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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (November 3, 2008) is 5652 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-11) exists of draft-ietf-ipsecme-ikev2bis-01 -- Obsolete informational reference (is this intentional?): RFC 3775 (ref. '3') (Obsoleted by RFC 6275) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 8 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: May 7, 2009 Panasonic 6 November 3, 2008 8 Re-direct Mechanism for IKEv2 9 draft-ietf-ipsecme-ikev2-redirect-01.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 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 May 7, 2009. 36 Abstract 38 IKEv2 is a popular protocol for setting up VPN tunnels from a remote 39 location to a gateway so that the VPN client can access services in 40 the network behind the gateway. Currently there is no standard 41 mechanism specified that allows an overloaded VPN gateway to re- 42 direct the VPN client to attach to another gateway. This document 43 proposes a re-direct mechanism for IKEv2. The proposed mechanism can 44 also be used for Mobile IPv6 to enable the home agent to re-direct 45 the mobile node to another home agent. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 50 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 51 3. IKEv2 Exchange with Redirect . . . . . . . . . . . . . . . . . 4 52 4. Use of Anycast Addresses with the Re-direct Mechanism . . . . 5 53 5. Gateway Initiated Redirect . . . . . . . . . . . . . . . . . . 6 54 6. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 7 55 6.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 7 56 6.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 7 57 6.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 8 58 6.4. REDIRECT_ACK . . . . . . . . . . . . . . . . . . . . . . . 9 59 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 60 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 61 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 62 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 63 10.1. Normative References . . . . . . . . . . . . . . . . . . . 10 64 10.2. Informative References . . . . . . . . . . . . . . . . . . 11 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 66 Intellectual Property and Copyright Statements . . . . . . . . . . 12 68 1. Introduction 70 IKEv2 [2] is widely used for setting up IPsec-based VPNs. The IP 71 address of the VPN gateway can be configured on the VPN client. But 72 this does not scale well, when the number of VPN gateways is large. 73 Dynamic discovery of VPN gateways using DNS is quite widely used too. 74 However, using DNS is not flexible when it comes to assigning a VPN 75 gateway to the VPN client based on the load on the VPN gateways. The 76 VPN client typically tries to connect to the IP address of the VPN 77 gateways that appears first in the DNS response. If the VPN tunnel 78 setup fails, then the VPN client tries to attach to the other VPN 79 gateways returned in the DNS response. 81 This document proposes a re-direct mechanism for IKEv2 that enables a 82 VPN gateway to re-direct the VPN client to another VPN gateway, for 83 example, based on the load condition. The re-direct is done during 84 the IKE_SA_INIT exchange. The re-direct mechanism can also be used 85 in conjunction with anycast addresses. In this case, anycast address 86 for the cluster of VPN gateways is stored in the DNS instead of a 87 list of unicast IP addresses of the VPN gateways. 89 The re-direct can also happen because of administrative or optimal 90 routing reasons. This document does not attempt to provide an 91 exhaustive list of reasons for re-directing a VPN client to another 92 VPN gateway. 94 Mobile IPv6 [3] may use IKEv2 for mutual authentication between the 95 mobile node and the home agent. IKEv2 may also be used for home 96 address configuration and setting up IPsec security associations for 97 protecting Mobile IPv6 signaling messages [4]. The IKEv2 exchange 98 precedes the exchange of Mobile IPv6 signaling messages. Therefore 99 the mechanism described in this document can be also be used by a 100 Mobile IPv6 home agent to re-direct a mobile node to another home 101 agent. 103 There is a Home Agent Switch mechanism available for re-directing a 104 mobile node to another home agent, described in [5]. The Home Agent 105 Switch mechanism can only be used after the binding cache had been 106 created at the home agent for the mobile node. The disadvantage with 107 this is that quite a bit of state is created on the home agent before 108 the mobile node can be re-directed to another home agent. The 109 mechanism described in this document can be used for re-directing a 110 mobile node before any state related to the Mobile IPv6 binding is 111 created on the home agent. 