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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'AP-ID' is mentioned on line 1104, but not defined == Missing Reference: 'AR-Info' is mentioned on line 1104, but not defined ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3775 (Obsoleted by RFC 6275) ** Obsolete normative reference: RFC 4306 (Obsoleted by RFC 5996) -- Obsolete informational reference (is this intentional?): RFC 4068 (Obsoleted by RFC 5268) Summary: 4 errors (**), 0 flaws (~~), 3 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Koodli, Ed. 3 Internet-Draft Starent Networks 4 Updates: 5268 (if approved) February 14, 2009 5 Intended status: Standards Track 6 Expires: August 18, 2009 8 Mobile IPv6 Fast Handovers 9 draft-ietf-mipshop-rfc5268bis-00.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 August 18, 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 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. 46 Abstract 48 Mobile IPv6 enables a Mobile Node (MN) to maintain its connectivity 49 to the Internet when moving from one Access Router to another, a 50 process referred to as handover. During handover, there is a period 51 during which the Mobile Node is unable to send or receive packets 52 because of link switching delay and IP protocol operations. This 53 "handover latency" resulting from standard Mobile IPv6 procedures, 54 namely movement detection, new Care-of Address configuration, and 55 Binding Update, is often unacceptable to real-time traffic such as 56 Voice over IP (VoIP). Reducing the handover latency could be 57 beneficial to non-real-time, throughput-sensitive applications as 58 well. This document specifies a protocol to improve handover latency 59 due to Mobile IPv6 procedures. This document does not address 60 improving the link switching latency. 62 This documents updates the packet formats for the Handover Initiate 63 (HI) and Handover Acknowledgement (HAck) messages to Mobility Header 64 Type. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 71 3.1. Addressing the Handover Latency . . . . . . . . . . . . . 7 72 3.2. Protocol Operation . . . . . . . . . . . . . . . . . . . . 9 73 3.3. Protocol Operation during Network-Initiated Handover . . . 12 74 4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 13 75 5. Other Considerations . . . . . . . . . . . . . . . . . . . . . 17 76 5.1. Handover Capability Exchange . . . . . . . . . . . . . . . 17 77 5.2. Determining New Care-of Address . . . . . . . . . . . . . 17 78 5.3. Prefix Management . . . . . . . . . . . . . . . . . . . . 17 79 5.4. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 18 80 5.5. DAD Handling . . . . . . . . . . . . . . . . . . . . . . . 19 81 5.6. Fast or Erroneous Movement . . . . . . . . . . . . . . . . 20 82 6. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 21 83 6.1. New Neighborhood Discovery Messages . . . . . . . . . . . 21 84 6.1.1. Router Solicitation for Proxy Advertisement 85 (RtSolPr) . . . . . . . . . . . . . . . . . . . . . . 21 86 6.1.2. Proxy Router Advertisement (PrRtAdv) . . . . . . . . . 23 87 6.2. New Mobility Header Messages . . . . . . . . . . . . . . . 26 88 6.2.1. Inter - Access Router Messages . . . . . . . . . . . . 26 89 6.2.2. Fast Binding Update (FBU) . . . . . . . . . . . . . . 30 90 6.2.3. Fast Binding Acknowledgment (FBack) . . . . . . . . . 31 91 6.3. Unsolicited Neighbor Advertisement (UNA) . . . . . . . . . 33 92 6.4. New Options . . . . . . . . . . . . . . . . . . . . . . . 34 93 6.4.1. IP Address/Prefix Option . . . . . . . . . . . . . . . 34 94 6.4.2. Mobility Header IP Address/Prefix Option . . . . . . . 36 95 6.4.3. Link-Layer Address (LLA) Option . . . . . . . . . . . 37 96 6.4.4. Mobility Header Link-Layer Address (MH-LLA) Option . . 38 97 6.4.5. Binding Authorization Data for FMIPv6 (BADF) . . . . . 39 98 6.4.6. Neighbor Advertisement Acknowledgment (NAACK) . . . . 40 99 7. Related Protocol and Device Considerations . . . . . . . . . . 41 100 8. Evolution from and Compatibility with RFC 4068 . . . . . . . . 41 101 9. Configurable Parameters . . . . . . . . . . . . . . . . . . . 42 102 10. Security Considerations . . . . . . . . . . . . . . . . . . . 42 103 10.1. Peer Authorization Database Entries when Using IKEv2 . . . 44 104 10.2. Security Policy Database Entries . . . . . . . . . . . . . 45 105 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45 106 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47 107 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 47 108 13.1. Normative References . . . . . . . . . . . . . . . . . . . 47 109 13.2. Informative References . . . . . . . . . . . . . . . . . . 48 110 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 49 111 Appendix B. Changes since RFC 5268 . . . . . . . . . . . . . . . 49 112 Appendix C. Changes since RFC 4068 . . . . . . . . . . . . . . . 49 114 1. Introduction 116 Mobile IPv6 [RFC3775] describes the protocol operations for a mobile 117 node to maintain connectivity to the Internet during its handover 118 from one access router to another. These operations involve link- 119 layer procedures, movement detection, IP address configuration, and 120 location update. The combined handover latency is often sufficient 121 to affect real-time applications. Throughput-sensitive applications 122 can also benefit from reducing this latency. This document describes 123 a protocol to reduce the handover latency. 125 This specification addresses the following problems: how to allow a 126 mobile node to send packets as soon as it detects a new subnet link 127 and how to deliver packets to a mobile node as soon as its attachment 128 is detected by the new access router. The protocol defines IP 129 protocol messages necessary for its operation regardless of link 130 technology. It does this without depending on specific link-layer 131 features while allowing link-specific customizations. By definition, 132 this specification considers handovers that interwork with Mobile IP. 133 Once attached to its new access router, an MN engages in Mobile IP 134 operations including Return Routability [RFC3775]. There are no 135 special requirements for a mobile node to behave differently with 136 respect to its standard Mobile IP operations. 138 This specification is applicable when a mobile node has to perform IP 139 layer operations as a result of handovers. This specification does 140 not address improving the link switching latency. It does not modify 141 or optimize procedures related to signaling with the home agent of a 142 mobile node. Indeed, while targeted for Mobile IPv6, it could be 143 used with any mechanism that allows communication to continue despite 144 movements. Finally, this specification does not address bulk 145 movement of nodes using aggregate prefixes. 147 This document updates the header format for the Handover Initiate 148 (HI) and Handover Acknowledge (HAck) messages defined in [rfc5268]. 149 Both Proxy Mobile IPv6 protocol and Mobile IPv6 protocol use Mobility 150 Header (MH) as the type for carrying signaling related to route 151 updates. Even though the Fast Handover protocol uses Mobility Header 152 for Mobile Node signaling purposes, it has used ICMP for inter-access 153 router communication. Specifying Mobility Header for the HI and HAck 154 messages enables deployment of the protocol along-side PMIP6 and MIP6 155 protocols. Hence, this specification specifies the Mobility Header 156 formats for HI and HAck messages (Section 6.2.1) and the Mobility 157 Header option format for the IPv6 Address/Prefix option 158 (Section 6.4.2), and deprecates the use of ICMP for HI and HAck 159 messages. 161 2. Terminology 163 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 164 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 165 document are to be interpreted as described in RFC 2119 [RFC2119]. 166 The use of the term, "silently ignore" is not defined in RFC 2119. 167 However, the term is used in this document and can be similarly 168 construed. 170 The following terminology and abbreviations are used in this document 171 in addition to those defined in [RFC3775]. The reference handover 172 scenario is illustrated in Figure 1. 174 v +--------------+ 175 +-+ | Previous | < 176 | | ------------ | Access | ------- >-----\ 177 +-+ | Router | < \ 178 MN | (PAR) | \ 179 | +--------------+ +---------------+ 180 | ^ IP | Correspondent | 181 | | Network | Node | 182 V | +---------------+ 183 v / 184 v +--------------+ / 185 +-+ | New | < / 186 | | ------------ | Access | ------- >-----/ 187 +-+ | Router | < 188 MN | (NAR) | 189 +--------------+ 191 Figure 1: Reference Scenario for Handover 193 Mobile Node (MN): A Mobile IPv6 host. 195 Access Point (AP): A Layer 2 device connected to an IP subnet that 196 offers wireless connectivity to an MN. An Access Point Identifier 197 (AP-ID) refers the AP's L2 address. Sometimes, AP-ID is also 198 referred to as a Basic Service Set IDentifier (BSSID). 200 Access Router (AR): The MN's default router. 202 Previous Access Router (PAR): The MN's default router prior to its 203 handover. 205 New Access Router (NAR): The MN's anticipated default router 206 subsequent to its handover. 208 Previous CoA (PCoA): The MN's Care-of Address valid on PAR's 209 subnet. 211 New CoA (NCoA): The MN's Care-of Address valid on NAR's subnet. 213 Handover: A process of terminating existing connectivity and 214 obtaining new IP connectivity. 216 Router Solicitation for Proxy Advertisement (RtSolPr): A message 217 from the MN to the PAR requesting information for a potential 218 handover. 220 Proxy Router Advertisement (PrRtAdv): A message from the PAR to 221 the MN that provides information about neighboring links 222 facilitating expedited movement detection. The message can also 223 act as a trigger for network-initiated handover. 225 (AP-ID, AR-Info) tuple: Contains an access router's L2 and IP 226 addresses, and prefix valid on the interface to which the Access 227 Point (identified by AP-ID) is attached. The triplet [Router's L2 228 address, Router's IP address, and Prefix] is called "AR-Info". 229 See also Section 5.3. 231 Neighborhood Discovery: The process of resolving neighborhood AP- 232 IDs to AR-Info. 234 Assigned Addressing: A particular type of NCoA configuration in 235 which the NAR assigns an IPv6 address for the MN. The method by 236 which NAR manages its address pool is not specified in this 237 document. 239 Fast Binding Update (FBU): A message from the MN instructing its 240 PAR to redirect its traffic (toward NAR). 242 Fast Binding Acknowledgment (FBack): A message from the PAR in 243 response to an FBU. 245 Predictive Fast Handover: The fast handover in which an MN is able 246 to send an FBU when it is attached to the PAR, which then 247 establishes forwarding for its traffic (even before the MN 248 attaches to the NAR). 250 Reactive Fast Handover: The fast handover in which an MN is able 251 to send the FBU only after attaching to the NAR. 253 Unsolicited Neighbor Advertisement (UNA): The message in [RFC4861] 254 with 'O' bit cleared. 256 Fast Neighbor Advertisement (FNA): This message from RFC 4068 257 [RFC4068] is deprecated. The UNA message above is the preferred 258 message in this specification. 260 Handover Initiate (HI): A message from the PAR to the NAR 261 regarding an MN's handover. 263 Handover Acknowledge (HAck): A message from the NAR to the PAR as 264 a response to HI. 266 3. Protocol Overview 268 3.1. Addressing the Handover Latency 270 The ability to immediately send packets from a new subnet link 271 depends on the "IP connectivity" latency, which in turn depends on 272 the movement detection latency and the new CoA configuration latency. 273 Once an MN is IP-capable on the new subnet link, it can send a 274 Binding Update to its Home Agent and one or more correspondents. 275 Once its correspondents process the Binding Update successfully, 276 which typically involves the Return Routability procedure, the MN can 277 receive packets at the new CoA. So, the ability to receive packets 278 from correspondents directly at its new CoA depends on the Binding 279 Update latency as well as the IP connectivity latency. 