CAPWAP exchanges must be designed to minimize the
 possibility of future compromises after the keys are established.
 CAPWAP MUST NOT prevent the use of asymmetric authentication.  The
 security considerations of such asymmetric authentication are
 described in the Security Considerations section.
 If the CAPWAP protocol meets the criteria to require automated key
 management per BCP 107 [RFC4107], then mutual authentication MUST be
 accomplished via an authenticated key exchange.
 Protocol Requirement:
 The CAPWAP protocol MUST support mutual authentication of WTPs and
 the centralized controller.  It also MUST ensure that information
 exchanges are integrity protected and SHOULD ensure confidentiality
 through encryption.

Govindan, et al. Informational [Page 13] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 WLANs are increasingly deployed in critical aspects of enterprise and
 consumer networks.  In these contexts, protocol security is crucial
 to ensure the privacy and integrity expected from network
 administrators and end-users.  So securing the CAPWAP protocol has
 direct benefits in addressing these concerns.
 In many cases, the network path between a WTP and WLAN controller
 contains untrusted links.  Such links could be leveraged by rogue
 WTPs to gain access to the WLAN system.  They could also be used by
 rogue WLAN controllers to gain control of legitimate WTPs and their
 associated terminals to either redirect or compromise terminal
 traffic.  These security concerns can be mitigated with this
 objective.
 Relation to Problem Statement:
 Security problems in large-scale WLANs are detailed in the Problem
 Statement.  These include complications arising from rogue WTPs and
 compromised interfaces between WTPs and the WLAN controller.  The
 requirement for protocol security addresses these problems and
 highlights the importance of protecting against them.

5.1.9. System-wide Security

 Classification: Security
 Description:
 The emphasis of this objective is on the security threats external to
 the centralized CAPWAP segment of a WLAN system.  The focus is
 therefore on rogue wireless clients and other illegitimate wireless
 interferences.  There are a number of specific external threats that
 need to be addressed within the CAPWAP framework.
 i.  PMK Sharing
 One aspect of this objective relates to recent discussions on
 Pairwise Master Key (PMK) sharing in the CAPWAP framework.  This
 objective highlights the need to prevent exploitation of this
 ambiguity by rogue wireless clients.  It is to ensure that any
 ambiguities arising from the CAPWAP framework are not cause for
 security breaches.

Govindan, et al. Informational [Page 14] RFC 4564 CAPWAP Objectives July 2006

 Protocol Requirement:
 The design of the CAPWAP protocol MUST NOT allow for any compromises
 to the WLAN system by external entities.
 Motivation and Protocol Benefits:
 The external threats to the centralized WLAN architecture become
 increasingly crucial given the low cost of wireless clients.  Since
 it is relatively inexpensive for rogue individuals to mount attacks,
 it is important that WLAN systems are protected against them.
 Adequate mechanisms to thwart such external threats will be of
 tremendous benefit to the WLAN systems controlled and managed with
 the CAPWAP protocol.
 Relation to Problem Statement:
 This objective is based on the security needs highlighted in the
 Problem Statement.  Specifically, the Problem Statement discusses the
 effects of the shared wireless medium.  This represents the external
 aspects of the CAPWAP framework from which certain threats can arise.
 The system-wide security objective addresses such threats in relation
 to the Problem Statement.

5.1.10. IEEE 802.11i Considerations

 Classification: Operations
 Description:
 The CAPWAP protocol must support authentication in the centralized
 WLAN architecture in which the authenticator and encryption points
 can be located on distinct entities, i.e., WLAN controller or WTP.
 The Architecture Taxonomy illustrates a number of variants, in both
 local-MAC and split-MAC designs, in which the authenticator is
 located at the WLAN controller and the encryption points are at the
 WTPs.  The CAPWAP protocol must be applicable to these variants and
 allow authentication mechanisms and their constituent processes to be
 operable in these cases.
 An important issue to consider in this case is the exchange of key
 information when authenticator and encryption points are located on
 distinct entities.  For example, consider the case where IEEE 802.11i
 is used in a WLAN in which the WLAN controller realizes the
 authenticator, some WTPs realize encryption (possibly local-MAC
 WTPs), and other WTPs rely on the WLAN controller for encryption
 (possibly split-MAC WTPs).

