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Versions: 00 01 02 rfc3990                                              
CAPWAP Working Group                                          P. Calhoun
Internet-Draft                                                 B. O'Hara
Expires: August 2, 2004                                        Airespace
                                                                J. Kempf
                                                         Docomo Labs USA
                                                        February 2, 2004

                        CAPWAP Problem Statement

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on August 2, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.


   This document describes the Configuration and Provisioning for
   Wireless Access Points (CAPWAP) problem statement.

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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. Problem Statement  . . . . . . . . . . . . . . . . . . . . . . . 4
   3. Security Considerations  . . . . . . . . . . . . . . . . . . . . 6
      References . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
      Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
      Intellectual Property and Copyright Statements . . . . . . . . . 8

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1. Introduction

   With the approval of the 802.11 standard by the IEEE in 1997,
   wireless LANs (WLANs) began a slow entry into enterprise networks.
   The limited data rates of the original 802.11 standard, only 1- and
   2-Mbps, limited widespread adoption of the technology.  802.11 found
   wide deployment in vertical applications, such as inventory
   management, point of sale, and transportation management.  Pioneering
   enterprises began to deploy 802.11, mostly for experimentation.

   In 1999, the IEEE approved the 802.11a and 802.11b amendments to the
   base standard, increasing the available data rate to 54- and 11-Mbps,
   respectively, and expanding to a new radio band. This removed one of
   the significant factors holding back adoption of 802.11 in large,
   enterprise networks. These large deployments were bound by the
   definition and functionality of an 802.11 Access Point (AP), as
   described in the 802.11 standard. The techniques required extensive
   use of layer 2 bridging and widespread VLANs to ensure the proper
   operation of higher layer protocols. Deployments of 802.11 WLANs as
   large as several thousand APs have been described.

   Large deployments of 802.11 WLANs have introduced several problems
   that require solutions. The limitations on the scalability of
   bridging should come as no suprise to the networking community, since
   similar limitations arose in the early 1980's for wired network
   bridging during the expansion and interconnection of wired local area
   networks. This document will describe the problems introduced by the
   large scale deployment of 802.11 WLANs in enterprise networks.

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2. Problem Statement

   The first problem introduced by large WLAN deployments is that each
   AP is an IP-addressable device requiring management, monitoring, and
   control.  Deployment of a large WLAN will typically double the number
   of network infrastructure devices that require management, over the
   devices in the network prior to the addition of the WLAN.  This
   presents a significant additional burden to the network
   administration resources and is often a hurdle to adoption of
   wireless technologies, particularly because the configuration of each
   access point is nearly identical to the next.  This near-sameness of
   configuration from one AP to the next often leads to misconfiguration
   and improper operation of the WLAN.

   A second problem introduced by large WLAN deployments is distributing
   and maintaining a consistent configuration throughout the entire set
   of access points in the WLAN.  Access point configuration consists of
   both long-term static information, such as addressing and hardware
   settings, and more dynamic provisioning information, such as
   individual WLAN settings and security parameters.  Large WLAN
   installations that need to update dyanmic provisioning information in
   all the APs in the WLAN require a prolonged phase-over time, while
   each AP is updated and the WLAN does not have a single, consistent,

   A third problem introduced by large WLAN deployments is the
   difficulty in dealing effectively with the dynamic nature of the WLAN
   medium, itself. Due to the shared nature of the wireless medium,
   shared with APs in the same WLAN, with APs in other WLANs, and with
   devices that are not APs at all, parameters controlling the wireless
   medium on each AP must be monitored frequently and modified in a
   coordinated fashion to maximize performance for the WLAN to utilize
   the wireless medium efficiently. This must be coordinated among all
   the access points, to minimize the interference of one access point
   with its neighbors.  Manually monitoring these metrics and
   determining a new, optimum configuration for the parameters related
   to the wireless medium is a task that takes a significant amount of
   time and effort.

   A fourth problem introduced by large WLAN deployments is securing
   access to the network and preventing installation of unauthorized
   access points.  Access points are often difficult to physically
   secure, since their location must often be outside of a locked
   network closet or server room.  Theft of an access point, with its
   embedded secrets, allows the thief to obtain access to the resources
   secured by those secrets.

   Recently, multiple vendors have begun offering proprietary solutions

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   that combine aspects of network switching, centralized control and
   management, and distributed wireless access in a variety of new
   architectures to adress some, or all, of the above mentioned
   problems. Since interoperable solutions allow enterprises and service
   providers a broader choice, a standardized, interoperable interface
   between access points and a centralized controller addressing the
   above mentioned problems seems desirable.

   The physical portions of this network system, in currently fielded
   devices, are one or more 802.11 access points (APs) and one or more
   central control devices, alternatively described as controllers (or
   access controllers, ACs). Ideally, a network designer would be able
   to choose one or more vendors for the APs and one or more vendors for
   the central control devices in sufficient numbers to design a network
   with 802.11 wireless access to meet the designer's requirements.

   Current implementations are proprietary and not interoperable.  A
   taxonomy of the architectures employed in the existing products in
   the market will provide the basis of an output document to be
   provided to the IEEE 802.11 Working Group.  This taxonomy will be
   utilized by the 802.11 Working Group as input to their task of
   defining the functional architecture of an access point.  The
   functional architecture, including description of detailed functional
   blocks, interfaces, and information flow, will be reviewed by CAPWAP
   to determine if further work is needed to apply or develop standard
   protocols providing for multi-vendor interoperable implementations of
   WLANs built from devices that adhere to the newly appearing
   hierarchical architecture utilizing a functional split between an
   access point and an access controller.

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3. Security Considerations

   To the extent of our knowledge, this problem statement does not
   create any security issues to the Internet.

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   [1]  "Mobility Related Terminology", April 2003, <ftp://ftp.isi.edu/

Authors' Addresses

   Pat R. Calhoun
   110 Nortech Parkway
   San Jose, CA  95134

   Phone: +1 408-635-2000
   EMail: pcalhoun@airespace.com

   Bob O'Hara
   110 Nortech Parkway
   San Jose, CA  95134

   Phone: +1 408-635-2025
   EMail: bob@airespace.com

   James Kempf
   Docomo Labs USA
   181 Metro Drive, Suite 300
   San Jose, CA  95110

   Phone: +1 408 451 4711
   EMail: kempf@docomolabs-usa.com

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Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive

Full Copyright Statement

   Copyright (C) The Internet Society (2004). All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an

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   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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