draft-ietf-capwap-problem-statement-02.txt   rfc3990.txt 
CAPWAP Working Group B. O'Hara Network Working Group B. O'Hara
Internet-Draft P. Calhoun Request for Comments: 3990 P. Calhoun
Expires: February 18, 2005 Airespace Category: Informational Airespace
J. Kempf J. Kempf
Docomo Labs USA Docomo Labs USA
August 20, 2004 February 2005
CAPWAP Problem Statement
draft-ietf-capwap-problem-statement-02
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
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Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at Configuration and Provisioning for Wireless Access Points (CAPWAP)
http://www.ietf.org/ietf/1id-abstracts.txt. Problem Statement
The list of Internet-Draft Shadow Directories can be accessed at Status of This Memo
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 18, 2005. 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 Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2005).
Abstract Abstract
This document describes the Configuration and Provisioning for This document describes the Configuration and Provisioning for
Wireless Access Points (CAPWAP) problem statement. Wireless Access Points (CAPWAP) problem statement.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 8
1. Introduction 1. Introduction
With the approval of the 802.11 standard by the IEEE in 1997, With the approval of the 802.11 standard by the IEEE in 1997,
wireless LANs (WLANs) began a slow entry into enterprise networks. wireless LANs (WLANs) began a slow entry into enterprise networks.
The limited data rates of the original 802.11 standard, only 1- and The limited data rates of the original 802.11 standard, only 1 and 2
2-Mbps, limited widespread adoption of the technology. 802.11 found Mbps, limited the widespread adoption of the technology. 802.11
wide deployment in vertical applications, such as inventory found wide deployment in vertical applications, such as inventory
management, point of sale, and transportation management. Pioneering management, point of sale, and transportation management. Pioneering
enterprises began to deploy 802.11, mostly for experimentation. enterprises began to deploy 802.11, mostly for experimentation.
In 1999, the IEEE approved the 802.11a and 802.11b amendments to the 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, base standard, increasing the available data rate to 54 and 11 Mbps,
respectively, and expanding to a new radio band. This removed one of respectively, and expanding to a new radio band. This removed one of
the significant factors holding back adoption of 802.11 in large, the significant factors holding back adoption of 802.11 in large
enterprise networks. These large deployments were bound by the enterprise networks. These large deployments were bound by the
definition and functionality of an 802.11 Access Point (AP), as definition and functionality of an 802.11 Access Point (AP), as
described in the 802.11 standard. The techniques required extensive described in the 802.11 standard. The techniques required extensive
use of layer 2 bridging and widespread VLANs to ensure the proper use of layer 2 bridging and widespread VLANs to ensure the proper
operation of higher layer protocols. Deployments of 802.11 WLANs as operation of higher layer protocols. Deployments of 802.11 WLANs as
large as several thousand APs have been described. large as several thousand APs have been described.
Large deployments of 802.11 WLANs have introduced several problems Large deployments of 802.11 WLANs have introduced several problems
that require solutions. The limitations on the scalability of that require solutions. The limitations on the scalability of
bridging should come as no suprise to the networking community, since bridging should come as no surprise to the networking community, as
similar limitations arose in the early 1980's for wired network similar limitations arose in the early 1980s for wired network
bridging during the expansion and interconnection of wired local area bridging during the expansion and interconnection of wired local area
networks. This document will describe the problems introduced by the networks. This document will describe the problems introduced by the
large scale deployment of 802.11 WLANs in enterprise networks. large-scale deployment of 802.11 WLANs in enterprise networks.
2. Problem Statement 2. Problem Statement
The first problem introduced by large WLAN deployments is that each Large WLAN deployments introduce several problems. First, each AP is
AP is an IP-addressable device requiring management, monitoring, and an IP-addressable device requiring management, monitoring, and
control. Deployment of a large WLAN will typically double the number control. Deployment of a large WLAN will typically double the number
of network infrastructure devices that require management, over the of network infrastructure devices that require management. This
devices in the network prior to the addition of the WLAN. This
presents a significant additional burden to the network presents a significant additional burden to the network
administration resources and is often a hurdle to adoption of administration resources and is often a hurdle to adoption of
wireless technologies, particularly because the configuration of each wireless technologies, particularly because the configuration of each
access point is nearly identical to the next. This near-sameness of access point is nearly identical to the next. This near-sameness
configuration from one AP to the next often leads to misconfiguration often leads to misconfiguration and improper operation of the WLAN.
and improper operation of the WLAN.