Govindan, et al. Informational [Page 15] RFC 4564 CAPWAP Objectives July 2006

 Here, CAPWAP will first need to identify the location of the
 authenticator and encryption points between each WLAN controller-WTP
 pair.  This will likely be part of the initial WTP configuration.
 Subsequently, the WTPs that realize encryption will need CAPWAP to
 exchange key information with the authenticator at the WLAN
 controller.  For the WTPs that do not realize encryption, CAPWAP
 needs to adapt its control to bypass the key exchange phase.
 Clearly, the centralized WLAN architecture presents a different
 platform for authentication mechanisms compared to legacy WLANs in
 which a WTP realized both authenticator and encryption roles.  So
 this objective highlights the need for CAPWAP to support
 authentication and key management in the centralized WLAN
 architecture.
 Protocol Requirement:
 The CAPWAP protocol MUST determine the exact structure of the
 centralized WLAN architecture in which authentication needs to be
 supported, i.e., the location of major authentication components.
 This may be achieved during WTP initialization where major
 capabilities are distinguished.
 The protocol MUST allow for the exchange of key information when
 authenticator and encryption roles are located in distinct entities.
 Motivation and Protocol Benefits:
 The immediate focus of CAPWAP is on supporting IEEE 802.11-based
 WLANs.  As such, it is necessary for the protocol to recognize the
 major distinction in WLAN design with respect to IEEE 802.11i
 authenticator and encryption points.  This represents a significant
 variation that has been highlighted in the Architecture Taxonomy.
 The CAPWAP protocol benefits by accommodating such a major
 consideration from IEEE 802.11i.
 These requirements will be common for all authentication mechanisms
 over the centralized WLAN architecture.  So they are applicable to
 IEEE 802.11i, Universal Access Method (UAM), and other mechanisms.
 Relation to Problem Statement:
 The Problem Statement highlights the availability of different WTP
 designs and the need to ensure interoperability among them.  In this
 regard, operational changes occurring due to the separation of the
 IEEE 802.11i authenticator and encryption points need to be
 accommodated within the CAPWAP protocol.

Govindan, et al. Informational [Page 16] RFC 4564 CAPWAP Objectives July 2006

5.1.11. Interoperability Objective

 Classification: Architecture
 Description:
 Two major designs of the centralized WLAN architecture are local-MAC
 and split-MAC.  With the focusing of standardization efforts on these
 two designs, it is crucial to ensure mutual interoperation among
 them.
 This objective for the CAPWAP protocol is to ensure that WTPs of both
 local-MAC and split-MAC architecture designs are capable of
 interoperation within a single WLAN.  Consequently, a single WLAN
 controller will be capable of controlling both types of WTPs using a
 single CAPWAP protocol.  Integral support for these designs comprises
 a number of protocol aspects.
 i.  Capability negotiations between WLAN controller and WTPs
 WTP designs differ in the degree of IEEE 802.11 MAC functionalities
 that each type of WTP realizes.  The major distinctions, split-MAC
 and local-MAC, differ in the processing of IEEE 802.11 MAC frames.
 In this regard, the CAPWAP protocol should include functionality that
 allows for negotiations of significant capabilities between WTPs and
 the WLAN controller.
 As a first step, such negotiations could cover the type of WTP,
 split-MAC or local-MAC, as this provides substantial information on
 their respective capabilities.
 ii.  Establishment of alternative interfaces
 The capability differences among different WTPs essentially equate to
 alternative interfaces with a WLAN controller.  So the CAPWAP
 protocol should be capable of adapting its operations to the major
 different interfaces.  In a first case, this would include
 accommodating capability differences between local-MAC and split-MAC
 WTPs.
 The definition of these interfaces in terms of finer granularity of
 functionalities will be based on AP functionality documents produced
 by the IEEE 802.11 AP Functionality (APF) Ad-Hoc Committee.
 Protocol Requirement:
 The CAPWAP protocol MUST include sufficient capabilities negotiations
 to distinguish between major types of WTPs.

