idnits 2.17.00 (12 Aug 2021) /tmp/idnits64407/draft-ietf-msdp-spec-10.txt: ** The Abstract section seems to be numbered Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** Looks like you're using RFC 2026 boilerplate. This must be updated to follow RFC 3978/3979, as updated by RFC 4748. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- ** Missing expiration date. 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All references will be assumed normative when checking for downward references. ** There are 17 instances of too long lines in the document, the longest one being 7 characters in excess of 72. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year == Line 745 has weird spacing: '...ndition is d...' == 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 it 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, and so that new receivers who join after a source has been active can get data quickly via a non-caching RP. 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. -- 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: 'SA-Advertisement-Period' is mentioned on line 158, but not defined == Missing Reference: 'SA-State-Period' is mentioned on line 176, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 184, but not defined == Missing Reference: 'HoldTime-Period' is mentioned on line 538, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 731, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 477, but not defined == Missing Reference: 'R2' is mentioned on line 398, but not defined == Missing Reference: 'MSDP-GRE-ProtocolType' is mentioned on line 1070, but not defined -- Possible downref: Non-RFC (?) normative reference: ref. 'IANA' ** Obsolete normative reference: RFC 1771 (Obsoleted by RFC 4271) ** Obsolete normative reference: RFC 2401 (Obsoleted by RFC 4301) ** Downref: Normative reference to an Historic RFC: RFC 1828 ** Obsolete normative reference: RFC 2283 (Obsoleted by RFC 2858) ** Obsolete normative reference: RFC 2362 (Obsoleted by RFC 4601, RFC 5059) Summary: 13 errors (**), 0 flaws (~~), 15 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group David Meyer (Editor) 2 INTERNET DRAFT Bill Fenner (Editor) 3 Category Standards Track 4 May, 2001 6 Multicast Source Discovery Protocol (MSDP) 7 9 1. Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC 2026. 14 Internet Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that other 16 groups may also distribute working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at 24 http://www.ietf.org/ietf/1id-abstracts.txt. 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 2. Abstract 31 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 32 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 33 its own independent RP(s) and does not have to depend on RPs in other 34 domains. 36 3. Copyright Notice 38 Copyright (C) The Internet Society (2001). All Rights Reserved. 40 4. Introduction 42 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 43 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 44 its own independent RP(s) and does not have to depend on RPs in other 45 domains. Advantages of this approach include: 47 o No Third-party resource dependencies on RP 49 PIM-SM domains can rely on their own RPs only. 51 o Receiver only Domains 53 Domains with only receivers get data without globally 54 advertising group membership. 56 Note that MSDP may be used with protocols other than PIM-SM, but such 57 usage is not specified in this memo. 59 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, 60 SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined 61 in RFC 2119 [RFC2119]. 63 5. Overview 65 MSDP-speaking routers in a PIM-SM [RFC2362] domain have a MSDP 66 peering relationship with MSDP peers in another domain. The peering 67 relationship is made up of a TCP connection in which control 68 information is exchanged. Each domain has one or more connections to 69 this virtual topology. 71 The purpose of this topology is to allow domains to discover 72 multicast sources from other domains. If the multicast sources are of 73 interest to a domain which has receivers, the normal source-tree 74 building mechanism in PIM-SM will be used to deliver multicast data 75 over an inter-domain distribution tree. 77 We envision this virtual topology will essentially be congruent to 78 the existing BGP topology used in the unicast-based Internet today. 79 That is, the TCP connections between MSDP peers are likely to be 80 congruent to the connections in the BGP routing system. 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 Each MSDP peer receives and forwards the message away from the RP 94 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 95 flooding is with respect to forwarding SA messages. The Multicast RPF 96 Routing Information Base (MRIB) is examined to determine which peer 97 towards the originating RP of the SA message is selected. Such a peer 98 is called an "RPF peer". See section 14 below for the details of 99 peer-RPF forwarding. 101 If the MSDP peer receives the SA from a non-RPF peer towards the 102 originating RP, it will drop the message. Otherwise, it forwards the 103 message to all its MSDP peers (except the one from which it received 104 the SA message). 106 When an MSDP peer which is also an RP for its own domain receives a 107 new SA message, it determines if it has any group members interested 108 in the group which the SA message describes. That is, the RP checks 109 for a (*,G) entry with a non-empty outgoing interface list; this 110 implies that the domain is interested in the group. In this case, the 111 RP triggers a (S,G) join event towards the data source as if a 112 Join/Prune message was received addressed to the RP itself. This sets 113 up a branch of the source-tree to this domain. Subsequent data 114 packets arrive at the RP which are forwarded down the shared-tree 115 inside the domain. If leaf routers choose to join the source-tree 116 they have the option to do so according to existing PIM-SM 117 conventions. Finally, if an RP in a domain receives a PIM Join 118 message for a new group G, the RP SHOULD trigger a (S,G) join event 119 for each SA for that group in its cache. 