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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MBONED Working Group M. Boucadair, Ed. 3 Internet-Draft France Telecom 4 Intended status: Standards Track J. Qin 5 Expires: October 20, 2013 Cisco 6 Y. Lee 7 Comcast 8 S. Venaas 9 Cisco Systems 10 X. Li 11 CERNET Center/Tsinghua University 12 M. Xu 13 Tsinghua University 14 April 18, 2013 16 IPv6 Multicast Address With Embedded IPv4 Multicast Address 17 draft-ietf-mboned-64-multicast-address-format-05 19 Abstract 21 This document reserves one bit (M-bit) of the unicast prefix-based 22 multicast IPv6 address for ASM and an IPv6 multicast prefix for SSM 23 mode to be used in the context of IPv4-IPv6 interconnection. 25 The document specifies an algorithmic translation of an IPv6 26 multicast address to a corresponding IPv4 multicast address, and vice 27 versa. This algorithmic translation can be used in both IPv4-IPv6 28 translation or encapsulation schemes. 30 Requirements Language 32 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 33 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 34 document are to be interpreted as described in RFC 2119 [RFC2119]. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at http://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on October 20, 2013. 53 Copyright Notice 55 Copyright (c) 2013 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 72 3. IPv4-Embedded IPv6 Multicast Prefix & Address . . . . . . . . 4 73 3.1. ASM Mode . . . . . . . . . . . . . . . . . . . . . . . . 4 74 3.2. SSM Mode . . . . . . . . . . . . . . . . . . . . . . . . 5 75 3.3. IPv4-Embedded IPv6 Multicast Address . . . . . . . . . . 5 76 3.4. Address Translation Algorithm . . . . . . . . . . . . . . 6 77 3.5. Textual Representation . . . . . . . . . . . . . . . . . 6 78 3.6. Source IPv4 Address in the IPv6 Realm . . . . . . . . . . 6 79 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6 80 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 81 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 82 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 83 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 84 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 85 8.2. Informative References . . . . . . . . . . . . . . . . . 8 86 Appendix A. Motivations . . . . . . . . . . . . . . . . . . . . 9 87 A.1. Why an Address Format is Needed for Multicast IPv4-IPv6 88 Interconnection? . . . . . . . . . . . . . . . . . . . . 9 89 A.2. Why Identifying an IPv4-Embedded IPv6 Multicast Address 90 is Required? . . . . . . . . . . . . . . . . . . . . . . 9 91 A.3. Location of the IPv4 Address . . . . . . . . . . . . . . 10 92 Appendix B. Design Considerations . . . . . . . . . . . . . . . 10 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 95 1. Introduction 97 Various solutions (e.g., [I-D.ietf-softwire-mesh-multicast], 98 [I-D.ietf-softwire-dslite-multicast]) have been proposed to allow 99 access to IPv4 multicast content from hosts attached to IPv6-enabled 100 domains. Even if these solutions have distinct applicability scopes 101 (translation vs. encapsulation) and target different use cases, they 102 all make use of specific IPv6 multicast addresses to embed an IPv4 103 multicast address. Particularly, the IPv4-Embedded IPv6 Multicast 104 Address is used as a destination IPv6 address of multicast flows 105 received from an IPv4-enabled domain and injected by the IPv4-IPv6 106 Interconnection Function into an IPv6-enabled domain. It is also 107 used to build an IPv6 multicast state (*, G6) or (S6, G6) 108 corresponding to their (*, G4) or (S4, G4) IPv4 counter parts by the 109 IPv4-IPv6 Interconnection Function. [I-D.ietf-mboned-v4v6-mcast-ps] 110 provides more discussion about issues related to IPv4/IPv6 multicast. 112 This document reserves one bit of the unicast prefix-based multicast 113 IPv6 address ([I-D.ietf-6man-multicast-addr-arch-update]) for Any- 114 Source Multicast (ASM) mode and an IPv6 multicast prefix for Source- 115 Specific Multicast (SSM) mode to be used in the context of IPv4-IPv6 116 interconnection. This document also defines how IPv4-Embedded IPv6 117 Multicast Addresses are constructed. Both IPv4-IPv6 translation and 118 encapsulation schemes can make use of this specification. 