Govindan, et al. Informational [Page 17] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 The benefits of realizing this architecture objective are both
 technical and practical.  First, there are substantial overlaps in
 the control operations of local-MAC and split-MAC architecture
 designs.  The Architecture Taxonomy tabulates major common features
 of the two designs.  As a result, it is technically practical to
 devise a single protocol that manages both types of devices.
 Next, the ability to operate a CAPWAP protocol for both types of
 architectural designs enhances its practical prospects as it will
 have wider appeal.
 Furthermore, the additional complexity resulting from such
 alternative interfaces is marginal.  Consequently, the benefits of
 this objective will far outweigh any cost of realizing it.
 Relation to Problem Statement:
 The objective for supporting both local-MAC and split-MAC WTPs is
 fundamental to addressing the Problem Statement.  It forms the basis
 for those problems to be uniformly addressed across the major WLAN
 architectures.  This is the ultimate aim of standardization efforts.
 The realization of this objective will ensure the development of a
 comprehensive set of mechanisms that address the challenges of
 large-scale WLAN deployments.

5.1.12. Protocol Specifications

 Classification: General
 Description:
 WLAN equipment vendors require sufficient details from protocol
 specifications so that implementing them will allow for compatibility
 with other equipment that runs the same protocol.  In this light, it
 is important for the CAPWAP protocol specifications to be reasonably
 complete for realization.
 Protocol Requirement:
 Any WTP or WLAN controller vendor or any person MUST be able to
 implement the CAPWAP protocol from the specification itself and by
 that it is required that all such implementations do interoperate.

Govindan, et al. Informational [Page 18] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 It is beneficial for WLAN equipment vendors to refer to a single set
 of specifications while implementing the CAPWAP protocol.  This helps
 to ease and quicken the development process.
 Relation to Problem Statement:
 This requirement is based on WG discussions that have been determined
 to be important for CAPWAP.

5.1.13. Vendor Independence

 Classification: General
 Description:
 Rapid developments in WLAN technologies result in equipment vendors
 constantly modifying their devices.  In many cases, developments are
 independently made for WLAN controllers and WTPs.  The CAPWAP
 protocol should not affect the independence of device modifications.
 Protocol Requirement:
 A WTP vendor SHOULD be able to make modifications to hardware without
 any WLAN controller vendor involvement.
 Motivation and Protocol Benefits:
 Independence in the type of hardware for WLAN equipment ensures that
 new developments do not hamper protocol operation.
 Relation to Problem Statement:
 This requirement is based on WG discussions that have been determined
 to be important for CAPWAP.

5.1.14. Vendor Flexibility

 Classification: General
 Description:
 The CAPWAP protocol must not be specified for a particular type of
 wireless MAC design.  It should be compatible with both local-MAC and
 split-MAC WTPs.

Govindan, et al. Informational [Page 19] RFC 4564 CAPWAP Objectives July 2006

 Protocol Requirement:
 The CAPWAP protocol MUST NOT limit WTP vendors in their choice of
 local-MAC or split-MAC WTPs.  It MUST be compatible with both types
 of WTPs.
 Motivation and Protocol Benefits:
 This requirement is to ensure that WTP vendors have sufficient
 flexibility in selecting the type of wireless MAC design that they
 consider best for deployments.
 Relation to Problem Statement:
 This requirement is based on WG discussions that have been determined
 to be important for CAPWAP.

5.1.15. NAT Traversal

 Classification: General
 Description:
 WLAN deployments may involve WTPs and the WLAN controller
 communicating across Network Address Translators (NATs).  The CAPWAP
 protocol must be capable of operating across topologies that contain
 known NAT configurations.  It requires appropriate discovery and
 identification mechanisms for NAT traversal.
 Protocol Requirement:
 The CAPWAP protocol MUST NOT prevent the operation of established
 methods of NAT traversal.
 Motivation and Protocol Benefits:
 The widespread adoption of WLANs raises the possibility for WLAN
 topologies containing NATs.  It is important for the CAPWAP protocol
 to be applicable within such topologies.  This requirement aims to
 make the CAPWAP protocol relevant for NAT traversal.
 Relation to Problem Statement:
 This requirement is based on WG discussions that have been determined
 to be important for CAPWAP.

