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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (May 30, 2008) is 5803 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'RFC 3963' is mentioned on line 337, but not defined ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3775 (Obsoleted by RFC 6275) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) == Outdated reference: A later version (-05) exists of draft-ietf-dhc-dhcpv6-agentopt-delegate-02 Summary: 4 errors (**), 0 flaws (~~), 4 warnings (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Mobile IPv6 Extensions Group R. Droms 3 Internet-Draft P. Thubert 4 Intended status: Informational Cisco 5 Expires: December 1, 2008 F. Dupont 6 ISC 7 W. Haddad 8 Qualcomm 9 May 30, 2008 11 DHCPv6 Prefix Delegation for NEMO 12 draft-droms-mext-nemo-pd-00 14 Status of this Memo 16 By submitting this Internet-Draft, each author represents that any 17 applicable patent or other IPR claims of which he or she is aware 18 have been or will be disclosed, and any of which he or she becomes 19 aware will be disclosed, in accordance with Section 6 of BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt. 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 This Internet-Draft will expire on December 1, 2008. 39 Abstract 41 One aspect of network mobility support is the assignment of a prefix 42 or prefixes to a Mobile Router (MR) for use on the links in the 43 Mobile Network. DHCPv6 prefix delegation can be used for this 44 configuration task. 46 1. Introduction 48 One aspect of network mobility support is the assignment of a prefix 49 or prefixes to a Mobile Router for use on the links in the Mobile 50 Network. DHCPv6 prefix delegation [RFC3633] (DHCPv6PD) can be used 51 for this configuration task. 53 2. Terminology 55 The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 56 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be 57 interpreted as described in RFC2119 [RFC2119]. 59 The following terms used in this document are defined in the IPv6 60 Addressing Architecture document [RFC4291]: 61 link-local unicast address 62 link-local scope multicast address 64 The following terms used in this document are defined in the mobile 65 IPv6 specification [RFC3775]: 66 home agent (HA) 67 home link 69 The following terms used in this document are defined in the Mobile 70 Network terminology document [RFC4886]: 71 Mobile Router (MR) 72 Mobile Network 73 mobile host (MH) 75 The following terms used in this document are defined in the DHCPv6 76 [RFC3315] and DHCPv6 prefix delegation [RFC3633] specifications: 77 delegating router (DR) 78 requesting router (RR) 79 DHCPv6 relay agent 81 The following acronym is used in this document: 82 DHCPv6PD: DHCPv6 prefix delegation 84 3. Application of DHCPv6 prefix delegation to mobile networks for 85 delegation of home prefixes 87 The NEMO Basic protocol [RFC3963] extends the mobile IPv6 protocol 88 [RFC3775] to enable network mobility. In this extension, a MR uses 89 the mobile IPv6 protocol to establish and maintain a session with its 90 HA, and uses bidirectional tunneling between the MR and HA to provide 91 a path through which hosts attached to links in the Mobile Network 92 can maintain connectivity with nodes not in the Mobile Network. 94 The requirements for NEMO [RFC4885] include the ability of the MR to 95 receive delegated prefixes that can then be assigned to links in the 96 Mobile Network. DHCPv6PD can be used to meet this requirement for 97 prefix delegation. 99 To use DHCPv6PD for Mobile Networks, the HA assumes the role of 100 either the DR or a DHCPv6 relay agent and the MR assumes the role of 101 the RR. Throughout the remainder of this document, the HA will be 102 assumed to be acting as a DHCPv6PD DR or relay agent and the MR will 103 be assumed to be acting as a RR. 105 If the HA is acts as relay agent, some other device acts as the DR. 106 For example, the server providing DHCPv6 service in the home network 107 might also provide NEMO DHCPv6PD service. Or, a home network with 108 several HAs might configure one of those HAs as a DHCPv6PD server 109 while the other HAs act as relay agents. 