idnits 2.17.1 draft-ietf-mboned-auto-multicast-03.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1.a on line 19. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 1021. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 1028. ** Found boilerplate matching RFC 3978, Section 5.4, paragraph 1 (on line 1040), which is fine, but *also* found old RFC 2026, Section 10.4C, paragraph 1 text on line 50. ** The document seems to lack an RFC 3978 Section 5.1 IPR Disclosure Acknowledgement -- however, there's a paragraph with a matching beginning. Boilerplate error? ** This document has an original RFC 3978 Section 5.4 Copyright Line, instead of the newer IETF Trust Copyright according to RFC 4748. ** The document seems to lack an RFC 3978 Section 5.5 (updated by RFC 4748) Disclaimer -- however, there's a paragraph with a matching beginning. Boilerplate error? ** The document seems to lack an RFC 3979 Section 5, para. 3 IPR Disclosure Invitation -- however, there's a paragraph with a matching beginning. Boilerplate error? ** The document uses RFC 3667 boilerplate or RFC 3978-like boilerplate instead of verbatim RFC 3978 boilerplate. After 6 May 2005, submission of drafts without verbatim RFC 3978 boilerplate is not accepted. The following non-3978 patterns matched text found in the document. That text should be removed or replaced: By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- ** The document is more than 15 pages and seems to lack a Table of Contents. == No 'Intended status' indicated for this document; assuming Proposed Standard Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** There is 1 instance of lines with control characters in the document. ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 96: '... The keywords MUST, MUST NOT, REQUIR...' RFC 2119 keyword, line 97: '... SHOULD NOT, RECOMMENDED, MAY, and O...' RFC 2119 keyword, line 549: '...n the AMT Membership Update. This MUST...' RFC 2119 keyword, line 655: '... local router, it SHOULD also function...' RFC 2119 keyword, line 659: '...ts. The gateway MUST also advertise i...' (8 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- Couldn't find a document date in the document -- date freshness check skipped. 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: 'RFC1112' is mentioned on line 87, but not defined == Missing Reference: 'RFC-2119' is mentioned on line 99, but not defined == Missing Reference: 'TBD IANA' is mentioned on line 237, but not defined == Unused Reference: 'IGMPv3' is defined on line 948, but no explicit reference was found in the text == Unused Reference: 'MLDv2' is defined on line 952, but no explicit reference was found in the text == Unused Reference: 'Brad88' is defined on line 961, but no explicit reference was found in the text ** Downref: Normative reference to an Informational RFC: RFC 2104 (ref. 'HMAC') == Outdated reference: A later version (-07) exists of draft-ietf-ssm-arch-06 -- Obsolete informational reference (is this intentional?): RFC 3068 (ref. 'ANYCAST') (Obsoleted by RFC 7526) -- Obsolete informational reference (is this intentional?): RFC 2362 (ref. 'PIMSM') (Obsoleted by RFC 4601, RFC 5059) Summary: 11 errors (**), 0 flaws (~~), 9 warnings (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Dave Thaler 3 Internet-Draft Mohit Talwar 4 October 2004 Amit Aggarwal 5 Expires: April 22, 2005 Microsoft 6 Lorenzo Vicisano 7 Cisco 8 Dirk Ooms 9 OneSparrow 11 Automatic IP Multicast Without Explicit Tunnels (AMT) 12 draft-ietf-mboned-auto-multicast-03.txt 14 Status of this Memo 16 By submitting this Internet-Draft, each author represents that any 17 applicable patent or other IPR claims of which he or she is aware 18 have been or will be disclosed, and any of which he or she becomes 19 aware will be disclosed, in accordance with Section 6 of RFC 3668. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html 37 Abstract 39 Automatic Multicast Tunneling (AMT) allows multicast communication 40 amongst isolated multicast-enabled sites or hosts, attached to a 41 network which has no native multicast support. It also enables them 42 to exchange multicast traffic with the native multicast 43 infrastructure (MBone) and does not require any manual configuration. 44 AMT uses an encapsulation interface so that no changes to a host 45 stack or applications are required, all protocols (not just UDP) are 46 handled, and there is no additional overhead in core routers. 48 Copyright Notice 50 Copyright (C) The Internet Society (2004). All Rights Reserved. 52 1. Introduction 54 The primary goal of this document is to foster the deployment of 55 native IP multicast by enabling a potentially large number of nodes 56 to connect to the already present multicast infrastructure. 57 Therefore, the techniques discussed here should be viewed as an 58 interim solution to help in the various stages of the transition to a 59 native multicast network. 61 To allow fast deployment, the solution presented here only requires 62 small and concentrated changes to the network infrastructure, and no 63 changes at all to user applications or to the socket API of end- 64 nodes' operating systems. The protocol introduced in this 65 specification is deployed in a few strategically-placed network nodes 66 and in user-installable software modules (pseudo device drivers 67 and/or user-mode daemons) that reside underneath the socket API of 68 end-nodes' operating systems. This mechanism is very similar to that 69 used by "6to4" [6TO4, ANYCAST] to get automatic IPv6 connectivity. 71 Effectively, AMT treats the unicast-only internetwork as a large non- 72 broadcast multi-access (NBMA) link layer, over which we require the 73 ability to multicast. To do this, multicast packets being sent to or 74 from a site must be encapsulated in unicast packets. If the group 75 has members in multiple sites, AMT encapsulation of the same 76 multicast packet will take place multiple times by necessity. 78 The following problems are addressed: 80 1. Allowing isolated sites/hosts to receive the SSM flavor of 81 multicast ([SSM]). 83 2. Allowing isolated sites/hosts to transmit the SSM flavor of 84 multicast. 86 3. Allowing isolated sites/hosts to receive general multicast (ISM 87 [RFC1112]). 