281 The protocol enables an MN to quickly detect that it has moved to a 282 new subnet by providing the new access point and the associated 283 subnet prefix information when the MN is still connected to its 284 current subnet (i.e., PAR in Figure 1). For instance, an MN may 285 discover available access points using link-layer specific mechanisms 286 (e.g., a "scan" in Wireless Local Area Network (WLAN)) and then 287 request subnet information corresponding to one or more of those 288 discovered access points. The MN may do this after performing router 289 discovery or at any time while connected to its current router. The 290 result of resolving an identifier associated with an access point is 291 a [AP-ID, AR-Info] tuple, which an MN can use in readily detecting 292 movement. When attachment to an access point with AP-ID takes place, 293 the MN knows the corresponding new router's coordinates including its 294 prefix, IP address, and L2 address. The "Router Solicitation for 295 Proxy Advertisement (RtSolPr)" and "Proxy Router Advertisement 296 (PrRtAdv)" messages in Section 6.1 are used for aiding movement 297 detection. 299 Through the RtSolPr and PrRtAdv messages, the MN also formulates a 300 prospective new CoA (NCoA) when it is still present on the PAR's 301 link. Hence, the latency due to new prefix discovery subsequent to 302 handover is eliminated. Furthermore, this prospective address can be 303 used immediately after attaching to the new subnet link (i.e., NAR's 304 link) when the MN has received a "Fast Binding Acknowledgment 305 (FBack)" (see Section 6.2.3) message prior to its movement. In the 306 event it moves without receiving an FBack, the MN can still start 307 using NCoA after announcing its attachment through an unsolicited 308 Neighbor Advertisement message (with the 'O' bit set to zero) 309 [RFC4861]; NAR responds to this UNA message in case it wishes to 310 provide a different IP address to use. In this way, NCoA 311 configuration latency is reduced. 313 The information provided in the PrRtAdv message can be used even when 314 DHCP [RFC3315] is used to configure an NCoA on the NAR's link. In 315 this case, the protocol supports forwarding using PCoA, and the MN 316 performs DHCP once it attaches to the NAR's link. The MN still 317 formulates an NCoA for FBU processing; however, it MUST NOT send data 318 packets using the NCoA in the FBU. 320 In order to reduce the Binding Update latency, the protocol specifies 321 a binding between the Previous CoA (PCoA) and NCoA. An MN sends a 322 "Fast Binding Update" (see Section 6.2.2) message to its Previous 323 Access Router to establish this tunnel. When feasible, the MN SHOULD 324 send an FBU from the PAR's link. Otherwise, the MN should send the 325 FBU immediately after detecting attachment to the NAR. An FBU 326 message MUST contain the Binding Authorization Data for FMIPv6 (BADF) 327 option (see Section 6.4.5) in order to ensure that only a legitimate 328 MN that owns the PCoA is able to establish a binding. Subsequent 329 sections describe the protocol mechanics. In any case, the result is 330 that the PAR begins tunneling packets arriving for PCoA to NCoA. 331 Such a tunnel remains active until the MN completes the Binding 332 Update with its correspondents. In the opposite direction, the MN 333 SHOULD reverse tunnel packets to the PAR, again until it completes 334 Binding Update. And, PAR MUST forward the inner packet in the tunnel 335 to its destination (i.e., to the MN's correspondent). Such a reverse 336 tunnel ensures that packets containing a PCoA as a source IP address 337 are not dropped due to ingress filtering. Even though the MN is IP- 338 capable on the new link, it cannot use the NCoA directly with its 339 correspondents without the correspondents first establishing a 340 binding cache entry (for the NCoA). Forwarding support for the PCoA 341 is provided through a reverse tunnel between the MN and the PAR. 343 Setting up a tunnel alone does not ensure that the MN receives 344 packets as soon as it is attached to a new subnet link, unless the 345 NAR can detect the MN's presence. A neighbor discovery operation 346 involving a neighbor's address resolution (i.e., Neighbor 347 Solicitation and Neighbor Advertisement) typically results in 348 considerable delay, sometimes lasting multiple seconds. For 349 instance, when arriving packets trigger the NAR to send Neighbor 350 Solicitation before the MN attaches, subsequent retransmissions of 351 address resolution are separated by a default period of one second 352 each. In order to circumvent this delay, an MN announces its 353 attachment immediately with an UNA message that allows the NAR to 354 forward packets to the MN right away. Through tunnel establishment 355 for PCoA and fast advertisement, the protocol provides expedited 356 forwarding of packets to the MN. 358 The protocol also provides the following important functionalities. 359 The access routers can exchange messages to confirm that a proposed 360 NCoA is acceptable. For instance, when an MN sends an FBU from the 361 PAR's link, FBack can be delivered after the NAR considers the NCoA 362 acceptable for use. This is especially useful when addresses are 363 assigned by the access router. The NAR can also rely on its trust 364 relationship with the PAR before providing forwarding support for the 365 MN. That is, it may create a forwarding entry for the NCoA, subject 366 to "approval" from the PAR, which it trusts. In addition, buffering 367 for handover traffic at the NAR may be desirable. Even though the 368 Neighbor Discovery protocol provides a small buffer (typically one or 369 two packets) for packets awaiting address resolution, this buffer may 370 be inadequate for traffic, such as VoIP, already in progress. The 371 routers may also wish to maintain a separate buffer for servicing the 372 handover traffic. Finally, the access routers could transfer 373 network-resident contexts, such as access control, Quality of Service 374 (QoS), and header compression, in conjunction with handover (although 375 the context transfer process itself is not specified in this 376 document). For all these operations, the protocol provides "Handover 377 Initiate (HI)" and "Handover Acknowledge (HAck)" messages (see 378 Section 6.2.1). Both of these messages SHOULD be used. The access 379 routers MUST have the necessary security association established by 380 means outside the scope of this document. 382 3.2. Protocol Operation 384 The protocol begins when an MN sends an RtSolPr message to its access 385 router to resolve one or more Access Point Identifiers to subnet- 386 specific information. In response, the access router (e.g., PAR in 387 Figure 1) sends a PrRtAdv message containing one or more [AP-ID, AR- 388 Info] tuples. The MN may send an RtSolPr at any convenient time, for 389 instance as a response to some link-specific event (a "trigger") or 390 simply after performing router discovery. However, the expectation 391 is that prior to sending an RtSolPr, the MN will have discovered the 392 available APs by link-specific methods. The RtSolPr and PrRtAdv 393 messages do not establish any state at the access router; their 394 packet formats are defined in Section 6.1. 396 With the information provided in the PrRtAdv message, the MN 397 formulates a prospective NCoA and sends an FBU message to the PAR. 398 The purpose of the FBU is to authorize the PAR to bind the PCoA to 399 the NCoA, so that arriving packets can be tunneled to the new 400 location of the MN. The FBU should be sent from the PAR's link 401 whenever feasible. For instance, an internal link-specific trigger 402 could enable FBU transmission from the previous link. 404 When it is not feasible, the FBU is sent from the new link. 406 The format and semantics of FBU processing are specified in 407 Section 6.2.2. The FBU message MUST contain the BADF option (see 408 Section 6.4.5) to secure the message. 410 Depending on whether an FBack is received on the previous link (which 411 clearly depends on whether the FBU was sent in the first place), 412 there are two modes of operation. 414 1. The MN receives FBack on the previous link. This means that 415 packet tunneling is already in progress by the time the MN 416 handovers to the NAR. The MN SHOULD send the UNA immediately 417 after attaching to the NAR, so that arriving as well as buffered 418 packets can be forwarded to the MN right away. Before sending 419 FBack to the MN, the PAR can determine whether the NCoA is 420 acceptable to the NAR through the exchange of HI and HAck 421 messages. When assigned addressing (i.e., addresses are assigned 422 by the router) is used, the proposed NCoA in the FBU is carried 423 in an HI message (from PAR to NAR), and NAR MAY assign the 424 proposed NCoA. Such an assigned NCoA MUST be returned in HAck 425 (from NAR to PAR), and PAR MUST in turn provide the assigned NCoA 426 in FBack. If there is an assigned NCoA returned in FBack, the MN 427 MUST use the assigned address (and not the proposed address in 428 FBU) upon attaching to NAR. 430 2. The MN does not receive the FBack on the previous link because 431 the MN has not sent the FBU or the MN has left the link after 432 sending the FBU (which itself may be lost), but before receiving 433 an FBack. Without receiving an FBack in the latter case, the MN 434 cannot ascertain whether the PAR has processed the FBU 435 successfully. Hence, the MN (re)sends the FBU message to the PAR 436 immediately after sending the UNA message. If the NAR chooses to 437 supply a different IP address to use than the NCoA, it MAY send a 438 Router Advertisement with "Neighbor Advertisement Acknowledge 439 (NAACK)" option in which it includes an alternate IP address for 440 the MN to use. Detailed UNA processing rules are specified in 441 Section 6.3. 443 The scenario in which an MN sends an FBU and receives an FBack on 444 PAR's link is illustrated in Figure 2. For convenience, this 445 scenario is characterized as the "predictive" mode of operation. The 446 scenario in which the MN sends an FBU from the NAR's link is 447 illustrated in Figure 3. For convenience, this scenario is 448 characterized as the "reactive" mode of operation. Note that the 449 reactive mode also includes the case in which an FBU has been sent 450 from the PAR's link but an FBack has not yet been received. The 451 figure is intended to illustrate that the FBU is forwarded through 452 the NAR, but it is processed only by the PAR. 454 MN PAR NAR 455 | | | 456 |------RtSolPr------->| | 457 |<-----PrRtAdv--------| | 458 | | | 459 |------FBU----------->|----------HI--------->| 460 | |<--------HAck---------| 461 | <--FBack---|--FBack---> | 462 | | | 463 disconnect forward | 464 | packets ===============>| 465 | | | 466 | | | 467 connect | | 468 | | | 469 |------------UNA --------------------------->| 470 |<=================================== deliver packets 471 | | 473 Figure 2: Predictive Fast Handover 475 MN PAR NAR 476 | | | 477 |------RtSolPr------->| | 478 |<-----PrRtAdv--------| | 479 | | | 480 disconnect | | 481 | | | 482 | | | 483 connect | | 484 |-------UNA-----------|--------------------->| 485 |-------FBU-----------|---------------------)| 486 | |<-------FBU----------)| 487 | |----------HI--------->| 488 | |<-------HAck----------| 489 | |(HI/HAck if necessary)| 490 | forward | 491 | packets(including FBAck)=====>| 492 | | | 493 |<=================================== deliver packets 494 | | 496 Figure 3: Reactive Fast Handover 498 Finally, the PrRtAdv message may be sent unsolicited, i.e., without 499 the MN first sending an RtSolPr. This mode is described in 500 Section 3.3. 502 3.3. Protocol Operation during Network-Initiated Handover 504 In some wireless technologies, the handover control may reside in the 505 network even though the decision to undergo handover may be mutually 506 arrived at between the MN and the network. In such networks, the PAR 507 can send an unsolicited PrRtAdv containing the link-layer address, IP 508 address, and subnet prefix of the NAR when the network decides that a 509 handover is imminent. The MN MUST process this PrRtAdv to configure 510 a new Care-of Address on the new subnet, and MUST send an FBU to PAR 511 prior to switching to the new link. After transmitting PrRtAdv, the 512 PAR MUST continue to forward packets to the MN on its current link 513 until the FBU is received. The rest of the operation is the same as 514 that described in Section 3.2. 516 The unsolicited PrRtAdv also allows the network to inform the MN 517 about geographically adjacent subnets without the MN having to 518 explicitly request that information. This can reduce the amount of 519 wireless traffic required for the MN to obtain a neighborhood 520 topology map of links and subnets. Such usage of PrRtAdv is 521 decoupled from the actual handover; see Section 6.1.2. 523 4. Protocol Details 525 All descriptions refer to Figure 1. 