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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 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.) -- 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: 'SG-State-Period' is mentioned on line 193, but not defined == Missing Reference: 'SA-Advertisement-Period' is mentioned on line 194, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 194, but not defined == Missing Reference: 'HoldTime-Period' is mentioned on line 465, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 610, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 436, but not defined == Unused Reference: 'IANA' is defined on line 667, but no explicit reference was found in the text == Unused Reference: 'RFC768' is defined on line 669, but no explicit reference was found in the text == Unused Reference: 'RFC1191' is defined on line 672, but no explicit reference was found in the text == Unused Reference: 'RFC1771' is defined on line 675, but no explicit reference was found in the text == Unused Reference: 'RFC2784' is defined on line 695, but no explicit reference was found in the text -- Possible downref: Non-RFC (?) normative reference: ref. 'IANA' ** Obsolete normative reference: RFC 1771 (Obsoleted by RFC 4271) ** Obsolete normative reference: RFC 2283 (Obsoleted by RFC 2858) ** Obsolete normative reference: RFC 2362 (Obsoleted by RFC 4601, RFC 5059) ** Obsolete normative reference: RFC 2401 (Obsoleted by RFC 4301) Summary: 10 errors (**), 0 flaws (~~), 17 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group David Meyer 2 (Editor) 3 INTERNET DRAFT Bill Fenner 4 (Editor) 5 Category 6 Standards Track 8 April, 2003 10 Multicast Source Discovery Protocol (MSDP) 11 13 Status of this Memo 15 This document is an Internet-Draft and is in full conformance with 16 all provisions of Section 10 of RFC 2026. 18 Internet Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that other 20 groups may also distribute working documents as Internet-Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 Abstract 35 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 36 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 37 its own independent Rendezvous Point (RP) and does not have to depend 38 on RPs in other domains. This draft is intended to document existing 39 MSDP implementations in the field. 41 Copyright Notice 43 Copyright (C) The Internet Society (2003). All Rights Reserved. 45 1. Introduction 47 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 48 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 49 its own independent RP(s) and does not have to depend on RPs in other 50 domains. Advantages of this approach include: 52 o No Third-party resource dependencies on RP 54 PIM-SM domains can rely on their own RPs only. 56 o Receiver only Domains 58 Domains with only receivers get data without globally 59 advertising group membership. 61 Note that MSDP may be used with protocols other than PIM-SM, but such 62 usage is not specified in this memo. 64 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, 65 SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined 66 in RFC 2119 [RFC2119]. 68 2. Overview 70 MSDP-speaking routers in a PIM-SM [RFC2362] domain have a MSDP 71 peering relationship with MSDP peers in another domain. The peering 72 relationship is made up of a TCP connection in which control 73 information is exchanged. Each domain has one or more connections to 74 this virtual topology. 76 The purpose of this topology is to allow domains to discover 77 multicast sources from other domains. If the multicast sources are of 78 interest to a domain which has receivers, the normal source-tree 79 building mechanism in PIM-SM will be used to deliver multicast data 80 over an inter-domain distribution tree. 82 3. Procedure 84 When an RP in a PIM-SM domain first learns of a new sender, e.g. via 85 PIM register messages, it constructs a "Source-Active" (SA) message 86 and sends it to its MSDP peers. All RPs, which intend to originate 87 or receive SA messages, must establish MSDP peering with other RPs, 88 either directly or via an intermediate MSDP peer. The SA message 89 contains the following fields: 91 o Source address of the data source. 92 o Group address the data source sends to. 93 o IP address of the RP. 95 Note that an RP that isn't a DR on a shared network SHOULD NOT 96 originate SA's for directly connected sources on that shared network; 97 it should only originate in response to receiving Register messages 98 from the DR. 100 Each MSDP peer receives and forwards the message away from the RP 101 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 102 flooding is with respect to forwarding SA messages. The Multicast RPF 103 Routing Information Base (MRIB) is examined to determine which peer 104 towards the originating RP of the SA message is selected. Such a peer 105 is called an "RPF peer". See section 13 for the details of peer-RPF 106 forwarding. 