Govindan, et al. Informational [Page 20] RFC 4564 CAPWAP Objectives July 2006

5.2. Desirable Objectives

 These objectives have been determined to be desirable for a CAPWAP
 protocol but not mandatory.  Realizing these objectives may help
 improve control of WLANs but need not necessarily be required for all
 networks or scenarios.

5.2.1. Multiple Authentication Mechanisms

 Classification: Architecture
 Description:
 Shared WLAN infrastructure raises the issue of multiple
 authentication mechanisms.  This is because each logical group is
 likely to be associated with different service providers or WLAN
 domains.  As a result, the authentication needs within them will be
 different.  Although CAPWAP is required to support IEEE 802.11i, it
 is also necessary for it to support other authentication mechanisms.
 For example, one logical group may use IEEE 802.11i, whereas another
 may use web authentication.  CAPWAP must be able to operate in such
 shared WLANs.
 Protocol Requirement:
 The CAPWAP protocol MUST support different authentication mechanisms
 in addition to IEEE 802.11i.
 Motivation and Protocol Benefits:
 The benefit of supporting various authentication mechanisms is that
 the protocol then becomes flexible for use in various deployments.
 The protocol will therefore not mandate the use of any particular
 mechanisms that may not be appropriate for a particular deployment.
 Relation to Problem Statement:
 This objective relates to the problem of management complexity.
 Shared WLAN deployments simplify management of large networks.

5.2.2. Support for Future Wireless Technologies

 Classification: Architecture
 Description:
 The rapid pace of technology developments means that new advances
 need to be catered to in current analyses.  Among these is the

Govindan, et al. Informational [Page 21] RFC 4564 CAPWAP Objectives July 2006

 support for new wireless technologies within the CAPWAP protocol,
 such as IEEE 802.16.  The protocol should therefore not rely on
 specifics of IEEE 802.11 technology.
 In all cases where the CAPWAP protocol messages contain specific
 layer 2 information elements, the definition of the protocol needs to
 provide for extensibility so that these elements can be defined for
 specific layer 2 wireless protocols.  This may entail assigning a
 layer 2 wireless protocol type and version field to the message PDU.
 Examples of other wireless protocols that might be supported include
 but are not limited to 802.16e, 802.15.x, etc.
 Protocol Requirement:
 CAPWAP protocol messages MUST be designed to be extensible for
 specific layer 2 wireless technologies.  It should not be limited to
 the transport of elements relating to IEEE 802.11.
 Motivation and Protocol Benefits:
 There are many benefits to an extensible protocol.  It allows for
 application in different networks and provides greater scope.
 Furthermore, service providers require WLAN solutions that will be
 able to meet current and future market requirements.
 Relation to Problem Statement:
 The Problem Statement describes some of the advances taking place in
 other standards bodies like the IEEE.  It is important for the CAPWAP
 protocol to reflect the advances and provide a framework in which
 they can be supported.

5.2.3. Support for New IEEE Requirements

 Classification: Architecture
 Description:
 The IEEE 802.11 APF Ad-Hoc Committee has reviewed IEEE 802.11
 functionality and has made more thorough definitions for the new
 requirements.  The CAPWAP protocol must be able to incorporate these
 definitions with minimal change.  Furthermore, a number of extensions
 for IEEE 802.11 are currently being standardized.  The CAPWAP
 protocol must also be able to incorporate these new extensions with
 minimal change.

Govindan, et al. Informational [Page 22] RFC 4564 CAPWAP Objectives July 2006

 Protocol Requirement:
 The CAPWAP protocol MUST be openly designed to support new IEEE
 802.11 definitions and extensions.
 Motivation and Protocol Benefits:
 There are a number of advances being made within the IEEE regarding
 the functionality of IEEE 802.11 technology.  Since this represents
 one of the major wireless technologies in use today, it will be
 beneficial for CAPWAP to incorporate the relevant new extensions.
 Relation to Problem Statement:
 The Problem Statement presents an overview of the task of the IEEE
 802.11 working group.  This group is focused on defining the
 functional architecture of WTPs and new extensions for it.  It is
 necessary for the CAPWAP protocol to reflect these definitions and
 extensions.

