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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NETLMM Working Group R. Wakikawa 3 Internet-Draft Toyota ITC 4 Intended status: Standards Track S. Gundavelli 5 Expires: October 10, 2009 Cisco 6 April 08, 2009 8 IPv4 Support for Proxy Mobile IPv6 9 draft-ietf-netlmm-pmip6-ipv4-support-11.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on October 10, 2009. 34 Copyright Notice 36 Copyright (c) 2009 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 This document specifies extensions to Proxy Mobile IPv6 protocol for 48 adding IPv4 protocol support. The scope of IPv4 protocol support is 49 two-fold: 1) enable IPv4 home address mobility support to the mobile 50 node. 2) allowing the mobility entities in the Proxy Mobile IPv6 51 domain to exchange signaling messages over an IPv4 transport network. 53 Table of Contents 55 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 56 1.1. Stated Assumptions . . . . . . . . . . . . . . . . . . . . 6 57 1.2. Relevance to Dual-Stack Mobile IPv6 . . . . . . . . . . . 7 59 2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 9 60 2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 9 61 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 9 63 3. IPv4 Home Address Mobility Support . . . . . . . . . . . . . . 11 64 3.1. Local Mobility Anchor Considerations . . . . . . . . . . . 12 65 3.1.1. Extensions to Binding Cache Entry . . . . . . . . . . 12 66 3.1.2. Signaling Considerations . . . . . . . . . . . . . . . 12 67 3.1.3. Routing Considerations for the Local Mobility 68 Anchor . . . . . . . . . . . . . . . . . . . . . . . . 18 69 3.2. Mobile Access Gateway Considerations . . . . . . . . . . . 19 70 3.2.1. Extensions to Binding Update List Entry . . . . . . . 19 71 3.2.2. Extensions to Mobile Node's Policy Profile . . . . . . 19 72 3.2.3. Signaling Considerations . . . . . . . . . . . . . . . 19 73 3.2.4. Routing Considerations for the Mobile Access 74 Gateway . . . . . . . . . . . . . . . . . . . . . . . 23 75 3.3. Mobility Options and Status Codes . . . . . . . . . . . . 24 76 3.3.1. IPv4 Default-Router Address Option . . . . . . . . . . 24 77 3.3.2. IPv4 DHCP Support Mode . . . . . . . . . . . . . . . . 25 78 3.3.3. Status Codes . . . . . . . . . . . . . . . . . . . . . 26 79 3.4. Supporting DHCP-Based Address Configuration . . . . . . . 26 80 3.4.1. DHCP Server co-located with the Mobile Access 81 Gateway . . . . . . . . . . . . . . . . . . . . . . . 28 82 3.4.2. DHCP Relay Agent co-located with the Mobile Access 83 Gateway . . . . . . . . . . . . . . . . . . . . . . . 30 85 4. IPv4 Transport Support . . . . . . . . . . . . . . . . . . . . 34 86 4.1. Local Mobility Anchor Considerations . . . . . . . . . . . 35 87 4.1.1. Extensions to Binding Cache Entry . . . . . . . . . . 35 88 4.1.2. Extensions to Mobile Node's Policy Profile . . . . . . 36 89 4.1.3. Signaling Considerations . . . . . . . . . . . . . . . 36 90 4.1.4. Routing Considerations . . . . . . . . . . . . . . . . 39 91 4.2. Mobile Access Gateway Considerations . . . . . . . . . . . 40 92 4.2.1. Extensions to Binding Update List Entry . . . . . . . 40 93 4.2.2. Signaling Considerations . . . . . . . . . . . . . . . 41 95 5. Protocol Configuration Variables . . . . . . . . . . . . . . . 44 96 5.1. Local Mobility Anchor - Configuration Variables . . . . . 44 97 5.2. Mobile Access Gateway - Configuration Variables . . . . . 44 99 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 100 7. Security Considerations . . . . . . . . . . . . . . . . . . . 47 102 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 48 104 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48 106 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48 107 10.1. Normative References . . . . . . . . . . . . . . . . . . . 48 108 10.2. Informative References . . . . . . . . . . . . . . . . . . 49 110 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 50 112 1. Overview 114 The transition from IPv4 to IPv6 is a long process and during this 115 period of transition, both the protocols will be enabled over the 116 same network infrastructure. Thus, it is reasonable to assume that a 117 mobile node in a Proxy Mobile IPv6 domain may operate in an IPv4-only 118 IPv6-only or in dual-stack mode and additionally the network between 119 the mobile access gateway and a local mobility anchor may be an IPv4 120 or an IPv6 network. It is also reasonable to expect the same 121 mobility infrastructure in the Proxy Mobile IPv6 domain to provide 122 mobility to the mobile nodes operating in IPv4, IPv6 or in dual mode 123 and when the network between the local mobility anchor and the mobile 124 access gateway is an IPv4 or an IPv6 network. The motivation and 125 scope of IPv4 support in Mobile IPv6 is summarized in [RFC-4977] and 126 all those requirements apply to Proxy Mobile IPv6 protocol as well. 128 The Proxy Mobile IPv6 protocol [RFC-5213] specifies a mechanism for 129 providing IPv6 home address mobility support to a mobile node in a 130 Proxy Mobile IPv6 domain. The protocol requires IPv6 transport 131 network between the mobility entities. The extensions defined in 132 this document extends IPv4 support to the Proxy Mobile IPv6 protocol 133 [RFC-5213]. 135 The scope of IPv4 support in Proxy Mobile IPv6 includes the support 136 for the following two features: 138 o IPv4 Home Address Mobility Support: A mobile node that has an IPv4 139 stack enabled will be able to obtain an IPv4 address and be able 140 to use that address from any of the access networks in that Proxy 141 Mobile IPv6 domain. The mobile node is not required to be 142 allocated or assigned an IPv6 address for enabling IPv4 home 143 address support. 145 o IPv4 Transport Network Support: The mobility entities in the Proxy 146 Mobile IPv6 domain will be able to exchange Proxy Mobile IPv6 147 signaling messages over an IPv4 transport and furthermore the 148 mobile access gateway may be using an IPv4 private address and 149 with NAT [RFC-3022] translation devices on the path to the local 150 mobility anchor. 152 These two features, the IPv4 Home Address Mobility support and the 153 IPv4 transport support features, are independent of each other and 154 deployments may choose to enable any one or both of these features as 155 required. 157 +----+ +----+ 158 |LMA1| |LMA2| 159 +----+ +----+ 160 IPv4-LMAA1 -> | | <-- LMAA2 161 | | 162 \\ //\\ 163 (NAT) // \\ 164 \\ // \\ 165 +---\\------------- //------\\----+ 166 ( \\ IPv4/IPv6 // \\ ) 167 ( \\ Network // \\ ) 168 +------\\--------//------------\\-+ 169 \\ // \\ 170 \\ // \\ 171 \\ // \\ 172 IPv4-Proxy-CoA1--> | | <-- Proxy-CoA2 173 +----+ +----+ 174 |MAG1|-----{MN2} |MAG2| 175 +----+ | +----+ 176 (IPv6 MN-HoA1) | | | <-- (IPv6 MN-HoA2) 177 (IPv4-MN-HoA1) --> | (IPv4-MN-HoA2) | <-- (IPv4-MN-HoA3) 178 {MN1} {MN3} 180 Figure 1: IPv4 support for Proxy Mobile IPv6 182 1.1. Stated Assumptions 184 The following are the configuration requirements from the mobility 185 entities in the Proxy Mobile IPv6 domain for supporting the 186 extensions defined in this document. 188 o The local mobility anchor and the mobile access gateway are both 189 IPv4 and IPv6 enabled. Irrespective of the type of transport 190 network (IPv4 or IPv6) separating these two entities, the mobility 191 signaling is always based on Proxy Mobile IPv6 [RFC-5213]. 193 o The local mobility anchor and the mobile access gateway MUST be 194 configured with IPv6 globally unique addresses, even when they are 195 in IPv4-only network. These addresses can be of the type Unique 196 Local IPv6 Unicast Address [RFC-4193], IPv6 Global Unicast Address 197 [RFC-3587] or IPv4-mapped IPv6 address [RFC-4291]. When using 198 IPv4 transport, it is not required that there is IPv6 routing 199 enabled between the local mobility anchor and the mobile access 200 gateway. However, they must be able to receive any IPv6 packets 201 sent to the configured IPv6 addresses, after removing the outer 202 IPv4 encapsulation header. 204 o The mobile node can be operating in IPv4-only, IPv6-only or in 205 dual mode. Based on what is enabled for a mobile node, it should 206 be able to obtain IPv4-only, IPv6-only or both IPv4 and IPv6 207 address(es) for its interface and furthermore achieve mobility 208 support for those addresses. 210 o For enabling IPv4 home address mobility support to a mobile node, 211 it is not required that the IPv6 home address mobility support 212 needs to enabled. However, the respective protocol(s) support, 213 such as IPv4 or IPv6 packet forwarding, must be enabled on the 214 access link between the mobile node and the mobile access gateway. 216 o The mobile node can obtain an IPv4 address for its attached 217 interface. Based on the type of link, it may be able to acquire 218 its IPv4 address configuration using standard IPv4 address 219 configuration mechanisms such as DHCP [RFC-2131], IPCP [RFC-1332], 220 IKEv2 [RFC-4306] or static address configuration. 222 o The mobile node's IPv4 home subnet is typically a shared address 223 space. It is not for the exclusive use of any one mobile node. 224 There can be multiple mobile nodes that are assigned IPv4 225 addresses from the same subnet. 227 o The mobile access gateway is the IPv4 default-router for the 228 mobile node on its access link. It will be in the forwarding path 229 for the mobile node's data traffic. Additionally, as specified in 230 section 6.9.3 of [RFC-5213], all the mobile access gateways in the 231 Proxy Mobile IPv6 domain MUST use the same link-layer address on 232 any of the access links wherever the mobile node attaches. 234 1.2. Relevance to Dual-Stack Mobile IPv6 236 IPv4 support for Mobile IPv6 is specified in Dual-Stack Mobile IPv6 237 specification [ID-DSMIP6]. This document to most part leverages the 238 approaches, messaging options and processing logic defined in that 239 document for extending IPv4 support to Proxy Mobile IPv6, except with 240 deviation in some aspects for obvious reasons of supporting a 241 network-based mobility model. Following are some of the related 242 considerations. 244 o The messaging options, IPv4 Home Address, IPv4 Address 245 Acknowledgement, IPv4 Care-of Address option defined in [ID- 246 DSMIP6] for use in Binding Update and Binding Acknowledgement 247 messages are used by this specification to be carried in Proxy 248 Binding Update and Proxy Binding Acknowledgement messages. 250 o The extensions needed to the conceptual data structures, Binding 251 Cache entry and Binding Update List entry, for storing the state 252 related to the IPv4 support defined in [ID-DSMIP6], will all be 253 needed and relevant for this document. 255 o The NAT traversal logic specified in [ID-DSMIP6] for detecting the 256 on-path NAT devices is valid for this specification as well. 258 o The tunneling considerations specified in [ID-DSMIP6] for 259 supporting IPv4 transport is relevant for this document as well. 261 If a given home agent [RFC-3775] implementation has support for both 262 Dual-stack Mobile IPv6 [ID-DSMIP6] and local mobility anchor function 263 [RFC-5213], when extending IPv4 support as specified in this document 264 the above common functions and the related considerations have to be 265 reused for Proxy Mobile IPv6 signaling flows. 267 2. Conventions & Terminology 269 2.1. Conventions 271 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 272 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 273 document are to be interpreted as described in RFC 2119 [RFC-2119]. 275 2.2. Terminology 277 All the mobility related terms used in this document are to be 278 interpreted as defined in the Mobile IPv6 specification [RFC-3775] 279 and Proxy Mobile IPv6 specification [RFC-5213]. In addition this 280 document introduces the following terms. 