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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 important so that new receivers who join after a source has been active can get data quickly via the receiver's own RP when it is not caching SA state. 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. 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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 180, but not defined == Missing Reference: 'SA-State-Period' is mentioned on line 200, but not defined == Missing Reference: 'SA-Hold-Down-Period' is mentioned on line 208, but not defined == Missing Reference: 'KeepAlive-Period' is mentioned on line 221, but not defined == Missing Reference: 'ConnectRetry-Period' is mentioned on line 232, but not defined == Missing Reference: 'Hold-Time-Period' is mentioned on line 245, but not defined == Missing Reference: 'MSDP-GRE-ProtocolType' is mentioned on line 910, but not defined == Outdated reference: draft-meyer-gre-update has been published as RFC 2784 ** Obsolete normative reference: RFC 1771 (Obsoleted by RFC 4271) ** Obsolete normative reference: RFC 1825 (Obsoleted by RFC 2401) ** 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: 14 errors (**), 0 flaws (~~), 15 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Dino Farinacci 3 INTERNET DRAFT Procket Networks 4 Yakov Rekhter 5 David Meyer 6 Cisco Systems 7 Peter Lothberg 8 Sprint 9 Hank Kilmer 10 Jeremy Hall 11 UUnet 12 Category Standards Track 13 February, 2000 15 Multicast Source Discovery Protocol (MSDP) 16 18 1. Status of this Memo 20 This document is an Internet-Draft and is in full conformance with 21 all provisions of Section 10 of RFC 2026. 23 Internet Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that other 25 groups may also distribute working documents as Internet-Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 2. Abstract 40 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 41 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 42 its own independent RP(s) and does not have to depend on RPs in other 43 domains. 45 3. Copyright Notice 47 Copyright (C) The Internet Society (2000). All Rights Reserved. 49 4. Introduction 51 The Multicast Source Discovery Protocol, MSDP, describes a mechanism 52 to connect multiple PIM-SM domains together. Each PIM-SM domain uses 53 its own independent RP(s) and does not have to depend on RPs in other 54 domains. Advantages of this approach include: 56 o No Third-party resource dependencies on RP 58 PIM-SM domains can rely on their own RPs only. 60 o Receiver only Domains 62 Domains with only receivers get data without globally 63 advertising group membership. 65 o Global Source State 67 Global source state is not required, since a router need not 68 cache Source Active (SA) messages (see below). MSDP is a 69 periodic protocol. 71 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, 72 SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined 73 in RFC 2119 [RFC2119]. 75 5. Overview 77 MSDP-speaking routers in a PIM-SM [RFC2362] domain will have a MSDP 78 peering relationship with MSDP peers in another domain. The peering 79 relationship will be made up of a TCP connection in which control 80 information is exchanged. Each domain will have one or more 81 connections to this virtual topology. 83 The purpose of this topology is to allow domains discover multicast 84 sources from other domains. If the multicast sources are of interest 85 to a domain which has receivers, the normal source-tree building 86 mechanism in PIM-SM will be used to deliver multicast data over an 87 inter-domain distribution tree. 89 We envision this virtual topology will essentially be congruent to 90 the existing BGP topology used in the unicast-based Internet today. 91 That is, the TCP connections between MSDP peers are likely to be 92 congruent to the connections in the BGP routing system. 94 6. Procedure 96 A source in a PIM-SM domain originates traffic to a multicast group. 97 The PIM DR which is directly connected to the source sends the data 98 encapsulated in a PIM Register message to the RP in the domain. 100 The RP will construct a "Source-Active" (SA) message and send it to 101 its MSDP peers. The SA message contains the following fields: 103 o Source address of the data source. 104 o Group address the data source sends to. 105 o IP address of the RP. 107 Each MSDP peer receives and forwards the message away from the RP 108 address in a "peer-RPF flooding" fashion. The notion of peer-RPF 109 flooding is with respect to forwarding SA messages. The BGP routing 110 table is examined to determine which peer is the NEXT_HOP towards the 111 originating RP of the SA message. Such a peer is called an "RPF 112 peer". See section 14 below for the details of peer-RPF forwarding. 114 If the MSDP peer receives the SA from a non-RPF peer towards the 115 originating RP, it will drop the message. Otherwise, it forwards the 116 message to all its MSDP peers (except the one from which it received 117 the SA message). 