5.2.4. Interconnection Objective

 Classification: Architecture
 Description:
 Large-scale WLAN deployments are likely to use a variety of
 interconnection technologies between different devices of the
 network.  It should therefore be possible for the CAPWAP protocol to
 operate over various interconnection technologies.
 As a result of realizing this objective, the protocol will be capable
 of operation over both IPv4 and IPv6.  It will also be designed such
 that it can operate within tightly administered networks, such as
 enterprise networks, or on open, public access networks.  For
 example, VLAN tunnels can be used across different types of networks
 over which CAPWAP will operate.
 Protocol Requirement:
 The CAPWAP protocol MUST NOT be constrained to specific underlying
 transport mechanisms.

Govindan, et al. Informational [Page 23] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 The main aim of the CAPWAP protocol is to achieve interoperability
 among various WTPs and WLAN controllers.  As such, the motivation for
 this requirement is for the protocol to be operable independent of
 underlying interconnection technologies.
 Relation to Problem Statement:
 The Problem Statement discusses the complexity of configuring large
 WLANs.  The selection of available interconnection technologies for
 large-scale deployments further intensifies this complexity.  This
 requirement avoids part of the complexity by advocating independence
 of the operational aspects of the protocol from underlying transport.

5.2.5. Access Control

 Classification: Operations
 Description:
 This objective focuses on the informational needs of WLAN access
 control and specifically the role of the CAPWAP protocol in
 transporting this information between WTPs and their WLAN controller.
 The following are some specific information aspects that need to be
 transported by the CAPWAP protocol:
 i.  IEEE 802.11 association and authentication
 The association of wireless clients is distinct for initial and
 roaming cases.  As a result, access control mechanisms require
 specific contextual information regarding each case.  Additionally,
 load balancing, QoS, security, and congestion information in both
 wireless medium segments and switching segments need to be
 considered.
 ii.  WTP Access Control
 In addition to controlling access for wireless clients, it is also
 necessary to control admission of new WTPs.  Given the threat of
 rogue WTPs, it is important for CAPWAP to relay appropriate
 authentication information between new WTPs and the WLAN controller.
 Protocol Requirement:
 The CAPWAP protocol MUST be capable of exchanging information
 required for access control of WTPs and wireless terminals.

Govindan, et al. Informational [Page 24] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 Due to the scale of deployments in which CAPWAP will be employed,
 comprehensive access control is crucial.  The effectiveness of access
 control in turn is affected by the information on which such control
 is based.  As a result, this objective has critical relevance to a
 CAPWAP protocol.
 Relation to Problem Statement:
 This objective addresses the issue of access control in large WLANs.
 Broadly, it relates the problem of managing the complexity scale of
 such networks.  With collective information of both switching and
 wireless medium segments, realizing this objective will help control
 and manage complexity.

5.3. Non-Objectives

 The following objectives have been prioritized as non-objectives
 during the course of working group consultations.  They have been
 prioritized so in the context of CAPWAP and its considerations.  They
 may, however, be applicable in alternative contexts.

5.3.1. Support for Non-CAPWAP WTPs

 Classification: Architecture
 Description:
 The CAPWAP protocol should provide an engine-mechanism to spring WTP
 auto-configuration and/or software version updates and should support
 integration with existing network management system.  WLAN controller
 as a management agent is optional.
 If entities other than WLAN controllers manage some aspects of WTPs,
 such as software downloads, the CAPWAP protocol may be used for WTPs
 to notify WLAN controllers of any changes made by the other entities.
 Protocol Requirement:
 The CAPWAP protocol SHOULD be capable of recognizing legacy WTPs and
 existing network management systems.

Govindan, et al. Informational [Page 25] RFC 4564 CAPWAP Objectives July 2006

 Motivation and Protocol Benefits:
 It is expected that in many cases, the centralized WLAN architecture
 will be deployed incrementally with legacy systems.  In this regard,
 it is necessary for the protocol to be used in scenarios with mixed
 WLAN devices.
 Relation to Problem Statement:
 The Problem Statement highlights management complexity as a major
 issue with large WLANs.  One part of this complexity can be related
 to the incremental deployment of centralized WLAN devices for which
 this objective is applicable.

