CAPWAP Working Group
P. Calhoun Internet-DraftB. O'Hara Internet-Draft P. Calhoun Expires: November 8, 2004February 18, 2005 Airespace J. Kempf Docomo Labs USA May 10,August 20, 2004 CAPWAP Problem Statement draft-ietf-capwap-problem-statement-01draft-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 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://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on November 8, 2004.February 18, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes the Configuration and Provisioning for Wireless Access Points (CAPWAP) problem statement. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . 8 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. 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, configuration. 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 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 controller. 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.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 ReferencesAPs are often installed in locations that are difficult to secure, in order to provide comprehensive radio coverage. The CAPWAP architecture may reduce the consequences of a stolen AP. If high-value secrets, such as a RADIUS shared secret, are stored in the AC, then the physical loss of an AP does not compromise these secrets. Further, the AC can easily be located in a physically secure location. Of course, concentrating all of the high-value secrets in one place makes the AC an attractive target, and strict physical, procedural, and technical controls are needed to protect the secrets. Authors' Addresses Pat R. CalhounBob O'Hara Airespace 110 Nortech Parkway San Jose, CA 95134 Phone: +1 408-635-2000408-635-2025 EMail: email@example.com Bob O'Harabob@airespace.com Pat R. Calhoun Airespace 110 Nortech Parkway San Jose, CA 95134 Phone: +1 408-635-2025408-635-2000 EMail: firstname.lastname@example.org@airespace.com James Kempf Docomo Labs USA 181 Metro Drive, Suite 300 San Jose, CA 95110 Phone: +1 408 451 4711 EMail: email@example.com 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. 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