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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 SA is received with a TLV format error, the session SHOULD be reset with that peer. All other errors, received from MSDP peers, SHOULD silently discard the packets 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 191, but not defined == Missing Reference: 'SA-Advertisement-Period' is mentioned on line 192, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 192, but not defined == Missing Reference: 'HoldTime-Period' is mentioned on line 462, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 607, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 433, 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: 11 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 November, 2002 10 Multicast Source Discovery Protocol (MSDP) 11 13 1. 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 2. 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 RP(s) and does not have to depend on RPs in other 38 domains. This draft is intended to document existing MSDP 39 implementations in the field. 41 3. Copyright Notice 43 Copyright (C) The Internet Society (2002). All Rights Reserved. 45 4. 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 5. 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 6. 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. The SA message contains the following 87 fields: 89 o Source address of the data source. 90 o Group address the data source sends to. 91 o IP address of the RP. 93 Note that an RP that isn't a DR on a shared network SHOULD NOT 94 originate SA's for directly connected sources on that shared network; 95 it should only originate in response to receiving Register messages 96 from the DR. 98 Each MSDP peer receives and forwards the message away from the RP 99 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 100 flooding is with respect to forwarding SA messages. The Multicast RPF 101 Routing Information Base (MRIB) is examined to determine which peer 102 towards the originating RP of the SA message is selected. Such a peer 103 is called an "RPF peer". See section 13 for the details of peer-RPF 104 forwarding. 106 If the MSDP peer receives the SA from a non-RPF peer towards the 107 originating RP, it will drop the message. Otherwise, it forwards the 108 message to all its MSDP peers (except the one from which it received 109 the SA message). 111 When an MSDP peer which is also an RP for its own domain receives a 112 new SA message, it determines if there are any group members within 113 the domain interested in any group described by an (S,G) entry within 114 the SA message. That is, the RP checks for a (*,G) entry with a non- 115 empty outgoing interface list; this implies that some system in the 116 domain is interested in the group. In this case, the RP triggers a 117 (S,G) join event towards the data source as if a Join/Prune message 118 was received addressed to the RP itself. This sets up a branch of the 119 source-tree to this domain. Subsequent data packets arrive at the RP 120 via this tree branch, and are forwarded down the shared-tree inside 121 the domain. If leaf routers choose to join the source-tree they have 122 the option to do so according to existing PIM-SM conventions. 123 Finally, if an RP in a domain receives a PIM Join message for a new 124 group G, the RP SHOULD trigger a (S,G) join event for each active 125 (S,G) for that group in its SA cache. 127 This procedure has been affectionately named flood-and-join because 128 if any RP is not interested in the group, they can ignore the SA 129 message. Otherwise, they join a distribution tree. 131 7. Caching 133 A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP 134 messages as well as reducing join latency for new receivers of a 135 group G at an originating RP which has existing MSDP (S,G) state. In 136 addition, caching greatly aids in diagnosis and debugging of various 137 problems. 139 An MSDP speaker must provide a mechanism to reduce the forwarding of 140 new SA's. The SA-cache is used to reduce storms and performs this 141 by not forwarding SA's unless they are in the cache or are new SA 142 packets that the MSDP speaker will cache for the first time. The 143 SA-cache also reduces storms by advertising from the cache at a 144 period of no more than twice per SA-Advertisement-Timer interval and 145 not less than 1 time per SA Advertisment period. 147 8. Timers 149 The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry 150 timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer. 151 Each is considered below. 