120 This specification can be used in conjunction with other extensions 121 such as embedding the rendezvous point [RFC3956]. Unicast prefix- 122 based and embedded-RP techniques are important tools to simplify IPv6 123 multicast deployments. Indeed, unicast prefix-based IPv6 addressing 124 is used in many current IPv6 multicast deployments, and has also been 125 defined for IPv4, and is seen as a very useful technique. Also 126 embedded-RP is used in existing deployments. 128 This document is a companion document to [RFC6052] which focuses 129 exclusively on IPv4-embedded IPv6 unicast addresses. 131 2. Terminology 133 This document makes use of the following terms: 135 o IPv4-Embedded IPv6 Multicast Address: denotes a multicast IPv6 136 address which includes in 32 bits an IPv4 address. 138 o Multicast Prefix64 (or MPREFIX64 for short) refers to an IPv6 139 multicast prefix to be used to construct IPv4-Embedded IPv6 140 Multicast Addresses. This prefix is used to build an 141 IPv4-Embedded IPv6 Multicast Address as defined in Section 3.4. 142 Section 3.4 specifies also how to extract an IPv4 address from an 143 IPv4-Embedded IPv6 Multicast Address. 145 o ASM_MPREFIX64: denotes a multicast Prefix64 used in Any Source 146 Multicast (ASM) mode. 148 o SSM_MPREFIX64: denotes a multicast Prefix64 used in Source 149 Specific Multicast (SSM) mode. 151 o IPv4-IPv6 Interconnection Function: refers to a function which is 152 enabled in a node interconnecting an IPv4-enabled domain with an 153 IPv6-enabled one. It can be located in various places of the 154 multicast network. Particularly, in terms of multicast control 155 messages, it can be an IGMP/MLD Interworking Function or an 156 IPv4-IPv6 PIM Interworking Function. An IPv4-IPv6 Interconnection 157 Function is configured with one or two MPREFIX64s. 159 3. IPv4-Embedded IPv6 Multicast Prefix & Address 161 3.1. ASM Mode 163 The format specified in Figure 1 uses some bits defined in 164 [I-D.ietf-6man-multicast-addr-arch-update]: M-bit (20th bit position) 165 now has a meaning. 167 Details on design considerations are discussed in Appendix B. 169 | 8 | 4 | 4 | 3 |1| 76 | 32 | 170 +--------+----+----+----+-+------------------------------+----------+ 171 |11111111|flgs|scop|flgs|M| sub-group-id |v4 address| 172 +--------+----+----+----+-+-----------------------------------------+ 174 Figure 1: IPv4-Embedded IPv6 Multicast Address Format: ASM Mode 176 The description of the fields is as follows: 178 o "flgs" fields are defined in 179 [I-D.ietf-6man-multicast-addr-arch-update]. 180 o "scop" field is defined in [RFC3956]. 181 o M (20th bit position): When this bit is set to 1, it indicates 182 that a multicast IPv4 address is embedded in the low-order 32 bits 183 of the multicast IPv6 address. 185 o sub-group-id: This field is configurable according to local 186 policies (e.g., enable embedded-RP) of the entity managing the 187 IPv4-IPv6 Interconnection Function. This field MUST follow the 188 recommendations specified in [RFC3306] if unicast-based prefix is 189 used or the recommendations specified in [RFC3956] if embedded-RP 190 is used. The default value is all zeros. 191 o The low-order 32 bits MUST include an IPv4 multicast address when 192 the M-bit is set to 1. The enclosed IPv4 multicast address SHOULD 193 NOT be in 232/8 range. 195 3.2. SSM Mode 197 For SSM mode, and given what is discussed in Appendix B, the 198 following IPv6 prefix to embed IPv4 multicast addresses is reserved: 200 o ff3x:0:8000::/96 ('x' is any valid scope). 202 3.3. IPv4-Embedded IPv6 Multicast Address 204 For the delivery of the IPv4-IPv6 multicast interconnection services, 205 a dedicated multicast prefix denoted as MPREFIX64 should be 206 provisioned (e.g., using NETCONF or 207 [I-D.ietf-softwire-multicast-prefix-option]) to any function 208 requiring to build an IPv4-Embedded IPv6 Multicast Address based on 209 an IPv4 multicast address. MPREFIX64 can be of ASM or SSM type. 210 When both modes are used, two prefixes are required to be 211 provisioned. 