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All references will be assumed normative when checking for downward references. ** There are 9 instances of too long lines in the document, the longest one being 2 characters in excess of 72. == There are 5 instances of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. == There are 2 instances of lines with private range IPv4 addresses in the document. If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year == Line 2733 has weird spacing: '...RIBs-In and t...' == 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: The information carried by the AdvertisementPath attribute is checked for ITAD loops. ITAD loop detection is done by scanning the full AdvertisementPath, and checking that the ITAD number of the local ITAD does not appear in the AdvertisementPath. If the local ITAD number appears in the AdvertisementPath, then the route MAY be stored in the Adj-TRIB-In, but unless the LS is configured to accept routes with its own ITAD in the advertisement path, the route MUST not be passed to the TRIP Decision Process. The operation of an LS that is configured to accept routes with its own ITAD number in the advertisement path are outside the scope of this document. -- 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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'8') (Obsoleted by RFC 3261, RFC 3262, RFC 3263, RFC 3264, RFC 3265) ** Obsolete normative reference: RFC 2373 (ref. '10') (Obsoleted by RFC 3513) ** Obsolete normative reference: RFC 2434 (ref. '11') (Obsoleted by RFC 5226) ** Obsolete normative reference: RFC 2401 (ref. '12') (Obsoleted by RFC 4301) ** Obsolete normative reference: RFC 2402 (ref. '13') (Obsoleted by RFC 4302, RFC 4305) ** Obsolete normative reference: RFC 2406 (ref. '14') (Obsoleted by RFC 4303, RFC 4305) ** Obsolete normative reference: RFC 2409 (ref. '15') (Obsoleted by RFC 4306) Summary: 12 errors (**), 0 flaws (~~), 6 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPTEL Working Group J. Rosenberg, dynamicsoft 3 Internet Draft H. Salama, Cisco Systems 4 draft-ietf-iptel-trip-07.txt M. Squire, WindWire 5 June 2001 6 Expiration Date: December 2001 8 Telephony Routing over IP (TRIP) 10 Status of this Memo 12 This document is an Internet-Draft and is in full conformance with 13 all provisions of Section 10 of RFC2026. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that other 17 groups may also distribute working documents as Internet-Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt. 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 Abstract 32 This document presents the Telephony Routing over IP (TRIP). TRIP is 33 a policy driven inter-administrative domain protocol for advertising 34 the reachability of telephony destinations between location servers, 35 and for advertising attributes of the routes to those destinations. 36 TRIP's operation is independent of any signaling protocol, hence TRIP 37 can serve as the telephony routing protocol for any signaling 38 protocol. 40 The Border Gateway Protocol (BGP-4) is used to distribute routing 41 information between administrative domains. TRIP is used to 42 distribute telephony routing information between telephony 43 administrative domains. The similarity between the two protocols is 44 obvious, and hence TRIP is modeled after BGP-4. 46 Table of Contents 48 1 Terminology and Definitions .............................. 3 49 2 Introduction ............................................. 4 50 3 Summary of Operation ..................................... 5 51 3.1 Peering Session Establishment and Maintenance ............ 6 52 3.2 Database Exchanges ....................................... 6 53 3.3 Internal Versus External Synchronization ................. 6 54 3.4 Advertising TRIP Routes .................................. 7 55 3.5 Telephony Routing Information Bases ...................... 8 56 4 Message Formats .......................................... 9 57 4.1 Message Header Format .................................... 9 58 4.2 OPEN Message Format ...................................... 10 59 4.3 UPDATE Message Format .................................... 15 60 4.4 KEEPALIVE Message Format ................................ 22 61 4.5 NOTIFICATION Message Format ............................. 23 62 5 TRIP Attributes ......................................... 24 63 5.1 WithdrawnRoutes .......................................... 24 64 5.2 ReachableRoutes .......................................... 28 65 5.3 NextHopServer ........................................... 29 66 5.4 AdvertisementPath ....................................... 31 67 5.5 RoutedPath ............................................... 35 68 5.6 AtomicAggregate ......................................... 37 69 5.7 LocalPreference ......................................... 38 70 5.8 MultiExitDisc ............................................ 39 71 5.9 Communities .............................................. 40 72 5.10 ITAD Topology .......................................... 42 73 5.11 ConvertedRoute ........................................... 44 74 5.12 Considerations for Defining New TRIP Attributes ......... 45 75 6 TRIP Error Detection and Handling ....................... 46 76 6.1 Message Header Error Detection and Handling ............. 46 77 6.2 OPEN Message Error Detection and Handling ............... 47 78 6.3 UPDATE Message Error Detection and Handling ............. 48 79 6.4 NOTIFICATION Message Error Detection and Handling ....... 49 80 6.5 Hold Timer Expired Error Handling ....................... 49 81 6.6 Finite State Machine Error Handling ..................... 49 82 6.7 Cease ................................................... 50 83 6.8 Connection Collision Detection .......................... 50 84 7 TRIP Version Negotiation ................................ 51 85 8 TRIP Capability Negotiation ............................. 51 86 9 TRIP Finite State Machine ............................... 51 87 10 UPDATE Message Handling ................................. 56 88 10.1 Flooding Process ........................................ 57 89 10.2 Decision Process ........................................ 60 90 10.3 Update-Send Process ..................................... 64 91 10.4 Route Selection Criteria ................................ 69 92 10.5 Originating TRIP Routes ................................. 69 93 11 TRIP Transport .......................................... 70 94 12 ITAD Topology ........................................... 70 95 13 IANA Considerations ...................................... 70 96 13.1 TRIP Capabilities ....................................... 70 97 13.2 TRIP Attributes ........................................ 71 98 13.3 Destination Address Families ............................ 71 99 13.4 TRIP Application Protocols .............................. 71 100 13.5 ITAD Numbers ............................................ 72 101 14 Security Considerations ................................. 72 102 Appendix 1: TRIP FSM State Transitions and Actions ...... 73 103 Appendix 2: Implementation Recommendations .............. 75 104 Acknowledgments .......................................... 77 105 References ............................................... 77 106 Authors' Addresses ....................................... 78 107 Intellectual Property Notice ............................. 79 108 Full Copyright Statement ................................. 80 110 1. Terminology and Definitions 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in RFC 2119 [1]. 116 A framework for a Telephony Routing over IP (TRIP) is described in 117 [2]. We assume the reader is familiar with the framework and 118 terminology of [2]. We define and use the following terms in addition 119 to those defined in [2]. 121 Telephony Routing Information Base (TRIB): The database of reachable 122 telephony destinations built and maintained at an LS as a result of 123 its participation in TRIP. 125 IP Telephony Administrative Domain (ITAD): The set of resources 126 (gateways, location servers, etc.) under the control of a single 127 administrative authority. End users are customers of an ITAD. 129 Less/More Specific Route: A route X is said to be less specific than 130 a route Y if every destination in Y is also a destination in X, and X 131 and Y are not equal. In this case, Y is also said to be more specific 132 than X. 134 Peers: Two LSs that share a logical association (a transport 135 connection). If the LSs are in the same ITAD, they are internal 136 peers. Otherwise, they are external peers. The logical association 137 between two peer LSs is called a peering session. 139 Telephony Routing Information Protocol (TRIP): The protocol defined 140 in this specification. The function of TRIP is to advertise the 141 reachability of telephony destinations, attributes associated with 142 the destinations, as well as the attributes of the path towards those 143 destinations. 145 TRIP destination: TRIP can be used to manage routing tables for 146 multiple protocols (SIP, H323, etc.). In TRIP, a destination is the 147 combination of (a) a set of addresses (given by an address family and 148 address prefix), and (b) an application protocol (SIP, H323, etc). 150 2. Introduction 152 The gateway location and routing problem has been introduced in [2]. 153 It is considered one of the more difficult problems in IP telephony. 154 The selection of an egress gateway for a telephony call, traversing 155 an IP network towards an ultimate destination in the PSTN, is driven 156 in large part by the policies of the various parties along the path, 157 and by the relationships established between these parties. As such, 158 a global directory of egress gateways in which users look up 159 destination phone numbers is not a feasible solution. Rather, 160 information about the availability of egress gateways is exchanged 161 between providers, and subject to policy, made available locally and 162 then propagated to other providers in other ITADs, thus creating 163 routes towards these egress gateways. This would allow each provider 164 to create its own database of reachable phone numbers and the 165 associated routes - such a database could be very different for each 166 provider depending on policy. 168 TRIP is an inter-domain (i.e., inter-ITAD) gateway location and 169 routing protocol. The primary function of a TRIP speaker, called a 170 location server (LS), is to exchange information with other LSs. This 171 information includes the reachability of telephony destinations, the 172 routes towards these destinations, and information about gateways 173 towards those telephony destinations residing in the PSTN. The TRIP 174 requirements are set forth in [2]. 176 LSs exchange sufficient routing information to construct a graph of 177 ITAD connectivity so that routing loops may be prevented. In 178 addition, TRIP can be used to exchange attributes necessary to 179 enforce policies and to select routes based on path or gateway 180 characteristics. This specification defines TRIP's transport and 181 synchronization mechanisms, its finite state machine, and the TRIP 182 data. This specification defines the basic attributes of TRIP. The 183 TRIP attribute set is extendible, so additional attributes may be 184 defined in future drafts. 186 TRIP is modeled after the Border Gateway Protocol 4 (BGP-4) [3] and 187 enhanced with some link state features as in the Open Shortest Path 188 First (OSPF) protocol [4], IS-IS [5], and the Server Cache 189 Synchronization Protocol (SCSP) [6]. TRIP uses BGP's inter-domain 190 transport mechanism, BGP's peer communication, BGP's finite state 191 machine, and similar formats and attributes as BGP. Unlike BGP 192 however, TRIP permits generic intra-domain LS topologies, which 193 simplifies configuration and increases scalability in contrast to 194 BGP's full mesh requirement of internal BGP speakers. TRIP uses an 195 intra-domain flooding mechanism similar to that used in OSPF [4], 196 IS-IS [5], and SCSP [6]. 198 TRIP permits aggregation of routes as they are advertised through the 199 network. TRIP does not define a specific route selection algorithm. 201 TRIP runs over a reliable transport protocol. This eliminates the 202 need to implement explicit fragmentation, retransmission, 203 acknowledgment, and sequencing. The error notification mechanism used 204 in TRIP assumes that the transport protocol supports a graceful 205 close, i.e., that all outstanding data will be delivered before the 206 connection is closed. 208 TRIP's operation is independent of any particular telephony signaling 209 protocol. Therefore, TRIP can be used as the routing protocol for any 210 of these protocols, e.g., H.323 [7] and SIP [8]. 212 The LS peering topology is independent of the physical topology of 213 the network. In addition, the boundaries of ITAD are independent of 214 the boundaries of the layer 3 routing autonomous systems. Neither 215 internal nor external TRIP peers need be physically adjacent. 217 3. Summary of Operation 219 This section summarizes the operation of TRIP. Details are provided 220 in later sections. 222 3.1. Peering Session Establishment and Maintenance 224 Two peer LSs form a transport protocol connection between one 225 another. They exchange messages to open and confirm the connection 226 parameters, and to negotiate the capabilities of each LS as well as 227 the type of information to be advertised over this connection. 229 KeepAlive messages are sent periodically to ensure adjacent peers are 230 operational. Notification messages are sent in response to errors or 231 special conditions. If a connection encounters an error condition, a 232 Notification message is sent and the connection is closed. 234 3.2. Database Exchanges 236 Once the peer connection has been established, the initial data flow 237 is a dump of all routes relevant to the new peer (In case of an 238 external peer, all routes in the LS's Adj-TRIB-Out for that external 239 peer. In case of an internal peer, all routes in the Ext-TRIB and all 240 Adj-TRIBs-In). Note that the different TRIBs are defined in Section 241 3.5. 243 Incremental updates are sent as the TRIP routing tables (TRIBs) 244 change. TRIP does not require periodic refresh of the routes. 245 Therefore, an LS must retain the current version of all routing 246 entries. 248 If a particular ITAD has multiple LSs and is providing transit 249 service for other ITADs, then care must be taken to ensure a 250 consistent view of routing within the ITAD. When synchronized the 251 TRIP routing tables, i.e., the Loc-TRIBs, of all internal peers are 252 identical. 254 3.3. Internal Versus External Synchronization 256 As with BGP, TRIP distinguishes between internal and external peers. 257 Within an ITAD, internal TRIP uses link-state mechanisms to flood 258 database updates over an arbitrary topology. Externally, TRIP uses 259 point-to-point peering relationships to exchange database 260 information. 262 To achieve internal synchronization, internal peer connections are 263 configured between LSs of the same ITAD such that the resulting 264 intra-domain LS topology is connected and sufficiently redundant. 265 This is different from BGP's approach that requires all internal 266 peers to be connected in a full mesh topology, which may result in 267 scaling problems. When an update is received from an internal peer, 268 the routes in the update are checked to determine if they are newer 269 than the version already in the database. Newer routes are then 270 flooded to all other peers in the same domain. 272 3.4. Advertising TRIP Routes 274 In TRIP, a route is defined as the combination of (a) a set of 275 destination addresses (given by an address family indicator and an 276 address prefix), and (b) an application protocol (e.g. SIP, H323, 277 etc.). Generally, there are additional attributes associated with 278 each route (for example, the next-hop server). 280 TRIP routes are advertised between a pair of LSs in UPDATE messages. 281 The destination addresses are included in the ReachableRoutes 282 attribute of the UPDATE, while other attributes describe things like 283 the path or egress gateway. 285 If an LS chooses to advertise the TRIP route, it may add to or modify 286 the attributes of the route before advertising it to a peer. TRIP 287 provides mechanisms by which an LS can inform its peer that a 288 previously advertised route is no longer available for use. There are 289 three methods by which a given LS can indicate that a route has been 290 withdrawn from service: 292 - Include the route in the WithdrawnRoutes Attribute in an UPDATE 293 message, thus marking the associated destinations as being no 294 longer available for use. 295 - Advertise a replacement route with the same set of destinations 296 in the ReachableRoutes Attribute. 