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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MEXT Working Group R. Wakikawa (Ed.) 3 Internet-Draft Toyota ITC 4 Intended status: Standards Track V. Devarapalli 5 Expires: October 22, 2009 Wichorus 6 G. Tsirtsis 7 Qualcomm 8 T. Ernst 9 INRIA 10 K. Nagami 11 INTEC NetCore 12 April 20, 2009 14 Multiple Care-of Addresses Registration 15 draft-ietf-monami6-multiplecoa-13.txt 17 Status of this Memo 19 This Internet-Draft is submitted to IETF in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 This Internet-Draft will expire on October 22, 2009. 40 Copyright Notice 42 Copyright (c) 2009 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents in effect on the date of 47 publication of this document (http://trustee.ietf.org/license-info). 48 Please review these documents carefully, as they describe your rights 49 and restrictions with respect to this document. 51 Abstract 53 According to the current Mobile IPv6 specification, a mobile node may 54 have several care-of addresses, but only one, called the primary 55 care-of address, that can be registered with its home agent and the 56 correspondent nodes. However, for matters of cost, bandwidth, delay, 57 etc, it is useful for the mobile node to get Internet access through 58 multiple accesses simultaneously, in which case the mobile node would 59 be configured with multiple active IPv6 care-of addresses. This 60 document proposes extensions to the Mobile IPv6 protocol to register 61 and use multiple care-of addresses. The extensions proposed in this 62 document can be used by Mobile Routers using the NEMO (Network 63 Mobility) Basic Support protocol as well. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 71 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 73 4. Mobile IPv6 Extensions . . . . . . . . . . . . . . . . . . . . 13 74 4.1. Binding Cache Structure and Binding Update List . . . . . 13 75 4.2. Binding Update Message . . . . . . . . . . . . . . . . . . 13 76 4.3. Binding Identifier Mobility Option . . . . . . . . . . . . 14 77 4.4. New Status Values for Binding Acknowledgement . . . . . . 15 79 5. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 18 80 5.1. Management of Care-of Address(es) and Binding 81 Identifier(s) . . . . . . . . . . . . . . . . . . . . . . 18 82 5.2. Binding Registration . . . . . . . . . . . . . . . . . . . 18 83 5.3. Bulk Registration . . . . . . . . . . . . . . . . . . . . 19 84 5.4. Binding De-Registration . . . . . . . . . . . . . . . . . 20 85 5.5. Returning Home: Using Single Interface . . . . . . . . . . 20 86 5.5.1. Using only Interface attached to the Home Link . . . . 21 87 5.5.2. Using only Interface attached to the Visited Link . . 21 88 5.6. Returning Home: Simultaneous Home and Visited Link 89 Operation . . . . . . . . . . . . . . . . . . . . . . . . 21 90 5.6.1. Problems of Simultaneous Home and Foreign 91 Attachments . . . . . . . . . . . . . . . . . . . . . 21 92 5.6.2. Overview and Approach . . . . . . . . . . . . . . . . 22 93 5.6.3. Home Binding Support . . . . . . . . . . . . . . . . . 23 94 5.6.4. Sending Packets from the Home Link . . . . . . . . . . 23 95 5.6.5. Leaving from the Home Link . . . . . . . . . . . . . . 24 96 5.7. Receiving Binding Acknowledgement . . . . . . . . . . . . 24 97 5.8. Receiving Binding Refresh Request . . . . . . . . . . . . 25 98 5.9. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 26 100 6. Home Agent and Correspondent Node Operation . . . . . . . . . 27 101 6.1. Searching Binding Cache with Binding Identifier . . . . . 27 102 6.2. Processing Binding Update . . . . . . . . . . . . . . . . 27 103 6.3. Sending Binding Acknowledgement for home link 104 registration . . . . . . . . . . . . . . . . . . . . . . . 29 105 6.4. Sending Binding Refresh Request . . . . . . . . . . . . . 31 106 6.5. Receiving Packets from Mobile Node . . . . . . . . . . . . 31 108 7. Network Mobility Applicability . . . . . . . . . . . . . . . . 32 110 8. DSMIPv6 Applicability . . . . . . . . . . . . . . . . . . . . 33 111 8.1. IPv4 Care-of Address Registration . . . . . . . . . . . . 33 112 8.2. IPv4 Home Address Management . . . . . . . . . . . . . . . 34 114 9. IPsec and IKEv2 interaction . . . . . . . . . . . . . . . . . 36 115 9.1. Use of Care-of Address in the IKEv2 exchange . . . . . . . 36 116 9.2. Transport Mode IPsec protected messages . . . . . . . . . 37 117 9.3. Tunnel Mode IPsec protected messages . . . . . . . . . . . 37 118 9.3.1. Tunneled Home Test Init and Home Test messages . . . . 37 119 9.3.2. Tunneled Payload Traffic . . . . . . . . . . . . . . . 38 121 10. Security Considerations . . . . . . . . . . . . . . . . . . . 39 123 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 125 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 42 127 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42 128 13.1. Normative References . . . . . . . . . . . . . . . . . . . 42 129 13.2. Informative References . . . . . . . . . . . . . . . . . . 42 131 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44 133 1. Introduction 135 A mobile node may use various types of network interfaces to obtain 136 durable and wide area network connectivity. This has increasingly 137 become true with mobile nodes having multiple interfaces such as 138 802.2, 802.11, 802.16, cellular radios, etc. The motivations for and 139 benefits of using multiple points of attachment are discussed in [ID- 140 MOTIVATION]. When a mobile node with multiple interfaces uses Mobile 141 IPv6 [RFC-3775] for mobility management, it cannot use its multiple 142 interfaces to send and receive packets while taking advantage of 143 session continuity provided by Mobile IPv6. This is because Mobile 144 IPv6 allows the mobile node to only bind one care-of address at a 145 time with its home address. See [ID-MIP6ANALYSIS] for a further 146 analysis of using multiple interfaces and addresses with Mobile IPv6. 148 This document proposes extensions to Mobile IPv6 to allow a mobile 149 node to register multiple care-of addresses for a home address and 150 create multiple binding cache entries. A new Binding Identification 151 (BID) number is created for each binding the mobile node wants to 152 create and sent in the Binding Update. The home agent that receives 153 this Binding Update creates a separate binding for each BID. The BID 154 information is stored in the corresponding binding cache entry. The 155 BID information can now be used to identify individual bindings. The 156 same extensions can also be used in Binding Updates sent to the 157 correspondent nodes. 159 2. Terminology 161 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 162 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 163 document are to be interpreted as described in [RFC-2119]. 165 Terms used in this draft are defined in [RFC-3775], [RFC-3753] and 166 [RFC-4885]. In addition to or as a replacement of these, the 167 following terms are defined or redefined: 169 Binding Identification number (BID) 171 The BID is an identification number used to distinguish multiple 172 bindings registered by the mobile node. Assignment of distinct 173 BIDs allows a mobile node to register multiple binding cache 174 entries for a given home address. The BIDs assigned to a same 175 home address must not be duplicated at a time. Zero value is 176 reserved for future extension. Each BID is generated and managed 177 by a mobile node. The BID is stored in the binding update List 178 and is sent by the mobile node in the Binding Update. A mobile 179 node may change the value of a BID at any time according to its 180 administrative policy, for instance to protect its privacy. An 181 implementation must carefully assign the BID so as to keep using 182 the same BID for the same binding even when the status of the 183 binding is changed. More details can be found in Section 5.1. 185 Binding Identifier Mobility Option 187 The Binding Identifier mobility option is used to carry the BID 188 information. 190 Bulk Registration 192 A mobile node can register multiple bindings at once by sending a 193 single Binding Update. A mobile node can also replace some or all 194 the bindings available at the home agent with the new bindings by 195 using the bulk registration. Bulk registration is supported only 196 for home registration (i.e. with the home agent) as explained in 197 Section 5.3. A mobile node must not perform bulk registration 198 mechanism described in this specification with a correspondent 199 node. 201 3. Protocol Overview 203 A new extension called the Binding identification number (BID) is 204 introduced to distinguish between multiple bindings pertaining to the 205 same home address. If a mobile node configures several IPv6 global 206 addresses on one or more of its interfaces, it can register these 207 addresses with its home agent as care-of addresses. If the mobile 208 node wants to register multiple bindings, it MUST generate a BID for 209 each care-of address and store the BID in the binding update list. A 210 mobile node can manipulate each binding independently by using the 211 BIDs. The mobile node then registers its care-of addresses by 212 sending a Binding Update with a Binding Identifier mobility option. 213 The BID is included in the Binding Identifier mobility option. After 214 receiving the Binding Update with a Binding Identifier mobility 215 option, the home agent MUST copy the BID from the Binding Identifier 216 mobility option to the corresponding field in the binding cache 217 entry. If there is an existing binding cache entry for the mobile 218 node, and if the BID in the Binding Update does not match the one 219 with the existing entry, the home agent MUST create a new binding 220 cache entry for the new care-of address and BID. The mobile node can 221 register multiple care-of addresses either independently in 222 individual Binding Updates or multiple at once in a single Binding 223 Update. 