89 This document does not address allowing isolated sites/hosts to 90 transmit general multicast. We expect that other solutions (e.g., 91 Tunnel Brokers, a la [BROKER]) will be used for sites that desire 92 this capability. 94 2. Requirements Terminology 96 The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 97 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this 98 document, are to be interpreted as described in [RFC-2119]. 100 3. Definitions 102 +---------------+ Internet +---------------+ 103 | AMT Site | | MBone | 104 | | AMT | | 105 | +------+----+ Relay +----+----+ AMT | 106 | |AMT Gateway| Anycast |AMT Relay| Subnet | 107 | | +-----+-+ Prefix +-+-----+ | Prefix | 108 | | |AMT IF | <--------|AMT IF | |--------> | 109 | | +-----+-+ +-+-----+ | | 110 | +------+----+ +----+----+ | 111 | | | | 112 +---------------+ +---------------+ 114 Figure 1: Automatic Multicast Definitions. 116 AMT Pseudo-Interface 117 AMT encapsulation of multicast packets inside unicast packets 118 occurs at a point that is logically equivalent to an interface, 119 with the link layer being the unicast-only network. This point is 120 referred to as a pseudo-interface. Some implementations may treat 121 it exactly like any other interface and others may treat it like a 122 tunnel end-point. 124 AMT Gateway 125 A host, or a site gateway router, supporting an AMT Pseudo- 126 Interface. It does not have native multicast connectivity to the 127 native multicast backbone infrastructure. It is simply referred 128 to in this document as a "gateway". 130 AMT Site 131 A multicast-enabled network not connected to the multicast 132 backbone served by an AMT Gateway. It could also be a stand- 133 alone AMT Gateway. 135 AMT Relay Router 136 A multicast router configured to support transit routing between 137 AMT Sites and the native multicast backbone infrastructure. The 138 relay router has one or more interfaces connected to the native 139 multicast infrastructure, zero or more interfaces connected to the 140 non-multicast capable internetwork, and an AMT pseudo-interface. 141 It is simply referred to in this document as a "relay". 143 As with [6TO4], we assume that normal multicast routers do not 144 want to be tunnel endpoints (especially if this results in high 145 fanout), and similarly that service providers do not want 146 encapsulation to arbitrary routers. Instead, we assume that 147 special-purpose routers will be deployed that are suitable for 148 serving as relays. 150 AMT Relay Anycast Prefix 151 A well-known address prefix used to advertise (into the unicast 152 routing infrastructure) a route to an available AMT Relay Router. 153 This could also be private (i.e., not well-known) for a private 154 relay. 156 Prefixes for both IPv4 and IPv6 will be assigned in a future 157 version of this draft. 159 AMT Relay Anycast Address 160 An anycast address which is used to reach the nearest AMT Relay 161 Router. 163 This address corresponds to the lowest address in the AMT Relay 164 Anycast Prefix. 166 AMT Unicast Autonomous System ID 167 A 16-bit Autonomous System ID, for use in BGP in accordance to 168 this memo. AS 10888 might be usable for this, but for now we'll 169 assume it's different, to avoid confusion. This number represents 170 a "pseudo-AS" common to all AMT relays using the well known AMT 171 Relay Anycast Prefix (private relays use their own ID). 173 To protect themselves from erroneous advertisements, managers of 174 border routers often use databases to check the relation between 175 the advertised network and the last hop in the AS path. 176 Associating a specific AS number with the AMT Relay Anycast 177 Address allows us to enter this relationship in the databases used 178 to check inter-domain routing [ANYCAST]. 180 AMT Subnet Prefix 181 A well-known address prefix used to advertise (into the M-RIB of 182 the native multicast-enabled infrastructure) a route to AMT Sites. 184 This prefix will be used to enable sourcing SSM traffic from an 185 AMT Gateway. 187 AMT Gateway Anycast Address 188 An anycast address in the AMT Subnet Prefix range, which is used 189 by an AMT Gateway to enable sourcing SSM traffic from local 190 applications. 192 AMT Multicast Autonomous System ID 193 A 16-bit Autonomous system ID, for use in MBGP in accordance to 194 this memo. This number represents a "pseudo-AS" common to all AMT 195 relays using the well known AMT Subnet Prefix (private relays use 196 their own ID). We assume that the existing AS 10888 is suitable 197 for this purpose. (Note: if this is a problem, a different one 198 would be fine.) 200 4. Overview 202 4.1. Receiving Multicast in an AMT Site 204 Internet 205 +---------------+ +---------------+ 206 | AMT Site | 2. 3-way Membership | MBone | 207 | | Handshake | | 208 | 1. Join +---+---+ =================> +---+---+ | 209 | +---->|Gateway| | Relay | | 210 | | +---+---+ <================= +---+---+ | 211 | R-+ | 3. Receive Data | | 212 +---------------+ +---------------+ 214 Figure 2: Receiving Multicast in an AMT Site. 216 AMT relays and gateways cooperate to transmit multicast traffic 217 sourced within the native multicast infrastructure to AMT sites: 218 relays receive the traffic natively and unicast-encapsulate it to 219 gateways; gateways decapsulate the traffic and possibly forward it 220 into the AMT site. 222 Each gateway has an AMT pseudo-interface that serves as a default 223 multicast route. Requests to join a multicast session are sent to 224 this interface and encapsulated to a particular relay reachable 225 across the unicast-only infrastructure. 227 Each relay has an AMT pseudo-interface too. Multicast traffic sent 228 on this interface is encapsulated to zero or more gateways that have 229 joined to the relay. The AMT recipient-list is determined for each 230 multicast session. This requires the relay to keep state for each 231 gateway which has joined a particular group or (source, group) pair). 232 Multicast packets from the native infrastructure behind the relay 233 will be sent to each gateway which has requested them. 235 All multicast packets (data and control) are encapsulated in unicast 236 packets. To work across NAT's, the encapsulation is done over UDP 237 using a reserved port number [TBD IANA]. 