297 - For external peers where flooding is not in use, the LS-to-LS 298 peer connection can be closed, which implicitly removes from 299 service all routes which the pair of LSs had advertised to each 300 other over that peer session. Note that terminating an internal 301 peering session does not necessarily remove the routes advertised 302 by the peer LS as the same routes may have been received from 303 multiple internal peers because of flooding. If an LS determines 304 that the another internal LS is no longer active (from the ITAD 305 Topology attributes of the UPDATE messages from other internal 306 peers), then it MUST remove all routes originated into the LS by 307 that LS and rerun its decision process. 309 3.5. Telephony Routing Information Bases 311 A TRIP LS processes three types of routes: 313 - External routes: An external route is a route received from an 314 external peer LS 315 - Internal routes: An internal route is a route received from an 316 internal LS in the same ITAD. 317 - Local routes: A local route is a route locally injected into 318 TRIP, e.g. by configuration or by route redistribution from 319 another routing protocol. 321 The Telephony Routing Information Base (TRIB) within an LS consists 322 of four distinct parts: 324 - Adj-TRIBs-In: The Adj-TRIBs-In store routing information that has 325 been learned from inbound UPDATE messages. Their contents 326 represent TRIP routes that are available as an input to the 327 Decision Process. These are the "unprocessed" routes received. 328 The routes from each external peer LS and each internal LS are 329 maintained in this database independently, so that updates from 330 one peer do not affect the routes received from another LS. Note 331 that there is an Adj-TRIBs-In for every LS within the domain, 332 even those with which the LS is not directly peered. 333 - Ext-TRIB: There is only one Ext-TRIB database per LS. The LS runs 334 the route selection algorithm on all external routes (stored in 335 the Adj-TRIBs-In of the external peers) and local routes (may be 336 stored in an Adj-TRIB-In representing the local LS) and selects 337 the best route for a given destination and stores it in the Ext- 338 TRIB. The use of Ext-TRIB will be explained further in Section 339 10.3.1 340 - Loc-TRIB: The Loc-TRIB contains the local TRIP routing 341 information that the LS has selected by applying its local 342 policies to the routing information contained in its Adj-TRIBs-In 343 of internal LSs and the Ext-TRIB. 344 - Adj-TRIBs-Out: The Adj-TRIBs-Out store the information that the 345 local LS has selected for advertisement to its external peers. 346 The routing information stored in the Adj-TRIBs-Out will be 347 carried in the local LS's UPDATE messages and advertised to its 348 peers. 350 Figure 1 illustrates the relationship between the three parts of the 351 routing information base. 353 Loc-TRIB 354 ^ 355 | 356 Decision Process 357 ^ ^ | 358 | | | 359 Adj-TRIBs-In | V 360 (Internal LSs) | Adj-TRIBs-Out 361 | 362 | 363 | 364 Ext-TRIB 365 ^ ^ 366 | | 367 Adj-TRIB-In Local Routes 368 (External Peers) 370 Figure 1: TRIB Relationships 372 Although the conceptual model distinguishes between Adj-TRIBs-In, 373 Loc-TRIB, and Adj-TRIBs-Out, this neither implies nor requires that 374 an implementation must maintain three separate copies of the routing 375 information. The choice of implementation (for example, 3 copies of 376 the information vs. 1 copy with pointers) is not constrained by the 377 protocol. 379 4. Message Formats 381 This section describes message formats used by TRIP. Messages are 382 sent over a reliable transport protocol connection. A message MUST be 383 processed only after it is entirely received. The maximum message 384 size is 4096 octets. All implementations MUST support this maximum 385 message size. The smallest message that MAY be sent consists of a 386 TRIP header without a data portion, or 3 octets. 388 4.1. Message Header Format 390 Each message has a fixed-size header. There may or may not be a data 391 portion following the header depending on the message type. The 392 layout of the header fields is shown in Figure 2. 394 0 1 2 395 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 396 +--------------+----------------+---------------+ 397 | Length | Type | 398 +--------------+----------------+---------------+ 400 Figure 2: TRIP Header 402 Length: 403 This 2-octet unsigned integer indicates the total length of the 404 message, including the header, in octets. Thus, it allows one to 405 locate in the transport-level stream the beginning of the next 406 message. The value of the Length field must always be at least 3 and 407 no greater than 4096, and may be further constrained depending on the 408 message type. No padding of extra data after the message is allowed, 409 so the Length field must have the smallest value possible given the 410 rest of the message. 412 Type: 413 This 1-octet unsigned integer indicates the type code of the message. 414 The following type codes are defined: 416 1 - OPEN 417 2 - UPDATE 418 3 - NOTIFICATION 419 4 - KEEPALIVE 421 4.2. OPEN Message Format 423 After a transport protocol connection is established, the first 424 message sent by each side is an OPEN message. If the OPEN message is 425 acceptable, a KEEPALIVE message confirming the OPEN is sent back. 426 Once the OPEN is confirmed, UPDATE, KEEPALIVE, and NOTIFICATION 427 messages may be exchanged. 429 The minimum length of the OPEN message is 14 octets (including 430 message header). OPEN messages not meeting this minimum requirement 431 are handled as defined in Section 6.2. 433 In addition to the fixed-size TRIP header, the OPEN message contains 434 the following fields: 436 0 1 2 3 437 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 1 438 +---------------+---------------+--------------+----------------+ 439 | Version | Reserved | Hold Time | 440 +---------------+---------------+--------------+----------------+ 441 | My ITAD | 442 +---------------+---------------+--------------+----------------+ 443 | TRIP Identifier | 444 +---------------+---------------+--------------+----------------+ 445 | Optional Parameters Len |Optional Parameters (variable)... 446 +---------------+---------------+--------------+----------------+ 447 Figure 3: TRIP OPEN Header 449 Version: 450 This 1-octet unsigned integer indicates the protocol version of the 451 message. The current TRIP version number is 1. 453 Hold Time: 454 This 2-octet unsigned integer indicates the number of seconds that 455 the sender proposes for the value of the Hold Timer. Upon receipt of 456 an OPEN message, an LS MUST calculate the value of the Hold Timer by 457 using the smaller of its configured Hold Time and the Hold Time 458 received in the OPEN message. The Hold Time MUST be either zero or at 459 least three seconds. An implementation MAY reject connections on the 460 basis of the Hold Time. The calculated value indicates the maximum 461 number of seconds that may elapse between the receipt of successive 462 KEEPALIVE and/or UPDATE messages by the sender. 464 This 4-octet unsigned integer indicates the ITAD number of the 465 sender. The ITAD number must be unique for this domain within this 466 confederation of cooperating LSs. 468 ITAD numbers are assigned by IANA as specified in Section 13. This 469 document reserves ITAD number 0. ITAD numbers from 1 to 255 are 470 designated for private use. 472 TRIP Identifier: 473 This 4-octet unsigned integer indicates the TRIP Identifier of the 474 sender. The TRIP Identifier MUST uniquely identify this LS within its 475 ITAD. A given LS MAY set the value of its TRIP Identifier to an IPv4 476 address assigned to that LS. The value of the TRIP Identifier is 477 determined on startup and MUST be the same for all peer connections. 478 When comparing two TRIP identifiers, the TRIP Identifier is 479 interpreted as a numerical 4-octet unsigned integer. 481 Optional Parameters Length: 482 This 2-octet unsigned integer indicates the total length of the 483 Optional Parameters field in octets. If the value of this field is 484 zero, no Optional Parameters are present. 486 Optional Parameters: 487 This field may contain a list of optional parameters, where each 488 parameter is encoded as a triplet. 491 0 1 2 492 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 1 493 +---------------+---------------+--------------+----------------+ 494 | Parameter Type | Parameter Length | 495 +---------------+---------------+--------------+----------------+ 496 | Parameter Value (variable)... 497 +---------------+---------------+--------------+----------------+ 499 Figure 4: Optional Parameter Encoding 501 Parameter Type: 502 This is a 2-octet field that unambiguously identifies individual 503 parameters. 505 Parameter Length: 506 This is a 2-octet field that contains the length of the Parameter 507 Value field in octets. 509 Parameter Value: 510 This is a variable length field that is interpreted according to the 511 value of the Parameter Type field. 513 4.2.1. Open Message Optional Parameters 515 This document defines the following Optional Parameters for the OPEN 516 message. 518 4.2.1.1. Capability Information 520 Capability Information uses Optional Parameter type 1. This is an 521 optional parameter used by an LS to convey to its peer the list of 522 capabilities supported by the LS. This permits an LS to learn of the 523 capabilities of its peer LSs. Capability negotiation is defined in 524 Section 8. 526 The parameter contains one or more triples , where each triple is encoded as 528 shown below: 530 0 1 2 531 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 1 532 +---------------+---------------+--------------+----------------+ 533 | Capability Code | Capability Length | 534 +---------------+---------------+--------------+----------------+ 535 | Capability Value (variable)... 536 +---------------+---------------+--------------+----------------+ 538 Figure 5: Capability Optional Parameter 540 Capability Code: 541 Capability Code is a 2-octet field that unambiguously identifies 542 individual capabilities. 544 Capability Length: 545 Capability Length is a 2-octet field that contains the length of the 546 Capability Value field in octets. 548 Capability Value: 549 Capability Value is a variable length field that is interpreted 550 according to the value of the Capability Code field. 552 Any particular capability, as identified by its Capability Code, may 553 appear more than once within the Optional Parameter. 555 This document reserves Capability Codes 32768-65535 for vendor- 556 specific applications (these are the codes with the first bit of the 557 code value equal to 1). This document reserves value 0. Capability 558 Codes (other than those reserved for vendor specific use) are 559 controlled by IANA. See Section 13 for IANA considerations. 561 The following Capability Codes are defined by this specification: 563 Code Capability 564 1 Route Types Supported 565 2 Send Receive Capability 567 4.2.1.1.1. Route Types Supported 569 The Route Types Supported Capability Code lists the route types 570 supported in this peering session by the transmitting LS. An LS MUST 571 NOT use route types that are not supported by the peer LS in any 572 particular peering session. If the route types supported by a peer 573 are not satisfactory, an LS SHOULD terminate the peering session. The 574 format for a Route Type is: 576 0 1 2 577 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 1 578 +---------------+---------------+--------------+----------------+ 579 | Address Family | Application Protocol | 580 +---------------+---------------+--------------+----------------+ 582 Figure 6: Route Types Supported Capability 584 The Address Family and Application Protocol are as defined in Section 585 5.1.1. Address Family gives the address family being routed (within 586 the ReachableRoutes attribute). The application protocol lists the 587 application for which the routes apply. As an example, a route type 588 for TRIP could be , indicating a set of POTS destinations 589 for the SIP protocol. 591 The Route Types Supported Capability MAY contain multiple route types 592 in the capability. The number of route types within the capability is 593 the maximum number that can fit given the capability length. The 594 Capability Code is 1 and the length is variable. 596 4.2.1.1.2. Send Receive Capability 598 This capability specifies the mode in which the LS will operate with 599 this particular peer. The possible modes are: Send Only mode, Receive 600 Only mode, or Send Receive mode. The default mode is Send Receive 601 mode. 603 In Send Only mode, an LS transmits UPDATE messages to its peer, but 604 the peer MUST NOT transmit UPDATE messages to that LS. If an LS in 605 Send Only mode receives an UPDATE message from its peer, it MUST 606 discard that message, but no further action should be taken. 608 The UPDATE messages sent by an LS in Send Only mode to its intra- 609 domain peer MUST include the ITAD Topology attribute whenever the 610 topology changes. A useful application of an LS in Send Only mode 611 with an external peer is to enable gateway termination services. 613 If a service provider terminates calls to a set of gateways it owns, 614 but never initiates calls, it can set its LSs to operate in Send Only 615 mode, since they only ever need to generate UPDATE messages, not 616 receive them. 618 If an LS in Send Receive mode has a peering session with a peer in 619 Send Only mode, that LS MUST set its route dissemination policy such 620 that it does not send any UPDATE messages to its peer. 622 In Receive Only mode, the LS acts as a passive TRIP listener. It 623 receives and processes UPDATE messages from its peer, but it MUST NOT 624 transmit any UPDATE messages to its peer. This is useful for 625 management stations that wish to collect topology information for 626 display purposes. 628 The behavior of an LS in Send Receive mode is the default TRIP 629 operation specified throughout this document. 631 The Send Receive capability is a 4-octet unsigned numeric value. It 632 can only take one of the following three values: 634 1 - Send Receive mode 635 2 - Send only mode 636 3 - Receive Only mode 638 A peering session MUST NOT be established between two LSs, both of 639 them in either Send Only mode or in Receive Only mode. If a peer LS 640 detects such a capability mismatch when processing an OPEN message, 641 it MUST respond with a NOTIFICATION message and close the peer 642 session. The error code in the NOTIFICATION message must be set to 643 "Capability Mismatch." 645 An LS MUST be configured in the same Send Receive mode for all peers. 647 4.3. UPDATE Message Format 649 UPDATE messages are used to transfer routing information between LSs. 650 The information in the UPDATE packet can be used to construct a graph 651 describing the relationships between the various ITADs. By applying 652 rules to be discussed, routing information loops and some other 653 anomalies can be prevented. 655 An UPDATE message is used to both advertise and withdraw routes from 656 service. An UPDATE message may simultaneously advertise and withdraw 657 TRIP routes. 659 In addition to the TRIP header, the TRIP UPDATE contains a list of 660 routing attributes as shown in Figure 7. There is no padding between 661 routing attributes. 663 +------------------------------------------------+--... 664 | First Route Attribute | Second Route Attribute | ... 665 +------------------------------------------------+--... 667 Figure 7: TRIP UPDATE Format 669 The minimum length of an UPDATE message 11 octets (the TRIP header 670 plus at least the WithdrawnRoutes and ReachableRoutes attributes). 672 4.3.1. Routing Attributes 674 A variable length sequence of routing attributes is present in every 675 UPDATE message. Each attribute is a triple of variable length. 678 0 1 2 3 679 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 1 680 +---------------+---------------+--------------+----------------+ 681 | Attr. Flags |Attr. Type Code| Attr. Length | 682 +---------------+---------------+--------------+----------------+ 683 | Attribute Value (variable) | 684 +---------------+---------------+--------------+----------------+ 686 Figure 8: Routing Attribute Format 688 Attribute Type is a two-octet field that consists of the Attribute 689 Flags octet followed by the Attribute Type Code octet. 691 The Attribute Type Code defines the type of attribute. The basic 692 TRIP-defined Attribute Type Codes are discussed later in this 693 section. Attributes MUST appear in the UPDATE message in numerical 694 order of the Attribute Type Code. An attribute MUST NOT be included 695 more than once in the same UPDATE message. Attribute Flags are used 696 to control attribute processing when the attribute type is unknown. 697 Attribute Flags are further defined in Section 4.3.2. 