225 If the mobile host wishes to register its binding with a 226 correspondent node, it must perform return routability operations as 227 described in [RFC-3775]. This includes managing a Care-of Keygen 228 token per care-of address and exchanging Care-of Test Init and 229 Care-of Test message with the correspondent node for each care-of 230 address. The mobile node MAY use the same BID that it used with the 231 home agent for a particular care-of address. For protocol 232 simplicity, bulk registration to correspondent nodes is not supported 233 in this document. This is because the Return Routability mechanism 234 introduced in [RFC-3775] cannot be easily extended to verify multiple 235 care-of addresses stored in a single Binding Update. 237 Figure 1 illustrates the configuration where the mobile node obtains 238 multiple care-of addresses at foreign links. The mobile node can 239 utilize all the care-of addresses. In Figure 1, the home address of 240 the mobile node (MN) is 2001:db8::EUI. The mobile node has 3 241 different interfaces and possibly acquires care-of addresses 1-3 242 (CoA1, CoA2, CoA3). The mobile node assigns BID1, BID2 and BID3 to 243 each care-of address. 245 +----+ 246 | CN | 247 +--+-+ 248 | 249 +---+------+ +----+ 250 +------+ Internet |----------+ HA | 251 | +----+---+-+ +--+-+ 252 CoA2| | | | Home Link 253 +--+--+ | | ------+------ 254 | MN +--------+ | 255 +--+--+ CoA1 | 256 CoA3| | 257 +---------------+ 259 Binding Cache Database: 260 home agent's binding (Proxy neighbor advertisement is active) 261 binding [2001:db8::EUI BID1 care-of address1] 262 binding [2001:db8::EUI BID2 care-of address2] 263 binding [2001:db8::EUI BID3 care-of address3] 264 correspondent node's binding 265 binding [2001:db8::EUI BID1 care-of address1] 266 binding [2001:db8::EUI BID2 care-of address2] 267 binding [2001:db8::EUI BID3 care-of address3] 269 Figure 1: Multiple Care-of Address Registration 271 If the mobile node decides to act as a regular mobile node compliant 272 with [RFC-3775], it sends a Binding Update without any Binding 273 Identifier mobility options. The receiver of the Binding Update 274 deletes all the bindings registering with a BID and registers only a 275 single binding for the mobile node. Note that the mobile node can 276 continue using the BID even if it has only a single binding that is 277 active. 279 Binding cache lookup is done based on the home address and BID 280 information if a BID is available. This is different from RFC 3775, 281 where only the home address is used for binding cache lookup. 282 Binding cache lookup is operated for either protocol signaling and 283 data packets. For the protocol signaling such as a Binding Update, 284 BID should be always carried by a BID sub-option in a protocol 285 signaling. Therefore, a correspondent binding cache that matches the 286 specified BID MUST be found from the binding cache database. On the 287 other hand, for the data packets, no BID information is carried in a 288 packet. The binding cache lookup may involve policy or flow filters 289 to retrieve a correspondent BID per packet in cases where some policy 290 or flow filters are used to direct a certain packet or flow to a 291 particular care-of address. However, the binding cache lookup using 292 policy or flow filters is out of scope for this document. If no such 293 mechanism is available and no BID is found for a packet, a node 294 SHOULD use the binding which was last verified by receiving data 295 packets or signaling from the mobile node. In case the binding cache 296 lookup for data packets, using the combination of home address and 297 BID, does not return a valid binding cache entry, the home agent 298 SHOULD perform the lookup based on only the home address as described 299 in [RFC-3775]. 301 In any case, to avoid problems with upper layer protocols and TCP in 302 particular, a single packet flow as identified by the 5-tuple SHOULD 303 only be sent to a single care-of address at a time. 305 The mobile node may return to the home link through one of its 306 interfaces. There are two options possible for the mobile node when 307 its returns home. Section 5.6 and Section 5.5.1 describe the 308 returning home procedures in more detail. 310 1. The mobile node uses only the interface with which it attaches to 311 the home link. This is illustrated in Figure 2. It de-registers 312 all bindings with the home agent related to all care-of 313 addresses. The interfaces still attached to the visited link(s) 314 are no longer going to be receiving any encapsulated traffic from 315 the home agent. On the other hand, the mobile node can continue 316 communicating with the correspondent node from the other 317 interfaces attached to foreign links by using route optimization. 318 Even if the mobile node is attached to the home link, it can 319 still send Binding Updates for other active care-of addresses 320 (CoA1 and CoA2) to correspondent nodes. Since the correspondent 321 node has bindings, packets are routed to each Care-of Addresses 322 directly. 324 +----+ 325 | CN | 326 +--+-+ 327 | 328 +---+------+ +----+ 329 +------+ Internet |----------+ HA | 330 | +----+-----+ +--+-+ 331 CoA2| | | Home Link 332 +--+--+ | --+---+------ 333 | MN +--------+ | 334 +--+--+ CoA1 | 335 | | 336 +---------------------------+ 338 Binding Cache Database: 339 home agent's binding 340 none 341 correspondent node's binding 342 binding [2001:db8::EUI BID1 care-of address1] 343 binding [2001:db8::EUI BID2 care-of address2] 345 Figure 2: Using only Interface Attached to Home Link 347 2. The mobile node may simultaneously use both the interface 348 attached to the home link and the interfaces still attached to 349 the visited link(s) as shown in Figure 3. There are two possible 350 topologies depending on whether the home agent is the only router 351 on the home link or not. The operation of Neighbor Discovery 352 [RFC-4861] is different in the two topologies. More details can 353 be found in Section 5.6. The home agent and the correspondent 354 node have the binding entries listed in Figure 3 in their binding 355 cache database in both topologies. The home agent also knows 356 that the mobile node is attached to the home link. All the 357 traffic from the Internet is intercepted by the home agent first 358 and routed to either the interface attached to the home link or 359 the one of the foreign links. How the home agent decides to 360 route a particular flow to the interface attached to the home 361 link or foreign link is out of scope in this document. 363 Topology-a) 364 +----+ 365 | CN | 366 +--+-+ 367 | 368 +---+------+ +----+ 369 +------+ Internet |----------+ HA | 370 | +----+-----+ +--+-+ 371 CoA2| | | Home Link 372 +--+--+ | --+---+------ 373 | MN +--------+ | 374 +--+--+ CoA1 | 375 | | 376 +---------------------------+ 378 Topology-b) 379 +----+ 380 | CN | 381 +--+-+ 382 | 383 +---+------+ Router +----+ 384 +------+ Internet |-------R | HA | 385 | +----+-----+ | +--+-+ 386 CoA2| | | | Home Link 387 +--+--+ | --+-+-------+------ 388 | MN +--------+ | 389 +--+--+ CoA1 | 390 | | 391 +---------------------------+ 393 Binding Cache Database: 394 home agent's binding 395 binding [2001:db8::EUI BID1 care-of address1] 396 binding [2001:db8::EUI BID2 care-of address2] 397 correspondent node's binding 398 binding [2001:db8::EUI BID1 care-of address1] 399 binding [2001:db8::EUI BID2 care-of address2] 401 Figure 3: Simultaneous Home and Visited Link Operation 403 This specification keeps backwards compatibility with [RFC-3775]. If 404 a receiver (either home agent or correspondent node) does not support 405 this specification, it does not understand the binding identifier 406 mobility option. The receiver skip the unknown mobility option (i.e. 407 Binding Identifier mobility option) and process the Binding Update as 408 defined in [RFC-3775]. In order to keep the backward compatibility 409 with [RFC-3775], when a mobile node sends a Binding Update message 410 with extensions described in this document, the receiver needs to 411 reflect the Binding Identifier mobility option in the Binding 412 Acknowledgement. If the mobile node finds no Binding Identifier 413 mobility options in the received Binding Acknowledgement, it assumes 414 the other end node does not support this specification. In such 415 case, the mobile node needs to fall back to the legacy RFC-3775 416 compliant mobile node. If it is the home registration, the mobile 417 node MAY try to discover another home agent supporting Binding 418 Identifier mobility option for the home registration. 420 4. Mobile IPv6 Extensions 422 This section summarizes the extensions to Mobile IPv6 necessary for 423 manage multiple bindings. 425 4.1. Binding Cache Structure and Binding Update List 427 The BID is required to be stored in the binding cache and binding 428 update list structure. 430 The sequence number value MUST be shared among all the binding update 431 list entries related to Binding Updates sent to a particular home 432 agent or correspondent node. Whenever a mobile node sends either an 433 individual or a bulk Binding Update, the sequence number is 434 incremented. When a home agent receives an individual Binding 435 Update, it should update the sequence number for all the bindings for 436 a particular mobile node with the sequence number in the received 437 Binding Update. 439 4.2. Binding Update Message 441 This specification extends the Binding Update message with a new 442 flag. The flag is shown and described below. 444 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 445 | Sequence # | 446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 447 |A|H|L|K|M|R|P|F|T|O| Reserved | Lifetime | 448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 | | 450 . . 