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Please replace those with straight textual mentions of the documents in question. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year == Line 754 has weird spacing: '...ces and group...' == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: RPs which originate SA messages do so periodically as long as there is data being sent by the source. There is one SA-Advertisement-Timer covering the sources that an RP may advertise. [SA-Advertisement-Period] MUST be 60 seconds. An RP MUST not send more than one periodic SA message for a given (S,G) within an SA Advertisement interval. Originating periodic SA messages is required to keep announcements alive in caches. Finally, an originating RP SHOULD trigger the transmission of an SA message as soon as it receives data from an internal source for the first time. This initial SA message may be in addition to the periodic sa-message forwarded in that first 60 seconds for that (S,G). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: If an MSDP message is received with a TLV format error, the session SHOULD be reset with that peer. MSDP messages with other errors, such as unrecognized type code, received from MSDP peers, SHOULD be silently discarded and the session SHOULD not be reset. -- 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.) -- The document date (May 2003) is 6945 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) == Missing Reference: 'SG-State-Period' is mentioned on line 244, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 245, but not defined == Missing Reference: 'HoldTime-Period' is mentioned on line 513, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 658, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 485, but not defined -- Looks like a reference, but probably isn't: '8' on line 763 -- Looks like a reference, but probably isn't: '200' on line 763 -- Looks like a reference, but probably isn't: '201' on line 768 -- Looks like a reference, but probably isn't: '255' on line 768 == Unused Reference: 'RFC2119' is defined on line 801, but no explicit reference was found in the text ** Obsolete normative reference: RFC 1142 (Obsoleted by RFC 7142) ** Obsolete normative reference: RFC 2178 (Obsoleted by RFC 2328) ** Obsolete normative reference: RFC 2283 (Obsoleted by RFC 2858) ** Obsolete normative reference: RFC 2362 (Obsoleted by RFC 4601, RFC 5059) ** Obsolete normative reference: RFC 2385 (Obsoleted by RFC 5925) ** Downref: Normative reference to an Informational RFC: RFC 3446 Summary: 9 errors (**), 0 flaws (~~), 12 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT Bill Fenner (Editor) 2 draft-ietf-msdp-spec-17.txt David Meyer (Editor) 3 Category Informational 4 Expires: November 2003 May 2003 6 Multicast Source Discovery Protocol (MSDP) 7 9 Status of this Document 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 This document is a product of an individual. Comments are solicited 31 and should be addressed to the author(s). 33 Copyright Notice 35 Copyright (C) The Internet Society (2003). All Rights Reserved. 37 Abstract 39 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 40 to connect multiple IP Version 4 Protocol Independent Multicast 41 Sparse-Mode (PIM-SM) [RFC2362] domains together. Each PIM-SM domain 42 uses its own independent Rendezvous Point (RP) and does not have to 43 depend on RPs in other domains. This document reflects existing MSDP 44 implementations. 46 Table of Contents 48 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 49 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 50 3. Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . 5 51 4. Caching. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 52 5. Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 53 5.1. SA-Advertisement-Timer. . . . . . . . . . . . . . . . . . . 7 54 5.2. SA-Advertisement-Timer Processing . . . . . . . . . . . . . 8 55 5.3. SA Cache Timeout (SA-State Timer) . . . . . . . . . . . . . 8 56 5.4. Peer Hold Timer . . . . . . . . . . . . . . . . . . . . . . 8 57 5.5. KeepAlive Timer . . . . . . . . . . . . . . . . . . . . . . 9 58 5.6. ConnectRetry Timer. . . . . . . . . . . . . . . . . . . . . 9 59 6. Intermediate MSDP Peers. . . . . . . . . . . . . . . . . . . . 9 60 7. SA Filtering and Policy. . . . . . . . . . . . . . . . . . . . 10 61 8. Encapsulated Data Packets. . . . . . . . . . . . . . . . . . . 10 62 9. Other Scenarios. . . . . . . . . . . . . . . . . . . . . . . . 10 63 10. MSDP Peer-RPF Forwarding. . . . . . . . . . . . . . . . . . . 11 64 10.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . . 11 65 10.1.1. Multicast RPF Routing Information Base. . . . . . . . . 