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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 14, 2008) is 5764 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) ** 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 (~~), 1 warning (==), 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: January 15, 2009 Panasonic 6 P. Eronen 7 Nokia 8 July 14, 2008 10 Re-direct Mechanism for IKEv2 11 draft-devarapalli-ipsec-ikev2-redirect-02.txt 13 Status of this Memo 15 By submitting this Internet-Draft, each author represents that any 16 applicable patent or other IPR claims of which he or she is aware 17 have been or will be disclosed, and any of which he or she becomes 18 aware will be disclosed, in accordance with Section 6 of BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt. 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 This Internet-Draft will expire on January 15, 2009. 38 Abstract 40 IKEv2 is a popular protocol for setting up VPN tunnels from a remote 41 location to a gateway so that the VPN client can access services in 42 the network behind the gateway. Currently there is no standard 43 mechanism specified that allows an overloaded VPN gateway to re- 44 direct the VPN client to attach to another gateway. This document 45 proposes a re-direct mechanism for IKEv2. The proposed mechanism can 46 also be used for Mobile IPv6 to enable the home agent to re-direct 47 the mobile node to another home agent. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 3. IKEv2 Exchange with Redirect . . . . . . . . . . . . . . . . . 4 54 4. Use of Anycast Addresses with the Re-direct Mechanism . . . . 5 55 5. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 6 56 5.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 6 57 5.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 7 58 5.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 7 59 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 60 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 61 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 62 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 63 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 64 9.2. Informative References . . . . . . . . . . . . . . . . . . 9 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 66 Intellectual Property and Copyright Statements . . . . . . . . . . 11 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 is created on the home agent. 112 2. Terminology 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in [1]. 118 3. IKEv2 Exchange with Redirect 120 To redirect a IKEv2 session to another VPN gateway, the VPN gateway 121 that initially received the IKE_SA_INIT request selects another VPN 122 gateway and responds to the VPN client with a REDIRECT Notification 123 payload. The mechanism by which the initial VPN gateway selects 124 another VPN gateway is out of scope for this document. The IP 125 address of the selected VPN gateway is sent in the REDIRECT payload. 127 The VPN client indicates support for the IKEv2 redirect mechanism by 128 including a REDIRECT_SUPPORTED notification message in the initial 129 IKE_SA_INIT request. If the IKE_SA_INIT request did not include the 130 REDIRECT_SUPPORTED payload, the responder MUST NOT send the REDIRECT 131 payload to the VPN client. 133 Initiator Responder (initial VPN GW) 134 --------- ------------------------- 136 (IP_I:500 -> Initial_IP_R:500) 137 HDR(A,0), SAi1, KEi, Ni, --> 138 N(REDIRECT_SUPPORTED) 140 (Initial_IP_R:500 -> IP_I:500) 141 <-- HDR(A,0), N(REDIRECT, IP_R) 143 When the VPN client receives the IKE_SA_INIT response with the 144 REDIRECT payload, it initiates a new IKE_SA_INIT exchange with the 145 VPN gateway listed in the REDIRECT payload. The VPN client includes 146 the IP address of the original VPN gateway that re-directed the 147 client. The IKEv2 exchange then proceeds as normal with the selected 148 VPN gateway. 150 Initiator Responder (Selected VPN GW) 151 --------- --------------------------- 153 (IP_I:500 -> IP_R:500) 154 HDR(A,0), SAi1, KEi, Ni, --> 155 N(REDIRECTED_FROM, Initial_IP_R) 157 (IP_R:500 -> IP_I:500) 158 <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] 160 (IP_I:500 -> IP_R:500) 161 HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] 162 [IDr,]AUTH, SAi2, TSi, TSr} --> 164 (IP_R:500 -> IP_I:500) 165 <-- HDR(A,B), SK {IDr, [CERT,] AUTH, 166 SAr2, TSi, TSr} 168 When this mechanism is used with Mobile IPv6, a mobile node's 169 security associations with its home agent may expire while it still 170 has a valid binding cache entry at the home agent. In this case, the 171 mobile node MUST NOT use the original home agent address as the 172 destination address in the IKE_SA_INIT exchange to setup new security 173 associations. It MUST try to setup security associations with its 174 existing home agent. 