108 If the MSDP peer receives the SA from a non-RPF peer towards the 109 originating RP, it will drop the message. Otherwise, it forwards the 110 message to all its MSDP peers (except the one from which it received 111 the SA message). 113 When an MSDP peer which is also an RP for its own domain receives a 114 new SA message, it determines if there are any group members within 115 the domain interested in any group described by an (S,G) entry within 116 the SA message. That is, the RP checks for a (*,G) entry with a non- 117 empty outgoing interface list; this implies that some system in the 118 domain is interested in the group. In this case, the RP triggers a 119 (S,G) join event towards the data source as if a Join/Prune message 120 was received addressed to the RP itself. This sets up a branch of the 121 source-tree to this domain. Subsequent data packets arrive at the RP 122 via this tree branch, and are forwarded down the shared-tree inside 123 the domain. If leaf routers choose to join the source-tree they have 124 the option to do so according to existing PIM-SM conventions. 125 Finally, if an RP in a domain receives a PIM Join message for a new 126 group G, the RP SHOULD trigger a (S,G) join event for each active 127 (S,G) for that group in its SA cache. 129 This procedure has been affectionately named flood-and-join because 130 if any RP is not interested in the group, they can ignore the SA 131 message. Otherwise, they join a distribution tree. 133 4. Caching 135 A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP 136 messages as well as reducing join latency for new receivers of a 137 group G at an originating RP which has existing MSDP (S,G) state. In 138 addition, caching greatly aids in diagnosis and debugging of various 139 problems. 141 An MSDP speaker must provide a mechanism to reduce the forwarding of 142 new SA's. The SA-cache is used to reduce storms and performs this 143 by not forwarding SA's unless they are in the cache or are new SA 144 packets that the MSDP speaker will cache for the first time. The 145 SA-cache also reduces storms by advertising from the cache at a 146 period of no more than twice per SA-Advertisement-Timer interval and 147 not less than 1 time per SA Advertisment period. 149 5. Timers 151 The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry 152 timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer. 153 Each is considered below. 155 5.1. SA-Advertisement-Timer 157 RPs which originate SA messages do so periodically as long as there 158 is data being sent by the source. There is one SA-Advertisement-Timer 159 covering the sources that an RP may advertise. [SA-Advertisement- 160 Period] MUST be 60 seconds. An RP MUST not send more than one 161 periodic SA message for a given (S,G) within an SA Advertisement 162 interval. Originating periodic SA messages is required to keep 163 announcements alive in caches. Finally, an originating RP SHOULD 164 trigger the transmission of an SA message as soon as it receives data 165 from an internal source for the first time. This initial SA message 166 may be in addition to the periodic sa-message forwarded in that first 167 60 seconds for that S,G. 169 5.2. SA-Advertisement-Timer Processing 171 An RP MUST spread the generation of periodic SA messages (i.e. 172 messages advertising the active sources for which it is the RP) over 173 its reporting interval (i.e. SA-Advertisement-Period). An RP starts 174 the SA-Advertisement-Timer when the MSDP process is configured. When 175 the timer expires, an RP resets the timer to [SA-Advertisement- 176 Period] seconds, and begins the advertisement of its active sources. 177 Active sources are advertised in the following manner: An RP packs 178 its active sources into an SA message until the largest MSDP packet 179 that can be sent is built or there are no more sources, and then 180 sends the message. This process is repeated periodically within the 181 SA-Advertisement-Period in such a way that all of the RP's sources 182 are advertised. Note that since MSDP is a periodic protocol, an 183 implemenation SHOULD send all cached SA messages when a connection is 184 established. Finally, the timer is deleted when the MSDP process is 185 deconfigured. 187 5.3. SA Cache Timeout (SA-State Timer) 189 Each entry in an SA Cache has an associated SA-State Timer. A 190 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 191 received by an MSDP peer. The timer is reset to [SG-State-Period] if 192 another (S,G)-SA message is received before the (S,G)-SA-State Timer 193 expires. [SG-State-Period] MUST NOT be less than 194 [SA-Advertisement-Period] + [SA-Hold-Down-Period]. 196 5.4. Peer Hold Timer 198 The Hold Timer is initialized to [HoldTime-Period] when the peer's 199 transport connection is established, and is reset to [HoldTime- 200 Period] when any MSDP message is received. Finally, the timer is 201 deleted when the peer's transport connection is closed. 