121 This procedure has been affectionately named flood-and-join because 122 if any RP is not interested in the group, they can ignore the SA 123 message. Otherwise, they join a distribution tree. 125 7. Caching 127 A MSDP speaker SHOULD cache SA messages. Caching allows pacing of 128 MSDP messages as well as reducing join latency for new receivers of a 129 group G at an originating RP which has existing MSDP (S,G) state. In 130 addition, caching greatly aids in diagnosis and debugging of various 131 problems. 133 8. Timers 135 The main timers for MSDP are: SA-Advertisement-Timer, SA-Hold-Down- 136 Timer, SA Cache Entry timer, KeepAlive timer, ConnectRetry and Peer 137 Hold Timer. Each is considered below. 139 8.1. SA-Advertisement-Timer 141 RPs which originate SA messages do it periodically as long as there 142 is data being sent by the source. There is one SA-Advertisement-Timer 143 covering the sources that an RP may advertise. [SA-Advertisement- 144 Period] MUST be 60 seconds. An RP MUST not send more than one 145 periodic SA message for a given (S,G) within an SA Advertisement 146 interval. Originating periodic SA messages is required to keep 147 announcements alive in caches, and so that new receivers who join 148 after a source has been active can get data quickly via a non-caching 149 RP. Finally, an originating RP SHOULD trigger the transmission of an 150 SA message as soon as it receives data from an internal source for 151 the first time. 153 8.2. SA-Advertisement-Timer Processing 155 An RP MUST spread the generation of periodic SA messages over its 156 reporting interval (i.e. SA-Advertisement-Period). An RP starts the 157 SA-Advertisement-Timer when the MSDP process is configured. When the 158 timer expires, an RP resets the timer to [SA-Advertisement-Period] 159 seconds, and begins the advertisement of its active sources. Active 160 sources are advertised in the following manner: An RP packs its 161 active sources into an SA message until the largest MSDP packet that 162 can be sent is built or there are no more sources, and then sends the 163 message. This process is repeated periodically within the SA- 164 Advertisement-Period in such a way that all of the RP's sources are 165 advertised. Note that the largest MSDP packet that can be sent has 166 size that is the minimum of MTU of outgoing link minus size of TCP 167 and IP headers, and 1400 (largest MSDP packet). Finally, the timer is 168 deleted when the MSDP process is deconfigured. 170 8.3. SA Cache Timeout (SA-State Timer) 172 Each entry in an SA Cache has an associated SA-State Timer. A 173 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 174 received by a MSDP peer. The timer is reset to [SA-State-Period] if 175 another (S,G)-SA message is received before the (S,G)-SA-State Timer 176 expires. [SA-State-Period] MUST NOT be less than 90 seconds. 178 8.4. SA-Hold-Down Timer 180 The per-(S,G) timer is set to [SA-Hold-Down-Period] when forwarding 181 an SA message, and a SA message MUST only be forwarded when its 182 associated timer is not running. [SA-Hold-Down-Period] SHOULD be set 183 to 30 seconds. A MSDP peer MUST NOT forward a (S,G)-SA message it has 184 received in during the previous [SA-Hold-Down-Period] seconds. 185 Finally, the timer is deleted when the SA cache entry is deleted. 187 8.5. Peer Hold Timer 189 If a system has not received any MSDP message within the period 190 specified by the Hold Timer, then a Notification message with Hold 191 Timer Expired Error Code MUST be sent and the MSDP connection MUST be 192 closed. [HoldTime-Period] MUST be at least three seconds. The 193 recommended value for [HoldTime-Period] is 90 seconds. 195 The Hold Timer is initialized to [HoldTime-Period] when the peer's 196 transport connection is established, and is reset to [HoldTime- 197 Period] when any MSDP message is received. Finally, the timer is 198 deleted when the peer's transport connection is closed. 200 8.6. KeepAlive Timer 202 Once an MSDP transport connection is established, each side of the 203 connection sends a KeepAlive message and sets a KeepAlive timer. If 204 the KeepAlive timer expires, the local system sends a KeepAlive 205 message and restarts its KeepAlive timer. 207 The KeepAlive timer is set to [KeepAlive-Period] when the peer comes 208 up. The timer is reset to [KeepAlive-Period] each time an MSDP 209 message is sent to the peer, and reset when the timer expires. 210 Finally, the KeepAlive timer is deleted when the peer's transport 211 connection is closed. 213 [KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be 214 at least one second. The recommended value for [KeepAlive-Period] is 215 75 seconds. 217 8.7. ConnectRetry Timer 219 The ConnectRetry timer is used by an MSDP peer to transition from 220 INACTIVE to CONNECTING states. There is one timer per peer, and the 221 [ConnectRetry-Period] SHOULD be set to 30 seconds. The timer is 222 initialized to [ConnectRetry-Period] when an MSDP speaker attempts to 223 actively open a TCP connection to its peer (see section 15, event E2, 224 action A2 ). When the timer expires, the peer retries the connection 225 and the timer is reset to [ConnectRetry-Period]. It is deleted if 226 either the connection transitions into ESTABLISHED state or the peer 227 is deconfigured. 229 9. Intermediate MSDP Peers 231 Intermediate MSDP speakers do not originate periodic SA messages on 232 behalf of sources in other domains. In general, an RP MUST only 233 originate an SA for a source which would register to it, and ONLY RPs 234 may originate SA messages. 