239 Each relay, plus the set of all gateways using the relay, together 240 are thought of as being on a separate logical NBMA link. This 241 implies that the AMT recipient- list is a list of "link layer" 242 addresses which are (IP address, UDP port) pairs. 244 Since the number of gateways using a relay can be quite large, and we 245 expect that most sites will not want to receive most groups, an 246 explicit-joining protocol is required for gateways to communicate 247 group membership information to a relay. The two most likely 248 candidates are the IGMP/MLD [IGMPv3/MLDv2] protocol, and the PIM- 249 Sparse Mode [PIMSM] protocol. Since an AMT gateway may be a host, 250 and hosts typically do not implement routing protocols, gateways will 251 use IGMP/MLD as described in Section 5 below. This allows a host 252 kernel (or a pseudo device driver) to easily implement AMT gateway 253 behavior, and obviates the relay from the need to know whether a 254 given gateway is a host or a router. From the relay's perspective, 255 all gateways are indistinguishable from hosts on an NBMA leaf 256 network. 258 4.1.1. Scalability Considerations 260 The requirement that a relay keep group state per gateway that has 261 joined the group introduces potential scalability concerns. 263 However, scalability of AMT can be achieved by adding more relays, 264 and using an appropriate relay discovery mechanism for gateways to 265 discover relays. The solution we adopt is to assign an anycast 266 address to relays. However, simply sending periodic membership 267 reports to the anycast address can cause duplicates. Specifically, 268 if routing changes such that a different relay receives a periodic 269 membership report, both the new and old relays will encapsulate data 270 to the AMT site until the old relay's state times out. This is 271 obviously undesirable. Instead, we use the anycast address merely to 272 find the unicast address of a relay to which membership reports are 273 sent. 275 Since adding another relay has the result of adding another 276 independent NBMA link, this allows the gateways to be spread out 277 among more relays so as to keep the number of gateways per relay at a 278 reasonable level. 280 4.1.2. Spoofing Considerations 282 An attacker could affect the group state in the relay or gateway by 283 spoofing the source address in the join or leave reports. This can be 284 used to launch reflection or denial of service attacks on the target. 285 Such attacks can be mitigated by using a three way handshake between 286 the gateway and the relay for each multicast membership report or 287 leave. 289 When a gateway or relay wants to send a membership report, it first 290 sends an AMT Request with a request nonce in it. The receiving side 291 (the respondent) can calculate a message authentication code (MAC) 292 based on the source IP address of the Request, the request nonce, and 293 a secret key known only to the respondent. 295 An AMT Membership Query is sent back including the request nonce and 296 the MAC to the originator of the Request. The originator then sends 297 the IGMP/MLD Membership/Listener Report or Leave/Done along with the 298 request nonce and the received MAC back to the respondent finalizing 299 the 3-way handshake. 301 Upon reception, the respondent can recalculate the MAC based on the 302 source IP address, the request nonce, and the local secret. The 303 IGMP/MLD message is only accepted if the received MAC matches the 304 calculated MAC. 306 The local secret never has to be shared with the other side. It is 307 only used to verify return routability of the originator. 309 4.2. Sourcing Multicast from an AMT site 311 Two cases are discussed below: multicast traffic sourced in an AMT 312 site and received in the MBone, and multicast traffic sourced in an 313 AMT site and received in another AMT site. 315 In both cases only SSM sources are supported. Furthermore this 316 specification only deals with the source residing directly in the 317 gateway. To enable a generic node in an AMT site to source 318 multicast, additional coordination between the gateway and the 319 source-node is required. 321 The general mechanism used to join towards AMT sources is based on 322 the following: 324 1. Applications residing in the gateway use addresses in the AMT 325 Subnet Prefix to send multicast, as a result of sourcing traffic 326 on the AMT pseudo-interface. 328 2. The AMT Subnet Prefix is advertised for RPF reachability in the M- 329 RIB by relays and gateways. 331 3. Relays or gateways that receive a join for a source/group pair use 332 information encoded in the address pair to rebuild the address of 333 the gateway (source) to which to encapsulate the join (see Section 334 5 for more details). The membership reports use the same three way 335 handshake as outlined in Section 4.1.2. 337 4.2.1. Supporting Site-MBone Multicast 339 Internet 340 +---------------+ +---------------+ 341 | AMT Site | 2. 3-way Membership | MBone | 342 | | Handshake | | 343 | +---+---+ <================= +---+---+ 1. Join | 344 | |Gateway| | Relay |<-----+ | 345 | +---+---+ =================> +---+---+ | | 346 | | 3. Receive Data | +-R | 347 +---------------+ +---------------+ 349 Figure 3: Site-MBone Multicast. 351 If a relay receives an explicit join from the native infrastructure, 352 for a given (source, group) pair where the source address belongs to 353 the AMT Subnet Prefix, then the relay will periodically (using the 354 rules specified in Section 4.1.2) encapsulate membership updates for 355 the group to the gateway. The gateway must keep state per relay from 356 which membership reports have been sent, and forward multicast 357 traffic from the site to all relays from which membership reports 358 have been received. The choice of whether this state and replication 359 is done at the link-layer (i.e., by the tunnel interface) or at the 360 network-layer is implementation dependent. 362 If there are multiple relays present, this ensures that data from the 363 AMT site is received via the closest relay to the receiver. This is 364 necessary when the routers in the native multicast infrastructure 365 employ Reverse-Path Forwarding (RPF) checks against the source 366 address, such as occurs when [PIMSM] is used by the multicast 367 infrastructure. 