451 . Mobility options . 452 . . 453 | | 454 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 Figure 4: Binding Update message 458 Overwrite (O) flag 460 When this flag is set, all the binding cache entries for a mobile 461 node are replaced by new entries registering with this Binding 462 Update message. This flag is only used when BID Mobility Option 463 is carried with Binding Update. 465 Reserved 467 6 bits Reserved field. 469 4.3. Binding Identifier Mobility Option 471 The Binding Identifier mobility option is included in the Binding 472 Update, Binding Acknowledgement, Binding Refresh Request, and Care-of 473 Test Init and Care-of Test message. The Binding Identifier Mobility 474 Option has an alignment requirement of 2n if the Care-of Address 475 field is not present. Otherwise, it has the alignment requirement of 476 8n + 2. 478 1 2 3 479 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 1 480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 | Type = TBD | Length | 482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 | Binding ID (BID) | Status |H| Reserved | 484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+ 485 + + 486 : IPv4 or IPv6 care-of address (CoA) : 487 + + 488 +---------------------------------------------------------------+ 490 Figure 5: BID Mobility Option 492 Type 494 Type value for Binding Identifier is TBD 496 Length 498 8-bit unsigned integer. Length of the option, in octets, 499 excluding the Type and Length fields. It MUST be set to either 4, 500 8, or 20 depending on the care-of address field. When the care-of 501 address is not carried by this option, the length value MUST be 502 set to 4. If the IPv4 care-of address is stored in the care-of 503 address field, the length MUST be 8. Otherwise, the Length value 504 MUST be set to 20 for IPv6 care-of address. 506 Binding ID (BID) 508 The BID which is assigned to the binding indicated by the care-of 509 address in the Binding Update or the Binding Identifier mobility 510 option. The BID is a 16-bit unsigned integer. The value of zero 511 is reserved and MUST NOT be used. 513 Status 515 The Status field is an 8-bit unsigned integer. When the Binding 516 Identifier mobility option is included in a Binding 517 Acknowledgement, this field overwrites the status field in the 518 Binding Acknowledgement only for this BID. If this field is set 519 to zero, the receiver ignores this field and uses the registration 520 status stored in the Binding Acknowledgement message. The 521 receiver MUST ignore this field if the Binding Identifier mobility 522 option is not carried within either the Binding Acknowledgement or 523 the Care-of Test messages. The possible status codes are the same 524 as the status codes of Binding Acknowledgement. This Status field 525 is also used to carry error information related to the care-of 526 address test in the Care-of Test message. 528 Simultaneous Home and Foreign Binding (H) flag 530 This flag indicates that the mobile node registers multiple 531 bindings to the home agent while is attached to the home link. 532 This flag is valid only for a Binding Update sent to the home 533 agent. 535 Reserved 537 7 bits Reserved field. The value MUST be initialized to zero by 538 the sender, and SHOULD be ignored by the receiver. 540 Care-of Address 542 If a Binding Identifier mobility option is included in a Binding 543 Update for the home registration, either IPv4 or IPv6 care-of 544 address for the corresponding BID can be stored in this field. 545 For the binding registration to correspondent nodes (i.e. route 546 optimization), only IPv6 care-of address can be stored in this 547 field. If no address is specified in this field, the length of 548 this field MUST be zero (i.e. not appeared in the option). If the 549 option is included in any other messages than a Binding Update, 550 the length of this field MUST be also zero. 552 4.4. New Status Values for Binding Acknowledgement 554 New status values for the status field in a Binding Acknowledgement 555 are defined for handling the multiple Care-of Addresses registration: 557 MCOA NOTCOMPLETE (TBD less than 128) 558 In bulk registration, not all the binding identifier mobility 559 options were successfully registered. Some of them were rejected. 560 The error status value of the failed mobility option is 561 individually stored in the status field of the binding identifier 562 mobility option. 564 MCOA RETURNHOME WO/NDP (TBD less than 128) 566 When a mobile node returns home, it MUST NOT use Neighbor 567 Discovery Protocol (NDP) for the home address on the home link. 568 This is explained in more detail in Section 5.6 570 MCOA MALFORMED (TBD more than 128) 572 Registration failed because Binding Identifier mobility option was 573 not formatted correctly. This value is used in the following 574 cases. 576 * when the wrong length value is specified (neither 4, 8 nor 20) 577 in the length field of the Binding Identifier mobility option. 579 * when a unicast routable address is not specified in the care-of 580 address field of the Binding Identifier mobility option. 582 * when a care-of address is not appeared in the care-of address 583 field of the Binding Identifier mobility option stored in an 584 IPsec ESP protected Binding Update. 586 MCOA NON-MCOA BINDING EXISTS (TBD more than 128) 588 It indicates that a bootstrapping multiple care-of address 589 registration was performed without the 'O' flag set. 591 MCOA UNKOWN COA(TBD more than 128) 593 It indicates that a Binding Identifier Mobility Option did not 594 include a Care-of address field and the receiver has no record for 595 the Binding ID indicated in the same option. 597 MCOA PROHIBITED(TBD more than 128) 599 It implies the multiple care-of address registration is 600 administratively prohibited. 602 MCOA BULK REGISTRATION PROHIBITED(TBD more than 128) 603 Bulk binding registration is not either permitted or supported. 604 Note that the bulk registration is an optional procedure and might 605 not be available on a home agent. 607 MCOA SIMULTANEOUS HOME AND FOREIGN PROHIBITED (TBD more than 128) 609 Simultaneous home and foreign attachment is neither supported nor 610 permitted. 612 5. Mobile Node Operation 614 5.1. Management of Care-of Address(es) and Binding Identifier(s) 616 There are two cases when a mobile node might acquire several care-of 617 addresses. A mixture of the two cases is also possible. Note that a 618 mobile node can use BID regardless of the number of interfaces and 619 care-of addresses. Whether a mobile node uses BID or not is 620 determined by a local configuration. 622 1. A mobile node is using several physical network interfaces and 623 acquires a care-of address on each of its interfaces. 625 2. A mobile node uses a single physical network interface, but 626 receives advertisements for multiple prefixes on the link the 627 interface is attached to. This will result in the mobile node 628 configuring several global addresses on the interface from each 629 of the announced prefixes. 631 The difference between the above two cases is only in the number of 632 physical network interfaces and therefore irrelevant in this 633 document. What is of significance is the fact that the mobile node 634 has several addresses it can use as care-of addresses. 636 A mobile node assigns a BID to each care-of address when it wants to 637 register them simultaneously with its home address. The BID MUST be 638 unique for a given home address. The value is an integer between 1 639 and 65535. Zero value SHOULD NOT be used as BIDs. If a mobile node 640 has only one care-of address, the assignment of a BID is not needed 641 until it has multiple care-of addresses to register with, at which 642 time all of the care-of addresses MUST be mapped to BIDs. 644 When a mobile node registers a given BID for the first time it MUST 645 include the care of address field in the Binding Identifier mobility 646 option. For any subsequent registrations that either re-register or 647 de-register the same BID, the MN SHOULD NOT include the care of 648 address field in the Binding Identifier mobility option. 650 5.2. Binding Registration 652 For the multiple Care-of Addresses registration, the mobile node MUST 653 include a Binding Identifier mobility option(s) in the Binding Update 654 as shown in Figure 6. 656 When IPsec ESP is used for protecting the Binding Update, a care-of 657 address MUST be carried in an alternate care-of address mobility 658 option as described in [RFC-4877]. However, in this specification, 659 the care-of address MUST be carried in the Care-of Address field of 660 the Binding Identifier mobility option. In order to save bits of the 661 Binding Update, the alternate care-of address option MUST NOT be 662 included. 664 For binding registration to a correspondent node, the mobile node 665 MUST have both active Home and Care-of Keygen tokens for Kbm (see 666 Section 5.2.5 of [RFC-3775]) before sending the Binding Update. The 667 care-of Keygen tokens MUST be maintained for each care-of address 668 that the mobile node wants to register to the correspondent node. 669 The Binding Update to the correspondent node is protected by the 670 Binding Authorization Data mobility option that is placed after the 671 Binding Identifier mobility option. 673 IPv6 header (src=Care-of Address, dst=Home Agent Address) 674 IPv6 Home Address Option 675 ESP Header* 676 Mobility header 677 Binding Update 678 Mobility Options 679 Binding Identifier mobility option 680 Binding Authorization mobility option+ 681 (*) if necessary, for home registration 682 (+) if necessary, for route optimization 684 Figure 6: Binding Update for Binding Registration 686 If the mobile node wants to replace existing registered bindings on 687 the home agent with the single binding in the sent Binding Update, it 688 sets the 'O' flag. It the 'O' flag is not set then the binding will 689 be added to existing bindings in the home agent. The single binding 690 will be registered with the assigned BID. Section 6.2 describes this 691 registration procedure in detail. 