111 The HA and MR exchange DHCPv6PD protocol messages through the tunnel 112 connecting them. The tunnel acts as the link labeled "DSL to 113 subscriber premises" in figure 1 of the DHCPv6PD specification. 115 The DHCPv6PD server is provisioned with prefixes to be assigned using 116 any of the prefix assignment mechanisms described in the DHCPv6PD 117 specifications. Other updates to the HA data structures required as 118 a side effect of prefix delegation are specified by the particular 119 network mobility protocol. For example, in the case of Basic Network 120 Mobility Support [RFC3963], the HA would add an entry in its binding 121 cache registering the delegated prefix to the MR to which the prefix 122 was delegated. 124 3.1. When the MR uses DHCPv6 126 The MR initiates a DHCPv6 message exchange for prefix delegation 127 whenever it establishes an MRHA tunnel to its HA. If the MR does not 128 have any active delegated prefixes (with unexpired leases), the MR 129 initiates a DHCPv6 message exchange with a DHCPv6 Solicit message as 130 described in section 17 of RFC 3315 and section 12 of RFC 3633. If 131 the MR has one or more active delegated prefixes, the MR initiates a 132 DHCPv6 message exchange with a DHCPv6 Confirm message as described in 133 section 18.1.2 of RFC 3315 and section 12 of RFC 3633. 135 3.2. Use of MRHA tunnel for DHCPv6 messages 137 The DHCPv6 specification requires the use of link-local unicast and 138 link-local scope multicast addresses in DHCPv6 messages (except in 139 certain cases as defined in section 22.12 of the DHCPv6 140 specification). Section 10.4.2 of the mobile IPv6 specification 141 describes forwarding of intercepted packets, and the third paragraph 142 of that section begins: 144 However, packets addressed to the mobile node's link-local address 145 MUST NOT be tunneled to the mobile node. 147 The DHCPv6 messages exchanged between the HA and the MR originate 148 only with the HA and the MR, and therefore are not "intercepted 149 packets" and may be sent between the HA and the MR through the 150 tunnel. 152 Even though the MRHA tunnel is a point to point connection, the MR 153 SHOULD use multicast DHCPv6 messages as described in RFC 3315 over 154 that tunnel. 156 3.3. DHCPv6 Relay Agent for transmission of DHCPv6 messages 158 A DHPCv6 relay agent function [RFC3315] can be used as an alternative 159 to multicast DHCPv6 messages over the tunnel between the MR and the 160 HA. In this configuration, the relay agent function is co-located in 161 the MR with the DHCPv6 client function. Rather than using multicast 162 to send DHCPv6 messages through the tunnel to the DHCPv6 server, the 163 DHCPv6 client in the MR hands any outbound DHCPv6 messages to the co- 164 located relay agent. Responses from the DHCPv6 server are delivered 165 to the relay agent function in the MR, which extracts the 166 encapsulated message and delivers it to the DHCPv6 client in the MR. 168 3.3.1. Relay agent configuration 170 The use of the relay agent function in the MR allows the MR to 171 unicast DHCPv6 messages to the DHCPv6 server. The relay agent must 172 be configured with the address of the DHCPv6 server or another DHCPv6 173 relay agent that will forward message on to a DHCPv6 server. For the 174 purposes of NEMO, the relay agent assumes that the HA for the MR 175 hosts the next hop in the path the to the DHCPv6 server: either the 176 DHCPv6 server or a relay agent that will forward message to the 177 DHCPv6 server. Therefore, if the MR acts as a DHCPv6 relay agent, 178 the MR MUST configure the DHCPv6 relay agent to forward DHCPv6 179 messages to the HA. 181 3.3.2. Transmission of DHCPv6 messages 183 In this configuration, when the DHCPv6 client in the MR sends a 184 message, it hands the message to the DHCPv6 relay agent in the MR. 185 The way in which this handoff takes place is beyond the scope of this 186 document. The relay agent encapsulates the message from the client 187 according to RFC 3315 in a Relay-forward message and sends the 188 resulting DHCPv6 message to the HA. The relay agent sets the fields 189 in the Relay-forward message as follows: 190 msg-type RELAY-FORW 191 hop-count 1 192 link-address A non-link-local address from the MR interface to the 193 tunnel between the HA and MR 194 peer-address A non-link-local address from the MR interface to the 195 tunnel between the HA and MR 196 options MUST include a "Relay Message option" [RFC3315]; MAY 197 include other options added by the relay agent. 