282 IPv4 Proxy Care-of Address (IPv4-Proxy-CoA) 284 The IPv4 address that is configured on the egress-interface of the 285 mobile access gateway. When using IPv4 transport, this address 286 will be the registered care-of address in the mobile node's 287 Binding Cache entry and will also be the transport-endpoint of the 288 tunnel between the local mobility anchor and a mobile access 289 gateway. However, if the configured address is a private IPv4 290 address and with a NAT device in the path to the local mobility 291 anchor, the care-of address as seen by the local mobility anchor 292 will be the address allocated by the NAT device for that flow. 294 IPv4 Local Mobility Anchor Address (IPv4-LMAA) 296 The IPv4 address that is configured on the egress-interface of the 297 local mobility anchor. When using IPv4 transport, the mobile 298 access gateway sends the Proxy Binding Update messages to this 299 address and will be the transport-endpoint of the tunnel between 300 the local mobility anchor and the mobile access gateway. 302 Mobile Node's IPv4 Home Address (IPv4-MN-HoA) 304 The IPv4 home address assigned to the mobile node's attached 305 interface. This address is topologically anchored at the local 306 mobility anchor. The mobile node configures this address on its 307 attached interface. If the mobile node connects to the Proxy 308 Mobile IPv6 domain via multiple interfaces each of the interfaces 309 are assigned a unique IPv4 address. All the IPv6 home network 310 prefixes and the IPv4 home address assigned to a given interface 311 of a mobile node will be managed under one mobility session. 313 Selective De-registration 314 It is a procedure for partial de-registration of all the addresses 315 that belong to one address family, i.e., de-registration of either 316 IPv4 home address, or all of the IPv6 home network prefixes. 318 Encapsulation Modes 320 This document uses the following terms when referring to the 321 different encapsulation modes. 323 IPv4-or-IPv6-over-IPv6 325 IPv4 or IPv6 packet carried as a payload of an IPv6 packet 327 IPv4-or-IPv6-over-IPv4 329 IPv4 or IPv6 packet carried as a payload of an IPv4 packet 331 IPv4-or-IPv6-over-IPv4-UDP 333 IPv4 or IPv6 packet carried as a payload in an UDP header of an 334 IPv4 packet 336 IPv4-or-IPv6-over-IPv4-UDP-TLV 338 IPv4 packet carried as a payload in an IPv4 packet with UDP and 339 TLV headers 341 3. IPv4 Home Address Mobility Support 343 The IPv4 home address mobility support essentially enables a mobile 344 node in a Proxy Mobile IPv6 domain to obtain IPv4 home address 345 configuration for its attached interface and be able to retain that 346 address configuration even after changing its point of attachment in 347 that Proxy Mobile IPv6 domain. This section describes the protocol 348 operation and the required extensions to Proxy Mobile IPv6 protocol 349 for extending IPv4 home address mobility support. 351 When an IPv4-enabled or a dual-stack enabled mobile node attaches to 352 the Proxy Mobile IPv6 domain, the mobile access gateway on the access 353 link where the mobile node is attached will identify the mobile node 354 and will initiate the Proxy Mobile IPv6 signaling with the mobile 355 node's local mobility anchor. The mobile access gateway will follow 356 the signaling considerations specified in Section 3.2 for requesting 357 IPv4 home address mobility support. Upon the completion of the 358 signaling, the local mobility anchor and the mobile access gateway 359 will establish the required routing states for allowing the mobile 360 node to use its IPv4 home address from its current point of 361 attachment. 363 The mobile node on the access link using any of the standard IPv4 364 address configuration mechanisms supported on that access link, such 365 as IPCP [RFC-1332], IKEv2 [RFC-4306] or DHCP [RFC-2131], will be able 366 to obtain an IPv4 home address (IPv4-MN-HoA) for its attached 367 interface. Although the address configuration mechanisms for 368 delivering the address configuration to the mobile node is 369 independent of the Proxy Mobile IPv6 protocol operation, however 370 there needs to be some interactions between these two protocol flows. 371 Section 3.4 identifies these interactions for supporting DHCP based 372 address configuration. 374 The support for IPv4 home address mobility is not dependent on the 375 IPv6 home address mobility support. It is not required that the IPv6 376 home address mobility support needs to be enabled for providing IPv4 377 home address mobility support. A mobile node will be able to obtain 378 IPv4-only, IPv6-only or dual IPv4/IPv6 address configuration for its 379 attached interface. The mobile node's policy profile will determine 380 if the mobile node is entitled for both the protocol versions or a 381 single protocol version. Based on the policy, only those protocols 382 will be enabled on the access link. Furthermore, if the mobile node 383 after obtaining the address configuration on its interface performs 384 an handoff, either by changing its point of attachment over the same 385 interface or to a different interface, the network will ensure the 386 mobile node will be able to use the same IPv4 address configuration 387 after the handoff. If the mobile node is DNAv4 [RFC-4436] capable 388 and if it performs DNAv4 procedures after a handoff, it would always 389 detect the same default-router on any of the access links in that 390 Proxy Mobile IPv6 domain, as the mobile access gateway configures a 391 fixed link-layer address on all the access links. 393 Additionally, If the mobile node connects to the Proxy Mobile IPv6 394 domain, through multiple interfaces and simultaneously through 395 different access networks, each of the connected interfaces will 396 obtain an IPv4 home address from different subnets. In such 397 scenario, there will be multiple Binding Cache entries for the mobile 398 node on the local mobility anchor. All the address (IPv4/IPv6) 399 assigned to a given interface will be managed as part of one mobility 400 session, as specified in Section 5.4 of [RFC-5213]. 402 3.1. Local Mobility Anchor Considerations 404 3.1.1. Extensions to Binding Cache Entry 406 To support this feature, the conceptual Binding Cache entry data 407 structure maintained by the local mobility anchor needs to include 408 the following parameters. 410 o The IPv4 home address assigned to the mobile node's interface and 411 registered by the mobile access gateway. The IPv4 home address 412 entry also includes the corresponding subnet mask. It is to be 413 noted that this parameter is defined in the [ID-DSMIP6] and is 414 presented here for completeness. 416 o The IPv4 default-router address assigned to the mobile node. 418 3.1.2. Signaling Considerations 420 3.1.2.1. Processing Proxy Binding Updates 422 The processing rules specified in Section 5.3 of [RFC-5213] are 423 applied for processing the received Proxy Binding Update message. 424 However, if the received Proxy Binding Update message has an IPv4 425 Home Address option [ID-DSMIP6], the following considerations MUST be 426 applied additionally. 428 o If there is an IPv4 Home Address option [ID-DSMIP6] present in the 429 received Proxy Binding Update message, but if there is no Home 430 Network Prefix option [RFC-5213] present in the request, the local 431 mobility anchor MUST NOT reject the request as specified in 432 Section 5.3.1 of [RFC-5213]. At least one instance of any of 433 these two options MUST be present. If there is not a single 434 instance of any of these two options present in the request, the 435 local mobility anchor MUST reject the request and send a Proxy 436 Binding Acknowledgement message with Status field set to 437 MISSING_HOME_NETWORK_PREFIX_OPTION (Missing mobile node's home 438 network prefix option) [RFC-5213]. 440 o If there is at least one instance of Home Network Prefix option 441 [RFC-5213] present in the received Proxy Binding Update message, 442 but either if it is known from the mobile node's policy profile 443 that the mobile node is not authorized for IPv6 service or if IPv6 444 routing not enabled in the home network, the local mobility anchor 445 MUST reject the request and send a Proxy Binding Acknowledgement 446 message with the Status field set to 447 NOT_AUTHORIZED_FOR_IPV6_HOME_NETWORK_PREFIX (mobile node not 448 authorized for the requesting IPv6 home network prefix). 450 o If there are more than one instance of the IPv4 Home Address 451 option present in the request, then the local mobility anchor MUST 452 reject the request and send a Proxy Binding Acknowledgement 453 message with the Status field set to 454 MULTIPLE_IPV4_HOME_ADDRESS_ASSIGNMENT_NOT_SUPPORTED (multiple IPv4 455 home address assignment not supported). 457 o If the prefix request(P) flag in the IPv4 Home Address option is 458 set to a value of 1, then the local mobility anchor MUST reject 459 the request and send a Proxy Binding Acknowledgement message with 460 the Status field set to IPV4_PREFIX_ASSIGNMENT_NOT_SUPPORTED (IPv4 461 prefix assignment not supported). 463 o For associating the received Proxy Binding Update message to an 464 existing mobility session, the local mobility anchor MUST perform 465 the Binding Cache entry existence test by applying the following 466 considerations. 468 * If there is at least one instance of the Home Network Prefix 469 option [RFC-5213] with a NON_ZERO prefix value, or, if there is 470 an IPv4 Home Address option [ID-DSMIP6] with the IPv4 address 471 in the option set to ALL_ZERO, considerations from Section 472 5.4.1 of [RFC-5213] MUST be applied. 474 * If there is an IPv4 Home Address option [ID-DSMIP6] present in 475 the request with the IPv4 address value in the option set to a 476 NON_ZERO value, considerations from Section 3.1.2.7 MUST be 477 applied. 479 o If there is no existing Binding Cache entry that can be associated 480 with the request, the local mobility anchor MUST consider this 481 request as an initial binding registration request and 482 considerations from Section 3.1.2.2 MUST be applied. 484 Additionally, if there are one or more Home Network Prefix options 485 [RFC-5213] present in the request, considerations from Section 486 5.3.2 of [RFC-5213] MUST also be applied. 488 o If there exists a Binding Cache entry that can be associated with 489 the request, the local mobility anchor MUST apply considerations 490 from Section 5.3.1 of [RFC-5213], (point 13), to determine if the 491 request is re-registration or a de-registration request and the 492 respective considerations from the below sections MUST be applied. 494 o If there exists a Binding Cache entry that can be associated with 495 the request and if it is determined that the request is a re- 496 registration request and with the request to extend IPv4 home 497 address mobility support to the existing IPv6-only mobility 498 session, considerations from Section 3.1.2.2 MUST be applied with 499 respect to IPv4 support. 501 3.1.2.2. Initial Binding Registration (New Mobility Session) 503 o If there is an IPv4 Home Address option [ID-DSMIP6] present in the 504 Proxy Binding Update message with the IPv4 address value in the 505 option set to ALL_ZERO, the local mobility anchor MUST allocate an 506 IPv4 home address to the mobile node and associate it with the new 507 mobility session created for that mobile node. 509 o If there is an IPv4 Home Address option [ID-DSMIP6] with the IPv4 510 address in the option set to a NON_ZERO value, the local mobility 511 anchor before accepting the request MUST ensure the address is 512 topologically anchored on the local mobility anchor and 513 furthermore the mobile node is authorized to use that address. If 514 the mobile node is not authorized for that specific address, the 515 local mobility anchor MUST reject the request and send a Proxy 516 Binding Acknowledgement message with the Status field set to 517 NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS (mobile node not authorized 518 for the requesting IPv4 address). It MUST also include the IPv4 519 Address Acknowledgement option [ID-DSMIP6] in the reply with the 520 status field value in the option set to 129 (Administratively 521 prohibited). 