idnits 2.17.1 draft-ietf-softwire-dslite-multicast-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 15, 2014) is 3483 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4601 (Obsoleted by RFC 7761) == Outdated reference: A later version (-15) exists of draft-ietf-softwire-multicast-prefix-option-06 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Softwire WG J. Qin 3 Internet-Draft Cisco 4 Intended status: Standards Track M. Boucadair 5 Expires: March 19, 2015 C. Jacquenet 6 France Telecom 7 Y. Lee 8 Comcast 9 Q. Wang 10 China Telecom 11 September 15, 2014 13 Delivery of IPv4 Multicast Services to IPv4 Clients over an IPv6 14 Multicast Network 15 draft-ietf-softwire-dslite-multicast-08 17 Abstract 19 This document specifies a solution for the delivery of IPv4 multicast 20 services to IPv4 clients over an IPv6 multicast network. The 21 solution relies upon a stateless IPv4-in-IPv6 encapsulation scheme 22 and uses the IPv6 multicast distribution tree to deliver IPv4 23 multicast traffic. The solution is particularly useful for the 24 delivery of multicast service offerings to DS-Lite serviced 25 customers. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on March 19, 2015. 44 Copyright Notice 46 Copyright (c) 2014 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5 66 4.1. IPv4-Embedded IPv6 Prefixes . . . . . . . . . . . . . . . 6 67 4.2. Multicast Distribution Tree Computation . . . . . . . . . 7 68 4.3. Multicast Data Forwarding . . . . . . . . . . . . . . . . 8 69 5. Address Mapping . . . . . . . . . . . . . . . . . . . . . . . 8 70 5.1. Prefix Assignment . . . . . . . . . . . . . . . . . . . . 8 71 5.2. Address Translation Algorithm . . . . . . . . . . . . . . 9 72 5.3. Textual Representation . . . . . . . . . . . . . . . . . 9 73 5.4. Examples . . . . . . . . . . . . . . . . . . . . . . . . 9 74 6. Multicast B4 (mB4) . . . . . . . . . . . . . . . . . . . . . 10 75 6.1. IGMP-MLD Interworking Function . . . . . . . . . . . . . 10 76 6.2. Multicast Data Forwarding . . . . . . . . . . . . . . . . 10 77 6.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 11 78 6.4. Host built-in mB4 Function . . . . . . . . . . . . . . . 11 79 6.5. Preserve the Scope . . . . . . . . . . . . . . . . . . . 11 80 7. Multicast AFTR (mAFTR) . . . . . . . . . . . . . . . . . . . 11 81 7.1. Routing Considerations . . . . . . . . . . . . . . . . . 11 82 7.2. Processing PIM Message . . . . . . . . . . . . . . . . . 12 83 7.3. Switching from Shared Tree to Shortest Path Tree . . . . 13 84 7.4. Multicast Data Forwarding . . . . . . . . . . . . . . . . 13 85 7.5. TTL/Scope . . . . . . . . . . . . . . . . . . . . . . . . 13 86 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 87 8.1. Firewall Configuration . . . . . . . . . . . . . . . . . 14 88 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 89 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 90 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 91 11.1. Normative References . . . . . . . . . . . . . . . . . . 14 92 11.2. Informative References . . . . . . . . . . . . . . . . . 15 93 Appendix A. Use Case: IPTV . . . . . . . . . . . . . . . . . . . 16 94 Appendix B. Deployment Considerations . . . . . . . . . . . . . 16 95 B.1. Other operational Modes . . . . . . . . . . . . . . . . . 16 96 B.1.1. MLD Querier with mAFTR Embedded . . . . . . . . . . . 17 97 B.1.2. mAFTR embedded in DR . . . . . . . . . . . . . . . . 17 98 B.2. Older Version of Group Membership management Protocols . 17 99 B.3. Load-Balancing . . . . . . . . . . . . . . . . . . . . . 17 100 B.4. RP for IPv4-Embedded IPv6 Multicast Groups . . . . . . . 18 101 B.5. mAFTR Policy Configuration . . . . . . . . . . . . . . . 18 102 B.6. Static vs. Dynamic PIM Triggering . . . . . . . . . . . . 18 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 105 1. Introduction 107 DS-Lite [RFC6333] is a technique that rationalizes the usage of the 108 remaining global IPv4 addresses during the transition period by 109 sharing a single IPv4 address with multiple users. A typical DS-Lite 110 scenario is the delivery of an IPv4 service to an IPv4 user over an 111 IPv6 network (denoted as a 4-6-4 scenario). [RFC6333] covers unicast 112 services exclusively. A more generic problem statement is sketched 113 in [I-D.ietf-mboned-v4v6-mcast-ps]. 115 This document specifies a generic solution for delivery of IPv4 116 multicast services to IPv4 clients over an IPv6 multicast network. 