699 This document reserves Attribute Type Codes 224-255 for vendor- 700 specific applications (these are the codes with the first three bits 701 of the code equal to 1). This document reserves value 0. Attribute 702 Type Codes (other than those reserved for vendor specific use) are 703 controlled by IANA. See Section 13 for IANA considerations. 705 The third and the fourth octets of the route attribute contain the 706 length of the attribute value field in octets. 708 The remaining octets of the attribute represent the Attribute Value 709 and are interpreted according to the Attribute Flags and the 710 Attribute Type Code. The basic supported attribute types, their 711 values, and their uses are defined in this specification. These are 712 the attributes necessary for proper loop free operation of TRIP, both 713 inter-domain and intra-domain. Additional attributes may be defined 714 in future documents. 716 4.3.2. Attribute Flags 718 It is clear that the set of attributes for TRIP will evolve over 719 time. Hence it is essential that mechanisms be provided to handle 720 attributes with unrecognized types. The handling of unrecognized 721 attributes is controlled via the flags field of the attribute. 722 Recognized attributes should be processed according to their specific 723 definition. 725 The following are the attribute flags defined by this specification: 726 Bit Flag 727 0 Well-Known Flag 728 1 Transitive Flag 729 2 Dependent Flag 730 3 Partial Flag 731 4 Link-state Encapsulated Flag 733 The high-order bit (bit 0) of the Attribute Flags octet is the Well- 734 Known Bit. It defines whether the attribute is not well-known (if set 735 to 1) or well-known (if set to 0). Implementations are not required 736 to support not well-known attributes, but MUST support well-known 737 attributes. 739 The second high-order bit (bit 1) of the Attribute Flags octet is the 740 Transitive bit. It defines whether a not well-known attribute is 741 transitive (if set to 1) or non-transitive (if set to 0). For well- 742 known attributes, the Transitive bit MUST be zero on transmit and 743 MUST be ignored on receipt. 745 The third high-order bit (bit 2) of the Attribute Flags octet is the 746 Dependent bit. It defines whether a transitive attribute is dependent 747 (if set to 1) or independent (if set to 0). For well-known attributes 748 and for non-transitive attributes, the Dependent bit is irrelevant, 749 and MUST be set to zero on transmit and MUST be ignored on receipt. 751 The fourth high-order bit (bit 3) of the Attribute Flags octet is the 752 Partial bit. It defines whether the information contained in the not 753 well-known transitive attribute is partial (if set to 1) or complete 754 (if set to 0). For well-known attributes and for non- transitive 755 attributes the Partial bit MUST be set to 0 on transmit and MUST be 756 ignored on receipt. 758 The fifth high-order bit (bit 4) of the Attribute Flags octet is the 759 Link-state Encapsulation bit. This bit is only applicable to certain 760 attributes (ReachableRoutes and WithdrawnRoutes) and determines the 761 encapsulation of the routes within those attributes. If this bit is 762 set, link-state encapsulation is used within the attribute. 763 Otherwise, standard encapsulation is used within the attribute. The 764 Link-state Encapsulation technique is described in Section 4.3.2.4. 765 This flag is only valid on the ReachableRoutes and WithdrawnRoutes 766 attributes. It MUST be cleared on transmit and MUST be ignored on 767 receipt for all other attributes. 769 The other bits of the Attribute Flags octet are unused. They MUST be 770 zeroed on transmit and ignored on receipt. 772 4.3.2.1. Attribute Flags and Route Selection 774 Any recognized attribute can be used as input to the route selection 775 process, although the utility of some attributes in route selection 776 is minimal. 778 4.3.2.2. Attribute Flags and Route Dissemination 780 TRIP provides for two variations of transitivity due to the fact that 781 intermediate LSs need not modify the NextHopServer when propagating 782 routes. Attributes may be non-transitive, dependent transitive, or 783 independent transitive. An attribute cannot be both dependent 784 transitive and independent transitive. 786 Unrecognized independent transitive attributes may be propagated by 787 any intermediate LS. Unrecognized dependent transitive attributes MAY 788 only be propagated if the LS is NOT changing the next-hop server. The 789 transitivity variations permit some unrecognized attributes to be 790 carried end-to-end (independent transitive), some to be carried 791 between adjacent next-hop servers (dependent transitive), and other 792 to be restricted to peer LSs (non- transitive). 794 An LS that passes an unrecognized transitive attribute to a peer MUST 795 set the Partial flag on that attribute. Any LS along a path MAY 796 insert a transitive attribute into a route. If any LS except the 797 originating LS inserts a new independent transitive attribute into a 798 route, then it MUST set the Partial flag on that attribute. If any 799 LS except an LS that modifies the NextHopServer inserts a new 800 dependent transitive attribute into a route, then it MUST set the 801 Partial flag on that attribute. The Partial flag indicates that not 802 every LS along the relevant path has processed and understood the 803 attribute. For independent transitive attributes, the "relevant path" 804 is the path given in the AdvertisementPath attribute. For dependent 805 transitive attributes, the relevant path consists only of those 806 domains thru which this object has passed since the NextHopServer was 807 last modified. The Partial flag in an independent transitive 808 attribute MUST NOT be unset by any other LS along the path. The 809 Partial flag in a dependent transitive attribute MUST be reset 810 whenever the NextHopServer is changed, but MUST NOT be unset by any 811 LS that is not changing the NextHopServer. 813 The rules governing the addition of new non-transitive attributes are 814 defined independently for each non-transitive attribute. Any 815 attribute MAY be updated by an LS in the path. 817 4.3.2.3. Attribute Flags and Route Aggregation 819 Each attribute defines how it is to be handled during route 820 aggregation. 822 The rules governing the handling of unknown attributes are guided by 823 the Attribute Flags. Unrecognized transitive attributes are dropped 824 during aggregation. There should be no unrecognized non-transitive 825 attributes during aggregation because non-transitive attributes must 826 be processed by the local LS in order to be propagated. 828 4.3.2.4. Attribute Flags and Encapsulation 830 Normally attributes have the simple format as described in Section 831 4.3.1. If the Link-state Encapsulation Flag is set, then the two 832 additional fields are added to the attribute header as shown in 833 Figure 9. 835 0 1 2 3 836 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 1 837 +---------------+---------------+--------------+----------------+ 838 | Attr. Flags |Attr. Type Code| Attr. Length | 839 +---------------+---------------+--------------+----------------+ 840 | Originator TRIP Identifier | 841 +---------------+---------------+--------------+----------------+ 842 | Sequence Number | 843 +---------------+---------------+--------------+----------------+ 844 | Attribute Value (variable) | 845 +---------------+---------------+--------------+----------------+ 847 Figure 9: Link State Encapsulation 849 The Originator TRIP ID and Sequence Number are used to control the 850 flooding of routing updates within a collection of servers. These 851 fields are used to detect duplicate and old routes so that they are 852 not further propagated within the servers. The use of these fields is 853 defined in Section 10.1. 855 4.3.3. Mandatory Attributes 857 There are no Mandatory attributes in TRIP. However, there are 858 Conditional Mandatory attributes. A conditional mandatory attribute 859 is an attribute, which MUST be included in an UPDATE message if 860 another attribute is included in that message. For example, if an 861 UPDATE message includes a ReachableRoutes attribute, it MUST include 862 an AdvertisementPath attribute as well. 864 The three base attributes in TRIP are WithdrawnRoutes, 865 ReachableRoutes, and ITAD Topology. Their presence in an UPDATE 866 message is entirely optional and independent of any other attributes. 868 4.3.4. TRIP UPDATE Attributes 870 This section summarizes the attributes that may be carried in an 871 UPDATE message. Attributes MUST appear in the UPDATE message in 872 increasing order of the Attribute Type Code. Additional details are 873 provided in Section 5. 875 4.3.4.1. WithdrawnRoutes 877 This attribute lists a set of routes that are being withdrawn from 878 service. The transmitting LS has determined that these routes should 879 no longer be advertised, and is propagating this information to its 880 peers. 882 4.3.4.2. ReachableRoutes 884 This attribute lists set of routes that are being added to service. 885 These routes will have the potential to be inserted into the Adj- 886 TRIBs-In of the receiving LS and the route selection process will be 887 applied to them. 889 4.3.4.3. NextHopServer 891 This attribute gives the identity of the entity to which messages 892 should be sent along this routed path. It specifies the identity of 893 the next hop server as either a host domain name or an IP address. It 894 MAY optionally specify the UDP/TCP port number for the next hop 895 signaling server. If not specified, then the default port SHOULD be 896 used. The NextHopServer is specific to the set of destinations and 897 application protocol defined in the ReachableRoutes attribute. Note 898 that this is NOT the address to which media (voice, video, etc.) 899 should be transmitted, it is only for the application protocol as 900 given in the ReachableRoutes attribute. 902 4.3.4.4. AdvertisementPath 904 The AdvertisementPath is analogous to the AS_PATH in BGP4 [3]. The 905 attribute records the sequence of domains through which this 906 advertisement has passed. The attribute is used to detect when the 907 routing advertisement is looping. This attribute does NOT reflect the 908 path through which messages following this route would traverse. 909 Since the next-hop need not be modified by each LS, the actual path 910 to the destination might not have to traverse every domain in the 911 AdvertisementPath. 913 4.3.4.5. RoutedPath 915 The RoutedPath attribute is analogous to the AdvertisementPath 916 attribute, except that it records the actual path (given by the list 917 of domains) *to* the destinations. Unlike AdvertisementPath, which is 918 modified each time the route is propagated, RoutedPath is only 919 modified when the NextHopServer attribute changes. Thus, it records 920 the subset of the AdvertisementPath over which messages following 921 this particular route would traverse. 923 4.3.4.6. AtomicAggregate 925 The AtomicAggregate attribute indicates that a route may actually 926 include domains not listed in the RoutedPath. If an LS, when 927 presented with a set of overlapping routes from a peer LS, selects a 928 less specific route without selecting the more specific route, then 929 the LS MUST include the AtomicAggregate attribute with the route. An 930 LS receiving a route with an AtomicAggregate attribute MUST NOT make 931 the set of destinations more specific when advertising it to other 932 LSs. 934 4.3.4.7. LocalPreference 936 The LocalPreference attribute is an intra-domain attribute used to 937 inform other LSs of the local LSs preference for a given route. The 938 preference of a route is calculated at the ingress to a domain and 939 passed as an attribute with that route throughout the domain. Other 940 LSs within the same ITAD use this attribute in their route selection 941 process. This attribute has no significance between domains. 943 4.3.4.8. MultiExitDisc 945 There may be more than one LS peering relationship between 946 neighboring domains. The MultiExitDisc attribute is used by an LS to 947 express a preference for one link between the domains over another 948 link between the domains. The use of the MultiExitDisc attribute is 949 controlled by local policy. 951 4.3.4.9. Communities 953 The Communities attribute is a not well-known attribute used to 954 facilitate and simplify the control of routing information by 955 grouping destinations into communities. 957 4.3.4.10. ITAD Topology 959 The ITAD topology attribute is an intra-domain attribute that is used 960 by LSs to indicate their intra-domain topology to other LSs in the 961 domain. 963 4.3.4.11. ConvertedRoute 965 The ConvertedRoute attribute indicates that an intermediate LS has 966 altered the route by changing the route's Application Protocol. 968 4.4. KEEPALIVE Message Format 970 TRIP does not use any transport-based keep-alive mechanism to 971 determine if peers are reachable. Instead, KEEPALIVE messages are 972 exchanged between peers often enough as not to cause the Hold Timer 973 to expire. A reasonable maximum time between KEEPALIVE messages would 974 be one third of the Hold Time interval. KEEPALIVE messages MUST NOT 975 be sent more than once every 3 seconds. An implementation SHOULD 976 adjust the rate at which it sends KEEPALIVE messages as a function of 977 the negotiated Hold Time interval. 979 If the negotiated Hold Time interval is zero, then periodic KEEPALIVE 980 messages MUST NOT be sent. 982 KEEPALIVE message consists of only message header and has a length of 983 3 octets. 985 4.5. NOTIFICATION Message Format 987 A NOTIFICATION message is sent when an error condition is detected. 988 The TRIP transport connection is closed immediately after sending a 989 NOTIFICATION message 991 In addition to the fixed-size TRIP header, the NOTIFICATION message 992 contains the following fields: 994 0 1 2 3 995 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 1 996 +---------------+---------------+--------------+----------------+ 997 | Error Code | Error Subcode | Data... (variable) 998 +---------------+---------------+--------------+----------------+ 1000 Figure 10: TRIP NOTIFICATION Format 1002 Error Code: 1003 This 1-octet unsigned integer indicates the type of NOTIFICATION. 1004 The following Error Codes have been defined: 1006 Error Code Symbolic Name Reference 1007 1 Message Header Error Section 6.1 1008 2 OPEN Message Error Section 6.2 1009 3 UPDATE Message Error Section 6.3 1010 4 Hold Timer Expired Section 6.5 1011 5 Finite State Machine Error Section 6.6 1012 6 Cease Section 6.7 1014 Error Subcode: 1015 This 1-octet unsigned integer provides more specific information 1016 about the nature of the reported error. Each Error Code may have one 1017 or more Error Subcodes associated with it. If no appropriate Error 1018 Subcode is defined, then a zero (Unspecific) value is used for the 1019 Error Subcode field. 1021 Message Header Error Subcodes: 1022 1 - Bad Message Length. 1023 2 - Bad Message Type. 1025 OPEN Message Error Subcodes: 1026 1 - Unsupported Version Number. 1027 2 - Bad Peer ITAD. 1028 3 - Bad TRIP Identifier. 1029 4 - Unsupported Optional Parameter. 1030 5 - Unacceptable Hold Time. 1031 6 - Unsupported Capability. 1032 7 - Capability Mismatch. 1034 UPDATE Message Error Subcodes: 1035 1 - Malformed Attribute List. 1036 2 - Unrecognized Well-known Attribute. 1037 3 - Missing Well-known Mandatory Attribute. 1038 4 - Attribute Flags Error. 1039 5 - Attribute Length Error. 1040 6 - Invalid Attribute. 1042 Data: 1043 This variable-length field is used to diagnose the reason for the 1044 NOTIFICATION. The contents of the Data field depend upon the Error 1045 Code and Error Subcode. 1047 Note that the length of the data can be determined from the message 1048 length field by the formula: 1050 Data Length = Message Length - 5 1052 The minimum length of the NOTIFICATION message is 5 octets (including 1053 message header). 1055 5. TRIP Attributes 1057 This section provides details on the syntax and semantics of each 1058 TRIP UPDATE attribute. 1060 5.1. WithdrawnRoutes 1062 Conditional Mandatory: False. 1063 Required Flags: Well-known. 1064 Potential Flags: Link-State Encapsulation (when flooding). 1065 TRIP Type Code: 1 1067 The WithdrawnRoutes attribute MUST be included in every UPDATE 1068 message. It specifies a set of routes that are to be removed from 1069 service by the receiving LS(s). The set of routes MAY be empty, 1070 indicated by a length field of zero. 1072 5.1.1. Syntax of WithdrawnRoutes 1074 The WithdrawnRoutes Attribute encodes a sequence of routes in its 1075 value field. The format for individual routes is given in Section 1076 5.1.1.1. The WithdrawnRoutes Attribute lists the individual routes 1077 sequentially with no padding as shown in Figure 11. Each route 1078 includes a length field so that the individual routes within the 1079 attribute can be delineated. 1081 +---------------------+---------------------+... 1082 | WithdrawnRoute1... | WithdrawnRoute2... |... 1083 +---------------------+---------------------+... 