523 o If the local mobility anchor is unable to allocate an IPv4 address 524 due to lack of resources, it MUST reject the request and send a 525 Proxy Binding Acknowledgement message with Status field set to 130 526 (Insufficient resources). It MUST also include the IPv4 Address 527 Acknowledgement option [ID-DSMIP6] in the reply with the status 528 field value in the option set to 128 (Failure, reason 529 unspecified). 531 o Upon accepting the request, the local mobility anchor MUST create 532 a Binding Cache entry for this mobility session. However, if the 533 request also contains one or more Home Network Prefix options [ID- 534 DSMIP6], there should still be only one Binding Cache entry that 535 should be created for this mobility session. The created Binding 536 Cache entry MUST be used for managing both IPv4 and IPv6 home 537 address bindings. The fields in the Binding Cache entry MUST be 538 updated with the accepted values for that session. 540 o The local mobility anchor MUST establish a bi-directional tunnel 541 to the mobile access gateway and with the encapsulation mode set 542 to the negotiated mode for carrying the IPv4 payload traffic. 543 When using IPv6 transport, the encapsulation mode is IPv4-or-IPv6- 544 over-IPv6 (IPv4 or IPv6 packet carried as a payload of an IPv6 545 packet). When using IPv4 transport, the encapsulation mode is as 546 specified in Section 4.0. 548 o The local mobility anchor MUST create an IPv4 host route (or a 549 platform specific equivalent function that sets up the forwarding) 550 for tunneling the packets received for the mobile node's home 551 address associated with this mobility session. 553 o The local mobility anchor MUST send the Proxy Binding 554 Acknowledgement message with the Status field set to 0 (Proxy 555 Binding Update Accepted). The message MUST be constructed as 556 specified in Section 3.1.2.6. 558 3.1.2.3. Binding Lifetime Extension (No handoff) 560 All the considerations from Section 5.3.3 of [RFC-5213] MUST be 561 applied. 563 3.1.2.4. Binding Lifetime Extension (After handoff) 565 o If there is no Home Network Prefix option(s) [RFC-5213] present in 566 the request, but if the Binding Cache entry associated with this 567 request has IPv6 home network prefix(es), the local mobility 568 anchor MUST consider this as a request to extend lifetime only for 569 the IPv4 home address and not for the IPv6 home network 570 prefix(es). Hence, the local mobility anchor SHOULD release all 571 the IPv6 home network prefix(es) assigned to that mobile node and 572 for that specific attached interface. Similar considerations 573 apply for the case where there is no IPv4 Home Address option [ID- 574 DSMIP6] present in the request, but if the Binding Cache entry 575 associated with that request has both IPv4 home address and IPv6 576 home network prefix(es). 578 o The local mobility anchor MUST remove the previously created IPv4 579 host route (or the forwarding state) and the dynamically created 580 bi-directional tunnel for carrying the IPv4 payload traffic (if 581 there are no other mobile nodes for which the tunnel is being 582 used). This will remove the routing state towards the mobile 583 access gateway where the mobile node was anchored prior to the 584 handoff. 586 o The local mobility anchor MUST create a bi-directional tunnel to 587 the mobile access gateway that sent the request (if there is no 588 existing bi-directional tunnel) and with the encapsulation mode 589 set to the negotiated mode for carrying the IPv4 payload traffic. 590 An IPv4 host route for tunneling the packets received for the 591 mobile node's IPv4 home address MUST also be added. 593 o The required forwarding state identified in Section 5.3.6 of [RFC- 594 5213] is for IPv6 payload traffic. Those considerations apply for 595 IPv4 payload traffic as well. However, if IPv4 transport is in 596 use, considerations from Section 4.0 MUST be applied. 598 3.1.2.5. Binding De-Registration 600 All the considerations from Section 5.3.5 of [RFC-5213] MUST be 601 applied. Additionally, for removing the IPv4 state as part of the 602 Binding Cache entry deletion, the IPv4 host route and the dynamically 603 created bi-directional tunnel for carrying the IPv4 payload traffic 604 (if there are no other mobile nodes for which the tunnel is being 605 used) MUST be removed. However, if the request is for a selective 606 de-registration (IPv4 home address only, or all the IPv6 home network 607 prefixes), the Binding Cache entry MUST NOT be deleted, only the 608 respective states with respect to those addresses MUST be deleted. 610 3.1.2.6. Constructing the Proxy Binding Acknowledgement Message 612 The local mobility anchor when sending the Proxy Binding 613 Acknowledgement message to the mobile access gateway MUST construct 614 the message as specified in Section 5.3.6 of [RFC-5213]. 615 Additionally, the following considerations MUST be applied. 617 o Section 5.3.6 of [RFC-5213] requires the local mobility anchor to 618 include at least one instance of Home Network Prefix option [RFC- 619 5213] in the Proxy Binding Acknowledgement message that it sends 620 to the mobile access gateway. However, if the received Proxy 621 Binding Update message has only the IPv4 Home Address option [ID- 622 DSMIP6] and did not contain the Home Network Prefix option(s), 623 then the local mobility anchor MUST NOT include any Home Network 624 Prefix option(s) in the reply. However, there MUST be at least 625 one instance of either the Home Network Prefix option [RFC-5213] 626 or the IPv4 Address Acknowledgement option [ID-DSMIP6] present in 627 the Proxy Binding Acknowledgement message. 629 o The IPv4 Address Acknowledgement option [ID-DSMIP6] MUST be 630 present in the Proxy Binding Acknowledgement message. 632 1. If the Status field is set to a value greater than or equal to 633 128, i.e., if the Proxy Binding Update is rejected, then there 634 MUST be an IPv4 Address Acknowledgement option [ID-DSMIP6] 635 corresponding to the IPv4 Home Address option [ID-DSMIP6] 636 present in the request and with the IPv4 address value and the 637 prefix length fields in the option set to the corresponding 638 values in the request. The status field value in the option 639 must be set to the specific error code. 641 2. For all other cases, there MUST be an IPv4 Address 642 Acknowledgement option for carrying the IPv4 home address 643 assigned for that mobility session and with the value in the 644 option set to the allocated IPv4 address. The prefix length 645 in the option MUST be set to the prefix length of the 646 allocated address. The status field value in the option must 647 be set to 0 (Success). 649 o The IPv4 Default-Router Address option MUST be present, if the 650 Status field value in the Proxy Binding Acknowledgement message is 651 set to 0 (Proxy Binding Update Accepted). Otherwise, the option 652 MUST NOT be present. If the option is present, the default-router 653 address in the option MUST be set to the mobile node's default- 654 router address. 656 3.1.2.7. Binding Cache Entry Lookup Considerations 658 The Binding Cache entry lookup considerations specified in section 659 5.4.1.1 of [RFC-5213] uses the Home Network Prefix option [RFC-5213] 660 as the key parameter for identifying the Binding Cache entry. 661 However, when there is not a single Home Network Prefix option with 662 NON_ZERO value present in the request, but if there an IPv4 Home 663 Address option with a NON_ZERO value present in the request, the 664 following considerations MUST be applied. 666 o The search rules specified in section 5.4.1.1 of [RFC-5213], which 667 primarily uses IPv6 home network prefix set as the search key, are 668 equally valid when using a single IPv4 home address as the key. 669 When applying those considerations, instead of the IPv6 home 670 network prefix(es), the IPv4 home address from the IPv4 Home 671 Address option present in the request MUST be used as the search 672 key. 674 o These rules specified in section 5.4.1.1 of [RFC-5213], assume the 675 presence of one or more IPv6 home network prefixes in the received 676 request and also in the Binding Cache entry. But, when using the 677 IPv4 home address as the search key, these considerations MUST 678 always assume just one single IPv4 home address, both in the 679 request and also in the Binding Cache entry. 681 3.1.3. Routing Considerations for the Local Mobility Anchor 683 Intercepting Packets Sent to the Mobile Node's IPv4 home address: 685 o When the local mobility anchor is serving a mobile node, it MUST 686 be able to receive packets that are sent to the mobile node's IPv4 687 home address. In order for it to receive those packets, it MUST 688 advertise a connected route in to the Routing Infrastructure for 689 the mobile node's IPv4 home address or for its home subnet. This 690 essentially enables IPv4 routers in that network to detect the 691 local mobility anchor as the last-hop router for that subnet. 693 Forwarding Packets to the Mobile Node: 695 o On receiving a packet from a correspondent node with the 696 destination address matching the mobile node's IPv4 home address, 697 the local mobility anchor MUST forward the packet through the bi- 698 directional tunnel setup for that mobile node. 700 o The format of the tunneled packet when payload protection is not 701 enabled: 703 IPv6 header (src= LMAA, dst= Proxy-CoA /* Tunnel Header */ 704 IPv4 header (src= CN, dst= IPv4-MN-HOA ) /* Packet Header */ 705 Upper layer protocols /* Packet Content*/ 707 Figure 2: Tunneled Packets from LMA to MAG 709 Forwarding Packets Sent by the Mobile Node: 711 o All the reverse tunneled packets that the local mobility anchor 712 receives from the mobile access gateway, after removing the tunnel 713 header MUST be routed to the destination specified in the inner 714 IPv4 packet header. These routed packets will have the source 715 address field set to the mobile node's IPv4 home address. 717 3.2. Mobile Access Gateway Considerations 719 3.2.1. Extensions to Binding Update List Entry 721 To support the IPv4 home address mobility feature, the conceptual 722 Binding Update List entry data structure needs to be extended with 723 the following additional fields. 725 o The IPv4 home address assigned to the mobile node's attached 726 interface. This IPv4 home address may have been statically 727 configured in the mobile node's policy profile, or, may have been 728 dynamically allocated by the local mobility anchor. The IPv4 home 729 address entry also includes the corresponding subnet mask. 731 o The IPv4 default-router address of the mobile node. This is 732 acquired from the mobile node's local mobility anchor through the 733 received Proxy Binding Acknowledgment message. 735 3.2.2. Extensions to Mobile Node's Policy Profile 737 To support the IPv4 Home Address Mobility Support feature the mobile 738 node's policy profile, specified in Section 6.2 of [RFC-5213] MUST be 739 extended with the following additional fields. 741 Extensions to the mandatory section of the policy profile: 743 o This field identifies all the IP protocol versions for which the 744 home address mobility support needs to be extended to the mobile 745 node. The supported modes are IPv4-only, IPv6-only and dual IPv4/ 746 IPv6. 