527 After discovering one or more nearby access points, the MN sends 528 RtSolPr to the PAR in order to resolve access point identifiers to 529 subnet router information. A convenient time to do this is after 530 performing router discovery. However, the MN can send RtSolPr at any 531 time, e.g., when one or more new access points are discovered. The 532 MN can also send RtSolPr more than once during its attachment to PAR. 533 The trigger for sending RtSolPr can originate from a link-specific 534 event, such as the promise of a better signal strength from another 535 access point coupled with fading signal quality with the current 536 access point. Such events, often broadly referred to as "L2 537 triggers", are outside the scope of this document. Nevertheless, 538 they serve as events that invoke this protocol. For instance, when a 539 "link up" indication is obtained on the new link, protocol messages 540 (e.g., UNA) can be transmitted immediately. Implementations SHOULD 541 make use of such triggers whenever available. 543 The RtSolPr message contains one or more AP-IDs. A wildcard requests 544 all available tuples. 546 As a response to RtSolPr, the PAR sends a PrRtAdv message that 547 indicates one of the following possible conditions. 549 1. If the PAR does not have an entry corresponding to the new access 550 point, it MUST respond indicating that the new access point is 551 unknown. The MN MUST stop fast handover protocol operations on 552 the current link. The MN MAY send an FBU from its new link. 554 2. If the new access point is connected to the PAR's current 555 interface (to which MN is attached), the PAR MUST respond with a 556 Code value indicating that the new access point is connected to 557 the current interface, but not send any prefix information. This 558 scenario could arise, for example, when several wireless access 559 points are bridged into a wired network. No further protocol 560 action is necessary. 562 3. If the new access point is known and the PAR has information 563 about it, then the PAR MUST respond indicating that the new 564 access point is known and supply the [AP-ID, AR-Info] tuple. If 565 the new access point is known, but does not support fast 566 handover, the PAR MUST indicate this with Code 3 (see 567 Section 6.1.2). 569 4. If a wildcard is supplied as an identifier for the new access 570 point, the PAR SHOULD supply neighborhood [AP-ID, AR-Info] tuples 571 that are subject to path MTU restrictions (i.e., provide any 'n' 572 tuples without exceeding the link MTU). 574 When further protocol action is necessary, some implementations MAY 575 choose to begin buffering copies of incoming packets at the PAR. If 576 such First In First Out (FIFO) buffering is used, the PAR MUST 577 continue forwarding the packets to the PCoA (i.e., buffer and 578 forward). While the protocol does not forbid such an implementation 579 support, care must be taken to ensure that the PAR continues 580 forwarding packets to the PCoA (i.e., uses a buffer and forward 581 approach). The PAR SHOULD stop buffering once it begins forwarding 582 packets to the NCoA. 584 The method by which access routers exchange information about their 585 neighbors and thereby allow construction of Proxy Router 586 Advertisements with information about neighboring subnets is outside 587 the scope of this document. 589 The RtSolPr and PrRtAdv messages MUST be implemented by an MN and an 590 access router that supports fast handovers. However, when the 591 parameters necessary for the MN to send packets immediately upon 592 attaching to the NAR are supplied by the link-layer handover 593 mechanism itself, use of the above messages is optional on such 594 links. 596 After a PrRtAdv message is processed, the MN sends an FBU at a time 597 determined by link-specific events, and includes the proposed NCoA. 598 The MN SHOULD send the FBU from the PAR's link whenever 599 "anticipation" of handover is feasible. When anticipation is not 600 feasible or when it has not received an FBack, the MN sends an FBU 601 immediately after attaching to NAR's link. In response to the FBU, 602 the PAR establishes a binding between the PCoA ("Home Address") and 603 the NCoA, and sends the FBack to the MN. Prior to establishing this 604 binding, the PAR SHOULD send an HI message to the NAR, and receive 605 HAck in response. In order to determine the NAR's address for the HI 606 message, the PAR can perform the longest prefix match of NCoA (in 607 FBU) with the prefix list of neighboring access routers. When the 608 source IP address of the FBU is the PCoA, i.e., the FBU is sent from 609 the PAR's link, the HI message MUST have a Code value set to 0; see 610 Section 6.2.1.1. When the source IP address of the FBU is not PCoA, 611 i.e., the FBU is sent from the NAR's link, the HI message MUST have a 612 Code value of 1; see Section 6.2.1.1. 614 The HI message contains the PCoA, link-layer address and the NCoA of 615 the MN. In response to processing an HI message with Code 0, the 616 NAR: 618 1. determines whether the NCoA supplied in the HI message is unique 619 before beginning to defend it. It sends a Duplicate Address 620 Detection (DAD) probe [RFC4862] for NCoA to verify uniqueness. 621 However, in deployments where the probability of address 622 collisions is considered extremely low (and hence not an issue), 623 the parameter DupAddrDetectTransmits (see [RFC4862]) is set to 624 zero on the NAR, allowing it to avoid performing DAD on the NCoA. 625 The NAR similarly sets DupAddrDetectTransmits to zero in other 626 deployments where DAD is not a concern. Once the NCoA is 627 determined to be unique, the NAR starts proxying [RFC4861] the 628 address for PROXY_ND_LIFETIME during which the MN is expected to 629 connect to the NAR. In case there is already an NCoA present in 630 its data structure (for instance, it has already processed an HI 631 message earlier), the NAR MAY verify if the LLA is the same as 632 its own or that of the MN itself. If so, the NAR MAY allow the 633 use of the NCoA. 635 2. allocates the NCoA for the MN when assigned addressing is used, 636 creates a proxy neighbor cache entry and begins defending it. 637 The NAR MAY allocate the NCoA proposed in HI. 639 3. MAY create a host route entry for the PCoA (on the interface to 640 which the MN is attaching to) in case the NCoA cannot be accepted 641 or assigned. This host route entry SHOULD be implemented such 642 that until the MN's presence is detected, either through explicit 643 announcement by the MN or by other means, arriving packets do not 644 invoke neighbor discovery. The NAR SHOULD also set up a reverse 645 tunnel to the PAR in this case. 647 4. provides the status of the handover request in the Handover 648 Acknowledge (HAck) message to the PAR. 650 When the Code value in HI is 1, the NAR MUST skip the above 651 operations. Sending an HI message with Code 1 allows the NAR to 652 validate the neighbor cache entry it creates for the MN during UNA 653 processing. That is, the NAR can make use of the knowledge that its 654 trusted peer (i.e., the PAR) has a trust relationship with the MN. 656 If HAck contains an assigned NCoA, the FBack MUST include it, and the 657 MN MUST use the address provided in the FBack. The PAR MAY send the 658 FBack to the previous link as well to facilitate faster reception in 659 the event that the MN is still present. The result of the FBU and 660 FBack processing is that PAR begins tunneling the MN's packets to the 661 NCoA. If the MN does not receive an FBack message even after 662 retransmitting the FBU for FBU_RETRIES, it must assume that fast 663 handover support is not available and stop the protocol operation. 665 As soon as the MN establishes link connectivity with the NAR, it: 667 1. sends an UNA message (see Section 6.3). If the MN has not 668 received an FBack by the time UNA is being sent, it SHOULD send 669 an FBU message following the UNA message. 671 2. joins the all-nodes multicast group and the solicited-node 672 multicast group corresponding to the NCoA. 674 3. starts a DAD probe for NCoA, see [RFC4862]. 676 When a NAR receives an UNA message, it: 678 1. deletes its proxy neighbor cache entry, if it exists, updates the 679 state to STALE [RFC4861], and forwards arriving and buffered 680 packets. 682 2. updates an entry in INCOMPLETE state [RFC4861], if it exists, to 683 STALE and forwards arriving and buffered packets. This would be 684 the case if NAR had previously sent a Neighbor Solicitation that 685 went unanswered perhaps because the MN had not yet attached to 686 the link. 688 The buffer for handover traffic should be linked to this UNA 689 processing. The exact mechanism is implementation dependent. 691 The NAR may choose to provide a different IP address other than the 692 NCoA. This is possible if it is proxying the NCoA. In such a case, 693 it: 695 1. MAY send a Router Advertisement with the NAACK option in which it 696 includes an alternate IP address for use. This message MUST be 697 sent to the source IP address present in UNA using the same Layer 698 2 address present in UNA. 700 If the MN receives an IP address in the NAACK option, it MUST use it 701 and send an FBU using the new CoA. As a special case, the address 702 supplied in NAACK could be the PCoA itself, in which case the MN MUST 703 NOT send any more FBUs. The Status codes for the NAACK option are 704 specified in Section 6.4.6. 706 Once the MN has confirmed its NCoA (either through DAD or when 707 provided for by the NAR), it SHOULD send a Neighbor Advertisement 708 message with the 'O' bit set, to the all-nodes multicast address. 709 This message allows MN's neighbors to update their neighbor cache 710 entries. 712 For data forwarding, the PAR tunnels packets using its global IP 713 address valid on the interface to which the MN was attached. The MN 714 reverse tunnels its packets to the same global address of PAR. The 715 tunnel end-point addresses must be configured accordingly. When the 716 PAR receives a reverse tunneled packet, it must verify if a secure 717 binding exists for the MN identified by the PCoA in the tunneled 718 packet, before forwarding the packet. 720 5. Other Considerations 722 5.1. Handover Capability Exchange 724 The MN expects a PrRtAdv in response to its RtSolPr message. If the 725 MN does not receive a PrRtAdv message even after RTSOLPR_RETRIES, it 726 must assume that the PAR does not support the fast handover protocol 727 and stop sending any more RtSolPr messages. 729 Even if an MN's current access router is capable of providing fast 730 handover support, the new access router to which the MN attaches may 731 be incapable of fast handover. This is indicated to the MN during 732 "runtime", through the PrRtAdv message with a Code value of 3 (see 733 Section 6.1.2). 735 5.2. Determining New Care-of Address 737 Typically, the MN formulates its prospective NCoA using the 738 information provided in a PrRtAdv message and sends the FBU. The PAR 739 MUST use the NCoA present in the FBU in its HI message. The NAR MUST 740 verify if the NCoA present in HI is already in use. In any case, the 741 NAR MUST respond to HI using a HAck, in which it may include another 742 NCoA to use, especially when assigned address configuration is used. 743 If there is a CoA present in HAck, the PAR MUST include it in the 744 FBack message. However, the MN itself does not have to wait on PAR's 745 link for this exchange to take place. It can handover any time after 746 sending the FBU message; sometimes it may be forced to handover 747 without sending the FBU. In any case, it can still confirm using 748 NCoA from NAR's link by sending the UNA message. 750 If a PrRtAdv message carries an NCoA, the MN MUST use it as its 751 prospective NCoA. 753 When DHCP is used, the protocol supports forwarding for PCoA only. 754 In this case, the MN MUST perform DHCP operations once it attaches to 755 the NAR even though it formulates an NCoA for transmitting the FBU. 756 This is indicated in the PrRtAdv message with Code = 5. 758 5.3. Prefix Management 760 As defined in Section 2, the Prefix part of "AR-Info" is the prefix 761 valid on the interface to which the AP is attached. This document 762 does not specify how this Prefix is managed, it's length and 763 assignment policies. The protocol operation specified in this 764 document works regardless of these considerations. Often, but not 765 necessarily always, this Prefix may be the aggregate prefix (such as 766 /48) valid on the interface. In some deployments, each MN may have 767 its own per-mobile prefix (such as a /64) used for generating the 768 NCoA. Some point-to-point links may use such a deployment. 