1085 Figure 11: WithdrawnRoutes Format 1087 5.1.1.1. Generic TRIP Route Format 1089 The generic format for a TRIP route is given in Figure 12. 1091 0 1 2 3 1092 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 1093 +---------------+---------------+--------------+----------------+ 1094 | Address Family | Application Protocol | 1095 +---------------+---------------+--------------+----------------+ 1096 | Length | Address (variable) ... 1097 +---------------+---------------+--------------+----------------+ 1099 Figure 12: Generic TRIP Route Format 1101 Address Family: 1102 The address family field gives the type of address for the route. Two 1103 address families are defined in this Section: 1105 Code Address Family 1106 1 Decimal Routing Numbers 1107 2 PentaDecimal Routing Numbers 1108 3 E.164 Numbers 1110 This document reserves address family code 0. This document reserves 1111 address family codes 32768-65535 for vendor-specific applications 1112 (these are the codes with the first bit of the code value equal to 1113 1).Additional address families may be defined in the future. 1114 Assignment of address family codes is controlled by IANA. See 1115 Section 13 for IANA considerations. 1117 Application Protocol: 1118 The application protocol gives the protocol for which this routing 1119 table is maintained. The currently defined application protocols are: 1121 Code Protocol 1122 1 SIP 1123 2 H.323-H.225.0-Q.931 1124 3 H.323-H.225.0-RAS 1125 4 H.323-H.225.0-Annex-G 1127 This document reserves application protocol code 0. This document 1128 reserves application protocol codes 32768-65535 for vendor-specific 1129 applications (these are the codes with the first bit of the code 1130 value equal to 1). Additional application protocols may be defined in 1131 the future. Assignment of application protocol codes is controlled by 1132 IANA. See Section 13 for IANA considerations. 1134 Length: 1135 The length of the address field, in bytes. 1137 Address: 1138 This is an address (prefix) of the family type given by Address 1139 Family. The octet length of the address is variable and is determined 1140 by the length field of the route. 1142 5.1.1.2. Decimal Routing Numbers 1144 The Decimal Routing Numbers address family is a super set of all 1145 E.164 numbers, national numbers, local numbers, and private numbers. 1146 It can also be used to represent the decimal routing numbers used in 1147 conjunction with Number Portability in some countries/regions. A set 1148 of telephone numbers is specified by a Decimal Routing Number prefix. 1149 Decimal Routing Number prefixes are represented by a string of 1150 digits, each digit encoded by its ASCII character representation. 1151 This routing object covers all phone numbers starting with this 1152 prefix. The syntax for the Decimal Routing Number prefix is: 1154 Decimal-routing-number = *decimal-digit 1155 decimal-digit = DECIMAL-DIGIT 1156 DECIMAL-DIGIT = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9" 1158 This DECIMAL Routing Number prefix is not bound in length. This 1159 format is similar to the format for a global telephone number as 1160 defined in SIP [8] without visual separators and without the "+" 1161 prefix for international numbers. This format facilitates efficient 1162 comparison when using TRIP to route SIP or H323, both of which use 1163 character based representations of phone numbers. The prefix length 1164 is determined from the length field of the route. The type of Decimal 1165 Routing Number (private, local, national, or international) can be 1166 deduced from the first few digits of the prefix. 1168 5.1.1.3. PentaDecimal Routing Numbers 1170 This address family is used to represent PentaDecimal Routing Numbers 1171 used in conjunction with Number Portability in some 1172 countries/regions. PentaDecimal Routing Number prefixes are 1173 represented by a string of digits, each digit encoded by its ASCII 1174 character representation. This routing object covers all routing 1175 numbers starting with this prefix. The syntax for the PentaDecimal 1176 Routing Number prefix is: 1178 PentaDecimal-routing-number = *pentadecimal-digit 1179 pentadecimal-routing-digit = PENTADECIMAL-DIGIT 1180 PENTADECIMAL-DIGIT = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"| 1181 "8"|"9"|"A"|"B"|"C"|"D"|"E" 1183 Note the difference in alphabets between Decimal Routing Numbers and 1184 PentaDecimal Routing Numbers. A PentaDecimal Routing Number prefix is 1185 not bound in length. 1187 Note that the address family, which suits the routing numbers of a 1188 specific country/region depends on the alphabets used for routing 1189 numbers in that country/region. For example, North American routing 1190 numbers SHOULD use the Decimal Routing Numbers address family, 1191 because their alphabet is limited to the digits "0" through "9". 1192 Another example, in most European countries routing numbers use the 1193 alphabet "0" through "9" and "A" through "F", and hence these 1194 countries SHOULD use the PentaDecimal Routing Numbers address family. 1196 5.1.1.4. E.164 Numbers 1198 The E.164 Numbers address family is dedicated to fully qualified 1199 E.164 numbers. A set of telephone numbers is specified by a E.164 1200 prefix. E.164 prefixes are represented by a string of digits, each 1201 digit encoded by its ASCII character representation. This routing 1202 object covers all phone numbers starting with this prefix. The syntax 1203 for the E.164 prefix is: 1205 E164-number = *e164-digit 1206 E164-digit = E164-DIGIT 1207 E164-DIGIT = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9" 1209 This format facilitates efficient comparison when using TRIP to route 1210 SIP or H323, both of which use character based representations of 1211 phone numbers. The prefix length is determined from the length field 1212 of the route. 1214 The E.164 Numbers address family and the Decimal Routing Numbers 1215 address family have the same alphabet. The E.164 Numbers address 1216 family SHOULD be used whenever possible. The Decimal Routing Numbers 1217 address family can be used in case of private numbering plans or 1218 applications that do not desire to advertise fully expanded, fully 1219 qualified telephone numbers. If Decimal routing Numbers are used to 1220 advertise non-fully qualified prefixes, the prefixes may have to be 1221 manipulated (e.g. expanded) at the boundary between ITADs. This adds 1222 significant complexity to the egress LS, because, it has to map the 1223 prefixes from the format used in its own ITAD to the format used in 1224 the peer ITAD. 1226 5.2. ReachableRoutes 1228 Conditional Mandatory: False. 1229 Required Flags: Well-known. 1230 Potential Flags: Link-State Encapsulation (when flooding). 1231 TRIP Type Code: 2 1233 The ReachableRoutes attribute MUST be included in every UPDATE 1234 message. It specifies a set of routes that are to be added to service 1235 by the receiving LS(s). The set of routes MAY be empty, this is 1236 indicated by setting the length field to zero. 1238 5.2.1. Syntax of ReachableRoutes 1240 The ReachableRoutes Attribute has the same syntax as the 1241 WithdrawnRoutes Attribute. See Section 5.1.1. 1243 5.2.2. Route Origination and ReachableRoutes 1245 Routes are injected into TRIP by a method outside the scope of this 1246 specification. Possible methods include a front-end protocol, an 1247 intra-domain routing protocol, or static configuration. 1249 5.2.3. Route Selection and ReachableRoutes 1251 The routes in ReachableRoutes are necessary for route selection. 1253 5.2.4. Aggregation and ReachableRoutes 1255 To aggregate multiple routes, the set of ReachableRoutes to be 1256 aggregated MUST combine to form a less specific set. 1258 There is no mechanism within TRIP to communicate that a particular 1259 address prefix is not used and thus that these addresses could be 1260 skipped during aggregation. LSs MAY use methods outside of TRIP to 1261 learn of invalid prefixes that may be ignored during aggregation. 1263 If an LS advertises an aggregated route, it MUST include the 1264 AtomicAggregate attribute. 1266 5.2.5. Route Dissemination and ReachableRoutes 1268 The ReachableRoutes attribute is recomputed at each LS except where 1269 flooding is being used (e.g., within a domain). It is therefore 1270 possible for an LS to change Application Protocol field of a route 1271 before advertising that route to an external peer. 1273 If an LS changes the Application Protocol of a route it advertises, 1274 it MUST include the ConvertedRoute attribute in the UPDATE message. 1276 5.2.6. Aggregation Specifics for Decimal Routing Numbers, E.164 Numbers, 1277 and PentaDecimal Routing Numbers 1279 An LS that has routes to all valid numbers in a specific prefix 1280 SHOULD advertise that prefix as the ReachableRoutes, even if there 1281 are more specific prefixes that do not actually exist on the PSTN. 1282 Generally, it takes 10 Decimal Routing/E.164 prefixes, or 15 1283 PentaDecimal Routing prefixes, of length n to aggregate into a prefix 1284 of length n-1. However, if an LS is aware that a prefix is an invalid 1285 Decimal Routing/E.164 prefix, or PentaDecimal Routing prefix, then 1286 the LS MAY aggregate by skipping this prefix. For example, if the 1287 Decimal Routing prefix 19191 is known not to exist, then an LS can 1288 aggregate to 1919 without 19191. A prefix representing an invalid set 1289 of PSTN destinations is sometimes referred to as a "black-hole." 1290 The method by which an LS is aware of black-holes is not within the 1291 scope of TRIP, but if an LS has such knowledge, it can use the 1292 knowledge when aggregating. 1294 5.3. NextHopServer 1296 Conditional Mandatory: True (if ReachableRoutes and/or 1297 WithdrawnRoutes attribute is present). 1298 Required Flags: Well-known. 1299 Potential Flags: None. 1300 TRIP Type Code: 3. 1302 Given a route with application protocol A and destinations D, the 1303 NextHopServer indicates the next-hop that messages of protocol A 1304 destined for D should be sent. This may or may not represent the 1305 ultimate destination of those messages. 1307 5.3.1. NextHopServer Syntax 1309 For generality, the address of the next-hop server may be of various 1310 types (domain name, IPv4, IPv6, etc). The NextHopServer attribute 1311 includes the ITAD number of next-hop server, a length field , and a 1312 next-hop name or address. 1314 The syntax for the NextHopServer is given in Figure 13. 1316 0 1 2 3 1317 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 1318 +---------------+---------------+--------------+----------------+ 1319 | Next Hop ITAD | 1320 +---------------+---------------+--------------+----------------+ 1321 | Length | Server (variable) ... 1322 +---------------+---------------+--------------+----------------+ 1324 Figure 13: NextHopServer Syntax 1326 The Next-Hop ITAD indicates the domain of the next-hop. Length field 1327 gives the number of octets in the Server field, and the Server field 1328 contains the name or address of the next-hop server. The server field 1329 is represented as a string of ASCII characters. It is defined as 1330 follows: 1332 Server = host [":" port ] 1333 host = < A legal Internet host domain name 1334 or an IPv4 address using the textual representation 1335 defined in Section 2.1 of RFC 1123 [9] 1336 or an IPv6 address using the textual representation 1337 defined in Section 2.2 of RFC 2373 [10]. The IPv6 1338 address MUST be enclosed in "[" and "]" 1339 characters.> 1340 port = *DIGIT 1342 If the port is empty or not given, the default port is assumed (e.g., 1343 port 5060 if the application protocol is SIP). 1345 5.3.2. Route Origination and NextHopServer 1347 When an LS originates a routing object into TRIP, it MUST include a 1348 NextHopServer within its domain. The NextHopServer could be an 1349 address of the egress gateway or of a signaling proxy. 1351 5.3.3. Route Selection and NextHopServer 1353 LS policy may prefer certain next-hops or next-hop domains over 1354 others. 1356 5.3.4. Aggregation and NextHopServer 1358 When aggregating multiple routing objects into a single routing 1359 object, an LS MUST insert a new signaling server from within its 1360 domain as the new NextHopServer unless all of the routes being 1361 aggregated have the same next-hop. 1363 5.3.5. Route Dissemination and NextHopServer 1365 When propagating routing objects to peers, an LS may choose to insert 1366 a signaling proxy within its domain as the new next-hop, or it may 1367 leave the next-hop unchanged. Inserting a new next-hop will cause the 1368 signaling messages to be sent to that address, and will provide finer 1369 control over the signaling path. Leaving the next-hop unchanged will 1370 yield a more efficient signaling path (fewer hops). It is a local 1371 policy decision of the LS to decide whether to propagate or change 1372 the NextHopServer. 1374 5.4. AdvertisementPath 1376 Conditional Mandatory: True (if ReachableRoutes and/or 1377 WithdrawnRoutes attribute is present). 1378 Required Flags: Well-known. 1379 Potential Flags: None. 1380 TRIP Type Code: 4. 1382 This attribute identifies the ITADs through which routing information 1383 carried in an advertisement has passed. The AdvertisementPath 1384 attribute is analogous to the AS_PATH attribute in BGP. The 1385 attributes differ in that BGP's AS_PATH also reflects the path to the 1386 destination. In TRIP, not every domain need modify the next-hop, so 1387 the AdvertisementPath may include many more hops than the actual path 1388 to the destination. The RoutedPath attribute (Section 5.5) reflects 1389 the actual path to the destination. 1391 5.4.1. AdvertisementPath Syntax 1393 AdvertisementPath is a variable length attribute that is composed of 1394 a sequence of ITAD path segments. Each ITAD path segment is 1395 represented by a type-length-value triple. 1397 The path segment type is a 1-octet long field with the following 1398 values defined: 1400 Value Segment Type 1401 1 AP_SET: unordered set of ITADs a route in the 1402 advertisement message has traversed 1403 2 AP_SEQUENCE: ordered set of ITADs a route in 1404 the advertisement message has traversed 1406 The path segment length is a 1-octet long field containing the number 1407 of ITADs in the path segment value field. 1409 The path segment value field contains one or more ITAD numbers, each 1410 encoded as a 4-octets long field. ITAD numbers uniquely identify an 1411 Internet Telephony Administrative Domain, and must be obtained from 1412 IANA. See Section 13 for procedures to obtain an ITAD number from 1413 IANA. 1415 5.4.2. Route Origination and AdvertisementPath 1417 When an LS originates a route then: 1419 - The originating LS shall include its own ITAD number in the 1420 AdvertisementPath attribute of all advertisements sent to LSs 1421 located in neighboring ITADs. In this case, the ITAD number of 1422 the originating LS's ITAD will be the only entry in the 1423 AdvertisementPath attribute. 1424 - The originating LS shall include an empty AdvertisementPath 1425 attribute in all advertisements sent to LSs located in its own 1426 ITAD. An empty AdvertisementPath attribute is one whose length 1427 field contains the value zero. 1429 5.4.3. Route Selection and AdvertisementPath 1431 The AdvertisementPath may be used for route selection. Possible 1432 criteria to be used are the number of hops on the path and the 1433 presence or absence of particular ITADs on the path. 1435 As discussed in Section 10, the AdvertisementPath is used to prevent 1436 routing information from looping. If an LS receives a route with its 1437 own ITAD already in the AdvertisementPath, the route MUST be 1438 discarded. 1440 5.4.4. Aggregation and AdvertisementPath 1442 The rules for aggregating AdvertisementPath attributes are given in 1443 the following sections, where the term "path" used in Section 5.4.4.1 1444 and 5.4.4.2 is understood to mean AdvertisementPath. 1446 5.4.4.1. Aggregating Routes with Identical Paths 1448 If all routes to be aggregated have identical path attributes, then 1449 the aggregated route has the same path attribute as the individual 1450 routes. 1452 5.4.4.2. Aggregating Routes with Different Paths 1454 For the purpose of aggregating path attributes we model each ITAD 1455 within the path as a pair , where "type" identifies a 1456 type of the path segment (AP_SEQUENCE or AP_SET), and "value" is the 1457 ITAD number. Two ITADs are said to be the same if their corresponding 1458 are the same. 1460 If the routes to be aggregated have different path attributes, then 1461 the aggregated path attribute shall satisfy all of the following 1462 conditions: 1464 - All pairs of the type AP_SEQUENCE in the aggregated path MUST 1465 appear in all of the paths of routes to be aggregated. 1466 - All pairs of the type AP_SET in the aggregated path MUST appear 1467 in at least one of the paths of the initial set (they may appear 1468 as either AP_SET or AP_SEQUENCE types). 