369 The solution above will scale to an arbitrary number of relays, as 370 long at the number of relays requiring multicast traffic from a given 371 AMT site remains reasonable enough to not overly burden the site's 372 gateway. 374 4.2.2. Supporting Site-Site Multicast 376 Internet 377 +---------------+ +---------------+ 378 | AMT Site | 2. 3-way Membership | AMT Site | 379 | | Handshake | | 380 | +---+---+ <================= +---+---+ 1. Join | 381 | |Gateway| |Gateway|<-----+ | 382 | +---+---+ =================> +---+---+ | | 383 | | 3. Receive Data | +-R | 384 +---------------+ +---------------+ 386 Figure 4: Site-Site Multicast. 388 Since we require gateways to accept membership reports, as described 389 above, it is also possible to support multicast among AMT sites, 390 without requiring assistance from any relays. 392 When a gateway wants to join a given (source, group) pair, where the 393 source address belongs to the AMT Subnet Prefix, then the gateway 394 will periodically unicast encapsulate an IGMPv3/MLDv2 [IGMPv3/MLDv2] 395 Report directly to the site gateway for the source. 397 We note that this can result in a significant amount of state at a 398 site gateway sourcing multicast to a large number of other AMT sites. 399 However, it is expected that this is not unreasonable for two 400 reasons. First, the gateway does not have native multicast 401 connectivity, and as a result is likely doing unicast replication at 402 present. The amount of state is thus the same as what such a site 403 already deals with. Secondly, any site expecting to source traffic to 404 a large number of sites could get a point-to-point tunnel to the 405 native multicast infrastructure, and use that instead of AMT. 407 5. Message Formats 409 5.1. AMT Relay Discovery 411 The AMT Relay Discovery message is a UDP packet sent from the AMT 412 gateway unicast address to the AMT relay anycast address to discover 413 the unicast address of an AMT relay. 415 The UDP source port is uniquely selected by the local host operating 416 system. The UDP destination port is the IANA reserved AMT port 417 number. 419 The payload of the UDP packet contains the following fields. 421 0 1 2 3 422 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 1 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 424 | Type=0x1 | Reserved | 425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 426 | Discovery Nonce | 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 429 Fields: 431 Type 432 The type of the message. 434 Reserved 435 A 24-bit reserved field. Sent as 0, ignored on receipt. 437 Discovery Nonce 438 A 32-bit random value generated by the gateway and replayed by the 439 relay. 441 5.2. AMT Relay Advertisement 443 The AMT Relay Advertisement message is a UDP packet sent from the AMT 444 relay anycast address to the source of the discovery message. 446 The UDP source port is the IANA reserved AMT port number and the UDP 447 destination port is the source port received in the Discovery 448 message. 450 The payload of the UDP packet contains the following fields. 452 Fields: 454 Type 455 The type of the message. 457 Reserved 458 A 24-bit reserved field. Sent as 0, ignored on receipt. 460 0 1 2 3 461 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 1 462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 463 | Type=0x2 | Reserved | 464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 465 | Discovery Nonce | 466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 467 | Relay Address | 468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 Discovery Nonce 471 A 32-bit random value replayed from the discovery message. 473 Relay Address 474 The unicast IPv4 or IPv6 address of the AMT relay. The family can 475 be determined by the length of the Advertisement. 477 5.3. AMT Request 479 A Request packet is sent to begin a 3-way handshake for sending an 480 IGMP/MLD Membership/Listener Report or Leave/Done. It can be sent 481 from a gateway to a relay, from a gateway to another gateway, or from 482 a relay to a gateway. 484 It is sent from the originator's unique unicast address to the 485 respondents' unique unicast address. 487 The UDP source port is uniquely selected by the local host operating 488 system. It can be different for each Request and different from the 489 source port used in Discovery messages but does not have to be. The 490 UDP destination port is the IANA reserved AMT port number. 492 0 1 2 3 493 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 1 494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 495 | Type=0x3 | Reserved | 496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 497 | Request Nonce | 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 500 Fields: 502 Type 503 The type of the message. 505 Reserved 506 A 24-bit reserved field. Sent as 0, ignored on receipt. 508 Request Nonce 509 A 32-bit identifier used to distinguish this request. 511 5.4. AMT Membership Query 513 An AMT Membership Query packet is sent from the relay back to the 514 originator to solicit an AMT Membership Update while confirming the 515 source of the original request. It contains a relay Message 516 Authentication Code (MAC) that is a non-cryptographic hash of a 517 private secret, the originators address, and the request nonce. 519 It is sent from the destination address received in the Request to 520 the source address received in the Request. 522 The UDP source port is the IANA reserved AMT port number and the UDP 523 destination port is the source port received in the Request message. 525 0 1 2 3 526 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 1 527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 | Type=0x4 | Reserved | 529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 530 | Request Nonce | 531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 532 | Response MAC | 533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 Fields: 537 Type 538 The type of the message. 540 Reserved 541 A 24-bit reserved field. Sent as 0, ignored on receipt. 543 Request Nonce 544 A 32-bit identifier used to distinguish this request echoed back 545 to the originator. 