153 8.1. SA-Advertisement-Timer 155 RPs which originate SA messages do so periodically as long as there 156 is data being sent by the source. There is one SA-Advertisement-Timer 157 covering the sources that an RP may advertise. [SA-Advertisement- 158 Period] MUST be 60 seconds. An RP MUST not send more than one 159 periodic SA message for a given (S,G) within an SA Advertisement 160 interval. Originating periodic SA messages is required to keep 161 announcements alive in caches. Finally, an originating RP SHOULD 162 trigger the transmission of an SA message as soon as it receives data 163 from an internal source for the first time. This initial SA message 164 may be in addition to the periodic sa-message forwarded in that first 165 60 seconds for that S,G. 167 8.2. SA-Advertisement-Timer Processing 169 An RP MUST spread the generation of periodic SA messages (i.e. 170 messages advertising the active sources for which it is the RP) over 171 its reporting interval (i.e. SA-Advertisement-Period). An RP starts 172 the SA-Advertisement-Timer when the MSDP process is configured. When 173 the timer expires, an RP resets the timer to [SA-Advertisement- 174 Period] seconds, and begins the advertisement of its active sources. 175 Active sources are advertised in the following manner: An RP packs 176 its active sources into an SA message until the largest MSDP packet 177 that can be sent is built or there are no more sources, and then 178 sends the message. This process is repeated periodically within the 179 SA-Advertisement-Period in such a way that all of the RP's sources 180 are advertised. Note that since MSDP is a periodic protocol, an 181 implemenation SHOULD send all cached SA messages when a connection is 182 established. Finally, the timer is deleted when the MSDP process is 183 deconfigured. 185 8.3. SA Cache Timeout (SA-State Timer) 187 Each entry in an SA Cache has an associated SA-State Timer. A 188 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 189 received by an MSDP peer. The timer is reset to [SG-State-Period] if 190 another (S,G)-SA message is received before the (S,G)-SA-State Timer 191 expires. [SG-State-Period] MUST NOT be less than 192 [SA-Advertisement-Period] + [SA-Hold-Down-Period]. 194 8.4. Peer Hold Timer 196 The Hold Timer is initialized to [HoldTime-Period] when the peer's 197 transport connection is established, and is reset to [HoldTime- 198 Period] when any MSDP message is received. Finally, the timer is 199 deleted when the peer's transport connection is closed. 200 [HoldTime-Period] MUST be at least three seconds. The recommended 201 value for [HoldTime-Period] is 75 seconds. 203 8.5. KeepAlive Timer 205 Once an MSDP transport connection is established, each side of the 206 connection sends a KeepAlive message and sets a KeepAlive timer. If 207 the KeepAlive timer expires, the local system sends a KeepAlive 208 message and restarts its KeepAlive timer. 210 The KeepAlive timer is set to [KeepAlive-Period] when the peer comes 211 up. The timer is reset to [KeepAlive-Period] each time an MSDP 212 message is sent to the peer, and reset when the timer expires. 214 Finally, the KeepAlive timer is deleted when the peer's transport 215 connection is closed. 217 [KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be 218 at least one second. The recommended value for [KeepAlive-Period] is 219 60 seconds. 221 8.6. ConnectRetry Timer 223 The ConnectRetry timer is used by the MSDP peer with the lower IP 224 address to transition from INACTIVE to CONNECTING states. There is 225 one timer per peer, and the [ConnectRetry-Period] SHOULD be set to 30 226 seconds. The timer is initialized to [ConnectRetry-Period] when an 227 MSDP speaker attempts to actively open a TCP connection to its peer 228 (see section 15, event E2, action A2 ). When the timer expires, the 229 peer retries the connection and the timer is reset to [ConnectRetry- 230 Period]. It is deleted if either the connection transitions into 231 ESTABLISHED state or the peer is deconfigured. 233 9. Intermediate MSDP Peers 235 Intermediate MSDP speakers do not originate periodic SA messages on 236 behalf of sources in other domains. In general, an RP MUST only 237 originate an SA for a source which would register to it, and ONLY RPs 238 may originate SA messages. 240 10. SA Filtering and Policy 242 As the number of (S,G) pairs increases in the Internet, an RP may 243 want to filter which sources it describes in SA messages. Also, 244 filtering may be used as a matter of policy which at the same time 245 can reduce state. MSDP peers in transit domains should not filter 246 SA messages or the flood-and-join model can not guarantee that 247 sources will be known throughout the Internet (i.e., SA filtering 248 by transit domains may cause undesired lack of connectivity). In 249 general, policy should be expressed using MBGP [RFC2283]. This 250 will cause MSDP messages to flow in the desired direction and 251 peer-RPF fail otherwise. An exception occurs at an administrative 252 scope [RFC2365] boundary. In particular, a SA message for a (S,G) 253 MUST NOT be sent to peers which are on the other side of an 254 administrative scope boundary for G. 256 11. Encapsulated Data Packets 258 The RP MAY encapsulate multicast data from the source. An interested 259 RP may decapsulate the packet, which SHOULD be forwarded as if a PIM 260 register encapsulated packet was received. That is, if packets are 261 already arriving over the interface toward the source, then the 262 packet is dropped. Otherwise, if the outgoing interface list is non- 263 null, the packet is forwarded appropriately. Note that when doing 264 data encapsulation, an implementation MUST bound the time during 265 which packets are encapsulated. 