748 Extensions to the optional section of the policy profile: 750 o The IPv4 home address assigned to the mobile node's attached 751 interface. The specific details on how the network maintains the 752 association between the address and the attached interface is 753 outside the scope of this document. This address field also 754 includes the corresponding subnet mask. 756 3.2.3. Signaling Considerations 757 3.2.3.1. Mobile Node Attachment and Initial Binding Registration 759 After detecting a new mobile node on its access link, the mobile 760 access gateway on the access link MUST determine if IPv4 home address 761 mobility support needs to be enabled for that mobile node. The 762 mobile node's policy profile identifies the supported modes (IPv4- 763 only, IPv6-only or dual IPv4/IPv6) for that mobile node for which the 764 mobile service needs to be enabled. Based on those policy 765 considerations and from other triggers such as from the network, if 766 it is determined that IPv4 home address mobility support needs to be 767 enabled for the mobile node, considerations from section 6.9.1.1 of 768 [RFC-5213] MUST be applied with the following exceptions. 770 o The IPv4 Home Address option [ID-DSMIP6] MUST be present in the 771 Proxy Binding Update message. 773 * If the mobile access gateway learns the mobile node's IPv4 home 774 address either from its policy profile, or from other means, 775 the mobile access gateway MAY ask the local mobility anchor to 776 allocate that specific address by including exactly one 777 instance of the IPv4 Home Address option [ID-DSMIP6] with the 778 IPv4 home address and the prefix length fields in the option 779 set to that specific address and its prefix length. 780 Furthermore, the (P) flag in the option MUST be set to 0. 782 * The mobile access gateway MAY also ask the local mobility 783 anchor for dynamic IPv4 home address allocation. It can 784 include exactly one instance of the IPv4 Home Address option 785 with the IPv4 home address and the prefix length fields in the 786 option set to ALL_ZERO value. Furthermore, the (P) flag in the 787 option MUST be set to 0. This essentially serves as a request 788 to the local mobility anchor for the IPv4 home address 789 allocation. 791 o The Proxy Binding Update message MUST be constructed as specified 792 in Section 6.9.1.5 of [RFC-5213]. However, the Home Network 793 Prefix option(s) [RFC-5213] MUST be present in the Proxy Binding 794 Update only if IPv6 home address mobility support also needs to be 795 enabled for the mobile node. Otherwise, the Home Network Prefix 796 option(s) MUST NOT be present. 798 o When using IPv4 transport for carrying the signaling messages, the 799 related considerations from section 4.0 MUST be applied 800 additionally. 802 3.2.3.2. Receiving Proxy Binding Acknowledgement 804 All the considerations from section 6.9.1.2 of [RFC-5213] MUST be 805 applied with the following exceptions. 807 o If the received Proxy Binding Acknowledgement message has the 808 Status field value set to NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS(The 809 mobile node is not authorized for IPv4 home address), the mobile 810 access gateway SHOULD NOT send a Proxy Binding Update message 811 including the IPv4 Home Address option [ID-DSMIP6] till an 812 administrative action is taken. 814 o If the received Proxy Binding Acknowledgement message has the 815 Status field value set to NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS(The 816 mobile node is not authorized for the requesting IPv4 home 817 address), the mobile access gateway SHOULD NOT request for the 818 same address again, but MAY request the local mobility anchor to 819 do the assignment of address by including exactly one instance of 820 IPv4 Home Address option [ID-DSMIP6] with the IPv4 home address 821 and the prefix length fields in the option set to ALL_ZERO value. 823 o If there is no IPv4 Address Acknowledgement option [ID-DSMIP6] 824 present in the received Proxy Binding Acknowledgement message, the 825 mobile access gateway MUST NOT enable IPv4 support for the mobile 826 node and the rest of the considerations from this section can be 827 skipped. 829 o If the received Proxy Binding Acknowledgement message has the 830 Status field value in the IPv4 Address Acknowledgement Option [ID- 831 DSMIP6] set to a value that indicates that the request was 832 rejected by the local mobility anchor, the mobile access gateway 833 MUST NOT enable forwarding for that specific IPv4 home address. 835 o If the received Proxy Binding Acknowledgement message has the 836 Status field value set to 0 (Proxy Binding Update accepted), the 837 mobile access gateway MUST update a Binding Update List entry for 838 that mobile node. The entry MUST be updated with the assigned 839 IPv4 home address and other accepted registration values. 841 o If the received Proxy Binding Acknowledgement message has the 842 Status field value set to 0 (Proxy Binding Update accepted) and 843 has the IPv4 Address Acknowledgement Option [ID-DSMIP6] set to a 844 value that indicates that the request was accepted by the local 845 mobility anchor, the mobile access gateway MUST establish a bi- 846 directional tunnel to the local mobility anchor (if there is no 847 existing bi-directional tunnel to that local mobility anchor) and 848 with the encapsulation mode set to IPv4-or-IPv6-over-IPv6 (IPv4 or 849 IPv6 packet carried as a payload of an IPv6 packet). 851 Considerations from Section 5.6.1 of [RFC-5213] MUST be applied 852 for managing the dynamically created bi-directional tunnel. 853 However, when using IPv4 transport, the encapsulation mode MUST be 854 set to the negotiated encapsulation mode, as specified in Section 855 4 of this specification. 857 o The mobile access gateway MUST set up the route for forwarding the 858 IPv4 packets received from the mobile node (using its IPv4 home 859 address) through the bi-directional tunnel set up for that mobile 860 node. 862 o The default-router address MUST be obtained from the IPv4 Default- 863 Router Address option present in the received Proxy Binding 864 Acknowledgement message. The mobile access gateway MAY configure 865 this address on its interface and respond to any ARP requests sent 866 by the mobile node for resolving the hardware address of the 867 default-router. It MAY also use this address as the source 868 address for any datagrams sent to the mobile node and originated 869 by the mobile access gateway itself. It MAY also use this address 870 in the DHCP Router option [RFC-2132] in the DHCP messages. 872 o If there is an IPv4 DHCP Support Mode option present in the 873 received Proxy Binding Acknowledgement message and if the (S) flag 874 in the option is set to a value of 1, then the mobile access 875 gateway MUST function as a DHCP server for the mobile node. If 876 either the (S) flag in the option is set to a value of 0, or if 877 the option is not present in the request, then the mobile access 878 gateway MUST function as a DHCP Relay for the mobile node. 880 3.2.3.3. Binding Re-Registration and De-Registrations 882 When sending a Proxy Binding Update either for extending the lifetime 883 of a mobility session or for de-registering the mobility session, the 884 respective considerations from [RFC-5213] MUST be applied. 885 Furthermore, the following additional considerations MUST also be 886 applied. 888 o If there is an IPv4 home address assigned to the mobility session, 889 then there MUST be exactly one instance of the IPv4 Home Address 890 option [ID-DSMIP6] present in the Proxy Binding Update message. 891 The IPv4 home address and the prefix length fields in the option 892 MUST be set to that specific address and its corresponding subnet- 893 mask length. The (P) flag in the option MUST be set to 0. 895 o If there was no IPv4 home address requested in the initial Proxy 896 Binding Update message, but if it is determined that the IPv4 home 897 address MUST be requested subsequently, then there MUST be exactly 898 one instance of the IPv4 Home Address option [ID-DSMIP6] present 899 in the Proxy Binding Update message. The IPv4 home address in the 900 option MUST be set to either ALL_ZERO or to a specific address 901 that is being requested. 903 o For performing selective de-registration of IPv4 home address but 904 still retaining the mobility session with all the IPv6 home 905 network prefixes, the Proxy Binding Update message with the 906 lifetime value of 0 MUST NOT include any IPv6 Home Network Prefix 907 options(s) [RFC-5213]. It MUST include exactly one instance of 908 the IPv4 Home Address option [ID-DSMIP6] with the IPv4 home 909 address and the prefix length fields in the option set to the IPv4 910 home address that is being de-registered. Similarly for selective 911 de-registration of all the IPv6 home network prefixes, the Proxy 912 Binding Update message MUST NOT include the IPv4 Home address 913 option, it MUST include a Home Network Prefix option for each of 914 the assigned home network prefixes assigned for that mobility 915 session and with the prefix value in the option set to that 916 respective prefix value. 918 o The Home Network Prefix option(s) [RFC-5213] MUST NOT be present 919 if the same option(s) was not present in the initial Proxy Binding 920 Update message. Otherwise considerations from [RFC-5213] with 921 respect to this option MUST be applied. 923 3.2.4. Routing Considerations for the Mobile Access Gateway 925 o On receiving a packet from the bi-directional tunnel established 926 with the mobile node's local mobility anchor, the mobile access 927 gateway MUST remove the outer header before forwarding the packet 928 to the mobile node. 930 o Considerations from Section 6.10.3 of [RFC-5213] MUST be applied 931 with respect the local routing and on the use of 932 EnableMAGLocalRouting flag. 934 o On receiving a packet from a mobile node connected to its access 935 link, the packet MUST be forwarded to the local mobility anchor 936 through the bi-directional tunnel established with the local 937 mobility anchor. The encapsulation considerations specified in 938 section 3.1.3 MUST be applied. However, before forwarding the 939 packet, the mobile access gateway MUST ensure the source address 940 in the received packet is the address allocated for that mobile 941 node and that there is an active binding on the local mobility 942 anchor for that mobile node. 944 3.3. Mobility Options and Status Codes 946 To support the IPv4 home address mobility feature, this specification 947 defines the following new options and Status Codes. 949 3.3.1. IPv4 Default-Router Address Option 951 A new option, IPv4 Default-Router Address Option is defined for using 952 it in the Proxy Binding Acknowledgment message [RFC-5213] sent by the 953 local mobility anchor to the mobile access gateway. This option can 954 be used for sending the mobile node's IPv4 default-router address. 956 The IPv4 Default-Router Address option has an alignment requirement 957 of 4n. Its format is as follows: 959 0 1 2 3 960 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 1 961 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 962 | Type | Length | Reserved (R) | 963 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 964 | IPv4 Default-Router Address | 965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 967 Figure 3: IPv4 Default-Router Address Option 969 Type 971 IANA 973 Length 975 8-bit unsigned integer indicating the length of the option in 976 octets, excluding the type and length fields. This field MUST 977 be set to 6. 979 Reserved (R) 981 This 8-bit field is unused for now. The value MUST be 982 initialized to 0 by the sender and MUST be ignored by the 983 receiver. 