693 5.3. Bulk Registration 695 Bulk registration is an optimization for binding multiple care-of 696 addresses to a home address using a single Binding Update. This is 697 very useful if the mobile node, for instance, does not want to send a 698 lot of signaling messages through an interface where the bandwidth is 699 scarce. This document specifies bulk registration only for the 700 mobile node's home registration. A mobile node performing bulk 701 registration with a correspondent node is out of scope. 703 To use bulk registration, the mobile node includes a Binding 704 Identifier Mobility option for each BID it wants to register in the 705 same Binding Update message. As with single registrations (see 706 Section 5.1), the care of address field is included for BID 707 registered for the first time. This is shown in Figure 7. The rest 708 of the fields and options in the Binding Update such as Lifetime, 709 Sequence Number, and the flags in the Binding Update are common 710 across all care-of addresses. 712 IPv6 header (src=Care-of Address, dst=Home Agent Address) 713 IPv6 Home Address Option 714 ESP Header 715 Mobility header 716 Binding Update 717 Mobility Options 718 Binding Identifier1 (including Care-of Address) 719 Binding Identifier2 (including Care-of Address) 720 Binding Identifier3 (no Care-of Address) 721 Binding IdentifierN (no Care-of Address) 723 : 725 Figure 7: Binding Update for Bulk Registration 727 As with regular registrations, if the mobile node wants to replace 728 existing registered bindings on the home agent with the multiple 729 bindings in the sent Binding Update, it sets the 'O' flag in the 730 Binding Update, otherwise the bindings are added to the existing 731 bindings in the home agent. 733 5.4. Binding De-Registration 735 When a mobile node decides to delete all the bindings for its home 736 address, it sends a regular de-registration Binding Update with 737 lifetime set to zero as defined in [RFC-3775]. The Binding 738 Identifier mobility option is not required. 740 If a mobile node wants to delete a particular binding(s) from its 741 home agent and correspondent nodes, the mobile node sends a Binding 742 Update with lifetime set to zero and includes a Binding Identifier 743 mobility option(s) with the BID(s) it wants to de-register. The 744 receiver will remove only the care-of address(es) that match(es) the 745 specified BID(s). Since de-registration attempts to remove a BID 746 that already exists, the care-of addresses field in each binding 747 identifier option can be omitted by the sender as defined in 748 Section 5.1. 750 5.5. Returning Home: Using Single Interface 752 The mobile node may return to the home link, by attaching to the home 753 link through one of its interfaces. When the mobile node wants to 754 return home, it should be configured with information on what 755 interface it needs to use. 757 5.5.1. Using only Interface attached to the Home Link 759 The mobile node returns home and de-registers all the bindings as 760 shown in Figure 2 and as defined in [RFC-3775]. After the de- 761 registration step, all the packets routed by the home agent are only 762 forwarded to the interface attached to the home link, even if there 763 are other active interfaces attached to the visited link(s). While 764 the mobile node de-registers all the bindings from the home agent, it 765 may continue registering bindings for interface(s) attached to 766 visited link(s) to the correspondent node as shown in Figure 2. 768 5.5.2. Using only Interface attached to the Visited Link 770 The mobile node returns home physically but shuts down the interface 771 attached to the home link. As a result, a mobile node does not 772 return home even though it attaches to the home link by one of 773 interfaces. Before shutting down the interface, any binding for the 774 care-of address previously associated with the interface should be 775 deleted as defined in . 777 In this scenario, despite the fact that the mobile node is connected 778 to its home link, all of its traffic is sent and received via the 779 home agent and its foreign links. 781 5.6. Returning Home: Simultaneous Home and Visited Link Operation 783 5.6.1. Problems of Simultaneous Home and Foreign Attachments 785 The mobile node returns home and continues using all the interfaces 786 attached to both foreign and home links as shown in Figure 3. 788 In [RFC-3775], the home agent intercepts packets meant for the mobile 789 node using Proxy Neighbor Discovery [RFC-4861] while the mobile node 790 is away from the home link. When the mobile node returns home, the 791 home agent deletes the binding cache and stops proxying for the home 792 address so that a mobile node can configure its home address on the 793 interface attached to the home link. In this specification, a mobile 794 node may return home, configure the home address on the interface 795 attached to the home link, but still use the interfaces attached to 796 the foreign links. In this case, a possible conflict arises when the 797 both the home agent and the mobile node try to defend the home 798 address. If the home agent stops proxying for the home address, the 799 packets are always routed to the interface attached to the home link 800 and are never routed to the interfaces attached to the visited links. 801 It is required to avoid the conflict between the home agent and the 802 mobile node, while still allowing the simultaneous use of home and 803 foreign links. The following describes the mechanism for achieving 804 this. 806 5.6.2. Overview and Approach 808 The home agent MUST intercept all the packets meant for the mobile 809 node whether the mobile node is attached to the home link or not and 810 decide whether to send the traffic directly to the home address on 811 the link or tunnel to the care-of address. 813 Two scenarios are illustrated in Figure 3, depending on whether the 814 Home Agent is the only router at the home link or not. The 815 difference is on who defends the home address by (Proxy) Neighbor 816 Discovery on the home link. 818 1. Mobile node defends the home address by the regular Neighbor 819 Discovery Protocol (illustrated as topology-a in Figure 3). The 820 home agent is the only router on the home link. Therefore the 821 home agent is capable of intercepting packets without relying on 822 the proxy Neighbor Discovery protocol and the mobile node can 823 manage the Neighbor Cache entry of the home address on the home 824 link as a regular IPv6 node. However, there is one limitation of 825 this scenario. If a correspondent node is located at the home 826 link, the home agent may not intercept the packets destined to 827 the mobile node. These packets are routed only via the home 828 link, but this is the most optimal path for the mobile node to 829 communicate with nodes on the home link. 831 2. If there are other routers on the home link apart from the home 832 agent, then it cannot be guaranteed that all packets meant for 833 the mobile node are routed to the home agent. In this case, the 834 mobile node MUST NOT operate the Neighbor Discovery protocol for 835 the home address on the home link. This allows the home agent to 836 keep using proxy neighbor discovery and thus it keeps receiving 837 all the packets sent to the mobile node's home address. If the 838 home agent, according to its local policy, needs to deliver 839 packets to the mobile node over the home link, an issue arises 840 with respect to how the home agent discovers the mobile node's 841 link local address. This specification uses the Mobility Header 842 Link-layer Address Option defined in [RFC-5268] in order to carry 843 the mobile node's link-layer address in the Binding Update. 844 Likewise, the mobile node would also know the link-layer address 845 of the default router address to send packets from the home link 846 without Neighbor Discovery. The link-layer address is used to 847 transmit packets from and to the mobile node on the home link. 848 The packets are transmitted without the Neighbor Discovery 849 protocol by constructing the link-layer header manually. This 850 operation is similar to Mobile IPv6 [RFC-3775] when a mobile node 851 sends a deregistration binding update to the home agent's link- 852 layer address in the operation for returning home. 854 5.6.3. Home Binding Support 856 When the home binding is used, the mobile node MUST send a 857 registering binding update with a Binding Identifier mobility option 858 whith H flag set. The lifetime MUST be set to a non-zero lifetime of 859 the home binding, and the care-of address MUST be set to the home 860 address. 862 The mobile node SHOULD include the Mobility Header Link-layer Address 863 Option [RFC-5268] to notify the mobile node's link-layer address to 864 the home agent, too. The option code of the Mobility Header Link- 865 layer Address option MUST be set to '2' (Link-layer Address of the 866 mobile node). This link-layer address is required for the home agent 867 to send the Binding Acknowledgement and to forward the mobile node's 868 packet. 870 According to [RFC-3775], the mobile node MUST start responding to 871 Neighbor Solicitation for its home address right after it sends the 872 deregistration Binding Update to the home agent. However, in this 873 specification, the mobile node MUST NOT respond to Neighbor 874 Solicitation before receiving a Binding Acknowledgement, since the 875 home agent may continue proxying for the home address. If the mobile 876 node receives [MCOA RETURNHOME WO/NDP (TBD)] status value in the 877 received Binding Acknowledgment, it MUST NOT respond to Neighbor 878 Solicitation even after the Binding Acknowledgement. 