idnits 2.17.00 (12 Aug 2021) /tmp/idnits3441/draft-ietf-msdp-spec-12.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. The document expiration date should appear on the first and last page. ** The document seems to lack a 1id_guidelines paragraph about Internet-Drafts being working documents. ** The document is more than 15 pages and seems to lack a Table of Contents. == No 'Intended status' indicated for this document; assuming Proposed Standard == The page length should not exceed 58 lines per page, but there was 32 longer pages, the longest (page 2) being 60 lines == It seems as if not all pages are separated by form feeds - found 0 form feeds but 33 pages Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an Introduction section. ** The document seems to lack separate sections for Informative/Normative References. 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 == 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 180 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. -- 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 159, but not defined == Missing Reference: 'SA-State-Period' is mentioned on line 177, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 188, but not defined == Missing Reference: 'HoldTime-Period' is mentioned on line 546, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 736, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 485, but not defined == Missing Reference: 'R2' is mentioned on line 406, but not defined == Missing Reference: 'MSDP-GRE-ProtocolType' is mentioned on line 1072, but not defined -- 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: 12 errors (**), 0 flaws (~~), 14 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 September, 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 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. 96 Each MSDP peer receives and forwards the message away from the RP 97 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 98 flooding is with respect to forwarding SA messages. The Multicast RPF 99 Routing Information Base (MRIB) is examined to determine which peer 100 towards the originating RP of the SA message is selected. Such a peer 101 is called an "RPF peer". See section 14 for the details of peer-RPF 102 forwarding. 104 If the MSDP peer receives the SA from a non-RPF peer towards the 105 originating RP, it will drop the message. Otherwise, it forwards the 106 message to all its MSDP peers (except the one from which it received 107 the SA message). 109 When an MSDP peer which is also an RP for its own domain receives a 110 new SA message, it determines if it has any group members interested 111 in the group which the SA message describes. That is, the RP checks 112 for a (*,G) entry with a non-empty outgoing interface list; this 113 implies that the domain is interested in the group. In this case, the 114 RP triggers a (S,G) join event towards the data source as if a 115 Join/Prune message was received addressed to the RP itself. This sets 116 up a branch of the source-tree to this domain. Subsequent data 117 packets arrive at the RP which are forwarded down the shared-tree 118 inside the domain. If leaf routers choose to join the source-tree 119 they have the option to do so according to existing PIM-SM 120 conventions. Finally, if an RP in a domain receives a PIM Join 121 message for a new group G, the RP SHOULD trigger a (S,G) join event 122 for each SA for that group in its cache. 124 This procedure has been affectionately named flood-and-join because 125 if any RP is not interested in the group, they can ignore the SA 126 message. Otherwise, they join a distribution tree. 128 7. Caching 130 A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP 131 messages as well as reducing join latency for new receivers of a 132 group G at an originating RP which has existing MSDP (S,G) state. In 133 addition, caching greatly aids in diagnosis and debugging of various 134 problems. 136 8. Timers 138 The main timers for MSDP are: SA-Advertisement-Timer, SA-Hold-Down- 139 Timer, SA Cache Entry timer, KeepAlive timer, ConnectRetry and Peer 140 Hold Timer. Each is considered below. 142 8.1. SA-Advertisement-Timer 144 RPs which originate SA messages do so periodically as long as there 145 is data being sent by the source. There is one SA-Advertisement-Timer 146 covering the sources that an RP may advertise. [SA-Advertisement- 147 Period] MUST be 180 seconds. An RP MUST not send more than one 148 periodic SA message for a given (S,G) within an SA Advertisement 149 interval. Originating periodic SA messages is required to keep 150 announcements alive in caches. Finally, an originating RP SHOULD 151 trigger the transmission of an SA message as soon as it receives data 152 from an internal source for the first time. 154 8.2. SA-Advertisement-Timer Processing 156 An RP MUST spread the generation of periodic SA messages over its 157 reporting interval (i.e. SA-Advertisement-Period). An RP starts the 158 SA-Advertisement-Timer when the MSDP process is configured. When the 159 timer expires, an RP resets the timer to [SA-Advertisement-Period] 160 seconds, and begins the advertisement of its active sources. Active 161 sources are advertised in the following manner: An RP packs its 162 active sources into an SA message until the largest MSDP packet that 163 can be sent is built or there are no more sources, and then sends the 164 message. This process is repeated periodically within the SA- 165 Advertisement-Period in such a way that all of the RP's sources are 166 advertised. Note that since MSDP is a periodic protocol, an 167 implemenation SHOULD send all cached SA messages when a connection is 168 established. Finally, the timer is deleted when the MSDP process is 169 deconfigured. 