113 2. Terminology 115 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 116 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 117 document are to be interpreted as described in [1]. 119 3. IKEv2 Exchange with Redirect 121 To redirect a IKEv2 session to another VPN gateway, the VPN gateway 122 that initially received the IKE_SA_INIT request selects another VPN 123 gateway and responds to the VPN client with a REDIRECT Notification 124 payload. The mechanism by which the initial VPN gateway selects 125 another VPN gateway is out of scope for this document. The IP 126 address of the selected VPN gateway is sent in the REDIRECT payload. 128 The VPN client indicates support for the IKEv2 redirect mechanism by 129 including a REDIRECT_SUPPORTED notification message in the initial 130 IKE_SA_INIT request. If the IKE_SA_INIT request did not include the 131 REDIRECT_SUPPORTED payload, the responder MUST NOT send the REDIRECT 132 payload to the VPN client. 134 Initiator Responder (initial VPN GW) 135 --------- ------------------------- 137 (IP_I:500 -> Initial_IP_R:500) 138 HDR(A,0), SAi1, KEi, Ni, --> 139 N(REDIRECT_SUPPORTED) 141 (Initial_IP_R:500 -> IP_I:500) 142 <-- HDR(A,0), N(REDIRECT, IP_R) 144 When the VPN client receives the IKE_SA_INIT response with the 145 REDIRECT payload, it initiates a new IKE_SA_INIT exchange with the 146 VPN gateway listed in the REDIRECT payload. The VPN client includes 147 the IP address of the original VPN gateway that re-directed the 148 client. The IKEv2 exchange then proceeds as normal with the selected 149 VPN gateway. 151 Initiator Responder (Selected VPN GW) 152 --------- --------------------------- 154 (IP_I:500 -> IP_R:500) 155 HDR(A,0), SAi1, KEi, Ni, --> 156 N(REDIRECTED_FROM, Initial_IP_R) 158 (IP_R:500 -> IP_I:500) 159 <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] 161 (IP_I:500 -> IP_R:500) 162 HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] 163 [IDr,]AUTH, SAi2, TSi, TSr} --> 165 (IP_R:500 -> IP_I:500) 166 <-- HDR(A,B), SK {IDr, [CERT,] AUTH, 167 SAr2, TSi, TSr} 169 When this mechanism is used with Mobile IPv6, a mobile node's 170 security associations with its home agent may expire while it still 171 has a valid binding cache entry at the home agent. In this case, the 172 mobile node MUST NOT use the original home agent address as the 173 destination address in the IKE_SA_INIT exchange to setup new security 174 associations. It MUST try to setup security associations with its 175 existing home agent. 177 4. Use of Anycast Addresses with the Re-direct Mechanism 179 The use of anycast addresses will avoid having to configure a 180 particular VPN gateway's IP address in the DNS. Instead, the anycast 181 address that represents the group of VPN gateways is stored in the 182 DNS. When the VPN client performs a DNS lookup for the VPN gateway, 183 it receives the anycast address of the VPN gateway in the DNS 184 response. 186 If an anycast address is returned in response to DNS resolution of an 187 FQDN, the IKEv2 transaction between the VPN client and the VPN 188 gateway is slightly modified. The VPN client sends the IKE_SA_INIT 189 request to the anycast address. The IKE_SA_INIT request is routed to 190 one of the VPN gateways that is part of the anycast group. The VPN 191 gateway that receives the IKE_SA_INIT request responds with an 192 IKE_SA_INIT reply from the anycast address. 194 Initiator Responder (any VPN GW) 195 --------- ------------------------- 197 (IP_I:500 -> ANYCAST:500) 198 HDR(A,0), SAi1, KEi, Ni) --> 199 N(REDIRECT_SUPPORTED) 201 (ANYCAST:500 -> IP_I:500) 202 <-- HDR(A,0), N(REDIRECT, IP_R) 204 If the destination address on the IKE_SA_INIT request is an anycast 205 address, the VPN gateway that received the IKE_SA_INIT request MUST 206 include the REDIRECT payload to re-direct the VPN client to a unicast 207 address of one of the VPN gateway. The VPN gateway that received the 208 IKE_SA_INIT request MAY re-direct the client to its own unicast 209 address, if it is not overloaded. 211 The rest of the IKEv2 exchange is the same as described in Section 3. 213 5. Gateway Initiated Redirect 215 The re-direct mechanism may also be used by a VPN gateway to re- 216 direct the client to another VPN gateway in middle of a session. To 217 re-direct a client, the gateway should send an INFORMATIONAL message 218 with the REDIRECT Notify payload. The REDIRECT payload MUST carry 219 information about the new VPN gateway. When the client receives this 220 message, it MUST send an INFORMATIONAL message with the REDIRECT_ACK 221 Notify payload. Until the client responds with an INFORMATIONAL 222 message with the REDIRECT_ACK payload, the gateway SHOULD re-transmit 223 the re-direct INFORMATIONAL message as described in [2]. The 224 following illustrates the INFORMATIONAL message exchange for gateway- 225 initiated redirect. 