117 The solution was developed with DS-Lite in mind (see more discussion 118 below). The solution is however not limited to DS-Lite. 120 If customers have to access IPv4 multicast-based services through DS- 121 Lite environment, Address Family Transition Router (AFTR) devices 122 will have to process all the IGMP Report messages [RFC2236] [RFC3376] 123 that have been forwarded by the CPE into the IPv4-in-IPv6 tunnels. 124 From that standpoint, AFTR devices are likely to behave as a 125 replication point for downstream multicast traffic. And the 126 multicast packets will be replicated for each tunnel endpoint where 127 IPv4 receivers are connected to. 129 This kind of DS-Lite environment raises two major issues: 131 1. The IPv6 network loses the benefits of the multicast traffic 132 forwarding efficiency because it is unable to deterministically 133 replicate the data as close to the receivers as possible. As a 134 consequence, the downstream bandwidth in the IPv6 network will be 135 vastly consumed by sending multicast data over a unicast 136 infrastructure. 138 2. The AFTR is responsible for replicating multicast traffic and 139 forwarding it into each tunnel endpoint connecting IPv4 receivers 140 that have explicitly asked for the corresponding contents. This 141 process may greatly consume AFTR's resources and overload the 142 AFTR. 144 This document specifies an extension to the DS-Lite model to deliver 145 IPv4 multicast services to IPv4 clients over an IPv6 multicast- 146 enabled network. 148 1.1. Requirements Language 150 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 151 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 152 document are to be interpreted as described in RFC 2119 [RFC2119]. 154 2. Terminology 156 This document makes use of the following terms: 158 o IPv4-embedded IPv6 address: is an IPv6 address which embeds a 32- 159 bit-encoded IPv4 address. An IPv4-embedded IPv6 address can be 160 unicast or multicast. 162 o mPrefix64: is a dedicated multicast IPv6 prefix for constructing 163 IPv4-embedded IPv6 multicast addresses. mPrefix64 can be of two 164 types: ASM_mPrefix64 used in Any Source Multicast (ASM) mode or 165 SSM_mPrefix64 used in Source Specific Multicast (SSM) mode 166 [RFC4607]. 168 o uPrefix64: is a dedicated IPv6 unicast prefix for constructing 169 IPv4-embedded IPv6 unicast addresses [RFC6052]. 171 o Multicast AFTR (mAFTR): is a functional entity which supports 172 IPv4-IPv6 multicast interworking function (refer to Figure 3). It 173 receives and encapsulates the IPv4 multicast packets into IPv4-in- 174 IPv6 packets and behaves as the corresponding IPv6 multicast 175 source for the encapsulated IPv4-in-IPv6 packets. 177 o Multicast B4 (mB4): is a functional entity which supports an IGMP- 178 MLD interworking function (refer to Section 6.1) that relays 179 information conveyed in IGMP messages by forwarding the 180 corresponding MLD messages towards the MLD Querier in the IPv6 181 network. In addition, the mB4 decapsulates IPv4-in-IPv6 multicast 182 packets. 184 o PIMv4: refers to PIM when deployed in an IPv4 infrastructure 185 (i.e., IPv4 transport capabilities are used to exchange PIM 186 messages). 188 o PIMv6: refers to PIM when deployed in an IPv6 infrastructure 189 (i.e., IPv6 transport capabilities are used to exchange PIM 190 messages). 192 3. Scope 194 This document focuses only on subscription to an IPv4 multicast group 195 and the delivery of IPv4-formatted content to IPv4 receivers over an 196 IPv6-only network. In particular, only the following case is 197 covered: 199 An IPv4 receiver accesses IPv4 multicast contents over an IPv6- 200 only multicast-enabled network. 202 This document does not cover the source/receiver heuristics, where as 203 IPv4 receiver can also behave as an IPv4 multicast source. This 204 document assumes that hosts behind the mB4 are IPv4 multicast 205 receivers only. 207 4. Solution Overview 209 In the original DS-Lite specification [RFC6333], an IPv4-in-IPv6 210 tunnel is used to carry bidirectional IPv4 unicast traffic between a 211 B4 and an AFTR. The solution specified in this document provides an 212 IPv4-in-IPv6 encapsulation scheme to deliver unidirectional IPv4 213 multicast traffic from an mAFTR to an mB4. 215 An overview of the solution is provided in this section which is 216 intended as an introduction to how it works, but is NOT normative. 217 For the normative specifications of the two new functional elements: 218 mB4 and mAFTR (Figure 1), refer to Section 6 and Section 7. 