171 8.3. SA Cache Timeout (SA-State Timer) 173 Each entry in an SA Cache has an associated SA-State Timer. A 174 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 175 received by a MSDP peer. The timer is reset to [SA-State-Period] if 176 another (S,G)-SA message is received before the (S,G)-SA-State Timer 177 expires. [SA-State-Period] MUST NOT be less than [SA-Advertisement- 178 Period] + [SA-Hold-Down-Period]. 180 8.4. SA-Hold-Down Timer 182 When an SA message is received which creates (S,G) state, the 183 (S,G)-SA message will be forwarded if the peer-RPF check succeeds. If 184 the peer-RPF check succeeds and the (S,G)-SA message is not already 185 in the SA cache, then the (S,G)-SA-Hold-Down timer is set to [SA- 186 Hold-Down-Period] seconds. When an (S,G)-SA message is received and 187 an (S,G) entry already exists, the message is forwarded only if the 188 (S,G)-SA-Hold-Down timer is not running. [SA-Hold-Down-Period] SHOULD 189 be set to 30 seconds. 191 8.5. Peer Hold Timer 193 If a system has not received any MSDP message within the period 194 specified by the Hold Timer, then a Notification message with Hold 195 Timer Expired Error Code MUST be sent and the MSDP connection MUST be 196 closed. [HoldTime-Period] MUST be at least three seconds. The 197 recommended value for [HoldTime-Period] is 90 seconds. 199 The Hold Timer is initialized to [HoldTime-Period] when the peer's 200 transport connection is established, and is reset to [HoldTime- 201 Period] when any MSDP message is received. Finally, the timer is 202 deleted when the peer's transport connection is closed. 204 8.6. KeepAlive Timer 206 Once an MSDP transport connection is established, each side of the 207 connection sends a KeepAlive message and sets a KeepAlive timer. If 208 the KeepAlive timer expires, the local system sends a KeepAlive 209 message and restarts its KeepAlive timer. 211 The KeepAlive timer is set to [KeepAlive-Period] when the peer comes 212 up. The timer is reset to [KeepAlive-Period] each time an MSDP 213 message is sent to the peer, and reset when the timer expires. 215 Finally, the KeepAlive timer is deleted when the peer's transport 216 connection is closed. 218 [KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be 219 at least one second. The recommended value for [KeepAlive-Period] is 220 75 seconds. 222 8.7. ConnectRetry Timer 224 The ConnectRetry timer is used by an MSDP peer to transition from 225 INACTIVE to CONNECTING states. There is one timer per peer, and the 226 [ConnectRetry-Period] SHOULD be set to 30 seconds. The timer is 227 initialized to [ConnectRetry-Period] when an MSDP speaker attempts to 228 actively open a TCP connection to its peer (see section 15, event E2, 229 action A2 ). When the timer expires, the peer retries the connection 230 and the timer is reset to [ConnectRetry-Period]. It is deleted if 231 either the connection transitions into ESTABLISHED state or the peer 232 is deconfigured. 234 9. Intermediate MSDP Peers 236 Intermediate MSDP speakers do not originate periodic SA messages on 237 behalf of sources in other domains. In general, an RP MUST only 238 originate an SA for a source which would register to it, and ONLY RPs 239 may originate SA messages. 241 10. SA Filtering and Policy 243 As the number of (S,G) pairs increases in the Internet, an RP may 244 want to filter which sources it describes in SA messages. Also, 245 filtering may be used as a matter of policy which at the same time 246 can reduce state. Only the RP co-located in the same domain as the 247 source can restrict SA messages. Note, however, that MSDP peers in 248 transit domains should not filter SA messages or the flood-and-join 249 model can not guarantee that sources will be known throughout the 250 Internet (i.e., SA filtering by transit domains can cause undesired 251 lack of connectivity). In general, policy should be expressed using 252 MBGP [RFC2283]. This will cause MSDP messages to flow in the desired 253 direction and peer-RPF fail otherwise. An exception occurs at an 254 administrative scope [RFC2365] boundary. In particular, a SA message 255 for a (S,G) MUST NOT be sent to peers which are on the other side of 256 an administrative scope boundary for G. 258 11. SA Requests 260 A MSDP speaker MAY accept SA-Requests from other MSDP peers. When an 261 MSDP speaker receives an SA-Request for a group range, it will 262 respond to the peer with a set of SA entries, in an SA-Response 263 message, for all active sources in its SA cache sending to the group 264 requested in the SA-Request message. The peer that sends the request 265 will not flood the responding SA-Response message to other peers. See 266 section 17 for discussion of error handling relating to SA requests 267 and responses. 269 12. Encapsulated Data Packets 271 The RP may encapsulate multicast data from the source. An interested 272 RP may decapsulate the packet, which SHOULD be forwarded as if a PIM 273 register encapsulated packet was received. That is, if packets are 274 already arriving over the interface toward the source, then the 275 packet is dropped. Otherwise, if the outgoing interface list is non- 276 null, the packet is forwarded appropriately. Note that when doing 277 data encapsulation, an implementation MUST bound the time during 278 which packets are encapsulated. 