227 Initiator (VPN client) Responder (VPN GW) 228 ---------------------- ------------------ 230 <-- HDR, SK {[REDIRECT]} 232 HDR, SK {[REDIRECT_ACK]} --> 234 The INFORMATIONAL message exchange described above is protected by 235 the existing IKEv2 SA between the client and the gateway. 237 6. Redirect Messages 239 6.1. REDIRECT_SUPPORTED 241 The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT 242 request by the initiator to indicate support for the IKEv2 re-direct 243 mechanism described in this document. 245 1 2 3 246 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 1 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | Next Payload |C| RESERVED | Payload Length | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Protocol ID | SPI Size (=0) | Notify Message Type | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 254 the 'Notify Message Type' fields are the same as described in Section 255 3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 256 the SPI is not present in this message. 258 The 'Payload Length' field MUST be set to '8'. The 'Notify Message 259 Type' field is set to indicate the REDIRECT_SUPPORTED payload . 262 6.2. REDIRECT 264 The REDIRECT payload is included in an IKE_SA_INIT response from the 265 responder when the responder wants to re-direct the initiator to 266 another VPN gateway. The message includes the new responder's IP 267 address. 269 1 2 3 270 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 1 271 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 272 | Next Payload |C| RESERVED | Payload Length | 273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 | Protocol ID | SPI Size (=0) | Notify Message Type | 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | GW Ident Type | | 277 +---------------+ ~ 278 ~ New Responder GW Identity ~ 279 | | 280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 282 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 283 the 'Notify Message Type' fields are the same as described in Section 284 3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 285 the SPI is not present in this message. 287 If the IP address of the new VPN gateway is sent, the 'Payload 288 Length' field MUST be set to either '13' or '25' depending on whether 289 an IPv4 or IPv6 address is sent in the message. If the FQDN of the 290 new VPN gateway is sent, the 'Payload Length' field is set to the 291 length of the FQDN plus the fixed fields in the message. The 'Notify 292 Message Type' field is set to indicate the REDIRECT payload . The 'GW Identity Type' field indicates the 294 type of information that is sent to identify the new VPN gateway. 295 The following values are reserved by this document. 297 1 - IPv4 address of the new VPN gateway 298 2 - IPv6 address of the new VPN gateway 299 3 - FQDN of the new VPN gateway 301 All other values for this field are reserved and MUST NOT be used. 302 The identity of the new VPN gateway is carried in the 'New Responder 303 GW Identity' field. 305 6.3. REDIRECTED_FROM 307 The REDIRECTED_FROM message type is included in the IKE_SA_INIT 308 request from the initiator to the new VPN gateway to indicate the IP 309 address of the original VPN gateway that re-directed the initiator. 310 The original VPN gateway's IP address is included in the message. 312 1 2 3 313 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 1 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 | Next Payload |C| RESERVED | Payload Length | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 317 | Protocol ID | SPI Size (=0) | Notify Message Type | 318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 319 | GW Ident Type | | 320 +---------------+ ~ 321 ~ Original Responder GW Identity ~ 322 | | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 326 the 'Notify Message Type' fields are the same as described in Section 327 3.10 of [2] The 'SPI Size' field MUST be set to 0 to indicate that 328 the SPI is not present in this message. 330 The 'Payload Length' field MUST be set to either '13' or '25' 331 depending on whether an IPv4 or IPv6 address of the original VPN 332 gateway is sent in the message. The 'Notify Message Type' field is 333 set to indicate the REDIRECTED_FROM payload . The 'GW Identity Type' field indicates the type of 335 information that is sent to identify the new VPN gateway. The 336 following values are reserved by this document. 338 1 - IPv4 address of the original VPN gateway 339 2 - IPv6 address of the original VPN gateway 341 All other values for this field are reserved and MUST NOT be used. 342 The identity of the original VPN gateway is carried in the 'Original 343 Responder GW Identity' field. 345 6.4. REDIRECT_ACK 347 The REDIRECT_ACK payload is included in the INFORMATIONAL message 348 sent by the VPN client to the gateway in response to a gateway 349 initiated redirect message as described in Section 5. 