547 Response MAC 548 A 32-bit hash generated by the respondent and sent to the 549 originator for inclusion in the AMT Membership Update. This MUST 550 be calculated as HMAC-MD5-32 [HMAC]. 552 5.5. AMT Membership Update 554 An AMT Membership Update is sent from the originator to the 555 respondent containing the original IGMP/MLD Membership/Listener 556 Report or Leave/Done received over the AMT pseudo-interface. It 557 echoes the Response MAC received in the AMT Membership Query so the 558 respondent can verify return routability to the originator. 560 It is sent from the destination address received in the Query to the 561 source address received in the Query which should both be the same as 562 the original Request. 564 The UDP source and destination port numbers should be the same ones 565 sent in the original Request. 567 0 1 2 3 568 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 1 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 | Type=0x5 | Reserved | 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 | Request Nonce | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 | Response MAC | 575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 576 | IGMP/MLD Message | 577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 578 | ... | 579 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 Fields: 583 Type 584 The type of the message. 586 Reserved 587 A 24-bit reserved field. Sent as 0, ignored on receipt. 589 Request Nonce 590 A 32-bit identifier used to distinguish this request. 592 Response MAC 593 The MAC received from the relay and echoed back in the AMT 594 Membership Update. 596 5.6. AMT UDP Data 598 The AMT UDP Data message is a UDP packet encapsulating the data 599 requested by the originator based on a previous AMT Membership Update 600 message. Currently, it is only defined for original UDP multicast 601 data packets. This prevents the tunnel from being used as an 602 arbitrary tunnel mechanism and greatly reduces the possibility of 603 exploitation. 605 It is sent from the unicast destination address of the Membership 606 update to the source address of the Membership Update. 608 The UDP source and destination port numbers should be the same ones 609 sent in the original Query. 611 The payload of the UDP packet contains the following fields. 613 0 1 2 3 614 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 1 615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 | Type=0x6 | Reserved | 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 | UDP Multicast Data | 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 | ... | 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 Fields: 625 Type 626 The type of the message. 628 Reserved 629 A 24-bit reserved field. Sent as 0, ignored on receipt. 631 UDP Multicast Data 632 The original Multicast UDP data packet that is being replicated by 633 the relay to the gateways. 635 6. AMT Gateway Details 637 This section details the behavior of an AMT Gateway, which may be a 638 router serving an AMT site, or the site may consist of a single host, 639 serving as its own gateway. 641 6.1. At Startup Time 643 At startup time, the AMT gateway will bring up an AMT pseudo- 644 interface, to be used for encapsulation. The gateway will then send 645 a AMT Relay Discovery message to the AMT Relay Anycast Address, and 646 note the unicast address (which is treated as a link-layer address to 647 the encapsulation interface) from the AMT Relay Advertisement 648 message. This discovery should be done periodically (e.g., once a 649 day) to re-resolve the unicast address of a close relay. The gateway 650 also initializes a timer used to send periodic membership reports to 651 a random value from the interval [0, [Query Interval]] before sending 652 the first periodic report, in order to prevent startup 653 synchronization (e.g., after a power outage). 655 If the gateway is serving as a local router, it SHOULD also function 656 as an IGMP/MLD Proxy, as described in [PROXY], with its IGMP/MLD 657 host-mode interface being the AMT pseudo-interface. This enables it 658 to translate group memberships on its downstream interfaces into 659 IGMP/MLD Reports. The gateway MUST also advertise itself as the 660 default route for multicast in the M-RIB (or it must be the default 661 unicast router if unicast and multicast topologies are congruent). 662 Also, if a shared tree routing protocol is used inside the AMT site, 663 each tree-root must be a gateway, e.g., in PIM-SM each RP must be a 664 gateway. 666 Finally, to support sourcing traffic to SSM groups by a gateway with 667 a global unicast address, the AMT Subnet Prefix is treated as the 668 subnet prefix of the AMT pseudo-interface, and an anycast address is 669 added on the interface. This anycast address is formed by 670 concatenating the AMT Subnet Prefix followed by the high bits of the 671 gateway's global unicast address. For example, if IANA assigns the 672 IPv4 prefix x.y/16 as the AMT Subnet Prefix, and the gateway has 673 global unicast address a.b.c.d, then the AMT Gateway's Anycast 674 Address will be x.y.a.b. Note that multiple gateways might end up 675 with the same anycast address assigned to their pseudo-interfaces. 677 6.2. Joining Groups with MBone Sources 679 The IGMP/MLD protocol usually operates by having the Querier 680 multicast an IGMP/MLD Query message on the link. This behavior does 681 not work on NBMA links which do not support multicast. Since the set 682 of gateways is typically unknown to the relay (and potentially quite 683 large), unicasting the queries is also impractical. The following 684 behavior is used instead. 686 Applications residing in a gateway should join groups on the AMT 687 pseudo-interface, causing IGMP/MLD Membership/Listener Reports to be 688 sent over that interface. When UDP encapsulating the membership 689 reports (and in fact any other messages, unless specified otherwise 690 in this document), the destination address in the outer IP header is 691 the relay's unicast address. Robustness is provided by the 692 underlying IGMP/MLD protocol messages sent on the AMT pseudo- 693 interface. In other words, the gateway does not need to retransmit 694 IGMP/MLD Membership/Listener Reports and Leave/Done messages received 695 on the pseudo-interface since IGMP/MLD will already do this. The 696 gateway simply needs to encapsulate each IGMP/MLD Membership/Listener 697 Report and Leave/Done message it receives. 