770 When per-mobile prefix assignment is used, the "AR-Info" advertised 771 in PrRtAdv still includes the (aggregate) prefix valid on the 772 interface to which the target AP is attached, unless the access 773 routers communicate with each other (using HI and HAck messages) to 774 manage the per-mobile prefix. The MN still formulates an NCoA using 775 the aggregate prefix. However, an alternate NCoA based on the per- 776 mobile prefix is returned by NAR in the HAck message. This alternate 777 NCoA is provided to the MN in either the FBack message or in the 778 NAACK option. 780 5.4. Packet Loss 782 Handover involves link switching, which may not be exactly 783 coordinated with fast handover signaling. Furthermore, the arrival 784 pattern of packets is dependent on many factors, including 785 application characteristics, network queuing behaviors, etc. Hence, 786 packets may arrive at the NAR before the MN is able to establish its 787 link there. These packets will be lost unless they are buffered by 788 the NAR. Similarly, if the MN attaches to the NAR and then sends an 789 FBU message, packets arriving at the PAR until the FBU is processed 790 will be lost unless they are buffered. This protocol provides an 791 option to indicate request for buffering at the NAR in the HI 792 message. When the PAR requests this feature (for the MN), it SHOULD 793 also provide its own support for buffering. 795 Whereas buffering can enable a smooth handover, the buffer size and 796 the rate at which buffered packets are eventually forwarded are 797 important considerations when providing buffering support. There are 798 a number of aspects to consider: 800 o Some applications transmit less data over a given period of data 801 than others, and this implies different buffering requirements. 802 For instance, Voice over IP typically needs smaller buffers 803 compared to high-resolution streaming video, as the latter has 804 larger packet sizes and higher arrival rates. 806 o When the mobile node appears on the new link, having the buffering 807 router send a large number of packets in quick succession may 808 overtax the resources of the router, the mobile node itself, or 809 the path between these two. 811 In particular, transmitting a large amount of buffered packets in 812 succession can congest the path between the buffering router and 813 the mobile node. Furthermore, nodes (such as a base station) on 814 the path between the buffering router and the mobile node may drop 815 such packets. If a base station buffers too many such packets, 816 they may contribute to additional jitter for packets arriving 817 behind them, which is undesirable for real-time communication. 819 o Since routers are not involved in end-to-end communication, they 820 have no knowledge of transport conditions. 822 o The wireless connectivity of the mobile node may vary over time. 823 It may achieve a smaller or higher bandwidth on the new link, 824 signal strength may be weak at the time it just enters the area of 825 this access point, and so on. 827 As a result, it is difficult to design an algorithm that would 828 transmit buffered packets at appropriate spacing under all scenarios. 829 The purpose of fast handovers is to avoid packet loss. Yet, draining 830 buffered packets too fast can, by itself, cause loss of the packets, 831 as well as blocking or loss of following packets meant for the mobile 832 node. 834 This specification does not restrict implementations from providing 835 specialized buffering support for any specific situation. However, 836 attention must be paid to the rate at which buffered packets are 837 forwarded to the MN once attachment is complete. Routers 838 implementing this specification MUST implement at least the default 839 algorithm, which is based on the original arrival rates of the 840 buffered packets. A maximum of 5 packets MAY be sent one after 841 another, but all subsequent packets SHOULD use a sending rate that is 842 determined by metering the rate at which packets have entered the 843 buffer, potentially using smoothing techniques such as recent 844 activity over a sliding time window and weighted averages [RFC3290]. 846 It should be noted, however, that this default algorithm is crude and 847 may not be suitable for all situations. Future revisions of this 848 specification may provide additional algorithms, once enough 849 experience of the various conditions in deployed networks is 850 attained. 852 5.5. DAD Handling 854 Duplicate Address Detection (DAD) was defined in [RFC4862] to avoid 855 address duplication on links when stateless address auto- 856 configuration is used. The use of DAD to verify the uniqueness of an 857 IPv6 address configured through stateless auto-configuration adds 858 delays to a handover. The probability of an interface identifier 859 duplication on the same subnet is very low; however, it cannot be 860 ignored. Hence, the protocol specified in this document SHOULD only 861 be used in deployments where the probability of such address 862 collisions is extremely low or it is not a concern (because of the 863 address management procedure deployed). The protocol requires the 864 NAR to send a DAD probe before it starts defending the NCoA. 865 However, this DAD delay can be turned off by setting 866 DupAddrDetectTransmits to zero on the NAR ([RFC4862]). 868 This document specifies messages that can be used to provide 869 duplicate-free addresses, but the document does not specify how to 870 create or manage such duplicate-free addresses. In some cases, the 871 NAR may already have the knowledge required to assess whether or not 872 the MN's address is a duplicate before the MN moves to the new 873 subnet. For example, in some deployments, the NAR may maintain a 874 pool of duplicate-free addresses in a list for handover purposes. In 875 such cases, the NAR can provide this disposition in the HAck message 876 (see Section 6.2.1.2) or in the NAACK option (see Section 6.4.6). 878 5.6. Fast or Erroneous Movement 880 Although this specification is for fast handover, the protocol is 881 limited in terms of how fast an MN can move. A special case of fast 882 movement is ping-pong, where an MN moves between the same two access 883 points rapidly. Another instance of the same problem is erroneous 884 movement, i.e., the MN receives information prior to a handover that 885 it is moving to a new access point but it either moves to a different 886 one or it aborts movement altogether. All of the above behaviors are 887 usually the result of link-layer idiosyncrasies and thus are often 888 resolved at the link layer itself. 890 IP layer mobility, however, introduces its own limits. IP layer 891 handovers should occur at a rate suitable for the MN to update the 892 binding of, at least, its Home Agent and preferably that of every CN 893 with which it is in communication. An MN that moves faster than 894 necessary for this signaling to complete, which may be of the order 895 of few seconds, may start losing packets. The signaling cost over 896 the air interface and in the network may increase significantly, 897 especially in the case of rapid movement between several access 898 routers. To avoid the signaling overhead, the following measures are 899 suggested. 901 An MN returning to the PAR before updating the necessary bindings 902 when present on the NAR MUST send a Fast Binding Update with the Home 903 Address equal to the MN's PCoA and a lifetime of zero to the PAR. 904 The MN should have a security association with the PAR since it 905 performed a fast handover to the NAR. The PAR, upon receiving this 906 Fast Binding Update, will check its set of outgoing (temporary fast 907 handover) tunnels. If it finds a match, it SHOULD terminate that 908 tunnel; i.e., start delivering packets directly to the node instead. 909 In order for the PAR to process such an FBU, the lifetime of the 910 security association has to be at least that of the tunnel itself. 912 Temporary tunnels for the purposes of fast handovers should use short 913 lifetimes (of the order of at most a few tens of seconds or less). 914 The lifetime of such tunnels should be enough to allow an MN to 915 update all its active bindings. The default lifetime of the tunnel 916 should be the same as the lifetime value in the FBU message. 918 The effect of erroneous movement is typically limited to the loss of 919 packets since routing can change and the PAR may forward packets 920 toward another router before the MN actually connects to that router. 921 If the MN discovers itself on an unanticipated access router, it 922 SHOULD send a new Fast Binding Update to the PAR. This FBU 923 supersedes the existing binding at the PAR, and the packets will be 924 redirected to the newly confirmed location of the MN. 926 6. Message Formats 928 All the ICMPv6 messages have a common Type specified in [RFC4443]. 929 The messages are distinguished based on the Subtype field (see 930 below). For all the ICMPv6 messages, the checksum is defined in 931 [RFC4443]. 933 6.1. New Neighborhood Discovery Messages 935 6.1.1. Router Solicitation for Proxy Advertisement (RtSolPr) 937 Mobile Nodes send Router Solicitation for Proxy Advertisement in 938 order to prompt routers for Proxy Router Advertisements. All the 939 Link-Layer Address options have the format defined in Section 6.4.3. 941 0 1 2 3 942 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 1 943 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 944 | Type | Code | Checksum | 945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 946 | Subtype | Reserved | Identifier | 947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 948 | Options ... 949 +-+-+-+-+-+-+-+-+-+-+-+- 951 Figure 4: Router Solicitation for Proxy Advertisement (RtSolPr) 952 Message 954 IP Fields: 956 Source Address: An IP address assigned to the sending 957 interface. 959 Destination Address: The address of the access router or the 960 all routers multicast address. 962 Hop Limit: 255. See RFC 2461. 964 ICMP Fields: 966 Type: 154 968 Code: 0 970 Checksum: The ICMPv6 checksum. 972 Subtype: 2 974 Reserved: MUST be set to zero by the sender and ignored by the 975 receiver. 977 Identifier: MUST be set by the sender so that replies can be 978 matched to this Solicitation. 980 Valid Options: 982 Source Link-Layer Address: When known, the link-layer address 983 of the sender SHOULD be included using the Link-Layer Address 984 (LLA) option. See the LLA option format below. 986 New Access Point Link-Layer Address: The link-layer address or 987 identification of the access point for which the MN requests 988 routing advertisement information. It MUST be included in all 989 RtSolPr messages. More than one such address or identifier can 990 be present. This field can also be a wildcard address. See 991 the LLA option below. 993 Future versions of this protocol may define new option types. 994 Receivers MUST silently ignore any options that they do not recognize 995 and continue processing the rest of the message. 997 Including the source LLA option allows the receiver to record the 998 sender's L2 address so that neighbor discovery can be avoided when 999 the receiver needs to send packets back to the sender (of the RtSolPr 1000 message). 1002 When a wildcard is used for New Access Point LLA, no other New Access 1003 Point LLA options must be present. 1005 A Proxy Router Advertisement (PrRtAdv) message should be received by 1006 the MN in response to an RtSolPr. If such a message is not received 1007 in a timely manner (no less than twice the typical round trip time 1008 (RTT) over the access link or 100 milliseconds if RTT is not known), 1009 it SHOULD resend the RtSolPr message. Subsequent retransmissions can 1010 be up to RTSOLPR_RETRIES, but MUST use an exponential backoff in 1011 which the timeout period (i.e., 2xRTT or 100 milliseconds) is doubled 1012 prior to each instance of retransmission. If Proxy Router 1013 Advertisement is not received by the time the MN disconnects from the 1014 PAR, the MN SHOULD send an FBU immediately after configuring a new 1015 CoA. 1017 When RtSolPr messages are sent more than once, they MUST be rate 1018 limited with MAX_RTSOLPR_RATE per second. During each use of an 1019 RtSolPr, exponential backoff is used for retransmissions. 