236 10. SA Filtering and Policy 238 As the number of (S,G) pairs increases in the Internet, an RP may 239 want to filter which sources it describes in SA messages. Also, 240 filtering may be used as a matter of policy which at the same time 241 can reduce state. Only the RP co-located in the same domain as the 242 source can restrict SA messages. Note, however, that MSDP peers in 243 transit domains should not filter SA messages or the flood-and-join 244 model can not guarantee that sources will be known throughout the 245 Internet (i.e., SA filtering by transit domains can cause undesired 246 lack of connectivity). In general, policy should be expressed using 247 MBGP [RFC2283]. This will cause MSDP messages to flow in the desired 248 direction and peer-RPF fail otherwise. An exception occurs at an 249 administrative scope [RFC2365] boundary. In particular, a SA message 250 for a (S,G) MUST NOT be sent to peers which are on the other side of 251 an administrative scope boundary for G. 253 11. SA Requests 255 A MSDP speaker MAY accept SA-Requests from other MSDP peers. When an 256 MSDP speaker receives an SA-Request for a group range, it will 257 respond to the peer with a set of SA entries, in an SA-Response 258 message, for all active sources in its SA cache sending to the group 259 requested in the SA-Request message. The peer that sends the request 260 will not flood the responding SA-Response message to other peers. See 261 section 17 for discussion of error handling relating to SA requests 262 and responses. 264 12. Encapsulated Data Packets 266 The RP may encapsulate multicast data from the source. An interested 267 RP may decapsulate the packet, which SHOULD be forwarded as if a PIM 268 register encapsulated packet was received. That is, if packets are 269 already arriving over the interface toward the source, then the 270 packet is dropped. Otherwise, if the outgoing interface list is non- 271 null, the packet is forwarded appropriately. Note that when doing 272 data encapsulation, an implementation MUST bound the time during 273 which packets are encapsulated. 275 This allows for small bursts to be received before the multicast tree 276 is built back toward the source's domain. For example, an 277 implementation SHOULD encapsulate at least the first packet to 278 provide service to bursty sources. 280 13. Other Scenarios 282 MSDP is not limited to deployment across different routing domains. 283 It can be used within a routing domain when it is desired to deploy 284 multiple RPs for the same group ranges. As long as all RPs have a 285 interconnected MSDP topology, each can learn about active sources as 286 well as RPs in other domains. 288 14. MSDP Peer-RPF Forwarding 290 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 291 messages throughout an MSDP enabled internet. Unlike the RPF check 292 used when forwarding data packets, the Peer-RPF check is against the 293 RP address carried in the SA message. 295 14.1. Definitions 297 The following definitions are used in the description of the Peer-RPF 298 Forwarding Rules: 300 14.1.1. Multicast RPF Routing Information Base (MRIB) 302 The MRIB is the multicast topology table. It is typically derived 303 from the unicast routing table or from other routing protocols such 304 as multi-protocol BGP [RFC2283]. 306 14.1.2. RPF Route 308 The RPF route is the route that the MRIB chooses for a given address. 309 The RPF route for a SA's originating RP is used to select the peer 310 from which the SA is accepted. 312 14.2. Peer-RPF Forwarding Rules 314 An SA message originated by R and received by X from N is 315 accepted if N is the peer-RPF neighbor for X, and is discarded 316 otherwise. 318 MPP(R,N) MP(N,X) 319 R ---------....-------> N ------------------> X 320 SA(S,G,R) SA(S,G,R) 322 Where MPP(R,N) is an MSDP peering path (zero or more MSDP 323 peers) between R and N. SA(S,G,R) is an SA message for source 324 S on group G originated by an RP R. MP(N,X) is an MSDP 325 peering between N and X. 327 The peer-RPF neighbor is chosen deterministically, using the 328 first of the following rules that matches. In particular, 329 N is the RPF neighbor of X with respect to R if 331 (i). N == R (X has an MSDP peering with R). 333 (ii). N is the BGP NEXT_HOP of the active RPF route 334 for R. 336 (iii). The active RPF route for R is learned through a 337 distance-vector or path-vector routing protocol 338 (e.g. BGP, RIP, DVMRP) and N is the neighbor that 339 advertised the active RPF route for R. 341 (iv). N resides in an AS that is in the AS_PATH of the active 342 RPF route for R, and N has the highest IP address among 343 the MSDP peers that reside in ASs in that AS_PATH. 345 (v). N is configured as the static RPF-peer for R. 347 14.3. MSDP static RPF-peer semantics 349 If none of the rules (i) - (iv) are able to determine an RPF peer for 350 R, a longest-match lookup is performed in the static RPF peer table. 351 This table MUST be able to contain a default entry, and SHOULD be 352 able to contain prefix or per-host (RP) entries. This table 353 statically maps RP addresses to peers, and allows configuration of 354 topology that is e.g. unknown to the MRIB. 356 The result of the longest-match lookup of an RP address R in the 357 static RPF peer table is an MSDP peer, which is the RPF neighbor for 358 R. 360 14.4. MSDP mesh-group semantics 362 A MSDP mesh-group is a operational mechanism for reducing SA 363 flooding, typically in an intra-domain setting. In particular, when 364 some subset of a domain's MSDP speakers are fully meshed, then can be 365 configured into a mesh-group. 367 Note that mesh-groups assume that a member doesn't have to forward an 368 SA to other members of the mesh-group because the originator will 369 forward to all members. To be able for the originator to forward to 370 all members (and to have each member also be a potential originator), 371 the mesh-group must be a full mesh of MSDP peering among all members. 