985 IPv4 Default-Router Address 986 A four-byte field containing the mobile node's default router 987 address. 989 3.3.2. IPv4 DHCP Support Mode 991 A new option, IPv4 DHCP Support Mode Option is defined for using it 992 in the Proxy Binding Acknowledgment message [RFC-5213] sent by the 993 local mobility anchor to the mobile access gateway. This option can 994 be used for notifying the mobile access gateway, if it should 995 function as a DHCP Server or a DHCP Relay for the attached mobile 996 node. 998 The IPv4 DHCP Support Mode option has no alignment requirement. Its 999 format is as follows: 1001 0 1 2 3 1002 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 1003 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1004 | Type | Length | Reserved (R) |S| 1005 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1007 Figure 4: IPv4 DHCP Support Mode Option 1009 Type 1011 IANA 1013 Length 1015 8-bit unsigned integer indicating the length of the option in 1016 octets, excluding the type and length fields. This field MUST 1017 be set to 2. 1019 Reserved (R) 1021 This 15-bit field is unused for now. The value MUST be 1022 initialized to 0 by the sender and MUST be ignored by the 1023 receiver. 1025 DHCP Support Mode (S) 1027 A 1-bit field that specifies the DHCP support mode. This flag 1028 indicates if the mobile access gateway should function as a 1029 DHCP Server or a DHCP Relay for the attached mobile node. The 1030 flag value of (0) indicates the mobile access gateway should 1031 act as a DHCP Relay and the flag value of (1) indicates it 1032 should act as a DHCP Server. 1034 3.3.3. Status Codes 1036 This document defines the following new Status values for use in the 1037 Proxy Binding Acknowledgement message [RFC-5213]. These values are 1038 to be allocated from the same numbering space, as defined in Section 1039 6.1.8 of [RFC-3775]. 1041 NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS: IANA 1043 Mobile node not authorized for the requesting IPv4 home address 1045 NOT_AUTHORIZED_FOR_IPV6_HOME_NETWORK_PREFIX: IANA 1047 Mobile node not authorized for the requesting IPv6 home network 1048 prefix(es). 1050 MULTIPLE_IPV4_HOME_ADDRESS_ASSIGNMENT_NOT_SUPPORTED 1052 Multiple IPv4 home address assignment not supported 1054 IPV4_PREFIX_ASSIGNMENT_NOT_SUPPORTED 1056 IPv4 prefix assignment not supported 1058 3.4. Supporting DHCP-Based Address Configuration 1060 This section explains how DHCP-based address configuration support 1061 can be enabled for a mobile node in a Proxy Mobile IPv6 domain. It 1062 explains the protocol operation, supported DHCP server deployment 1063 configurations and the protocol interactions between DHCP agents and 1064 mobility entities in each of the supported configurations. 1066 This specification supports the following two DHCP deployment 1067 configurations. 1069 o DHCP relay agent co-located with the mobile access gateway. 1071 o DHCP server co-located in the mobile access gateway. 1073 The following are the configuration requirements: 1075 o The DHCP server or the DHCP relay agent configured on the mobile 1076 access gateway is required to have an IPv4 address for exchanging 1077 the DHCP messages with the mobile node. This address can be 1078 either the IPv4 Proxy Care-of Address or the mobile node's 1079 default-router address provided by the local mobility anchor. 1080 Optionally, all the DHCP servers co-located with the mobile access 1081 gateways in the Proxy Mobile IPv6 domain can be configured with a 1082 fixed IPv4 address. This fixed address can be potentially an IPv4 1083 private address [RFC-1918] that can be used for the DHCP protocol 1084 communication on any of the access links. This address will be 1085 used as the server identifier in the DHCP messages. 1087 o A DHCP server identifies the DHCP client and its interface for 1088 which the address is assigned from the client identifier and the 1089 client hardware address (chaddr) [RFC-2131] fields respectively. 1090 A mobile node in a Proxy Mobile IPv6 domain, can attach to the 1091 network through multiple interfaces and additionally may perform 1092 handoffs between its interfaces. Following are the related 1093 considerations: 1095 * If the mobile node attaches to the Proxy Mobile IPv6 domain 1096 through multiple interfaces, the DHCP server will uniquely 1097 identify each of those interfaces from the client hardware 1098 address and will perform address assignment. As the mobile 1099 node changes its point of attachment in the network and 1100 performs an handoff to a different mobile access gateway, using 1101 the same interface, the DHCP server will always be able to 1102 identify the binding using the presented client hardware 1103 address. The client hardware address and client identifier 1104 will remain as the primary keys for each binding, just as how 1105 they are unique in a Binding Cache entry. 1107 * However, if the mobile node is capable of performing handoff 1108 between interfaces, as per [RFC-5213], the client hardware 1109 address in such scenarios needs to be an identifier that is not 1110 tied to any of those interfaces. The identifier must be a 1111 stable identifier which remains the same through out the mobile 1112 node's attachment in that Proxy Mobile IPv6 domain. This 1113 identifier must remain fixed for a given binding. This 1114 identifier in some implementations can be the identifier 1115 associated to a virtual interface, that is abstracting the 1116 physical interfaces. 1118 o All the DHCP servers co-located with the mobile access gateways in 1119 a Proxy Mobile IPv6 domain can be configured with the same set of 1120 DHCP option values (Ex: DNS Server, SIP Server ..etc.) to ensure 1121 the mobile node receives the same configuration values on any of 1122 the access links in that Proxy Mobile IPv6 domain. 1124 3.4.1. DHCP Server co-located with the Mobile Access Gateway 1126 This section explains the operational sequence of home address 1127 assignment operation when the DHCP server is co-located with the 1128 mobile access gateway. 1130 MN MAG(DHCP-S) LMA 1131 |------>| | 1. DHCPDISCOVER 1132 | |------->| 2. Proxy Binding Update 1133 | |<-------| 3. Proxy Binding Acknowledgement (IPv4 HoA) 1134 | |========| 4. Tunnel/Route Setup 1135 |<------| | 5. DHCPOFFER (IPv4 HoA) 1136 |------>| | 6. DHCPREQUEST (IPv4 HoA) 1137 |<------| | 7. DHCPACK 1138 | | | 1139 * DHCPDISCOVER (Step-1) and Proxy Mobile IPv6 signaling 1140 * (Step-2 to Step-4) may happen in parallel and in no specific order 1141 * Tunnel/Route setup(Step-4) and the subsequent steps will happen in 1142 * in the specified order. 1144 Figure 5: Overview of DHCP Server located at Mobile Access Gateway 1146 Initial IPv4 Home Address Assignment: 1148 o When the mobile node sends a DHCPDISCOVER message [RFC-2131], the 1149 DHCP server co-located with the mobile access gateway will trigger 1150 the mobile access gateway to complete the Proxy Mobile IPv6 1151 signaling. This is the required interaction between these two 1152 protocols. If the mobile access gateway is unable to complete the 1153 Proxy Mobile IPv6 signaling, or, if the local mobility anchor does 1154 not assign an IPv4 address for the mobile node, the mobile access 1155 gateway MUST NOT enable IPv4 support for the mobile node on that 1156 access link. The trigger for initiating Proxy Mobile IPv6 1157 signaling can also be delivered to the mobile access gateway as 1158 part of a context transfer from the previous mobile access 1159 gateway, or delivered from the other network elements in the radio 1160 network, the details of which are outside the scope of this 1161 document. 1163 o After a successful completion of the Proxy Mobile IPv6 signaling 1164 and upon acquiring the mobile node's IPv4 home address from the 1165 local mobility anchor, the DHCP server on the mobile access 1166 gateway will send a DHCPOFFER message [RFC-2131] to the mobile 1167 node. The offered address will be the mobile node's IPv4 home 1168 address, assigned by the local mobility anchor. The server 1169 address, 'siaddr' field of the DHCPOFFER message, will be set to 1170 the mobile node's default-router address. The DHCPOFFER message 1171 will be sent to the mobile node just as specified in [RFC-2131]. 1173 o If the mobile node sends the DHCPREQUEST message, the DHCP server 1174 will send DHCPACK message, as per [RFC-2131]. 1176 IPv4 Home Address Renewal with the DHCP server (No Handoff): 1178 o Any time the mobile node goes into the DHCP RENEWING state [RFC- 1179 2131], it simply unicasts the DHCPREQUEST message including the 1180 assigned IPv4 home address in the 'requested IP address' option. 1181 The DHCPREQUEST is sent to the address specified in 'server 1182 identifier' field of the previously received DHCPOFFER and DHCPACK 1183 messages. 1185 o The DHCP server will send a DHCPACK to the mobile node to 1186 acknowledge the assignment of the committed IPv4 address. 1188 IPv4 Home Address Renewal with a different DHCP server (After 1189 Handoff): 1191 When the mobile node goes into the DHCP RENEWING state [RFC-2131], it 1192 directly unicasts the DHCPREQUEST message to the DHCP server that 1193 currently provided the DHCP lease. However, if the mobile node 1194 changed its point of attachment and is attached to a new mobile 1195 access gateway, it is required that the mobile node updates the DHCP 1196 server address and uses the address of the DHCP server that is co- 1197 located with the new mobile access gateway. The following approach 1198 can be adopted to ensure the mobile node uses the DHCP server on the 1199 attached link. 1201 The use of fixed DHCP server address on all DHCP servers 1202 MN oMAG(DHCP-S) nMAG(DHCP-S) 1203 | : | 1204 RENEW------------->| 1. DHCPREQUEST (IPv4 HoA) 1205 BOUND<-------------| 2. DHCPACK or DHCPNACK 1206 | : | 1208 Figure 6: Address renewal with a different DHCP server 1210 o If a fixed address such as the IPv4 default-router address of the 1211 mobile node is used as the DHCP server Id on any of the links in 1212 that Proxy Mobile IPv6 domain, the DHCPREQUEST message sent by the 1213 mobile node for renewing the address will be received by the new 1214 mobile access gateway on the attached link. The mobile access 1215 gateway after completing the Proxy Mobile IPv6 signaling and upon 1216 acquiring the IPv4 home address of the mobile node will return the 1217 address in the DHCPACK message. However, if the mobile access 1218 gateway is unable to complete the Proxy Mobile IPv6 signaling or 1219 is unable to acquire the same IPv4 address as requested by the 1220 mobile node, it will send a DHCPNACK message [RFC-2131] to the 1221 mobile node, as shown in Figure 6-1). 1223 Additional Operation: 1225 o If at any point the mobile access gateway fails to extend the 1226 binding lifetime with the local mobility anchor for the mobile 1227 node's IPv4 address, it MUST remove any forwarding state set up 1228 for the mobile node's IPv4 home address. 1230 3.4.2. DHCP Relay Agent co-located with the Mobile Access Gateway 1232 A DHCP relay agent is co-located with each mobile access gateway. A 1233 DHCP server is located somewhere in the Proxy Mobile IPv6 domain 1234 (e.g., is co-located with the local mobility anchor). Figure 7 shows 1235 the sequence of IPv4 home address assignment using DHCP Relay. 1237 MN MAG(DHCP-R) LMA DHCP-S 1238 | |------->| | 1. Proxy Binding Update * 1239 | |<-------| | 2. Proxy Binding Acknowledgement (IPv4HoA) 1240 | |========| | 3. Tunnel/Route Setup* 1241 |------>|-------------->| 4. DHCPDISCOVER (IPv4HoA) via DHCP-R 1242 |<------|<--------------| 5. DHCPOFFER (IPv4 HoA) via DHCP-R 1243 |------>|-------------->| 6. DHCPREQUEST (IPv4 HoA) via DHCP-R 1244 |<------|<--------------| 7. DHCPACK via DHCP-R 1245 | | | 1246 * The Proxy Mobile IPv6 signaling (Step-1 to Step-2) and the 1247 DHCPDISCOVER phase (Step-4) may occur in any order. However, 1248 the DHCPOFFER (Step-5) and the following steps will occur in 1249 the specified order and after the Tunnel/Route Setup (Step-3). 