119 The flooding can be further constrained to children of the peer by 120 interrogating BGP reachability information. That is, if a BGP peer 121 advertises a route (back to you) and you are the next to last AS in 122 the AS_PATH, the peer is using you as the NEXT_HOP. This is known in 123 other circles as Split-Horizon with Poison Reverse. An implementation 124 SHOULD NOT forward SA messages (which were originated from the RP 125 address covered by a route) to peers which have not Poison Reversed 126 that route. 128 When an MSDP peer which is also an RP for its own domain receives a 129 new SA message, it determines if it has any group members interested 130 in the group which the SA message describes. That is, the RP checks 131 for a (*,G) entry with a non-empty outgoing interface list; this 132 implies that the domain is interested in the group. In this case, the 133 RP triggers a (S,G) join event towards the data source as if a 134 Join/Prune message was received addressed to the RP itself. This sets 135 up a branch of the source-tree to this domain. Subsequent data 136 packets arrive at the RP which are forwarded down the shared-tree 137 inside the domain. If leaf routers choose to join the source-tree 138 they have the option to do so according to existing PIM-SM 139 conventions. Finally, if an RP in a domain receives a PIM Join 140 message for a new group G, and it is caching SAs, then the RP should 141 trigger a (S,G) join event for each SA for that group in its cache. 143 This procedure has been affectionately named flood-and-join because 144 if any RP is not interested in the group, they can ignore the SA 145 message. Otherwise, they join a distribution tree. 147 7. Controlling State 149 While RPs which receive SA messages are not required to keep MSDP 150 (S,G) state, an RP SHOULD cache SA messages by default. One of the 151 main advantages of caching is that since the RP has MSDP (S,G) state, 152 join latency is greatly reduced for new receivers of G. In addition, 153 caching greatly aids in diagnosis and debugging of various problems. 155 8. Timers 157 The main timers for MSDP are: SA-Advertisement-Timer, SA-Hold-Down- 158 Timer, SA Cache Entry timer, KeepAlive timer, and ConnectRetry and 159 Peer Hold Timer. Each is considered below. 161 8.1. SA-Advertisement-Timer 163 RPs which originate SA messages do it periodically as long as there 164 is data being sent by the source. There is one SA-Advertisement-Timer 165 covering the sources that an RP may advertise. [SA-Advertisement- 166 Period] MUST be 60 seconds. An RP MUST not send more than one 167 periodic SA message for a given (S,G) within an SA Advertisement 168 interval. Originating periodic SA messages is important so that new 169 receivers who join after a source has been active can get data 170 quickly via the receiver's own RP when it is not caching SA state. 171 Finally, an originating RP SHOULD trigger the transmission of an SA 172 message as soon as it receives data from an internal source for the 173 first time. 175 8.2. SA-Advertisement-Timer Processing 177 An RP MUST spread the generation of periodic SA messages over its 178 reporting interval (i.e. SA-Advertisement-Period). An RP starts the 179 SA-Advertisement-Timer when the MSDP process is configured. When the 180 timer expires, an RP resets the timer to [SA-Advertisement-Period] 181 seconds, and begins the advertisement of its active sources. Active 182 sources are advertised in the following manner: An RP packs its 183 active sources into an SA message until the largest MSDP packet that 184 can be sent is built or there are no more sources, and then sends the 185 message. This process is repeated periodically within the SA- 186 Advertisement-Period in such a way that all of the RP's sources are 187 advertised. Note that the largest MSDP packet that can be sent has 188 size that is the minimum of MTU of outgoing link minus size of TCP 189 and IP headers, and 1400 (largest MSDP packet). Finally, the timer is 190 deleted when the MSDP process is deconfigured. Note that a caching 191 implementation may also wish to check the SA-Cache on this timer 192 event. 194 8.3. SA Cache Timeout (SA-State-Timer) 196 Each entry in an SA Cache has an associated SA-State-Timer. A 197 (S,G)-SA-State-Timer is started when an (S,G)-SA message is initially 198 received by a caching MSDP peer. The timer is reset to [SA-State- 199 Period] if another (S,G)-SA message is received before the (S,G)-SA- 200 State-Timer expires. [SA-State-Period] MUST NOT be less than 90 201 seconds. 203 8.4. SA-Hold-Down-Timer 205 A caching MSDP peer SHOULD NOT forward an SA message it has received 206 in during the previous [SA-Hold-Down-Period] seconds. [SA-Hold-Down- 207 Period] SHOULD be set to 30 seconds. The per-SA message timer is set 208 to [SA-Hold-Down-Period] when forwarding an (S,G)-SA message, and a 209 (S,G)-SA message MUST only be forwarded when it's associated timer is 210 not running. Finally, the timer is deleted when the (S,G)-SA cache 211 entry is deleted. 