202 [HoldTime-Period] MUST be at least three seconds. The recommended 203 value for [HoldTime-Period] is 75 seconds. 205 5.5. KeepAlive Timer 207 Once an MSDP transport connection is established, each side of the 208 connection sends a KeepAlive message and sets a KeepAlive timer. If 209 the KeepAlive timer expires, the local system sends a KeepAlive 210 message and restarts its KeepAlive timer. 212 The KeepAlive timer is set to [KeepAlive-Period] when the peer comes 213 up. The timer is reset to [KeepAlive-Period] each time an MSDP 214 message is sent to the peer, and reset when the timer expires. 216 Finally, the KeepAlive timer is deleted when the peer's transport 217 connection is closed. 219 [KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be 220 at least one second. The recommended value for [KeepAlive-Period] is 221 60 seconds. 223 5.6. ConnectRetry Timer 225 The ConnectRetry timer is used by the MSDP peer with the lower IP 226 address to transition from INACTIVE to CONNECTING states. There is 227 one timer per peer, and the [ConnectRetry-Period] SHOULD be set to 30 228 seconds. The timer is initialized to [ConnectRetry-Period] when an 229 MSDP speaker attempts to actively open a TCP connection to its peer 230 (see section 15, event E2, action A2 ). When the timer expires, the 231 peer retries the connection and the timer is reset to [ConnectRetry- 232 Period]. It is deleted if either the connection transitions into 233 ESTABLISHED state or the peer is deconfigured. 235 6. Intermediate MSDP Peers 237 Intermediate MSDP speakers do not originate periodic SA messages on 238 behalf of sources in other domains. In general, an RP MUST only 239 originate an SA for a source which would register to it, and ONLY RPs 240 may originate SA messages. 242 7. SA Filtering and Policy 244 As the number of (S,G) pairs increases in the Internet, an RP may 245 want to filter which sources it describes in SA messages. Also, 246 filtering may be used as a matter of policy which at the same time 247 can reduce state. MSDP peers in transit domains should not filter 248 SA messages or the flood-and-join model can not guarantee that 249 sources will be known throughout the Internet (i.e., SA filtering 250 by transit domains may cause undesired lack of connectivity). In 251 general, policy should be expressed using MBGP [RFC2283]. This 252 will cause MSDP messages to flow in the desired direction and 253 peer-RPF fail otherwise. An exception occurs at an administrative 254 scope [RFC2365] boundary. In particular, a SA message for a (S,G) 255 MUST NOT be sent to peers which are on the other side of an 256 administrative scope boundary for G. 258 8. Encapsulated Data Packets 260 The RP MAY encapsulate multicast data from the source. An interested 261 RP may decapsulate the packet, which SHOULD be forwarded as if a PIM 262 register encapsulated packet was received. That is, if packets are 263 already arriving over the interface toward the source, then the 264 packet is dropped. Otherwise, if the outgoing interface list is non- 265 null, the packet is forwarded appropriately. Note that when doing 266 data encapsulation, an implementation MUST bound the time during 267 which packets are encapsulated. 269 This allows for small bursts to be received before the multicast tree 270 is built back toward the source's domain. For example, an 271 implementation SHOULD encapsulate at least the first packet to 272 provide service to bursty sources. 274 9. Other Scenarios 276 MSDP is not limited to deployment across different routing domains. 277 It can be used within a routing domain when it is desired to deploy 278 multiple RPs for the same group ranges such as with Anycast RP's. 279 As long as all RPs have a interconnected MSDP topology, each can 280 learn about active sources as well as RPs in other domains. 282 10. MSDP Peer-RPF Forwarding 284 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 285 messages throughout an MSDP enabled internet. Unlike the RPF check 286 used when forwarding data packets, which generally compares the 287 packet's source address against the interface upon which the packet 288 was received, the Peer-RPF check compares the RP address carried in 289 the SA message against the MSDP peer from which the message was 290 received. 292 10.1. Definitions 294 The following definitions are used in the description of the Peer-RPF 295 Forwarding Rules: 297 10.1.1. Multicast RPF Routing Information Base (MRIB) 299 The MRIB is the multicast topology table. It is typically derived 300 from the unicast routing table or from other routing protocols such 301 as multi-protocol BGP [RFC2283]. 303 10.1.2. Peer-RPF Route 305 The Peer-RPF route is the route that the MRIB chooses for a given 306 address. The Peer-RPF route for a SA's originating RP is used to 307 select the peer from which the SA is accepted. 309 10.2. Peer-RPF Forwarding Rules 311 An SA message originated by R and received by X from N is 312 accepted if N is the peer-RPF neighbor for X, and is discarded 313 otherwise. 