699 However, since periodic IGMP/MLD Membership/Listener Reports are sent 700 in response to IGMP/MLD Queries, some mechanism to trigger periodic 701 Membership/Listener Reports and Leave/Done messages are necessary. 702 This can be achieved in any implementation-specific manner. Some 703 possibilities include: 705 1. The AMT pseudo-interface might periodically manufacture 706 IGMPv3/MLDv2 Queries as if they had been received from an IGMP/MLD 707 Querier, and deliver them to the IP layer, after which normal 708 IGMP/MLD behavior will cause the appropriate reports to be sent. 710 2. The IGMP/MLD module itself might provide an option to operate in 711 periodic mode on specific interfaces. 713 6.3. Responding to Relay Changes 715 When a gateway determines that its current relay is unreachable 716 (e.g., upon receipt of a ICMP Unreachable message [ICMP] for the 717 relay's unicast address), it may need to repeat relay address 718 discovery. However, care should be taken not to abandon the current 719 relay too quickly due to transient network conditions. Some 720 implementations may find it difficult to send a discovery packet to 721 the anycast relay address while the gateway has an address configured 722 on the AMT pseudo-interface on the same anycast prefix. Therefore, it 723 may be necessary to tear down the AMT pseudo-interface to rediscover 724 a new relay. 726 6.4. Creating SSM groups 728 When a gateway wants to create an SSM group (i.e., in 232/8) for 729 which it can source traffic, the remaining 24 bits MUST be generated 730 as described below. ([SSM] states that "the policy for allocating 731 these bits is strictly locally determined at the sender's host.") 733 When the gateway determined its AMT Gateway Anycast Address as 734 described above, it used the high bits of its global unicast address. 735 The remaining bits of its global unicast address are appended to the 736 232/8 prefix, and any spare bits may be allocated using any policy 737 (again, strictly locally determined at the sender's host). 739 For example, if the IPv4 AMT Subnet Prefix is x.y/16, and the device 740 has global unicast address a.b.c.d, then it MUST allocate IPv4 SSM 741 groups in the range 232.c.d/24. 743 6.5. Joining SSM Groups with AMT Sources 745 An IGMPv3/MLDv2 Report for a given (source, group) pair MAY be 746 encapsulated directly to the source, when the source address belongs 747 to the AMT Subnet Prefix. 749 The "link-layer" address to use as the destination address in the 750 outer IP header is obtained as follows. The source address in the 751 inclusion list of the IGMPv3/MLDv2 report will be an AMT Gateway 752 Anycast Address with the high bits of the address, and the remaining 753 bits will be in the middle of the group address. 755 For example, if the IPv4 AMT Subnet Prefix is x.y/16, and the IGMPv3 756 Report is for (x.y.a.b, 232.c.d.e), then the "link layer" IPv4 757 destination address used for encapsulation is a.b.c.d. 759 6.6. Receiving IGMPv3/MLDv2 Reports at the Gateway 761 When an AMT Request is received by the gateway, it follows the same 762 3-way handshake procedure a relay would follow if it received the AMT 763 Request. It generates a MAC and responds with an AMT Membership 764 Query. When the AMT Membership Update is received, it verifies the 765 MAC and then processes the IGMP/MLD Membership/Listener Report or 766 Leave/Done. 768 At the gateway, the IGMP/MLD packet should be an IGMPv3/MLDv2 source 769 specific (S,G) join or leave. 771 If S is not the AMT Gateway Anycast Address, the packet is dropped. 772 If G does not contain the low bits of the global unicast address (as 773 described above), the packet is also dropped. 775 The gateway adds the source address (from the outer IP header) and 776 UDP port of the report to a membership list for G. Maintaining this 777 membership list may be done in any implementation-dependent manner. 778 For example, it might be maintained by the "link-layer" inside the 779 AMT pseudo-interface, making it invisible to the normal IGMP/MLD 780 module. 782 6.7. Sending data to SSM groups 784 When multicast packets are sent on the AMT pseudo-interface, they are 785 encapsulated as follows. If the group address is not an SSM group, 786 then the packet is dropped (this memo does not currently provide a 787 way to send to non-SSM groups). 789 If the group address is an SSM group, then the packet is unicast 790 encapsulated to each remote node from which the gateway has received 791 an IGMPv3/MLDv2 report for the packet's (source, group) pair. 793 7. Relay Router Details 795 7.1. At Startup time 797 At startup time, the relay router will bring up an NBMA-style AMT 798 pseudo-interface. It shall also add the AMT Relay Anycast Address on 799 some interface. 801 The relay router shall then advertise the AMT Relay Anycast Prefix 802 into the unicast-only Internet, as if it were a connection to an 803 external network. When the advertisement is done using BGP, the AS 804 path leading to the AMT Relay Anycast Prefix shall include the 805 identifier of the local AS and the AMT Unicast Autonomous System ID. 807 The relay router shall also enable IGMPv3/MLDv2 on the AMT pseudo- 808 interface, except that it shall not multicast Queries (this might be 809 done, for example, by having the AMT pseudo-device drop them, or by 810 having the IGMP/MLD module not send them in the first place). 812 Finally, to support sourcing SSM traffic from AMT sites, the AMT 813 Subnet Prefix is assigned to the AMT pseudo-interface, and the AMT 814 Subnet Prefix is injected into the M-RIB of MBGP. 816 7.2. Receiving Relay Discovery messages sent to the Anycast Address 818 When a relay receives a AMT Relay Discovery message directed to the 819 AMT Relay Anycast Address, it should respond with a AMT Relay 820 Advertisement containing its unicast address. The source and 821 destination addresses of the advertisement should be the same as the 822 destination and source addresses of the discovery message 823 respectively. Further, the nonce in the discovery message MUST be 824 copied into the advertisement message. 