1021 6.1.2. Proxy Router Advertisement (PrRtAdv) 1023 Access routers send Proxy Router Advertisement messages gratuitously 1024 if the handover is network-initiated or as a response to an RtSolPr 1025 message from an MN, providing the link-layer address, IP address, and 1026 subnet prefixes of neighboring routers. All the Link-Layer Address 1027 options have the format defined in 6.4.3. 1029 0 1 2 3 1030 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 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 | Type | Code | Checksum | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 | Subtype | Reserved | Identifier | 1035 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 | Options ... 1037 +-+-+-+-+-+-+-+-+-+-+-+- 1039 Figure 5: Proxy Router Advertisement (PrRtAdv) Message 1041 IP Fields: 1043 Source Address: MUST be the link-local address assigned to the 1044 interface from which this message is sent. 1046 Destination Address: The Source Address of an invoking Router 1047 Solicitation for Proxy Advertisement or the address of the node 1048 the access router is instructing to handover. 1050 Hop Limit: 255. See RFC 2461. 1052 ICMP Fields: 1054 Type: 154 1056 Code: 0, 1, 2, 3, 4, or 5. See below. 1058 Checksum: The ICMPv6 checksum. 1060 Subtype: 3 1062 Reserved: MUST be set to zero by the sender and ignored by the 1063 receiver. 1065 Identifier: Copied from Router Solicitation for Proxy 1066 Advertisement or set to zero if unsolicited. 1068 Valid Options in the following order: 1070 Source Link-Layer Address: When known, the link-layer address 1071 of the sender SHOULD be included using the Link-Layer Address 1072 option. See the LLA option format below. 1074 New Access Point Link-Layer Address: The link-layer address or 1075 identification of the access point is copied from RtSolPr 1076 message. This option MUST be present. 1078 New Router's Link-Layer Address: The link-layer address of the 1079 access router for which this message is proxied for. This 1080 option MUST be included when the Code is 0 or 1. 1082 New Router's IP Address: The IP address of the NAR. This 1083 option MUST be included when the Code is 0 or 1. 1085 New Router Prefix Information Option: Specifies the prefix of 1086 the access router the message is proxied for and is used for 1087 address auto-configuration. This option MUST be included when 1088 Code is 0 or 1. However, when this prefix is the same as what 1089 is used in the New Router's IP Address option (above), the 1090 Prefix Information option need not be present. 1092 New CoA Option: MAY be present when PrRtAdv is sent 1093 unsolicited. The PAR MAY compute a new CoA using the NAR's 1094 prefix information and the MN's L2 address or by any other 1095 means. 1097 Future versions of this protocol may define new option types. 1098 Receivers MUST silently ignore any options they do not recognize and 1099 continue processing the message. 1101 Currently, Code values 0, 1, 2, 3, 4, and 5 are defined. 1103 A Proxy Router Advertisement with Code 0 means that the MN should use 1104 the [AP-ID, AR-Info] tuple (present in the options above) for 1105 movement detection and NCoA formulation. The Option-Code field in 1106 the New Access Point LLA option in this case is 1 reflecting the LLA 1107 of the access point for which the rest of the options are related. 1108 Multiple tuples may be present. 1110 A Proxy Router Advertisement with Code 1 means that the message has 1111 been sent unsolicited. If a New CoA option is present following the 1112 New Router Prefix Information option, the MN MUST use the supplied 1113 NCoA and send an FBU immediately or else stand to lose service. This 1114 message acts as a network-initiated handover trigger; see 1115 Section 3.3. The Option-Code field in the New Access Point LLA 1116 option (see below) in this case is 1 reflecting the LLA of the access 1117 point for which the rest of the options are related. 1119 A Proxy Router Advertisement with Code 2 means that no new router 1120 information is present. Each New Access Point LLA option contains an 1121 Option-Code value (described below) that indicates a specific 1122 outcome. 1124 When the Option-Code field in the New Access Point LLA option is 1125 5, handover to that access point does not require a change of CoA. 1126 This would be the case, for instance, when a number of access 1127 points are connected to the same router interface, or when network 1128 based mobility management mechanisms ensure that the specific 1129 mobile node always observes the same prefix regardless of whether 1130 there is a separate router attached to the target access point. 1132 No other options are required in this case. 1134 When the Option-Code field in the New Access Point LLA option is 1135 6, the PAR is not aware of the Prefix Information requested. The 1136 MN SHOULD attempt to send an FBU as soon as it regains 1137 connectivity with the NAR. No other options are required in this 1138 case. 1140 When the Option-Code field in the New Access Point LLA option is 1141 7, it means that the NAR does not support fast handover. The MN 1142 MUST stop fast handover protocol operations. No other options are 1143 required in this case. 1145 A Proxy Router Advertisement with Code 3 means that new router 1146 information is only present for a subset of access points requested. 1147 The Option-Code field values (defined above including a value of 1) 1148 distinguish different outcomes for individual access points. 1150 A Proxy Router Advertisement with Code 4 means that the subnet 1151 information regarding neighboring access points is sent unsolicited, 1152 but the message is not a handover trigger, unlike when the message is 1153 sent with Code 1. Multiple tuples may be present. 1155 A Proxy Router Advertisement with Code 5 means that the MN may use 1156 the new router information present for detecting movement to a new 1157 subnet, but the MN must perform DHCP [RFC3315] upon attaching to the 1158 NAR's link. The PAR and NAR will forward packets to the PCoA of the 1159 MN. The MN must still formulate an NCoA for transmitting FBU (using 1160 the information sent in this message), but that NCoA will not be used 1161 for forwarding packets. 1163 When a wildcard AP identifier is supplied in the RtSolPr message, the 1164 PrRtAdv message should include any 'n' [Access Point Identifier, 1165 Link-Layer Address option, Prefix Information Option] tuples 1166 corresponding to the PAR's neighborhood. 1168 6.2. New Mobility Header Messages 1170 Mobile IPv6 uses a new IPv6 header type called Mobility Header 1171 [RFC3775]. The Handover Initiate, Handover Acknowledge, Fast Binding 1172 Update, Fast Binding Acknowledgment, and the (deprecated) Fast 1173 Neighbor Advertisement messages use the Mobility Header. 1175 6.2.1. Inter - Access Router Messages 1177 6.2.1.1. Handover Initiate (HI) 1179 The Handover Initiate (HI) is a Mobility Header message sent by an 1180 Access Router (typically PAR) to another access router (typically 1181 NAR) to initiate the process of an MN's handover. 1183 0 1 2 3 1184 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 1186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1187 | Sequence # | 1188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1189 |S|U| Reserved | Reserved | Code | 1190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1191 | | 1192 . . 1193 . Mobility options . 1194 . . 1195 | | 1196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1198 Figure 6: Handover Initiate (HI) Message 1200 IP Fields: 1202 Source Address: The IP address of the PAR 1204 Destination Address: The IP address of the NAR 1206 Sequence #: See [RFC3775]. 1208 'S' flag: Assigned address configuration flag. When set, this 1209 message requests a new CoA to be returned by the destination. 1210 MAY be set when Code = 0. MUST be 0 when Code = 1. 1212 'U' flag: Buffer flag. When set, the destination SHOULD buffer 1213 any packets toward the node indicated in the options of this 1214 message. Used when Code = 0, SHOULD be set to 0 when Code = 1. 1216 Code: 0 or 1. See below 1218 Reserved: MUST be set to zero by the sender and ignored by the 1219 receiver. 1221 Valid Options: 1223 Link-Layer Address of MN: The link-layer address of the MN that 1224 is undergoing handover to the destination (i.e., NAR). This 1225 option MUST be included so that the destination can recognize 1226 the MN. 1228 Previous Care-of Address: The IP address used by the MN while 1229 attached to the originating router. This option SHOULD be 1230 included so that a host route can be established if necessary. 1232 New Care-of Address: The IP address the MN wishes to use when 1233 connected to the destination. When the 'S' bit is set, the NAR 1234 MAY assign this address. 1236 The PAR uses a Code value of 0 when it processes an FBU with PCoA as 1237 source IP address. The PAR uses a Code value of 1 when it processes 1238 an FBU whose source IP address is not PCoA. 1240 If a Handover Acknowledge (HAck) message is not received as a 1241 response in a short time period (no less than twice the typical round 1242 trip time (RTT) between source and destination, or 100 milliseconds 1243 if RTT is not known), the Handover Initiate SHOULD be resent. 1244 Subsequent retransmissions can be up to HI_RETRIES, but MUST use 1245 exponential backoff in which the timeout period (i.e., 2xRTT or 100 1246 milliseconds) is doubled during each instance of retransmission. 1248 6.2.1.2. Handover Acknowledge (HAck) 1250 The Handover Acknowledge message is a new Mobility Header message 1251 that MUST be sent (typically by the NAR to the PAR) as a reply to the 1252 Handover Initiate message. 1254 0 1 2 3 1255 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 1257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1258 | Sequence # | 1259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1260 | Reserved | Reserved | Code | 1261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1262 | | 1263 . . 1264 . Mobility options . 1265 . . 1266 | | 1267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1269 Figure 7: Handover Acknowledge (HAck) Message 1271 IP Fields: 1273 Source Address: Copied from the destination address of the 1274 Handover Initiate Message to which this message is a response. 1276 Destination Address: Copied from the source address of the 1277 Handover Initiate Message to which this message is a response. 1279 Sequence #: Copied from the HI message to enable the 1280 destination to match this HAck message with an outstanding HI 1281 message. 1283 Code: 1285 0: Handover Accepted, NCoA valid 1287 1: Handover Accepted, NCoA not valid or in use 1289 2: Handover Accepted, NCoA assigned (used in Assigned 1290 addressing) 1292 3: Handover Accepted, use PCoA 1294 4: Message sent unsolicited, usually to trigger an HI 1295 message 1297 128: Handover Not Accepted, reason unspecified 1299 129: Administratively prohibited 1301 130: Insufficient resources 1303 Reserved: MUST be set to zero by the sender and ignored by the 1304 receiver. 1306 Valid Options: 1308 New Care-of Address: If the S flag in the Handover Initiate 1309 message is set, this option MUST be used to provide NCoA the MN 1310 should use when connected to this router. This option MAY be 1311 included, even when the 'S' bit is not set, e.g., Code 2 above. 1313 Upon receiving an HI message, the NAR MUST respond with a Handover 1314 Acknowledge message. If the 'S' flag is set in the HI message, the 1315 NAR SHOULD include the New Care-of Address option and a Code 3. 1317 The NAR MAY provide support for the PCoA (instead of accepting or 1318 assigning an NCoA), establish a host route entry for the PCoA, and 1319 set up a tunnel to the PAR to forward the MN's packets sent with the 1320 PCoA as a source IP address. This host route entry SHOULD be used to 1321 forward packets once the NAR detects that the particular MN is 1322 attached to its link. The NAR indicates forwarding support for PCoA 1323 using Code value 3 in the HAck message. Subsequently, the PAR 1324 establishes a tunnel to the NAR in order to forward packets arriving 1325 for the PCoA. 1327 When responding to an HI message containing a Code value 1, the Code 1328 values 1, 2, and 4 in the HAck message are not relevant. 1330 Finally, the New Access Router can always refuse handover, in which 1331 case it should indicate the reason in one of the available Code 1332 values. 1334 6.2.2. Fast Binding Update (FBU) 1336 The Fast Binding Update message has a Mobility Header Type value of 1337 8. The FBU is identical to the Mobile IPv6 Binding Update (BU) 1338 message. However, the processing rules are slightly different. 