213 8.5. KeepAlive Timer 215 The KeepAlive timer is used by the active connect side of the MSDP 216 connection to track the state of the passive-connect side of the 217 connection. In particular, the KeepAlive timer is used to reset the 218 TCP connection when the passive-connect side of the connection goes 219 down. The KeepAlive timer is set to [KeepAlive-Period] when the 220 passive-connect peer comes up. [KeepAlive-Period] SHOULD NOT be less 221 that 75 seconds. The timer is reset to [KeepAlive-Period] upon 222 receipt of an MSDP message from peer, and deleted when the timer 223 expires or the passive-connect peer closes the connection. 225 8.6. ConnectRetry Timer 227 The ConnectRetry timer is used by an MSDP peer to transition from 228 INACTIVE to CONNECTING states. There is one timer per peer, and the 229 [ConnectRetry-Period] SHOULD be set to 30 seconds. The timer is 230 initialized to [ConnectRetry-Period] when an MSDP peer's active 231 connect attempt fails. When the timer expires, the peer retries the 232 connection and the timer is reset to [ConnectRetry-Period]. It is 233 deleted if either the connection transitions into ESTABLISHED state 234 or the peer is deconfigured. 236 8.7. Peer Hold Timer 238 If a system does not receive successive KeepAlive messages (or any SA 239 message) within the period specified by the Hold Timer, then a 240 Notification message with Hold Timer Expired Error Code MUST be sent 241 and the MSDP connection MUST be closed. [Hold-Time-Period] MUST be at 242 least three seconds. A suggested value for [Hold-Time-Period] is 90 243 seconds. 245 The Hold Timer is initialized to [Hold-Time-Period] when the peer's 246 transport connection is established, and is reset to [Hold-Time- 247 Period] when any MSDP message is received. 249 9. Intermediate MSDP Peers 251 Intermediate RPs do not originate periodic SA messages on behalf of 252 sources in other domains. In general, an RP MUST only originate an SA 253 for a source which would register to it. 255 10. SA Filtering and Policy 257 As the number of (S,G) pairs increases in the Internet, an RP may 258 want to filter which sources it describes in SA messages. Also, 259 filtering may be used as a matter of policy which at the same time 260 can reduce state. Only the RP co-located in the same domain as the 261 source can restrict SA messages. Note, however, that MSDP peers in 262 transit domains should not filter SA messages or the flood-and-join 263 model can not guarantee that sources will be known throughout the 264 Internet (i.e., SA filtering by transit domains can cause undesired 265 lack of connectivity). In general, policy should be expressed using 266 MBGP [RFC2283]. This will cause MSDP messages will flow in the 267 desired direction and peer-RPF fail otherwise. An exception occurs at 268 an administrative scope [RFC2365] boundary. In particular, a SA 269 message for a (S,G) MUST NOT be sent to peers which are on the other 270 side of an administrative scope boundary for G. 272 11. SA Requests 274 If an MSDP peer decides to cache SA state, it MAY accept SA-Requests 275 from other MSDP peers. When an MSDP peer receives an SA-Request for a 276 group range, it will respond to the peer with a set of SA entries, in 277 an SA-Response message, for all active sources sending to the group 278 range requested in the SA-Request message. The peer that sends the 279 request will not flood the responding SA-Response message to other 280 peers. See section 17 for discussion of error handling relating to SA 281 requests and responses. 283 12. Encapsulated Data Packets 285 For bursty sources, the RP may encapsulate multicast data from the 286 source. An interested RP may decapsulate the packet, which SHOULD be 287 forwarded as if a PIM register encapsulated packet was received. That 288 is, if packets are already arriving over the interface toward the 289 source, then the packet is dropped. Otherwise, if the outgoing 290 interface list is non-null, the packet is forwarded appropriately. 291 Note that when doing data encapsulation, an implementation MUST bound 292 the time during which packets are encapsulated. 294 This allows for small bursts to be received before the multicast tree 295 is built back toward the source's domain. For example, an 296 implementation SHOULD encapsulate at least the first packet to 297 provide service to bursty sources. 299 13. Other Scenarios 301 MSDP is not limited to deployment across different routing domains. 302 It can be used within a routing domain when it is desired to deploy 303 multiple RPs for the same group ranges. As long as all RPs have a 304 interconnected MSDP topology, each can learn about active sources as 305 well as RPs in other domains. 307 14. MSDP Peer-RPF Forwarding 309 The MSDP Peer-RPF Forwarding rules are used for forwarding SA 310 messages throughout an MSDP enabled internet. Unlike the RPF check 311 used when forwarding data packets, the Peer-RPF check is against the 312 RP address carried in the SA message. 314 14.1. Peer-RPF Forwarding Rules 316 An SA message originated by an MSDP originator R and received by a 317 MSDP router from MSDP peer N is accepted if N is the appropriate RPF 318 neighbor for originator R (the RP in the SA message), and discarded 319 otherwise. 