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Versions: 00 01 02 rfc3990                                              
CAPWAP Working Group                                          P. Calhoun
Internet-Draft                                                 B. O'Hara
Expires: November 8, 2004                                      Airespace
                                                                J. Kempf
                                                         Docomo Labs USA
                                                            May 10, 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 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

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

   This Internet-Draft will expire on November 8, 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
   4.   References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6
        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.  This
   is due to a number of factors, including the disparate architectural
   choices made by the various manufacturers.  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

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3.  Security Considerations

   The devices used in WLANs control the access to networks and provide
   for the delivery of packets between hosts using the WLAN and other
   hosts on the WLAN or elsewhere on the internet.  The functions for
   control and provisioning of wireless access points, therefore require
   protection to prevent misuse of the devices.

   Requirements for central management, monitoring, and control of
   wireless access points that should be addressed include
   confidentiality, integrity, and authenticity.  Once an AP and AC have
   been authenticated to each other, it may not be sufficient that a
   single level of authorization allows monitoring, as well as control
   and provisioning.  The requirement for more than a single level of
   authorization should be determined.  Physical security should also be
   addressed, for those devices that contain security parameters that
   are sensitive and might compromise the security of the system, if
   those parameters were to fall into the hands of an attacker.

4  References

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

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   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
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   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
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   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.

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   The limited permissions granted above are perpetual and will not be
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   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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