880 The management of the home binding is same as the binding management 881 described in this specification. The home binding can be included in 882 a bulk binding registration (Section 5.3). The MN SHOULD refresh the 883 lifetime of the home binding by sending appropriate Binding Updates 884 as with any other binding. 886 5.6.4. Sending Packets from the Home Link 888 o When the mobile node receives the Binding Acknowledgement with the 889 status value 'Binding Update Accepted' and the BID option, it can 890 configure its home address to the interface attached to the home 891 link and start operating Neighbor Discovery for the home address 892 on the home link. Packets can be transmitted from and to the 893 mobile node as if the mobile node is a regular IPv6 node. 895 o If the mobile node receives the status [MCOA RETURNHOME WO/NDP] in 896 the Binding Acknowledgement, it MUST NOT operate Neighbor 897 Discovery for the home address. When the mobile node sends 898 packets from the interface attached to the home link, it MUST 899 learn the link-layer address of the next hop (i.e. default router 900 of the mobile node). A mobile node learns the default router's 901 link-layer address from a Source Link-Layer Address option in 902 Router Advertisements. The mobile node sends packets directly to 903 the default router's link-layer address. This is done by 904 constructing the packet including a link-layer header with the 905 learned link-layer address of the default router. The home agent 906 also forwards the packet to the mobile node on the home link by 907 using the mobile node's link-layer address. The link-layer 908 address SHOULD be cached when the home agent received the 909 deregistration Binding Update message. Note that the default 910 router MUST NOT cache the mobile node's link-layer address in the 911 neighbor cache when it forwards the packet from the mobile node to 912 the home agent. 914 5.6.5. Leaving from the Home Link 916 When the mobile node detaches from the home link, it SHOULD 917 immediately send a Binding Update for one of active care-of address 918 with H flag unset. When the 'H' flag of BID option is unset in any 919 Binding Update, the home agent stop forwarding the mobile node's 920 packets to the home link. 922 5.7. Receiving Binding Acknowledgement 924 The verification of a Binding Acknowledgement is the same as Mobile 925 IPv6 (section 11.7.3 of [RFC-3775]). The operation for sending a 926 Binding Acknowledgement is described in Section 6.2. 928 If a mobile node includes a Binding Identifier mobility option in a 929 Binding Update with the 'A' flag set, a Binding Acknowledgement 930 SHOULD carry a Binding Identifier mobility option. According to 931 [RFC-3775], the receiver of the Binding Update ignores unknown 932 mobility options and processes the Binding Update without the unknown 933 mobility option. Therefore, if no such mobility option is included 934 in the Binding Acknowledgement in response to a Binding Update for 935 multiple care-of address registration, this indicates that the 936 originating node of the Binding Acknowledgement does not support 937 processing the Binding Identifier mobility option regardless of 938 status value. In such case, the receiver of the Binding Update may 939 create a regular binding. The mobile node then SHOULD no longer 940 attempt multiple care-of address registration with that node. If 941 this occurs with home registration the mobile node MAY attempt to 942 discover another home agent supporting Binding Identifier mobility 943 option for the home registration. 945 If a Binding Identifier mobility option is present in the received 946 Binding Acknowledgement, the mobile node checks the status field in 947 the option. If the status value in the Binding Identifier mobility 948 option is zero, the mobile node uses the value in the Status field of 949 the Binding Acknowledgement. Otherwise, it uses the value in the 950 Status field of the Binding Identifier mobility option. 952 If the status code is greater than or equal to 128, the mobile node 953 starts relevant operations according to the error code. Otherwise, 954 the mobile node assumes that the originator (home agent or 955 correspondent node) successfully registered the binding information 956 and BID for the mobile node. 958 o If the Status value is [MCOA PROHIBITED], the mobile node MUST 959 stop registering multiple bindings with the node that sent the 960 Binding Acknowledgement. 962 o If the Status value is [MCOA BULK REGISTRATION NOT SUPPORT], the 963 mobile node needs to stop using bulk registrations with the node 964 that sent the Binding Acknowledgement. It should assume that none 965 of the attempted registrations were successful. 967 o If [MCOA MALFORMED] is specified, it indicates that the binding 968 identifier mobility option is formatted wrongly presumably due to 969 a programming error or major packet corruption. . 971 o If [MCOA NON-MCOA BINDING EXISTS] is specified, it means that 972 there is non-MCoA binding entry in the receiver. The mobile node 973 MUST set 'O' flag so that all the registered bindings are replced 974 by an MCoA registration as described in Section 5.9. 976 o If [MCOA UNKNOWN COA] is specified, it means that the mobile node 977 sent a binding identifier mobility option without a care-off 978 address field but the receiver could not find an entry for the BID 979 indicated. If the mobile node is trying to deregister a BID, it 980 NEED NOT do anything further. If the mobile node is trying to 981 refresh a binding it SHOULD send a binding identifier mobility 982 option including the care-of address field. 984 5.8. Receiving Binding Refresh Request 986 The verification of a Binding Refresh Request is the same as in 987 Mobile IPv6 (section 11.7.4 of [RFC-3775]). The operation of sending 988 a Binding Refresh Request is described in Section 6.4. 990 If a mobile node receives a Binding Refresh Request with a Binding 991 Identifier mobility option, it indicates that the node sending the 992 Binding Refresh Request message is requesting the mobile node to send 993 a new Binding Update for the BID. The mobile node SHOULD then send a 994 Binding Update at least for the respective binding, as described in 995 Section 5.2 and Section 5.3. 997 5.9. Bootstrapping 999 When a mobile node bootstraps and registers multiple bindings for the 1000 first time, it MUST set the 'O' flag in the Binding Update message. 1001 If old bindings still exists at the home agent, the mobile node has 1002 no knowledge of which bindings still exist at the home agent. This 1003 scenario happens when a mobile node reboots and loses state regarding 1004 the registrations. If the 'O' flag is set, all the bindings are 1005 replaced by the new binding(s). 1007 6. Home Agent and Correspondent Node Operation 1009 6.1. Searching Binding Cache with Binding Identifier 1011 If either a correspondent node or a home agent has multiple bindings 1012 for a mobile node in their binding cache database, it can use any of 1013 the bindings to communicate with the mobile node. This section 1014 explains how to retrieve the desired binding for the binding 1015 management. This document does not provide any mechanism to select 1016 the suitable binding for forwarding data packets. 1018 A node which is either a correspondent node or a home agent SHOULD 1019 use both the home address and the BID as the search key of the 1020 binding cache if it knows the corresponding BID (example: when 1021 processing signaling messages). In the example below, if a node 1022 searches the binding with the home address and BID2, it gets binding2 1023 for this mobile node. 1025 binding1 [2001:db8::EUI, care-of address1, BID1] 1026 binding2 [2001:db8::EUI, care-of address2, BID2] 1027 binding3 [2001:db8::EUI, care-of address3, BID3] 1029 Figure 8: Searching the Binding Cache 1031 The node learns the BID when it receives a Binding Identifier 1032 mobility option. At that time, the node MUST look up its binding 1033 cache database with the home address and the BID retrieved from the 1034 Binding Update. If the node does not know the BID, it searches for a 1035 binding with only the home address. In such a case, the first 1036 matched binding is found. If the node does not desire to use 1037 multiple bindings for a mobile node, it can simply ignore the BID. 1039 6.2. Processing Binding Update 1041 If a Binding Update does not contain a Binding Identifier mobility 1042 option, its processing is the same as in [RFC-3775]. If the receiver 1043 already has multiple bindings for the home address, it MUST replace 1044 all the existing bindings with the received binding. If the [RFC- 1045 3775] Binding Update is for de-registration, the receiver MUST delete 1046 all existing bindings from its Binding Cache. 1048 If the Binding Update contains a Binding Identifier mobility 1049 option(s), it is first validated according to section 9.5.1 of [RFC- 1050 3775]. Then the receiver processes the Binding Identifier mobility 1051 option(s) as described in the following steps. 1053 o The length value is examined. The length value MUST be either 4, 1054 8, or 20 depending on the Care-of Address field. If the length is 1055 incorrect, the receiver MUST reject the Binding Update and returns 1056 the status value set to [MCOA MALFORMED]. 1058 o When the Length value is either 8 or 20, the care-of address MUST 1059 be present in the Binding Identifier mobility option. If the 1060 unicast routable address [RFC-3775] is not present in the care-of 1061 address field, the receiver MUST reject the Binding Identifier 1062 mobility option and returns the status value set to [MCOA 1063 MALFORMED]. 