321 The RPF neighbor is chosen using the first of the following rules 322 that matches: 324 (i). R is the RPF neighbor if we have an MSDP peering with R. 326 (ii). The external MBGP neighbor towards which we are 327 poison-reversing the MBGP route towards R is the RPF neighbor 328 if we have an MSDP peering with it. 330 (iii). If we have any MSDP peerings with neighbors in the first 331 AS along the AS_PATH (the AS from which we learned this 332 route), but no external MBGP peerings with them, 333 the neighbor with the highest IP address is the RPF neighbor. 335 (vi). The internal MBGP advertiser of the router towards R is 336 the RPF neighbor if we have an MSDP peering with it. 338 (v). If none of the above match, and we have an MSDP 339 default-peer configured, the MSDP default-peer is 340 the RPF neighbor. 342 14.2. MSDP default-peer semantics 344 An MSDP default-peer is much like a default route. It is intended to 345 be used in those cases where a stub network isn't running BGP or 346 MBGP. An MSDP peer configured with a default-peer accepts all SA 347 messages from the default-peer. Note that a router running BGP or 348 MBGP SHOULD NOT allow configuration of default peers, since this 349 allows the possibility for SA looping or black-holes to occur. 351 15. MSDP Connection Establishment 353 MSDP messages will be encapsulated in a TCP connection. An MSDP peer 354 listens for new TCP connections on port 639. One side of the MSDP 355 peering relationship will listen on the well-known port and the other 356 side will do an active connect to the well-known port. The side with 357 the higher peer IP address will do the listen. This connection 358 establishment algorithm avoids call collision. Therefore, there is no 359 need for a call collision procedure. It should be noted, however, 360 that the disadvantage of this approach is that it may result in 361 longer startup times at the passive end. 363 An MSDP peer starts in the INACTIVE state. MSDP peers establish 364 peering sessions according to the following state machine: 366 De-configured or 367 disabled 368 +-------------------------------------------+ 369 | | 370 | | 371 Enable | 372 +-----|--------->+----------+ Connect Retry Timer | 373 | | +->| INACTIVE |----------------+ | 374 | | | +----------+ | | 375 Deconf'ed | | | /|\ /|\ | | Lower Address 376 or | | | | | | | 377 disabled | | | | | \|/ | 378 | | | | | | +-------------+ 379 | | | | | +---------------| CONNECTING | 380 | | | | | Timeout or +-------------+ 381 | | | | | Local Address Change | 382 \|/ \|/ | | | | 383 +----------+ | | | | 384 | DISABLED | | | +---------------------+ | TCP Established 385 +----------+ | | | | 386 /|\ /|\ | | Connection Timeout, | | 387 | | | | Local Address change, | | 388 | | | | Authorization Failure | | 389 | | | | | | 390 | | | | | \|/ 391 | | | | +-------------+ 392 | | Local | | | ESTABLISHED | 393 | | Address | | Higher Address +-------------+ 394 | | Change | \|/ /|\ | 395 | | | +--------+ | | 396 | | +--| LISTEN |--------------------+ | 397 | | +--------+ TCP Accept | 398 | | | | 399 | | | | 400 | +---------------+ | 401 | De-configured or | 402 | disabled | 403 | | 404 +------------------------------------------------------+ 405 De-configured or 406 disabled 408 16. Packet Formats 410 MSDP messages will be encoded in TLV format. If an implementation 411 receives a TLV that has length that is longer than expected, the TLV 412 SHOULD be accepted. Any additional data SHOULD be ignored. 414 16.1. MSDP TLV format: 416 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 1 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | Type | Length | Value .... | 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 Type (8 bits) 422 Describes the format of the Value field. 424 Length (16 bits) 425 Length of Type, Length, and Value fields in octets. 426 minimum length required is 4 octets, except for 427 Keepalive messages. 429 Value (variable length) 430 Format is based on the Type value. See below. The length of 431 the value field is Length field minus 3. All reserved fields 432 in the Value field MUST be transmitted as zeros and ignored on 433 receipt. 435 16.2. Defined TLVs 437 The following TLV Types are defined: 439 Code Type 440 =========================================================== 441 1 IPv4 Source-Active 442 2 IPv4 Source-Active Request 443 3 IPv4 Source-Active Response 444 4 KeepAlive 445 5 Notification 447 Each TLV is described below. 449 16.2.1. IPv4 Source-Active TLV 451 The maximum size SA message that can be sent is 1400 octets. If an 452 MSDP peer needs to originate a message with information greater than 453 1400 octets, it sends successive 1400 octet or smaller messages. The 454 1400 octet size does not include the TCP, IP, layer-2 headers. 456 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 1 457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 458 | 1 | x + y | Entry Count | 459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 460 | RP Address | 461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 462 | Reserved | Sprefix Len | \ 463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ 464 | Group Address | ) z 465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 466 | Source Address | / 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 469 Type 470 IPv4 Source-Active TLV is type 1. 