280 This allows for small bursts to be received before the multicast tree 281 is built back toward the source's domain. For example, an 282 implementation SHOULD encapsulate at least the first packet to 283 provide service to bursty sources. 285 13. Other Scenarios 287 MSDP is not limited to deployment across different routing domains. 288 It can be used within a routing domain when it is desired to deploy 289 multiple RPs for the same group ranges. As long as all RPs have a 290 interconnected MSDP topology, each can learn about active sources as 291 well as RPs in other domains. 293 14. MSDP Peer-RPF Forwarding 295 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 296 messages throughout an MSDP enabled internet. Unlike the RPF check 297 used when forwarding data packets, the Peer-RPF check is against the 298 RP address carried in the SA message. 300 14.1. Definitions 302 The following definitions are used in the description of the Peer-RPF 303 Forwarding Rules: 305 14.1.1. Multicast RPF Routing Information Base (MRIB) 307 The MRIB is the multicast topology table. It is typically derived 308 from the unicast routing table or from other routing protocols such 309 as multi-protocol BGP [RFC2283]. 311 14.1.2. RPF Route 313 The RPF route is the route that the MRIB chooses for a given address. 314 The RPF route for a SA's originating RP is used to select the peer 315 from which the SA is accepted. 317 14.2. Peer-RPF Forwarding Rules 319 An SA message originated by R and received by X from N is 320 accepted if N is the peer-RPF neighbor for X, and is discarded 321 otherwise. 323 MPP(R,N) MP(N,X) 324 R ---------....-------> N ------------------> X 325 SA(S,G,R) SA(S,G,R) 327 Where MPP(R,N) is an MSDP peering path (zero or more MSDP 328 peers) between R and N. SA(S,G,R) is an SA message for source 329 S on group G originated by an RP R. MP(N,X) is an MSDP 330 peering between N and X. 332 The peer-RPF neighbor is chosen deterministically, using the 333 first of the following rules that matches. In particular, 334 N is the RPF neighbor of X with respect to R if 336 (i). N == R (X has an MSDP peering with R). 338 (ii). N is the BGP NEXT_HOP of the active RPF route 339 for R. 341 (iii). The active RPF route for R is learned through a 342 distance-vector or path-vector routing protocol 343 (e.g. BGP, RIP, DVMRP) and N is the neighbor that 344 advertised the active RPF route for R if the 345 route was learned via a distance-vector or 346 path-vector protocol, or N is the IGP next hop 347 for if R was learned via a link-state protocol. 349 (iv). N resides in an AS that is in the AS_PATH of the active 350 RPF route for R, and N has the highest IP address among 351 the MSDP peers that reside in ASs in that AS_PATH. 353 (v). N is configured as the static RPF-peer for R. 355 14.3. MSDP static RPF-peer semantics 357 If none of the rules (i) - (iv) are able to determine an RPF peer for 358 R, a longest-match lookup is performed in the static RPF peer table. 359 This table MUST be able to contain a default entry, and SHOULD be 360 able to contain prefix or per-host (RP) entries. This table 361 statically maps RP addresses to peers, and allows configuration of 362 topology that is e.g. unknown to the MRIB. 364 The result of the longest-match lookup of an RP address R in the 365 static RPF peer table is an MSDP peer, which is the RPF neighbor for 366 R. 368 14.4. MSDP mesh-group semantics 370 A MSDP mesh-group is a operational mechanism for reducing SA 371 flooding, typically in an intra-domain setting. In particular, when 372 some subset of a domain's MSDP speakers are fully meshed, then can be 373 configured into a mesh-group. 375 Note that mesh-groups assume that a member doesn't have to forward an 376 SA to other members of the mesh-group because the originator will 377 forward to all members. To be able for the originator to forward to 378 all members (and to have each member also be a potential originator), 379 the mesh-group must be a full mesh of MSDP peering among all members. 381 The semantics of the mesh-group are as follows: 383 (i). If a member R of a mesh-group M receives a SA message from an 384 MSDP peer that is also a member of mesh-group M, R accepts the 385 SA message and forwards it to all of its peers that are not 386 part of any mesh-group. R MUST NOT forward the SA message to 387 other members of mesh-group M. 389 (ii). If a member R of a mesh-group M receives a SA message from an 390 MSDP peer that is not a member of mesh-group M, and the SA 391 message passes the peer-RPF check, then R forwards the SA 392 message to all members of mesh-group M. 394 (iii). Cross mesh-group forwarding 396 If a member R of a mesh-groups M and N receives an SA 397 message from an MSDP peer in mesh-group M, R forwards the SA 398 to its MSDP peers in mesh-group N if it receives that SA 399 message from a peer that is in the same mesh-group as its 400 peer-RPF neighbor for that SA. 402 For example, consider the case in which three routers (R1, R2, 403 and R3) and three mesh-groups (A, B, and C) are arranged in a 404 triangle, e.g., 406 [R2] {A,B} 407 / \ 408 / \ 409 / \ 410 / \ 411 {A,C} [R1]--------[R3] {B,C} 413 Now, when R1 receives an SA message from R2 and R1's 414 peer-RPF neighbor for this SA lies in mesh-group A, R1 415 forwards the SA message its peers in other mesh-groups 416 (in particular, R3 in mesh-group C). Similarly, if R3's 417 peer-RPF neighbor lies in mesh-group B, R3 will forward an 418 SA message from R2. In this case, both R1 and R3 will send 419 SA messages to each other (because they share common mesh-group 420 C), but neither of them will forward any further the SA messages 421 received from each other (as their peer-RPF neighbors do 422 not lie in mesh-group C). 