11 66 10.1.2. Peer-RPF Route. . . . . . . . . . . . . . . . . . . . . 11 67 10.1.3. Peer-RPF Forwarding Rules . . . . . . . . . . . . . . . 11 68 10.2. MSDP mesh-group semantics. . . . . . . . . . . . . . . . . 13 69 11. MSDP Connection State Machine . . . . . . . . . . . . . . . . 14 70 11.1. Events . . . . . . . . . . . . . . . . . . . . . . . . . . 15 71 11.2. Actions. . . . . . . . . . . . . . . . . . . . . . . . . . 16 72 11.3. Peer-specific Events . . . . . . . . . . . . . . . . . . . 16 73 11.4. Peer-independent Events. . . . . . . . . . . . . . . . . . 17 74 12. Packet Formats. . . . . . . . . . . . . . . . . . . . . . . . 17 75 12.1. MSDP TLV format. . . . . . . . . . . . . . . . . . . . . . 17 76 12.2. Defined TLVs . . . . . . . . . . . . . . . . . . . . . . . 18 77 12.2.1. IPv4 Source-Active TLV. . . . . . . . . . . . . . . . . 18 78 12.2.2. KeepAlive TLV . . . . . . . . . . . . . . . . . . . . . 20 79 13. MSDP Error Handling . . . . . . . . . . . . . . . . . . . . . 20 80 14. SA Data Encapsulation . . . . . . . . . . . . . . . . . . . . 21 81 15. Applicability Statement . . . . . . . . . . . . . . . . . . . 21 82 15.1. Between PIM Domains. . . . . . . . . . . . . . . . . . . . 21 83 15.2. Between Anycast-RPs. . . . . . . . . . . . . . . . . . . . 21 84 16. Intellectual Property . . . . . . . . . . . . . . . . . . . . 21 85 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 86 18. Security Considerations . . . . . . . . . . . . . . . . . . . 23 87 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 88 19.1. IANA Allocated TLV Range . . . . . . . . . . . . . . . . . 23 89 19.2. Experimental TLV Range . . . . . . . . . . . . . . . . . . 23 90 20. References. . . . . . . . . . . . . . . . . . . . . . . . . . 24 91 20.1. Normative References . . . . . . . . . . . . . . . . . . . 24 92 20.2. Informative References . . . . . . . . . . . . . . . . . . 24 94 21. Editor's Addresses. . . . . . . . . . . . . . . . . . . . . . 25 95 22. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 25 97 1. Introduction 99 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 100 to connect multiple PIM Sparse-Mode (PIM-SM) [RFC2362] domains 101 together. Each PIM-SM domain uses its own independent RP(s) and does 102 not have to depend on RPs in other domains. Advantages of this 103 approach include: 105 o No Third-party resource dependencies on a domain's RP 107 PIM-SM domains can rely on their own RPs only. 109 o Receiver only Domains 111 Domains with only receivers get data without globally 112 advertising group membership. 114 Note that MSDP may be used with protocols other than PIM-SM, but such 115 usage is not specified in this memo. 117 2. Overview 119 MSDP-speaking routers in a PIM-SM domain have a MSDP peering 120 relationship with MSDP peers in another domain. The peering 121 relationship is made up of a TCP connection in which control 122 information is exchanged. Each domain has one or more connections to 123 this virtual topology. 125 The purpose of this topology is to allow domains to discover 126 multicast sources from other domains. If the multicast sources are of 127 interest to a domain which has receivers, the normal source-tree 128 building mechanism in PIM-SM will be used to deliver multicast data 129 over an inter-domain distribution tree. 131 3. Procedure 133 When an RP in a PIM-SM domain first learns of a new sender, e.g. via 134 PIM register messages, it constructs a "Source-Active" (SA) message 135 and sends it to its MSDP peers. All RPs, which intend to originate or 136 receive SA messages, must establish MSDP peering with other RPs, 137 either directly or via an intermediate MSDP peer. The SA message 138 contains the following fields: 140 o Source address of the data source. 142 o Group address the data source sends to. 144 o IP address of the RP. 146 Note that an RP that isn't a DR on a shared network SHOULD NOT 147 originate SA's for directly connected sources on that shared network; 148 it should only originate in response to receiving Register messages 149 from the DR. 151 Each MSDP peer receives and forwards the message away from the RP 152 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 153 flooding is with respect to forwarding SA messages. The Multicast RPF 154 Routing Information Base (MRIB) is examined to determine which peer 155 towards the originating RP of the SA message is selected. Such a peer 156 is called an "RPF peer". See section 13 for the details of peer-RPF 157 forwarding. 159 If the MSDP peer receives the SA from a non-RPF peer towards the 160 originating RP, it will drop the message. Otherwise, it forwards the 161 message to all its MSDP peers (except the one from which it received 162 the SA message). 