1251 Figure 7: Overview of the DHCP relay located at mobile access gateway 1253 Initial IPv4 Home Address Assignment: 1255 o When the mobile access gateway receives a DHCPDISCOVER message 1256 from a mobile node, it can check if there is already an assigned 1257 IPv4 home address for the mobile node, from the local mobility 1258 anchor. If there is no assigned IPv4 home address assigned for 1259 that mobile node, the mobile access gateway has to complete the 1260 Proxy Mobile IPv6 signaling with the local mobility anchor by 1261 sending a Proxy Binding Update message. It is to be noted that 1262 the mobile node needs to be identified by the MN-Identifier, as 1263 specified in Section 6.6 of [RFC-5213]. 1265 o If the Proxy Binding Update message is rejected by the local 1266 mobility anchor for any reason, the mobile access gateway will 1267 discard the DHCPDISCOVER messages from the mobile node. 1269 o If the Proxy Binding Update message is accepted by the local 1270 mobility anchor and if there is an assigned IPv4 home address for 1271 the mobile node, the DHCP messages will be forwarded to the DHCP 1272 server. 1274 o The DHCP relay agent on the mobile access gateway will add the 1275 DHCP relay agent information option [RFC-3046] to the DHCPDISCOVER 1276 message. The assigned IPv4 home address will be included in the 1277 Agent Remote ID Sub-option of the DHCP relay agent information 1278 option. This sub-option is used as a hint for requesting the DHCP 1279 server to allocate that specific IPv4 address. 1281 o On receiving a DHCPOFFER message from the DHCP server, the mobile 1282 access gateway will ensure the assigned address is currently 1283 assigned by the local mobility anchor to that mobile node. If 1284 this address is different from what is assigned to the mobile 1285 node, then the mobile access gateway will drop the DHCPOFFER 1286 message and an administrative error message will be logged. 1288 o When the DHCP messages are sent over administrative boundaries, 1289 the operators needs to ensure these messages are secured. All the 1290 DHCP messages relayed by the mobile access gateway can be tunneled 1291 to the local mobility anchor if needed. Alternatively, if the 1292 network in the Proxy Mobile IPv6 domain is secure enough, the 1293 mobile access gateway can just relay the DHCP messages to the 1294 server. To achieve this, all the mobile access gateways needs to 1295 have a route towards the DHCP server. 1297 IPv4 Home Address Renewal to the same DHCP server: (No Handover) 1299 o When the DHCP client goes into the DHCP RENEW STATE [RFC-2131], it 1300 directly unicasts DHCPREQUEST message to the DHCP server. The 1301 DHCP relay agent may not detect these unicasted DHCPREQUEST 1302 messages for renewing the address. Thus, any of the following 1303 approaches can be adopted. 1305 * The DHCP relay agent can intercept all IPv4 DHCP packets 1306 destined to the set of addresses used within the Proxy Mobile 1307 IPv6 domain as DHCP addresses. Since the link between a mobile 1308 node and a mobile access gateway is the point-to-point link, 1309 the mobile access gateway will be in path for all the messages. 1311 * The DHCP relay agent can use the DHCP Server Identifier 1312 Override Sub-option [RFC-5107] to be in path for all the DHCP 1313 message flows. The DHCP client uses the DHCP server address 1314 which is overridden by the DHCP relay agent address as a 1315 destination address of DHCPREQUEST. The DHCP Server Identifier 1316 Override Sub-option is recommended only when the fixed DHCP 1317 relay address is configured on all the mobile access gateways. 1318 Otherwise, the DHCP relay agent address is changed when the 1319 mobile node changes the attached mobile access gateway. 1321 o The DHCP Relay agent on detecting the DHCPREQUEST message from the 1322 mobile node, will verify if the address in the DHCPREQUEST message 1323 is the address assigned by the local mobility anchor for that 1324 mobile node. If the requesting IPv4 home address is not 1325 registered to the local mobility anchor, the mobile access gateway 1326 will drop the packet. Once the address verification is 1327 successfully completed, the DHCP relay agent will forward the 1328 DHCPREQUEST message to the DHCP server. However, the mobile 1329 access gateway is neither required to perform this check, nor 1330 intercept the DCHPREQUEST message from the mobile node, if the 1331 DHCP server is co-located with the local mobility anchor, as that 1332 check will be performed by the local mobility anchor in such 1333 scenario. The mobile access gateway can determine the co-location 1334 of the DHCP server and the local mobility anchor by comparing the 1335 source address of the DHCPOFFER message with the address of the 1336 mobile node's local mobility anchor. 1338 IPv4 Address Release Triggers from the mobile node: 1340 o The mobile node may release its IPv4 home address at any time by 1341 sending the DHCPRELEASE message [RFC-2131]. When the mobile 1342 access gateway detects the DHCPRELEASE message sent by the mobile 1343 node and for releasing its assigned IPv4 home address, the mobile 1344 access gateway should consider this as a trigger for de- 1345 registering the mobile node's IPv4 home address. It MUST apply 1346 the considerations specified in section 3.2.3.3 for performing the 1347 de-registration procedure. However, this operation should not 1348 release any IPv6 home network prefix(es) assigned to the mobile 1349 node. 1351 Additional Operations: 1353 o If at any point the mobile access gateway fails to extend the 1354 binding lifetime with the local mobility anchor for the mobile 1355 node's IPv4 address, it MUST remove any forwarding state set up 1356 for the mobile node's IPv4 home address. 1358 4. IPv4 Transport Support 1360 The Proxy Mobile IPv6 specification [RFC-5213] requires the signaling 1361 messages exchanged between the local mobility anchor and the mobile 1362 access gateway to be over an IPv6 transport. The extensions defined 1363 in this section allow the exchange of signaling messages over an IPv4 1364 transport when the local mobility anchor and the mobile access 1365 gateway are separated by an IPv4 network and are reachable using only 1366 IPv4 addresses. 1368 IPv4-Proxy-CoA IPv4-LMAA 1369 | + - - - - - - + | 1370 +--+ +---+ / \ +---+ +--+ 1371 |MN|----------|MAG|===== IPv4 Network =====|LMA|----------|CN| 1372 +--+ +---+ \ / +---+ +--+ 1373 + - - - - - - + 1375 Figure 8: IPv4 Transport Network 1377 When the local mobility anchor and the mobile access gateway are 1378 configured and reachable using only IPv4 addresses, the mobile access 1379 gateway serving a mobile node can potentially send the signaling 1380 messages over IPv4 transport and register its IPv4 address as the 1381 care-of address in the mobile node's Binding Cache entry. An IPv4 1382 tunnel (with any of the supported encapsulation modes) can be used 1383 for tunneling the mobile node's data traffic. The following are the 1384 key aspects of this feature. 1386 o The local mobility anchor and the mobile access gateway are both 1387 configured and reachable using an IPv4 address. Additionally, 1388 both entities are also IPv6 enabled and have configured IPv6 1389 addresses on their interfaces, as specified in [RFC-5213], but are 1390 reachable only over an IPv4 transport. 1392 o The mobile access gateway can be potentially in a private IPv4 1393 network behind a NAT [RFC-3022] device, with a private IPv4 1394 address configured on its egress interface. But, the local 1395 mobility anchor must not be behind a NAT and must be using a 1396 globally routable IPv4 address. However, both the local mobility 1397 anchor and the mobile access gateway can be in the same private 1398 IPv4 routing domain, i.e., when both are configured with private 1399 IPv4 addresses and with no need for NAT translation between them. 1401 o The IPv6 address configuration requirement on the mobile access 1402 gateway does not imply there needs to be IPv6 routing enabled 1403 between the local mobility anchor and the mobile access gateway. 1404 It just requires each of the mobile access gateways and local 1405 mobility anchors in a Proxy Mobile IPv6 domain to be configured 1406 with a globally unique IPv6 address. 1408 o The Proxy Mobile IPv6 signaling messages exchanged between the 1409 local mobility anchor and the mobile access gateway for 1410 negotiating the IPv4 transport will be encapsulated and carried as 1411 IPv4 packets. However, these signaling messages are fundamentally 1412 IPv6 messages using the mobility header and the related semantics 1413 as specified in base Proxy Mobile IPv6 specification [RFC-5213], 1414 but carried as a payload in an IPv4 packet. The supported 1415 encapsulation modes for the signaling messages are either native 1416 IPv4 or IPv4 with UDP header. 1418 o The mobile node can be an IPv6, IPv4 or a dual IPv4/IPv6 node and 1419 the IPv4 transport support specified in this section is agnostic 1420 to the type of address mobility enabled for that mobile node. 1422 o The IPv4 tunnel established between the local mobility anchor and 1423 the mobile access gateway (with any of the supported encapsulation 1424 modes over IPv4 transport) will be used for carrying the mobile 1425 node's IPv4 and IPv6 traffic. The following are the outer headers 1426 based on the negotiated encapsulation mode. 1428 * IPv4 (IPv4 or IPv6 Payload packet carried in an IPv4 packet). 1429 If payload protection using IPsec is enabled for the tunneled 1430 traffic, the ESP header follows the outer tunnel header. 1432 * IPv4-UDP (Payload packet carried in an IPv4 packet with UDP 1433 header). If payload protection using IPsec is enabled for the 1434 tunneled traffic, the ESP header follows the outer tunnel 1435 header, as specified in [RFC-3948]. 1437 * IPv4-UDP-TLV (Payload packet carried in an IPv4 packet with UDP 1438 and TLV header). Refer to [ID-GREKEY-NEGO]. If payload 1439 protection using IPsec is enabled for the tunneled traffic, the 1440 ESP header follows the outer tunnel header. 1442 4.1. Local Mobility Anchor Considerations 1444 4.1.1. Extensions to Binding Cache Entry 1446 To support this feature, the conceptual Binding Cache entry data 1447 structure maintained by the local mobility anchor [RFC-5213] MUST be 1448 extended with the following additional parameters. It is to be noted 1449 that all of these parameters are specified in [ID-DSMIP6] and also 1450 required here in the present usage context, and are presented here 1451 only for completeness. 1453 o The IPv4 Proxy Care-of Address configured on the mobile access 1454 gateway that sent the Proxy Binding Update message. This address 1455 can be obtained from the IPv4 Care-of Address option [ID-DSMIP6], 1456 present in the received Proxy Binding Update message. However, if 1457 the received Proxy Binding Update message is not sent as an IPv4 1458 packet, i.e., when using IPv6 transport, this field in the Binding 1459 Cache entry MUST be set to ALL_ZERO value. 1461 o The IPv4 NAT translated address of the mobile access gateway. If 1462 the mobile access gateway is not behind a NAT [RFC-3022], this 1463 address will be the same as the address configured on the egress 1464 interface of the mobile access gateway. This address can be 1465 obtained from the IPv4 header of the received Proxy Binding Update 1466 message. However, if the received Proxy Binding Update message is 1467 not sent as an IPv4 packet, this field in the Binding Cache entry 1468 MUST be set to ALL_ZERO value. 