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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4306 (ref. '2') (Obsoleted by RFC 5996) -- Obsolete informational reference (is this intentional?): RFC 3775 (ref. '3') (Obsoleted by RFC 6275) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group V. Devarapalli 3 Internet-Draft WiChorus 4 Intended status: Standards Track K. Weniger 5 Expires: October 15, 2009 April 13, 2009 7 Redirect Mechanism for IKEv2 8 draft-ietf-ipsecme-ikev2-redirect-08.txt 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. This document may not be modified, 14 and derivative works of it may not be created, except to format it 15 for publication as an RFC or to translate it into languages other 16 than English. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on October 15, 2009. 36 Copyright Notice 38 Copyright (c) 2009 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents in effect on the date of 43 publication of this document (http://trustee.ietf.org/license-info). 44 Please review these documents carefully, as they describe your rights 45 and restrictions with respect to this document. 47 Abstract 49 IKEv2 is a protocol for setting up VPN tunnels from a remote location 50 to a gateway so that the VPN client can access services in the 51 network behind the gateway. Currently there is no standard mechanism 52 specified that allows an overloaded VPN gateway or a VPN gateway that 53 is being shut down for maintenance to redirect the VPN client to 54 attach to another gateway. This document proposes a redirect 55 mechanism for IKEv2. The proposed mechanism can also be used in 56 Mobile IPv6 to enable the home agent to redirect the mobile node to 57 another home agent. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 63 3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 4 64 4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 5 65 5. Gateway Initiated Redirect . . . . . . . . . . . . . . . . . . 6 66 6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 7 67 7. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 8 68 7.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 8 69 7.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 8 70 7.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 10 71 8. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 10 72 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 73 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 74 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 75 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 76 12.1. Normative References . . . . . . . . . . . . . . . . . . . 12 77 12.2. Informative References . . . . . . . . . . . . . . . . . . 12 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 80 1. Introduction 82 IKEv2 [2] is used for setting up IPsec-based VPNs. The IP address of 83 the VPN gateway can be configured on the VPN client. But this does 84 not scale well, when the number of VPN gateways is large. Dynamic 85 discovery of VPN gateways using DNS is quite widely used too. 86 However, using DNS is not flexible when it comes to assigning a VPN 87 gateway to the VPN client based on the load on the VPN gateways. The 88 VPN client typically tries to connect to the IP address of the VPN 89 gateways that appears first in the DNS response. If the VPN tunnel 90 setup fails, then the VPN client tries to attach to the other VPN 91 gateways returned in the DNS response. 93 This document proposes a redirect mechanism for IKEv2 that enables a 94 VPN gateway to redirect the VPN client to another VPN gateway, for 95 example, based on the load condition. The redirect can be done 96 during the IKE_SA_INIT or the IKE_AUTH exchange. Gateway-initiated 97 redirect in the middle of a session is also supported. The redirect 98 mechanism can also be used in conjunction with anycast addresses. In 99 this case, anycast address for the cluster of VPN gateways is stored 100 in the DNS instead of a list of unicast IP addresses of the VPN 101 gateways. 103 The redirect can also happen because of administrative or optimal 104 routing reasons. This document does not attempt to provide an 105 exhaustive list of reasons for redirecting a VPN client to another 106 VPN gateway. 108 Mobile IPv6 [3] may use IKEv2 for mutual authentication between the 109 mobile node and the home agent. IKEv2 may also be used for home 110 address configuration and setting up IPsec security associations for 111 protecting Mobile IPv6 signaling messages [4]. The IKEv2 exchange 112 precedes the exchange of Mobile IPv6 signaling messages. Therefore 113 the mechanism described in this document can also be used by a Mobile 114 IPv6 home agent to redirect a mobile node to another home agent. 