1065 o When multiple Binding Identifier mobility options are present in 1066 the Binding Update, it is treated as bulk registration. If the 1067 receiving node is a correspondent node, it MUST reject the Binding 1068 Update and returns the status value in the binding Acknowledgement 1069 set to [MCOA BULK REGISTRATION NOT SUPPORT]. 1071 o If the Lifetime field in the Binding Update is set to zero, the 1072 receiving node deletes the binding entry that corresponds to the 1073 BID in the Binding Identifier mobility option. If the receiving 1074 node does not have an appropriate binding for the BID, it MUST 1075 reject the Binding Update and send a Binding Acknowledgement with 1076 status set to 133 [not home agent for this mobile node]. 1078 o If the 'O' flag is set in the de-registering Binding Update, it is 1079 ignored. If the 'H' flag is set, the home agent stores a home 1080 address in the Care-of Address field of the binding cache entry. 1081 The home agent MUST follow the descriptions described in 1082 Section 5.6. 1084 o If the Lifetime field is not set to zero, the receiving node 1085 registers a binding with the specified BID as a mobile node's 1086 binding. The Care-of address is obtained from the Binding Update 1087 packet as follows: 1089 * If the Length value of the Binding Identifier mobility option 1090 is 20, the care-of address is copied the IPv6 address from the 1091 care-of address field in the Binding Identifier mobility 1092 option. 1094 * When the Length value is 8, the address MUST be the IPv4 valid 1095 address. How to obtain an IPv4 care-of address is described in 1096 Section 8. 1098 o Once the care-of address(es) have been retrieved from the Binding 1099 Update, the receiving nodes creates new binding(s). 1101 * If the 'O' flag is set in the Binding Update, the home agent 1102 removes all the existing bindings and registers the received 1103 binding(s). 1105 * If the 'O' flag is unset in the Binding Update and the receiver 1106 has a regular binding which does not have BID for the mobile 1107 node, it must not process the Binding Update. The receiver 1108 should sent a Binding Acknowledgement with status set to [MCOA 1109 NON-MCOA BINDING EXISTS]. 1111 * If the receiver already has a binding with the same BID but 1112 different care-of address, it MUST update the binding and 1113 respond with a Binding Acknowledgement with status set to 0 1114 [Binding Update accepted]. 1116 * If the receiver does not have a binding entry for the BID, it 1117 registers a new binding for the BID and responds with a Binding 1118 Acknowledgement with status set to 0 [Binding Update accepted]. 1120 If all the above operations are successfully completed, a Binding 1121 Acknowledgement containing the Binding Identifier mobility options 1122 MUST be sent to the mobile node. Whenever a Binding Acknowledgement 1123 is sent, all the Binding Identifier mobility options stored in the 1124 Binding Update MUST be copied to the Binding Acknowledgement except 1125 the status field. The Care-of address field in each Binding 1126 Identifier mobility option, however, MAY be omitted, because the 1127 mobile node can match a corresponding binding update list entry using 1128 the BID. 1130 When a correspondent node sends a Binding Acknowledgement, the status 1131 value MUST be always stored in the Status field of the Binding 1132 Acknowledgement and the Status field of Binding Identifier mobility 1133 option MUST be always set to zero. 1135 When the home agent sends a Binding Acknowledgement, the status value 1136 can be stored in the Status field of either a Binding Acknowledgement 1137 or a Binding Identifier mobility option. If the status value is 1138 specific to one of bindings in the bulk registration, the status 1139 value MUST be stored in the Status field in the corresponding Binding 1140 Identifier mobility option. In this case, the Status field of the 1141 Binding Acknowledgement MUST be set to [MCOA NOTCOMPLETE], so that 1142 the receiver can examine the Status field of each Binding Identifier 1143 mobility option for further operations. Otherwise, the status field 1144 of the Binding Identifier mobility option MUST be set to zero and the 1145 home agent status field of the Binding Acknowledgement is used. 1147 6.3. Sending Binding Acknowledgement for home link registration 1149 The operations described in this section are related to the returning 1150 home using simultaneous use of home and foreign links. 1152 o When the home agent sends the Binding Acknowledgement after 1153 successfully processing the home binding registration, it MUST set 1154 the status value to either 0 [Binding Update Accepted] or to [MCOA 1155 RETURNHOME WO/NDP (TBD)] in the Status field of the Binding 1156 Acknowledgment depending on home agent configuration at the home 1157 link. The new values are: 1159 * Binding Update Accepted (0): Neighbor Discovery Protocol is 1160 permitted for the home address at the home link. This is 1161 regular returning home operation of [RFC-3775] 1163 * MCOA RETURNHOME WO/NDP (TBD): Neighbor Discovery Protocol is 1164 prohibited for the home address at the home link 1166 The respective Binding Identifier mobility options need to be 1167 included in the Binding Acknowledgement. 1169 o If the Binding Update is rejected, the appropriate error value 1170 MUST be set in the status field. In this case, the home agent 1171 operation is the same as [RFC-3775]. 1173 o Only if the home agent is certainly the only router in the home 1174 link, it MAY turn off Neighbor Discovery for the requested home 1175 address and responds with the [Binding Update Accepted] status 1176 value to the mobile node. Since the mobile node will not reply to 1177 Neighbor Solicitation for the home address before receiving the 1178 Binding Acknowledgement, the home agent SHOULD use the link-layer 1179 address carried by the Mobility Header Link-Layer Address option 1180 [RFC-5268] in the received Binding Update. After the completion 1181 of the home binding registration, the mobile node starts regular 1182 Neighbor Discovery operations for the home address on the home 1183 link. The neighbor cache entry for the home address is created by 1184 the regular exchange of Neighbor Solicitation and Neighbor 1185 Advertisement. 1187 o On the other hand, the home agent returns [MCOA RETURNHOME WO/NDP] 1188 value in the Status field of the Binding Identifier mobility 1189 option. The home agent learns the mobile node's link-layer 1190 address by receiving the Mobility Header link-layer address option 1191 carried by the Binding Update. It stores the link-layer address 1192 as a neighbor cache entry for the mobile node so that it can send 1193 the packets to the mobile node's link-layer address. 1195 o Note that the use of proxy Neighbor Discovery is an easier way to 1196 intercept the mobile nodes' packets instead of IP routing in some 1197 deployment scenarios. Therefore, even if a home agent is the only 1198 router, it is an implementation and operational choice whether the 1199 home agent returns [Binding Update Accepted] or [MCOA RETURNHOME 1200 WO/NDP]. 1202 o If BID option is not included in the Binding Acknowledgement, the 1203 home agent might not recognize the home registration. The home 1204 agent might have processed the home registration Binding Update as 1205 a regular de-registration as described in [RFC-3775] and deletes 1206 all the registered binding cache entries for the mobile node. 1207 Thus, the mobile node SHOULD stop using the interface attached to 1208 foreign link and use only the interface attached to the home link. 1210 6.4. Sending Binding Refresh Request 1212 When a node (home agent or correspondent node) sends a Binding 1213 Refresh Request for a particular binding created with the BID, the 1214 node SHOULD include the Binding Identifier mobility option in the 1215 Binding Refresh Request. The node MAY include multiple Binding 1216 Identifier mobility options if there are multiple bindings that need 1217 to be refreshed. 1219 6.5. Receiving Packets from Mobile Node 1221 When a node receives packets with a Home Address destination option 1222 from a mobile node, it MUST check that the care-of address that 1223 appears in the source address field of the IPv6 header MUST be equal 1224 to one of the care-of addresses in the binding cache entry. If no 1225 binding is found, the packets MUST be discarded. The node MUST also 1226 send a Binding Error message as specified in [RFC-3775]. This 1227 verification MUST NOT be done for a Binding Update. 1229 7. Network Mobility Applicability 1231 The binding management mechanisms are the same for a mobile host that 1232 uses Mobile IPv6 and for a mobile router that is using the NEMO Basic 1233 Support protocol [RFC-3963]. Therefore the extensions described in 1234 this document can also be used to support a mobile router with 1235 multiple care-of addresses. [RFC-4980] is a document for an analysis 1236 of NEMO multihoming. 1238 8. DSMIPv6 Applicability 1240 Dual Stack Mobile IPv6 (DSMIPv6) [ID-DSMIPv6] extends Mobile IPv6 to 1241 register an IPv4 care-of address instead of the IPv6 care-of address 1242 when the mobile node is attached to an IPv4-only access network. It 1243 also allows the mobile node to acquire an IPv4 home address in 1244 addition to an IPv6 home address for use with IPv4-only correspondent 1245 nodes. This section describes how the multiple care-of address 1246 registration works with IPv4 care-of and home addresses. 1248 8.1. IPv4 Care-of Address Registration 1250 The mobile node can use the extensions described in the document to 1251 register multiple care-of addresses, even if some of the care-of 1252 addresses are IPv4 address. 1254 Bulk registration MUST NOT be used for the initial binding 1255 registration from an IPv4 care-of address. This is because, the 1256 Binding Update and Binding Acknowledgement exchange is used to detect 1257 NAT on the path between the mobile node and the home agent. So the 1258 mobile node needs to check for a NAT between each IPv4 care-of 1259 address and the home agent. 