164 When an MSDP peer which is also an RP for its own domain receives a 165 new SA message, it determines if there are any group members within 166 the domain interested in any group described by an (Source, Group), 167 or (S,G) entry within the SA message. That is, the RP checks for a 168 (*,G) entry with a non-empty outgoing interface list; this implies 169 that some system in the domain is interested in the group. In this 170 case, the RP triggers a (S,G) join event towards the data source as 171 if a Join/Prune message was received addressed to the RP itself. This 172 sets up a branch of the source-tree to this domain. Subsequent data 173 packets arrive at the RP via this tree branch, and are forwarded down 174 the shared-tree inside the domain. If leaf routers choose to join the 175 source-tree they have the option to do so according to existing PIM- 176 SM conventions. Finally, if an RP in a domain receives a PIM Join 177 message for a new group G, the RP SHOULD trigger a (S,G) join event 178 for each active (S,G) for that group in its SA cache. 180 This procedure has been affectionately named flood-and-join because 181 if any RP is not interested in the group, they can ignore the SA 182 message. Otherwise, they join a distribution tree. 184 4. Caching 186 A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP 187 messages as well as reducing join latency for new receivers of a 188 group G at an originating RP which has existing MSDP (S,G) state. In 189 addition, caching greatly aids in diagnosis and debugging of various 190 problems. 192 An MSDP speaker must provide a mechanism to reduce the forwarding of 193 new SA's. The SA-cache is used to reduce storms and performs this by 194 not forwarding SA's unless they are in the cache or are new SA 195 packets that the MSDP speaker will cache for the first time. The SA- 196 cache also reduces storms by advertising from the cache at a period 197 of no more than twice per SA-Advertisement-Timer interval and not 198 less than 1 time per SA Advertisement period. 200 5. Timers 202 The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry 203 timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer. Each 204 is considered below. 206 5.1. SA-Advertisement-Timer 208 RPs which originate SA messages do so periodically as long as there 209 is data being sent by the source. There is one SA-Advertisement-Timer 210 covering the sources that an RP may advertise. [SA-Advertisement- 211 Period] MUST be 60 seconds. An RP MUST not send more than one 212 periodic SA message for a given (S,G) within an SA Advertisement 213 interval. Originating periodic SA messages is required to keep 214 announcements alive in caches. Finally, an originating RP SHOULD 215 trigger the transmission of an SA message as soon as it receives data 216 from an internal source for the first time. This initial SA message 217 may be in addition to the periodic sa-message forwarded in that first 218 60 seconds for that (S,G). 220 5.2. SA-Advertisement-Timer Processing 222 An RP MUST spread the generation of periodic SA messages (i.e. 223 messages advertising the active sources for which it is the RP) over 224 its reporting interval (i.e. SA-Advertisement-Period). An RP starts 225 the SA-Advertisement-Timer when the MSDP process is configured. When 226 the timer expires, an RP resets the timer to [SA-Advertisement- 227 Period] seconds, and begins the advertisement of its active sources. 228 Active sources are advertised in the following manner: An RP packs 229 its active sources into an SA message until the largest MSDP packet 230 that can be sent is built or there are no more sources, and then 231 sends the message. This process is repeated periodically within the 232 SA-Advertisement-Period in such a way that all of the RP's sources 233 are advertised. Note that since MSDP is a periodic protocol, an 234 implementation SHOULD send all cached SA messages when a connection 235 is established. Finally, the timer is deleted when the MSDP process 236 is de-configured. 238 5.3. SA Cache Timeout (SA-State Timer) 240 Each entry in an SA Cache has an associated SA-State Timer. A 241 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 242 received by an MSDP peer. The timer is reset to [SG-State-Period] if 243 another (S,G)-SA message is received before the (S,G)-SA-State Timer 244 expires. [SG-State-Period] MUST NOT be less than [SA-Advertisement- 245 Period] + [SA-Hold-Down-Period]. 