116 There is a Home Agent Switch mechanism available for redirecting a 117 mobile node to another home agent, described in [5]. The Home Agent 118 Switch mechanism can only be used after the binding cache had been 119 created at the home agent for the mobile node. The disadvantage with 120 this is that quite a bit of state is created on the home agent before 121 the mobile node can be redirected to another home agent. The 122 mechanism described in this document can be used for redirecting a 123 mobile node before any state related to the Mobile IPv6 binding is 124 created on the home agent. 126 2. Terminology 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in [1]. 132 3. IKEv2 Initial Exchange with Redirect 134 This section describes the use of Redirect mechanism during the 135 IKE_SA_INIT exchange. Gateway-initiated redirect and the use of 136 redirect during IKE_AUTH exchange are explained in subsequent 137 sections. 139 To redirect an IKEv2 session to another VPN gateway, the VPN gateway 140 that initially received the IKE_SA_INIT request selects another VPN 141 gateway and responds to the VPN client with a REDIRECT Notification 142 payload. The mechanism by which the initial VPN gateway selects 143 another VPN gateway is out of scope for this document. The IP 144 address of the selected VPN gateway is sent in the REDIRECT payload. 145 The gateway MUST include the nonce data from the Ni payload sent by 146 the initiator in the REDIRECT payload. This prevents certain Denial- 147 of-Service attacks on the initiator that could be caused by an 148 attacker injecting IKE_SA_INIT responses with REDIRECT payloads. 150 The VPN client indicates support for the IKEv2 redirect mechanism and 151 the willingness to be redirected by including a REDIRECT_SUPPORTED 152 notification message in the initial IKE_SA_INIT request. If the 153 IKE_SA_INIT request did not include the REDIRECT_SUPPORTED payload, 154 the responder MUST NOT send the REDIRECT payload to the VPN client. 156 Initiator Responder (initial VPN GW) 157 --------- ------------------------- 159 (IP_I:500 -> Initial_IP_R:500) 160 HDR(A,0), SAi1, KEi, Ni, --> 161 N(REDIRECT_SUPPORTED) 163 (Initial_IP_R:500 -> IP_I:500) 164 <-- HDR(A,0), N(REDIRECT, IP_R) 166 When the VPN client receives the IKE_SA_INIT response with the 167 REDIRECT payload, it initiates a new IKE_SA_INIT exchange with the 168 VPN gateway listed in the REDIRECT payload provided this is allowed 169 by its IPsec policy. The VPN client includes the IP address of the 170 original VPN gateway that redirected the client. The IKEv2 exchange 171 then proceeds as normal with the selected VPN gateway. 173 Initiator Responder (Selected VPN GW) 174 --------- --------------------------- 176 (IP_I:500 -> IP_R:500) 177 HDR(A,0), SAi1, KEi, Ni, --> 178 N(REDIRECTED_FROM, Initial_IP_R) 180 (IP_R:500 -> IP_I:500) 181 <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] 183 (IP_I:500 -> IP_R:500) 184 HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] 185 [IDr,]AUTH, SAi2, TSi, TSr} --> 187 (IP_R:500 -> IP_I:500) 188 <-- HDR(A,B), SK {IDr, [CERT,] AUTH, 189 SAr2, TSi, TSr} 191 When this mechanism is used with Mobile IPv6, care must be taken to 192 ensure that the home agent information is consistent with the IKEv2 193 gateway information. The Mobile IPv6 home agent discovery mechanisms 194 (for instance, RFC 5026 [4]) would have configured the mobile node 195 with a particular home agent. When the mobile node initiates an 196 IKEv2 exchange with the home agent and is redirected to another 197 gateway, the home agent information should also be updated, subject 198 to the policy on the mobile node. 200 4. Use of Anycast Addresses with the Redirect Mechanism 202 The use of anycast addresses will avoid having to configure a 203 particular VPN gateway's IP address in the DNS. Instead, the anycast 204 address that represents the group of VPN gateways is stored in the 205 DNS. When the VPN client performs a DNS lookup for the VPN gateway, 206 it receives the anycast address of the VPN gateway in the DNS 207 response. 209 If an anycast address is returned in response to DNS resolution of an 210 FQDN, the VPN client sends the IKE_SA_INIT request to the anycast 211 address. The IKE_SA_INIT request is routed to one of the VPN 212 gateways that is part of the anycast group. The VPN gateway that 213 receives the IKE_SA_INIT request responds with an IKE_SA_INIT reply 214 from the anycast address. 