826 7.3. Receiving Membership Updates from AMT Gateways 828 The relay operates passively, sending no Queries but simply tracking 829 membership information according to Reports and Leave messages, as a 830 router normally would. In addition, the relay must also do explicit 831 membership tracking, as to which gateways on the AMT pseudo- 832 interface have joined which groups. Once an AMT Membership Update has 833 been successfully received, it updates the forwarding state for the 834 appropriate group and source (if provided). When data arrives for 835 that group, the traffic must be encapsulated to each gateway which 836 has joined that group. 838 The explicit membership tracking and unicast replication may be done 839 in any implementation-specific manner. Some examples are: 841 1. The AMT pseudo-device driver might track the group information and 842 perform the replication at the "link-layer", with no changes to a 843 pre-existing IGMP/MLD module. 845 2. The IGMP/MLD module might have native support for explicit 846 membership tracking, especially if it supports other NBMA-style 847 interfaces. 849 7.4. Receiving (S,G) Joins from the Native Side, for AMT Sources 851 The relay encapsulates an IGMPv3/MLDv2 report to the AMT source as 852 described above in Section 4.1.2. 854 8. IANA Considerations 856 The IANA should allocate a prefix dedicated to the public AMT Relays 857 to the native multicast backbone. The prefix length should be 858 determined by the IANA; the prefix should be large enough to 859 guarantee advertisement in the default- free BGP networks; a length 860 of 16 will meet this requirement. This is a one time effort; there 861 is no need for any recurring assignment after this stage. 863 The IANA should also allocate an Autonomous System ID which can be 864 used as a pseudo-AS when advertising routes to the above prefix. 865 Furthermore, to support sourcing SSM traffic from AMT gateways, the 866 IANA should allocate a subnet prefix dedicated to the AMT link. The 867 prefix length should be determined by the IANA; the prefix should be 868 large enough to guarantee advertisement in the default- free BGP 869 networks; a length of 16 will meet this requirement. This is a one 870 time effort; there is no need for any recurring assignment after this 871 stage. It should also be noted that this prefix length directly 872 affects the number of groups available to be created by the AMT 873 gateway: a length of 16 gives 256 groups, and a length of 8 gives 874 65536 groups. For diagnostic purposes, it is helpful to have a 875 prefix length which is a multiple of 8, although this is not 876 required. 878 An autonomous system number dedicated to a pseudo-AS for multicast is 879 already in use today (AS 10888), and so it is expected that no 880 additional AS number is required for this prefix. 882 Finally, IANA should allocate a reserved UDP port number for AMT 883 encapsulation. 885 9. Security Considerations 887 The anycast technique introduces a risk that a rogue router or a 888 rogue AS could introduce a bogus route to the AMT Relay Anycast 889 Prefix, and thus divert the traffic. Network managers have to 890 guarantee the integrity of their routing to the AMT Relay anycast 891 prefix in much the same way that they guarantee the integrity of all 892 other routes. 894 Within the native MBGP infrastructure, there is a risk that a rogue 895 router or a rogue AS could introduce a bogus route to the AMT Subnet 896 Prefix, and thus divert joins and cause RPF failures of multicast 897 traffic. Again, network managers have to guarantee the integrity of 898 the MBGP routing to the AMT subnet prefix in much the same way that 899 they guarantee the integrity of all other routes in the M-RIB. 901 Gateways and relays will accept and decapsulate multicast traffic 902 from any source from which regular unicast traffic is accepted. If 903 this is for any reason felt to be a security risk, then additional 904 source address based packet filtering MUST be applied: 906 1. To prevent a rogue sender (that can't do traditional spoofing 907 because of e.g. access lists deployed by its ISP) from making use 908 of AMT to send packets to an SSM tree, a relay that receives an 909 encapsulated multicast packet MUST discard the multicast packet if 910 the IPv4 source address in the outer header is not composed of the 911 last 2 bytes of the source address and the 2 middle bytes of the 912 destination address of the inner header (i.e., a.b.c.d must be 913 composed of the a.b of x.y.a.b and the c.d of 232.c.d.e). 915 2. A gateway MUST discard encapsulated multicast packets if the 916 source address in the outer header is not the address to which the 917 encapsulated join message was sent. An AMT Gateway that receives 918 an encapsulated IGMPv3/MLDv2 (S,G)-Join MUST discard the message 919 if the IPv4 destination address in the outer header is not 920 composed of the last 2 bytes of S and the 2 middle bytes of G 921 (i.e. the destination address a.b.c.d must be composed of the a.b 922 of the multicast source x.y.a.b and the c.d of the multicast group 923 232.c.d.e). 925 10. Acknowledgments 927 Most of the mechanisms described in this document are based on 928 similar work done by the NGTrans WG for obtaining automatic IPv6 929 connectivity without explicit tunnels ("6to4"). Tony Ballardie 930 provided helpful discussion that inspired this document. Tom 931 Pusateri helped flush out protocol details based on implementation 932 experience and provided updates to this draft. 934 11. Normative References 936 [HMAC] Krawczyk, H., Bellare, M., Canetti, R., "HMAC: Keyed- 937 Hashing for Message Authentication", RFC 2104, February 938 1997. 940 [ICMP] Postel, J., "Internet Control Message Protocol", RFC 792, 941 September 1981. 943 [PROXY] Fenner, W., He, H., Haberman, B., Sandick, H., "IGMP/MLD- 944 based Multicast Forwarding ("IGMP/MLD Proxying")", Work 945 in progress, draft-ietf-magma-igmp-proxy-06.txt, April 946 2004. 948 [IGMPv3] Cain, B., Deering, S., Fenner, B., Kouvelas, I., 949 Thyagarajan A., "Internet Group Management Protocol, 950 Version 3", RFC 3376, October 2002. 