424 Note that since mesh-groups suspend peer-RPF checking of SAs received 425 from a mesh-group member ((i). above), they allow for mis- 426 configuration to cause SA looping. 428 15. MSDP Connection State Machine 430 MSDP uses TCP as its transport protocol. In a peering relationship, 431 one MSDP peer listens for new TCP connections on the well-known port 432 639. The other side makes an active connect to this port. The peer 433 with the higher IP address will listen. This connection establishment 434 algorithm avoids call collision. Therefore, there is no need for a 435 call collision procedure. It should be noted, however, that the 436 disadvantage of this approach is that it may result in longer startup 437 times at the passive side. 439 An MSDP peer starts in the DISABLED state. MSDP peers establish 440 peering sessions according to the following state machine: 442 --------------->+----------+ 443 / | DISABLED |<---------- 444 | ------>+----------+ \ 445 | / |E1->A1 | 446 | | | | 447 | | V |E7->A7 448 | | +----------+ E3->A3 +--------+ 449 | | | INACTIVE |------->| LISTEN | 450 | | +----------+ +--------+ 451 | | E2->A2| ^ |E5->A5 452 | | | | | 453 | |E7->A6 V |E6 | 454 | \ +------------+ | 455 E7->A8 | ------| CONNECTING | | 456 E8->A9 | +------------+ | 457 E9->A10| |E4->A4 | 458 E10->A11| | | 459 E11->A12| V | 460 \ +-------------+ / 461 --------------| ESTABLISHED |<--------- 462 +-------------+ 464 15.1. Events 466 E1) Enable MSDP peering with P 467 E2) Own IP address < P's IP address 468 E3) Own IP address > P's IP address 469 E4) TCP established (active side) 470 E5) TCP established (passive side) 471 E6) ConnectRetry timer expired 472 E7) Disable MSDP peering with P 473 An example of when to do this is when one's own address is 474 changed) 475 E8) Hold Timer expired 476 E9) Authorization failure 477 E10) Notification TLV received 478 E11) Error detected 480 15.2. Actions 482 A1) Allocate resources for peering with P 483 Compare one's own and peer's IP addresses 484 A2) TCP active OPEN 485 Set ConnectRetry timer to [ConnectRetry-Period] 486 A3) TCP passive OPEN (listen) 487 A4) Delete ConnectRetry timer 488 Send KeepAlive TLV 489 Set KeepAlive timer to [KeepAlive-Period] 490 Set Hold Timer to [HoldTime-Period] 491 A5) Send KeepAlive TLV 492 Set KeepAlive timer to [KeepAlive-Period] 493 Set Hold Timer to [HoldTime-Period] 494 A6) Abort TCP active OPEN attempt 495 Release resources allocated for peering with P 496 A7) Abort TCP passive OPEN attempt 497 Release resources allocated for peering with P 499 In action sets 8)-12), the action "Close peering session" includes 500 the following steps: 501 Close TCP connection 502 Delete KeepAlive timer 503 Delete Hold Timer 504 Release resources allocated for peering with P 506 A8) Send Notification TLV with Error Code "Cease" 507 Close peering session 508 A9) Send Notification TLV with Error Code "Hold Timer Expired" 509 Close peering session 511 A10) Notify management system unless this has already been done by 512 the security mechanism 513 Close peering session 514 A11) Notify management system 515 If the received Notification TLV's O-bit was cleared, close 516 peering session. Otherwise, remain in ESTABLISHED state. 517 A12) Send Notification TLV with appropriate Error Code 518 Notify management system 519 If the sent Notification TLV's O-bit was cleared, close peering 520 session. Otherwise, remain in ESTABLISHED state. 522 15.3. Peer-specific Events 524 The following peer-specific events can occur in the ESTABLISHED 525 state, they do not cause a state transition. Appropriate actions are 526 listed for each event. 528 *) KeepAlive timer expired: 529 -> Send KeepAlive TLV 530 -> Set KeepAlive timer to [KeepAlive-Period] 531 *) KeepAlive TLV received: 532 -> Set Hold Timer to [HoldTime-Period] 533 *) Source-Active TLV received: 534 -> Set Hold Timer to [HoldTime-Period] 535 -> Run Peer-RPF Forwarding algorithm (consider SA-Hold-Down 536 Timer and SA-State Timer) 537 -> Set KeepAlive timer to [KeepAlive-Period] for those peers 538 the Source-Active TLV is forwarded to 539 -> Send information to PIM-SM 540 -> Store information in cache 541 *) Source-Active Request TLV received: 542 -> Set Hold Timer to [HoldTime-Period] 543 -> If SA-Requests are accepted, send Source-Active Response 544 TLV and set KeepAlive timer to [KeepAlive-Period] 545 *) Source-Active Response TLV received: 546 -> Set Hold Timer to [HoldTime-Period] 547 -> If a corresponding SA-Request were previously sent, send 548 information to PIM-SM. If not, an error has occured 549 (event 11 above) 550 -> Store information in cache 552 15.4. Peer-independent Events 554 There are also a number of events that affect more than one peering 555 session, but still require actions to be performed on a per-peer 556 basis. 