216 Initiator Responder (any VPN GW) 217 --------- ------------------------- 219 (IP_I:500 -> ANYCAST:500) 220 HDR(A,0), SAi1, KEi, Ni) --> 221 N(REDIRECT_SUPPORTED) 223 (ANYCAST:500 -> IP_I:500) 224 <-- HDR(A,0), N(REDIRECT, IP_R) 226 If the destination address on the IKE_SA_INIT request is an anycast 227 address, the VPN gateway that received the IKE_SA_INIT request MUST 228 include the REDIRECT payload to redirect the VPN client to a unicast 229 address of one of the VPN gateway. The VPN gateway that received the 230 IKE_SA_INIT request MAY redirect the client to its own unicast 231 address, if it is not overloaded. 233 The rest of the IKEv2 exchange is the same as described in Section 3. 235 5. Gateway Initiated Redirect 237 The redirect mechanism may also be used by a VPN gateway to redirect 238 the client to another VPN gateway in middle of a session. To 239 redirect a client, the gateway should send an INFORMATIONAL message 240 with the REDIRECT Notify payload. The REDIRECT payload MUST carry 241 information about the new VPN gateway. The gateway MUST NOT include 242 any nonce data in the REDIRECT payload, since it is a gateway- 243 initiated message and is protected by the IKEv2 security association. 244 When the client receives this message, it MUST send an empty message 245 as an acknowledgement. Until the client responds with an 246 acknowledgement, the gateway SHOULD re-transmit the redirect 247 INFORMATIONAL message as described in [2]. The following illustrates 248 the INFORMATIONAL message exchange for gateway-initiated redirect. 250 Initiator (VPN client) Responder (VPN GW) 251 ---------------------- ------------------ 253 <-- HDR, SK {N[REDIRECT, IP_R/FQDN_R]} 255 HDR, SK {} --> 257 The INFORMATIONAL message exchange described above is protected by 258 the existing IKEv2 SA between the client and the gateway. 260 Once the client sends an acknowledgement to the gateway, it SHOULD 261 delete the existing security associations with the old gateway by 262 sending an Informational message with a DELETE payload. The gateway 263 MAY also decide to delete the security associations without any 264 signaling from the client, again by sending an Informational message 265 with a DELETE payload. However, it should allow sufficient time for 266 the client to setup the required security associations with the new 267 security gateway. This time period should be configurable on the 268 gateway. 270 6. Redirect During IKE_AUTH Exchange 272 If the gateway decides to redirect the client during the IKE_AUTH 273 exchange, based on the identity presented by the client in the 274 IKE_AUTH request message, it prevents the creation of a CHILD SA and 275 sends the REDIRECT payload in the IKE_AUTH response. When the client 276 receives the IKE_AUTH response with the REDIRECT payload, it SHOULD 277 delete the existing IKEv2 security association with the gateway. The 278 gateway MUST verify the client's AUTH payload before sending the 279 Redirect payload, and the client MUST verify the gateway's AUTH 280 payload before acting on the Redirect payload. 282 Initiator Responder ( VPN GW) 283 --------- ------------------- 285 (IP_I:500 -> IP_R:500) 286 HDR(A,0), SAi1, KEi, Ni, --> 287 N(REDIRECTED_SUPPORTED) 289 (IP_R:500 -> IP_I:500) 290 <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] 292 (IP_I:500 -> IP_R:500) 293 HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] 294 [IDr,]AUTH, SAi2, TSi, TSr} --> 296 (IP_R:500 -> IP_I:500) 297 <-- HDR(A,B), SK {IDr, [CERT,] AUTH, 298 N[REDIRECT, IP_R/FQDN_R]} 300 In case the IKE_AUTH exchange involves EAP authentication as 301 described in Section 2.16 of RFC 4306 [2] or multiple authentication 302 methods as described in RFC 4739 [6], the IKE_AUTH exchange is more 303 complicated. The identity presented by the client in the first 304 IKE_AUTH request might be a temporary one. In addition, the gateway 305 might decide to redirect the client based on the interaction with the 306 the AAA server, when EAP authentication is used or the external 307 authentication server, when multiple authentication methods are used. 308 In such cases, the gateway should send the REDIRECT notification 309 payload in the final IKE_AUTH response message that carries the AUTH 310 payload and the traffic selectors. The gateway MUST NOT send and the 311 client MUST NOT accept a redirect in an earlier IKE_AUTH message. 313 7. Redirect Messages 315 7.1. REDIRECT_SUPPORTED 317 The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT 318 request by the initiator to indicate support for the IKEv2 redirect 319 mechanism described in this document. 