213 The length of MPREFIX64 MUST be /96. For SSM, MPREFIX64 MUST be 214 equal to ff3x:0:8000::/96. For the ASM mode, MPREFIX64 MUST have the 215 M-bit set to 1. Furthermore, the format of the ASM_MPREFIX64 should 216 follow what is specified in [RFC3306] and [RFC3956] if corresponding 217 mechanisms are used. If not, bits 21-96 can be set to any value. 219 Figure 2 shows how to build an IPv4-Embedded IPv6 Multicast Address 220 using a configured MPREFIX64 and an IPv4 multicast address. The low- 221 order 32 bits MUST include an IPv4 multicast address. The enclosed 222 IPv4 multicast address SHOULD NOT be in 232/8 range if an 223 ASM_PREFIX64 is configured. The enclosed IPv4 multicast address 224 SHOULD be in 232/8 range if an SSM_PREFIX64 is configured. 226 Embedding an IPv4 multicast address in the last 32 bits does not 227 conflict with the Group IDs assigned by IANA (i.e., 0x00000001 to 228 0x3FFFFFFF [RFC3307]). 230 When several MPREFIX64 are available, it is RECOMMENDED to use the 231 MPREFIX64 which preserve the scope of the IPv4 multicast address. 233 | 96 | 32 | 234 +------------------------------------------------------+----------+ 235 | MPREFIX64 |v4 address| 236 +------------------------------------------------------+----------+ 238 Figure 2: IPv4-Embedded IPv6 Multicast Address Format 240 3.4. Address Translation Algorithm 242 IPv4-Embedded IPv6 Multicast Addresses are composed according to the 243 following algorithm: 245 o Concatenate the MPREFIX64 and the 32 bits of the IPv4 address to 246 obtain a 128-bit address. 248 The IPv4 multicast addresses are extracted from the IPv4-Embedded 249 IPv6 Multicast Addresses according to the following algorithm: 251 o If the multicast address has the 20th bit set to 1 or it matches 252 ff3x:0:8000::/96 or a preconfigured MPREFIX64, extract the last 32 253 bits of the IPv6 multicast address. 255 3.5. Textual Representation 257 The embedded IPv4 address in an IPv6 multicast address is included in 258 the last 32 bits; therefore dotted decimal notation can be used. 260 3.6. Source IPv4 Address in the IPv6 Realm 262 An IPv4 source is represented in the IPv6 realm with its 263 IPv4-converted IPv6 address [RFC6052]. 265 4. Examples 267 Figure 3 provides some examples of ASM IPv4-Embedded IPv6 Address 268 while Figure 4 provides an example of SSM IPv4-Embedded IPv6 Address. 270 IPv4 multicast addresses used in the examples are derived from the 271 IPv4 multicast block reserved for documentation in [RFC6676]. 273 +----------------------+--------------+-----------------------------+ 274 | MPREFIX64 | IPv4 address | IPv4-Embedded IPv6 Address | 275 +----------------------+--------------+-----------------------------+ 276 | ff3x:z000:0:abc::/96 | 233.252.0.1 |ff3x:z000:0:abc::233.252.0.1 | 277 | ff7x:z000:0:abc::/96 | 233.252.0.2 |ff7x:z000:0:abc::233.252.0.2 | 278 +----------------------+--------------+-----------------------------+ 279 where: 281 "x" is any valid scope 282 "z" is any 4 bits where the last bit is set (e.g., 1, 3, 7, ...) 284 Figure 3: Example of ASM IPv4-embedded IPv6 address 286 +---------------------+--------------+----------------------------+ 287 | MPREFIX64 | IPv4 address | IPv4-Embedded IPv6 Address | 288 +---------------------+--------------+----------------------------+ 289 | ff3x:0:8000::/96 | 233.252.0.5 | ff3x:0:8000::233.252.0.5 | 290 +---------------------+--------------+----------------------------+ 292 Figure 4: Example of SSM IPv4-embedded IPv6 address 294 5. IANA Considerations 296 This document requests IANA to reserve: 298 o ff3x:0:8000::/96 SSM range to embed an IPv4 multicast address in 299 the last 32 bits. 301 6. Security Considerations 303 This document defines an algorithmic translation of an IPv6 multicast 304 address into an IPv4 multicast address, and vice versa. The security 305 considerations discussed in [RFC6052] are to be taken into 306 consideration. 308 7. Acknowledgements 310 Many thanks to R. Bonica, B. Sarikaya, P. Savola, T. Tsou, C. 311 Bormann, T. Chown, P. Koch, B. Haberman, and B. Hinden for their 312 comments and review. 