373 The semantics of the mesh-group are as follows: 375 (i). If a member R of a mesh-group M receives a SA message from an 376 MSDP peer that is also a member of mesh-group M, R accepts the 377 SA message and forwards it to all of its peers that are not 378 part of any mesh-group. R MUST NOT forward the SA message to 379 other members of mesh-group M. 381 (ii). If a member R of a mesh-group M receives a SA message from an 382 MSDP peer that is not a member of mesh-group M, and the SA 383 message passes the peer-RPF check, then R forwards the SA 384 message to all members of mesh-group M. 386 (iii). Cross mesh-group forwarding 388 If a member R of a mesh-groups M and N receives an SA 389 message from an MSDP peer in mesh-group M, R forwards the SA 390 to its MSDP peers in mesh-group N if it receives that SA 391 message from a peer that is in the same mesh-group as its 392 peer-RPF neighbor for that SA. 394 For example, consider the case in which three routers (R1, R2, 395 and R3) and three mesh-groups (A, B, and C) are arranged in a 396 triangle, e.g., 398 [R2] {A,B} 399 / \ 400 / \ 401 / \ 402 / \ 403 {A,C} [R1]--------[R3] {B,C} 405 Now, when R1 receives an SA message from R2 and R1's 406 peer-RPF neighbor for this SA lies in mesh-group A, R1 407 forwards the SA message its peers in other mesh-groups 408 (in particular, R3 in mesh-group C). Similarly, if R3's 409 peer-RPF neighbor lies in mesh-group B, R3 will forward an 410 SA message from R2. In this case, both R1 and R3 will send 411 SA messages to each other (because they share common mesh-group 412 C), but neither of them will forward any further the SA messages 413 received from each other (as their peer-RPF neighbors do 414 not lie in mesh-group C). 416 Note that since mesh-groups suspend peer-RPF checking of SAs received 417 from a mesh-group member ((i). above), they allow for mis- 418 configuration to cause SA looping. 420 15. MSDP Connection State Machine 422 MSDP uses TCP as its transport protocol. In a peering relationship, 423 one MSDP peer listens for new TCP connections on the well-known port 424 639. The other side makes an active connect to this port. The peer 425 with the higher IP address will listen. This connection establishment 426 algorithm avoids call collision. Therefore, there is no need for a 427 call collision procedure. It should be noted, however, that the 428 disadvantage of this approach is that it may result in longer startup 429 times at the passive side. 431 An MSDP peer starts in the DISABLED state. MSDP peers establish 432 peering sessions according to the following state machine: 434 --------------->+----------+ 435 / | DISABLED |<---------- 436 | ------>+----------+ \ 437 | / |E1->A1 | 438 | | | | 439 | | V |E7->A7 440 | | +----------+ E3->A3 +--------+ 441 | | | INACTIVE |------->| LISTEN | 442 | | +----------+ +--------+ 443 | | E2->A2| ^ |E5->A5 444 | | | | | 445 | |E7->A6 V |E6 | 446 | \ +------------+ | 447 E7->A8 | ------| CONNECTING | | 448 E8->A9 | +------------+ | 449 E9->A10| |E4->A4 | 450 E10->A11| | | 451 E11->A12| V | 452 \ +-------------+ / 453 --------------| ESTABLISHED |<--------- 454 +-------------+ 456 15.1. Events 458 E1) Enable MSDP peering with P 459 E2) Own IP address < P's IP address 460 E3) Own IP address > P's IP address 461 E4) TCP established (active side) 462 E5) TCP established (passive side) 463 E6) ConnectRetry timer expired 464 E7) Disable MSDP peering with P 465 An example of when to do this is when one's own address is 466 changed) 467 E8) Hold Timer expired 468 E9) Authorization failure 469 E10) Notification TLV received 470 E11) Error detected 472 15.2. Actions 474 A1) Allocate resources for peering with P 475 Compare one's own and peer's IP addresses 476 A2) TCP active OPEN 477 Set ConnectRetry timer to [ConnectRetry-Period] 478 A3) TCP passive OPEN (listen) 479 A4) Delete ConnectRetry timer 480 Send KeepAlive TLV 481 Set KeepAlive timer to [KeepAlive-Period] 482 Set Hold Timer to [HoldTime-Period] 483 A5) Send KeepAlive TLV 484 Set KeepAlive timer to [KeepAlive-Period] 485 Set Hold Timer to [HoldTime-Period] 486 A6) Abort TCP active OPEN attempt 487 Release resources allocated for peering with P 488 A7) Abort TCP passive OPEN attempt 489 Release resources allocated for peering with P 491 In action sets 8)-12), the action "Close peering session" includes 492 the following steps: 493 Close TCP connection 494 Delete KeepAlive timer 495 Delete Hold Timer 496 Release resources allocated for peering with P 498 A8) Send Notification TLV with Error Code "Cease" 499 Close peering session 500 A9) Send Notification TLV with Error Code "Hold Timer Expired" 501 Close peering session 503 A10) Notify management system unless this has already been done by 504 the security mechanism 505 Close peering session 506 A11) Notify management system 507 If the received Notification TLV's O-bit was cleared, close 508 peering session. Otherwise, remain in ESTABLISHED state. 509 A12) Send Notification TLV with appropriate Error Code 510 Notify management system 511 If the sent Notification TLV's O-bit was cleared, close peering 512 session. Otherwise, remain in ESTABLISHED state. 514 15.3. Peer-specific Events 516 The following peer-specific events can occur in the ESTABLISHED 517 state, they do not cause a state transition. Appropriate actions are 518 listed for each event. 520 *) KeepAlive timer expired: 521 -> Send KeepAlive TLV 522 -> Set KeepAlive timer to [KeepAlive-Period] 523 *) KeepAlive TLV received: 524 -> Set Hold Timer to [HoldTime-Period] 525 *) Source-Active TLV received: 526 -> Set Hold Timer to [HoldTime-Period] 527 -> Run Peer-RPF Forwarding algorithm (if caching, consider 528 SA-Hold-Down Timer and SA-State Timer) 529 -> Set KeepAlive timer to [KeepAlive-Period] for those peers the 530 Source-Active TLV is forwarded to 531 -> Send information to PIM-SM 532 -> If caching, store information 533 *) Source-Active Request TLV received: 534 -> Set Hold Timer to [HoldTime-Period] 535 -> If SA-Requests are accepted, send Source-Active Response TLV 536 and set KeepAlive timer to [KeepAlive-Period] 537 *) Source-Active Response TLV received: 538 -> Set Hold Timer to [HoldTime-Period] 539 -> If a corresponding SA-Request were previously sent, send 540 information to PIM-SM. If not, an error has occured (event 11 541 above) 542 -> If caching, store information 544 15.4. Peer-independent Events 546 There are also a number of events that affect more than one peering 547 session, but still require actions to be performed on a per-peer 548 basis. If the MSDP speaker does not cache SA messages, ignore all 549 events and actions pertaining to caching. 