176 4. Use of Anycast Addresses with the Re-direct Mechanism 178 The use of anycast addresses will avoid having to configure a 179 particular VPN gateway's IP address in the DNS. Instead, the anycast 180 address that represents the group of VPN gateways is stored in the 181 DNS. When the VPN client performs a DNS lookup for the VPN gateway, 182 it receives the anycast address of the VPN gateway in the DNS 183 response. 185 If an anycast address is returned in response to DNS resolution of an 186 FQDN, the IKEv2 transaction between the VPN client and the VPN 187 gateway is slightly modified. The VPN client sends the IKE_SA_INIT 188 request to the anycast address. The IKE_SA_INIT request is routed to 189 one of the VPN gateways that is part of the anycast group. The VPN 190 gateway that receives the IKE_SA_INIT request responds with an 191 IKE_SA_INIT reply from the anycast address. 193 Initiator Responder (any VPN GW) 194 --------- ------------------------- 196 (IP_I:500 -> ANYCAST:500) 197 HDR(A,0), SAi1, KEi, Ni) --> 198 N(REDIRECT_SUPPORTED) 200 (ANYCAST:500 -> IP_I:500) 201 <-- HDR(A,0), N(REDIRECT, IP_R) 203 If the destination address on the IKE_SA_INIT request is an anycast 204 address, the VPN gateway that received the IKE_SA_INIT request MUST 205 include the REDIRECT payload to re-direct the VPN client to a unicast 206 address of one of the VPN gateway. The VPN gateway that received the 207 IKE_SA_INIT request MAY re-direct the client to its own unicast 208 address, if it is not overloaded. 210 The rest of the IKEv2 exchange is the same as described in Section 3. 212 5. Redirect Messages 214 5.1. REDIRECT_SUPPORTED 216 The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT 217 request by the initiator to indicate support for the IKEv2 re-direct 218 mechanism described in this document. 220 1 2 3 221 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 1 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | Next Payload |C| RESERVED | Payload Length | 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | Protocol ID | SPI Size (=0) | Notify Message Type | 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 228 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 229 the 'Notify Message Type' fields are the same as described in Section 230 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to 231 indicate that the SPI is not present in this message. 233 The 'Payload Length' field MUST be set to '8'. The 'Notify Message 234 Type' field is set to indicate the REDIRECT_SUPPORTED payload . 237 5.2. REDIRECT 239 The REDIRECT payload is included in an IKE_SA_INIT response from the 240 responder when the responder wants to re-direct the initiator to 241 another VPN gateway. The message includes the new responder's IP 242 address. 244 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | Next Payload |C| RESERVED | Payload Length | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Protocol ID | SPI Size (=0) | Notify Message Type | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | GW Ident Type | | 252 +---------------+ ~ 253 ~ New Responder GW Identity ~ 254 | | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 258 the 'Notify Message Type' fields are the same as described in Section 259 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to 260 indicate that the SPI is not present in this message. 262 The 'Payload Length' field MUST be set to either '13' or '25' 263 depending on whether an IPv4 or IPv6 address of the new VPN gateway 264 is sent in the message. The 'Notify Message Type' field is set to 265 indicate the REDIRECT payload . The 266 'GW Identity Type' field indicates the type of information that is 267 sent to identify the new VPN gateway. The following values are 268 reserved by this document. 270 1 - IPv4 address of the new VPN gateway 271 2 - IPv6 address of the new VPN gateway 272 3 - FQDN of the new VPN gateway 274 All other values for this field are reserved and MUST NOT be used. 275 The identity of the new VPN gateway is carried in the 'New Responder 276 GW Identity' field. 278 5.3. REDIRECTED_FROM 280 The REDIRECTED_FROM message type is included in the IKE_SA_INIT 281 request from the initiator to the new VPN gateway to indicate the IP 282 address of the original VPN gateway that re-directed the initiator. 