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Note that 19 other groups may also distribute working documents as 20 Internet-Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on February 18, 2005. 35 Copyright Notice 37 Copyright (C) The Internet Society (2004). All Rights Reserved. 39 Abstract 41 This document describes the Configuration and Provisioning for 42 Wireless Access Points (CAPWAP) problem statement. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 47 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 48 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 49 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6 50 Intellectual Property and Copyright Statements . . . . . . . . 8 52 1. Introduction 54 With the approval of the 802.11 standard by the IEEE in 1997, 55 wireless LANs (WLANs) began a slow entry into enterprise networks. 56 The limited data rates of the original 802.11 standard, only 1- and 57 2-Mbps, limited widespread adoption of the technology. 802.11 found 58 wide deployment in vertical applications, such as inventory 59 management, point of sale, and transportation management. Pioneering 60 enterprises began to deploy 802.11, mostly for experimentation. 62 In 1999, the IEEE approved the 802.11a and 802.11b amendments to the 63 base standard, increasing the available data rate to 54- and 11-Mbps, 64 respectively, and expanding to a new radio band. This removed one of 65 the significant factors holding back adoption of 802.11 in large, 66 enterprise networks. These large deployments were bound by the 67 definition and functionality of an 802.11 Access Point (AP), as 68 described in the 802.11 standard. The techniques required extensive 69 use of layer 2 bridging and widespread VLANs to ensure the proper 70 operation of higher layer protocols. Deployments of 802.11 WLANs as 71 large as several thousand APs have been described. 73 Large deployments of 802.11 WLANs have introduced several problems 74 that require solutions. The limitations on the scalability of 75 bridging should come as no suprise to the networking community, since 76 similar limitations arose in the early 1980's for wired network 77 bridging during the expansion and interconnection of wired local area 78 networks. This document will describe the problems introduced by the 79 large scale deployment of 802.11 WLANs in enterprise networks. 81 2. Problem Statement 83 The first problem introduced by large WLAN deployments is that each 84 AP is an IP-addressable device requiring management, monitoring, and 85 control. Deployment of a large WLAN will typically double the number 86 of network infrastructure devices that require management, over the 87 devices in the network prior to the addition of the WLAN. This 88 presents a significant additional burden to the network 89 administration resources and is often a hurdle to adoption of 90 wireless technologies, particularly because the configuration of each 91 access point is nearly identical to the next. This near-sameness of 92 configuration from one AP to the next often leads to misconfiguration 93 and improper operation of the WLAN. 95 A second problem introduced by large WLAN deployments is distributing 96 and maintaining a consistent configuration throughout the entire set 97 of access points in the WLAN. Access point configuration consists of 98 both long-term static information, such as addressing and hardware 99 settings, and more dynamic provisioning information, such as 100 individual WLAN settings and security parameters. Large WLAN 101 installations that need to update dyanmic provisioning information in 102 all the APs in the WLAN require a prolonged phase-over time, while 103 each AP is updated and the WLAN does not have a single, consistent, 104 configuration. 106 A third problem introduced by large WLAN deployments is the 107 difficulty in dealing effectively with the dynamic nature of the WLAN 108 medium, itself. Due to the shared nature of the wireless medium, 109 shared with APs in the same WLAN, with APs in other WLANs, and with 110 devices that are not APs at all, parameters controlling the wireless 111 medium on each AP must be monitored frequently and modified in a 112 coordinated fashion to maximize performance for the WLAN to utilize 113 the wireless medium efficiently. This must be coordinated among all 114 the access points, to minimize the interference of one access point 115 with its neighbors. Manually monitoring these metrics and 116 determining a new, optimum configuration for the parameters related 117 to the wireless medium is a task that takes a significant amount of 118 time and effort. 120 A fourth problem introduced by large WLAN deployments is securing 121 access to the network and preventing installation of unauthorized 122 access points. Access points are often difficult to physically 123 secure, since their location must often be outside of a locked 124 network closet or server room. Theft of an access point, with its 125 embedded secrets, allows the thief to obtain access to the resources 126 secured by those secrets. 