472 Length x 473 Is the length of the control information in the message. x is 474 8 octets (for the first two 32-bit quantities) plus 12 times 475 Entry Count octets. 477 Length y 478 If 0, then there is no data encapsulated. Otherwise an IPv4 479 packet follows and y is the length of the total length field 480 of the IPv4 header encapsulated. If there are multiple SA TLVs 481 in a message, and data is also included, y must be 0 in all SA 482 TLVs except the last one and the last SA TLV must reflect the 483 source and destination addresses in the IP header of the 484 encapsulated data. 486 Entry Count 487 Is the count of z entries (note above) which follow the RP 488 address field. This is so multiple (S,G)s from the same domain 489 can be encoded efficiently for the same RP address. 491 RP Address 492 The address of the RP in the domain the source has become 493 active in. 495 Reserved 496 The Reserved field MUST be transmitted as zeros and ignored 497 by a receiver. 499 Sprefix Len 500 The route prefix length associated with source address. 501 This field MUST be transmitted as 32 (/32). An Invalid 502 Sprefix Len Notification SHOULD be sent upon receipt 503 of any other value. 505 Group Address 506 The group address the active source has sent data to. 508 Source Address 509 The IP address of the active source. 511 Multiple SA TLVs MAY appear in the same message and can be batched 512 for efficiency at the expense of data latency. This would typically 513 occur on intermediate forwarding of SA messages. 515 16.2.2. IPv4 Source-Active Request TLV 517 The Source-Active Request is used to request SA-state from a caching 518 MSDP peer. If an RP in a domain receives a PIM Join message for a 519 group, creates (*,G) state and wants to know all active sources for 520 group G, and it has been configured to peer with an SA-state caching 521 peer, it may send an SA-Request message for the group. 523 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 1 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | 2 | 8 | Gprefix Len | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | Group Address Prefix | 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 530 Type 531 IPv4 Source-Active Request TLV is type 2. 533 Gprefix Len 534 The route prefix length associated with the group address prefix. 536 Group Address 537 The group address the MSDP peer is requesting. 539 16.2.3. IPv4 Source-Active Response TLV 541 The Source-Active Response is sent in response to a Source-Active 542 Request message. The Source-Active Response message has the same 543 format as a Source-Active message but does not allow encapsulation of 544 multicast data. 546 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 1 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | 3 | x | .... | 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 Type 552 IPv4 Source-Active Response TLV is type 3. 554 Length x 555 Is the length of the control information in the message. x is 8 556 octets (for the first two 32-bit quantities) plus 12 times Entry 557 Count octets. 559 16.2.4. KeepAlive TLV 561 A KeepAlive TLV is sent to an MSDP peer if and only if there were no 562 MSDP messages sent to the peer after a period of time. This message 563 is necessary for the active connect side of the MSDP connection. The 564 passive connect side of the connection knows that the connection will 565 be reestablished when a TCP SYN packet is sent from the active 566 connect side. However, the active connect side will not know when the 567 passive connect side goes down. Therefore, the KeepAlive timeout will 568 be used to reset the TCP connection. 570 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 1 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 | 4 | 3 | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 The length of the message is 3 octets which encompasses the one octet 576 Type field and the two octet Length field. 578 16.2.5. Notification TLV 580 A Notification message is sent when an error condition is detected, 581 and has the following form: 583 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 1 584 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 585 | 5 | x + 5 |O| Error Code | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 | Error subcode | ... | 588 +-+-+-+-+-+-+-+-+ | 589 | Data | 590 | ... | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 Type 594 The Notification TLV is type 5. 596 Length 597 Length is a two octet field with value x + 5, where x is 598 the length of the notification data field. 600 O-bit 601 Open-bit. If clear, the connection will be closed. 603 Error code 604 This 7-bit unsigned integer indicates the type of Notification. 