551 *) SA-Advertisement-Timer expired: 552 -> Start periodic transmission of Source-Active TLV(s) 553 -> Set KeepAlive timer to [KeepAlive-Period] each time a 554 Source-Active TLV is sent 555 *) MSDP learns of a new active internal source (e.g. PIM-SM 556 register received for a new source): 557 -> Send Source-Active TLV 558 -> Set KeepAlive timer to [KeepAlive-Period] 559 *) Source-Active Request triggered (event not specified here): 560 -> Send Source-Active Request TLV 561 -> Set KeepAlive timer to [KeepAlive-Period] 562 *) SA-State-Timer expired (one timer per cache entry): 563 -> Implementation specific, typically mark the cache entry for 564 deletion 566 16. Packet Formats 568 MSDP messages will be encoded in TLV format. If an implementation 569 receives a TLV that has length that is longer than expected, the TLV 570 SHOULD be accepted. Any additional data SHOULD be ignored. 572 16.1. MSDP TLV format: 574 0 1 2 3 575 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 1 576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 | Type | Length | Value .... | 578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 580 Type (8 bits) 581 Describes the format of the Value field. 583 Length (16 bits) 584 Length of Type, Length, and Value fields in octets. 585 minimum length required is 4 octets, except for 586 Keepalive messages. The maximum TLV length is 1400. 588 Value (variable length) 589 Format is based on the Type value. See below. The length of 590 the value field is Length field minus 3. All reserved fields 591 in the Value field MUST be transmitted as zeros and ignored on 592 receipt. 594 16.2. Defined TLVs 596 The following TLV Types are defined: 598 Code Type 599 =========================================================== 600 1 IPv4 Source-Active 601 2 IPv4 Source-Active Request 602 3 IPv4 Source-Active Response 603 4 KeepAlive 604 5 Notification 606 Each TLV is described below. 608 In addition, the following TLV Types are assigned but not described 609 in this memo: 611 Code Type 612 =========================================================== 613 6 MSDP traceroute in progress 614 7 MSDP traceroute reply 616 16.2.1. IPv4 Source-Active TLV 618 The maximum size SA message that can be sent is 1400 octets. If an 619 MSDP peer needs to originate a message with information greater than 620 1400 octets, it sends successive 1400 octet or smaller messages. The 621 1400 octet size does not include the TCP, IP, layer-2 headers. 623 0 1 2 3 624 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 1 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 | 1 | x + y | Entry Count | 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 628 | RP Address | 629 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 | Reserved | Sprefix Len | \ 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 632 | Group Address | ) z 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 634 | Source Address | / 635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 Type 638 IPv4 Source-Active TLV is type 1. 640 Length x 641 Is the length of the control information in the message. x is 642 8 octets (for the first two 32-bit quantities) plus 12 times 643 Entry Count octets. 645 Length y 646 If 0, then there is no data encapsulated. Otherwise an IPv4 647 packet follows and y is the length of the total length field 648 of the IPv4 header encapsulated. If there are multiple SA TLVs 649 in a message, and data is also included, y must be 0 in all SA 650 TLVs except the last one and the last SA TLV must reflect the 651 source and destination addresses in the IP header of the 652 encapsulated data. 654 Entry Count 655 Is the count of z entries (note above) which follow the RP 656 address field. This is so multiple (S,G)s from the same domain 657 can be encoded efficiently for the same RP address. 659 RP Address 660 The address of the RP in the domain the source has become 661 active in. 663 Reserved 664 The Reserved field MUST be transmitted as zeros and MUST be 665 ignored by a receiver. 667 Sprefix Len 668 The route prefix length associated with source address. 669 This field MUST be transmitted as 32 (/32). An Invalid 670 Sprefix Len Notification SHOULD be sent upon receipt 671 of any other value. 673 Group Address 674 The group address the active source has sent data to. 676 Source Address 677 The IP address of the active source. 679 Multiple SA TLVs MAY appear in the same message and can be batched 680 for efficiency at the expense of data latency. This would typically 681 occur on intermediate forwarding of SA messages. 683 16.2.2. IPv4 Source-Active Request TLV 685 The Source-Active Request is used to request SA-state from a MSDP 686 peer. If an RP in a domain receives a PIM Join message for a group, 687 creates (*,G) state and wants to know all active sources for group G, 688 it may send an SA-Request message for the group. 690 0 1 2 3 691 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 1 692 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 693 | 2 | 8 | Reserved | 694 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 | Group Address | 696 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 698 Type 699 IPv4 Source-Active Request TLV is type 2. 701 Reserved 702 Must be transmitted as zero and ignored on receipt. 704 Group Address 705 The group address the MSDP peer is requesting. 707 16.2.3. IPv4 Source-Active Response TLV 709 The Source-Active Response is sent in response to a Source-Active 710 Request message. The Source-Active Response message has the same 711 format as a Source-Active message but does not allow encapsulation of 712 multicast data. 714 0 1 2 3 715 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 1 716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 | 3 | x | .... | 718 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 720 Type 721 IPv4 Source-Active Response TLV is type 3. 723 Length x 724 Is the length of the control information in the message. x is 8 725 octets (for the first two 32-bit quantities) plus 12 times Entry 726 Count octets. 