5.3.2. Technical Specifications

 Classification: General
 Description:
 The CAPWAP protocol must not require AC and WTP vendors to share
 technical specifications to establish compatibility.  The protocol
 specifications alone must be sufficient for compatibility.
 Protocol Requirement:
 WTP vendors SHOULD NOT have to share technical specifications for
 hardware and software to AC vendors in order for interoperability to
 be achieved.
 Motivation and Protocol Benefits:
 It is beneficial for WLAN equipment vendors to refer to a single set
 of specifications while implementing the CAPWAP protocol.  This helps
 to ease and quicken the development process.
 Relation to Problem Statement:
 This requirement is based on WG discussions that have been determined
 to be important for CAPWAP.
 This objective has been prioritized as a non-objective as it is a
 duplicate of the Protocol Specifications objective (Section 5.1.12).

Govindan, et al. Informational [Page 26] RFC 4564 CAPWAP Objectives July 2006

5.4. Operator Requirements

 The following objectives have been provided by network service
 operators.  They represent the requirements from those ultimately
 deploying the CAPWAP protocol in their WLANs.

5.4.1. AP Fast Handoff

 Classification: Operations
 Description:
 Network service operators consider handoffs crucial because of the
 mobile nature of their customers.  In this regard, the CAPWAP
 protocol should not adversely affect AP fast-handoff procedures.  The
 protocol may support optimizations for fast handoff procedures so as
 to allow better support for real-time services during handoffs.
 Protocol Requirement:
 CAPWAP protocol operations MUST NOT impede or obstruct the efficacy
 of AP fast-handoff procedures.

6. Summary and Conclusion

 The objectives presented in this document address three main aspects
 of the CAPWAP protocol, namely:
 i.  Architecture
 ii.  Operations
 iii.  Security
 These requirements are aimed at focusing standardization efforts on a
 simple, interoperable protocol for managing large-scale WLANs.  The
 architecture requirements specify the structural features of the
 protocol such as those relating to WTP types (local-MAC and split-
 MAC) and WTP structures (logical groups).  The operations
 requirements address the functional aspects dealing with WTP
 configuration and management.  Finally, the security requirements
 cover authentication and integrity aspects of protocol exchanges.
 The objectives have additionally been prioritized to reflect their
 immediate significance to the development and evaluation of an
 interoperable CAPWAP protocol.  The priorities are Mandatory and
 Accepted, Desirable, and Non-Objectives.  They reflect working group
 consensus on the effectiveness of the requirements in the context of
 protocol design.

Govindan, et al. Informational [Page 27] RFC 4564 CAPWAP Objectives July 2006

 Additionally, this document includes requirements from network
 service operators that have been derived based on their experience in
 operating large-scale WLANs.
 The resulting requirements from this document will be used in
 conjunction with the CAPWAP Problem Statement [RFC3990] and CAPWAP
 Architecture Taxonomy [RFC4118] to develop and evaluate an
 interoperable protocol for the control and provisioning of WTPs in
 large-scale WLANs.

7. Security Considerations

 The CAPWAP framework highlights support for both local-MAC and
 split-MAC WTPs.  In deployments where both types of WTPs are used, it
 is crucial to ensure that each be secured in consideration of its
 capabilities.  The Architecture Taxonomy illustrates how different
 WTPs incorporate varying levels of functionalities.  Development of
 the CAPWAP protocol should ensure that the deployment of both local-
 MAC and split-MAC WTPs within a single WLAN do not present loopholes
 for security compromises.
 In shared WLAN deployments made of a number of logical groups,
 traffic from each group needs to be mutually separated.  So in
 addition to protocol-related exchanges, data traffic from wireless
 terminals should also be segregated with respect to the logical
 groups to which they belong.  It should not be possible for data or
 control traffic from one logical group to stray to or influence
 another logical group.
 The use of IEEE 802.11i over the centralized WLAN architecture allows
 for implementations in which the PMK is shared across WTPs.  This
 raises the ambiguity between legitimate sharing and illegitimate
 copies.  Wireless terminals may unknowingly fall prey to or exploit
 this ambiguity.  The resolution of this issue is currently being
 evaluated by the IEEE 802 and IETF liaisons.
 The low cost of launching attacks on WLANs makes the CAPWAP protocol
 a target.  A first step in securing against any form of attacks is to
 continuously monitor the WLAN for conditions of potential threats
 from rogue WTPs or wireless terminals.  For example, profiles for DoS
 and replay attacks need to be considered for the CAPWAP protocol to
 effectively monitor security conditions.
 The open environment of many WLAN deployments makes physical security
 breaches highly probable.  Compromises resulting from theft and
 physical damage must be considered during protocol development.  For
 instance, it should not be possible for a single compromised WTP to
 affect the WLAN as a whole.