558 *) SA-Advertisement-Timer expired: 559 -> Start periodic transmission of Source-Active TLV(s) 560 -> Set KeepAlive timer to [KeepAlive-Period] each time a 561 Source-Active TLV is sent 562 *) MSDP learns of a new active internal source (e.g. PIM-SM 563 register received for a new source): 564 -> Send Source-Active TLV 565 -> Set KeepAlive timer to [KeepAlive-Period] 566 *) Source-Active Request triggered (event not specified here): 567 -> Send Source-Active Request TLV 568 -> Set KeepAlive timer to [KeepAlive-Period] 569 *) SA-State-Timer expired (one timer per cache entry): 570 -> Implementation specific, typically mark the cache entry for 571 deletion 573 16. Packet Formats 575 MSDP messages will be encoded in TLV format. If an implementation 576 receives a TLV that has length that is longer than expected, the TLV 577 SHOULD be accepted. Any additional data SHOULD be ignored. 579 16.1. MSDP TLV format: 581 0 1 2 3 582 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 1 583 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 | Type | Length | Value .... | 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 Type (8 bits) 588 Describes the format of the Value field. 590 Length (16 bits) 591 Length of Type, Length, and Value fields in octets. 592 minimum length required is 4 octets, except for 593 Keepalive messages. The maximum TLV length is 1400. 595 Value (variable length) 596 Format is based on the Type value. See below. The length of 597 the value field is Length field minus 3. All reserved fields 598 in the Value field MUST be transmitted as zeros and ignored on 599 receipt. 601 16.2. Defined TLVs 603 The following TLV Types are defined: 605 Code Type 606 =========================================================== 607 1 IPv4 Source-Active 608 2 IPv4 Source-Active Request 609 3 IPv4 Source-Active Response 610 4 KeepAlive 611 5 Notification 613 Each TLV is described below. 615 In addition, the following TLV Types are assigned but not described 616 in this memo: 618 Code Type 619 =========================================================== 620 6 MSDP traceroute in progress 621 7 MSDP traceroute reply 623 16.2.1. IPv4 Source-Active TLV 625 The maximum size SA message that can be sent is 9192 octets. The 9192 626 octet size does not include the TCP, IP, layer-2 headers. 628 0 1 2 3 629 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 1 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 | 1 | x + y | Entry Count | 632 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 | RP Address | 634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 | Reserved | Sprefix Len | \ 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 637 | Group Address | ) z 638 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 639 | Source Address | / 640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 Type 643 IPv4 Source-Active TLV is type 1. 645 Length x 646 Is the length of the control information in the message. x is 647 8 octets (for the first two 32-bit quantities) plus 12 times 648 Entry Count octets. 650 Length y 651 If 0, then there is no data encapsulated. Otherwise an IPv4 652 packet follows and y is the length of the total length field 653 of the IPv4 header encapsulated. If there are multiple SA TLVs 654 in a message, and data is also included, y must be 0 in all SA 655 TLVs except the last one and the last SA TLV must reflect the 656 source and destination addresses in the IP header of the 657 encapsulated data. 659 Entry Count 660 Is the count of z entries (note above) which follow the RP 661 address field. This is so multiple (S,G)s from the same domain 662 can be encoded efficiently for the same RP address. 664 RP Address 665 The address of the RP in the domain the source has become 666 active in. 668 Reserved 669 The Reserved field MUST be transmitted as zeros and MUST be 670 ignored by a receiver. 672 Sprefix Len 673 The route prefix length associated with source address. 674 This field MUST be transmitted as 32 (/32). An Invalid 675 Sprefix Len Notification SHOULD be sent upon receipt 676 of any other value. 678 Group Address 679 The group address the active source has sent data to. 681 Source Address 682 The IP address of the active source. 684 Multiple SA TLVs MAY appear in the same message and can be batched 685 for efficiency at the expense of data latency. This would typically 686 occur on intermediate forwarding of SA messages. 688 16.2.2. IPv4 Source-Active Request TLV 690 The Source-Active Request is used to request SA-state from a MSDP 691 peer. If an RP in a domain receives a PIM Join message for a group, 692 creates (*,G) state and wants to know all active sources for group G, 693 it may send an SA-Request message for the group. 695 0 1 2 3 696 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 1 697 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 698 | 2 | 8 | Reserved | 699 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 700 | Group Address | 701 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 Type 704 IPv4 Source-Active Request TLV is type 2. 706 Reserved 707 Must be transmitted as zero and ignored on receipt. 709 Group Address 710 The group address the MSDP peer is requesting. 712 16.2.3. IPv4 Source-Active Response TLV 714 The Source-Active Response is sent in response to a Source-Active 715 Request message. The Source-Active Response message has the same 716 format as a Source-Active message but does not allow encapsulation of 717 multicast data. 719 0 1 2 3 720 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 1 721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 722 | 3 | x | .... | 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 Type 726 IPv4 Source-Active Response TLV is type 3. 728 Length x 729 Is the length of the control information in the message. x is 8 730 octets (for the first two 32-bit quantities) plus 12 times Entry 731 Count octets. 