728 16.2.4. KeepAlive TLV 730 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 731 MSDP messages sent to the peer within [KeepAlive-Period] seconds. 732 This message is necessary to keep the MSDP connection alive. 734 0 1 2 3 735 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 1 736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 737 | 4 | 3 | 738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 740 The length of the message is 3 octets which encompasses the one octet 741 Type field and the two octet Length field. 743 16.2.5. Notification TLV 745 A Notification message is sent when an error condition is detected, 746 and has the following form: 748 0 1 2 3 749 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 1 750 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 751 | 5 | x + 5 |O| Error Code | 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 | Error subcode | ... | 754 +-+-+-+-+-+-+-+-+ | 755 | Data | 756 | ... | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 759 Type 760 The Notification TLV is type 5. 762 Length 763 Length is a two octet field with value x + 5, where x is 764 the length of the notification data field. 766 O-bit 767 Open-bit. If clear, the connection will be closed. 769 Error code 770 This 7-bit unsigned integer indicates the type of Notification. 771 The following Error Codes have been defined: 773 Error Code Symbolic Name Reference 775 1 Message Header Error Section 17.1 776 2 SA-Request Error Section 17.2 777 3 SA-Message/SA-Response Error Section 17.3 778 4 Hold Timer Expired Section 17.4 779 5 Finite State Machine Error Section 17.5 780 6 Notification Section 17.6 781 7 Cease Section 17.7 783 Error subcode: 784 This one-octet unsigned integer provides more specific information 785 about the reported error. Each Error Code may have one or more 786 Error 787 Subcodes associated with it. If no appropriate Error Subcode is 788 defined, then a zero (Unspecific) value is used for the Error 789 Subcode 790 field, and the O-bit must be cleared (i.e. the connection will be 791 closed). The used notation in the error description below is: MC = 792 Must Close connection = O-bit clear; CC = Can Close connection = 793 O-bit MAY be cleared. 795 Message Header Error subcodes: 797 0 - Unspecific (MC) 798 2 - Bad Message Length (MC) 799 3 - Bad Message Type (CC) 801 SA-Request Error subcodes (the O-bit is always clear): 803 0 - Unspecific (MC) 804 1 - Invalid Group (MC) 806 SA-Message/SA-Response Error subcodes 808 0 - Unspecific (MC) 809 1 - Invalid Entry Count (CC) 810 2 - Invalid RP Address (MC) 811 3 - Invalid Group Address (MC) 812 4 - Invalid Source Address (MC) 813 5 - Invalid Sprefix Length (MC) 814 6 - Looping SA (Self is RP) (MC) 815 7 - Unknown Encapsulation (MC) 816 8 - Administrative Scope Boundary Violated (MC) 818 Hold Timer Expired subcodes (the O-bit is always clear): 820 0 - Unspecific (MC) 822 Finite State Machine Error subcodes (the O-bit is always clear): 824 0 - Unspecific (MC) 825 1 - Unexpected Message Type FSM Error (MC) 827 Notification subcodes (the O-bit is always clear): 829 0 - Unspecific (MC) 831 Cease subcodes (the O-bit is always clear): 833 0 - Unspecific (MC) 835 17. MSDP Error Handling 837 This section describes actions to be taken when errors are detected 838 while processing MSDP messages. MSDP Error Handling is similar to 839 that of BGP [RFC1771]. 841 When any of the conditions described here are detected, a 842 Notification message with the indicated Error Code, Error Subcode, 843 and Data fields is sent. In addition, the MSDP connection MAY be 844 closed. If no Error Subcode is specified, then a zero (Unspecific) 845 must be used. 847 The phrase "the MSDP connection is closed" means that the transport 848 protocol connection has been closed and that all resources for that 849 MSDP connection have been deallocated. 851 17.1. Message Header Error Handling 853 All errors detected while processing the Message Header are indicated 854 by sending the Notification message with Error Code Message Header 855 Error. The Error Subcode describes the specific nature of the error. 856 The Data field contains the erroneous Message (including the message 857 header). 859 If the Length field of the message header is less than 4 or greater 860 than 1400, or the length of a KeepAlive message is not equal to 3, 861 then the Error Subcode is set to Bad Message Length. 863 If the Type field of the message header is not recognized, then the 864 Error Subcode is set to Bad Message Type. 866 17.2. SA-Request Error Handling 868 The SA-Request Error code is used to signal the receipt of a SA 869 request at a MSDP peer when an invalid group address requested. 871 When a MSDP peer receives a request for an invalid group, it returns 872 the following notification: 874 0 1 2 3 875 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 1 876 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 877 | 5 | 12 |O| 2 | 878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 879 | 2 | Reserved | 880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 881 | Group Address | 882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 884 17.3. SA-Message/SA-Response Error Handling 886 The SA-Message/SA-Response Error code is used to signal the receipt 887 of a erroneous SA Message at an MSDP peer, or the receipt of an SA- 888 Response Message by a peer that did not issue a SA-Request. It has 889 the following form: 891 17.3.1. Invalid Entry Count (IEC) 893 0 1 2 3 894 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 1 895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 896 | 5 | 6 |O| 3 | 897 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 898 | 1 | Entry Count | 899 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 901 17.3.2. Invalid RP Address 903 0 1 2 3 904 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 1 905 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 906 | 5 | 12 |O| 3 | 907 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 