314 8. References 316 8.1. Normative References 318 [I-D.ietf-6man-multicast-addr-arch-update] 319 Boucadair, M. and S. Venaas, "Updates to the IPv6 320 Multicast Addressing Architecture", draft-ietf-6man- 321 multicast-addr-arch-update-00 (work in progress), April 322 2013. 324 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 325 Requirement Levels", BCP 14, RFC 2119, March 1997. 327 [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 328 Multicast Addresses", RFC 3306, August 2002. 330 [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast 331 Addresses", RFC 3307, August 2002. 333 [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous 334 Point (RP) Address in an IPv6 Multicast Address", RFC 335 3956, November 2004. 337 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for 338 IP", RFC 4607, August 2006. 340 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 341 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 342 October 2010. 344 8.2. Informative References 346 [I-D.ietf-behave-nat64-learn-analysis] 347 Korhonen, J. and T. Savolainen, "Analysis of solution 348 proposals for hosts to learn NAT64 prefix", draft-ietf- 349 behave-nat64-learn-analysis-03 (work in progress), March 350 2012. 352 [I-D.ietf-mboned-v4v6-mcast-ps] 353 Jacquenet, C., Boucadair, M., Lee, Y., Qin, J., Tsou, T., 354 and Q. Sun, "IPv4-IPv6 Multicast: Problem Statement and 355 Use Cases", draft-ietf-mboned-v4v6-mcast-ps-02 (work in 356 progress), March 2013. 358 [I-D.ietf-softwire-dslite-multicast] 359 Qin, J., Boucadair, M., Jacquenet, C., Lee, Y., and Q. 360 Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients 361 over an IPv6 Multicast Network", draft-ietf-softwire- 362 dslite-multicast-05 (work in progress), April 2013. 364 [I-D.ietf-softwire-mesh-multicast] 365 Xu, M., Cui, Y., Wu, J., Yang, S., Metz, C., and G. 366 Shepherd, "Softwire Mesh Multicast", draft-ietf-softwire- 367 mesh-multicast-04 (work in progress), January 2013. 369 [I-D.ietf-softwire-multicast-prefix-option] 370 Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6 371 Option for IPv4-Embedded Multicast and Unicast IPv6 372 Prefixes", draft-ietf-softwire-multicast-prefix-option-04 373 (work in progress), April 2013. 375 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 376 Description Protocol", RFC 4566, July 2006. 378 [RFC6676] Venaas, S., Parekh, R., Van de Velde, G., Chown, T., and 379 M. Eubanks, "Multicast Addresses for Documentation", RFC 380 6676, August 2012. 382 Appendix A. Motivations 384 A.1. Why an Address Format is Needed for Multicast IPv4-IPv6 385 Interconnection? 387 Arguments why an IPv6 address format is needed to embed multicast 388 IPv4 address are quite similar to those of [RFC6052]. Concretely, 389 the definition of a multicast address format embedding a multicast 390 IPv4 address allows: 392 o Stateless IPv4-IPv6 header translation of multicast flows; 394 o Stateless IPv4-IPv6 PIM interworking function; 396 o Stateless IGMP-MLD interworking function (e.g., required for an 397 IPv4 receiver to access to IPv4 multicast content via an IPv6 398 network); 400 o Stateless (local) synthesis of IPv6 address when IPv4 multicast 401 address are embedded in application payload (e.g., SDP [RFC4566]); 403 o Except the provisioning of the same MPREFIX64, no coordination is 404 required between IPv4-IPv6 PIM interworking function, IGMP-MLD 405 interworking function, IPv4-IPv6 Interconnection Function and any 406 ALG (Application Level Gateway) in the path; 408 o Minimal operational constraints on the multicast address 409 management: IPv6 multicast addresses can be constructed using what 410 has been deployed for IPv4 delivery mode. 412 A.2. Why Identifying an IPv4-Embedded IPv6 Multicast Address is 413 Required? 