247 5.4. Peer Hold Timer 249 The Hold Timer is initialized to [HoldTime-Period] when the peer's 250 transport connection is established, and is reset to [HoldTime- 251 Period] when any MSDP message is received. Finally, the timer is 252 deleted when the peer's transport connection is closed. [HoldTime- 253 Period] MUST be at least three seconds. The recommended value for 254 [HoldTime-Period] is 75 seconds. 256 5.5. KeepAlive Timer 258 Once an MSDP transport connection is established, each side of the 259 connection sends a KeepAlive message and sets a KeepAlive timer. If 260 the KeepAlive timer expires, the local system sends a KeepAlive 261 message and restarts its KeepAlive timer. 263 The KeepAlive timer is set to [KeepAlive-Period] when the peer comes 264 up. The timer is reset to [KeepAlive-Period] each time an MSDP 265 message is sent to the peer, and reset when the timer expires. 267 Finally, the KeepAlive timer is deleted when the peer's transport 268 connection is closed. 270 [KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be 271 at least one second. The recommended value for [KeepAlive-Period] is 272 60 seconds. 274 5.6. ConnectRetry Timer 276 The ConnectRetry timer is used by the MSDP peer with the lower IP 277 address to transition from INACTIVE to CONNECTING states. There is 278 one timer per peer, and the [ConnectRetry-Period] SHOULD be set to 30 279 seconds. The timer is initialized to [ConnectRetry-Period] when an 280 MSDP speaker attempts to actively open a TCP connection to its peer 281 (see section 15, event E2, action A2 ). When the timer expires, the 282 peer retries the connection and the timer is reset to [ConnectRetry- 283 Period]. It is deleted if either the connection transitions into 284 ESTABLISHED state or the peer is de-configured. 286 6. Intermediate MSDP Peers 288 Intermediate MSDP speakers do not originate periodic SA messages on 289 behalf of sources in other domains. In general, an RP MUST only 290 originate an SA for a source which would register to it, and ONLY RPs 291 may originate SA messages. 293 7. SA Filtering and Policy 295 As the number of (S,G) pairs increases in the Internet, an RP may 296 want to filter which sources it describes in SA messages. Also, 297 filtering may be used as a matter of policy which at the same time 298 can reduce state. MSDP peers in transit domains should not filter SA 299 messages or the flood-and-join model can not guarantee that sources 300 will be known throughout the Internet (i.e., SA filtering by transit 301 domains may cause undesired lack of connectivity). In general, policy 302 should be expressed using MBGP [RFC2283]. This will cause MSDP 303 messages to flow in the desired direction and peer-RPF fail 304 otherwise. An exception occurs at an administrative scope [RFC2365] 305 boundary. In particular, a SA message for a (S,G) MUST NOT be sent to 306 peers which are on the other side of an administrative scope boundary 307 for G. 309 8. Encapsulated Data Packets 311 The RP MAY encapsulate multicast data from the source. An interested 312 RP may decapsulate the packet, which SHOULD be forwarded as if a PIM 313 register encapsulated packet was received. That is, if packets are 314 already arriving over the interface toward the source, then the 315 packet is dropped. Otherwise, if the outgoing interface list is non- 316 null, the packet is forwarded appropriately. Note that when doing 317 data encapsulation, an implementation MUST bound the time during 318 which packets are encapsulated. 320 This allows for small bursts to be received before the multicast tree 321 is built back toward the source's domain. For example, an 322 implementation SHOULD encapsulate at least the first packet to 323 provide service to bursty sources. 325 9. Other Scenarios 327 MSDP is not limited to deployment across different routing domains. 328 It can be used within a routing domain when it is desired to deploy 329 multiple RPs for the same group ranges such as with Anycast RP's. As 330 long as all RPs have a interconnected MSDP topology, each can learn 331 about active sources as well as RPs in other domains. 333 10. MSDP Peer-RPF Forwarding 335 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 336 messages throughout an MSDP enabled internet. Unlike the RPF check 337 used when forwarding data packets, which generally compares the 338 packet's source address against the interface upon which the packet 339 was received, the Peer-RPF check compares the RP address carried in 340 the SA message against the MSDP peer from which the message was 341 received. 343 10.1. Definitions 345 The following definitions are used in the description of the Peer-RPF 346 Forwarding Rules: 348 10.1.1. Multicast RPF Routing Information Base 350 The Multicast RPF Routing Information Base (MRIB) is the multicast 351 topology table. It is typically derived from the unicast routing 352 table or from other routing protocols such as multi-protocol BGP 353 [RFC2283]. 