321 1 2 3 322 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 1 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | Next Payload |C| RESERVED | Payload Length | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | Protocol ID | SPI Size (=0) | Notify Message Type | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 330 the 'Notify Message Type' fields are the same as described in Section 331 3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 332 the SPI is not present in this message. The 'Protocol ID' MUST be 333 set to 0, since the notification is not specific to a particular 334 security association. 336 The 'Payload Length' field MUST be set to '8'. The 'Notify Message 337 Type' field is set to indicate the REDIRECT_SUPPORTED payload . 340 7.2. REDIRECT 342 The REDIRECT payload is included in an IKE_SA_INIT response from the 343 responder or an INFORMATIONAL message from the responder, when the 344 responder wants to redirect the initiator to another VPN gateway. 345 The message includes the new responder's IP address. 347 1 2 3 348 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 1 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 | Next Payload |C| RESERVED | Payload Length | 351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 352 | Protocol ID | SPI Size (=0) | Notify Message Type | 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 354 | GW Ident Type | GW Ident Len | | 355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 356 ~ New Responder GW Identity ~ 357 | | 358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 359 | | 360 ~ Nonce Data ~ 361 | | 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 365 the 'Notify Message Type' fields are the same as described in Section 366 3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 367 the SPI is not present in this message. The 'Protocol ID' MUST be 368 set to 0, since the notification is not specific to a particular 369 security association. 371 The 'Payload Length' field is set to the length in octets of the 372 entire payload, including the generic payload header. 'Notify 373 Message Type' field is set to indicate the REDIRECT payload . The 'GW Identity Type' field indicates the 375 type of information that is sent to identify the new VPN gateway. 376 The following values are reserved by this document. 378 1 - IPv4 address of the new VPN gateway 379 2 - IPv6 address of the new VPN gateway 380 3 - FQDN of the new VPN gateway 382 All other values for this field are reserved and MUST NOT be used. 383 The 'GW Ident Len' field is set to the length of the gateway identity 384 information. The identity of the new VPN gateway is carried in the 385 'New Responder GW Identity' field. 387 The 'Nonce Data' field carries the nonce data from the Ni payload 388 sent by the initiator. The size of the nonce MUST be between 16 and 389 256 bytes as described in Section 3.9 of [2]. The 'Nonce Data' field 390 is present in the REDIRECT payload only when the REDIRECT payload is 391 sent in the IKE_SA_INIT response message. It MUST NOT be included in 392 the REDIRECT payload if sent in an IKE_AUTH response or in a gateway- 393 initiated redirect message. 395 7.3. REDIRECTED_FROM 397 The REDIRECTED_FROM message type is included in the IKE_SA_INIT 398 request from the initiator to the new VPN gateway to indicate the IP 399 address of the original VPN gateway that redirected the initiator. 400 The original VPN gateway's IP address is included in the message. 402 1 2 3 403 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 1 404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 405 | Next Payload |C| RESERVED | Payload Length | 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 | Protocol ID | SPI Size (=0) | Notify Message Type | 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 | GW Ident Type | GW Ident Len | | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ 411 ~ Original Responder GW Identity ~ 412 | | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 416 the 'Notify Message Type' fields are the same as described in Section 417 3.10 of [2] The 'SPI Size' field MUST be set to 0 to indicate that 418 the SPI is not present in this message. The 'Protocol ID' MUST be 419 set to 0, since the notification is not specific to a particular 420 security association. 422 The 'Payload Length' field MUST be set to either '13' or '25' 423 depending on whether an IPv4 or IPv6 address of the original VPN 424 gateway is sent in the message. The 'Notify Message Type' field is 425 set to indicate the REDIRECTED_FROM payload . The 'GW Identity Type' field indicates the type of 427 information that is sent to identify the new VPN gateway. The 428 following values are reserved by this document. 