733 16.2.4. KeepAlive TLV 735 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 736 MSDP messages sent to the peer within [KeepAlive-Period] seconds. 737 This message is necessary to keep the MSDP connection alive. 739 0 1 2 3 740 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 1 741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 742 | 4 | 3 | 743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 745 The length of the message is 3 octets which encompasses the one octet 746 Type field and the two octet Length field. 748 16.2.5. Notification TLV 750 A Notification message is sent when an error condition is detected, 751 and has the following form: 753 0 1 2 3 754 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 1 755 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 756 | 5 | x + 5 |O| Error Code | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 | Error subcode | ... | 759 +-+-+-+-+-+-+-+-+ | 760 | Data | 761 | ... | 762 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 764 Type 765 The Notification TLV is type 5. 767 Length 768 Length is a two octet field with value x + 5, where x is 769 the length of the notification data field. 771 O-bit 772 Open-bit. If clear, the connection will be closed. 774 Error code 775 This 7-bit unsigned integer indicates the type of Notification. 776 The following Error Codes have been defined: 778 Error Code Symbolic Name Reference 780 1 Message Header Error Section 17.1 781 2 SA-Request Error Section 17.2 782 3 SA-Message/SA-Response Error Section 17.3 783 4 Hold Timer Expired Section 17.4 784 5 Finite State Machine Error Section 17.5 785 6 Notification Section 17.6 786 7 Cease Section 17.7 788 Error subcode: 789 This one-octet unsigned integer provides more specific information 790 about the reported error. Each Error Code may have one or more Error 791 Subcodes associated with it. If no appropriate Error Subcode is 792 defined, then a zero (Unspecific) value is used for the Error Subcode 793 field, and the O-bit must be cleared (i.e. the connection will be 794 closed). The used notation in the error description below is: MC = 795 Must Close connection = O-bit clear; CC = Can Close connection = 796 O-bit MAY be cleared. 798 Message Header Error subcodes: 800 0 - Unspecific (MC) 801 2 - Bad Message Length (MC) 802 3 - Bad Message Type (CC) 804 SA-Request Error subcodes (the O-bit is always clear): 806 0 - Unspecific (MC) 807 1 - Invalid Group (MC) 809 SA-Message/SA-Response Error subcodes 811 0 - Unspecific (MC) 812 1 - Invalid Entry Count (CC) 813 2 - Invalid RP Address (MC) 814 3 - Invalid Group Address (MC) 815 4 - Invalid Source Address (MC) 816 5 - Invalid Sprefix Length (MC) 817 6 - Looping SA (Self is RP) (MC) 818 7 - Unknown Encapsulation (MC) 819 8 - Administrative Scope Boundary Violated (MC) 821 Hold Timer Expired subcodes (the O-bit is always clear): 823 0 - Unspecific (MC) 825 Finite State Machine Error subcodes (the O-bit is always clear): 827 0 - Unspecific (MC) 828 1 - Unexpected Message Type FSM Error (MC) 830 Notification subcodes (the O-bit is always clear): 832 0 - Unspecific (MC) 834 Cease subcodes (the O-bit is always clear): 836 0 - Unspecific (MC) 838 17. MSDP Error Handling 840 This section describes actions to be taken when errors are detected 841 while processing MSDP messages. MSDP Error Handling is similar to 842 that of BGP [RFC1771]. 844 When any of the conditions described here are detected, a 845 Notification message with the indicated Error Code, Error Subcode, 846 and Data fields is sent. In addition, the MSDP connection MAY be 847 closed. If no Error Subcode is specified, then a zero (Unspecific) 848 must be used. 850 The phrase "the MSDP connection is closed" means that the transport 851 protocol connection has been closed and that all resources for that 852 MSDP connection have been deallocated. 854 17.1. Message Header Error Handling 856 All errors detected while processing the Message Header are indicated 857 by sending the Notification message with Error Code Message Header 858 Error. The Error Subcode describes the specific nature of the error. 859 The Data field contains the erroneous Message (including the message 860 header). 862 If the Length field of the message header is less than 4 or greater 863 than 1400, or the length of a KeepAlive message is not equal to 3, 864 then the Error Subcode is set to Bad Message Length. 866 If the Type field of the message header is not recognized, then the 867 Error Subcode is set to Bad Message Type. 869 17.2. SA-Request Error Handling 871 The SA-Request Error code is used to signal the receipt of a SA 872 request at a MSDP peer when an invalid group address requested. 