1470 o The source UDP port, if the Proxy Binding Update was received in 1471 an IPv4 packet with UDP header. 1473 o The destination UDP port, if the Proxy Binding Update was received 1474 in an IPv4 packet with UDP header. 1476 4.1.2. Extensions to Mobile Node's Policy Profile 1478 To support the IPv4 Transport Support feature the mobile node's 1479 policy profile, specified in Section 6.2 of [RFC-5213] MUST be 1480 extended with the following additional fields. These are mandatory 1481 fields of the policy profile required for supporting this feature. 1483 o The IPv4 address of the local mobility anchor (IPv4-LMAA). 1485 4.1.3. Signaling Considerations 1487 This section provides the rules for processing the Proxy Mobile IPv6 1488 signaling messages received over IPv4 transport. 1490 4.1.3.1. Processing Proxy Binding Updates 1492 o If the received Proxy Binding Update message was sent encapsulated 1493 in IPv4 or IPv4-UDP header, the message MUST be authenticated 1494 after removing the outer encapsulation (IPv4 or IPv4-UDP) header. 1495 Considerations from Section 4 of [RFC-5213] MUST be applied for 1496 authenticating and authorizing the request. 1498 o All the considerations from Section 5.3.1 of [RFC-5213] MUST be 1499 applied on the encapsulated Proxy Binding Update message, after 1500 removing the outer encapsulation (IPv4 or IPv4-UDP) header. 1502 o If there is an IPv4 Care-of Address option [ID-DSMIP6] present in 1503 the request and if the outer encapsulation header is IPv4-UDP, 1504 then the NAT presence detection procedure specified in Section 1505 4.1.3.3 MUST be used for detecting the NAT in the path. 1507 o Upon accepting the request, the local mobility anchor MUST set up 1508 an IPv4 bi-directional tunnel to the mobile access gateway. The 1509 tunnel endpoint addresses are IPv4-LMAA and the IPv4-Proxy-CoA. 1510 The encapsulation mode MUST be determined from the below 1511 considerations. 1513 * If the received Proxy Binding Update message was sent with IPv4 1514 encapsulated header, then the encapsulation mode for the bi- 1515 directional tunnel MUST be set to IPv4. Otherwise, the 1516 following considerations apply. 1518 * If NAT is not detected on the path and if the (F) flag in the 1519 received Proxy Binding Update message is set to the value of 1, 1520 but if the configuration flag, 1521 AcceptForcedIPv4UDPEncapsulationRequest, is set to a value of 1522 0, then the local mobility anchor MUST reject the request with 1523 the Status field value set to 129 (Administratively 1524 prohibited). 1526 * If the (T) flag [ID-GREKEY-NEGO] in the Proxy Binding Update 1527 message is set to value of 1, then the encapsulation mode MUST 1528 be set to IPv4-or-IPv6-over-IPv4-UDP-TLV. 1530 * If NAT is detected on the path, or if the (F) flag in the 1531 received Proxy Binding Update message is set to the value of 1, 1532 then the encapsulation mode MUST be set to IPv4-or-IPv6-over- 1533 IPv4-UDP. Otherwise the encapsulation mode MUST be set to 1534 IPv4-or-IPv6-over-IPv4. 1536 o The local mobility anchor MUST send the Proxy Binding 1537 Acknowledgement message with the Status field value set to 0 1538 (Proxy Binding Update Accepted). The message MUST be constructed 1539 as specified in Section 4.1.3.2. 1541 4.1.3.2. Constructing the Proxy Binding Acknowledgement Message 1543 The local mobility anchor when sending the Proxy Binding 1544 Acknowledgement message to the mobile access gateway MUST construct 1545 the message as specified in Section 5.3.6 of [RFC-5213]. However, if 1546 the received Proxy Binding Update message was encapsulated in an IPv4 1547 packet or as a payload in the UDP header of an IPv4 packet, the 1548 following additional considerations MUST be applied. 1550 o The Proxy Binding Acknowledgement message MUST be encapsulated in 1551 an IPv4 packet. However, if the received Proxy Binding Update 1552 message was sent encapsulated in the UDP header of an IPv4 packet, 1553 then the Proxy Binding Acknowledgement message MUST be 1554 encapsulated in the UDP header of an IPv4 packet. 1556 o The source address in the IPv4 header of the message MUST be set 1557 to the destination IPv4 address of the received request. 1559 o If the mobile access gateway and the local mobility anchor are 1560 using globally routable IPv4 addresses and if there is a security 1561 association that is based of IPv4 addresses, then the encapsulated 1562 IPv4 packet (containing the IPv6 Proxy Binding Acknowledgement) 1563 MUST be protected using IPsec ESP [RFC-4301] mode. There is no 1564 need to apply IPsec ESP header to the IPv6 packet. In all other 1565 cases, the Proxy Binding Acknowledgement message MUST be protected 1566 using IPsec prior to the IPv4 or IPv4-UDP encapsulation. 1568 o The NAT Detection option [ID-DSMIP6] MUST be present only if there 1569 is an IPv4 Care-of Address option [ID-DSMIP6] present in the 1570 received Proxy Binding Update message and if the NAT detection 1571 procedure resulted in detecting a NAT on path. However, if the 1572 received Proxy Binding Update message was not sent encapsulated in 1573 IPv4 UDP header, then the option MUST NOT be present. 1574 Furthermore, in all other cases, the option MUST NOT be present. 1576 o The IPv4 DHCP Support Mode option MAY be present. If this option 1577 is not present, the mobile access gateway will enable the default 1578 behavior and function as a DHCP Relay for the mobile node. 1580 o The format of the Proxy Binding Acknowledgement message 1581 encapsulated in an IPv4 packet and protected using IPv6 security 1582 association. The UDP header MUST be present only if the received 1583 Proxy Binding Update message was sent with IPv4-UDP encapsulation 1584 header. 1586 IPv4 header (src=IPv4-LMAA, dst=pbu_src_address) 1587 UDP header (sport=DSMIP_PORT, dport= pbu_sport) /*Optional*/ 1588 /* IPv6 PBA Packet protected with ESP header */ 1590 Figure 9: Proxy Binding Acknowledgment (PBA) Message encapsulated 1591 in IPv4 header 1593 4.1.3.3. NAT Presence Detection 1595 When the transport network between the local mobility anchor and the 1596 mobile access gateway is an IPv4 network and if the received Proxy 1597 Binding Update message was sent encapsulated in IPv4 UDP header, the 1598 local mobility anchor performs the NAT Presence Detection as 1599 specified below. 1601 On receiving the Proxy Binding Update message encapsulated in an IPv4 1602 UDP packet, the local mobility anchor, if it detects a NAT on the 1603 path, will send the Proxy Binding Acknowledgment message with the NAT 1604 Detection Option. The presence of this option in the Proxy Binding 1605 Acknowledgment is an indication to the mobile access gateway about 1606 the presence of NAT in the path. On detecting any NAT in the path, 1607 both the local mobility anchor and the mobile access gateway will set 1608 the encapsulation mode of the tunnel to IPv4-UDP-based encapsulation. 1609 The specific details around the NAT detection and the related logic 1610 are described in DSMIPv6 specification [ID-DSMIP6]. 1612 However, if the value of the configuration variable, 1613 UseIPv4UDPEncapForSignalingMessages, is set to a value of 0, the 1614 mobile access gateway will not use IPv4 UDP encapsulation for Proxy 1615 Binding Update messages and hence the local mobility anchor will not 1616 perform this NAT Presence Detection procedure on these messages that 1617 are not sent in IPv4 UDP packet. 1619 4.1.4. Routing Considerations 1621 4.1.4.1. Forwarding Considerations 1623 Forwarding Packets to the Mobile Node: 1625 o On receiving an IPv4 or an IPv6 packet from a correspondent node 1626 with the destination address matching any of the mobile node's 1627 IPv4 or IPv6 home addresses, the local mobility anchor MUST 1628 forward the packet through the bi-directional tunnel set up for 1629 that mobile node. 1631 o The format of the tunneled packet is shown below. 1633 IPv4 Header (src= IPv4-LMAA, dst= IPv4-Proxy-CoA)] /* Tunnel Header */ 1634 [UDP Header (src port=DSMIPv6, dst port=Z] /* If UDP encap nego */ 1635 [TLV Header] /* If TLV negotiated */ 1636 /* IPv6 or IPv4 Payload Packet */ 1637 IPv6 header (src= CN, dst= MN-HOA) 1638 OR 1639 IPv4 header (src= CN, dst= IPv4 MN-HoA) 1641 Figure 10: Tunneled IPv4 Packet from LMA to MAG 1643 o Forwarding Packets Sent by the Mobile Node: 1645 * All the reverse tunneled packets (IPv4 and IPv6) that the local 1646 mobility anchor receives from the mobile access gateway, after 1647 removing the tunnel header (i.e., the outer IPv4 header along 1648 with the UDP and TLV header, if negotiated) MUST be routed to 1649 the destination specified in the inner packet header. These 1650 routed packets will have the source address field set to the 1651 mobile node's home address. 1653 4.1.4.2. ECN Considerations 1655 The ECN considerations specified in Section 5.6.3 of [RFC-5213] apply 1656 for the IPv4 transport tunnels as well. The mobility agents at the 1657 tunnel entry and exit points MUST handle ECN information as specified 1658 in that document. 1660 4.1.4.3. Bi-Directional Tunnel Management 1662 The Tunnel Management considerations specified in section 5.6.1 of 1663 [RFC-5213] apply for the IPv4 transport tunnels as well, with just 1664 one difference that the encapsulation mode is different. 1666 4.2. Mobile Access Gateway Considerations 1668 4.2.1. Extensions to Binding Update List Entry 1670 To support the IPv4 Transport Support feature, the conceptual Binding 1671 Update List entry data structure maintained by the mobile access 1672 gateway [RFC-5213] MUST be extended with the following additional 1673 parameters. 1675 o The IPv4 address of the local mobility anchor. This address can 1676 be obtained from the mobile node's policy profile. 1678 4.2.2. Signaling Considerations 1680 The mobile access gateway when sending a Proxy Binding Update message 1681 to the local mobility anchor MUST construct the message as specified 1682 in Section 6.9.1.5 of [RFC-5213]. However, if the mobile access 1683 gateway is in an IPv4-only access network, the following additional 1684 considerations MUST be applied. 1686 o The Proxy Binding Update message MUST be encapsulated in an IPv4 1687 packet. However, if the value of the configuration variable, 1688 UseIPv4UDPEncapForSignalingMessages, is set to 1, then the Proxy 1689 Binding Update message MUST be encapsulated in an UDP header of an 1690 IPv4 packet. 1692 o The IPv4 Care-of Address option [ID-DSMIP6] MUST be present. The 1693 IPv4 address in the option MUST be set to the mobile access 1694 gateway's IPv4-Proxy-CoA. 1696 o The packet MUST be constructed as specified in Section 4.2.3. 1698 o Just as specified in [RFC-5213], when sending a Proxy Binding 1699 message for extending the lifetime of a currently existing 1700 mobility session or for de-registering the mobility session, the 1701 Proxy Binding Update message MUST be constructed just as the 1702 initial request. 1704 Receiving Proxy Binding Acknowledgement 1706 o If the received Proxy Binding Acknowledgement message is 1707 encapsulated in IPv4 or IPv4 UDP packet, the message MUST be 1708 authenticated after removing the outer IPv4 or IPv4-UDP header. 1709 Considerations from Section 4 of [RFC-5213] MUST be applied for 1710 authenticating and authorizing the message. 1712 o All the considerations from Section 6.9.1.2 of [RFC-5213] MUST be 1713 applied on the encapsulated Proxy Binding Acknowledgement message, 1714 after removing the outer IPv4 UDP header. 1716 o If the Status field indicates Success, the mobile access gateway 1717 MUST setup a bi-directional tunnel to the local mobility anchor. 