283 The original VPN gateway's IP address is included in the message. 285 1 2 3 286 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 1 287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 288 | Next Payload |C| RESERVED | Payload Length | 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | Protocol ID | SPI Size (=0) | Notify Message Type | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | GW Ident Type | | 293 +---------------+ ~ 294 ~ Original Responder GW Identity ~ 295 | | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and 299 the 'Notify Message Type' fields are the same as described in Section 300 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to 301 indicate that the SPI is not present in this message. 303 The 'Payload Length' field MUST be set to either '13' or '25' 304 depending on whether an IPv4 or IPv6 address of the original VPN 305 gateway is sent in the message. The 'Notify Message Type' field is 306 set to indicate the REDIRECTED_FROM payload . The 'GW Identity Type' field indicates the type of 308 information that is sent to identify the new VPN gateway. The 309 following values are reserved by this document. 311 1 - IPv4 address of the original VPN gateway 312 2 - IPv6 address of the original VPN gateway 314 All other values for this field are reserved and MUST NOT be used. 315 The identity of the original VPN gateway is carried in the 'Original 316 Responder GW Identity' field. 318 6. Security Considerations 320 An eavesdropper on the path between VPN client and server may send a 321 redirect to the client upon receiving an IKE_SA_INIT message from 322 this client. This is no problem regarding DoS attacks for the VPN 323 connection, since an on-path-attacker can as well drop the 324 IKE_SA_INIT requests to prevent VPN access for the client. But an 325 eavesdropper on the path between VPN client and server can redirect a 326 large number of clients to a victim, which is then flooded with 327 IKE_SA_INIT requests. Flooding only happens if many clients initiate 328 IKEv2 exchange at almost the same time, which is considered a rare 329 event. However, this may happen if a Home Agent/VPN server is 330 shutdown for maintenance and all clients need to re-establish VPN 331 connections with another Home Agent/VPN server or if the on-path 332 attacker forces all IPsec security associations to expire by dropping 333 all received IKEv2 messages. 335 The use of REDIRECTED_FROM payload is intended to discourage a rogue 336 VPN gateway from re-directing a large number of VPN clients to a 337 particular VPN gateway. It does not prevent such a DoS attack. 339 7. IANA Considerations 341 This document defines three new IKEv2 Notification Message types as 342 described in Section 5. The three Notify Message Types must be 343 assigned values between 16396 and 40959. 345 o REDIRECT_SUPPORTED 346 o REDIRECT 347 o REDIRECTED_FROM 349 8. Acknowledgements 351 The use of anycast address with IKEv2 was first described in [6]. It 352 was then added to an early draft version of RFC 5026 and later 353 removed before the RFC was published. Therefore the authors of [6] 354 and RFC 5026 are acknowledged. 356 Thanks to Tero Kivinen for suggesting the use of REDIRECTED_FROM 357 payload. The authors would also like to thank Yaron Sheffer and 358 Arnaud Ebalard for their reviews and comments. 360 9. References 362 9.1. Normative References 364 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 365 Levels", BCP 14, RFC 2119, March 1997. 367 [2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, 368 December 2005. 370 9.2. Informative References 372 [3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in 373 IPv6", RFC 3775, June 2004. 375 [4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 376 Bootstrapping in Split Scenario", RFC 5026, October 2007. 378 [5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility 379 Header Home Agent Switch Message", RFC 5142, January 2008. 381 [6] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in 382 Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02 383 (work in progress), January 2007. 385 Authors' Addresses 387 Vijay Devarapalli 388 WiChorus 389 3590 North First St 390 San Jose, CA 95134 391 USA 393 Email: vijay@wichorus.com 395 Killian Weniger 396 Panasonic R&D Center Germany 397 Monzastr. 4c 398 Langen 63225 399 Germany 401 Email: kilian.weniger@eu.panasonic.com 403 Pasi Eronen 404 Nokia 405 P.O. 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