220 ------------ 221 / \ 222 | IPv4 network | 223 \ / 224 ------------ 225 IPv4 multicast : | ^ PIMv4 Join 226 v | : 227 +-------------+ 228 | mAFTR | 229 +-------------+ 230 IPv6 multicast |:| | ^ PIMv6 Join (PIMv6 231 (IPv4 embedded) |:| | : routers in between) 232 ------------ 233 / \ 234 | IPv6 network | 235 \ / 236 ------------ 237 |:| | : MLD Report 238 |v| | : 239 +-----------+ 240 | mB4 | 241 +-----------+ 242 IPv4 multicast : | ^ IGMP Report 243 v | : 244 +-----------+ 245 | IPv4 | 246 | receiver | 247 +-----------+ 249 Figure 1: Functional Architecture 251 4.1. IPv4-Embedded IPv6 Prefixes 253 In order to map the addresses of IPv4 multicast traffic with IPv6 254 multicast addresses, an IPv6 multicast prefix (mPrefix64) and an IPv6 255 unicast prefix (uPrefix64) are provided to mAFTR and mB4 elements, 256 both of which contribute to the computation and the maintenance of 257 the IPv6 multicast distribution tree that extends the IPv4 multicast 258 distribution tree into the IPv6 multicast network. 260 The mAFTR and mB4 use mPrefix64 to convert an IPv4 multicast address 261 (G4) to an IPv4-embedded IPv6 multicast address (G6). The mAFTR and 262 mB4 use uPrefix64 to convert an IPv4 multicast source address (S4) to 263 an IPv4-embedded IPv6 address (S6). The mAFTR and mB4 MUST use the 264 same mPrefix64 and uPrefix64, as well as run the same algorithm for 265 building IPv4-embedded IPv6 addresses. Refer to Section 5 for more 266 details about the address mapping. 268 4.2. Multicast Distribution Tree Computation 270 When an IPv4 receiver connected to the device that embeds the mB4 271 capability wants to subscribe to an IPv4 multicast group, it sends an 272 IGMP Report message to the mB4. The mB4 creates the IPv6 multicast 273 group (G6) address using mPrefix64 and the original IPv4 multicast 274 group address. If the receiver sends a source-specific IGMPv3 Report 275 message, the mB4 will create the IPv6 source address (S6) using 276 uPrefix64 and the original IPv4 source address. 278 The mB4 uses the G6 (and both S6 and G6 in SSM) to create the 279 corresponding MLD Report message. The mB4 sends the Report message 280 to the MLD Querier in the IPv6 network. The MLD Querier (typically 281 acts as the PIMv6 Designated Router) receives the MLD Report message 282 and sends the PIMv6 Join to join the IPv6 multicast distribution 283 tree. The MLD Querier can send either PIMv6 Join (*,G6) in ASM or 284 PIMv6 Join (S6,G6) in SSM to the mAFTR. 286 The mAFTR acts as the DR to which the uPrefix64-derived S6 is 287 connected. The mAFTR will receive the source-specific PIMv6 Join 288 message (S6,G6) from the IPv6 multicast network. If the mAFTR is the 289 Rendezvous Point (RP) of G6, it will receive the any-source PIMv6 290 Join message (*,G6) from the IPv6 multicast network. If the mAFTR is 291 not the RP of G6, it will send the PIM Register message to the RP of 292 G6 located in the IPv6 multicast network. 294 When the mAFTR receives the PIMv6 Join message (*,G6), it will 295 extract the IPv4 multicast group address (G4). If the mAFTR is the 296 RP of G4 in the IPv4 multicast network, it will create a (*,G4) entry 297 (if there is not yet an existing one) in its own IPv4 multicast 298 routing table. If the mAFTR is not the RP of G4, it will send the 299 corresponding PIMv4 Join message (*,G4) towards the RP of G4 in the 300 IPv4 multicast network. 302 When the mAFTR receives the PIMv6 Join message (S6,G6), it will 303 extract the IPv4 multicast group address (G4) and IPv4 source address 304 (S4) and send the corresponding (S4,G4) PIMv4 Join message directly 305 to the IPv4 source. 307 A branch of the multicast distribution tree is constructed, 308 comprising both an IPv4 part (from the mAFTR upstream) and an IPv6 309 part (from mAFTR downstream to the mB4). 311 The mAFTR MUST advertise the route of uPrefix64 with an IPv6 IGP, so 312 as to represent the IPv4-embedded IPv6 source in the IPv6 multicast 313 network, and to pass the Reverse Path Forwarding (RPF) check on 314 multicast devices. 316 4.3. Multicast Data Forwarding 318 When the mAFTR receives an IPv4 multicast packet, it will encapsulate 319 the packet into an IPv6 multicast packet using the IPv4-embedded IPv6 320 multicast address as the destination address and an IPv4-embedded 321 IPv6 unicast address as the source address. The encapsulated IPv6 322 multicast packet will be forwarded down the IPv6 multicast 323 distribution tree and the mB4 will eventually receive the packet. 