1719 o Upon accepting the request, the mobile access gateway MUST set up 1720 an IPv4 bi-directional tunnel to the local mobility anchor. The 1721 tunnel endpoint addresses are IPv4-Proxy-CoA and the IPv4-LMAA. 1722 The encapsulation mode MUST be determined from the below 1723 considerations. 1725 * The encapsulation mode for the bi-directional tunnel MUST be 1726 set to IPv4. However, if the value of the configuration 1727 variable, UseIPv4UDPEncapForSignalingMessages, is set to 1, 1728 then the following considerations MUST be applied. 1730 * If there is a NAT Detection option [ID-DSMIP6] in the received 1731 Proxy Binding Acknowledgement message and if the value of the 1732 configuration flag, UseIPv4UDPEncapForSignalingMessages, is set 1733 to value of 1, then the encapsulation mode for the tunnel MUST 1734 be set to IPv4-UDP. Otherwise the encapsulation mode MUST be 1735 set to IPv4. 1737 * If the (T) flag in the Proxy Binding Acknowledgement message is 1738 set to value of 1, then the encapsulation mode MUST be set to 1739 IPv4-UDP-TLV. 1741 4.2.2.1. Constructing the Proxy Binding Update Message 1743 o The source address in the IPv4 header MUST be set to IPv4-Proxy- 1744 CoA of the mobile access gateway and the destination address MUST 1745 be set to the local mobility anchor's IPv4-LMAA. 1747 o The IPv4 Care-of Address option [ID-DSMIP6] MUST be present. The 1748 address MUST be set to the mobile access gateway's IPv4-Proxy-CoA. 1750 o If the configuration variable ForceIPv4UDPEncapsulationSupport is 1751 set to value of 1, then the (F) flag in the Proxy Binding Update 1752 message MUST be set to value of 1. 1754 o The Proxy Binding Update message MUST be protected using IPsec ESP 1755 [RFC-4301], as specified in [RFC-5213]. The protection MUST be 1756 applied on the IPv6 packet of the Proxy Binding Update message, 1757 prior to the IPv4 encapsulation. 1759 o The format of the Proxy Binding Update message encapsulated in an 1760 IPv4 or IPv4-UDP packet with no IPsec protection: 1762 IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA) 1763 UDP header (sport=ANY, dport= DSMIP_PORT) /*Optional*/ 1764 /* IPv6 PBU Packet protected with ESP header */ 1766 Figure 11: Proxy Binding Update (PBU) message encapsulated in IPv4 1767 UDP header 1769 4.2.2.2. Forwarding Considerations 1771 Forwarding Packets Sent by the Mobile Node: 1773 o On receiving an IPv4 or an IPv6 packet from the mobile node to any 1774 destination, the mobile access gateway MUST tunnel the packet to 1775 the local mobility anchor. The format of the tunneled packet is 1776 shown below. However, considerations from Section 6.10.3 of [RFC- 1777 5213] MUST be applied with respect the local routing and on the 1778 use of EnableMAGLocalRouting flag. 1780 IPv4 Header (src= IPv4-Proxy-CoA, dst= IPv4-LMAA)] /* Tunnel Header */ 1781 [UDP Header (src port=DSMIPv6, dst port=Z] /* If UDP encap nego */ 1782 [TLV Header] /* If TLV negotiated */ 1783 /* IPv6 or IPv4 Payload Packet */ 1784 IPv6 header (src= CN, dst= MN-HOA) 1785 OR 1786 IPv4 header (src= CN, dst= IPv4 MN-HoA) 1788 Figure 12: Tunneled IPv4 Packet from LMA to MAG 1790 o Forwarding Packets received from the bi-directional tunnel: 1792 o On receiving a packet from the bi-directional tunnel established 1793 with the mobile node's local mobility anchor, the mobile access 1794 gateway MUST remove the outer header before forwarding the packet 1795 to the mobile node. 1797 5. Protocol Configuration Variables 1799 5.1. Local Mobility Anchor - Configuration Variables 1801 The local mobility anchor MUST allow the following variables to be 1802 configured by the system management. The configured values for these 1803 protocol variables MUST survive server reboots and service restarts. 1805 AcceptForcedIPv4UDPEncapsulationRequest 1807 This flag indicates whether or not the local mobility anchor 1808 should accept IPv4 UDP encapsulation request for the mobile node's 1809 data traffic, even if there is no NAT detected in the path. 1811 The default value for this flag is set to value of 0, indicating 1812 that the local mobility anchor MUST NOT accept IPv4 UDP 1813 encapsulation request when NAT is not detected in the path. 1815 When the value for this flag is set to value of 1, the local 1816 mobility anchor MUST accept IPv4 UDP encapsulation request even 1817 when NAT is not detected in the path. 1819 5.2. Mobile Access Gateway - Configuration Variables 1821 The mobile access gateway MUST allow the following variables to be 1822 configured by the system management. The configured values for these 1823 protocol variables MUST survive server reboots and service restarts. 1825 UseIPv4UDPEncapForSignalingMessages 1827 This flag indicates whether or not the mobile access gateway 1828 should use IPv4-UDP encapsulation mode for the signaling messages. 1830 The default value for this flag is set to value of 0, indicating 1831 that the mobile access gateway MUST NOT use IPv4-UDP encapsulation 1832 mode, but MUST use native IPv4 encapsulation mode for sending the 1833 Proxy Mobile IPv6 signaling messages. 1835 When the value for this flag is set to value of 1, the mobile 1836 access gateway MUST use IPv4-UDP encapsulation mode for sending 1837 the Proxy Mobile IPv6 signaling messages. 1839 ForceIPv4UDPEncapsulationSupport 1840 This flag indicates whether or not the mobile access gateway 1841 should request the mobile node's local mobility anchor for forcing 1842 IPv4 UDP encapsulation support for the mobile node's data traffic, 1843 even when NAT is not detected in the path. 1845 The default value for this flag is set to value of 0, indicating 1846 that the mobile access gateway MUST NOT request the mobile node's 1847 local mobility anchor for forcing IPv4 UDP encapsulation support 1848 even when NAT is not detected in path. 1850 When the value for this flag is set to value of 1, the mobile 1851 access gateway MUST force the mobile node's local mobility anchor 1852 for IPv4 UDP encapsulation support. 1854 This flag is applicable only when the flag 1855 UseIPv4UDPEncapForSignalingMessages is set to a value of 1. 1857 6. IANA Considerations 1859 This document defines a new Mobility Header option, IPv4 Default 1860 Router Address option. This option is described in Section 3.3.1. 1861 The Type value for this option needs to be assigned from the same 1862 number space as allocated for the other mobility options, as defined 1863 in [RFC-3775]. 1865 This document also defines new status values, used in Proxy Binding 1866 Acknowledgement message, as described in Section 3.3.2. These values 1867 are to be assigned from the same number space as allocated for other 1868 Status codes [RFC-3775]. Each of these allocated values have to be 1869 greater than 128. 1871 7. Security Considerations 1873 All the security considerations from the base Proxy Mobile IPv6 [RFC- 1874 5213], Mobile IPv6 [RFC-3775], and Dual-Stack Mobile IPv6 [ID-DSMIP6] 1875 apply when using the extensions defined in this document. 1876 Additionally, the following security considerations need to be 1877 applied. 1879 This document defines news mobility options for supporting the IPv4 1880 Home Address assignment and IPv4 Transport Support features. These 1881 options are to be carried in Proxy Binding Update and Proxy Binding 1882 Acknowledgement messages. The required security mechanisms specified 1883 in the base Proxy Mobile IPv6 protocol for protecting these signaling 1884 messages are sufficient when carrying these mobility options. 1886 This specification describes the use of IPv4 transport for exchanging 1887 the signaling messages between the local mobility anchor and the 1888 mobile access gateway. These signaling messages are fundamentally 1889 IPv6 messages, but encapsulated in an IPv4 header and routed as IPv4 1890 packets. The encapsulated inner IPv6 message is still protected 1891 using IPsec, using the established security association and this 1892 offers the same level of security as when the messages are routed 1893 natively as IPv6 packets. The use of outer IPv4 header does not 1894 introduce any new security vulnerabilities. 1896 8. Contributors 1898 This document reflects discussions and contributions from several 1899 people (in alphabetical order): 1901 Kuntal Chowdhury 1903 kchowdhury@starentnetworks.com 1905 Vijay Devarapalli 1907 vijay.devarapalli@azairenet.com 1909 Sangjin Jeong 1911 sjjeong@etri.re.kr 1913 Basavaraj Patil 1915 basavaraj.patil@nsn.com 1917 Myungki Shin 1919 myungki.shin@gmail.com 1921 9. Acknowledgments 1923 The IPv4 support for Proxy Mobile IPv6 was initially covered in the 1924 internet-draft [draft-sgundave-mip6-proxymip6-02.txt]. We would like 1925 to thank all the authors of the document and acknowledge that initial 1926 work. 1928 Thanks to Alper Yegin, Behcet Sarikaya, Bernard Aboba, Charles 1929 Perkins, Damic Damjan, Jari Arkko, Joel Hortelius, Jonne Soinnen, 1930 Julien Laganier, Mohana Jeyatharan, Niklas Nuemann, Premec Domagoj, 1931 Ralph Droms, Sammy Touati, Vidya Narayanan, Yingzhe Wu and Zu Qiang 1932 for their helpful review of this document. 1934 10. References 1936 10.1. Normative References 1938 [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate 1939 Requirement Levels", BCP 14, RFC 2119, March 1997. 1941 [RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 1942 2131, March 1997. 1944 [RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in 1945 IPv6", RFC 3775, June 2004. 1947 [RFC-4193] Hinden, R. and Haberman, B., "Unique Local IPv6 Unicast 1948 Addresses", RFC-4193, October 2005. 1950 [RFC-4291] Hinden, R. and Deering, S., "IP Version 6 Addressing 1951 Architecture", RFC-4291, February 2006. 1953 [RFC-5213] Gundavelli, S., et.al, "Proxy Mobile IPv6", RFC 5213, 1954 November 2007. 1956 [ID-DSMIP6] Soliman, H. et al, "Mobile IPv6 support for dual stack 1957 Hosts and Routers (DSMIPv6)", 1958 draft-ietf-mext-nemo-v4traversal-10.txt, April 2009. 1960 [ID-GREKEY-NEGO] Muhanna, A., Khalil, M., Gundavelli, S., Leung, K., 1961 "GRE Key Option for Proxy Mobile IPv6", 1962 draft-ietf-netlmm-grekey-option-06.txt, February 2009. 1964 10.2. Informative References 1966 [RFC-1332] G. McGregor, "The PPP Internet Protocol Control Protocol 1967 (IPCP)", RFC 1332, May 1992. 1969 [RFC-1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1970 and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1971 1918, February 1996. 1973 [RFC-2132] Alexander, S. & Droms, R., "DHCP Options and BOOTP Vendor 1974 Extensions", RFC 2132, March 1997. 1976 [RFC-3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1977 Address Translator (Traditional NAT)", RFC 3022, January 2001. 1979 [RFC-3046] M. Patrick, "DHCP Relay Agent Information Option", January 1980 2001. 1982 [RFC-3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global 1983 Unicast Address Format", RFC 3587, August 2003. 1985 [RFC-3948] Huttunen, A. et al, "UDP Encapsulation of IPsec ESP 1986 Packets", RFC 3948, January 2005. 1988 [RFC-4301] Kent, S. and K. Seo, "Security Architecture for the 1989 Internet Protocol", RFC 4301, December 2005. 1991 [RFC-4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 1992 4306, December 2005. 1994 [RFC-4436] Aboba, B., Carlson, J. and S.Cheshire, "Detecting Network 1995 Attachment in IPv4", RFC 4436, March 2006. 1997 [RFC-4977] Tsirtsis, G., Soliman, H., "Problem Statement: Dual Stack 1998 Mobility", RFC 4977, August 2007. 2000 [RFC-5107] R. Johnson and J. Jumarasamy and K. Kinnear and M. Stapp, 2001 "DHCP Server Identifier Override Suboption", RFC 5107, February 2008. 2003 Authors' Addresses 2005 Ryuji Wakikawa 2006 Toyota ITC / Keio University 2007 6-6-20 Akasaka, Minato-ku 2008 Tokyo 107-0052 2009 Japan 2011 Phone: +81-3-5561-8276 2012 Fax: +81-3-5561-8292 2013 Email: ryuji@jp.toyota-itc.com 2015 Sri Gundavelli 2016 Cisco 2017 170 West Tasman Drive 2018 San Jose, CA 95134 2019 USA 2021 Email: sgundave@cisco.com