Govindan, et al. Informational [Page 28] RFC 4564 CAPWAP Objectives July 2006

 Considering asymmetric, non-mutual authentication between WTPs and
 the WLAN controller, there is a risk of a rogue participant
 exploiting such an arrangement.  It is preferable to avoid non-mutual
 authentication.  In some cases, the legitimacy of the protocol
 exchange participants may be verified externally, for example, by
 means of physical containment within a close environment.  Asymmetric
 authentication may be appropriate here without risk of security
 compromises.

8. Acknowledgements

 The authors would like to thank the working group chairs, Dorothy
 Gellert and Mahalingam Mani, for their support and patience with this
 document.  We would also like to thank participants of the working
 group who have helped shape the objectives.  In particular, the
 authors thank James Kempf, Pat Calhoun, Inderpreet Singh, Dan
 Harkins, T. Sridhar, Charles Clancy, and Emek Sadot for their
 invaluable inputs.  We also extend our gratitude to the IEEE 802.11
 Ad-Hoc Committee for its evaluation of the document.  The authors
 also acknowledge the contributions from Meimei Dang, Satoshi Iino,
 Mikihito Sugiura, and Dong Wang.

9. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3990]  O'Hara, B., Calhoun, P., and J. Kempf, "Configuration and
            Provisioning for Wireless Access Points (CAPWAP) Problem
            Statement", RFC 3990, February 2005.
 [RFC4118]  Yang, L., Zerfos, P., and E. Sadot, "Architecture Taxonomy
            for Control and Provisioning of Wireless Access Points
            (CAPWAP)", RFC 4118, June 2005.

10. Informative References

 [802.11]   IEEE Standard 802.11, "Wireless LAN Medium Access Control
            (MAC) and Physical Layer (PHY) Specifications", June 2003.
 [802.11i]  IEEE Standard 802.11i, "Medium Access Control (MAC)
            Security Enhancements", July 2004.
 [802.11e]  IEEE Standard 802.11e, "Medium Access Control (MAC)
            Quality of Service Enhancements", November 2005.
 [RFC4107]  Bellovin, S. and R. Housley, "Guidelines for Cryptographic
            Key Management", BCP 107, RFC 4107, June 2005.

Govindan, et al. Informational [Page 29] RFC 4564 CAPWAP Objectives July 2006

Authors' Addresses

 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
 Zhonghui Yao
 Huawei Longgang Production Base
 Shenzhen  518 129
 P. R. China
 Phone: +86 755 2878 0808
 EMail: yaoth@huawei.com
 Wenhui Zhou
 China Mobile
 53A, Xibianmen Ave, Xuanwu District
 Beijing  100 053
 P. R. China
 Phone: +86 10 6600 6688 ext.3061
 EMail: zhouwenhui@chinamobile.com
 L. Lily Yang
 Intel Corp.
 JF3-206, 2111 NE 25th Ave.
 Hilsboro, OR  97124
 USA
 Phone: +1 503 264 8813
 EMail: lily.l.yang@intel.com

Govindan, et al. Informational [Page 30] RFC 4564 CAPWAP Objectives July 2006

 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

Govindan, et al. Informational [Page 31] RFC 4564 CAPWAP Objectives July 2006

Full Copyright Statement

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 contained in BCP 78, and except as set forth therein, the authors
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Govindan, et al. Informational [Page 32]

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