605 The following Error Codes have been defined: 607 Error Code Symbolic Name Reference 609 1 Message Header Error Section 17.1 610 2 SA-Request Error Section 17.2 611 3 SA-Message/SA-Response Error Section 17.3 612 4 Hold Timer Expired Section 17.4 613 5 Finite State Machine Error Section 17.5 614 6 Notification Section 17.6 615 7 Cease Section 17.7 617 Error subcode: 618 This one-octet unsigned integer provides more specific information 619 about the reported error. Each Error Code may have one or more Error 620 Subcodes associated with it. If no appropriate Error Subcode is 621 defined, then a zero (Unspecific) value is used for the Error Subcode 622 field, and the O-bit must be cleared (i.e. the connection will be 623 closed). The used notation in the error description below is: MC = 624 Must Close connection = O-bit clear; CC = Can Close connection = 625 O-bit might be cleared. 627 Message Header Error subcodes: 629 0 - Unspecific (MC) 630 2 - Bad Message Length (MC) 631 3 - Bad Message Type (CC) 633 SA-Request Error subcodes: 635 0 - Unspecific (MC) 636 1 - Does not cache SA (MC) 637 2 - Invalid Group (MC) 639 SA-Message/SA-Response Error subcodes 641 0 - Unspecific (MC) 642 1 - Invalid Entry Count (CC) 643 2 - Invalid RP Address (MC) 644 3 - Invalid Group Address (MC) 645 4 - Invalid Source Address (MC) 646 5 - Invalid Sprefix Length (MC) 647 6 - Looping SA (Self is RP) (MC) 648 7 - Unknown Encapsulation (MC) 649 8 - Administrative Scope Boundary Violated (MC) 651 Hold Timer Expired subcodes (the O-bit is always clear): 653 0 - Unspecific (MC) 655 Finite State Machine Error subcodes: 657 0 - Unspecific (MC) 658 1 - Unexpected Message Type FSM Error (MC) 660 Notification subcodes (the O-bit is always clear): 662 0 - Unspecific (MC) 664 Cease subcodes (the O-bit is always clear): 666 0 - Unspecific (MC) 668 17. MSDP Error Handling 670 This section describes actions to be taken when errors are detected 671 while processing MSDP messages. MSDP Error Handling is similar to 672 that of BGP [RFC1771]. 674 When any of the conditions described here are detected, a 675 Notification message with the indicated Error Code, Error Subcode, 676 and Data fields is sent. In addition, the MSDP connection might be 677 closed. If no Error Subcode is specified, then a zero (Unspecific) 678 must be used. 680 The phrase "the MSDP connection is closed" means that the transport 681 protocol connection has been closed and that all resources for that 682 MSDP connection have been deallocated. 684 17.1. Message Header Error Handling 686 All errors detected while processing the Message Header are indicated 687 by sending the Notification message with Error Code Message Header 688 Error. The Error Subcode describes the specific nature of the error. 689 The Data field contains the erroneous Message (including the message 690 header). 692 If the Length field of the message header is less than 4 or greater 693 than 1400, or the length of a KeepAlive message is not equal to 3, 694 then the Error Subcode is set to Bad Message Length. 696 If the Type field of the message header is not recognized, then the 697 Error Subcode is set to Bad Message Type. 699 17.2. SA-Request Error Handling 701 The SA-Request Error code is used to signal the receipt of a SA 702 request at a non-caching MSDP peer, or at a caching MSDP peer when an 703 invalid group address requested. 705 When a non-caching MSDP peer receives an SA-Request, it returns the 706 following notification: 708 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 1 709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 | 5 | 16 |O| 2 | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | 1 | Reserved | Gprefix Len | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | Gprefix | 715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 716 | Group Address | 717 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 718 y.fi 720 If a caching MSDP peer receives a request for an invalid 721 group, it returns the following notification: 723 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 1 724 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 | 5 | 16 |O| 2 | 726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 | 2 | Reserved | Gprefix Len | 728 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 729 | Gprefix | 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 731 | Invalid Group Address | 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 734 17.3. SA-Message/SA-Response Error Handling 736 The SA-Message/SA-Response Error code is used to signal the receipt 737 of a erroneous SA Message at an MSDP peer, or the receipt of an SA- 738 Response Message by a peer that did not issue a SA-Request. It has 739 the following form: 741 17.3.1. Invalid Entry Count (IEC) 743 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 1 744 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 745 | 5 | 6 |O| 3 | 746 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 747 | 1 | IEC | 748 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 750 17.3.2. Invalid RP Address 752 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 1 753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 754 | 5 | 12 |O| 3 | 755 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 756 | 2 | Reserved | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 | Invalid RP Address | 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 761 17.3.3. Invalid