1340 0 1 2 3 1341 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 1343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1344 | Sequence # | 1345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1346 |A|H|L|K| Reserved | Lifetime | 1347 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1348 | | 1349 . . 1350 . Mobility options . 1351 . . 1352 | | 1353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1355 Figure 8: Fast Binding Update (FBU) Message 1357 IP Fields: 1359 Source Address: The PCoA or NCoA 1361 Destination Address: The IP address of the Previous Access 1362 Router 1364 'A' flag: MUST be set to one to request that PAR send a Fast 1365 Binding Acknowledgment message. 1367 'H' flag: MUST be set to one. See [RFC3775]. 1369 'L' flag: See [RFC3775]. 1371 'K' flag: See [RFC3775]. 1373 Reserved: This field is unused. MUST be set to zero. 1375 Sequence Number: See [RFC3775]. 1377 Lifetime: The requested time in seconds for which the sender 1378 wishes to have a binding. 1380 Mobility Options: MUST contain an alternate CoA option set to the 1381 NCoA when an FBU is sent from the PAR's link. MUST contain the 1382 Binding Authorization Data for the FMIP (BADF) option. See 1383 Section 6.4.5. MAY contain the Mobility Header LLA option (see 1384 Section 6.4.4). 1386 The MN sends an FBU message any time after receiving a PrRtAdv 1387 message. If the MN moves prior to receiving a PrRtAdv message, it 1388 SHOULD send an FBU to the PAR after configuring the NCoA on the NAR 1389 according to Neighbor Discovery and IPv6 Address Configuration 1390 protocols. When the MN moves without having received a PrRtAdv 1391 message, it cannot transmit an UNA message upon attaching to the 1392 NAR's link. 1394 The source IP address is the PCoA when the FBU is sent from the PAR's 1395 link, and the source IP address is the NCoA when the FBU sent from 1396 the NAR's link. When the source IP address is the PCoA, the MN MUST 1397 include the alternate CoA option set to NCoA. The PAR MUST process 1398 the FBU even though the address in the alternate CoA option is 1399 different from that in the source IP address, and ensure that the 1400 address in the alternate CoA option is used in the New CoA option in 1401 the HI message to the NAR. 1403 The FBU MUST also include the Home Address Option set to PCoA. An 1404 FBU message MUST be protected so that the PAR is able to determine 1405 that the FBU message is sent by an MN that legitimately owns the 1406 PCoA. 1408 6.2.3. Fast Binding Acknowledgment (FBack) 1410 The Fast Binding Acknowledgment message has a Mobility Header Type 1411 value of 9. The FBack message is sent by the PAR to acknowledge 1412 receipt of a Fast Binding Update message in which the 'A' bit is set. 1413 If PAR sends an HI message to the NAR after processing an FBU, the 1414 FBack message SHOULD NOT be sent to the MN before the PAR receives a 1415 HAck message from the NAR. The PAR MAY send the FBack immediately in 1416 the reactive mode however. The Fast Binding Acknowledgment MAY also 1417 be sent to the MN on the old link. 1419 0 1 2 3 1420 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 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1423 | Status |K| Reserved | 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1425 | Sequence # | Lifetime | 1426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1427 | | 1428 . . 1429 . Mobility options . 1430 . . 1431 | | 1432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1434 Figure 9: Fast Binding Acknowledgment (FBack) Message 1436 IP Fields: 1438 Source address: The IP address of the Previous Access Router 1440 Destination Address: The NCoA, and optionally the PCoA 1442 Status: 8-bit unsigned integer indicating the disposition of the 1443 Fast Binding Update. Values of the Status field that are less 1444 than 128 indicate that the Binding Update was accepted by the 1445 receiving node. The following such Status values are currently 1446 defined: 1448 0 Fast Binding Update accepted 1450 1 Fast Binding Update accepted but NCoA is invalid. Use NCoA 1451 supplied in "alternate" CoA 1453 Values of the Status field greater than or equal to 128 indicate 1454 that the Binding Update was rejected by the receiving node. The 1455 following such Status values are currently defined: 1457 128: Reason unspecified 1459 129: Administratively prohibited 1461 130: Insufficient resources 1463 131: Incorrect interface identifier length 1465 'K' flag: See [RFC3775]. 1467 Reserved: An unused field. MUST be set to zero. 1469 Sequence Number: Copied from the FBU message for use by the MN in 1470 matching this acknowledgment with an outstanding FBU. 1472 Lifetime: The granted lifetime in seconds for which the sender of 1473 this message will retain a binding for traffic redirection. 1475 Mobility Options: MUST contain an "alternate" CoA if Status is 1. 1476 MUST contain the Binding Authorization Data for FMIP (BADF) 1477 option. See 6.4.5. 1479 6.3. Unsolicited Neighbor Advertisement (UNA) 1481 This is the same message as in [RFC4861] with the requirement that 1482 the 'O' bit is always set to zero. Since this is an unsolicited 1483 message, the 'S' bit is zero, and since this is sent by an MN, the 1484 'R' bit is also zero. 1486 If the NAR is proxying the NCoA (as a result of HI and HAck 1487 exchange), then UNA processing has additional steps (see below). If 1488 the NAR is not proxying the NCoA (for instance, HI and HAck exchange 1489 has not taken place), then UNA processing follows the same procedure 1490 as specified in [RFC4861]. Implementations MAY retransmit UNA 1491 subject to the specification in Section 7.2.6 of [RFC4861] while 1492 noting that the default RetransTimer value is large for handover 1493 purposes. 1495 The Source Address in UNA MUST be the NCoA. The destination address 1496 is typically the all-nodes multicast address; however, some 1497 deployments may not prefer transmission to a multicast address. In 1498 such cases, the destination address SHOULD be the NAR's IP address. 1500 The Target Address MUST include the NCoA, and the Target link-layer 1501 address MUST include the MN's LLA. 1503 The MN sends an UNA message to the NAR, as soon as it regains 1504 connectivity on the new link. Arriving or buffered packets can be 1505 immediately forwarded. If the NAR is proxying the NCoA, it creates a 1506 neighbor cache entry in STALE state but forwards packets as it 1507 determines bidirectional reachability according to the standard 1508 Neighbor Discovery procedure. If there is an entry in INCOMPLETE 1509 state without a link-layer address, it sets it to STALE, again 1510 according to the procedure in [RFC4861]. 1512 The NAR MAY wish to provide a different IP address to the MN than the 1513 one in the UNA message. In such a case, the NAR MUST delete the 1514 proxy entry for the NCoA and send a Router Advertisement with NAACK 1515 option containing the new IP address. 1517 The combination of the NCoA (present in source IP address) and the 1518 Link-Layer Address (present as a Target LLA) SHOULD be used to 1519 distinguish the MN from other nodes. 1521 6.4. New Options 1523 All the options, with the exception of Binding Data Authorization for 1524 FMIPv6 (BADF) discussed in Section 6.4.5, use Type, Length, and 1525 Option-Code format shown in Figure 10. 1527 The Type values are defined from the Neighbor Discovery options space 1528 and Mobility Header options space. The Length field is in units of 8 1529 octets for Neighbor Discovery options, and is in units of octets for 1530 Mobility Header options. And, Option-Code provides additional 1531 information for each of the options (see individual options below). 1533 0 1 2 3 1534 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 1535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1536 | Type | Length | Option-Code | | 1537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1538 ~ ... ~ 1539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1541 Figure 10: Option Format 1543 6.4.1. IP Address/Prefix Option 1545 This option is sent in the Proxy Router Advertisement message. 1547 0 1 2 3 1548 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 1549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1550 | Type | Length | Option-Code | Prefix Length | 1551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1552 | Reserved | 1553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1554 | | 1555 + + 1556 | | 1557 + IPv6 Address + 1558 | | 1559 + + 1560 | | 1561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1563 Figure 11: IPv6 Address/Prefix Option 1565 Type: 17 1567 Length: The size of this option in 8 octets including the Type, 1568 Option-Code, and Length fields. 1570 Option-Code: 1572 1: Old Care-of Address 1574 2: New Care-of Address 1576 3: NAR's IP address 1578 4: NAR's Prefix, sent in PrRtAdv. The Prefix Length field 1579 contains the number of valid leading bits in the prefix. The 1580 bits in the prefix after the prefix length are reserved and 1581 MUST be initialized to zero by the sender and ignored by the 1582 receiver. 1584 Prefix Length: 8-bit unsigned integer that indicates the length of 1585 the IPv6 Address Prefix. The value ranges from 0 to 128. 1587 Reserved: MUST be set to zero by the sender and MUST be ignored by 1588 the receiver. 1590 IPv6 address: The IP address defined by the Option-Code field. 1592 6.4.2. Mobility Header IP Address/Prefix Option 1594 This option is sent in the Handover Initiate, and Handover 1595 Acknowledge messages. This option has an alignment requirement of 1596 8n+4. 1598 0 1 2 3 1599 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 1600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1601 | Type | Length | Option-Code | Prefix Length | 1602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1603 | | 1604 + + 1605 | | 1606 + IPv6 Address/Prefix + 1607 | | 1608 + + 1609 | | 1610 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1612 Figure 12: Mobility Header IPv6 Address/Prefix Option 1614 Type: 17 1616 Length: The size of this option in octets iexcluding the Type, and 1617 Length fields. 1619 Option-Code: 1621 1: Old Care-of Address 1623 2: New Care-of Address 1625 3: NAR's IP address 1627 4: NAR's Prefix, sent in PrRtAdv. The Prefix Length field 1628 contains the number of valid leading bits in the prefix. The 1629 bits in the prefix after the prefix length are reserved and 1630 MUST be initialized to zero by the sender and ignored by the 1631 receiver. 1633 Prefix Length: 8-bit unsigned integer that indicates the length of 1634 the IPv6 Address Prefix. The value ranges from 0 to 128. 1636 IPv6 address/prefix: The IP address/prefix defined by the Option- 1637 Code field. 1639 6.4.3. Link-Layer Address (LLA) Option 1641 0 1 2 3 1642 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 1643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1644 | Type | Length | Option-Code | LLA... 1645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1647 Figure 13: Link-Layer Address Option 1649 Type: 19 1651 Length: The size of this option in 8 octets including the Type, 1652 Option-Code, and Length fields. 1654 Option-Code: 1656 0: wildcard requesting resolution for all nearby access points 1658 1: Link-Layer Address of the New Access Point 1660 2: Link-Layer Address of the MN 1662 3: Link-Layer Address of the NAR (i.e., Proxied Originator) 1664 4: Link-Layer Address of the source of RtSolPr or PrRtAdv 1665 message 1667 5: The access point identified by the LLA belongs to the 1668 current interface of the router 1670 6: No prefix information available for the access point 1671 identified by the LLA 1673 7: No fast handovers support available for the access point 1674 identified by the LLA 1676 LLA: The variable length link-layer address. 1678 The LLA option does not have a length field for the LLA itself. The 1679 implementations must consult the specific link layer over which the 1680 protocol is run in order to determine the content and length of the 1681 LLA. 1683 Depending on the size of individual LLA option, appropriate padding 1684 MUST be used to ensure that the entire option size is a multiple of 8 1685 octets. 1687 The New Access Point Link-Layer Address contains the link-layer 1688 address of the access point for which handover is about to be 1689 attempted. This is used in the Router Solicitation for Proxy 1690 Advertisement message. 1692 The MN Link-Layer Address option contains the link-layer address of 1693 an MN. It is used in the Handover Initiate message. 