267 This allows for small bursts to be received before the multicast tree 268 is built back toward the source's domain. For example, an 269 implementation SHOULD encapsulate at least the first packet to 270 provide service to bursty sources. 272 12. Other Scenarios 274 MSDP is not limited to deployment across different routing domains. 275 It can be used within a routing domain when it is desired to deploy 276 multiple RPs for the same group ranges such as with Anycast RP's. 277 As long as all RPs have a interconnected MSDP topology, each can 278 learn about active sources as well as RPs in other domains. 280 13. MSDP Peer-RPF Forwarding 282 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 283 messages throughout an MSDP enabled internet. Unlike the RPF check 284 used when forwarding data packets, which generally compares the 285 packet's source address against the interface upon which the packet 286 was received, the Peer-RPF check compares the RP address carried in 287 the SA message against the MSDP peer from which the message was 288 received. 290 13.1. Definitions 292 The following definitions are used in the description of the Peer-RPF 293 Forwarding Rules: 295 13.1.1. Multicast RPF Routing Information Base (MRIB) 297 The MRIB is the multicast topology table. It is typically derived 298 from the unicast routing table or from other routing protocols such 299 as multi-protocol BGP [RFC2283]. 301 13.1.2. Peer-RPF Route 303 The Peer-RPF route is the route that the MRIB chooses for a given 304 address. The Peer-RPF route for a SA's originating RP is used to 305 select the peer from which the SA is accepted. 307 13.2. Peer-RPF Forwarding Rules 309 An SA message originated by R and received by X from N is 310 accepted if N is the peer-RPF neighbor for X, and is discarded 311 otherwise. 313 MPP(R,N) MP(N,X) 314 R ---------....-------> N ------------------> X 315 SA(S,G,R) SA(S,G,R) 317 MP(N,X) is an MSDP peering between N and X. MPP(R,N) is 318 an MSDP peering path (zero or more MSDP peers) between 319 R and N, e.g. MPP(R,N) = MP(R, A) + MP(A, B) + MP(B, 320 N). SA(S,G,R) is an SA message for source S on group G 321 originated by an RP R. 323 The peer-RPF neighbor N is chosen deterministically, using the 324 first of the following rules that matches. In particular, 325 N is the RPF neighbor of X with respect to R if 327 (i). N == R (X has an MSDP peering with R). 329 (ii). N is the eBGP NEXT_HOP of the Peer-RPF route 330 for R. 332 (iii). The Peer-RPF route for R is learned through a 333 distance-vector or path-vector routing protocol 334 (e.g. BGP, RIP, DVMRP) and N is the neighbor that 335 advertised the Peer-RPF route for R (e.g. N is the 336 iBGP advertiser of the route for R), or N is the 337 IGP next hop for R if the route for R is learned 338 via a link-state protocol (e.g. OSPF or ISIS). 340 (iv). N resides in the closest AS in the best path towards 341 R. If multiple MSDP peers reside in the closest AS, 342 the peer with the highest IP address is the rpf-peer. 344 (v). N is configured as the static RPF-peer for R. 346 MSDP peers, which are NOT in state ESTABLISHED (ie down peers), are 347 not eligible for peer RPF consideration. 349 13.3. MSDP mesh-group semantics 351 An MSDP mesh-group is a operational mechanism for reducing SA 352 flooding, typically in an intra-domain setting. In particular, when 353 some subset of a domain's MSDP speakers are fully meshed, they can be 354 configured into a mesh-group. 356 Note that mesh-groups assume that a member doesn't have to forward an 357 SA to other members of the mesh-group because the originator will 358 forward to all members. To be able for the originator to forward to 359 all members (and to have each member also be a potential originator), 360 the mesh-group must be a full mesh of MSDP peering among all members. 362 The semantics of the mesh-group are as follows: 364 (i). If a member R of a mesh-group M receives a SA message from an 365 MSDP peer that is also a member of mesh-group M, R accepts the 366 SA message and forwards it to all of its peers that are not 367 part of any mesh-group. R MUST NOT forward the SA message to 368 other members of mesh-group M. 370 (ii). If a member R of a mesh-group M receives a SA message from an 371 MSDP peer that is not a member of mesh-group M, and the SA 372 message passes the peer-RPF check, then R forwards the SA 373 message to all members of mesh-group M. 375 14. MSDP Connection State Machine 377 MSDP uses TCP as its transport protocol. In a peering relationship, 378 one MSDP peer listens for new TCP connections on the well-known port 379 639. The other side makes an active connect to this port. The peer 380 with the higher IP address will listen. This connection establishment 381 algorithm avoids call collision. Therefore, there is no need for a 382 call collision procedure. It should be noted, however, that the 383 disadvantage of this approach is that the startup time depends 384 completely upon the active side and its connect retry timer; the 385 passive side cannot cause the connection to be established. 