1469 - For any pair X of the type AP_SEQUENCE that precedes pair Y in 1470 the aggregated path, X precedes Y in each path of the initial set 1471 that contains Y, regardless of the type of Y. 1472 - No pair with the same value shall appear more than once in the 1473 aggregated path, regardless of the pair's type. 1475 An implementation may choose any algorithm that conforms to these 1476 rules. At a minimum a conformant implementation MUST be able to 1477 perform the following algorithm that meets all of the above 1478 conditions: 1480 - Determine the longest leading sequence of tuples (as defined 1481 above) common to all the paths of the routes to be aggregated. 1482 Make this sequence the leading sequence of the aggregated path. 1483 - Set the type of the rest of the tuples from the paths of the 1484 routes to be aggregated to AP_SET, and append them to the 1485 aggregated path. 1486 - If the aggregated path has more than one tuple with the same 1487 value (regardless of tuple's type), eliminate all but one such 1488 tuple by deleting tuples of the type AP_SET from the aggregated 1489 path. 1491 An implementation that chooses to provide a path aggregation 1492 algorithm that retains significant amounts of path information 1493 may wish to use the procedure of Section 5.4.4.3. 1495 5.4.4.3. Example Path Aggregation Algorithm 1497 An example algorithm to aggregate two paths works as follows: 1499 - Identify the ITADs (as defined in Section 5.4.1) within each path 1500 attribute that are in the same relative order within both path 1501 attributes. Two ITADs, X and Y, are said to be in the same order 1502 if either X precedes Y in both paths, or if Y precedes X in both 1503 paths. 1504 - The aggregated path consists of ITADs identified in (a) in 1505 exactly the same order as they appear in the paths to be 1506 aggregated. If two consecutive ITADs identified in (a) do not 1507 immediately follow each other in both of the paths to be 1508 aggregated, then the intervening ITADs (ITADs that are between 1509 the two consecutive ITADs that are the same) in both attributes 1510 are combined into an AP_SET path segment that consists of the 1511 intervening ITADs from both paths; this segment is then placed in 1512 between the two consecutive ITADs identified in (a) of the 1513 aggregated attribute. If two consecutive ITADs identified in (a) 1514 immediately follow each other in one attribute, but do not follow 1515 in another, then the intervening ITADs of the latter are combined 1516 into an AP_SET path segment; this segment is then placed in 1517 between the two consecutive ITADs identified in (a) of the 1518 aggregated path. 1520 If as a result of the above procedure a given ITAD number appears 1521 more than once within the aggregated path, all, but the last instance 1522 (rightmost occurrence) of that ITAD number should be removed from the 1523 aggregated path. 1525 5.4.5. Route Dissemination and AdvertisementPath 1527 When an LS propagates a route which it has learned from another LS, 1528 it shall modify the route's AdvertisementPath attribute based on the 1529 location of the LS to which the route will be sent. 1531 - When a LS advertises a route to another LS located in its own 1532 ITAD, the advertising LS MUST NOT modify the AdvertisementPath 1533 attribute associated with the route. 1534 - When a LS advertises a route to an LS located in a neighboring 1535 ITAD, then the advertising LS MUST update the AdvertisementPath 1536 attribute as follows: 1538 * If the first path segment of the AdvertisementPath is of type 1539 AP_SEQUENCE, the local system shall prepend its own ITAD 1540 number as the last element of the sequence (put it in the 1541 leftmost position). 1542 * If the first path segment of the AdvertisementPath is of type 1543 AP_SET, the local system shall prepend a new path segment of 1544 type AP_SEQUENCE to the AdvertisementPath, including its own 1545 ITAD number in that segment. 1547 5.5. RoutedPath 1549 Conditional Mandatory: True (if ReachableRoutes attribute is present). 1550 Required Flags: Well-known. 1551 Potential Flags: None. 1552 TRIP Type Code: 5. 1554 This attribute identifies the ITADs through which messages sent using 1555 this route would pass. The ITADs in this path are a subset of those 1556 in the AdvertisementPath. 1558 5.5.1. RoutedPath Syntax 1560 The syntax of the RoutedPath attribute is the same as that of the 1561 AdvertisementPath attribute. See Section 5.4.1. 1563 5.5.2. Route Origination and RoutedPath 1565 When an LS originates a route it MUST include the RoutedPath 1566 attribute. 1568 - The originating LS shall include its own ITAD number in the 1569 RoutedPath attribute of all advertisements sent to LSs located in 1570 neighboring ITADs. In this case, the ITAD number of the 1571 originating LS's ITAD will be the only entry in the RoutedPath 1572 attribute. 1573 - The originating LS shall include an empty RoutedPath attribute in 1574 all advertisements sent to LSs located in its own ITAD. An empty 1575 RoutedPath attribute is one whose length field contains the value 1576 zero. 1578 5.5.3. Route Selection and RoutedPath 1580 The RoutedPath MAY be used for route selection, and in most cases is 1581 preferred over the AdvertisementPath for this role. Some possible 1582 criteria to be used are the number of hops on the path and the 1583 presence or absence of particular ITADs on the path. 1585 5.5.4. Aggregation and RoutedPath 1587 The rules for aggregating RoutedPath attributes are given in Section 1588 5.4.4.1 and 5.4.4.2, where the term "path" used in Section 5.4.4.1 1589 and 5.4.4.2 is understood to mean RoutedPath. 1591 5.5.5. Route Dissemination and RoutedPath 1593 When an LS propagates a route that it learned from another LS, it 1594 modifies the route's RoutedPath attribute based on the location of 1595 the LS to which the route is sent. 1597 - When a LS advertises a route to another LS located in its own 1598 ITAD, the advertising LS MUST NOT modify the RoutedPath attribute 1599 associated with the route. 1600 - If the LS has not changed the NextHopServer attribute, then the 1601 LS MUST NOT change the RoutedPath attribute. 1602 - Otherwise, the LS changed the NextHopServer and is advertising 1603 the route to an LS in another ITAD. The advertising LS MUST 1604 update the RoutedPath attribute as follows: 1606 * If the first path segment of the RoutedPath is of type 1607 AP_SEQUENCE, the local system shall prepend its own ITAD 1608 number as the last element of the sequence (put it in the 1609 leftmost position). 1611 * If the first path segment of the RoutedPath is of type 1612 AP_SET, the local system shall prepend a new path segment of 1613 type AP_SEQUENCE to the RoutedPath, including its own ITAD 1614 number in that segment. 1616 5.6. AtomicAggregate 1618 Conditional Mandatory: False. 1619 Required Flags: Well-known. 1620 Potential Flags: None. 1621 TRIP Type Code: 6. 1623 The AtomicAggregate attribute indicates that a route may traverse 1624 domains not listed in the RoutedPath. If an LS, when presented with a 1625 set of overlapping routes from a peer LS, selects the less specific 1626 route without selecting the more specific route, then the LS includes 1627 the AtomicAggregate attribute with the routing object. 1629 5.6.1. AtomicAggregate Syntax 1631 This attribute has length zero (0); the value field is empty. 1633 5.6.2. Route Origination and AtomicAggregate 1635 Routes are never originated with the AtomicAggregate attribute. 1637 5.6.3. Route Selection and AtomicAggregate 1639 The AtomicAggregate attribute may be used in route selection - it 1640 indicates that the RoutedPath may be incomplete. 1642 5.6.4. Aggregation and AtomicAggregate 1644 If any of the routes to aggregate has the AtomicAggregate attribute, 1645 then so MUST the resultant aggregate. 1647 5.6.5. Route Dissemination and AtomicAggregate 1649 If an LS, when presented with a set of overlapping routes from a peer 1650 LS, selects the less specific route (see Section 0) without selecting 1651 the more specific route, then the LS MUST include the AtomicAggregate 1652 attribute with the routing object (if it is not already present). 1654 An LS receiving a routing object with an AtomicAggregate attribute 1655 MUST NOT make the set of destinations more specific when advertising 1656 it to other LSs, and MUST NOT remove the attribute when propagating 1657 this object to a peer LS. 1659 5.7. LocalPreference 1661 Conditional Mandatory: False. 1662 Required Flags: Well-known. 1663 Potential Flags: None. 1664 TRIP Type Code: 7. 1666 The LocalPreference attribute is only used intra-domain, it indicates 1667 the local LS's preference for the routing object to other LSs within 1668 the same domain. This attribute MUST NOT be included when 1669 communicating to an LS in another domain, and MUST be included over 1670 intra-domain links. 1672 5.7.1. LocalPreference Syntax 1674 The LocalPreference attribute is a 4-octet unsigned numeric value. A 1675 higher value indicates a higher preference. 1677 5.7.2. Route Origination and LocalPreference 1679 Routes MUST NOT be originated with the LocalPreference attribute to 1680 inter-domain peers. Routes to intra-domain peers MUST be originated 1681 with the LocalPreference attribute. 1683 5.7.3. Route Selection and LocalPreference 1685 The LocalPreference attribute allows one LS in a domain to calculate 1686 a preference for a route, and to communicate this preference to other 1687 LSs within the domain. 1689 5.7.4. Aggregation and LocalPreference 1691 The LocalPreference attribute is not affected by aggregation. 1693 5.7.5. Route Dissemination and LocalPreference 1695 An LS MUST include the LocalPreference attribute when communicating 1696 with peer LSs within its own domain. An LS MUST NOT include the 1697 LocalPreference attribute when communicating with LSs in other 1698 domains. LocalPreference attributes received from inter-domain peers 1699 MUST be ignored. 1701 5.8. MultiExitDisc 1703 Conditional Mandatory: False. 1704 Required Flags: Well-known. 1705 Potential Flags: None. 1706 TRIP Type Code: 8. 1708 When two ITADs are connected by more than one set of peers, the 1709 MultiExitDisc attribute may be used to specify preferences for routes 1710 received over one of those links versus routes received over other 1711 links. The MultiExitDisc parameter is used only for route selection. 1713 5.8.1. MultiExitDisc Syntax 1715 The MultiExitDisc attribute carries a 4-octet unsigned numeric value. 1716 A higher value represents a more preferred routing object. 1718 5.8.2. Route Origination and MultiExitDisc 1720 Routes originated to intra-domain peers MUST NOT be originated with 1721 the MultiExitDisc attribute. When originating a route to an inter- 1722 domain peer, the MultiExitDisc attribute may be included. 1724 5.8.3. Route Selection and MultiExitDisc 1726 The MultiExitDisc attribute is used to express a preference when 1727 there are multiple links between two domains. If all other factors 1728 are equal, then a route with a higher MultiExitDisc attribute is 1729 preferred over a route with a lower MultiExitDisc attribute. 1731 5.8.4. Aggregation and MultiExitDisc 1733 Routes with differing MultiExitDisc parameters MUST NOT be 1734 aggregated. Routes with the same value in the MultiExitDisc attribute 1735 MAY be aggregated and the same MultiExitDisc attribute attached to 1736 the aggregated object. 1738 5.8.5. Route Dissemination and MultiExitDisc 1740 If received from a peer LS in another domain, an LS MAY propagate the 1741 MultiExitDisc to other LSs within its domain. The MultiExitDisc 1742 attribute MUST NOT be propagated to LSs in other domains. 1744 An LS may add the MultiExitDisc attribute when propagating routing 1745 objects to an LS in another domain. The inclusion of the 1746 MultiExitDisc attribute is a matter of policy, as is the value of the 1747 attribute. 1749 5.9. Communities 1751 Conditional Mandatory: False. 1752 Required Flags: Not Well-Known, Independent Transitive. 1753 Potential Flags: None. 1754 TRIP Type Code: 9. 1756 A community is a group of destinations that share some common 1757 property. 1759 The Communities attribute is used to group destinations so that the 1760 routing decision can be based on the identity of the group. Using the 1761 Communities attribute should significantly simplify the distribution 1762 of routing information by providing an administratively defined 1763 aggregation unit. 1765 Each ITAD administrator may define the communities to which a 1766 particular route belongs. By default, all routes belong to the 1767 general Internet Telephony community. 1769 As an example, the Communities attribute could be used to define an 1770 alliance between a group of Internet Telephony service providers for 1771 a specific subset of routing information. In this case, members of 1772 that alliance would accept only routes for destinations in this group 1773 that are advertised by other members of the alliance. Other 1774 destinations would be more freely accepted. To achieve this, a member 1775 would tag each route with a designated Community attribute value 1776 before disseminating it. This relieves the members of such an 1777 alliance from the responsibility of keeping track of the identities 1778 of all other members of that alliance. 1780 Another example use of the Communities attribute is with aggregation. 1781 It is often useful to advertise both the aggregate route and the 1782 component more-specific routes that were used to form the aggregate. 1783 These component information are only useful to the neighboring TRIP 1784 peer, and perhaps the ITAD of the neighboring TRIP peer, so it is 1785 desirable to filter out the component routes. This can be achieved by 1786 specifying a Community attribute value that the neighboring peers 1787 will match and filter on. That way it can be assured that the more 1788 specific routes will not propagate beyond their desired scope. 1790 5.9.1. Syntax of Communities 1792 The Communities attribute is of variable length. It consists of set 1793 of 8-octet values, each of which specifies a community. The first 4 1794 octets of the Community value are the Community ITAD Number and the 1795 next 4 octets are the Community ID. 1797 0 1 2 3 1798 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 1799 +---------------+---------------+--------------+----------------+ 1800 | Community ITAD Number 1 | 1801 +---------------+---------------+--------------+----------------+ 1802 | Community ID 1 | 1803 +---------------+---------------+--------------+----------------+ 1804 | . . . . . . . . . 1805 +---------------+---------------+--------------+----------------+ 1807 Figure 14: Communities Syntax 1809 For administrative assignment, the following assumptions may be made: 1811 The Community attribute values starting with a Community ITAD 1812 Number of 0x00000000 are hereby reserved. 1814 The following communities have global significance and their 1815 operation MUST be implemented in any Community attribute-aware TRIP 1816 LS. 1818 - NO_EXPORT (Community ITAD Number = 0x00000000 and Community ID = 1819 0xFFFFFF01). Any received route with a community attribute 1820 containing this value MUST NOT be advertised outside of the 1821 receiving TRIP ITAD. 1823 Other community values MUST be encoded using an ITAD number in the 1824 four most significant octets. The semantics of the final four octets 1825 (the Community ID octets) may be defined by the ITAD (e.g., ITAD 690 1826 may define research, educational, and commercial community IDs that 1827 may be used for policy routing as defined by the operators of that 1828 ITAD). 1830 5.9.2. Route Origination and Communities 1832 The Communities attribute is not well-known. If a route has a 1833 Communities attribute associated with it, the LS MUST include that 1834 attribute in advertisement it originates. 1836 5.9.3. Route Selection and Communities 1838 The Communities attribute may be used for route selection. A route 1839 that is a member of a certain community may be preferred over another 1840 route that is not a member of that community. Likewise, routes 1841 without a certain community value may be excluded from consideration. 1843 5.9.4. Aggregation and Communities 1845 If a set of routes is to be aggregated and the resultant aggregate 1846 does not carry an Atomic_Aggregate attribute, then the resulting 1847 aggregate should have a Communities attribute that contains the union 1848 of the Community attributes of the aggregated routes. 1850 5.9.5. Route Dissemination and Communities 1852 An LS may manipulate the Communities attribute before disseminating a 1853 route to a peer. Community attribute manipulation may include adding 1854 communities, removing communities, adding a Communities attribute (if 1855 none exists), deleting the Communities attribute, etc. 1857 5.10. ITAD Topology 1859 Conditional Mandatory: False. 1860 Required Flags: Well-known, Link-State encapsulated. 