315 MPP(R,N) MP(N,X) 316 R ---------....-------> N ------------------> X 317 SA(S,G,R) SA(S,G,R) 319 MP(N,X) is an MSDP peering between N and X. MPP(R,N) is 320 an MSDP peering path (zero or more MSDP peers) between 321 R and N, e.g. MPP(R,N) = MP(R, A) + MP(A, B) + MP(B, 322 N). SA(S,G,R) is an SA message for source S on group G 323 originated by an RP R. 325 The peer-RPF neighbor N is chosen deterministically, using the 326 first of the following rules that matches. In particular, 327 N is the RPF neighbor of X with respect to R if 329 (i). N == R (X has an MSDP peering with R). 331 (ii). N is the eBGP NEXT_HOP of the Peer-RPF route 332 for R. 334 (iii). The Peer-RPF route for R is learned through a 335 distance-vector or path-vector routing protocol 336 (e.g. BGP, RIP, DVMRP) and N is the neighbor that 337 advertised the Peer-RPF route for R (e.g. N is the 338 iBGP advertiser of the route for R), or N is the 339 IGP next hop for R if the route for R is learned 340 via a link-state protocol (e.g. OSPF or ISIS). 342 (iv). N resides in the closest AS in the best path towards 343 R. If multiple MSDP peers reside in the closest AS, 344 the peer with the highest IP address is the rpf-peer. 346 (v). N is configured as the static RPF-peer for R. 348 MSDP peers, which are NOT in state ESTABLISHED (ie down peers), are 349 not eligible for peer RPF consideration. 351 10.3. MSDP mesh-group semantics 353 An MSDP mesh-group is a operational mechanism for reducing SA 354 flooding, typically in an intra-domain setting. In particular, when 355 some subset of a domain's MSDP speakers are fully meshed, they can be 356 configured into a mesh-group. 358 Note that mesh-groups assume that a member doesn't have to forward an 359 SA to other members of the mesh-group because the originator will 360 forward to all members. To be able for the originator to forward to 361 all members (and to have each member also be a potential originator), 362 the mesh-group must be a full mesh of MSDP peering among all members. 364 The semantics of the mesh-group are as follows: 366 (i). If a member R of a mesh-group M receives a SA message from an 367 MSDP peer that is also a member of mesh-group M, R accepts the 368 SA message and forwards it to all of its peers that are not 369 part of mesh-group M. R MUST NOT forward the SA message to 370 other members of mesh-group M. 372 (ii). If a member R of a mesh-group M receives an SA message from an 373 MSDP peer that is not a member of mesh-group M, and the SA 374 message passes the peer-RPF check, then R forwards the SA 375 message to all members of mesh-group M and to any other 376 msdp peers. 378 11. MSDP Connection State Machine 380 MSDP uses TCP as its transport protocol. In a peering relationship, 381 one MSDP peer listens for new TCP connections on the well-known port 382 639. The other side makes an active connect to this port. The peer 383 with the higher IP address will listen. This connection establishment 384 algorithm avoids call collision. Therefore, there is no need for a 385 call collision procedure. It should be noted, however, that the 386 disadvantage of this approach is that the startup time depends 387 completely upon the active side and its connect retry timer; the 388 passive side cannot cause the connection to be established. 390 An MSDP peer starts in the DISABLED state. MSDP peers establish 391 peering sessions according to the following state machine: 393 --------------->+----------+ 394 / | DISABLED |<---------- 395 | ------>+----------+ \ 396 | / |E1->A1 | 397 | | | | 398 | | V |E7->A7 399 | | +----------+ E3->A3 +--------+ 400 | | | INACTIVE |------->| LISTEN | 401 | | +----------+ +--------+ 402 | | E2->A2| ^ |E5->A5 403 | | | | | 404 | |E7->A6 V |E6 | 405 | \ +------------+ | 406 | ------| CONNECTING | | 407 | +------------+ | 408 E7->A8 | |E4->A4 | 409 E8->A8 | | | 410 E9->A8 | V | 411 \ +-------------+ / 412 --------------| ESTABLISHED |<--------- 413 +-------------+ 414 | ^ 415 | | 416 E10->A9\______/ 417 11.1. Events 419 E1) Enable MSDP peering with P 420 E2) Own IP address < P's IP address 421 E3) Own IP address > P's IP address 422 E4) TCP established (active side) 423 E5) TCP established (passive side) 424 E6) ConnectRetry timer expired 425 E7) Disable MSDP peering with P 426 (e.g. when one's own address is changed) 427 E8) Hold Timer expired 428 E9) MSDP TLV format error detected 429 E10) Any other error detected 431 11.2. Actions 433 A1) Allocate resources for peering with P 434 Compare one's own and peer's IP addresses 435 A2) TCP active OPEN 436 Set ConnectRetry timer to [ConnectRetry-Period] 437 A3) TCP passive OPEN (listen) 438 A4) Delete ConnectRetry timer 439 Send KeepAlive TLV 440 Set KeepAlive timer to [KeepAlive-Period] 441 Set Hold Timer to [HoldTime-Period] 442 A5) Send KeepAlive TLV 443 Set KeepAlive timer to [KeepAlive-Period] 444 Set Hold Timer to [HoldTime-Period] 445 A6) Abort TCP active OPEN attempt 446 Release resources allocated for peering with P 447 A7) Abort TCP passive OPEN attempt 448 Release resources allocated for peering with P 449 A8) Close the TCP connection 450 Release resources allocated for peering with P 451 A9) Drop the packet 453 11.3. Peer-specific Events 455 The following peer-specific events can occur in the ESTABLISHED 456 state, they do not cause a state transition. Appropriate actions are 457 listed for each event. 