1695 The NAR (i.e., Proxied Originator) Link-Layer Address option contains 1696 the link-layer address of the access router to which the Proxy Router 1697 Solicitation message refers. 1699 6.4.4. Mobility Header Link-Layer Address (MH-LLA) Option 1701 This option is identical to the LLA option, but is carried in the 1702 Mobility Header messages, e.g., FBU. In the future, other Mobility 1703 Header messages may also make use of this option. The format of the 1704 option is shown in Figure 14. There are no alignment requirements 1705 for this option. 1707 0 1 2 3 1708 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 1709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1710 | Type | Length | 1711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1712 | Option-Code | LLA .... 1713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1715 Figure 14: Mobility Header Link-Layer Address Option 1717 Type: 7 1719 Length: The size of this option in octets not including the Type 1720 and Length fields. 1722 Option-Code: 2 Link-Layer Address of the MN. 1724 LLA: The variable length link-layer address. 1726 6.4.5. Binding Authorization Data for FMIPv6 (BADF) 1728 This option MUST be present in FBU and FBack messages. The security 1729 association between the MN and the PAR is established by companion 1730 protocols [RFC5269]. This option specifies how to compute and verify 1731 a Message Authentication Code (MAC) using the established security 1732 association. 1734 The format of this option is shown in Figure 15. 1736 0 1 2 3 1737 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 1738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1739 | Type | Option Length | 1740 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1741 | SPI | 1742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1743 | | 1744 + + 1745 | Authenticator | 1746 + + 1747 | | 1748 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1750 Figure 15: Binding Authorization Data for FMIPv6 (BADF) Option 1752 Type: 21 1754 Option Length: The length of the Authenticator in bytes 1756 SPI: Security Parameter Index. SPI = 0 is reserved for the 1757 Authenticator computed using SEND-based handover keys. 1759 Authenticator: Same as in RFC 3775, with "correspondent" replaced 1760 by the PAR's IP address, and Kbm replaced by the shared key 1761 between the MN and the PAR. 1763 The default MAC calculation is done using HMAC_SHA1 with the first 96 1764 bits used for the MAC. Since there is an Option Length field, 1765 implementations can use other algorithms such as HMAC_SHA256. 1767 This option MUST be the last Mobility Option present. 1769 6.4.6. Neighbor Advertisement Acknowledgment (NAACK) 1771 0 1 2 3 1772 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 1773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1774 | Type | Length | Option-Code | Status | 1775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1776 | Reserved | 1777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1779 Figure 16: Neighbor Advertisement Acknowledgment Option 1781 Type: 20 1783 Length: 8-bit unsigned integer. Length of the option, in 8 1784 octets. The length is 1 when a new CoA is not supplied. The 1785 length is 3 when a new CoA is present (immediately following the 1786 Reserved field) 1788 Option-Code: 0 1790 Status: 8-bit unsigned integer indicating the disposition of the 1791 Unsolicited Neighbor Advertisement message. The following Status 1792 values are currently defined: 1794 1: NCoA is invalid, perform address configuration 1796 2: NCoA is invalid, use the supplied NCoA. The supplied NCoA 1797 (in the form of an IP Address Option) MUST be present following 1798 the Reserved field. 1800 3: NCoA is invalid, use NAR's IP address as NCoA in FBU 1802 4: PCoA supplied, do not send FBU 1804 128: Link-Layer Address unrecognized 1806 Reserved: MUST be set to zero by the sender and MUST be ignored by 1807 the receiver. 1809 The NAR responds to UNA with the NAACK option to notify the MN to use 1810 a different NCoA than the one that the MN has used. If the NAR 1811 proposes a different NCoA, the Router Advertisement MUST use the 1812 source IP address in the UNA message as the destination address, and 1813 use the L2 address present in UNA. The MN MUST use the NCoA if it is 1814 supplied with the NAACK option. If the NAACK indicates that the 1815 Link-Layer Address is unrecognized, for instance, if the MN uses an 1816 LLA valid on PAR's link but the same LLA is not valid on NAR's link 1817 due to a different access technology, the MN MUST NOT use the NCoA or 1818 the PCoA and SHOULD start immediately the process of acquiring a 1819 different NCoA at the NAR. 1821 In the future, new option types may be defined. 1823 7. Related Protocol and Device Considerations 1825 The protocol specified here, as a design principle, introduces no or 1826 minimal changes to related protocols. For example, no changes to the 1827 base Mobile IPv6 protocol are needed in order to implement this 1828 protocol. Similarly, no changes to the IPv6 stateless address auto- 1829 configuration protocol [RFC4862] and DHCP [RFC3315] are introduced. 1830 The protocol specifies an optional extension to Neighbor Discovery 1831 [RFC4861] in which an access router may send a router advertisement 1832 as a response to the UNA message (see Section Section 6.3). Other 1833 than this extension, the specification does not modify Neighbor 1834 Discovery behavior (including the procedures performed when attached 1835 to the PAR and when attaching to the NAR). 1837 The protocol does not require changes to any intermediate Layer 2 1838 device between an MN and its access router that supports this 1839 specification. This includes the wireless access points, switches, 1840 snooping devices, and so on. 1842 8. Evolution from and Compatibility with RFC 4068 1844 This document has evolved from [RFC4068]. Specifically, a new 1845 handover key establishment protocol (see [RFC5269]) has been defined 1846 to enable a security association between a mobile node and its access 1847 router. This allows the secure update of the routing of packets 1848 during a handover. In the future, new specifications may be defined 1849 to establish such security associations depending on the particular 1850 deployment scenario. 1852 The protocol has improved from the experiences in implementing 1853 [RFC4068], and from experimental usage. The input has improved the 1854 specification of parameter fields (such as lifetime, codepoints, 1855 etc.) as well as inclusion of new parameter fields in the existing 1856 messages. As of this writing, there are two publicly available 1857 implementations, [fmipv6] and [tarzan], and multiple proprietary 1858 implementations. Some experience suggests that the protocol meets 1859 the delay and packet loss requirements when used appropriately with 1860 particular radio access protocols. For instance, see [RFC5184], and 1861 [mip6-book]. Nevertheless, it is important to recognize that 1862 handover performance is a function of both IP layer operations, which 1863 this protocol specifies, and the particular radio access technology 1864 itself, which this protocol relies upon but does not modify. 1866 An existing implementation of [RFC4068] needs to be updated in order 1867 to support this specification. The primary addition is the 1868 establishment of a security association between an MN and its access 1869 router (i.e., MN and PAR). One way to establish such a security 1870 association is specified in [RFC5269]. An implementation that 1871 complies with the specification in this document is likely to also 1872 work with [RFC4068], except for the Binding Authorization Data for 1873 FMIPv6 option (see Section 6.4.5) that can only be processed when 1874 security association is in place between a mobile node and its access 1875 router. This specification deprecates the Fast Neighbor 1876 Advertisement (FNA) message. However, it is acceptable for a NAR to 1877 process this message from a mobile node as specified in [RFC4068]. 1879 9. Configurable Parameters 1881 Mobile nodes rely on configuration parameters shown in the table 1882 below. Each mobile node MUST have a configuration mechanism to 1883 adjust the parameters. Such a configuration mechanism may be either 1884 local (such as a command line interface) or based on central 1885 management of a number of mobile nodes. 1887 +-------------------+---------------+-----------------+ 1888 | Parameter Name | Default Value | Definition | 1889 +-------------------+---------------+-----------------+ 1890 | RTSOLPR_RETRIES | 3 | Section 6.1.1 | 1891 | MAX_RTSOLPR_RATE | 3 | Section 6.1.1 | 1892 | FBU_RETRIES | 3 | Section 6.2.2 | 1893 | PROXY_ND_LIFETIME | 1.5 seconds | Section 6.2.1.2 | 1894 | HI_RETRIES | 3 | Section 6.2.1.1 | 1895 +-------------------+---------------+-----------------+ 1897 10. Security Considerations 1899 The following security vulnerabilities are identified and suggested 1900 solutions are mentioned. 1902 Insecure FBU: in this case, packets meant for one address could be 1903 stolen or redirected to some unsuspecting node. This concern is 1904 the same as that in an MN and Home Agent relationship. 1906 Hence, the PAR MUST ensure that the FBU packet arrived from a node 1907 that legitimately owns the PCoA. The access router and its hosts 1908 may use any available mechanism to establish a security 1909 association that MUST be used to secure FBU. The current version 1910 of this protocol relies on a companion protocol [RFC5269] to 1911 establish such a security association. Using the shared handover 1912 key from [RFC5269], the Authenticator in BADF option (see 1913 Section 6.4.5) MUST be computed, and the BADF option included in 1914 FBU and FBack messages. 1916 Secure FBU, malicious or inadvertent redirection: in this case, 1917 the FBU is secured, but the target of binding happens to be an 1918 unsuspecting node either due to inadvertent operation or due to 1919 malicious intent. This vulnerability can lead to an MN with a 1920 genuine security association with its access router redirecting 1921 traffic to an incorrect address. 1923 However, the target of malicious traffic redirection is limited to 1924 an interface on an access router with which the PAR has a security 1925 association. The PAR MUST verify that the NCoA to which PCoA is 1926 being bound actually belongs to NAR's prefix. In order to do 1927 this, HI and HAck message exchanges are to be used. When NAR 1928 accepts NCoA in HI (with Code = 0), it proxies NCoA so that any 1929 arriving packets are not sent on the link until the MN attaches 1930 and announces itself through UNA. Therefore, any inadvertent or 1931 malicious redirection to a host is avoided. It is still possible 1932 to jam a NAR's buffer with redirected traffic. However, since a 1933 NAR's handover state corresponding to an NCoA has a finite (and 1934 short) lifetime corresponding to a small multiple of anticipated 1935 handover latency, the extent of this vulnerability is arguably 1936 small. 1938 Sending an FBU from a NAR's link: A malicious node may send an FBU 1939 from a NAR's link providing an unsuspecting node's address as an 1940 NCoA. This is similar to base Mobile IP where the MN can provide 1941 some other node's IP address as its CoA to its Home Agent; here 1942 the PAR acts like a "temporary Home Agent" having a security 1943 association with the Mobile Node and providing forwarding support 1944 for the handover traffic. As in base Mobile IP, this misdelivery 1945 is traceable to the MN that has a security association with the 1946 router. So, it is possible to isolate such an MN if it continues 1947 to misbehave. Similarly, an MN that has a security association 1948 with the PAR may provide the LLA of some other node on NAR's link, 1949 which can cause misdelivery of packets (meant for the NCoA) to an 1950 unsuspecting node. It is possible to trace the MN in this case as 1951 well. 1953 Apart from the above, the RtSolPr (Section 6.1.1) and PrRtAdv 1954 (Section 6.1.2) messages inherit the weaknesses of Neighbor Discovery 1955 protocol [RFC4861]. Specifically, when its access router is 1956 compromised, the MN's RtSolPr message may be answered by an attacker 1957 that provides a rogue router as the resolution. Should the MN attach 1958 to such a rogue router, its communication can be compromised. 1960 Similarly, a network-initiated PrRtAdv message (see Section 3.3) from 1961 an attacker could cause an MN to handover to a rogue router. Where 1962 these weaknesses are a concern, a solution such as Secure Neighbor 1963 Discovery (SEND) [RFC3971] SHOULD be considered. 