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Levkowetz 3 Internet-Draft ipUnplugged 4 Expires: March 31, 2004 Oct 2003 6 DHCP Option for Mobile IP Mobility Agents 7 draft-ietf-dhc-mipadvert-opt 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that other 16 groups may also distribute working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at http:// 24 www.ietf.org/ietf/1id-abstracts.txt. 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 This Internet-Draft will expire on March 31, 2004. 31 Copyright Notice 33 Copyright (C) The Internet Society (2003). All Rights Reserved. 35 Abstract 37 This document defines a new Dynamic Host Configuration Protocol 38 (DHCP) option with suboptions. One suboption is passed from the DHCP 39 Server to the DHCP Client to announce the presence of one or more 40 Mobile IP Mobility Agents. For each announced Mobility Agent, 41 information is provided which is the same as that of the Mobile IP 42 Agent Advertisement extension to ICMP Router Advertisements. There is 43 also one suboption which may be used by a DHCP client to provide 44 identity information to the DHCP server. 46 Table of Contents 48 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 50 2. Requirements terminology . . . . . . . . . . . . . . . . . . . 3 52 3. Mobility Agent Information Option . . . . . . . . . . . . . . 3 53 3.1 Mobility Agent Information Option Definition . . . . . . 3 54 3.2 Network Access Identifier Sub-Option . . . . . . . . . . 4 55 3.3 Mobility Agent Announcement Sub-Option . . . . . . . . . 4 57 4. Mobility Agent Option Usage . . . . . . . . . . . . . . . . . 7 59 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 61 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 63 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 65 Normative References . . . . . . . . . . . . . . . . . . . . . 7 67 Informative References . . . . . . . . . . . . . . . . . . . . 8 69 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8 71 Intellectual Property and Copyright Statements . . . . . . . . 9 73 1. Introduction 75 There already exists a DHCP option to announce Mobile IP Home Agent 76 addresses, described in RFC 2132 [2]. There is, however, no option 77 available to announce Mobile IP Foreign Agents. 79 Announcement of available Mobile IP Mobility Agents by means of DHCP 80 provides possibilities for selective and individual assignment of 81 Mobility Agents to Mobile Nodes. This in turn makes load-sharing and 82 selective service offerings easier. This draft describes a DHCP 83 option for announcing Mobility Agents to DHCP Clients. 85 2. Requirements terminology 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in RFC 2119 [8]. 91 The Mobile IP related terminology used in this document is described 92 in RFC 3220 [5]. 94 3. Mobility Agent Information Option 96 3.1 Mobility Agent Information Option Definition 98 This document defines a new DHCP Option called the Mobility Agent 99 Option. It is a "container" option for specific agent- supplied 100 sub-options. The format of the Mobility Agent option is: 102 Code Len Mobility Agent Information Field 103 +-------+------+------+------+------+------+--...-+------+ 104 | TBD | N | a1 | a2 | a3 | a4 | | aN | 105 +-------+------+------+------+------+------+--...-+------+ 107 The length N gives the total number of octets in the Mobility Agent 108 Field. The Mobility Agent Information field consists of a sequence 109 of SubOpt/Length/Value tuples for each sub-option, encoded in the 110 following manner: 112 SubOpt Len Sub-option Value 113 +------+------+------+------+------+------+--...-+------+ 114 | 1 | N | s1 | s2 | s3 | s4 | | sN | 115 +------+------+------+------+------+------+--...-+------+ 116 SubOpt Len Sub-option Value 117 +------+------+------+------+------+------+--...-+------+ 118 | 2 | N | t1 | t2 | t3 | t4 | | tN | 119 +------+------+------+------+------+------+--...-+------+ 121 The Mobility Agent Information field shall NOT be terminated with a 122 255 sub-option. The length N of the DHCP Mobility Agent Information 123 Option shall include all bytes of the sub-option code/length/value 124 tuples. Since at least one sub-option must be defined, the minimum 125 Mobility Agent Information length is two (2). The length N of the 126 sub-options shall be the number of octets in only that sub-option's 127 value field. A sub-option length may be zero. The sub-options need 128 not appear in sub-option code order. 130 3.2 Network Access Identifier Sub-Option 132 The Network Access Identifier (NAI) defined in RFC 2486 [3] is 133 already used in Mobile IP as an alternative to the home address as an 134 identifier of a mobile node [9]. 136 The Network Access Identifier sub-option of the Mobility Agent 137 Information Option MAY be used by the DHCP client to provide 138 identifying information to the DHCP server, as part of the 139 DHCPDISCOVER message. The server may then use this information in 140 selecting mobility agent announcement parameters for the client. 142 The format of the Network Access Identifier sub-option is as follows: 144 SubOpt Len Sub-option Value 145 +------+-----+-----+-----+-----+-----+--...-+-----+ 146 | 1 | N | Network Access Identifier | 147 +------+-----+-----+-----+-----+-----+--...-+-----+ 149 3.3 Mobility Agent Announcement Sub-Option 151 The Mobility Agent Announcement sub-option announces the address of 152 one or more mobility agents, together with all the information about 153 the mobility agent which is normally found in a Mobile IP Agent 154 Advertisement extension to ICMP Router Advertisements as described in 155 RFC 3220 [5]. 157 All fields are defined so as to correspond to fields of the same name 158 in a Mobility Agent Advertisement Extension as described in RFC 3220 159 [5], and if in the future additional bits are allocated from the 160 'reserved' field for the Mobility Agent Advertisement Extension, they 161 should be equally valid in a DHCP Mobility Agent option. 163 This option may contain announcements of one or more Mobility Agents, 164 in sequence. The length of each individual Mobility Agent 165 Announcement is determined from the Adv-Length field of the 166 announcement. 