355 10.1.2. Peer-RPF Route 357 The Peer-RPF route is the route that the MRIB chooses for a given 358 address. The Peer-RPF route for a SA's originating RP is used to 359 select the peer from which the SA is accepted. 361 10.1.3. Peer-RPF Forwarding Rules 363 An SA message originated by R and received by X from N is accepted if 364 N is the peer-RPF neighbor for X, and is discarded otherwise. 366 MPP(R,N) MP(N,X) 367 R ---------....-------> N ------------------> X 368 SA(S,G,R) SA(S,G,R) 370 MP(N,X) is an MSDP peering between N and X. MPP(R,N) is an MSDP 371 peering path (zero or more MSDP peers) between R and N, e.g. MPP(R,N) 372 = MP(R, A) + MP(A, B) + MP(B, N). SA(S,G,R) is an SA message for 373 source S on group G originated by an RP R. 375 The peer-RPF neighbor N is chosen deterministically, using the first 376 of the following rules that matches. In particular, N is the RPF 377 neighbor of X with respect to R if 378 (i). N == R (X has an MSDP peering with R). 380 (ii). N is the eBGP NEXT_HOP of the Peer-RPF route for R. 382 (iii). The Peer-RPF route for R is learned through a 383 distance-vector or path-vector routing protocol 384 (e.g. BGP, RIP, DVMRP) and N is the neighbor that 385 advertised the Peer-RPF route for R (e.g. N is the iBGP 386 advertiser of the route for R), or N is the IGP next hop 387 for R if the route for R is learned via a link-state 388 protocol (e.g. OSPF [RFC2178] or IS-IS [RFC1142]). 390 (iv). N resides in the closest AS in the best path towards 391 R. If multiple MSDP peers reside in the closest AS, the 392 peer with the highest IP address is the rpf-peer. 394 (v). N is configured as the static RPF-peer for R. 396 MSDP peers, which are NOT in state ESTABLISHED (i.e., down peers), 397 are not eligible for peer RPF consideration. 399 10.2. MSDP mesh-group semantics 401 An MSDP mesh-group is a operational mechanism for reducing SA 402 flooding, typically in an intra-domain setting. In particular, when 403 some subset of a domain's MSDP speakers are fully meshed, they can be 404 configured into a mesh-group. 406 Note that mesh-groups assume that a member doesn't have to forward an 407 SA to other members of the mesh-group because the originator will 408 forward to all members. To be able for the originator to forward to 409 all members (and to have each member also be a potential originator), 410 the mesh-group must be a full mesh of MSDP peering among all members. 412 The semantics of the mesh-group are as follows: 414 (i). If a member R of a mesh-group M receives a SA message 415 from an MSDP peer that is also a member of mesh-group M, 416 R accepts the SA message and forwards it to all of its 417 peers that are not part of mesh-group M. R MUST NOT 418 forward the SA message to other members of mesh-group M. 420 (ii). If a member R of a mesh-group M receives an SA message 421 from an MSDP peer that is not a member of mesh-group M, 422 and the SA message passes the peer-RPF check, then R 423 forwards the SA message to all members of mesh-group M 424 and to any other msdp peers. 426 11. MSDP Connection State Machine 428 MSDP uses TCP as its transport protocol. In a peering relationship, 429 one MSDP peer listens for new TCP connections on the well-known port 430 639. The other side makes an active connect to this port. The peer 431 with the higher IP address will listen. This connection establishment 432 algorithm avoids call collision. Therefore, there is no need for a 433 call collision procedure. It should be noted, however, that the 434 disadvantage of this approach is that the startup time depends 435 completely upon the active side and its connect retry timer; the 436 passive side cannot cause the connection to be established. 438 An MSDP peer starts in the DISABLED state. MSDP peers establish 439 peering sessions according to the following state machine: 441 --------------->+----------+ 442 / | DISABLED |<---------- 443 | ------>+----------+ \ 444 | / |E1->A1 | 445 | | | | 446 | | V |E7->A7 447 | | +----------+ E3->A3 +--------+ 448 | | | INACTIVE |------->| LISTEN | 449 | | +----------+ +--------+ 450 | | E2->A2| ^ |E5->A5 451 | | | | | 452 | |E7->A6 V |E6 | 453 | \ +------------+ | 454 | ------| CONNECTING | | 455 | +------------+ | 456 E7->A8 | |E4->A4 | 457 E8->A8 | | | 458 E9->A8 | V | 459 \ +-------------+ / 460 --------------| ESTABLISHED |<--------- 461 +-------------+ 462 | ^ 463 | | 464 E10->A9 \______/ 466 11.1. Events 468 E1) Enable MSDP peering with P 469 E2) Own IP address < P's IP address 470 E3) Own IP address > P's IP address 471 E4) TCP established (active side) 472 