459 *) KeepAlive timer expired: 460 -> Send KeepAlive TLV 461 -> Set KeepAlive timer to [KeepAlive-Period] 462 *) KeepAlive TLV received: 463 -> Set Hold Timer to [HoldTime-Period] 464 *) Source-Active TLV received: 465 -> Set Hold Timer to [HoldTime-Period] 466 -> Run Peer-RPF Forwarding algorithm 467 -> Set KeepAlive timer to [KeepAlive-Period] for those peers 468 the Source-Active TLV is forwarded to 469 -> Send information to PIM-SM 470 -> Store information in cache 472 11.4. Peer-independent Events 474 There are also a number of events that affect more than one peering 475 session, but still require actions to be performed on a per-peer 476 basis. 478 *) SA-Advertisement-Timer expired: 479 -> Start periodic transmission of Source-Active TLV(s) 480 -> Set KeepAlive timer to [KeepAlive-Period] each time a 481 Source-Active TLV is sent 482 *) MSDP learns of a new active internal source (e.g. PIM-SM 483 register received for a new source): 484 -> Send Source-Active TLV 485 -> Set KeepAlive timer to [KeepAlive-Period] 486 *) SG-State-Timer expired (one timer per cache entry): 487 -> Implementation specific, typically mark the cache entry for 488 deletion 490 12. Packet Formats 492 MSDP messages will be encoded in TLV format. If an implementation 493 receives a TLV that has length that is longer than expected, the TLV 494 SHOULD be accepted. Any additional data SHOULD be ignored and the 495 MSDP session should not be reset. 497 12.1. MSDP TLV format: 499 0 1 2 3 500 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 1 501 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 | Type | Length | Value .... | 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 Type (8 bits) 506 Describes the format of the Value field. 508 Length (16 bits) 509 Length of Type, Length, and Value fields in octets. 510 Minimum length required is 4 octets, except for 511 Keepalive messages. The maximum TLV length is 9192. 513 Value (variable length) 514 Format is based on the Type value. See below. The length of 515 the value field is Length field minus 3. All reserved fields 516 in the Value field MUST be transmitted as zeros and ignored on 517 receipt. 519 12.2. Defined TLVs 521 The following TLV Types are defined: 523 Code Type 524 =========================================================== 525 1 IPv4 Source-Active 526 2 IPv4 Source-Active Request 527 3 IPv4 Source-Active Response 528 4 KeepAlive 529 5 Reserved (Previously: Notification) 531 Each TLV is described below. 533 In addition, the following TLV Types are assigned but not described 534 in this memo: 536 Code Type 537 =========================================================== 538 6 MSDP traceroute in progress 539 7 MSDP traceroute reply 541 12.2.1. IPv4 Source-Active TLV 543 The maximum size SA message that can be sent is 9192 octets. The 9192 544 octet size does not include the TCP, IP, layer-2 headers. 546 0 1 2 3 547 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 1 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 | 1 | x + y | Entry Count | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | RP Address | 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 553 | Reserved | Sprefix Len | \ 554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 555 | Group Address | ) z 556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 557 | Source Address | / 558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 Type 561 IPv4 Source-Active TLV is type 1. 563 Length x 564 Is the length of the control information in the message. x is 565 8 octets (for the first two 32-bit quantities) plus 12 times 566 Entry Count octets. 568 Length y 569 If 0, then there is no data encapsulated. Otherwise an IPv4 570 packet follows and y is the value of the total length field 571 in the header of the encapsulated IP packet. If there are 572 multiple (S,G) entries in an SA message, only the last entry 573 may have encapsulated data and it must reflect the source and 574 destination addresses in the header of the encapsulated IP 575 packet. 577 Entry Count 578 Is the count of z entries (note above) which follow the RP 579 address field. This is so multiple (S,G)s from the same domain 580 can be encoded efficiently for the same RP address. An 581 SA message containing encapsulated data typically has an 582 entry count of 1 (i.e. only contains a single entry, for 583 the (S,G) representing the encapsulated packet). 585 RP Address 586 The address of the RP in the domain the source has become 587 active in. 589 Reserved 590 The Reserved field MUST be transmitted as zeros and MUST be 591 ignored by a receiver. 