1861 Potential Flags: None. 1862 TRIP Type Code: 10. 1864 Within an ITAD, each LS must know the status of other LSs so that LS 1865 failure can be detected. To do this, each LS advertises its internal 1866 topology to other LSs within the domain. When an LS detects that 1867 another LS is no longer active, the information sourced by that LS 1868 can be deleted (the Adj-TRIB-In for that peer may be cleared). The 1869 ITAD Topology attribute is used to communicate this information to 1870 other LSs within the domain. 1872 An LS MUST send a topology update each time it detects a change in 1873 its internal peer set. The topology update may be sent in an UPDATE 1874 message by itself or it may be piggybacked on an UPDATE message which 1875 includes ReachableRoutes and/or WithdrawnRoutes information. 1877 When an LS receives a topology update from an internal LS, it MUST 1878 recalculate to which LSs are active within their domain via a 1879 connectivity algorithm on the topology. 1881 5.10.1. ITAD Topology Syntax 1883 The ITAD Topology attribute indicates the LSs with which the LS is 1884 currently peering. The attribute consists of a list of the TRIP 1885 Identifiers with which the LS is currently peering, the format is 1886 given in Figure 15. This attribute MUST use the link-state 1887 encapsulation as defined in Section 4.3.2.4. 1889 0 1 2 3 1890 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 1891 +---------------+---------------+--------------+----------------+ 1892 | TRIP Identifier 1 | 1893 +---------------+---------------+--------------+----------------+ 1894 | TRIP Identifier 2 ... | 1895 +---------------+---------------+--------------+----------------+ 1897 Figure 15: ITAD Topology Syntax 1899 5.10.2. Route Origination and ITAD Topology 1901 The ITAD Topology attribute is independent of any routes in the 1902 UPDATE. Whenever the set of internal peers of a LS changes, it 1903 MUST 1904 originate an UPDATE with the ITAD Topology Attribute included 1905 listing the current set of internal peers. The LS MUST include 1906 this attribute in the first UPDATE it sends to a peer after the 1907 peering session is established. 1909 5.10.3. Route Selection and ITAD Topology 1911 This attribute is independent of any routing information in the 1912 UPDATE. When an LS receives an UPDATE with an ITAD Topology 1913 attribute, it MUST compute the set of LSs currently active in the 1914 domain by performing a connectivity test on the ITAD topology as 1915 given by the set of originated ITAD Topology attributes. The LS MUST 1916 locally purge the Adj-TRIB-In for any LS that is no longer active in 1917 the domain. The LS MUST NOT propagate this purging information to 1918 other LSs as they will make a similar decision. 1920 5.10.4. Aggregation and ITAD Topology 1922 This information is not aggregated. 1924 5.10.5. Route Dissemination and ITAD Topology 1926 An LS MUST ignore the attribute if received from a peer in another 1927 domain. An LS MUST NOT send this attribute to an inter-domain peer. 1929 5.11. ConvertedRoute 1931 Conditional Mandatory: False. 1932 Required Flags: Well-known. 1933 Potential Flags: None. 1934 TRIP Type Code: 12. 1936 The ConvertedRoute attribute indicates that an intermediate LS has 1937 altered the route by changing the route's Application Protocol. For 1938 example, if an LS receives a route with Application Protocol X and 1939 changes the Application Protocol to Y before advertising the route to 1940 an external peer, the LS MUST include the ConvertedRoute attribute. 1941 The attribute is an indication that the advertised application 1942 protocol will not be used end-to-end, i.e., the information 1943 advertised about this route is not complete. 1945 5.11.1. ConvertedRoute Syntax 1947 This attribute has length zero (0); the value field is empty. 1949 5.11.2. Route Origination and ConvertedRoute 1951 Routes are never originated with the ConvertedRoute attribute. 1953 5.11.3. Route Selection and ConvertedRoute 1955 The ConvertedRoute attribute may be used in route selection - it 1956 indicates that advertised routing information is not complete. 1958 5.11.4. Aggregation and ConvertedRoute 1960 If any of the routes to aggregate has the ConvertedRoute attribute, 1961 then so MUST the resultant aggregate. 1963 5.11.5. Route Dissemination and ConvertedRoute 1965 If an LS changes the Application Protocol of route before advertising 1966 the route to an external peer, the LS MUST include the ConvertedRoute 1967 attribute. 1969 5.12. Considerations for Defining New TRIP Attributes 1971 Any proposal for defining new TRIP attributes should specify the 1972 following: 1974 - the use of this attribute, 1975 - the attribute's flags, 1976 - the attribute's syntax, 1977 - how the attribute works with route origination, 1978 - how the attribute works with route aggregation, and 1979 - how the attribute works with route dissemination and the 1980 attribute's scope (e.g., intra-domain only like LocalPreference) 1982 IANA will manage the assignment of TRIP attribute type codes to new 1983 attributes. 1985 6. TRIP Error Detection and Handling 1987 This section describes errors to be detected and the actions to be 1988 taken while processing TRIP messages. 1990 When any of the conditions described here are detected, a 1991 NOTIFICATION message with the indicated Error Code, Error Subcode, 1992 and Data fields MUST be sent, and the TRIP connection MUST be closed. 1993 If no Error Subcode is specified, then a zero Subcode MUST be used. 1995 The phrase "the TRIP connection is closed" means that the transport 1996 protocol connection has been closed and that all resources for that 1997 TRIP connection have been de-allocated. If the connection was inter- 1998 domain, then routing table entries associated with the remote peer 1999 MUST be marked as invalid. Routing table entries MUST NOT be marked 2000 as invalid if an internal peering session is terminated. The fact 2001 that the routes have been marked as invalid is passed to other TRIP 2002 peers before the routes are deleted from the system. 2004 Unless specified explicitly, the Data field of the NOTIFICATION 2005 message that is sent to indicate an error MUST be empty. 2007 6.1. Message Header Error Detection and Handling 2009 All errors detected while processing the Message Header are indicated 2010 by sending the NOTIFICATION message with Error Code Message Header 2011 Error. The Error Subcode elaborates on the specific nature of the 2012 error. The error checks in this section MUST be performed by each LS 2013 on receipt of every message. 2015 If the Length field of the message header is less than 3 or greater 2016 than 4096, or if the Length field of an OPEN message is less than the 2017 minimum length of the OPEN message, or if the Length field of an 2018 UPDATE message is less than the minimum length of the UPDATE message, 2019 or if the Length field of a KEEPALIVE message is not equal to 3, or 2020 if the Length field of a NOTIFICATION message is less than the 2021 minimum length of the NOTIFICATION message, then the Error Subcode 2022 MUST be set to Bad Message Length. The Data field contains the 2023 erroneous Length field. 2025 If the Type field of the message header is not recognized, then the 2026 Error Subcode MUST be set to "Bad Message Type." The Data field 2027 contains the erroneous Type field. 2029 6.2. OPEN Message Error Detection and Handling 2031 All errors detected while processing the OPEN message are indicated 2032 by sending the NOTIFICATION message with Error Code "OPEN Message 2033 Error." The Error Subcode elaborates on the specific nature of the 2034 error. The error checks in this section MUST be performed by each LS 2035 on receipt of every OPEN message. 2037 If the version number contained in the Version field of the received 2038 OPEN message is not supported, then the Error Subcode MUST be set to 2039 "Unsupported Version Number." The Data field is a 1-octet unsigned 2040 integer, which indicates the largest locally supported version number 2041 less than the version the remote TRIP peer bid (as indicated in the 2042 received OPEN message). 2044 If the ITAD field of the OPEN message is unacceptable, then the Error 2045 Subcode MUST be set to "Bad Peer ITAD." The determination of 2046 acceptable ITAD numbers is outside the scope of this protocol. 2048 If the Hold Time field of the OPEN message is unacceptable, then the 2049 Error Subcode MUST be set to "Unacceptable Hold Time." An 2050 implementation MUST reject Hold Time values of one or two seconds. An 2051 implementation MAY reject any proposed Hold Time. An implementation 2052 that accepts a Hold Time MUST use the negotiated value for the Hold 2053 Time. 2055 If the TRIP Identifier field of the OPEN message is not valid, then 2056 the Error Subcode MUST be set to "Bad TRIP Identifier." A TRIP 2057 identifier is 4-octets and can take any value. An LS considers the 2058 TRIP Identifier invalid if it has an already open connection with 2059 another peer LS that has the same ITAD and TRIP Identifier. 2061 Any two LSs within the same ITAD MUST NOT have equal TRIP Identifier 2062 values. This restriction does not apply to LSs in different ITADs 2063 since the purpose is to uniquely identify an LS using its TRIP 2064 Identifier and its ITAD number. 2066 If one of the Optional Parameters in the OPEN message is not 2067 recognized, then the Error Subcode MUST be set to "Unsupported 2068 Optional Parameters." 2070 If the Optional Parameters of the OPEN message include Capability 2071 Information with an unsupported capability (unsupported in either 2072 capability type or value), then the Error Subcode MUST be set to 2073 "Unsupported Capability," and the entirety of the unsupported 2074 capabilities MUST be listed in the Data field of the NOTIFICATION 2075 message. 2077 If the Optional Parameters of the OPEN message include Capability 2078 Information which do not match the receiving LS's capabilities, then 2079 the Error Subcode MUST be set to "Capability Mismatch," and the 2080 entirety of the mismatched capabilities MUST be listed in the Data 2081 field of the NOTIFICATION message. 2083 6.3. UPDATE Message Error Detection and Handling 2085 All errors detected while processing the UPDATE message are indicated 2086 by sending the NOTIFICATION message with Error Code "UPDATE Message 2087 Error." The Error Subcode elaborates on the specific nature of the 2088 error. The error checks in this section MUST be performed by each LS 2089 on receipt of every UPDATE message. These error checks MUST occur 2090 before flooding procedures are invoked with internal peers. 2092 If any recognized attribute has Attribute Flags that conflict with 2093 the Attribute Type Code, then the Error Subcode MUST be set to 2094 "Attribute Flags Error." The Data field contains the erroneous 2095 attribute (type, length and value). 2097 If any recognized attribute has Attribute Length that conflicts with 2098 the expected length (based on the attribute type code), then the 2099 Error Subcode MUST be set to "Attribute Length Error." The Data 2100 field contains the erroneous attribute (type, length and value). 2102 If any of the mandatory (i.e., conditional mandatory attribute and 2103 the conditions for including it in the UPDATE message are fulfilled) 2104 well-known attributes are not present, then the Error Subcode MUST be 2105 set to "Missing Well-known Mandatory Attribute." The Data field 2106 contains the Attribute Type Code of the missing well-known 2107 conditional mandatory attributes. 2109 If any of the well-known attributes are not recognized, then the 2110 Error Subcode MUST be set to "Unrecognized Well-known Attribute." The 2111 Data field contains the unrecognized attribute (type, length and 2112 value). 2114 If any attribute has a syntactically incorrect value, or an undefined 2115 value, then the Error Subcode is set to "Invalid Attribute." The 2116 Data field contains the incorrect attribute (type, length and value). 2117 Such a NOTIFICATION message is sent, for example, when a 2118 NextHopServer attribute is received with an invalid address. 2120 The information carried by the AdvertisementPath attribute is checked 2121 for ITAD loops. ITAD loop detection is done by scanning the full 2122 AdvertisementPath, and checking that the ITAD number of the local 2123 ITAD does not appear in the AdvertisementPath. If the local ITAD 2124 number appears in the AdvertisementPath, then the route MAY be stored 2125 in the Adj-TRIB-In, but unless the LS is configured to accept routes 2126 with its own ITAD in the advertisement path, the route MUST not be 2127 passed to the TRIP Decision Process. The operation of an LS that is 2128 configured to accept routes with its own ITAD number in the 2129 advertisement path are outside the scope of this document. 2131 If the UPDATE message was received from an internal peer and either 2132 the WithdrawnRoutes, ReachableRoutes, or ITAD Topology attribute does 2133 not have the Link-State Encapsulation flag set, then the Error 2134 Subcode is set to "Invalid Attribute" and the data field contains the 2135 attribute. Likewise, the attribute is invalid if received from an 2136 external peer and the Link-State Flag is set. 2138 If any attribute appears more than once in the UPDATE message, then 2139 the Error Subcode is set to "Malformed Attribute List." 2141 6.4. NOTIFICATION Message Error Detection and Handling 2143 If a peer sends a NOTIFICATION message, and there is an error in that 2144 message, there is unfortunately no means of reporting this error via 2145 a subsequent NOTIFICATION message. Any such error, such as an 2146 unrecognized Error Code or Error Subcode, should be noticed, logged 2147 locally, and brought to the attention of the administration of the 2148 peer. The means to do this, however, are outside the scope of this 2149 document. 2151 6.5. Hold Timer Expired Error Handling 2153 If a system does not receive successive messages within the period 2154 specified by the negotiated Hold Time, then a NOTIFICATION message 2155 with "Hold Timer Expired" Error Code MUST be sent and the TRIP 2156 connection MUST be closed. 2158 6.6. Finite State Machine Error Handling 2160 An error detected by the TRIP Finite State Machine (e.g., receipt of 2161 an unexpected event) MUST result in sending a NOTIFICATION message 2162 with Error Code "Finite State Machine Error" and the TRIP connection 2163 MUST be closed. 2165 6.7. Cease 2167 In the absence of any fatal errors (that are indicated in this 2168 section), a TRIP peer MAY choose at any given time to close its TRIP 2169 connection by sending the NOTIFICATION message with Error Code 2170 "Cease." However, the Cease NOTIFICATION message MUST NOT be used 2171 when a fatal error indicated by this section exists. 2173 6.8. Connection Collision Detection 2175 If a pair of LSs try simultaneously to establish a transport 2176 connection to each other, then two parallel connections between this 2177 pair of speakers might well be formed. We refer to this situation as 2178 connection collision. Clearly, one of these connections must be 2179 closed. 2181 Based on the value of the TRIP Identifier a convention is established 2182 for detecting which TRIP connection is to be preserved when a 2183 collision occurs. The convention is to compare the TRIP Identifiers 2184 of the peers involved in the collision and to retain only the 2185 connection initiated by the LS with the higher-valued TRIP 2186 Identifier. 2188 Upon receipt of an OPEN message, the local LS MUST examine all of its 2189 connections that are in the OpenConfirm state. An LS MAY also examine 2190 connections in an OpenSent state if it knows the TRIP Identifier of 2191 the peer by means outside of the protocol. If among these connections 2192 there is a connection to a remote LS whose TRIP Identifier equals the 2193 one in the OPEN message, then the local LS MUST perform the following 2194 collision resolution procedure: 2196 The TRIP Identifier and ITAD of the local LS is compared to the TRIP 2197 Identifier and ITAD of the remote LS (as specified in the OPEN 2198 message). TRIP Identifiers are treated as 4-octet unsigned integers 2199 for comparison. 2201 If the value of the local TRIP Identifier is less than the remote 2202 one, or if the two TRIP Identifiers are equal and the value of ITAD 2203 of the local LS is less than value of the ITAD of the remote LS, then 2204 the local LS MUST close the TRIP connection that already exists (the 2205 one that is already in the OpenConfirm state), and accepts the TRIP 2206 connection initiated by the remote LS: 2208 1. Otherwise, the local LS closes newly created TRIP connection 2209 continues to use the existing one (the one that is already in 2210 the OpenConfirm state). 2212 2. If a connection collision occurs with an existing TRIP 2213 connection that is in the Established state, then the LS MUST 2214 unconditionally close of the newly created connection. Note 2215 that a connection collision cannot be detected with connections 2216 that are in Idle, Connect, or Active states. 