199 3.3.3. Receipt of DHCPv6 messages 201 In this configuration, messages from the DHCPv6 server will be 202 returned to the DHCPv6 relay agent, with the message for the DHCPv6 203 client encapsulated in the Relay Message option [RFC3315] in a Relay- 204 reply message. The relay agent function extracts the message for the 205 client from the Relay Message option and hands the message to the 206 DHCPv6 client in the MR. The way in which this handoff takes place 207 is beyond the scope of this document. 209 3.4. Exchanging DHCPv6 messages when MR is at home 211 When the MR is on its home link, the HA uses the home link to 212 exchange DHCPv6PD messages with the MR. It is the responsibility of 213 the implementation to determine when the MR is on its home link and 214 to avoid use of any existing tunnel. 216 3.5. Minimizing DHCPv6PD messages 218 DHCPv6PD in a Mobile Network can be combined with the Rapid Commit 219 option [RFC3315] to provide DHCPv6 prefix delegation with a two 220 message exchange between the mobile node and the DHCPv6 PD server. 222 3.6. DHCPv6PD and DHAAD 224 The MR acting as RR needs a direct link to the DR (or relay) 225 function. When the MR is away from Home, that link is the MRHA 226 tunnel. If a MR needs to obtain a prefix by means of DHCPv6PD, it 227 has to locate a HA that is capable of serving either as a DHCPv6PD 228 relay agent or server. Since the use of DHCPv6PD is optional and 229 comes as an addition to existing protocols [RFC3775] and [RFC3963], 230 it can not be expected that all HAs are DHCPv6PD capable. 232 This specification extends Dynamic Home Agent Address Discovery and 233 the Home Agent Information Option in order to enable the detection by 234 a MR of all HAs that are DHCPv6PD capable. A new 'D' bit is 235 introduced to let Home Agents advertise that they are willing to 236 participate to DHCP. Note that there is no need for the MR acting as 237 RR to know whether a HA is actually a DR or simply acting as a relay. 239 3.6.1. Modified Dynamic Home Agent Address Discovery Request 241 A new flag (D) (Support for DHCPv6PD) is introduced in the DHAAD 242 Request message, defined in [RFC3775] and [RFC 3963]. The Mobile 243 Router sets this flag to indicate that it wants to discover Home 244 Agents participating to DHCPv6 Prefix Delegation. 246 A the MR which sets the 'D' flag MUST also set the 'R' flag, to 247 declare that it is a Mobile Router and asks for a HA that supports 248 Mobile Routers, as defined in [RFC 3963]. 250 0 1 2 3 251 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 1 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | Type | Code | Checksum | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | Identifier |R|D| Reserved | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 DHCPv6PD Support Flag (D) 260 A one-bit flag that when set indicates that the Mobile Router 261 wants to discover Home Agents participating to DHCPv6 Prefix 262 Delegation. 264 For a description of the other fields in the message, see [RFC3775] 265 and [RFC 3963]. 267 3.6.2. Modified Dynamic Home Agent Address Discovery Reply 269 A new flag (D) (Support for DHCPv6PD) is introduced in the DHAAD 270 Reply message, defined in [RFC3775] and [RFC 3963]. If a Home Agent 271 receives a Dynamic Home Agent Discovery request message with the 272 DHCPv6PD Support Flag set, it MUST reply with a list of Home Agents 273 participating to DHCPv6PD. 275 The DHCPv6PD Support Flag MUST be set if there is at least one Home 276 Agent participating to DHCPv6PD. In that case, the reply will list 277 only those HAs that participate to DHCPv6PD, whether they act as 278 servers (DRs) or relays. 280 A HA that supports DHCPv6PD MUST support Mobile Routers as well, so 281 if the 'D' bit is set, then the 'R' bit should be set as well. So 282 there is no need in an implementation to support the case where some 283 HAs would support Mobile Routers while others would be participating 284 to DHCPv6 Prefix Delegation but none could do both. 286 If none of the Home Agents support DHCPv6PD, the Home Agent MAY reply 287 with a list of Home Agents that only support NEMO basic Mobile 288 Routers or Mobile IPv6 Mobile Nodes. In this case, the DHCPv6PD 289 Support Flag MUST be set to 0. 