908 | 2 | Reserved | 909 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 910 | RP Address | 911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 913 17.3.3. Invalid Group Address 915 0 1 2 3 916 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 1 917 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 918 | 5 | 12 |O| 3 | 919 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 920 | 3 | Reserved | 921 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 922 | Group Address | 923 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 925 17.3.4. Invalid Source Address 927 0 1 2 3 928 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 1 929 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 930 | 5 | 12 |O| 3 | 931 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 932 | 4 | Reserved | 933 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 934 | Source Address | 935 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 937 17.3.5. Invalid Sprefix Length (ISL) 939 0 1 2 3 940 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 1 941 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 942 | 5 | 6 |O| 3 | 943 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 944 | 5 | Sprefix Len | 945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 947 17.3.6. Looping SAs (Self is RP in received SA) 949 0 1 2 3 950 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 1 951 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 952 | 5 | x + 5 |O| 3 | 953 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 954 | 6 | SA Message .... 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 958 Length x 959 x is the length of the looping SA message contained in the data 960 field of the Notification message. 962 17.3.7. Unknown Encapsulation 964 This notification is sent on receipt of SA data that is encapsulated 965 in an unknown encapsulation type. See section 18 for known 966 encapsulations. 968 0 1 2 3 969 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 1 970 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 971 | 5 | x + 5 |O| 3 | 972 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 973 | 7 | SA Message .... 974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 976 Length x 977 x is the length of the SA message (which contained data which 978 was encapsulated in some unknown way) that is contained in the 979 data field of the Notification message. 981 17.3.8. Administrative Scope Boundary Violated 983 This notification is used when an SA message is received for a group 984 G from a peer which is across an administrative scope boundary for G. 986 0 1 2 3 987 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 1 988 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 989 | 5 | 12 |O| 3 | 990 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 991 | 8 | Reserved | 992 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 993 | Group Address | 994 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 996 17.4. Hold Time Expired 998 If a system has not received any MSDP message within the period 999 specified in the Hold Timer, the notification message with Hold Timer 1000 Expired Error Code and no additional data MUST be sent and the MSDP 1001 connection closed. 1003 17.5. Finite State Machine Error Handling 1005 Any error detected by the MSDP Finite State Machine (e.g., receipt of 1006 an unexpected event) is indicated by sending the Notification message 1007 with Error Code Finite State Machine Error. 1009 17.6. Notification Message Error Handling 1011 If a node sends a Notification message, and there is an error in that 1012 message, and the O-bit of that message is not clear, a Notification 1013 with O-bit clear, Error Code of Notification Error, and subcode 1014 Unspecific must be sent. In addition, the Data field must include 1015 the Notification message that triggered the error. However, if the 1016 erroneous Notification message had the O-bit clear, then any error, 1017 such as an unrecognized Error Code or Error Subcode, should be 1018 noticed, logged locally, and brought to the attention of the 1019 administrator of the remote node. 1021 17.7. Cease 1023 In absence of any fatal errors (that are indicated in this section), 1024 an MSDP node may choose at any given time to close its MSDP 1025 connection by sending the Notification message with Error Code Cease. 1026 However, the Cease Notification message MUST NOT be used when a fatal 1027 error indicated by this section does exist. 1029 18. SA Data Encapsulation 1031 This section describes UDP, GRE, and TCP encapsulation of data 1032 packets to be included with SA messages. Encapsulation type is a 1033 configuration option. 1035 18.1. UDP Data Encapsulation 1037 Data packets MAY be encapsulated in UDP. In this case, the UDP 1038 pseudo-header has the following form: 1040 0 1 2 3 1041 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 1042 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1043 | Source Port | Destination Port | 1044 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1045 | Length | Checksum | 1046 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1047 | Origin RP Address | 1048 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1050 The Source port, Destination Port, Length, and Checksum are used 1051 according to RFC 768. Source and Destination ports are known via an 1052 implementation-specific method (e.g. per-peer configuration). 1054 Checksum 1055 The checksum is computed according to RFC 768 [RFC768]. 