387 An MSDP peer starts in the DISABLED state. MSDP peers establish 388 peering sessions according to the following state machine: 390 --------------->+----------+ 391 / | DISABLED |<---------- 392 | ------>+----------+ \ 393 | / |E1->A1 | 394 | | | | 395 | | V |E7->A7 396 | | +----------+ E3->A3 +--------+ 397 | | | INACTIVE |------->| LISTEN | 398 | | +----------+ +--------+ 399 | | E2->A2| ^ |E5->A5 400 | | | | | 401 | |E7->A6 V |E6 | 402 | \ +------------+ | 403 | ------| CONNECTING | | 404 | +------------+ | 405 E7->A8 | |E4->A4 | 406 E8->A8 | | | 407 E9->A8 | V | 408 \ +-------------+ / 409 --------------| ESTABLISHED |<--------- 410 +-------------+ 411 | ^ 412 | | 413 E10->A9\______/ 414 14.1. Events 416 E1) Enable MSDP peering with P 417 E2) Own IP address < P's IP address 418 E3) Own IP address > P's IP address 419 E4) TCP established (active side) 420 E5) TCP established (passive side) 421 E6) ConnectRetry timer expired 422 E7) Disable MSDP peering with P 423 (e.g. when one's own address is changed) 424 E8) Hold Timer expired 425 E9) MSDP TLV format error detected 426 E10) Any other error detected 428 14.2. Actions 430 A1) Allocate resources for peering with P 431 Compare one's own and peer's IP addresses 432 A2) TCP active OPEN 433 Set ConnectRetry timer to [ConnectRetry-Period] 434 A3) TCP passive OPEN (listen) 435 A4) Delete ConnectRetry timer 436 Send KeepAlive TLV 437 Set KeepAlive timer to [KeepAlive-Period] 438 Set Hold Timer to [HoldTime-Period] 439 A5) Send KeepAlive TLV 440 Set KeepAlive timer to [KeepAlive-Period] 441 Set Hold Timer to [HoldTime-Period] 442 A6) Abort TCP active OPEN attempt 443 Release resources allocated for peering with P 444 A7) Abort TCP passive OPEN attempt 445 Release resources allocated for peering with P 446 A8) Close the TCP connection 447 Release resources allocated for peering with P 448 A9) Drop the packet 450 14.3. Peer-specific Events 452 The following peer-specific events can occur in the ESTABLISHED 453 state, they do not cause a state transition. Appropriate actions are 454 listed for each event. 456 *) KeepAlive timer expired: 457 -> Send KeepAlive TLV 458 -> Set KeepAlive timer to [KeepAlive-Period] 459 *) KeepAlive TLV received: 460 -> Set Hold Timer to [HoldTime-Period] 461 *) Source-Active TLV received: 462 -> Set Hold Timer to [HoldTime-Period] 463 -> Run Peer-RPF Forwarding algorithm 464 -> Set KeepAlive timer to [KeepAlive-Period] for those peers 465 the Source-Active TLV is forwarded to 466 -> Send information to PIM-SM 467 -> Store information in cache 469 14.4. Peer-independent Events 471 There are also a number of events that affect more than one peering 472 session, but still require actions to be performed on a per-peer 473 basis. 475 *) SA-Advertisement-Timer expired: 476 -> Start periodic transmission of Source-Active TLV(s) 477 -> Set KeepAlive timer to [KeepAlive-Period] each time a 478 Source-Active TLV is sent 479 *) MSDP learns of a new active internal source (e.g. PIM-SM 480 register received for a new source): 481 -> Send Source-Active TLV 482 -> Set KeepAlive timer to [KeepAlive-Period] 483 *) SG-State-Timer expired (one timer per cache entry): 484 -> Implementation specific, typically mark the cache entry for 485 deletion 487 15. Packet Formats 489 MSDP messages will be encoded in TLV format. If an implementation 490 receives a TLV that has length that is longer than expected, the TLV 491 SHOULD be accepted. Any additional data SHOULD be ignored and the 492 MSDP session should not be reset. 494 15.1. MSDP TLV format: 496 0 1 2 3 497 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 1 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 | Type | Length | Value .... | 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 Type (8 bits) 503 Describes the format of the Value field. 505 Length (16 bits) 506 Length of Type, Length, and Value fields in octets. 507 Minimum length required is 4 octets, except for 508 Keepalive messages. The maximum TLV length is 9192. 510 Value (variable length) 511 Format is based on the Type value. See below. The length of 512 the value field is Length field minus 3. All reserved fields 513 in the Value field MUST be transmitted as zeros and ignored on 514 receipt. 516 15.2. Defined TLVs 518 The following TLV Types are defined: 520 Code Type 521 =========================================================== 522 1 IPv4 Source-Active 523 2 IPv4 Source-Active Request 524 3 IPv4 Source-Active Response 525 4 KeepAlive 526 5 Reserved (Previously: Notification) 528 Each TLV is described below. 