291 The modified message format is as follows. 293 0 1 2 3 294 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 1 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 296 | Type | Code | Checksum | 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | Identifier |R|D| Reserved | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | | 301 + + 302 + + 303 | | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 DHCPv6PD Support Flag (D) 308 A one-bit flag that when set indicates that the Home Agents 309 listed in this message participate to DHCPv6 Prefix Delegation. 311 For a description of the other fields in the message, see [RFC3775] 312 and [RFC 3963]. 314 3.6.3. Modified Home Agent Information Option 316 A new flag (D) (Support for DHCPv6PD) is introduced in the Home Agent 317 Information Option defined in [RFC3775] and [RFC 3963]. 319 If a Home Agent participates to DHCPv6PD, it SHOULD set the flag. If 320 the HA sets the 'D' flag, then it MUST also set the 'R' flag, 321 Indicating that it supports Mobile Routers, as defined in [RFC 3963]. 323 0 1 2 3 324 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 1 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | Type | Length |R|D| Reserved | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | Home Agent Preference | Home Agent Lifetime | 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 DHCPv6PD Support Flag (D) 333 A one-bit flag that when set indicates that the Home Agents 334 participates to DHCPv6 Prefix Delegation. 336 For a description of the other fields in the message, see [RFC3775] 337 and [RFC 3963]. 339 3.7. Location of DHCPv6PD Delegating Router function 341 Support of DHCPv6PD for a Mobile Network is optional. 343 The use of a DHCPv6 relay agent is not defined for DHCPv6PD in the 344 DHCPv6PD specification [RFC3633]. If the DHCPv6PD DR function is 345 implemented in the HA for the MR, no relay agent function is 346 required. 348 It may be desirable to use a single DR to manage RRs in a network 349 with multiple HAs. In this scenario, the HAs will act as DHCP relay 350 agents, forwarding messages between the RRs and the DR. 352 Use of the DHCPv6 relay agent function with DHCPv6PD requires that 353 there be some mechanism through which routing information for the 354 delegated prefixes can be added to the appropriate routing 355 infrastructure. If the HA is acting as a DHCPv6 relay agent, the HA 356 SHOULD add a route to the delegated prefix and advertise that route 357 after receiving a binding update for the prefix from the RR 358 [RFC3963]. 360 In particular, if the MR uses NEMO explicit mode, then it must add 361 the delegated prefix to the prefix list in the Binding Update 362 messages. If the binding cache is cleared before the prefix valid 363 lifetime, the MR might bind that prefix again using explicit mode, 364 till the lifetime expires. 366 In implicit mode, the HA must save the delegated prefix with the 367 binding cache entry of the Mobile Router. When the BCE is cleared, 368 the HA loses the information about the delegated prefix. Because the 369 MR will use DHCPv6 when it reestablishes its tunnel to the HA (see 370 Section 3.1), the HA will be able to add the delegated prefix back to 371 the BCE. 373 At the time this draft was written, one way in which a DR can 374 explicitly notify a relay agent about delegated prefixes, is to use 375 the "DHCP Relay Agent Assignment Notification Option" 376 [I-D.ietf-dhc-dhcpv6-agentopt-delegate]. 378 Another alternative, if the RR is part of the same administrative 379 domain as the home network to which it is attached through the HA, 380 and the RR can be trusted, the RR can use a routing protocol like 381 OSPF to advertise any delegated prefixes. 