1057 Originating RP Address 1058 The Originating RP Address is the address of the RP sending 1059 the encapsulated data. 1061 18.2. GRE Encapsulation 1063 MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP- 1064 GRE-ProtocolType]. The GRE header and payload packet have the 1065 following form: 1067 0 1 2 3 1068 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 1069 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1070 |C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\ 1071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header 1072 | Checksum (optional) | Reserved1 |/ 1073 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1074 | Originating RP IPv4 Address |\ 1075 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload 1076 | (S,G) Data Packet .... / 1077 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1079 18.2.1. Encapsulation and Path MTU Discovery [RFC1191] 1081 Existing implementations of GRE, when using IPv4 as the Delivery 1082 Header, do not implement Path MTU discovery and do not set the Don't 1083 Fragment bit in the Delivery Header. This can cause large packets to 1084 become fragmented within the tunnel and reassembled at the tunnel 1085 exit (independent of whether the payload packet is using PMTU). If a 1086 tunnel entry point were to use Path MTU discovery, however, that 1087 tunnel entry point would also need to relay ICMP unreachable error 1088 messages (in particular the "fragmentation needed and DF set" code) 1089 back to the originator of the packet, which is not required by the 1090 GRE specification [RFC2784]. Failure to properly relay Path MTU 1091 information to an originator can result in the following behavior: 1092 the originator sets the don't fragment bit, the packet gets dropped 1093 within the tunnel, but since the originator doesn't receive proper 1094 feedback, it retransmits with the same PMTU, causing subsequently 1095 transmitted packets to be dropped. 1097 18.3. TCP Data Encapsulation 1099 As discussed earlier, encapsulation of data in SA messages MAY be 1100 supported for backwards compatibility with legacy MSDP peers. 1102 19. IANA Considerations 1104 The IANA should assign 0x0009 from the IANA SNAP Protocol IDs [IANA] 1105 to MSDP-GRE-ProtocolType. 1107 20. Security Considerations 1109 An MSDP implementation MAY use IPsec [RFC2401] or keyed MD5 [RFC1828] 1110 to secure control messages. When encapsulating data packets in GRE, 1111 security should be relatively similar to security in a normal IPv4 1112 network, as routing using GRE follows the same routing that IPv4 uses 1113 natively. Route filtering will remain unchanged. However packet 1114 filtering at a firewall requires either that a firewall look inside 1115 the GRE packet or that the filtering is done on the GRE tunnel 1116 endpoints. In those environments in which this is considered to be a 1117 security issue it may be desirable to terminate the tunnel at the 1118 firewall. 1120 21. Acknowledgments 1122 The editors would like to thank the original authors, Dino Farinacci, 1123 Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their 1124 orginal contribution to the MSDP specification. In addition, Bill 1125 Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, 1126 John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina 1127 Priestley and IJsbrand Wijnands provided useful and productive design 1128 feedback and comments. In addition to many other contributions, Tom 1129 Pusateri, Kristofer.Warell, Henning Eriksson, and Thomas Eriksson 1130 helped to clarify the connection state machine, Dave Thaler helped to 1131 clarify the Notification message types. Ravi Shekhar helped clarify 1132 the semantics of mesh-groups, and countless others helped to clarify 1133 the Peer-RPF rules. 1135 22. Editors' Address: 1137 David Meyer 1138 Cisco Systems, Inc. 1139 170 Tasman Drive 1140 San Jose, CA, 95134 1141 Email: dmm@cisco.com 1143 Bill Fenner 1144 AT&T Labs -- Research 1145 75 Willow Road 1146 Menlo Park, CA 94025 1147 Email: fenner@research.att.com 1149 23. REFERENCES 1151 [IANA] www.iana.org 1153 [RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation 1154 (GRE)", RFC 2784, March 2000. 1156 [RFC768] Postel, J. "User Datagram Protocol", RFC 768, August, 1157 1980. 1159 [RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery", 1160 RFC 1191, November 1990. 1162 [RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 1163 (BGP-4)", RFC 1771, March 1995. 1165 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for 1166 the Internet Protocol", RFC 2401, November 1998. 1168 [RFC1828] P. Metzger and W. Simpson, "IP Authentication using 1169 Keyed MD5", RFC 1828, August, 1995. 1171 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 1172 Requirement Levels", RFC 2119, March, 1997. 1174 [RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., 1175 "Multiprotocol Extensions for BGP-4", RFC 2283, 1176 February 1998. 1178 [RFC2362] Estrin D., et al., "Protocol Independent Multicast - 1179 Sparse Mode (PIM-SM): Protocol Specification", RFC 1180 2362, June 1998. 1182 [RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC 1183 2365, July, 1998. 1185 24. Full Copyright Statement 1187 Copyright (C) The Internet Society (2001). All Rights Reserved. 1189 This document and translations of it may be copied and furnished to 1190 others, and derivative works that comment on or otherwise explain it 1191 or assist in its implementation may be prepared, copied, published 1192 and distributed, in whole or in part, without restriction of any 1193 kind, provided that the above copyright notice and this paragraph are 1194 included on all such copies and derivative works. However, this 1195 document itself may not be modified in any way, such as by removing 1196 the copyright notice or references to the Internet Society or other 1197 Internet organizations, except as needed for the purpose of 1198 developing Internet standards in which case the procedures for 1199 copyrights defined in the Internet Standards process must be 1200 followed, or as required to translate it into languages other than 1201 English. 1203 The limited permissions granted above are perpetual and will not be 1204 revoked by the Internet Society or its successors or assigns. 1206 This document and the information contained herein is provided on an 1207 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 1208 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 1209 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 1210 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 1211 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.