874 When a MSDP peer receives a request for an invalid group, it returns 875 the following notification: 877 0 1 2 3 878 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 1 879 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 880 | 5 | 12 |O| 2 | 881 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 882 | 1 | Reserved | 883 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 884 | Group Address | 885 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 887 17.3. SA-Message/SA-Response Error Handling 889 The SA-Message/SA-Response Error code is used to signal the receipt 890 of a erroneous SA Message at an MSDP peer, or the receipt of an SA- 891 Response Message by a peer that did not issue a SA-Request. It has 892 the following form: 894 17.3.1. Invalid Entry Count (IEC) 896 0 1 2 3 897 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 1 898 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 899 | 5 | 6 |O| 3 | 900 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 901 | 1 | Entry Count | 902 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 904 17.3.2. Invalid RP Address 906 0 1 2 3 907 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 1 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 909 | 5 | 12 |O| 3 | 910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 911 | 2 | Reserved | 912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 913 | RP Address | 914 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 916 17.3.3. Invalid Group Address 918 0 1 2 3 919 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 1 920 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 921 | 5 | 12 |O| 3 | 922 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 923 | 3 | Reserved | 924 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 925 | Group Address | 926 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 928 17.3.4. Invalid Source Address 930 0 1 2 3 931 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 1 932 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 933 | 5 | 12 |O| 3 | 934 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 935 | 4 | Reserved | 936 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 937 | Source Address | 938 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 940 17.3.5. Invalid Sprefix Length (ISL) 942 0 1 2 3 943 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 1 944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 945 | 5 | 6 |O| 3 | 946 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 947 | 5 | Sprefix Len | 948 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 950 17.3.6. Looping SAs (Self is RP in received SA) 952 0 1 2 3 953 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 1 954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 955 | 5 | x + 5 |O| 3 | 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 957 | 6 | SA Message .... 958 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 960 Length x 961 x is the length of the looping SA message contained in the data 962 field of the Notification message. 964 17.3.7. Unknown Encapsulation 966 This notification is sent on receipt of SA data that is encapsulated 967 in an unknown encapsulation type. See section 18 for known 968 encapsulations. 970 0 1 2 3 971 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 1 972 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 973 | 5 | x + 5 |O| 3 | 974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 975 | 7 | SA Message .... 976 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 978 Length x 979 x is the length of the SA message (which contained data which 980 was encapsulated in some unknown way) that is contained in the 981 data field of the Notification message. 983 17.3.8. Administrative Scope Boundary Violated 985 This notification is used when an SA message is received for a group 986 G from a peer which is across an administrative scope boundary for G. 988 0 1 2 3 989 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 1 990 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 991 | 5 | 12 |O| 3 | 992 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 993 | 8 | Reserved | 994 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 995 | Group Address | 996 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 998 17.4. Hold Time Expired 1000 If a system has not received any MSDP message within the period 1001 specified in the Hold Timer, the notification message with Hold Timer 1002 Expired Error Code and no additional data MUST be sent and the MSDP 1003 connection closed. 1005 17.5. Finite State Machine Error Handling 1007 Any error detected by the MSDP Finite State Machine (e.g., receipt of 1008 an unexpected event) is indicated by sending the Notification message 1009 with Error Code Finite State Machine Error. 1011 17.6. Notification Message Error Handling 1013 If a node sends a Notification message, and there is an error in that 1014 message, and the O-bit of that message is not clear, a Notification 1015 with O-bit clear, Error Code of Notification Error, and subcode 1016 Unspecific must be sent. In addition, the Data field must include 1017 the Notification message that triggered the error. However, if the 1018 erroneous Notification message had the O-bit clear, then any error, 1019 such as an unrecognized Error Code or Error Subcode, should be 1020 noticed, logged locally, and brought to the attention of the 1021 administrator of the remote node. 1023 17.7. Cease 1025 In absence of any fatal errors (that are indicated in this section), 1026 an MSDP node may choose at any given time to close its MSDP 1027 connection by sending the Notification message with Error Code Cease. 1028 However, the Cease Notification message MUST NOT be used when a fatal 1029 error indicated by this section does exist. 1031 18. SA Data Encapsulation 1033 This section describes UDP, GRE, and TCP encapsulation of data 1034 packets to be included with SA messages. Encapsulation type is a 1035 configuration option. 