A second problem introduced by large WLAN deployments is distributing Second, distributing and maintaining a consistent configuration
and maintaining a consistent configuration throughout the entire set throughout the entire set of access points in the WLAN is
of access points in the WLAN. Access point configuration consists of problematic. Access point configuration consists of both long-term
both long-term static information, such as addressing and hardware static information (such as addressing and hardware settings) and
settings, and more dynamic provisioning information, such as more dynamic provisioning information (such as individual WLAN
individual WLAN settings and security parameters. Large WLAN settings and security parameters). Large WLAN installations that
installations that need to update dyanmic provisioning information in have to update dynamic provisioning information in all the APs in the
all the APs in the WLAN require a prolonged phase-over time, while WLAN require a prolonged phase-over time. As each AP is updated, the
each AP is updated and the WLAN does not have a single, consistent, WLAN will not have a single, consistent configuration.
configuration.
A third problem introduced by large WLAN deployments is the Third, dealing effectively with the dynamic nature of the WLAN medium
difficulty in dealing effectively with the dynamic nature of the WLAN itself is difficult. Due to the shared nature of the wireless medium
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
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
devices that are not APs at all, parameters controlling the wireless
medium on each AP must be monitored frequently and modified in a medium on each AP must be monitored frequently and modified in a
coordinated fashion to maximize performance for the WLAN to utilize coordinated fashion to maximize WLAN performance. This must be
the wireless medium efficiently. This must be coordinated among all coordinated among all the access points, to minimize the interference
the access points, to minimize the interference of one access point of one access point with its neighbors. Manually monitoring these
with its neighbors. Manually monitoring these metrics and metrics and determining a new, optimum configuration for the
determining a new, optimum configuration for the parameters related parameters related to the wireless medium is a task that takes
to the wireless medium is a task that takes a significant amount of significant time and effort.
time and effort.
A fourth problem introduced by large WLAN deployments is securing Fourth, securing access to the network and preventing installation of
access to the network and preventing installation of unauthorized unauthorized access points is challenging. Physical locations for
access points. Access points are often difficult to physically access points are often difficult to secure since their location must
secure, since their location must often be outside of a locked often be outside of a locked network closet or server room. Theft of
network closet or server room. Theft of an access point, with its an access point, with its embedded secrets, allows a thief to obtain
embedded secrets, allows the thief to obtain access to the resources access to the resources secured by those secrets.
secured by those secrets.
Recently, multiple vendors have begun offering proprietary solutions Recently, to address some, or all, of the above problems, multiple
that combine aspects of network switching, centralized control and vendors have begun offering proprietary solutions that combine
management, and distributed wireless access in a variety of new aspects of network switching, centralized control and management, and
architectures to adress some, or all, of the above mentioned distributed wireless access in a variety of new architectures. Since
problems. Since interoperable solutions allow enterprises and interoperable solutions allow enterprises and service providers a
service providers a broader choice, a standardized, interoperable broader choice, a standardized, interoperable interface between
interface between access points and a centralized controller access points and a centralized controller addressing the problems
addressing the above mentioned problems seems desirable. seems desirable.
The physical portions of this network system, in currently fielded In currently fielded devices, the physical portions of this network
devices, are one or more 802.11 access points (APs) and one or more system are one or more 802.11 access points (APs) and one or more
central control devices, alternatively described as controllers (or central control devices, alternatively described as controllers (or
access controllers, ACs). Ideally, a network designer would be able as access controllers, ACs). Ideally, a network designer would be
to choose one or more vendors for the APs and one or more vendors for able to choose one or more vendors for the APs and one or more
the central control devices in sufficient numbers to design a network vendors for the central control devices in sufficient numbers to
with 802.11 wireless access to meet the designer's requirements. design a network with 802.11 wireless access to meet the designer's
requirements.