325 The IPv6 multicast network treats the IPv4-in-IPv6 encapsulated 326 multicast packets as native. The IPv6 multicast routers use the 327 outer IPv6 header to make forwarding decisions. 329 When the mB4 receive the IPv6 multicast packet (to G6) derived by 330 mPrefix64, it MUST decapsulate it and forward the original IPv4 331 multicast packet to the receivers subscribing to G4. 333 Note: At this point, only IPv4-in-IPv6 encapsulation is defined; 334 however, other types of encapsulation could be defined in the future. 336 5. Address Mapping 338 5.1. Prefix Assignment 340 A dedicated IPv6 multicast prefix (mPrefix64) is provisioned to the 341 mAFTR and the mB4. The mAFTR and the mB4 use the mPrefix64 to form 342 an IPv6 multicast group address from an IPv4 multicast group address. 343 The mPrefix64 can be of two types: ASM_mPrefix64 (a mPrefix64 used in 344 ASM mode) or SSM_mPrefix64 (a mPrefix64 used in SSM mode). The 345 mPrefix64 MUST be derived from the corresponding IPv6 multicast 346 address space (e.g., the SSM_mPrefix64 MUST be in the range of 347 multicast address space specified in [RFC4607]). 349 The IPv6 part of the multicast distribution tree can be seen as an 350 extension of the IPv4 part of the multicast distribution tree. The 351 IPv4 multicast source address MUST be mapped to an IPv6 multicast 352 source address. An IPv6 unicast prefix (uPrefix64) is provisioned to 353 the mAFTR and the mB4. The mAFTR and the mB4 use the uPrefix64 to 354 form an IPv6 multicast source address from an IPv4 multicast source 355 address. The uPrefix-formed IPv6 multicast source address will 356 represent the original IPv4 multicast source in the IPv6 multicast 357 network. The uPrefix64 MUST be derived from the IPv6 unicast address 358 space. 360 The address translation MUST follow the algorithm defined in 361 Section 5.2. 363 The mPrefix64 and uPrefix64 can be configured in the mB4 using a 364 variety of methods, including an out-of-band mechanism, manual 365 configuration, or a dedicated provisioning protocol (e.g., using 366 DHCPv6 [I-D.ietf-softwire-multicast-prefix-option]). 368 5.2. Address Translation Algorithm 370 IPv4-Embedded IPv6 multicast addresses are composed according to the 371 following algorithm: 373 o Concatenate the mPrefix64 and the 32 bits of the IPv4 address to 374 obtain a 128-bit address. 376 The IPv4 multicast addresses are extracted from the IPv4-Embedded 377 IPv6 Multicast Addresses according to the following algorithm: 379 o If the multicast address has a pre-configured mPrefix64, extract 380 the last 32 bits of the IPv6 multicast address. 382 An IPv4 source is represented in the IPv6 realm with its 383 IPv4-converted IPv6 address [RFC6052]. 385 5.3. Textual Representation 387 The embedded IPv4 address in an IPv6 multicast address is included in 388 the last 32 bits; therefore dotted decimal notation can be used. 390 5.4. Examples 392 Group address mapping example: 394 +---------------------+--------------+----------------------------+ 395 | mPrefix64 | IPv4 address | IPv4-Embedded IPv6 address | 396 +---------------------+--------------+----------------------------+ 397 | ff0x::db8:0:0/96 | 233.252.0.1 | ff0x::db8::233.252.0.1 | 398 +---------------------+--------------+----------------------------+ 400 Source address mapping example when a /96 is used: 402 +---------------------+--------------+----------------------------+ 403 | uPrefix64 | IPv4 address | IPv4-Embedded IPv6 address | 404 +---------------------+--------------+----------------------------+ 405 | 2001:db8::/96 | 192.0.2.33 | 2001:db8::192.0.2.33 | 406 +---------------------+--------------+----------------------------+ 408 IPv4 and IPv6 addresses used in this example are derived from the 409 IPv4 and IPv6 blocks reserved for documentation, as per [RFC6676]. 411 The unicast IPv4 address of the above example is derived from the 412 documentation address block defined in [RFC6890]. 414 6. Multicast B4 (mB4) 416 6.1. IGMP-MLD Interworking Function 418 The IGMP-MLD Interworking Function combines the IGMP/MLD Proxying 419 function and the address synthesizing operations. The IGMP/MLD 420 Proxying function is specified in [RFC4605]. The address translation 421 is stateless and MUST follow the address mapping specified in 422 Section 5. 