415 Reserving a dedicated multicast prefix for IPv4-IPv6 interconnection 416 purposes is a means to guide the address selection process at the 417 receiver side; in particular it assists the receiver to select the 418 appropriate IP multicast address while avoiding to involve an 419 IPv4-IPv6 interconnection function in the path. 421 Two use cases to illustrate this behavior are provided below: 423 1. An ALG is required to help an IPv6 receiver to select the 424 appropriate IP address when only the IPv4 address is advertised 425 (e.g., using SDP); otherwise the access to the IPv4 multicast 426 content can not be offered to the IPv6 receiver. The ALG may be 427 located downstream the receiver. As such, the ALG does not know 428 in advance whether the receiver is dual-stack or IPv6-only. The 429 ALG may be tuned to insert both the original IPv4 address and 430 corresponding IPv6 multicast address. If a dedicated prefix is 431 not used, a dual-stack receiver may prefer to use the IPv6 432 address to receive the multicast content. This address selection 433 would require multicast flows to cross an IPv4-IPv6 434 interconnection function. 436 2. In order to avoid involving an ALG in the path, an IPv4-only 437 source can advertise both its IPv4 address and IPv4-Embedded IPv6 438 Multicast Address. If a dedicated prefix is not reserved, a 439 dual-stack receiver may prefer to use the IPv6 address to receive 440 the multicast content. This address selection would require 441 multicast flows to cross an IPv4-IPv6 interconnection function. 443 Reserving dedicated IPv6 multicast prefixes for IPv4-IPv6 444 interconnection purposes mitigates the issues discussed in 445 [I-D.ietf-behave-nat64-learn-analysis] in a multicast context. 447 A.3. Location of the IPv4 Address 449 There is no strong argument to allow for flexible options to encode 450 the IPv4 address inside the multicast IPv6 address. The option 451 retained by the authors is to encode the multicast IPv4 address in 452 the low-order 32 bits of the IPv6 address. 454 This choice is also motivated by the need to be compliant with 455 [RFC3306] and [RFC3956]. 457 Appendix B. Design Considerations 459 The following constraints should be met when reserving dedicated 460 prefix(es) to be used for IPv4/IPv6 multicast interconnection: 462 1: Belong to SSM prefix range (preferably ff3x::/32) and be 463 compatible with unicast-based prefix [RFC3306] for SSM. Note that 464 [RFC3306] suggests to set "plen" to 0 and "network-prefix" to 0. 465 As such, any prefix in the 33-96 range can be convenient. Given 466 [RFC4607] indicates future specifications may allow a non-zero 467 network prefix field, a /33 would allow for future extensions but 468 it has the drawback of reserving a large block. A /96 would be 469 adequate for the use cases already identified in 470 [I-D.ietf-mboned-v4v6-mcast-ps]. In the event of any concrete 471 extension, reserving additional prefixes may be considered. 473 2: Be compatible with embedded-RP [RFC3956] and unicast-based prefix 474 [RFC3306] for ASM. This results in associating a meaning with one 475 of the reserved bits in 476 [I-D.ietf-6man-multicast-addr-arch-update]. Defining the 17-20 477 bits range to have a meaning and be used for IPv4/IPv6 transition 478 has the advantage of allowing for future extensions but it may be 479 seen as a waste of the multicast address space. Consequently, 480 using one of the reserved bits (in the range 17-20) from the 481 unicast-based IPv6 multicast address format [RFC3306] is 482 preferred. 484 Meeting (1) and (2) with the same reserved bit is not feasible 485 without modifying embedded-RP and unicast-based prefix 486 specifications; this option is avoided. 488 As a consequence, this document proposes to reserve a multicast 489 prefix for SSM and define one bit of the unicast prefix-based 490 multicast IPv6 address for ASM when embedding IPv4 multicast address 491 in an IPv6 multicast address. 493 Authors' Addresses 495 Mohamed Boucadair (editor) 496 France Telecom 497 Rennes 35000 498 France 500 Email: mohamed.boucadair@orange.com 502 Jacni Qin 503 Cisco 504 China 506 Email: jacni@jacni.com 508 Yiu L. Lee 509 Comcast 510 U.S.A 512 Email: yiu_lee@cable.comcast.com 513 Stig Venaas 514 Cisco Systems 515 Tasman Drive 516 San Jose, CA 95134 517 USA 519 Email: stig@cisco.com 521 Xing Li 522 CERNET Center/Tsinghua University 523 Room 225, Main Building, Tsinghua University 524 Beijing 100084 525 P.R. China 527 Phone: +86 10-62785983 528 Email: xing@cernet.edu.cn 530 Mingwei Xu 531 Tsinghua University 532 Department of Computer Science, Tsinghua University 533 Beijing 100084 534 P.R.China 536 Phone: +86-10-6278-5822 537 Email: xmw@cernet.edu.cn