E5) TCP established (passive side) 473 E6) ConnectRetry timer expired 474 E7) Disable MSDP peering with P (e.g. when one's own address is 475 changed) 476 E8) Hold Timer expired 477 E9) MSDP TLV format error detected 478 E10) Any other error detected 480 11.2. Actions 482 A1) Allocate resources for peering with P Compare one's own and 483 peer's IP addresses 484 A2) TCP active OPEN Set ConnectRetry timer to 485 [ConnectRetry-Period] 486 A3) TCP passive OPEN (listen) 487 A4) Delete ConnectRetry timer Send KeepAlive TLV 488 Set KeepAlive timer to [KeepAlive-Period] 489 Set Hold Timer to [HoldTime-Period] 490 A5) Send KeepAlive TLV 491 Set KeepAlive timer to [KeepAlive-Period] 492 Set Hold Timer to [HoldTime-Period] 493 A6) Abort TCP active OPEN attempt 494 Release resources allocated for peering with P 495 A7) Abort TCP passive OPEN attempt 496 Release resources allocated for peering with P 497 A8) Close the TCP connection 498 Release resources allocated for peering with P 499 A9) Drop the packet 501 11.3. Peer-specific Events 503 The following peer-specific events can occur in the ESTABLISHED 504 state, they do not cause a state transition. Appropriate actions are 505 listed for each event. 507 *) KeepAlive timer expired: 508 -> Send KeepAlive TLV 509 -> Set KeepAlive timer to [KeepAlive-Period] 510 *) KeepAlive TLV received: 511 -> Set Hold Timer to [HoldTime-Period] 512 *) Source-Active TLV received: 513 -> Set Hold Timer to [HoldTime-Period] 514 -> Run Peer-RPF Forwarding algorithm 515 -> Set KeepAlive timer to [KeepAlive-Period] for those peers 516 the Source-Active TLV is forwarded to 517 -> Send information to PIM-SM 518 -> Store information in cache 520 11.4. Peer-independent Events 522 There are also a number of events that affect more than one peering 523 session, but still require actions to be performed on a per-peer 524 basis. 526 *) SA-Advertisement-Timer expired: 527 -> Start periodic transmission of Source-Active TLV(s) 528 -> Set KeepAlive timer to [KeepAlive-Period] each time a 529 Source-Active TLV is sent 530 *) MSDP learns of a new active internal source (e.g. PIM-SM 531 register received for a new source): 532 -> Send Source-Active TLV 533 -> Set KeepAlive timer to [KeepAlive-Period] 534 *) SG-State-Timer expired (one timer per cache entry): 535 -> Implementation specific, typically mark the cache entry 536 for deletion 538 12. Packet Formats 540 MSDP messages are encoded in TLV format. If an implementation 541 receives a TLV that has length that is longer than expected, the TLV 542 SHOULD be accepted. Any additional data SHOULD be ignored and the 543 MSDP session should not be reset. 545 12.1. MSDP TLV format 547 0 1 2 3 548 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 1 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | Type | Length | Value .... | 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 553 Type (8 bits) 554 Describes the format of the Value field. 556 Length (16 bits) 557 Length of Type, Length, and Value fields in octets. 558 Minimum length required is 4 octets, except for 559 Keepalive messages. The maximum TLV length is 9192. 561 Value (variable length) 562 Format is based on the Type value. See below. The length of 563 the value field is Length field minus 3. All reserved fields 564 in the Value field MUST be transmitted as zeros and ignored on 565 receipt. 567 12.2. Defined TLVs 569 The following TLV Types are defined: 571 Code Type 572 =================================================== 573 1 IPv4 Source-Active 574 2 IPv4 Source-Active Request 575 3 IPv4 Source-Active Response 576 4 KeepAlive 577 5 Reserved (Previously: Notification) 579 Each TLV is described below. 581 In addition, the following TLV Types are assigned but not described 582 in this memo: 584 Code Type 585 ==================================================== 586 6 MSDP traceroute in progress 587 7 MSDP traceroute reply 589 12.2.1. IPv4 Source-Active TLV 591 The maximum size SA message that can be sent is 9192 octets. The 9192 592 octet size does not include the TCP, IP, layer-2 headers. 594 0 1 2 3 595 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 1 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | 1 | x + y | Entry Count | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | RP Address | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 | Reserved | Sprefix Len | \ 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 603 | Group Address | ) z 604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 605 | Source Address | / 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 608 Type 609 IPv4 Source-Active TLV is type 1. 