424 The mB4 with the IGMP-MLD Interworking Function embedded relays 425 between the IGMP domain and the MLD domain. The mB4 performs the 426 host portion of the MLD protocol on the upstream interface. The 427 composition of IPv6 membership in this context is constructed through 428 address synthesizing operations and MUST synchronize with the 429 membership database maintained in the IGMP domain. MLD messages will 430 be forwarded natively towards the MLD Querier located upstream in the 431 IPv6 network. The mB4 also performs the router portion of the IGMP 432 protocol on the downstream interface(s). Refer to [RFC4605] for more 433 details 435 +----------+ IGMP +-------+ MLD +---------+ 436 | IPv4 |---------| mB4 |---------| MLD | 437 | Receiver | | | | Querier | 438 +----------+ +-------+ +---------+ 440 Figure 2: IGMP-MLD Interworking 442 If SSM is deployed, the mB4 MUST construct the IPv6 source address 443 (or retrieve the IPv4 source address) using the uPrefix64. The mB4 444 may create a membership database which associates the IPv4-IPv6 445 multicast groups with the interfaces (e.g., Wi-Fi and Wired Ethernet) 446 facing IPv4 multicast receivers. 448 6.2. Multicast Data Forwarding 450 When the mB4 receives an IPv6 multicast packet, it MUST check the 451 group address and the source address. If the IPv6 multicast group 452 prefix is mPrefix64 and the IPv6 source prefix is uPrefix64, the mB4 453 MUST de-capsulate the IPv6 header and forward the IPv4 multicast 454 packet through each relevant interface. Otherwise, the mB4 MUST drop 455 the packet silently. 457 As an illustration, if a packet is received from source 458 2001:db8::192.0.2.33 and to be forwarded to group 459 ff3x:1000::233.252.0.1, the mB4 will de-capsulate it into an IPv4 460 multicast packet using 192.0.2.33 as the IPv4 multicast source 461 address and using 233.252.0.1 as the IPv4 destination address. 463 6.3. Fragmentation 465 Encapsulating IPv4 multicast packets into IPv6 multicast packets that 466 will be forwarded by the mAFTR to the mB4 along the IPv6 multicast 467 distribution tree reduces the effective MTU size by the size of an 468 IPv6 header. In this specification, the data flow is unidirectional 469 from mAFTR to mB4, the mAFTR MUST fragment the oversized IPv6 packet 470 after the encapsulation into two IPv6 packets. The mB4 MUST 471 reassemble the IPv6 packets, decapsulate the IPv6 packet, and forward 472 the IPv4 packet to the hosts subscribing the multicast group. 473 Further considerations about fragmentation issues are documented in 474 [RFC6333]. 476 6.4. Host built-in mB4 Function 478 If the mB4 function is implemented in the host which is directly 479 connected to an IPv6-only network, the host MUST implement 480 Section 6.1, Section 6.2, and Section 6.3. The host MAY optimize the 481 implementation to provide an Application Programming Interface (API) 482 or kernel module to skip the IGMP-MLD Interworking Function. The 483 optimization is out of scope of the specification. 485 6.5. Preserve the Scope 487 When several mPrefix64s are available, if each enclosed IPv4-embedded 488 IPv6 multicast prefix has a distinct scope, mB4 MUST select the 489 appropriate IPv4-embedded IPv6 multicast prefix having a scope 490 matching the IPv4 multicast address used to synthesize an 491 IPv4-embedded IPv6 multicast address. 493 The mB4 MAY be configured to not preserve the scope when enforcing 494 the address translation algorithm. 496 7. Multicast AFTR (mAFTR) 498 7.1. Routing Considerations 500 The mAFTR is responsible for interconnecting the IPv4 multicast 501 distribution tree with the corresponding IPv6 multicast distribution 502 tree. The mAFTR MUST use the uPrefix64 to build the IPv6 source 503 addresses of the multicast group address derived from mPrefix64. In 504 other words, the mAFTR MUST be the multicast source derived from 505 uPrefix64. 507 The mAFTR MUST advertise the route of uPrefix64 to the IPv6 IGP. 508 This is needed for the IPv6 multicast routers to have routing 509 information to discover the source. 511 7.2. Processing PIM Message 513 The mAFTR MUST interwork PIM Join/Prune messages for (*, G6) and (S6, 514 G6) on their corresponding (*, G4) and (S4, G4). The following text 515 specifies the expected behavior of mAFTR for PIM Join message. 