2217 3. To close the TRIP connection (that results from the collision 2218 resolution procedure), an LS MUST send a NOTIFICATION message 2219 with the Error Code "Cease" and the TRIP connection MUST be 2220 closed. 2222 7. TRIP Version Negotiation 2224 Peer LSs may negotiate the version of the protocol by making multiple 2225 attempts to open a TRIP connection, starting with the highest version 2226 number each supports. If an open attempt fails with an Error Code 2227 "OPEN Message Error" and an Error Subcode "Unsupported Version 2228 Number," then the LS has available the version number it tried, the 2229 version number its peer tried, the version number passed by its peer 2230 in the NOTIFICATION message, and the version numbers that it 2231 supports. If the two peers support one or more common versions, then 2232 this will allow them to rapidly determine the highest common version. 2233 In order to support TRIP version negotiation, future versions of TRIP 2234 must retain the format of the OPEN and NOTIFICATION messages. 2236 8. TRIP Capability Negotiation 2238 An LS MAY include the Capabilities Option in its OPEN message to a 2239 peer to indicate the capabilities supported by the LS. An LS 2240 receiving an OPEN message MUST NOT use any capabilities that were not 2241 included in the OPEN message of the peer when communicating with that 2242 peer. 2244 9. TRIP Finite State Machine 2246 This section specifies TRIP operation in terms of a Finite State 2247 Machine (FSM). Following is a brief summary and overview of TRIP 2248 operations by state as determined by this FSM. A condensed version of 2249 the TRIP FSM is found in Appendix 1. There is a TRIP FSM per peer and 2250 these FSMs operate independently. 2252 Idle state: 2253 Initially TRIP is in the Idle state for each peer. In this state, 2254 TRIP refuses all incoming connections. No resources are allocated to 2255 the peer. In response to the Start event (initiated by either the 2256 system or the operator), the local system initializes all TRIP 2257 resources, starts the ConnectRetry timer, initiates a transport 2258 connection to the peer, starts listening for a connection that may be 2259 initiated by the remote TRIP peer, and changes its state to Connect. 2260 The exact value of the ConnectRetry timer is a local matter, but 2261 should be sufficiently large to allow TCP initialization. 2263 If an LS detects an error, it closes the transport connection and 2264 changes its state to Idle. Transitioning from the Idle state requires 2265 generation of the Start event. If such an event is generated 2266 automatically, then persistent TRIP errors may result in persistent 2267 flapping of the LS. To avoid such a condition, Start events MUST NOT 2268 be generated immediately for a peer that was previously transitioned 2269 to Idle due to an error. For a peer that was previously transitioned 2270 to Idle due to an error, the time between consecutive Start events, 2271 if such events are generated automatically, MUST exponentially 2272 increase. The value of the initial timer SHOULD be 60 seconds, and 2273 the time SHOULD be at least doubled for each consecutive retry up to 2274 some maximum value. 2276 Any other event received in the Idle state is ignored. 2278 Connect state: 2279 In this state, an LS is waiting for a transport protocol connection 2280 to be completed to the peer, and is listening for inbound transport 2281 connections from the peer. 2283 If the transport protocol connection succeeds, the local LS clears 2284 the ConnectRetry timer, completes initialization, sends an OPEN 2285 message to its peer, sets its Hold Timer to a large value, and 2286 changes its state to OpenSent. A Hold Timer value of 4 minutes is 2287 suggested. 2289 If the transport protocol connect fails (e.g., retransmission 2290 timeout), the local system restarts the ConnectRetry timer, continues 2291 to listen for a connection that may be initiated by the remote LS, 2292 and changes its state to Active state. 2294 In response to the ConnectRetry timer expired event, the local LS 2295 cancels any outstanding transport connection to the peer, restarts 2296 the ConnectRetry timer, initiates a transport connection to the 2297 remote LS, continues to listen for a connection that may be initiated 2298 by the remote LS, and stays in the Connect state. 2300 If the local LS detects that a remote peer is trying to establish a 2301 connection to it and the IP address of the peer is not an expected 2302 one, then the local LS rejects the attempted connection and continues 2303 to listen for a connection from its expected peers without changing 2304 state. 2306 If an inbound transport protocol connection succeeds, the local LS 2307 clears the ConnectRetry timer, completes initialization, sends an 2308 OPEN message to its peer, sets its Hold Timer to a large value, and 2309 changes its state to OpenSent. A Hold Timer value of 4 minutes is 2310 suggested. 2312 The Start event is ignored in the Connect state. 2314 In response to any other event (initiated by either the system or the 2315 operator), the local system releases all TRIP resources associated 2316 with this connection and changes its state to Idle. 2318 Active state: 2319 In this state, an LS is listening for an inbound connection from the 2320 peer, but is not in the process of initiating a connection to the 2321 peer. 2323 If an inbound transport protocol connection succeeds, the local LS 2324 clears the ConnectRetry timer, completes initialization, sends an 2325 OPEN message to its peer, sets its Hold Timer to a large value, and 2326 changes its state to OpenSent. A Hold Timer value of 4 minutes is 2327 suggested. 2329 In response to the ConnectRetry timer expired event, the local system 2330 restarts the ConnectRetry timer, initiates a transport connection to 2331 the TRIP peer, continues to listen for a connection that may be 2332 initiated by the remote TRIP peer, and changes its state to Connect. 2334 If the local LS detects that a remote peer is trying to establish a 2335 connection to it and the IP address of the peer is not an expected 2336 one, then the local LS rejects the attempted connection and continues 2337 to listen for a connection from its expected peers without changing 2338 state. 2340 Start event is ignored in the Active state. 2342 In response to any other event (initiated by either the system or the 2343 operator), the local system releases all TRIP resources associated 2344 with this connection and changes its state to Idle. 2346 OpenSent state: 2347 In this state, an LS has sent an OPEN message to its peer and is 2348 waiting for an OPEN message from its peer. When an OPEN message is 2349 received, all fields are checked for correctness. If the TRIP message 2350 header checking or OPEN message checking detects an error (see 2351 Section 6.2) or a connection collision (see Section 6.8), the local 2352 system sends a NOTIFICATION message and changes its state to Idle. 2354 If there are no errors in the OPEN message, TRIP sends a KEEPALIVE 2355 message and sets a KeepAlive timer. The Hold Timer, which was 2356 originally set to a large value (see above), is replaced with the 2357 negotiated Hold Time value (see Section 4.2). If the negotiated Hold 2358 Time value is zero, then the Hold Time timer and KeepAlive timers are 2359 not started. If the value of the ITAD field is the same as the local 2360 ITAD number, then the connection is an "internal" connection; 2361 otherwise, it is "external" (this will affect UPDATE processing). 2362 Finally, the state is changed to OpenConfirm. 2364 If the local LS detects that a remote peer is trying to establish a 2365 connection to it and the IP address of the peer is not an expected 2366 one, then the local LS rejects the attempted connection and continues 2367 to listen for a connection from its expected peers without changing 2368 state. 2370 If a disconnect notification is received from the underlying 2371 transport protocol, the local LS closes the transport connection, 2372 restarts the ConnectRetry timer, continues to listen for a connection 2373 that may be initiated by the remote TRIP peer, and goes into the 2374 Active state. 2376 If the Hold Timer expires, the local LS sends NOTIFICATION message 2377 with Error Code "Hold Timer Expired" and changes its state to Idle. 2379 In response to the Stop event (initiated by either system or 2380 operator) the local LS sends NOTIFICATION message with Error Code 2381 "Cease" and changes its state to Idle. 2383 The Start event is ignored in the OpenSent state. 2385 In response to any other event the local LS sends NOTIFICATION 2386 message with Error Code "Finite State Machine Error" and changes its 2387 state to Idle. 2389 Whenever TRIP changes its state from OpenSent to Idle, it closes the 2390 transport connection and releases all resources associated with that 2391 connection. 2393 OpenConfirm state: 2394 In this state, an LS has sent an OPEN to its peer, received an OPEN 2395 from its peer, and sent a KEEPALIVE in response to the OPEN. The LS 2396 is now waiting for a KEEPALIVE or NOTIFICATION message in response to 2397 its OPEN. 2399 If the local LS receives a KEEPALIVE message, it changes its state to 2400 Established. 2402 If the Hold Timer expires before a KEEPALIVE message is received, the 2403 local LS sends NOTIFICATION message with Error Code "Hold Timer 2404 Expired" and changes its state to Idle. 2406 If the local LS receives a NOTIFICATION message, it changes its state 2407 to Idle. 2409 If the KeepAlive timer expires, the local LS sends a KEEPALIVE 2410 message and restarts its KeepAlive timer. 2412 If a disconnect notification is received from the underlying 2413 transport protocol, the local LS closes the transport connection, 2414 restarts the ConnectRetry timer, continues to listen for a connection 2415 that may be initiated by the remote TRIP peer, and goes into the 2416 Active state. 2418 In response to the Stop event (initiated by either the system or the 2419 operator) the local LS sends NOTIFICATION message with Error Code 2420 "Cease" and changes its state to Idle. 2422 Start event is ignored in the OpenConfirm state. 2424 In response to any other event the local LS sends NOTIFICATION 2425 message with Error Code "Finite State Machine Error" and changes its 2426 state to Idle. 2428 Whenever TRIP changes its state from OpenConfirm to Idle, it closes 2429 the transport connection and releases all resources associated with 2430 that connection. 2432 Established state: 2433 In the Established state, an LS can exchange UPDATE, NOTIFICATION, 2434 and KEEPALIVE messages with its peer. 2436 If the negotiated Hold Timer is zero, then no procedures are 2437 necessary for keeping a peering session alive. If the negotiated Hold 2438 Time value is non-zero, the procedures of this paragraph apply. If 2439 the Hold Timer expires, the local LS sends a NOTIFICATION message 2440 with Error Code "Hold Timer Expired" and changes its state to Idle. 2441 If the KeepAlive Timer expires, then the local LS sends a KeepAlive 2442 message and restarts the KeepAlive Timer. If the local LS receives an 2443 UPDATE or KEEPALIVE message, then it restarts its Hold Timer. Each 2444 time the LS sends an UPDATE or KEEPALIVE message, it restarts its 2445 KeepAlive Timer. 2447 If the local LS receives a NOTIFICATION message, it changes its state 2448 to Idle. 2450 If the local LS receives an UPDATE message and the UPDATE message 2451 error handling procedure (see Section6.3) detects an error, the local 2452 LS sends a NOTIFICATION message and changes its state to Idle. 2454 If a disconnect notification is received from the underlying 2455 transport protocol, the local LS changes its state to Idle. 2457 In response to the Stop event (initiated by either the system or the 2458 operator), the local LS sends a NOTIFICATION message with Error Code 2459 "Cease" and changes its state to Idle. 2461 The Start event is ignored in the Established state. 2463 In response to any other event, the local LS sends NOTIFICATION 2464 message with Error Code "Finite State Machine Error" and changes its 2465 state to Idle. 2467 Whenever TRIP changes its state from Established to Idle, it closes 2468 the transport) connection, releases all resources associated with 2469 that connection. Additionally, if the peer is an external peer, the 2470 LS deletes all routes derived from that connection. 2472 10. UPDATE Message Handling 2474 An UPDATE message may be received only in the Established state. When 2475 an UPDATE message is received, each field is checked for validity as 2476 specified in Section 6.3. The rest of this section presumes that the 2477 UPDATE message has passed the error-checking procedures of Section 2478 6.3. 2480 If the UPDATE message was received from an internal peer, the 2481 flooding procedures of Section 10.1 MUST be applied. The flooding 2482 process synchronizes the Loc-TRIBs of all LSs within the domain. 2483 Certain routes within the UPDATE may be marked as old or duplicates 2484 by the flooding process and are ignored during the rest of the UPDATE 2485 processing. 2487 If the UPDATE message contains withdrawn routes, then the 2488 corresponding previously advertised routes shall be removed from the 2489 Adj-TRIB-In. This LS MUST run its Decision Process since the 2490 previously advertised route is no longer available for use. 2492 If the UPDATE message contains a route, then the route MUST be placed 2493 in the appropriate Adj-TRIB-In, and the following additional actions 2494 MUST be taken: 2496 1. If its destinations are identical to those of a route currently 2497 stored in the Adj-TRIB-In, then the new route MUST replace the 2498 older route in the Adj-TRIB-In, thus implicitly withdrawing the 2499 older route from service. The LS MUST run its Decision Process 2500 since the older route is no longer available for use. 2501 2. If the new route is more specific than an earlier route 2502 contained in the Adj-TRIB-In and has identical attributes, then 2503 no further actions are necessary. 2504 3. If the new route is more specific than an earlier route 2505 contained in the Adj-TRIB-In but does not have identical 2506 attributes, then the LS MUST run its Decision Process since the 2507 more specific route has implicitly made a portion of the less 2508 specific route unavailable for use. 2509 4. If the new route has destinations that are not present in any 2510 of the routes currently stored in the Adj-TRIB-In, then the LS 2511 MUST run its Decision Process. 2512 5. If the new route is less specific than an earlier route 2513 contained in the Adj-TRIB-In, the LS MUST run its Decision 2514 Process on the set of destinations that are described only by 2515 the less specific route. 2517 10.1. Flooding Process 2519 When an LS receives an UPDATE message from an internal peer, the LS 2520 floods the new information from that message to all of its other 2521 internal peers. Flooding is used to efficiently synchronize all of 2522 the LSs within a domain without putting any constraints on the 2523 domain's internal topology. The flooding mechanism is based on the 2524 techniques used in OSPF [4] and SCSP [6]. One may argue that TRIP's 2525 flooding process is in reality a controlled broadcast mechanism. 2527 10.1.1. Database Information 2529 The LS MUST maintain the sequence number and originating TRIP 2530 identifier for each link-state encapsulated attribute in an internal 2531 Adj-TRIB-In. These values are included with the route in the 2532 ReachableRoutes, WithdrawnRoutes, and ITAD Topology attributes. The 2533 originating TRIP identifier gives the internal LS that originated 2534 this route into the ITAD, the sequence number gives the version of 2535 this route at the originating LS. 2537 10.1.2. Determining Newness 2539 For each route in the ReachableRoutes or WithdrawnRoutes field, the 2540 LS decides if the route is new or old. This is determined by 2541 comparing the Sequence Number of the route in the UPDATE with the 2542 Sequence Number of the route saved in the Adj-TRIB-In. The route is 2543 new if either the route does not exist in the Adj-TRIB-In for the 2544 originating LS, or if the route does exist in the Adj-TRIB-In but the 2545 Sequence Number in the UPDATE is greater than the Sequence Number 2546 saved in the Adj-TRIBs-In. Note that the newness test is 2547 independently applied to each link-state encapsulated attribute in 2548 the UPDATE (WithdrawnRoutes or ReachableRoutes). 2550 10.1.3. Flooding 2552 Each route in the ReachableRoutes or WithdrawnRoutes field that is 2553 determined to be old is ignored in further processing. If the route 2554 is determined to be new then the following actions occur. 