430 1 - IPv4 address of the original VPN gateway 431 2 - IPv6 address of the original VPN gateway 433 All other values for this field are reserved and MUST NOT be used. 434 The 'GW Ident Len' field is set to the length of the gateway identity 435 information. The identity of the original VPN gateway is carried in 436 the 'Original Responder GW Identity' field. 438 8. Use of the Redirect Mechanism between IKEv2 Peers 440 The Redirect mechanism described in this document is mainly intended 441 for use in client-gateway scenarios. However, the mechanism can also 442 be used between any two IKEv2 peers. But this protocol is 443 asymmetric, meaning that only the original responder can redirect the 444 original initiator to another server. 446 9. Security Considerations 448 An eavesdropper on the path between VPN client and server may send a 449 redirect to the client upon receiving an IKE_SA_INIT message from 450 this client. This is no problem regarding DoS attacks for the VPN 451 connection, since an on-path-attacker can as well drop the 452 IKE_SA_INIT requests to prevent VPN access for the client. But an 453 eavesdropper on the path between VPN client and server can redirect a 454 large number of clients to a victim, which is then flooded with 455 IKE_SA_INIT requests. Flooding only happens if many clients initiate 456 IKEv2 exchange at almost the same time, which is considered a rare 457 event. However, this may happen if a Home Agent/VPN server is 458 shutdown for maintenance and all clients need to re-establish VPN 459 connections with another Home Agent/VPN server or if the on-path 460 attacker forces all IPsec security associations to expire by dropping 461 all received IKEv2 messages. 463 The use of REDIRECTED_FROM payload is intended to discourage a rogue 464 VPN gateway from redirecting a large number of VPN clients to a 465 particular VPN gateway. It does not prevent such a DoS attack. 467 Since the redirect message is not always sent as a secure message, it 468 MUST NOT result in the modification of the PAD entries on the client. 469 The new gateway, to which the client is redirected to should be 470 subject to the same authentication and authorization requirements as 471 the original gateway. To support a scenario where the FQDN of the 472 gateway is in the client's PAD entry and the client is redirected to 473 another gateway in the same administrative domain, one can either 474 configure all the possible gateways from the domain or use a wildcard 475 entry like, for example, GW*.example.com, in the client's 476 corresponding PAD entry. 478 10. IANA Considerations 480 This document defines four new IKEv2 Notification Message types as 481 described in Section 7. The three Notify Message Types must be 482 assigned values between 16396 and 40959. 484 o REDIRECT_SUPPORTED 485 o REDIRECT 486 o REDIRECTED_FROM 488 11. Acknowledgements 490 The use of anycast address with IKEv2 was first described in [7]. It 491 was then added to an early draft version of RFC 5026 and later 492 removed before the RFC was published. Therefore the authors of [7] 493 and RFC 5026 are acknowledged. 495 Thanks to Pasi Eronen, with whom the solution described in this 496 document was extensively discussed. Thanks to Tero Kivinen for 497 suggesting the use of REDIRECTED_FROM payload and other comments 498 which helped improve the document. The authors would also like to 499 thank Yaron Sheffer, Sunil Kumar, Fan Zhao, Yoav Nir, Richard 500 Graveman, Kanagavel Rajan, Srini Addepalli, and Arnaud Ebalard for 501 their reviews and comments. 503 12. References 505 12.1. Normative References 507 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 508 Levels", BCP 14, RFC 2119, March 1997. 510 [2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, 511 December 2005. 513 12.2. Informative References 515 [3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in 516 IPv6", RFC 3775, June 2004. 518 [4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 519 Bootstrapping in Split Scenario", RFC 5026, October 2007. 521 [5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility 522 Header Home Agent Switch Message", RFC 5142, January 2008. 524 [6] Eronen, P. and J. Korhonen, "Multiple Authentication Exchanges 525 in the Internet Key Exchange (IKEv2) Protocol", RFC 4739, 526 November 2006. 528 [7] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in 529 Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02 530 (work in progress), January 2007. 532 Authors' Addresses 534 Vijay Devarapalli 535 WiChorus 536 3590 North First St 537 San Jose, CA 95134 538 USA 540 Email: vijay@wichorus.com 542 Kilian Weniger 544 Email: kilian.weniger@googlemail.com