517 +---------+ 518 ---------| mAFTR |--------- 519 PIMv6 |uPrefix64| PIMv4 520 |mPreifx64| 521 +---------+ 523 Figure 3: PIMv6-PIMv4 Interworking Function 525 The mAFTR contains two separate Tree Information Base (TIB): IPv4 526 Tree Information Base (TIB4) and IPv6 Tree Information Base (TIB6), 527 which are bridged by one IPv4-in-IPv6 virtual interface. It should 528 be noted that the implementations may vary (e.g., using one 529 integrated TIB without any virtual interface), while they should 530 follow the specification herein for the consistency of overall 531 functionality. 533 When a mAFTR receives a PIMv6 Join message (*,G6) with an IPv6 534 multicast group address (G6) that is derived from the mPrefix64, it 535 MUST check its IPv6 Tree Information Base (TIB6). If there is an 536 entry for this G6, it MUST check whether the interface through which 537 the PIMv6 Join message has been received is on the outgoing interface 538 list. If not, the mAFTR MUST add the interface to the outgoing 539 interface list. If there is no entry in the TIB6, the mAFTR MUST 540 create a new entry (*,G6) for the multicast group. While, whether or 541 not to set the IPv4-in-IPv6 virtual interface as the incoming 542 interface of the newly created entry is up to the implementation but 543 should comply with the mAFTR's behavior of multicast data forwarding, 544 see Section 7.4. 546 The mAFTR MUST extract the IPv4 multicast group address (G4) from the 547 IPv4-embedded IPv6 multicast address (G6) contained in the PIMv6 Join 548 message. The mAFTR MUST check its IPv4 Tree Information Base (TIB4). 549 If there is an entry for G4, it MUST check whether the IPv4-in-IPv6 550 virtual interface is on the outgoing interface list. If not, the 551 mAFTR MUST add the interface to the outgoing interface list. If 552 there is no entry for G4, the mAFTR MUST create a new (*,G4) entry in 553 its TIB4 and initiate the procedure for building the shared tree in 554 the IPv4 multicast network without any additional requirement. 556 If mAFTR receives a source-specific Join message, the (S6, G6) will 557 be processed rather than (*,G6). The procedures of processing 558 (S6,G6) and (*,G6) are almost the same. Differences have been 559 detailed in [RFC4601]. 561 7.3. Switching from Shared Tree to Shortest Path Tree 563 When the mAFTR receives the first IPv4 multicast packet, it may 564 extract the multicast source address (S4) from the packet and send an 565 Explicit PIMv4 (S4,G4) Join message directly to S4. The mAFTR will 566 switch from the shared Rendezvous Point Tree (RPT) to the Shortest 567 Path Tree (SPT) for G4. 569 For IPv6 multicast routers to switch to the SPT, there is no new 570 requirement. IPv6 multicast routers may send an Explicit PIMv6 Join 571 to mAFTR once the first (S6,G6) multicast packet arrives from 572 upstream multicast routers. 574 7.4. Multicast Data Forwarding 576 When the mAFTR receives an IPv4 multicast packet, it will look up the 577 TIB4 to find a matching entry and then forward the packet to the 578 interface(s) on the outgoing interface list. If the IPv4-in-IPv6 579 virtual interface also belongs to this list, the packet will be 580 encapsulated with the mPrefix64-derived and uPrefix64-derived 581 IPv4-embedded IPv6 addresses to form an IPv6 multicast packet. Then 582 another lookup is executed to find a matching entry in the TIB6, 583 while whether or not to perform RPF check for the second lookup is up 584 to the implementation and is out of the scope of this document. The 585 IPv6 multicast packet is forwarded along the IPv6 multicast 586 distribution tree, based upon the outgoing interface list of the 587 matching entry in the TIB6. 589 As an illustration, if a packet is received from source 192.0.2.33 590 and to be forwarded to group 233.252.0.1, the mAFTR encapsulates it 591 into an IPv6 multicast packet using ff3x:1000::233.252.0.1 as the 592 IPv6 destination address and using 2001:db8::192.0.2.33 as the IPv6 593 multicast source address. 595 7.5. TTL/Scope 597 The Scope field of IPv4-in-IPv6 multicast addresses should be valued 598 accordingly (e.g, to "E", Global scope;) in the deployment 599 environment. This specification does not discuss the scope value 600 that should be used. 602 Nevertheless, when several mPrefix64s are available, if each enclosed 603 IPv4-embedded IPv6 multicast prefix has a distinct scope, mAFTR MUST 604 select the appropriate IPv4-embedded IPv6 multicast prefix having a 605 scope matching the IPv4 multicast address used to synthesize an 606 IPv4-embedded IPv6 multicast address. 608 mAFTR MAY be configured to not preserve the scope when enforcing the 609 address translation algorithm. 