351 1 2 3 352 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 1 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 354 | Next Payload |C| RESERVED | Payload Length | 355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 356 | Protocol ID | SPI Size (=0) | Notify Message Type | 357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 359 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 360 the 'Notify Message Type' fields are the same as described in Section 361 3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 362 the SPI is not present in this message. 364 The 'Payload Length' field MUST be set to '8'. The 'Notify Message 365 Type' field is set to indicate the REDIRECT_ACK payload . 368 7. Security Considerations 370 An eavesdropper on the path between VPN client and server may send a 371 redirect to the client upon receiving an IKE_SA_INIT message from 372 this client. This is no problem regarding DoS attacks for the VPN 373 connection, since an on-path-attacker can as well drop the 374 IKE_SA_INIT requests to prevent VPN access for the client. But an 375 eavesdropper on the path between VPN client and server can redirect a 376 large number of clients to a victim, which is then flooded with 377 IKE_SA_INIT requests. Flooding only happens if many clients initiate 378 IKEv2 exchange at almost the same time, which is considered a rare 379 event. However, this may happen if a Home Agent/VPN server is 380 shutdown for maintenance and all clients need to re-establish VPN 381 connections with another Home Agent/VPN server or if the on-path 382 attacker forces all IPsec security associations to expire by dropping 383 all received IKEv2 messages. 385 The use of REDIRECTED_FROM payload is intended to discourage a rogue 386 VPN gateway from re-directing a large number of VPN clients to a 387 particular VPN gateway. It does not prevent such a DoS attack. 389 8. IANA Considerations 391 This document defines four new IKEv2 Notification Message types as 392 described in Section 6. The four Notify Message Types must be 393 assigned values between 16396 and 40959. 395 o REDIRECT_SUPPORTED 396 o REDIRECT 397 o REDIRECTED_FROM 398 o REDIRECT_ACK 400 9. Acknowledgements 402 The use of anycast address with IKEv2 was first described in [6]. It 403 was then added to an early draft version of RFC 5026 and later 404 removed before the RFC was published. Therefore the authors of [6] 405 and RFC 5026 are acknowledged. 407 Thanks to Pasi Eronen, with who, the solution described in this 408 document was extensively discussed. Thanks to Tero Kivinen for 409 suggesting the use of REDIRECTED_FROM payload. The authors would 410 also like to thank Yaron Sheffer, Sunil Kumar and Arnaud Ebalard for 411 their reviews and comments. 413 10. References 415 10.1. Normative References 417 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 418 Levels", BCP 14, RFC 2119, March 1997. 420 [2] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key 421 Exchange Protocol: IKEv2", draft-ietf-ipsecme-ikev2bis-01 (work 422 in progress), October 2008. 424 10.2. Informative References 426 [3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in 427 IPv6", RFC 3775, June 2004. 429 [4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 430 Bootstrapping in Split Scenario", RFC 5026, October 2007. 432 [5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility 433 Header Home Agent Switch Message", RFC 5142, January 2008. 435 [6] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in 436 Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02 437 (work in progress), January 2007. 439 Authors' Addresses 441 Vijay Devarapalli 442 WiChorus 443 3590 North First St 444 San Jose, CA 95134 445 USA 447 Email: vijay@wichorus.com 449 Killian Weniger 450 Panasonic R&D Center Germany 451 Monzastr. 4c 452 Langen 63225 453 Germany 455 Email: kilian.weniger@eu.panasonic.com 457 Full Copyright Statement 459 Copyright (C) The IETF Trust (2008). 461 This document is subject to the rights, licenses and restrictions 462 contained in BCP 78, and except as set forth therein, the authors 463 retain all their rights. 465 This document and the information contained herein are provided on an 466 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 467 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 468 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 469 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 470 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 471 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 473 Intellectual Property 475 The IETF takes no position regarding the validity or scope of any 476 Intellectual Property Rights or other rights that might be claimed to 477 pertain to the implementation or use of the technology described in 478 this document or the extent to which any license under such rights 479 might or might not be available; nor does it represent that it has 480 made any independent effort to identify any such rights. 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