Group Address 763 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 1 764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 | 5 | 12 |O| 3 | 766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 | 3 | Reserved | 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 | Invalid Group Address | 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 772 17.3.4. Invalid Source Address 774 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 1 775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 776 | 5 | 12 |O| 3 | 777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 778 | 4 | Reserved | 779 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 780 | Invalid Source Address | 781 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 783 17.3.5. Invalid Sprefix Length (ISL) 785 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 1 786 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 787 | 5 | 6 |O| 3 | 788 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 789 | 5 | ISL | 790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 792 17.3.6. Looping SAs (Self is RP in received SA) 794 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 1 795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 796 | 5 | x + 5 |O| 3 | 797 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 798 | 6 | Looping SA Message .... 799 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 801 Length x 802 x is the length of the looping SA message contained in the data 803 field of the Notification message. 805 17.3.7. Unknown Encapsulation 807 This notification is sent on receipt of SA data that is encapsulated 808 in an unknown encapsulation type. See section 18 for known 809 encapsulations. 811 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 1 812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 813 | 5 | x + 5 |O| 3 | 814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 815 | 7 | SA Message .... 816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 818 Length x 819 x is the length of the SA message (which contained data which 820 was encapsulated in some unknown way) that is contained in the 821 data field of the Notification message. 823 17.3.8. Administrative Scope Boundary Violated 825 This notification is used when an SA message is received for a group 826 G from a peer which is across an administrative scope boundary for G. 828 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 1 829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 830 | 5 | 16 |O| 3 | 831 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 832 | 8 | Reserved | Gprefix Len | 833 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 834 | Gprefix | 835 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 836 | Group Address | 837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 839 17.4. Hold Time Expired 841 If a system does not receive successive KeepAlive or any SA Message 842 and/or Notification messages within the period specified in the Hold 843 Timer, the notification message with Hold Timer Expired Error Code 844 and no additional data MUST be sent and the MSDP connection closed. 846 17.5. Finite State Machine Error Handling 848 Any error detected by the MSDP Finite State Machine (e.g., receipt of 849 an unexpected event) is indicated by sending the Notification message 850 with Error Code Finite State Machine Error. 852 17.6. Notification Message Error Handling 854 If a node sends a Notification message, and there is an error in that 855 message, and the O-bit of that message is not clear, a Notification 856 with O-bit clear, Error Code of Notification Error, and subcode 857 Unspecific must be sent. In addition, the Data field must include 858 the Notification message that triggered the error. However, if the 859 erroneous Notification message had the O-bit clear, then any error, 860 such as an unrecognized Error Code or Error Subcode, should be 861 noticed, logged locally, and brought to the attention of the 862 administrator of the remote node. 864 17.7. Cease 866 In absence of any fatal errors (that are indicated in this section), 867 an MSDP node may choose at any given time to close its MSDP 868 connection by sending the Notification message with Error Code Cease. 869 However, the Cease Notification message MUST NOT be used when a fatal 870 error indicated by this section does exist. 872 18. SA Data Encapsulation 874 This section describes UDP, GRE, and TCP encapsulation of SA data. 875 Encapsulation type is a configuration option. 877 18.1. UDP Data Encapsulation 879 Data packets MAY be encapsulated in UDP. In this case, the UDP 880 pseudo-header has the following form: 882 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 1 883 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 884 | Source Port | Destination Port | 885 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 886 | Length | Checksum | 887 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 888 | Origin RP Address | 889 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 891 The Source port, Destination Port, Length, and Checksum are used 892 according to RFC 768. Source and Destination ports are known via an 893 implementation-specific method (e.g. per-peer configuration). 