611 8. Security Considerations 613 A part for multicast scoping considerations (see Section 6.5 and 614 Section 7.5), this document does not introduce any new security 615 concern in addition to what is discussed in Section 5 of [RFC6052], 616 Section 10 of [RFC3810] and Section 6 of [RFC4601]. 618 mB4 SHOULD be provided with appropriate configuration to enable 619 preserving the scope of a multicast message when mapping an IPv4 620 multicast address into an IPv4-embedded IPv6 multicast address and 621 vice versa. 623 8.1. Firewall Configuration 625 The CPE that embeds the mB4 function SHOULD be configured to accept 626 incoming MLD messages and traffic forwarded to multicast groups 627 subscribed by receivers located in the customer premises. 629 9. Acknowledgements 631 The authors would like to thank Dan Wing for his guidance in the 632 early discussions which initiated this work. We also thank Peng Sun, 633 Jie Hu, Qiong Sun, Lizhong Jin, Alain Durand, Dean Cheng, Behcet 634 Sarikaya, Tina Tsou, Rajiv Asati, Xiaohong Deng and S. Venaas for 635 their valuable comments. 637 10. IANA Considerations 639 This document includes no request to IANA. 641 11. References 643 11.1. Normative References 645 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 646 Requirement Levels", BCP 14, RFC 2119, March 1997. 648 [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. 649 Thyagarajan, "Internet Group Management Protocol, Version 650 3", RFC 3376, October 2002. 652 [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery 653 Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. 655 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 656 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 657 Protocol Specification (Revised)", RFC 4601, August 2006. 659 [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, 660 "Internet Group Management Protocol (IGMP) / Multicast 661 Listener Discovery (MLD)-Based Multicast Forwarding 662 ("IGMP/MLD Proxying")", RFC 4605, August 2006. 664 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for 665 IP", RFC 4607, August 2006. 667 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 668 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 669 October 2010. 671 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 672 Stack Lite Broadband Deployments Following IPv4 673 Exhaustion", RFC 6333, August 2011. 675 11.2. Informative References 677 [I-D.ietf-mboned-multiaaa-framework] 678 Satou, H., Ohta, H., Hayashi, T., Jacquenet, C., and H. 679 He, "AAA and Admission Control Framework for 680 Multicasting", draft-ietf-mboned-multiaaa-framework-12 681 (work in progress), August 2010. 683 [I-D.ietf-mboned-v4v6-mcast-ps] 684 Jacquenet, C., Boucadair, M., Lee, Y., Qin, J., Tsou, T., 685 and Q. Qiong, "IPv4-IPv6 Multicast: Problem Statement and 686 Use Cases", draft-ietf-mboned-v4v6-mcast-ps-04 (work in 687 progress), September 2013. 689 [I-D.ietf-softwire-multicast-prefix-option] 690 Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6 691 Option for IPv4-Embedded Multicast and Unicast IPv6 692 Prefixes", draft-ietf-softwire-multicast-prefix-option-06 693 (work in progress), March 2014. 695 [RFC2236] Fenner, W., "Internet Group Management Protocol, Version 696 2", RFC 2236, November 1997. 698 [RFC6676] Venaas, S., Parekh, R., Van de Velde, G., Chown, T., and 699 M. Eubanks, "Multicast Addresses for Documentation", RFC 700 6676, August 2012. 702 [RFC6890] Cotton, M., Vegoda, L., Bonica, R., and B. Haberman, 703 "Special-Purpose IP Address Registries", BCP 153, RFC 704 6890, April 2013. 706 Appendix A. Use Case: IPTV 708 IPTV generally includes two categories of service offerings: 710 o Video on Demand (VoD) that unicast video content to receivers. 712 o Multicast live TV broadcast services. 714 Two players intervene in the delivery of this service: 716 o Content Providers, who usually own the contents that is multicast 717 to receivers. Content providers may contractually define an 718 agreement with network providers to deliver contents to receivers. 720 o Network Providers, who provide network connectivity services 721 (e.g., network providers are responsible for carrying multicast 722 flows from head-ends to receivers). Refer to 723 [I-D.ietf-mboned-multiaaa-framework]. 725 Note that some contract agreements prevent a network provider from 726 altering the content as sent by the content provider for various 727 reasons. Under the contract, multicast streams should be delivered 728 unaltered to the requesting users. 