1965 The protocol provides support for buffering packets during an MN's 1966 handover. This is done by securely exchanging the Handover Initiate 1967 (HI) and Handover Acknowledgment (HAck) messages in response to the 1968 FBU message from an MN. It is possible that an MN may fail, either 1969 inadvertently or purposely, to undergo handover to the NAR, which 1970 typically provides buffering support. This can cause the NAR to 1971 waste its memory containing the buffered packets, and in the worst 1972 case, could create resource exhaustion concerns. Hence, 1973 implementations must limit the size of the buffer as a local policy 1974 configuration, which may consider parameters such as the average 1975 handover delay, expected size of packets, and so on. 1977 The Handover Initiate (HI) and Handover Acknowledgement (HAck) 1978 messages exchanged between the PAR and NAR MUST be protected using 1979 end-to-end security association(s) offering integrity and data origin 1980 authentication. 1982 The PAR and the NAR MUST implement IPsec [RFC4301] for protecting the 1983 HI and HAck messages. IPsec Encapsulating Security Payload (ESP) 1984 [RFC4303] in transport mode with mandatory integrity protection 1985 SHOULD be used for protecting the signaling messages. 1986 Confidentiality protection of these messages is not required. 1988 The security associations can be created by using either manual IPsec 1989 configuration or a dynamic key negotiation protocol such as Internet 1990 Key Exchange Protocol version 2 (IKEv2) [RFC4306]. If IKEv2 is used, 1991 the PAR and the NAR can use any of the authentication mechanisms, as 1992 specified in RFC 4306, for mutual authentication. However, to ensure 1993 a baseline interoperability, the implementations MUST support shared 1994 secrets for mutual authentication. The following sections describe 1995 the Peer Authorization Database (PAD) and Security Policy Database 1996 (SPD) entries specified in [RFC4301] when IKEv2 is used for setting 1997 up the required IPsec security associations. 1999 10.1. Peer Authorization Database Entries when Using IKEv2 2001 This section describes PAD entries on the PAR and the NAR. The PAD 2002 entries are only example configurations. Note that the PAD is a 2003 logical concept and a particular PAR or NAR implementation can 2004 implement the PAD in any implementation specific manner. The PAD 2005 state may also be distributed across various databases in a specific 2006 implementation. 2008 PAR PAD: 2010 - IF remote_identity = nar_identity_1 2011 THEN authenticate (shared secret/certificate/EAP) and authorize 2012 CHILD_SA for remote address nar_address_1 2014 NAR PAD: 2016 - IF remote_identity = par_identity_1 2017 THEN authenticate (shared secret/certificate/EAP) and authorize 2018 CHILD_SAs for remote address par_address_1 2020 The list of authentication mechanisms in the above examples is not 2021 exhaustive. There could be other credentials used for authentication 2022 stored in the PAD. 2024 10.2. Security Policy Database Entries 2026 This section describes the security policy entries on the PAR and the 2027 NAR required to protect the HI and HAck messages. The SPD entries 2028 are only example configurations. A particular PAR or NAR 2029 implementation could configure different SPD entries as long as they 2030 provide the required security. 2032 In the examples shown below, the identity of the PAR is assumed to be 2033 par_1, the address of the PAR is assumed to be par_address_1, and the 2034 address of the NAR is assumed to be nar_address_1. 2036 PAR SPD-S: 2038 - IF local_address = par_address_1 & remote_address = 2039 nar_address_1 & proto = MH & local_mh_type = HI & 2040 remote_mh_type = HAck 2041 THEN use SA ESP transport mode Initiate using IDi = par_1 to 2042 address nar_address_1 2044 NAR SPD-S: 2046 - IF local_address = nar_address_1 & remote_address = 2047 par_address_1 & proto = MH & local_mh_type = HAck & 2048 remote_mh_type = HI 2049 THEN use SA ESP transport mode 2051 11. IANA Considerations 2053 This document defines two new Mobility Header messages which need 2054 allocation from the Mobility Header Type registry at 2055 http://www.iana.org/assignments/mobility-parameters 2056 TBD Handover Initiate Message (Section 6.2.1.1) 2058 TBD Handover Acknowledge Message (Section 6.2.1.2) 2060 This document defines a new Mobility Option that needs Type 2061 assignment from the Mobility Options Type registry at 2062 http://www.iana.org/assignments/mobility-parameters 2064 1. Mobility Header IPv6 Address/Prefix option, described in 2065 Section 6.4.2 2067 This document defines a new ICMPv6 message, which has been allocated 2068 from the ICMPv6 Type registry. 2070 154 FMIPv6 Messages 2072 This document creates a new registry for the 'Subtype' field in the 2073 above ICMPv6 message, called the "FMIPv6 Message Types". IANA has 2074 assigned the following values. 2076 +---------+-------------------+-----------------+ 2077 | Subtype | Description | Reference | 2078 +---------+-------------------+-----------------+ 2079 | 2 | RtSolPr | Section 6.1.1 | 2080 | 3 | PrRtAdv | Section 6.1.2 | 2081 | 4 | HI - Deprecated | Section 6.2.1.1 | 2082 | 5 | HAck - Deprecated | Section 6.2.1.2 | 2083 +---------+-------------------+-----------------+ 2085 The values '0' and '1' are reserved. The upper limit is 255. An RFC 2086 is required for new message assignment. 2088 The document defines a new Mobility Option that has received Type 2089 assignment from the Mobility Options Type registry. 2091 1. Binding Authorization Data for FMIPv6 (BADF) option, described in 2092 Section 6.4.5 2094 The document has already received Type assignments for the following 2095 (see [RFC4068]): 2097 The document defines the following Neighbor Discovery [RFC4861] 2098 options that have received Type assignment from IANA. 2100 +------+--------------------------------------------+---------------+ 2101 | Type | Description | Reference | 2102 +------+--------------------------------------------+---------------+ 2103 | 17 | IP Address/Prefix Option | Section 6.4.1 | 2104 | 19 | Link-layer Address Option | Section 6.4.3 | 2105 | 20 | Neighbor Advertisement Acknowledgment | Section 6.4.6 | 2106 | | Option | | 2107 +------+--------------------------------------------+---------------+ 2109 The document defines the following Mobility Header messages that have 2110 received Type allocation from the Mobility Header Types registry. 2112 1. Fast Binding Update, described in Section 6.2.2 2114 2. Fast Binding Acknowledgment, described in Section 6.2.3 2116 The document defines the following Mobility Option that has received 2117 Type assignment from the Mobility Options Type registry. 2119 1. Mobility Header Link-Layer Address option, described in 2120 Section 6.4.4 2122 12. Acknowledgments 2124 The editor would like to thank all those who have provided feedback 2125 on this specification, but can only mention a few here: Vijay 2126 Devarapalli, Youn-Hee Han, Emil Ivov, Syam Madanapalli, Suvidh 2127 Mathur, Andre Martin, Javier Martin, Koshiro Mitsuya, Gabriel 2128 Montenegro, Takeshi Ogawa, Sun Peng, YC Peng, Alex Petrescu, Domagoj 2129 Premec, Subba Reddy, K. Raghav, Ranjit Wable, and Jonathan Wood. 2130 Behcet Sarikaya and Frank Xia are acknowledged for the feedback on 2131 operation over point-to-point links. The editor would like to 2132 acknowledge a contribution from James Kempf to improve this 2133 specification. Vijay Devarapalli provided text for the security 2134 configuration between access routers in Section 10. Thanks to Jari 2135 Arkko for the detailed AD Review, which has improved this document. 2136 The editor would also like to thank the [mipshop] working group chair 2137 Gabriel Montenegro and the erstwhile [mobile ip] working group chairs 2138 Basavaraj Patil and Phil Roberts for providing much support for this 2139 work. 2141 13. References 2143 13.1. Normative References 2145 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2146 Requirement Levels", BCP 14, RFC 2119, March 1997. 2148 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 2149 and M. Carney, "Dynamic Host Configuration Protocol for 2150 IPv6 (DHCPv6)", RFC 3315, July 2003. 2152 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility 2153 Support in IPv6", RFC 3775, June 2004. 2155 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2156 Internet Protocol", RFC 4301, December 2005. 2158 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 2159 RFC 4303, December 2005. 2161 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 2162 RFC 4306, December 2005. 2164 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 2165 Message Protocol (ICMPv6) for the Internet Protocol 2166 Version 6 (IPv6) Specification", RFC 4443, March 2006. 2168 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2169 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2170 September 2007. 2172 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2173 Address Autoconfiguration", RFC 4862, September 2007. 2175 [RFC5269] Kempf, J. and R. Koodli, "Distributing a Symmetric Fast 2176 Mobile IPv6 (FMIPv6) Handover Key Using SEcure Neighbor 2177 Discovery (SEND)", RFC 5269, June 2008. 2179 [rfc5268] Koodli(Editor), R., "Mobile IPv6 Fast Handovers", 2180 RFC 5268, June 2008, 2181 . 2183 13.2. Informative References 2185 [RFC3290] Bernet, Y., Blake, S., Grossman, D., and A. Smith, "An 2186 Informal Management Model for Diffserv Routers", 2187 RFC 3290, May 2002. 2189 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 2190 Neighbor Discovery (SEND)", RFC 3971, March 2005. 2192 [RFC4068] Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068, 2193 July 2005. 2195 [RFC5184] Teraoka, F., Gogo, K., Mitsuya, K., Shibui, R., and K. 2197 Mitani, "Unified Layer 2 (L2) Abstractions for Layer 3 2198 (L3)-Driven Fast Handover", RFC 5184, May 2008. 2200 [fmipv6] "fmipv6.org : Home Page", http://fmipv6.org . 2202 [mip6-book] Koodli, R. and C. Perkins, "Mobile Internetworking with 2203 IPv6, Chapter 22, John Wiley & Sons.", , July 2007. 2205 [tarzan] "Nautilus6 - Tarzan", 2206 http://software.nautilus6.org/TARZAN/ . 2208 Appendix A. Contributors 2210 This document has its origins in the fast handover design team in the 2211 erstwhile [mobile ip] working group. The members of this design team 2212 in alphabetical order were; Gopal Dommety, Karim El-Malki, Mohammed 2213 Khalil, Charles Perkins, Hesham Soliman, George Tsirtsis, and Alper 2214 Yegin. 2216 Appendix B. Changes since RFC 5268 2218 Defined the Mobility Header format for HI and HAck messages, and 2219 Mobility Header Option format for IPv6 Address/Prefix option. The 2220 use of ICMP for HI and HAck messages is deprecated. 2222 Appendix C. Changes since RFC 4068 2224 Following are the major changes and clarifications: 2226 o Specified security association between the MN and its Access 2227 Router in the companion document [RFC5269]. 2229 o Specified Binding Authorization Data for Fast Handovers (BADF) 2230 option to carry the security parameters used for verifying the 2231 authenticity of FBU and FBack messages. The handover key used for 2232 computing the Authenticator is specified in companion documents. 2234 o Specified the security configuration for inter - access router 2235 signaling (HI, HAck). 2237 o Added a section on prefix management between access routers and 2238 illustrated protocol operation over point-to-point links. 2240 o Deprecated FNA, which is a Mobility Header message. In its place, 2241 the Unsolicited Neighbor Advertisement (UNA) message from RFC 4861 2242 is used. 2244 o Combined the IPv6 Address Option and IPv6 Prefix Option. 2246 o Added description of DAD requirement on NAR when determining NCoA 2247 uniqueness in Section 4, "Protocol Details". 2249 o Added a new code value for gratuitous HAck message to trigger a HI 2250 message. 2252 o Added Option-Code 5 in PrRtAdv message to indicate NETLMM usage. 2254 o Clarified protocol usage when DHCP is used for NCoA formulation 2255 (Sections 6.1.2, 3.1, and 5.2). Added a new Code value (5) in 2256 PrRtAdv (Section 6.1.2). 2258 o Clarified that IPv6 Neighbor Discovery operations are a must in 2259 Section 7, "Related Proto Considerations". 2261 o Clarified "PAR = temporary HA" for FBUs sent by a genuine MN to an 2262 unsuspecting CoA. 2264 Author's Address 2266 Rajeev Koodli (editor) 2267 Starent Networks 2268 USA 2270 EMail: rkoodli@starentnetworks.com