895 Checksum 896 The checksum is computed according to RFC 768 [RFC768]. 898 Originating RP Address 899 The Originating RP Address is the address of the RP sending 900 the encapsulated data. 902 18.2. GRE Encapsulation 904 MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP- 905 GRE-ProtocolType]. The GRE header and payload packet have the 906 following form: 908 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 1 909 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 910 |C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\ 911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header 912 | Checksum (optional) | Reserved1 |/ 913 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 914 | Originating RP IPv4 Address |\ 915 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload 916 | (S,G) Data Packet .... / 917 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 919 18.2.1. Encapsulation and Path MTU Discovery [RFC1191] 921 Existing implementations of GRE, when using IPv4 as the Delivery 922 Header, do not implement Path MTU discovery and do not set the Don't 923 Fragment bit in the Delivery Header. This can cause large packets to 924 become fragmented within the tunnel and reassembled at the tunnel 925 exit (independent of whether the payload packet is using PMTU). If a 926 tunnel entry point were to use Path MTU discovery, however, that 927 tunnel entry point would also need to relay ICMP unreachable error 928 messages (in particular the "fragmentation needed and DF set" code) 929 back to the originator of the packet, which is not required by the 930 GRE specification [GRE]. Failure to properly relay Path MTU 931 information to an originator can result in the following behavior: 932 the originator sets the don't fragment bit, the packet gets dropped 933 within the tunnel, but since the originator doesn't receive proper 934 feedback, it retransmits with the same PMTU, causing subsequently 935 transmitted packets to be dropped. 937 18.3. TCP Data Encapsulation 939 As discussed earlier, encapsulation of data in SA messages MAY be 940 supported for backwards compatibility with legacy MSDP peers. 942 19. Security Considerations 944 An MSDP implementation MAY use IPsec [RFC1825] or keyed MD5 [RFC1828] 945 to secure control messages. When encapsulating SA data in GRE, 946 security should be relatively similar to security in a normal IPv4 947 network, as routing using GRE follows the same routing that IPv4 uses 948 natively. Route filtering will remain unchanged. However packet 949 filtering at a firewall requires either that a firewall look inside 950 the GRE packet or that the filtering is done on the GRE tunnel 951 endpoints. In those environments in which this is considered to be a 952 security issue it may be desirable to terminate the tunnel at the 953 firewall. 955 20. Acknowledgments 957 The authors would like to thank Bill Nickless, John Meylor, Liming 958 Wei, Manoj Leelanivas, Mark Turner, John Zwiebel, and Cristina 959 Radulescu-Banu for their design feedback and comments. In addition to 960 many other contributions, Tom Pusateri helped to clarify the 961 connection state machine, Dave Thaler helped to clarify the 962 Notification message types, and Bill Fenner helped to clarify the 963 Peer-RPF rules. 965 21. Author's Address: 967 Dino Farinacci 968 Procket Networks 969 3850 No. First St., Ste. C 970 San Jose, CA 95134 971 Email: dino@procket.com 973 Yakov Rehkter 974 Cisco Systems, Inc. 975 170 Tasman Drive 976 San Jose, CA, 95134 977 Email: yakov@cisco.com 979 Peter Lothberg 980 Sprint 981 VARESA0104 982 12502 Sunrise Valley Drive 983 Reston VA, 20196 984 Email: roll@sprint.net 986 Hank Kilmer 987 Email: hank@rem.com 989 Jeremy Hall 990 UUnet Technologies 991 3060 Williams Drive 992 Fairfax, VA 22031 993 Email: jhall@uu.net 995 David Meyer 996 Cisco Systems, Inc. 997 170 Tasman Drive 998 San Jose, CA, 95134 999 Email: dmm@cisco.com 1001 22. REFERENCES 1003 [GRE] Farinacci, D., et al., "Generic Routing Encapsulation 1004 (GRE)", draft-meyer-gre-update-03.txt, January, 1005 2000. Work in Progress. 1007 [RFC768] Postel, J. "User Datagram Protocol", RFC 768, August, 1008 1980. 1010 [RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery", 1011 RFC 1191, November 1990. 1013 [RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 1014 (BGP-4)", RFC 1771, March 1995. 1016 [RFC1825] Atkinson, R., "Security Architecture for the Internet 1017 Protocol", RFC 1825, August, 1995. 1019 [RFC1828] P. Metzger and W. Simpson, "IP Authentication using 1020 Keyed MD5", RFC 1828, August, 1995. 1022 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 1023 Requirement Levels", RFC 2119, March, 1997. 1025 [RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., 1026 "Multiprotocol Extensions for BGP-4", RFC 2283, 1027 February 1998. 1029 [RFC2362] Estrin D., et al., "Protocol Independent Multicast - 1030 Sparse Mode (PIM-SM): Protocol Specification", RFC 1031 2362, June 1998. 1033 [RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC 1034 2365, July, 1998.