128 Recently, multiple vendors have begun offering proprietary solutions 129 that combine aspects of network switching, centralized control and 130 management, and distributed wireless access in a variety of new 131 architectures to adress some, or all, of the above mentioned 132 problems. Since interoperable solutions allow enterprises and 133 service providers a broader choice, a standardized, interoperable 134 interface between access points and a centralized controller 135 addressing the above mentioned problems seems desirable. 137 The physical portions of this network system, in currently fielded 138 devices, are one or more 802.11 access points (APs) and one or more 139 central control devices, alternatively described as controllers (or 140 access controllers, ACs). Ideally, a network designer would be able 141 to choose one or more vendors for the APs and one or more vendors for 142 the central control devices in sufficient numbers to design a network 143 with 802.11 wireless access to meet the designer's requirements. 145 Current implementations are proprietary and not interoperable. This 146 is due to a number of factors, including the disparate architectural 147 choices made by the various manufacturers. A taxonomy of the 148 architectures employed in the existing products in the market will 149 provide the basis of an output document to be provided to the IEEE 150 802.11 Working Group. This taxonomy will be utilized by the 802.11 151 Working Group as input to their task of defining the functional 152 architecture of an access point. The functional architecture, 153 including description of detailed functional blocks, interfaces, and 154 information flow, will be reviewed by CAPWAP to determine if further 155 work is needed to apply or develop standard protocols providing for 156 multi-vendor interoperable implementations of WLANs built from 157 devices that adhere to the newly appearing hierarchical architecture 158 utilizing a functional split between an access point and an access 159 controller. 161 3. Security Considerations 163 The devices used in WLANs control the access to networks and provide 164 for the delivery of packets between hosts using the WLAN and other 165 hosts on the WLAN or elsewhere on the Internet. The functions for 166 control and provisioning of wireless access points, therefore require 167 protection to prevent misuse of the devices. 169 Requirements for central management, monitoring, and control of 170 wireless access points that should be addressed include 171 confidentiality, integrity, and authenticity. Once an AP and AC have 172 been authenticated to each other, it may not be sufficient that a 173 single level of authorization allows monitoring, as well as control 174 and provisioning. The requirement for more than a single level of 175 authorization should be determined. Physical security should also be 176 addressed, for those devices that contain security parameters that 177 are sensitive and might compromise the security of the system, if 178 those parameters were to fall into the hands of an attacker. 180 APs are often installed in locations that are difficult to secure, in 181 order to provide comprehensive radio coverage. The CAPWAP 182 architecture may reduce the consequences of a stolen AP. If 183 high-value secrets, such as a RADIUS shared secret, are stored in the 184 AC, then the physical loss of an AP does not compromise these 185 secrets. Further, the AC can easily be located in a physically 186 secure location. Of course, concentrating all of the high-value 187 secrets in one place makes the AC an attractive target, and strict 188 physical, procedural, and technical controls are needed to protect 189 the secrets. 191 Authors' Addresses 193 Bob O'Hara 194 Airespace 195 110 Nortech Parkway 196 San Jose, CA 95134 198 Phone: +1 408-635-2025 199 EMail: bob@airespace.com 200 Pat R. Calhoun 201 Airespace 202 110 Nortech Parkway 203 San Jose, CA 95134 205 Phone: +1 408-635-2000 206 EMail: pcalhoun@airespace.com 208 James Kempf 209 Docomo Labs USA 210 181 Metro Drive, Suite 300 211 San Jose, CA 95110 213 Phone: +1 408 451 4711 214 EMail: kempf@docomolabs-usa.com 216 Intellectual Property Statement 218 The IETF takes no position regarding the validity or scope of any 219 intellectual property or other rights that might be claimed to 220 pertain to the implementation or use of the technology described in 221 this document or the extent to which any license under such rights 222 might or might not be available; neither does it represent that it 223 has made any effort to identify any such rights. Information on the 224 IETF's procedures with respect to rights in standards-track and 225 standards-related documentation can be found in BCP-11. 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