1261 The Binding Update MUST be sent to the IPv4 home agent address by 1262 using UDP and IPv4 headers as shown in Figure 9. It is similar to 1263 [ID-DSMIPv6] except that the IPv4 care-of address option MUST NOT be 1264 used when the BID mobility option is used. 1266 IPv4 header (src=V4ADDR, dst=HA_V4ADDR) 1267 UDP Header 1268 IPv6 header (src=V6HoA, dst=HAADDR) 1269 ESP Header 1270 Mobility header 1271 -Binding Update 1272 Mobility Options 1273 - Binding Identifier (IPv4 CoA) 1274 *V4ADDR, HA_V4ADDR, V6HOA, HAADDR are defined in [ID-DSMIPv6] 1276 Figure 9: Initial Binding Update for IPv4 Care-of Address 1278 If a NAT is not detected, the mobile node can update the IPv4 care-of 1279 address by using bulk registration. The mobile node can register the 1280 IPv4 care-of address along with other IPv4 and IPv6 care-of 1281 addresses. Figure 10 shows the Binding Update format when the mobile 1282 node sends a Binding Update from one of its IPv6 care-of addresses. 1283 If the mobile node sends a Binding Update from IPv4 care-of address, 1284 it MUST follow the format described in Figure 9. Note that the IPv4 1285 Care-of Address must be registered by non bulk Binding registration, 1286 whenever it is changed. 1288 As shown in Figure 9, IPv4 care-of address will be appeared in 1289 Binding Identifier mobility option. The IPv4 care-of address 1290 mobility option defined in [ID-DSMIP6] MUST always be omitted. The 1291 receiver of the Binding Update message for an IPv4 care-of address 1292 MUST treat the IPv4 address stored in the Binding Identifier mobility 1293 option as the one in the IPv4 care-of address mobility option of [ID- 1294 DSMIP6]. If the IPv4 address in the Binding Identifier mobility 1295 option is different from one in the source address field in the IPv4 1296 header of the Binding Update (i.e. V4ADDR in Figure 9), the source 1297 address is used as an IPv4 care-of address. Otherwise, the IPv4 1298 address in the Binding Identifier mobility option is used as an IPv4 1299 care-of address. 1301 IPv6 header (src=Care-of Address, dst=Home Agent Address) 1302 IPv6 Home Address Option 1303 ESP Header 1304 Mobility header 1305 -Binding Update 1306 Mobility Options 1307 - Binding Identifier (IPv6/v4 CoA) 1308 - Binding Identifier (IPv6/v4 CoA) 1309 - ... 1311 Figure 10: Binding Bulk Registration for IPv4 care-of address 1313 When the home agent returns a Binding Acknowledgement for the IPv4 1314 care-of address registration, it SHOULD NOT use the IPv4 address 1315 Acknowledgement mobility option and SHOULD use only the Binding 1316 Identifier mobility option. The registration status for the IPv4 1317 Care-of address is stored in the Status field of the Binding 1318 Identifier mobility option. However, if the home agent needs to 1319 store the status value specially defined for the IPv4 address 1320 Acknowledgement mobility option, it MUST store the status value in 1321 the IPv4 address Acknowledgement mobility option and MUST NOT store 1322 it in Binding Identifier mobility option. In such case, the home 1323 agent MUST include both the IPv4 address Acknowledgement mobility 1324 option and Binding Identifier mobility option. 1326 8.2. IPv4 Home Address Management 1328 When the mobile node wants to configure an IPv4 home address in 1329 addition to the IPv6 home address, it can request for one using the 1330 IPv4 Home Address option in the Binding Update. If the home agent 1331 accepts the Binding Update, the mobile node can now register multiple 1332 care-of addresses for the IPv4 home address in addition to the IPv6 1333 home address. The mobile node MUST always use the IPv4 home address 1334 mobility option for any purposes of the IPv4 home address management. 1335 The same set of care-of addresses will be registered for both IPv6 1336 and IPv4 home addresses. The mobile node cannot bind a different set 1337 of care-of addresses to each home address. 1339 According to [ID-DSMIPv6], the home agent includes the IPv4 address 1340 Acknowledgement option in the Binding Acknowledgement only if the 1341 mobile node had requested for an IPv4 home address in the 1342 corresponding Binding Update. The IPv4 address Acknowledgement 1343 option MUST be present before any Binding Identifier mobility option. 1344 The status field of the IPv4 address Acknowledgement option contains 1345 only the error code defined in Section 4.2.1 of [ID-DSMIP6]. The 1346 home agent MUST always include the IPv4 address Acknowledgement 1347 mobility option in the Binding Acknowledgement for the IPv4 home 1348 address registration. 1350 9. IPsec and IKEv2 interaction 1352 Mobile IPv6 [RFC-3775] and the NEMO protocol [RFC-3963] require the 1353 use of IPsec to protect signaling messages including Binding Updates, 1354 Binding Acknowledgement and return routability messages. IPsec may 1355 also be used protect all tunneled data traffic. The Mobile IPv6- 1356 IKEv2 specification [RFC-4877] specifies how IKEv2 can be used to 1357 setup the required IPsec security associations. The following 1358 assumptions were made in [RFC-3775], [RFC-3963] and [RFC-4877] with 1359 respect to the use of IKEv2 and IPsec. 1361 o There is only one primary care-of address per mobile node. 1363 o The primary care-of address is stored in the IPsec database for 1364 tunnel encapsulation and decapsulation. 1366 o When the home agent receives a packet from the mobile node, the 1367 source address is verified against the care-of address in the 1368 corresponding binding cache entry. If the packet is a reverse 1369 tunneled packet from the mobile node, the care-of address check is 1370 done against the source address on the outer IPv6 header. The 1371 reverse tunnel packet could either be a tunneled Home Test Init 1372 message or tunneled data traffic to the correspondent node. 1374 o The mobile node runs IKEv2 (or IKEv1) with the home agent using 1375 the care-of address. The IKE SA is based on the care-of address 1376 of the mobile node. 1378 The above assumptions may not be valid when multiple care-of 1379 addresses are used by the mobile node. In the following sections, 1380 the main issues with the use of multiple care-of address with IPsec 1381 are addressed. 1383 9.1. Use of Care-of Address in the IKEv2 exchange 1385 For each home address the mobile node sets up security associations 1386 with the home agent, the mobile node must pick one care-of address 1387 and use that as the source address for all IKEv2 messages exchanged 1388 to create and maintain the IPsec security associations associated 1389 with the home address. The resultant IKEv2 security association is 1390 created based on this care-of address. 1392 If the mobile node needs to change the care-of address, it just sends 1393 a Binding Update with the care-of address it wants to use, with the 1394 corresponding Binding Identifier mobility option, and with the 'K' 1395 bit set. This will force the home agent to update the IKEv2 security 1396 association to use the new care-of address. If the 'K' bit is not 1397 supported on the mobile node or the home agent, the mobile node MUST 1398 re-establish the IKEv2 security association with the new care-of 1399 address. This will also result in new IPsec security associations 1400 being setup for the home address. 1402 9.2. Transport Mode IPsec protected messages 1404 For Mobile IPv6 signaling message protected using IPsec in transport 1405 mode, the use of a particular care-of address among multiple care-of 1406 addresses does not matter for IPsec processing. 1408 The home agent processes Mobile Prefix Discovery messages with the 1409 same rules of data packets described in Section 6.5. 1411 9.3. Tunnel Mode IPsec protected messages 1413 The use of IPsec in tunnel mode with multiple care-of address 1414 introduces a few issues that require changes to how the mobile node 1415 and the home agent send and receive tunneled traffic. The route 1416 optimization mechanism described in [RFC-3775] mandates the use of 1417 IPsec protection in tunnel mode for the Home Test Init and Home Test 1418 messages. The mobile node and the home agent may also choose to 1419 protect all reverse tunneled payload traffic with IPsec in tunnel 1420 mode. The following sections address multiple care-of address 1421 support for these two types of messages. 1423 9.3.1. Tunneled Home Test Init and Home Test messages 1425 The mobile node MAY use the same care-of address for all Home Test 1426 Init messages sent reverse tunneled through the home agent. The 1427 mobile node may use the same care-of address irrespective of which 1428 correspondent node the Home Test Init message is being sent. RFC 1429 3775 requires the home agent to verify that the mobile node is using 1430 the care-of address that is in the binding cache entry, when it 1431 receives a reverse tunneled Home Test Init message. If a different 1432 address is used as the source address, the message is silently 1433 dropped by the home agent. This document requires the home agent 1434 implementation to decapsulate and forward the Home Test Init message 1435 as long as the source address is one of the care-of addresses in the 1436 binding cache entry for the mobile node. 1438 When the home agent tunnels a Home Test message to the mobile node, 1439 the care-of address used in the outer IPv6 header is not relevant to 1440 the Home Test message. So regular IPsec tunnel encapsulation with 1441 the care-of address known to the IPsec implementation on the home 1442 agent is sufficient. 1444 9.3.2. Tunneled Payload Traffic 1446 When the mobile sends and receives multiple traffic flows protected 1447 by IPsec to different care-of addresses, the use of the correct 1448 care-of address for each flow becomes important. Support for this 1449 requires the following two considerations on the home agent. 