952 [MLDv2] Vida, R., Costa, L., "Multicast Listener Discovery 953 Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. 955 [SSM] Holbrook, H., Cain, B., "Source-Specific Multicast for 956 IP", Work in Progress, draft-ietf-ssm-arch-06.txt, 957 September 2004. 959 12. Informative References 961 [Brad88] Braden, R., Borman, D., Partridge, C., "Computing the 962 Internet Checksum", RFC 1071, September 1988. 964 [6TO4] Carpenter, B., Moore, K., "Connection of IPv6 Domains via 965 IPv4 Clouds", RFC 3056, February 2001. 967 [BROKER] Durand, A., Fasano, P., Guardini, I., Lento, D., "IPv6 968 Tunnel Broker", RFC 3053, January 2001. 970 [ANYCAST] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers", 971 RFC 3068, June 2001. 973 [PIMSM] Estrin, D. Farinacci, D., Helmy, A., Thaler, D., Deering, 974 S., Handley, M., Jacobson, V., Liu, C., Sharma, P., Wei, 975 L., "Protocol Independent Multicast-Sparse Mode (PIM-SM): 976 Protocol Specification", RFC 2362, June 1998. 978 13. Author's Address 980 Dave Thaler 981 Microsoft Corporation 982 One Microsoft Way 983 Redmond, WA 98052-6399 984 Phone: +1 425 703 8835 985 EMail: dthaler@microsoft.com 987 Mohit Talwar 988 Microsoft Corporation 989 One Microsoft Way 990 Redmond, WA 98052-6399 991 Phone: +1 425 705 3131 992 EMail: mohitt@microsoft.com 994 Amit Aggarwal 995 Microsoft Corporation 996 One Microsoft Way 997 Redmond, WA 98052-6399 998 Phone: +1 425 706 0593 999 EMail: amitag@microsoft.com 1000 Lorenzo Vicisano 1001 Cisco Systems 1002 170 West Tasman Dr. 1003 San Jose, CA 95134 1004 Phone: +1 408 525 2530 1005 EMail: lorenzo@cisco.com 1007 Dirk Ooms 1008 OneSparrow 1009 Belegstraat 13; 2018 Antwerp; Belgium 1010 EMail: dirk@onesparrow.com 1012 14. Intellectual Property Rights Notice 1014 The IETF takes no position regarding the validity or scope of any 1015 Intellectual Property Rights or other rights that might be claimed to 1016 pertain to the implementation or use of the technology described in 1017 this document or the extent to which any license under such rights 1018 might or might not be available; nor does it represent that it has 1019 made any independent effort to identify any such rights. Information 1020 on the procedures with respect to rights in RFC documents can be 1021 found in BCP 78 and BCP 79. 1023 Copies of IPR disclosures made to the IETF Secretariat and any 1024 assurances of licenses to be made available, or the result of an 1025 attempt made to obtain a general license or permission for the use of 1026 such proprietary rights by implementers or users of this 1027 specification can be obtained from the IETF on-line IPR repository at 1028 http://www.ietf.org/ipr. 1030 The IETF invites any interested party to bring to its attention any 1031 copyrights, patents or patent applications, or other proprietary 1032 rights that may cover technology that may be required to implement 1033 this standard. Please address the information to the IETF at ietf- 1034 ipr@ietf.org." 1036 15. Full Copyright Statement 1038 Copyright (C) The Internet Society (2004). This document is subject 1039 to the rights, licenses and restrictions contained in BCP 78, and 1040 except as set forth therein, the authors retain all their rights. 1042 16. Disclaimer 1044 This document and the information contained herein are provided on an 1045 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1046 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 1047 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 1048 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 1049 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1050 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." 1051 Table of Contents 1053 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1054 2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 3 1055 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 1056 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1057 4.1. Receiving Multicast in an AMT Site . . . . . . . . . . . . . 5 1058 4.2. Sourcing Multicast from an AMT site . . . . . . . . . . . . 7 1059 5. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 9 1060 5.1. AMT Relay Discovery . . . . . . . . . . . . . . . . . . . . 9 1061 5.2. AMT Relay Advertisement . . . . . . . . . . . . . . . . . . 10 1062 5.3. AMT Request . . . . . . . . . . . . . . . . . . . . . . . . 11 1063 5.4. AMT Membership Query . . . . . . . . . . . . . . . . . . . . 12 1064 5.5. AMT Membership Update . . . . . . . . . . . . . . . . . . . 13 1065 5.6. AMT UDP Data . . . . . . . . . . . . . . . . . . . . . . . . 14 1066 6. AMT Gateway Details . . . . . . . . . . . . . . . . . . . . . 14 1067 6.1. At Startup Time . . . . . . . . . . . . . . . . . . . . . . 15 1068 6.2. Joining Groups with MBone Sources . . . . . . . . . . . . . 15 1069 6.3. Responding to Relay Changes . . . . . . . . . . . . . . . . 16 1070 6.4. Creating SSM groups . . . . . . . . . . . . . . . . . . . . 16 1071 6.5. Joining SSM Groups with AMT Sources . . . . . . . . . . . . 17 1072 6.6. Receiving IGMPv3/MLDv2 Reports at the Gateway . . . . . . . 17 1073 6.7. Sending data to SSM groups . . . . . . . . . . . . . . . . . 18 1074 7. Relay Router Details . . . . . . . . . . . . . . . . . . . . . 18 1075 7.1. At Startup time . . . . . . . . . . . . . . . . . . . . . . 18 1076 7.2. Receiving Relay Discovery messages sent to the Anycast 1077 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1078 7.3. Receiving Membership Updates from AMT Gateways . . . . . . . 19 1079 7.4. Receiving (S,G) Joins from the Native Side, for AMT Sources 1080 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1081 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 1082 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 1083 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 1084 11. Normative References . . . . . . . . . . . . . . . . . . . . 21 1085 12. Informative References . . . . . . . . . . . . . . . . . . . 22 1086 13. Author's Address . . . . . . . . . . . . . . . . . . . . . . 22 1087 14. Intellectual Property Rights Notice . . . . . . . . . . . . . 23 1088 15. Full Copyright Statement . . . . . . . . . . . . . . . . . . 23 1089 16. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 24