383 NEMO explicit mode is recommended to take advantage of the function 384 already defined for NEMO. 386 3.8. Other DHCPv6 functions 388 The DHCPv6 messages exchanged between the MR and the HA may also be 389 used for other DHCPv6 functions in addition to DHCPv6PD. For 390 example, the HA may assign global addresses to the MR and may pass 391 other configuration information such as a list of available DNS 392 recursive resolvers to the MR using the same DHCPv6 messages as used 393 for DHCPV6PD. 395 The HA may act as a DHCPv6 relay agent for MHs while it acts as a DR 396 for MRs. 398 4. Changes in this draft 400 This document is based on draft-ietf-nemo-dhcpv6-pd-03 and includes 401 the use of the DHCPv6 relay agent in the MR, as described in 402 Section 3.3, from draft-dupont-mext-dhcrelay-00. 404 5. Security Considerations 406 This document describes the use of DHCPv6 for prefix delegation in 407 Mobile Networks. It does not introduce any additional security 408 considerations beyond those described in the "Security 409 Considerations" section of the DHCPv6 base specification [RFC3315] 410 and the "Security Considerations" of the DHCPv6 Prefix Delegation 411 specification [RFC3633]. 413 Following the DHCPv6 Prefix Delegation specification, HAs and MRs 414 SHOULD use DHCPv6 authentication as described in section 415 "Authentication of DHCP messages" of the DHCPv6 specification 416 [RFC3315], to guard against attacks mounted through prefix 417 delegation. 419 6. IANA Considerations 421 This document describes the use of DHCPv6 for prefix delegation in 422 Mobile Networks. It does not introduce any additional IANA 423 considerations. 425 7. Normative References 427 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 428 Host Configuration Protocol (DHCP) version 6", RFC 3633, 429 December 2003. 431 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 432 Requirement Levels", BCP 14, RFC 2119, March 1997. 434 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 435 Architecture", RFC 4291, February 2006. 437 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 438 in IPv6", RFC 3775, June 2004. 440 [RFC4885] Ernst, T. and H-Y. Lach, "Network Mobility Support 441 Terminology", RFC 4885, July 2007. 443 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 444 and M. Carney, "Dynamic Host Configuration Protocol for 445 IPv6 (DHCPv6)", RFC 3315, July 2003. 447 [RFC4886] Ernst, T., "Network Mobility Support Goals and 448 Requirements", RFC 4886, July 2007. 450 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 451 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 452 RFC 3963, January 2005. 454 [I-D.ietf-dhc-dhcpv6-agentopt-delegate] 455 Droms, R., "DHCPv6 Relay Agent Assignment Notification 456 (RAAN) Option", draft-ietf-dhc-dhcpv6-agentopt-delegate-02 457 (work in progress), November 2006. 459 Authors' Addresses 461 Ralph Droms 462 Cisco 463 1414 Massachusetts Avenue 464 Boxborough, MA 01719 465 USA 467 Phone: +1 978.936.1674 468 Email: rdroms@cisco.com 470 Pascal Thubert 471 Cisco 472 Village d'Entreprises Green Side 473 400, Avenue Roumanille 474 Biot - Sophia Antipolis 06410 475 FRANCE 477 Email: pthubert@cisco.com 479 Francis Dupont 480 ISC 482 Email: Francis.Dupont@fdupont.fr 484 Wassim Haddad 485 Qualcomm 487 Email: whaddad@qualcomm.com 489 Full Copyright Statement 491 Copyright (C) The IETF Trust (2008). 493 This document is subject to the rights, licenses and restrictions 494 contained in BCP 78, and except as set forth therein, the authors 495 retain all their rights. 497 This document and the information contained herein are provided on an 498 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 499 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 500 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 501 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 502 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 503 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 505 Intellectual Property 507 The IETF takes no position regarding the validity or scope of any 508 Intellectual Property Rights or other rights that might be claimed to 509 pertain to the implementation or use of the technology described in 510 this document or the extent to which any license under such rights 511 might or might not be available; nor does it represent that it has 512 made any independent effort to identify any such rights. 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