593 Sprefix Len 594 The route prefix length associated with source address. 595 This field MUST be transmitted as 32 (/32). 597 Group Address 598 The group address the active source has sent data to. 600 Source Address 601 The IP address of the active source. 603 Multiple (S,G) entries MAY appear in the same SA and can be batched 604 for efficiency at the expense of data latency. This would typically 605 occur on intermediate forwarding of SA messages. 607 12.2.2. KeepAlive TLV 609 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 610 MSDP messages sent to the peer within [KeepAlive-Period] seconds. 611 This message is necessary to keep the MSDP connection alive. 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 | 4 | 3 | 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 The length of the message is 3 octets which encompasses the one octet 620 Type field and the two octet Length field. 622 13. MSDP Error Handling 624 If an MSDP message is received with a TLV format error, the session 625 SHOULD be reset with that peer. MSDP messages with other errors, such 626 as unrecognized type code, received from MSDP peers, SHOULD be silently 627 discarded and the session SHOULD not be reset. 629 14. SA Data Encapsulation 631 As discussed earlier, TCP encapsulation of data in SA messages MAY be 632 supported for backwards compatibility with legacy MSDP peers. 634 15. Security Considerations 636 An MSDP implementation MAY use IPsec [RFC2401] or MD5 to secure control 637 messages. In particular, the TCP connection between MSDP peers MAY 638 be secured using IPsec or MD5. Implementations MUST be capable of 639 working with peers which do not provide IPsec or MD5 security. 641 16. Acknowledgments 643 The editors would like to thank the original authors, Dino Farinacci, 644 Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their 645 orginal contribution to the MSDP specification. In addition, Bill 646 Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, 647 John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina 648 Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning 649 Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided 650 useful and productive design feedback and comments. Mike McBride, 651 Leonard Giuliano, Swapna Yelamanchi, Toerless Eckert and Ishan Wu 652 contributed to the final version of the draft. 654 17. Editors' Address: 656 David Meyer 657 Email: dmm@maoz.com 659 Bill Fenner 660 AT&T Labs -- Research 661 75 Willow Road 662 Menlo Park, CA 94025 663 Email: fenner@research.att.com 665 18. REFERENCES 667 [IANA] http://www.iana.org 669 [RFC768] Postel, J. "User Datagram Protocol", RFC 768, August, 670 1980. 672 [RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery", 673 RFC 1191, November 1990. 675 [RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 676 (BGP-4)", RFC 1771, March 1995. 678 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 679 Requirement Levels", RFC 2119, March, 1997. 681 [RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., 682 "Multiprotocol Extensions for BGP-4", RFC 2283, 683 February 1998. 685 [RFC2362] Estrin D., et al., "Protocol Independent Multicast - 686 Sparse Mode (PIM-SM): Protocol Specification", RFC 687 2362, June 1998. 689 [RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC 690 2365, July, 1998. 692 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for 693 the Internet Protocol", RFC 2401, November 1998. 695 [RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation 696 (GRE)", RFC 2784, March 2000. 698 19. Full Copyright Statement 700 Copyright (C) The Internet Society (2003). All Rights Reserved. 702 This document and translations of it may be copied and furnished to 703 others, and derivative works that comment on or otherwise explain it 704 or assist in its implementation may be prepared, copied, published 705 and distributed, in whole or in part, without restriction of any 706 kind, provided that the above copyright notice and this paragraph are 707 included on all such copies and derivative works. However, this 708 document itself may not be modified in any way, such as by removing 709 the copyright notice or references to the Internet Society or other 710 Internet organizations, except as needed for the purpose of 711 developing Internet standards in which case the procedures for 712 copyrights defined in the Internet Standards process must be 713 followed, or as required to translate it into languages other than 714 English. 716 The limited permissions granted above are perpetual and will not be 717 revoked by the Internet Society or its successors or assigns. 719 This document and the information contained herein is provided on an 720 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 721 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 722 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 723 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 724 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.