730 Many current IPTV contents are likely to remain IPv4-formatted and 731 out of control of the network providers. Additionally, there are 732 numerous legacy receivers (e.g., IPv4-only Set Top Boxes (STB)) that 733 can't be upgraded or be easily replaced to support IPv6. As a 734 consequence, IPv4 service continuity MUST be guaranteed during the 735 transition period, including the delivery of multicast services such 736 as Live TV Broadcasting to users. 738 Appendix B. Deployment Considerations 740 B.1. Other operational Modes 741 B.1.1. MLD Querier with mAFTR Embedded 743 mAFTR can embed the MLD Querier function (as well as the PIMv6 DR) 744 for optimization. When mB4 sends MLD Report message to this mAFTR, 745 the mAFTR should process the MLD Report message that contain 746 IPv4-embedded IPv6 multicast group subscription information then send 747 the corresponding PIMv4 Join message. (Figure 4) 749 +---------+ 750 ---------| mAFTR |--------- 751 MLD |uPrefix64| PIMv4 752 |mPreifx64| 753 +---------+ 755 Figure 4: MLD-PIMv4 Interworking Function 757 Discussions about the location of the mAFTR capability and related 758 ASM or SSM multicast design considerations are out of the scope of 759 this document. 761 B.1.2. mAFTR embedded in DR 763 If mAFTR is the DR of the original IPv4 source, it may simply use the 764 uPrefix64 and mPrefix64 to build the IPv4-embedded IPv6 multicast 765 traffic, the sending of PIMv4 Join message is not necessary. 767 B.2. Older Version of Group Membership management Protocols 769 Given the multiple versions of group membership management protocols, 770 mismatch issues may be raised in the mB4 Function (refer to 771 Section 6.1). 773 If IGMPv2 operates on the IPv4 receivers while MLDv2 operates on the 774 MLD Querier, or if IGMPv3 operates on the IPv4 receivers while MLDv1 775 operates on the MLD Querier, the issue mentioned above will be 776 encountered. To solve this problem, the mB4 SHOULD perform the 777 router portion of IGMP which is of the same as the corresponding MLD 778 version (IGMPv2 as of MLDv1, or IGMPv3 as of MLDv2) operating in the 779 IPv6 domain, then the protocol interaction approach specified in 780 Section 7 of [RFC3376] can be used to exchange signaling messages 781 with the IPv4 receivers on which the different version of IGMP is 782 operating. 784 B.3. Load-Balancing 786 For robustness and load distribution purposes, several nodes in the 787 network can embed the mAFTR function. In such case, the same IPv6 788 prefixes (i.e., mPrefix64 and uPrefix64) and algorithm to build IPv4- 789 embedded IPv6 addresses MUST be configured on those nodes. 791 B.4. RP for IPv4-Embedded IPv6 Multicast Groups 793 For the sake of simplicity, it is RECOMMENDED to configure mAFTR as 794 the RP for the IPv4-embedded IPv6 multicast groups it manages. No 795 registration procedure is required under this configuration. 797 B.5. mAFTR Policy Configuration 799 mAFTR may be configured with a list of IPv4 multicast groups and 800 sources. Only multicast flows bound to the configured addresses 801 should be handled by the mAFTR. Otherwise, packets are silently 802 drooped. 804 B.6. Static vs. Dynamic PIM Triggering 806 To optimize the usage of network resources in current deployments, 807 all multicast streams are conveyed in the core network while only 808 popular ones are continuously conveyed in the aggregation/access 809 network (static mode). Non-popular streams are conveyed in the 810 access network upon request (dynamic mode). Depending on the 811 location of the mAFTR in the network, two modes can be envisaged: 812 static and dynamic. 814 o Static Mode: the mAFTR is configured to instantiate permanent (S6, 815 G6) and (*, G6) entries in its TIB6 using a pre-configured (S4, 816 G4) list. 818 o Dynamic Mode: the instantiation and deletion of (S6, g6) or (*, 819 G6) is triggered by the receipt of PIMv6 messages. 821 Authors' Addresses 823 Jacni Qin 824 Cisco 825 Shanghai 826 China 828 Email: jacni@jacni.com 829 Mohamed Boucadair 830 France Telecom 831 Rennes 35000 832 France 834 Email: mohamed.boucadair@orange.com 836 Christian Jacquenet 837 France Telecom 838 Rennes 35000 839 France 841 Email: christian.jacquenet@orange.com 843 Yiu L. Lee 844 Comcast 845 U.S.A. 847 Email: yiu_lee@cable.comcast.com 848 URI: http://www.comcast.com 850 Qian Wang 851 China Telecom 852 No.118, Xizhimennei 853 Beijing 100035 854 China 856 Phone: +86 10 5855 2177 857 Email: wangqian@ctbri.com.cn