530 In addition, the following TLV Types are assigned but not described 531 in this memo: 533 Code Type 534 =========================================================== 535 6 MSDP traceroute in progress 536 7 MSDP traceroute reply 538 15.2.1. IPv4 Source-Active TLV 540 The maximum size SA message that can be sent is 9192 octets. The 9192 541 octet size does not include the TCP, IP, layer-2 headers. 543 0 1 2 3 544 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 1 545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 546 | 1 | x + y | Entry Count | 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | RP Address | 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | Reserved | Sprefix Len | \ 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 552 | Group Address | ) z 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 554 | Source Address | / 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 557 Type 558 IPv4 Source-Active TLV is type 1. 560 Length x 561 Is the length of the control information in the message. x is 562 8 octets (for the first two 32-bit quantities) plus 12 times 563 Entry Count octets. 565 Length y 566 If 0, then there is no data encapsulated. Otherwise an IPv4 567 packet follows and y is the length of the total length field 568 of the IPv4 header encapsulated. If there are multiple SA TLVs 569 in a message, and data is also included, y must be 0 in all SA 570 TLVs except the last one and the last SA TLV must reflect the 571 source and destination addresses in the IP header of the 572 encapsulated data. 574 Entry Count 575 Is the count of z entries (note above) which follow the RP 576 address field. This is so multiple (S,G)s from the same domain 577 can be encoded efficiently for the same RP address. An 578 SA message containing encapsulated data typically has an 579 entry count of 1 (i.e. only contains a single entry, for 580 the (S,G) representing the encapsulated packet). 582 RP Address 583 The address of the RP in the domain the source has become 584 active in. 586 Reserved 587 The Reserved field MUST be transmitted as zeros and MUST be 588 ignored by a receiver. 590 Sprefix Len 591 The route prefix length associated with source address. 592 This field MUST be transmitted as 32 (/32). 594 Group Address 595 The group address the active source has sent data to. 597 Source Address 598 The IP address of the active source. 600 Multiple SA TLVs MAY appear in the same message and can be batched 601 for efficiency at the expense of data latency. This would typically 602 occur on intermediate forwarding of SA messages. 604 15.2.2. KeepAlive TLV 606 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 607 MSDP messages sent to the peer within [KeepAlive-Period] seconds. 608 This message is necessary to keep the MSDP connection alive. 610 0 1 2 3 611 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 1 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 | 4 | 3 | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 The length of the message is 3 octets which encompasses the one octet 617 Type field and the two octet Length field. 619 16. MSDP Error Handling 621 If an MSDP SA is received with a TLV format error, the session SHOULD 622 be reset with that peer. All other errors, received from MSDP peers, 623 SHOULD silently discard the packets and the session SHOULD not be 624 reset. 626 17. SA Data Encapsulation 628 As discussed earlier, TCP encapsulation of data in SA messages MAY be 629 supported for backwards compatibility with legacy MSDP peers. 631 18. Security Considerations 633 An MSDP implementation MAY use IPsec [RFC2401] or MD5 to secure control 634 messages. In particular, the TCP connection between MSDP peers MAY 635 be secured using IPsec or MD5. Implementations MUST be capable of 636 working with peers which do not provide IPsec or MD5 security. 638 19. Acknowledgments 640 The editors would like to thank the original authors, Dino Farinacci, 641 Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their 642 orginal contribution to the MSDP specification. In addition, Bill 643 Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, 644 John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina 645 Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning 646 Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided 647 useful and productive design feedback and comments. Mike McBride, 648 Leonard Giuliano, Swapna Yelamanchi and Toerless Eckert worked on the 649 final version of the draft. 651 20. Editors' Address: 653 David Meyer 654 Sprint 655 12502 Sunrise Valley Drive 656 Reston VA, 20191 657 Email: dmm@sprint.net 659 Bill Fenner 660 AT&T Labs -- Research 661 75 Willow Road 662 Menlo Park, CA 94025 663 Email: fenner@research.att.com 665 21. 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 22. Full Copyright Statement 700 Copyright (C) The Internet Society (2001). 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.