611 Length x 612 Is the length of the control information in the message. x is 613 8 octets (for the first two 32-bit quantities) plus 12 times 614 Entry Count octets. 616 Length y 617 If 0, then there is no data encapsulated. Otherwise an IPv4 618 packet follows and y is the value of the total length field 619 in the header of the encapsulated IP packet. If there are 620 multiple (S,G) entries in an SA message, only the last entry 621 may have encapsulated data and it must reflect the source and 622 destination addresses in the header of the encapsulated IP 623 packet. 625 Entry Count 626 Is the count of z entries (note above) which follow the RP 627 address field. This is so multiple (S,G)s from the same domain 628 can be encoded efficiently for the same RP address. An 629 SA message containing encapsulated data typically has an 630 entry count of 1 (i.e. only contains a single entry, for 631 the (S,G) representing the encapsulated packet). 633 RP Address 634 The address of the RP in the domain the source has become 635 active in. 637 Reserved 638 The Reserved field MUST be transmitted as zeros and MUST be 639 ignored by a receiver. 641 Sprefix Len 642 The route prefix length associated with source address. 643 This field MUST be transmitted as 32 (/32). 645 Group Address 646 The group address the active source has sent data to. 648 Source Address 649 The IP address of the active source. 651 Multiple (S,G) entries MAY appear in the same SA and can be batched 652 for efficiency at the expense of data latency. This would typically 653 occur on intermediate forwarding of SA messages. 655 12.2.2. KeepAlive TLV 657 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 658 MSDP messages sent to the peer within [KeepAlive-Period] seconds. 659 This message is necessary to keep the MSDP connection alive. 661 0 1 2 3 662 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 1 663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 664 | 4 | 3 | 665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 667 The length of the message is 3 octets which encompasses the one octet 668 Type field and the two octet Length field. 670 13. MSDP Error Handling 672 If an MSDP message is received with a TLV format error, the session 673 SHOULD be reset with that peer. MSDP messages with other errors, such 674 as unrecognized type code, received from MSDP peers, SHOULD be 675 silently discarded and the session SHOULD not be reset. 677 14. SA Data Encapsulation 679 As discussed earlier, TCP encapsulation of data in SA messages MAY be 680 supported for backwards compatibility with legacy MSDP peers. 682 15. Applicability Statement 684 MSDP is used primarily in two deployment scenarios: 686 15.1. Between PIM Domains 688 MSDP can be used between PIM domains to convey information about 689 active sources available in other domains. MSDP peering used in such 690 cases is generally one to one peering, and utilizes the deterministic 691 peer-RPF rules described in this spec (i.e., does not use mesh- 692 groups). Peerings can be aggregated on a single MSDP peer, typically 693 from one to hundreds of peerings, similar in scale, although not 694 necessarily consistent, with BGP peerings. 696 15.2. Between Anycast-RPs 698 MSDP is also used between Anycast-RPs [RFC3446] within a PIM domain 699 to synchronize information about the active sources being served by 700 each Anycast-RP peer (by virtue of IGP reachability). MSDP peering 701 used in this scenario is typically based on MSDP mesh groups, where 702 anywhere from two to tens of peers can comprise a given mesh group, 703 although more than ten is not typical. One or more of these mesh- 704 group peers may then also have additional one-to-one peering with 705 msdp peers outside that PIM domain as described in scenario A, for 706 discovery of external sources. MSDP for anycast-RP without external 707 MSDP peering is a valid deployment option and common. 709 16. Intellectual Property 711 The IETF takes no position regarding the validity or scope of any 712 intellectual property or other rights that might be claimed to 713 pertain to the implementation or use of the technology described in 714 this document or the extent to which any license under such rights 715 might or might not be available; neither does it represent that it 716 has made any effort to identify any such rights. Information on the 717 IETF's procedures with respect to rights in standards-track and 718 standards-related documentation can be found in BCP-11. Copies of 719 claims of rights made available for publication and any assurances of 720 licenses to be made available, or the result of an attempt made to 721 obtain a general license or permission for the use of such 722 proprietary rights by implementors or users of this specification can 723 be obtained from the IETF Secretariat. 