Current implementations are proprietary and not interoperable. This Current implementations are proprietary and are not interoperable.
is due to a number of factors, including the disparate architectural This is due to a number of factors, including the disparate
choices made by the various manufacturers. A taxonomy of the architectural choices made by the various manufacturers. A taxonomy
architectures employed in the existing products in the market will of the architectures employed in the existing products in the market
provide the basis of an output document to be provided to the IEEE will provide the basis of an output document to be provided to the
802.11 Working Group. This taxonomy will be utilized by the 802.11 IEEE 802.11 Working Group. This taxonomy will be utilized by the
Working Group as input to their task of defining the functional 802.11 Working Group as input to their task of defining the
architecture of an access point. The functional architecture, functional architecture of an access point. The functional
including description of detailed functional blocks, interfaces, and architecture, including descriptions of detailed functional blocks,
information flow, will be reviewed by CAPWAP to determine if further interfaces, and information flow, will be reviewed by CAPWAP to
work is needed to apply or develop standard protocols providing for determine if further work is necessary to apply or develop standard
multi-vendor interoperable implementations of WLANs built from protocols providing for multi-vendor interoperable implementations of
devices that adhere to the newly appearing hierarchical architecture WLANs built from devices that adhere to the newly appearing
utilizing a functional split between an access point and an access hierarchical architecture using a functional split between an access
controller. point and an access controller.
3. Security Considerations 3. Security Considerations
The devices used in WLANs control the access to networks and provide The devices used in WLANs control network access and provide for the
for the delivery of packets between hosts using the WLAN and other delivery of packets between hosts using the WLAN and other hosts on
hosts on the WLAN or elsewhere on the Internet. The functions for the WLAN or elsewhere on the Internet. Therefore, the functions for
control and provisioning of wireless access points, therefore require control and provisioning of wireless access points, require
protection to prevent misuse of the devices. protection to prevent misuse of the devices.
Requirements for central management, monitoring, and control of Confidentiality, integrity, and authenticity requirements should
wireless access points that should be addressed include address central management, monitoring, and control of wireless
confidentiality, integrity, and authenticity. Once an AP and AC have access points that should be addressed. Once an AP and AC have been
been authenticated to each other, it may not be sufficient that a authenticated to each other, a single level of authorization allowing
single level of authorization allows monitoring, as well as control monitoring, control, and provisioning may not be sufficient. The
and provisioning. The requirement for more than a single level of requirement for more than a single level of authorization should be
authorization should be determined. Physical security should also be determined. Physical security should also be addressed for those
addressed, for those devices that contain security parameters that devices that contain sensitive security parameters that might
are sensitive and might compromise the security of the system, if compromise the security of the system, if those parameters were to
those parameters were to fall into the hands of an attacker. fall into the hands of an attacker.
APs are often installed in locations that are difficult to secure, in To provide comprehensive radio coverage, APs are often installed in
order to provide comprehensive radio coverage. The CAPWAP locations that are difficult to secure. The CAPWAP architecture may
architecture may reduce the consequences of a stolen AP. If reduce the consequences of a stolen AP. If high-value secrets, such
high-value secrets, such as a RADIUS shared secret, are stored in the as a RADIUS shared secret, are stored in the AC, then the physical
AC, then the physical loss of an AP does not compromise these loss of an AP does not compromise these secrets. Further, the AC can
secrets. Further, the AC can easily be located in a physically easily be located in a physically secure location. Of course,
secure location. Of course, concentrating all of the high-value concentrating all the high-value secrets in one place makes the AC an
secrets in one place makes the AC an attractive target, and strict attractive target, and strict physical, procedural, and technical
physical, procedural, and technical controls are needed to protect controls are needed to protect the secrets.
the secrets.
Authors' Addresses Authors' Addresses
Bob O'Hara Bob O'Hara
Airespace Airespace
110 Nortech Parkway 110 Nortech Parkway
San Jose, CA 95134 San Jose, CA 95134
Phone: +1 408-635-2025 Phone: +1 408-635-2025
EMail: bob@airespace.com EMail: bob@airespace.com
skipping to change at page 8, line 5 skipping to change at page 5, line 5
EMail: pcalhoun@airespace.com EMail: pcalhoun@airespace.com
James Kempf James Kempf
Docomo Labs USA Docomo Labs USA
181 Metro Drive, Suite 300 181 Metro Drive, Suite 300
San Jose, CA 95110 San Jose, CA 95110
Phone: +1 408 451 4711 Phone: +1 408 451 4711
EMail: kempf@docomolabs-usa.com EMail: kempf@docomolabs-usa.com
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