1451 o When the home agent receives a reverse tunneled payload message 1452 protected by IPsec in tunnel mode, the source address used in the 1453 outer IPv6 header is irrelevant to IPsec, since the tunnel mode 1454 security association is based on the addresses in the inner IPv6 1455 header. Therefore, the same IPsec security association can be 1456 used for payload traffic tunneled from any of the care-of 1457 addresses. Note that the care-of address used in the reverse 1458 tunneld traffic can be different from the care-of address used as 1459 the source address in the IKEv2 exchange. However, this does not 1460 cause an issue due to the above mentioned reason. 1462 o For tunneled IPsec traffic from the home agent to the mobile node, 1463 the IPsec implementation on the home agent will not be aware of 1464 which care-of address to use when performing IPsec tunnel 1465 encapsulation. The Mobile IP stack on the home agent, based on 1466 the binding cache entries created by the mobile node, knows which 1467 care-of address the packet belonging to a particular flow needs to 1468 be tunneled to. The destination address for the outer IP header 1469 must either by conveyed dynamically per packet to the IPsec stack 1470 when it performs the encapsulation or the Mobile IPv6 stack must 1471 get access to the packet after IPsec processing is done and modify 1472 the destination address. The first option requires changes to the 1473 IPsec implementation. In the second option, there is a need for 1474 special processing in the forwarding function to replace the 1475 destination address on the outer header with the correct care-of 1476 address. The exact technique to achieve the above is 1477 implementation specific. 1479 10. Security Considerations 1481 The security considerations for securing the Binding Update and 1482 Binding Acknowledgement messages with multiple care-of address are 1483 very similar to the security considerations for securing the Binding 1484 Update and Binding Acknowledgement. Please see [RFC-3775] for more 1485 information. The Binding Update and binding Acknowledgement messages 1486 with multiple care-of addresses are securely exchanged as described 1487 in [RFC-3775], [RFC-4877] and Section 9. Additional security 1488 considerations are described below. 1490 With simultaneous binding support, it is possible for a malicious 1491 mobile node to successfully bind a number of victims' addresses as 1492 valid care-of addresses for the mobile node with its home agent. 1493 Once these addresses have been bound, the malicious mobile node can 1494 perform a re-direction attack by instructing the home agent (e.g. 1495 setting filtering rules to direct a large file transfer) to tunnel 1496 packets to the victims' addresses. Such risk is highlighted in [ID- 1497 MIP6ANALYSIS]. These attacks are possible because the care-of 1498 addresses sent by the mobile node in the Binding Update messages are 1499 not verified by the home agent, i.e., the home agent does not check 1500 if the mobile node is at the care-of address it is claiming to be. 1501 The security model for Mobile IPv6 assumes that there is a trust 1502 relationship between the mobile node and its home agent. Any 1503 malicious attack by the mobile node is traceable by the home agent. 1504 This acts as a deterrent for the mobile node to launch such attacks. 1506 Although such a risk exists in Mobile IPv6, the risk level is 1507 increased when simultaneous multiple care-of address bindings are 1508 performed. In Mobile IPv6, a mobile node can only have a single 1509 care-of address binding per home address at a given time. However, 1510 for simultaneous multiple care-of address bindings, a mobile node can 1511 have more than one care-of address binding per home address at a 1512 given time. This implies that a mobile node using simultaneous 1513 binding support can effectively bind more than a single victim's 1514 address. Another difference is the degree of risk involved. In the 1515 single care-of address binding case, once the re-direction attack is 1516 initiated, a malicious mobile node would be unable to use its home 1517 address for communications (such as to receive control packets 1518 pertaining to the file transfer). However, in the simultaneous 1519 binding support case, a malicious mobile node could bind a valid 1520 care-of address in addition to multiple victims addresses. This 1521 valid care-of address could then be used by the malicious mobile node 1522 to set up flow filtering rules at its home agent, thereby controlling 1523 and/or launching new re-direction attacks. 1525 Thus, in view of such risks, it is advisable for a home agent to 1526 employ some form of care-of address verification mechanism before 1527 using the care-of addresses as a valid routing path to a mobile node. 1528 These mechanisms are out-of scope for this document. 1530 In the binding registration of Mobile IPv6, a care-of address is 1531 always verified its reachability by a home agent. This reachability 1532 test may decrease the above risks. However, when bulk registration 1533 is used, a home agent cannot verify reachability of care-of addresses 1534 carried in a Binding Identifier mobility option. Therefore, the home 1535 agent can choose to reject bulk registration by using [MCOA BULK 1536 REGISTRATION PROHIBITED] in a Binding Acknowledgement. 1537 Alternatively, when a mobile node first registers a care-of address, 1538 it uses the individual binding updates for the first appeared care-of 1539 address. During the initial binding registration, a home agent can 1540 verify the address reachability for that given care-of address. 1541 After that, the mobile node uses bulk registration to refresh the 1542 care-of address. 1544 11. IANA Considerations 1546 The following Extension Types MUST be assigned by IANA: 1548 o Binding Identifier mobility option type: This must be assigned 1549 from the same space as mobility option in [RFC-3775]. 1551 o New Successful Status of Binding Acknowledgement: This status code 1552 must be assigned from the same space as binding acknowledgement 1553 status codes in [RFC-3775]. 1555 * MCOA NOTCOMPLETE (TBD) 1557 * MCOA RETURNHOME WO/NDP (TBD) 1559 o New Unsuccessful Status of Binding Acknowledgement: These status 1560 codes must also be assigned from the same space as Binding 1561 Acknowledgement status codes in [RFC-3775]. 1563 * MCOA MALFORMED (TBD) 1565 * MCOA NON-MCOA BINDING EXISTS (TBD) 1567 * MCOA PROHIBITED(TBD) 1569 * MCOA UNKNOWN COA(TBD) 1571 * MCOA BULK REGISTRATION PROHIBITED (TBD) 1573 * MCOA SIMULTANEOUS HOME AND FOREIGN PROHIBITED (TBD) 1575 12. Acknowledgements 1577 The authors would also like to thank Masafumi Aramoto, Keigo Aso, 1578 Julien Charbon, Tero Kauppinen, Benjamin Lim, Martti Kuparinen, 1579 Romain Kuntz, Heikki Mahkonen, Nicolas Montavont, Chan-Wah Ng for 1580 their discussions and inputs. Thanks to Susumu Koshiba, Hiroki 1581 Matutani, Koshiro Mitsuya, Koji Okada, Keisuke Uehara, Masafumi 1582 Watari and Jun Murai for earlier work on this subject. 1584 13. References 1586 13.1. Normative References 1588 [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate 1589 Requirement Levels", BCP 14, RFC 2119, March 1997. 1591 [RFC-4861] Narten, T., Nordmark, E., W. Simpson, and H. Soliman, 1592 "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September 1593 2007.. 1595 [RFC-3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 1596 in IPv6", RFC 3775, June 2004. 1598 [RFC-4877] V. Devarapalli, F. Dupont, "Mobile IPv6 Operation with 1599 IKEv2 and the Revised IPsec Architecture", RFC 4877, April 2007. 1601 [RFC-3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1602 Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, 1603 January 2005. 1605 [RFC-4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with 1606 IKEv2 and the revised IPsec Architecture", RFC 4877, April 2007. 1608 [ID-DSMIPv6] Soliman, H., "Mobile IPv6 support for dual stack Hosts 1609 and Routers (DSMIPv6)", draft-ietf-mext-nemo-v4traversal-07 (work in 1610 progress), December 2008. 1612 [RFC-5268] R. Koodli, "Mobile IPv6 Fast Handovers", RFC 5268, June 1613 2008. 1615 13.2. Informative References 1617 [ID-MOTIVATION] Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and 1618 K. Kuladinithi, "Motivations and Scenarios for Using Multiple 1619 Interfaces and Global Addresses", 1620 draft-ietf-monami6-multihoming-motivation-scenario-03 (work in 1621 progress), May 2008. 1623 [RFC-4980] Ng, C., Paik, Ernst, and C. Bagnulo, "Analysis of 1624 Multihoming in Network Mobility Support", RFC 4980, October 2007. 1626 [ID-MIP6ANALYSIS] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and 1627 K. Kuladinithi, "Analysis of Multihoming in Mobile IPv6", 1628 draft-ietf-monami6-mipv6-analysis-05 (Work in progress), May 2008. 1630 [ID-FLOWBINDING] H. Soliman, N. Montavont, N. Fikouras, and K. 1631 Kuladinithi, "Flow Bindings in Mobile IPv6 and Nemo Basic Support", 1632 draft-ietf-mext-flow-binding-01 (Work in progress), February 2009. 1634 [RFC-3753] Manner, J. and M. Kojo, "Mobility Related Terminology", 1635 RFC 3753, June 2004. 1637 [RFC-4306] C. Kaufman (Editor), "Internet Key Exchange (IKEv2) 1638 Protocol", RFC 4306, December 2005. 1640 [RFC-4885] Ernst, T. and H. Lach, "Network Mobility Support 1641 Terminology", RFC 4885, July 2007. 1643 Authors' Addresses 1645 Ryuji Wakikawa (Editor) 1646 TOYOTA InfoTechnology Center Co., Ltd. 1648 Email: ryuji.wakikawa@gmail.com (ryuji@jp.toyota-itc.com) 1650 Vijay Devarapalli 1651 Wichorus 1653 Email: vijay@wichorus.com 1655 George Tsirtsis 1656 Qualcomm 1658 Email: Tsirtsis@gmail.com 1660 Thierry Ernst 1661 INRIA 1663 Email: thierry.ernst@inria.fr 1665 Kenichi Nagami 1666 INTEC NetCore Inc. 1668 Email: nagami@inetcore.com