725 The IETF invites any interested party to bring to its attention any 726 copyrights, patents or patent applications, or other proprietary 727 rights which may cover technology that may be required to practice 728 this standard. Please address the information to the IETF Executive 729 Director. 731 17. Acknowledgments 733 The editors would like to thank the original authors, Dino Farinacci, 734 Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their 735 original contribution to the MSDP specification. In addition, Bill 736 Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, 737 John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina 738 Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning 739 Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided 740 useful and productive design feedback and comments. Mike McBride, 741 Leonard Giuliano, Swapna Yelamanchi, Toerless Eckert, John Meylor and 742 Ishan Wu contributed to the final version of the draft. 744 18. Security Considerations 746 An MSDP implementation SHOULD implement Keyed MD5 [RFC2385] to secure 747 control messages, and MUST be capable of interoperating with peers 748 that do not support it. However, if one side of the connection is 749 configured with Keyed MD5 and the other side is not, the connection 750 SHOULD NOT be established. 752 In addition, to mitigate state explosion during denial of service and 753 other attacks, SA filters and limits SHOULD be used with MSDP to 754 limit the sources and groups that will be passed between RPs. 756 19. IANA Considerations 758 This document defines the seven MSDP TLV values specificed in Section 759 12.2. 761 19.1. IANA Allocated TLV Range 763 MSDP TLV values in the range [8,200] (inclusive) are to be allocated 764 using an IESG Approval or Standards Action process. 766 19.2. Experimental TLV Range 768 TLV values in the range [201,255] (inclusive) are allocated for 769 experimental use. 771 20. References 773 20.1. Normative References 775 [RFC1142] Oran, D. "OSI IS-IS Intra-domain Routing 776 Protocol", RFC 1142, February 1990. 778 [RFC2178] Moy, J., "OSPF Version 2", RFC 2178, April, 1998. 780 [RFC2283] Bates, T., Chandra, R., Katz, D., and 781 Y. Rekhter., "Multiprotocol Extensions for 782 BGP-4", RFC 2283, February 1998. 784 [RFC2362] Estrin D., et al., "Protocol Independent 785 Multicast - Sparse Mode (PIM-SM): Protocol 786 Specification", RFC 2362, June 1998. 788 [RFC2365] Meyer, D. "Administratively Scoped IP Multicast", 789 RFC 2365, July, 1998. 791 [RFC2385] Heffernan. A, "Protection of BGP Sessions via the 792 TCP MD5 Signature Option", August, 1998. 794 [RFC3446] Kim, D., et al., "Anycast Rendezvous Point (RP) 795 Mechanism using Protocol Independent Multicast 796 (PIM) and Multicast Source Discovery Protocol 797 (MSDP)", RFC 3446, January, 2003. 799 20.2. Informative References 801 [RFC2119] S. Bradner, "Key words for use in RFCs to 802 Indicate Requirement Levels", RFC 2119, March, 803 1997. 805 21. Editor's Addresses 807 Bill Fenner 808 AT&T Labs -- Research 809 75 Willow Road 810 Menlo Park, CA 94025 811 Email: fenner@research.att.com 813 David Meyer 814 Email: dmm@maoz.com 816 22. Full Copyright Statement 818 Copyright (C) The Internet Society (2003). All Rights Reserved. 820 This document and translations of it may be copied and furnished to 821 others, and derivative works that comment on or otherwise explain it 822 or assist in its implementation may be prepared, copied, published 823 and distributed, in whole or in part, without restriction of any 824 kind, provided that the above copyright notice and this paragraph are 825 included on all such copies and derivative works. However, this 826 document itself may not be modified in any way, such as by removing 827 the copyright notice or references to the Internet Society or other 828 Internet organizations, except as needed for the purpose of 829 developing Internet standards in which case the procedures for 830 copyrights defined in the Internet Standards process must be 831 followed, or as required to translate it into languages other than 832 English. 834 The limited permissions granted above are perpetual and will not be 835 revoked by the Internet Society or its successors or assigns. 837 This document and the information contained herein is provided on an 838 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 839 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 840 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 841 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 842 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.