168 SubOpt Len Sub-option Value (Announcements) 169 +------+-----+-----+-----+--...-+-----+-----+-----+--...-+-----+... 170 | 2 | N | Announcement 1 | Announcement 2 | 171 +------+-----+-----+-----+--...-+-----+-----+-----+--...-+-----+... 173 The format of one Mobility Agent Announcement is as follows: 175 0 1 2 3 176 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 | Mobility Agent IP Address | 179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 180 | Type | Adv-Length | Sequence Number | 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 | Registration Lifetime |R|B|H|F|M|G|r|T| reserved | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 | zero or more care-of addresses | 185 | ... | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 Option code 189 DHCP_MIP_OPTION (to be assigned by IANA) 191 Length 192 Length in bytes of this option, not including the Option code and 193 Length bytes. 195 Agent IP Address 196 The address trough which the Mobile Node may reach the announced 197 Mobility Agent in order to do a Mobile IP registration. 199 Type 200 16. This is the same value as for the type field in a Mobility 201 Agent Advertisement Extension as described in RFC 3220 [5]. If 202 other Mobility Agent Advertisement Extensions are defined in the 203 future, this field will make it possible to differentiate between 204 them without using new DHCP option numbers. 206 Reserved-0 207 Sent as zero; required to be zero on reception for the option 208 described in this document. 210 Adv-Length 211 (6 + 4*N), where 6 accounts for the number of bytes in the 212 Sequence Number, Registration Lifetime, flags, and reserved 213 fields, and N is the number of care-of addresses advertised for 214 the Mobility Agent. 216 Sequence Number 217 The count of Mobility Agent DHCP announcements made since the DHCP 218 server was initialized (RFC 3220, Section 2.3.2 [5]). 220 Registration Lifetime 221 The longest lifetime (measured in seconds) that this agent is 222 willing to accept in any Registration Request. A value of 0xffff 223 indicates infinity. 225 R 226 Registration required. Registration with this foreign agent (or 227 another foreign agent listed in this DHCP option) is required even 228 when using a co-located care-of address. 230 B 231 Busy. The foreign agent will not accept registrations from 232 additional mobile nodes. 234 H 235 Home agent. This agent offers service as a home agent on the link 236 on which this mobility agent announcement is sent. 238 F 239 Foreign agent. This agent offers service as a foreign agent on 240 the link on which this mobility agent announcement is sent. 242 M 243 Minimal encapsulation. This agent implements receiving tunneled 244 datagrams that use minimal encapsulation [7]. 246 G 247 GRE encapsulation. This agent implements receiving tunneled 248 datagrams that use GRE encapsulation [6]. 250 r 251 Sent as zero; ignored on reception. SHOULD NOT be allocated for 252 any other uses. 254 T 255 Foreign agent supports reverse tunneling [11]. 257 reserved 258 Sent as zero; ignored on reception. 260 Care-of Address(es) 261 The foreign agent care-of address(es) provided by this foreign 262 agent. An DHCP Mobility Agent Announcement MUST include at least 263 one care-of address if the 'F' bit is set. The number of care-of 264 addresses present is determined by the Length field in the 265 Extension. 267 4. Mobility Agent Option Usage 269 The requesting and sending of this option follows the rules for DHCP 270 options in RFC 2131 [1] 272 5. Security Considerations 274 DHCP provides an authentication mechanism, as described in RFC 3118 275 [4], which may be used if authentication is required before offering 276 the Mobility Agent option described here. On the other hand, Mobile 277 IP Agent Advertisements as described in RFC 3220 [5] requires no 278 authentication for Agent Advertisement and Agent Solicitation 279 messages. 281 By providing Agent Advertisements by means of DHCP as an alternative 282 to extended ICMP Router Advertisement messages it is possible to do 283 so more selectively, and it does not offer any new threat to the 284 internet. 286 6. IANA Considerations 288 The value for the DHCP_MIP_OPTION code must be assigned from the 289 numbering space defined for public DHCP Options in RFC 2939 [10]. 291 7. Acknowledgements 293 Normative References 295 [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, 296 March 1997. 298 [2] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor 299 Extensions", RFC 2132, March 1997. 301 [3] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC 302 2486, January 1999. 304 [4] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", 305 RFC 3118, June 2001. 307 [5] Perkins, C., "IP Mobility Support for IPv4", RFC 3220, January 308 2002. 310 Informative References 312 [6] Hanks, S., Li, T., Farinacci, D. and P. Traina, "Generic 313 Routing Encapsulation (GRE)", RFC 1701, October 1994. 315 [7] Perkins, C., "Minimal Encapsulation within IP", RFC 2004, 316 October 1996. 318 [8] Bradner, S., "Key words for use in RFCs to Indicate Requirement 319 Levels", BCP 14, RFC 2119, March 1997. 321 [9] Calhoun, P. and C. Perkins, "Mobile IP Network Access 322 Identifier Extension for IPv4", RFC 2794, March 2000. 324 [10] Droms, R., "Procedures and IANA Guidelines for Definition of 325 New DHCP Options and Message Types", BCP 43, RFC 2939, 326 September 2000. 328 [11] Montenegro, G., "Reverse Tunneling for Mobile IP, revised", RFC 329 3024, January 2001. 331 Author's Address 333 Henrik Levkowetz 334 ipUnplugged AB 335 Arenavagen 33 336 Stockholm S-121 28 337 SWEDEN 339 Phone: +46 8 725 9513 340 EMail: henrik@levkowetz.com 342 Intellectual Property Statement 344 The IETF takes no position regarding the validity or scope of any 345 intellectual property or other rights that might be claimed to 346 pertain to the implementation or use of the technology described in 347 this document or the extent to which any license under such rights 348 might or might not be available; neither does it represent that it 349 has made any effort to identify any such rights. 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