1037 18.1. UDP Data Encapsulation 1039 Data packets MAY be encapsulated in UDP. In this case, the UDP 1040 pseudo-header has the following form: 1042 0 1 2 3 1043 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 1044 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1045 | Source Port | Destination Port | 1046 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1047 | Length | Checksum | 1048 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1049 | Origin RP Address | 1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1052 The Source port, Destination Port, Length, and Checksum are used 1053 according to RFC 768. Source and Destination ports are known via 1054 an implementation-specific method (e.g. per-peer configuration). 1056 Checksum 1057 The checksum is computed according to RFC 768 [RFC768]. 1059 Originating RP Address 1060 The Originating RP Address is the address of the RP sending 1061 the encapsulated data. 1063 18.2. GRE Encapsulation 1065 MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP- 1066 GRE-ProtocolType]. The GRE header and payload packet have the 1067 following form: 1069 0 1 2 3 1070 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 1071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1072 |C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\ 1073 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header 1074 | Checksum (optional) | Reserved1 |/ 1075 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1076 | Originating RP IPv4 Address |\ 1077 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload 1078 | (S,G) Data Packet .... / 1079 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1081 18.2.1. Encapsulation and Path MTU Discovery [RFC1191] 1083 Existing implementations of GRE, when using IPv4 as the Delivery 1084 Header, do not implement Path MTU discovery and do not set the Don't 1085 Fragment bit in the Delivery Header. This can cause large packets to 1086 become fragmented within the tunnel and reassembled at the tunnel 1087 exit (independent of whether the payload packet is using PMTU). If a 1088 tunnel entry point were to use Path MTU discovery, however, that 1089 tunnel entry point would also need to relay ICMP unreachable error 1090 messages (in particular the "fragmentation needed and DF set" code) 1091 back to the originator of the packet, which is not required by the 1092 GRE specification [RFC2784]. Failure to properly relay Path MTU 1093 information to an originator can result in the following behavior: 1094 the originator sets the don't fragment bit, the packet gets dropped 1095 within the tunnel, but since the originator doesn't receive proper 1096 feedback, it retransmits with the same PMTU, causing subsequently 1097 transmitted packets to be dropped. 1099 18.3. TCP Data Encapsulation 1101 As discussed earlier, encapsulation of data in SA messages MAY be 1102 supported for backwards compatibility with legacy MSDP peers. 1104 19. IANA Considerations 1106 The IANA should assign 0x0009 from the IANA SNAP Protocol IDs [IANA] 1107 to MSDP-GRE-ProtocolType. 1109 20. Security Considerations 1111 An MSDP implementation MUST use IPsec [RFC2401] to secure control 1112 messages. In particular, the TCP connection between MSDP peers MUST 1113 be secured using IPsec. When encapsulating data packets in GRE, 1114 security should be relatively similar to security in a normal IPv4 1115 network, as routing using GRE follows the same routing that IPv4 uses 1116 natively. Route filtering will remain unchanged. However packet 1117 filtering at a firewall requires either that a firewall look inside 1118 the GRE packet or that the filtering is done on the GRE tunnel 1119 endpoints. In those environments in which this is considered to be a 1120 security issue it may be desirable to terminate the tunnel at the 1121 firewall. 1123 21. Acknowledgments 1125 The editors would like to thank the original authors, Dino Farinacci, 1126 Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their 1127 orginal contribution to the MSDP specification. In addition, Bill 1128 Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, 1129 John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina 1130 Priestley and IJsbrand Wijnands provided useful and productive design 1131 feedback and comments. In addition to many other contributions, Tom 1132 Pusateri, Kristofer Warell, Henning Eriksson, and Thomas Eriksson 1133 helped to clarify the connection state machine, Dave Thaler helped to 1134 clarify the Notification message types. Ravi Shekhar helped clarify 1135 the semantics of mesh-groups, and countless others helped to clarify 1136 the Peer-RPF rules. 1138 22. Editors' Address: 1140 David Meyer 1141 Sprint 1142 12502 Sunrise Valley Drive 1143 Reston VA, 20191 1144 Email: dmm@sprint.net 1146 Bill Fenner 1147 AT&T Labs -- Research 1148 75 Willow Road 1149 Menlo Park, CA 94025 1150 Email: fenner@research.att.com 1152 23. REFERENCES 1154 [IANA] http://www.iana.org 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 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 1166 Requirement Levels", RFC 2119, March, 1997. 1168 [RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., 1169 "Multiprotocol Extensions for BGP-4", RFC 2283, 1170 February 1998. 1172 [RFC2362] Estrin D., et al., "Protocol Independent Multicast - 1173 Sparse Mode (PIM-SM): Protocol Specification", RFC 1174 2362, June 1998. 1176 [RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC 1177 2365, July, 1998. 1179 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for 1180 the Internet Protocol", RFC 2401, November 1998. 1182 [RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation 1183 (GRE)", RFC 2784, March 2000. 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.