2556 If the route is being withdrawn, then the LS MUST flood the withdrawn 2557 route to all other internal peers, and MUST mark the route as 2558 withdrawn. An LS MUST maintain routes marked as withdrawn in its 2559 databases for MaxPurgeTime seconds. 2561 If the route is being updated, then the LS MUST update the route in 2562 the Adj-TRIB-In and MUST flood it to all other internal peers. 2564 If these procedures result in changes to the Adj-TRIB-In, then the 2565 route is also made available for local route processing as described 2566 early in Section 10. 2568 To implement flooding, the following is recommended. All routes 2569 received in a single UPDATE message that are determined to be new 2570 should be forwarded to all other internal peers in a single UPDATE 2571 message. Other variations on flooding are possible, but the local LS 2572 MUST ensure that each new route (and any associated attributes) 2573 received from an internal peer get forwarded to every other internal 2574 peer. 2576 10.1.4. Sequence Number Considerations 2578 The Sequence Number is used to determine when one version of a Route 2579 is newer than another version of a route. A larger Sequence Number 2580 indicates a newer version. The Sequence Number is assigned by the LS 2581 originating the route into the local ITAD. The Sequence Number is an 2582 unsigned 4-octet integer in the range of 1 thru 2^31-1 MinSequenceNum 2583 thru MaxSequenceNum). The value 0 is reserved. When an LS first 2584 originates a route (including when the LS restarts/reboots) into its 2585 ITAD, it MUST originate it with a Sequence Number of MinSequenceNum. 2586 Each time the route is updated within the ITAD by the originator, the 2587 Sequence Number MUST be increased. 2589 If it is ever the case that the sequence number is MaxSequenceNum-1 2590 and it needs to be increased, then the TRIP module of the LS MUST be 2591 disabled for a period of TripDisableTime so that all routes 2592 originated by this LS with high sequence numbers can be removed. 2594 10.1.5. Purging a Route Within the ITAD 2596 To withdraw a route that it originated within the ITAD, an LS 2597 includes the route in the WithdrawnRoutes field of an UPDATE message. 2598 The Sequence Number MUST be greater than the last valid version of 2599 the route. The LS MAY choose to use a sequence number of 2600 MaxSequenceNum when withdrawing routes within its ITAD, but this is 2601 not required. 2603 After withdrawing a route, an LS MUST mark the route as "withdrawn" 2604 in its database, and maintain the withdrawn route in its database for 2605 MaxPurgeTime seconds. If the LS needs to re-originate a route that 2606 had been purged but is still in its database, it can either re- 2607 originate the route immediately using a Sequence Number that is 2608 greater than that used in the withdraw, or the LS may wait until 2609 MaxPurgeTime seconds have expired since the route was withdrawn. 2611 10.1.6. Receiving Self-Originated Routes 2613 It is common for an LS to receive UPDATES for routes that it 2614 originated within the ITAD via the flooding procedure. If the LS 2615 receives an UPDATE for a route that it originated that is newer (has 2616 a higher sequence number) than the LSs current version, then special 2617 actions must be taken. This should be a relatively rare occurrence 2618 and indicates that a route still exists within the ITAD since the LSs 2619 last restart/reboot. 2621 If an LS receives a self-originated route update that is newer than 2622 the current version of the route at the LS, then the following 2623 actions MUST be taken. If the LS still wishes to advertise the 2624 information in the route, then the LS MUST increase the Sequence 2625 Number of the route to a value greater than that received in the 2626 UPDATE and re-originate the route. If the LS does not wish to 2627 continue to advertise the route, then it MUST purge the route as 2628 described in Section 10.1.5. 2630 10.1.7. Removing Withdrawn Routes 2632 An LS SHOULD ensure that routes marked as withdrawn are removed from 2633 the database in a timely fashion after the MaxPurgeTime has expired. 2634 This could be done, for example, by periodically sweeping the 2635 database, and deleting those entries that were withdrawn more than 2636 MaxPurgeTime seconds ago. 2638 10.2. Decision Process 2640 The Decision Process selects routes for subsequent advertisement by 2641 applying the policies in the local Policy Information Base (PIB) to 2642 the routes stored in its Adj-TRIBs-In. The output of the Decision 2643 Process is the set of routes that will be advertised to all peers; 2644 the selected routes will be stored in the local LS's Adj-TRIBs-Out. 2646 The selection process is formalized by defining a function that takes 2647 the attributes of a given route as an argument and returns a non- 2648 negative integer denoting the degree of preference for the route. The 2649 function that calculates the degree of preference for a given route 2650 shall not use as its inputs any of the following: the existence of 2651 other routes, the non-existence of other routes, or the attributes of 2652 other routes. Route selection then consists of individual application 2653 of the degree of preference function to each feasible route, followed 2654 by the choice of the one with the highest degree of preference. 2656 All internal LSs in an ITAD MUST run the Decision Process and apply 2657 the same decision criteria, otherwise it will not be possible to 2658 synchronize their Loc-TRIBs. 2660 The Decision Process operates on routes contained in each Adj-TRIBs- 2661 In, and is responsible for: 2663 - selection of routes to be advertised to internal peers 2664 - selection of routes to be advertised to external peers 2665 - route aggregation and route information reduction 2667 The Decision Process takes place in three distinct phases, each 2668 triggered by a different event: 2670 - Phase 1 is responsible for calculating the degree of preference 2671 for each route received from an external peer, and for 2672 advertising to all the internal peers the routes from external 2673 peers that have the highest degree of preference for each 2674 distinct destination. 2676 - Phase 2 is invoked on completion of phase 1. It is responsible 2677 for choosing the best route out of all those available for each 2678 distinct destination, and for installing each chosen route into 2679 the Loc-TRIB. 2680 - Phase 3 is invoked after the Loc-TRIB has been modified. It is 2681 responsible for disseminating routes in the Loc-TRIB to each 2682 external peer, according to the policies contained in the PIB. 2683 Route aggregation and information reduction can optionally be 2684 performed within this phase. 2686 10.2.1. Phase 1: Calculation of Degree of Preference 2688 The Phase 1 decision function shall be invoked whenever the local LS 2689 receives from a peer an UPDATE message that advertises a new route, a 2690 replacement route, or a withdrawn route. 2692 The Phase 1 decision function is a separate process that completes 2693 when it has no further work to do. 2695 The Phase 1 decision function shall lock an Adj-TRIB-In prior to 2696 operating on any route contained within it, and shall unlock it after 2697 operating on all new or replacement routes contained within it. 2699 The local LS MUST determine a degree of preference for each newly 2700 received or replacement route. If the route is learned from an 2701 internal peer, the value of the LocalPreference attribute MUST be 2702 taken as the degree of preference. If the route is learned from an 2703 external peer, then the degree of preference MUST be computed based 2704 on pre-configured policy information and used as the LocalPreference 2705 value in any intra-domain TRIP advertisement. The exact nature of 2706 this policy information and the computation involved is a local 2707 matter. 2709 The output of the degree of preference determination process is the 2710 local preference of a route. The local LS computes the local 2711 preference of routes learned from external peers or originated 2712 internally at that LS. The local preference of a route learned from 2713 an internal peer is included in the LocalPreference attribute 2714 associated with that route. 2716 10.2.2. Phase 2: Route Selection 2718 The Phase 2 decision function shall be invoked on completion of Phase 2719 1. The Phase 2 function is a separate process that completes when it 2720 has no further work to do. Phase 2 consists of two sub- phases: 2a 2721 and 2b. The same route selection function is applied in both sub- 2722 phases, but the inputs to each phase are different. The Phase 2a 2723 process MUST consider as inputs all external routes, that are present 2724 in the Adj-TRIBs-In of external peers, and all local routes. The 2725 output of Phase 2a is inserted into the Ext-TRIB. The Phase 2b 2726 process shall be invoked upon completion of Phase 2a and it MUST 2727 consider as inputs all routes in the Ext-TRIB and all routes that are 2728 present in the Adj-TRIBs-In of internal LSs. The output of Phase 2b 2729 is stored in the Loc-TRIB. 2731 The Phase 2 decision function MUST be blocked from running while the 2732 Phase 3 decision function is in process. The Phase 2 function MUST 2733 lock all Adj-TRIBs-In and the Ext-TRIB prior to commencing its 2734 function, and MUST unlock them on completion. 2736 If the LS determines that the NextHopServer listed in a route is 2737 unreachable, then the route MAY be excluded from the Phase 2 decision 2738 function. The means by which such a determination is made is not 2739 mandated here. 2741 For each set of destinations for which one or more routes exist, the 2742 local LS's route selection function MUST identify the route that has: 2744 - the highest degree of preference, or 2745 - is selected as a result of the tie breaking rules specified in 2746 10.2.2.1. 2748 Withdrawn routes MUST be removed from the Loc-TRIB, Ext-TRIB, and the 2749 Adj-TRIBs-In. 2751 10.2.2.1. Breaking Ties (Phase 2) 2753 Several routes to the same destination that have the same degree of 2754 preference may be input to the Phase 2 route selection function. The 2755 local LS can select only one of these routes for inclusion in the 2756 associated Ext-TRIB (Phase 2a) or Loc-TRIB (Phase 2b). The local LS 2757 considers all routes with the same degrees of preference. The 2758 following algorithm shall be used to break ties. 2760 - If the local LS is configured to use the MultiExitDisc attribute 2761 to break ties, and candidate routes received from the same 2762 neighboring ITAD differ in the value of the MultiExitDisc 2763 attribute, then select the route that has the larger value of 2764 MultiExitDisc. 2765 - If at least one of the routes was originated by an internal LS, 2766 select the route route that was advertised by the internal LS 2767 that has the lowest TRIP ID. 2769 - Otherwise, select the route that was advertised by the neighbor 2770 domain that has the lowest ITAD number. 2772 10.2.3. Phase 3: Route Dissemination 2774 The Phase 3 decision function MUST be invoked upon completion of 2775 Phase 2 if Phase 2 results in changes to the Loc-TRIB or when a new 2776 LS-to-LS peer session is established. 2778 The Phase 3 function is a separate process that completes when it has 2779 no further work to do. The Phase 3 routing decision function MUST be 2780 blocked from running while the Phase 2 decision function is in 2781 process. 2783 All routes in the Loc-TRIB shall be processed into a corresponding 2784 entry in the associated Adj-TRIBs-Out. Route aggregation and 2785 information reduction techniques (see 10.3.4) MAY optionally be 2786 applied. 2788 When the updating of the Adj-TRIBs-Out is complete, the local LS MUST 2789 run the external update process of 10.3.2. 2791 10.2.4. Overlapping Routes 2793 When overlapping routes are present in the same Adj-TRIB-In, the more 2794 specific route shall take precedence, in order from more specific to 2795 least specific. 2797 The set of destinations described by the overlap represents a portion 2798 of the less specific route that is feasible, but is not currently in 2799 use. If a more specific route is later withdrawn, the set of 2800 destinations described by the more specific route will still be 2801 reachable using the less specific route. 2803 If an LS receives overlapping routes, the Decision Process MUST take 2804 into account the semantics of the overlapping routes. In particular, 2805 if an LS accepts the less specific route while rejecting the more 2806 specific route from the same peer, then the destinations represented 2807 by the overlap may not forward along the domains listed in the 2808 AdvertisementPath attribute of that route. Therefore, an LS has the 2809 following choices: 2811 1. Install both the less and the more specific routes 2812 2. Install the more specific route only 2813 3. Install the non-overlapping part of the less specific route 2814 only (that implies disaggregation of the less-specific route) 2815 4. Aggregate the two routes and install the aggregated route 2816 5. Install the less specific route only 2817 6. Install neither route 2819 If an LS chooses 5), then it SHOULD add AtomicAggregate attribute to 2820 the route. A route that carries AtomicAggregate attribute MUST NOT be 2821 de-aggregated. That is, the route cannot be made more specific. 2822 Forwarding along such a route does not guarantee that route traverses 2823 only domains listed in the RoutedPath of the route. If an LS chooses 2824 1), then it MUST NOT advertise the more general route without the 2825 more specific route. 2827 10.3. Update-Send Process 2829 The Update-Send process is responsible for advertising UPDATE 2830 messages to all peers. For example, it distributes the routes chosen 2831 by the Decision Process to other LSs that may be located in either 2832 the same ITAD or a neighboring ITAD. Rules for information exchange 2833 between peer LSs located in different ITADs are given in 10.3.2; 2834 rules for information exchange between peer LSs located in the same 2835 ITAD are given in 10.3.1. 2837 Before forwarding routes to peers, an LS MUST determine which 2838 attributes should be forwarded along with that route. If a not well- 2839 known non-transitive attribute is unrecognized, it is quietly 2840 ignored. If a not well-known dependent-transitive attribute is 2841 unrecognized, and the NextHopServer attribute has been changed by the 2842 LS, the unrecognized attribute is quietly ignored. If a not well- 2843 known dependent-transitive attribute is unrecognized, and the 2844 NextHopServer attribute has not been modified by the LS, the Partial 2845 bit in the attribute flags octet is set to 1, and the attribute is 2846 retained for propagation to other TRIP speakers. Similarly, if an not 2847 well-known independent-transitive attribute is unrecognized, the 2848 Partial bit in the attribute flags octet is set to 1, and the 2849 attribute is retained for propagation to other TRIP speakers. 2851 If a not well-known attribute is recognized, and has a valid value, 2852 then, depending on the type of the not well-known attribute, it is 2853 updated, if necessary, for possible propagation to other TRIP 2854 speakers. 2856 10.3.1. Internal Updates 2858 The Internal update process is concerned with the distribution of 2859 routing information to internal peers. 2861 When an LS receives an UPDATE message from another TRIP LS located in 2862 its own ITAD, it is flooded as described in Section 10.1. 2864 When an LS receives a new route from an LS in a neighboring ITAD, or 2865 if a local route is injected into TRIP, the LS determines the 2866 preference of that route. If the new route has the highest degree of 2867 preference for all external routes and local routes to a given 2868 destination (or if the route was selected via a tie-breaking 2869 procedure as specified in 10.3.1.1), the LS MUST insert that new 2870 route into the Ext-TRIB database and the LS MUST advertise that route 2871 to all other LSs in its ITAD by means of an UPDATE message. The LS 2872 MUST advertise itself as the Originator of that route within the 2873 ITAD. 2875 When an LS receives an UPDATE message with a non-empty 2876 WithdrawnRoutes attribute from an external peer, or if a local route 2877 is withdrawn from TRIP, the LS MUST remove from its Adj-TRIB-In all 2878 routes whose destinations were carried in this field. If the 2879 withdrawn route was previously selected into the Ext-TRIB, the LS 2880 MUST take the following additional steps: 2882 - If a new route is selected for advertisement for those 2883 destinations, then the LS MUST insert the replacement route into 2884 Ext-TRIB to replace the withdrawn route and advertise it to all 2885 internal LSs. 2886 - If a replacement route is not available for advertisement, then 2887 the LS MUST include the destinations of the route in the 2888 WithdrawnRoutes attribute of an UPDATE message, and MUST send 2889 this message to each internal peer. The LS MUST also remove the 2890 withdrawn route from the Ext-TRIB. 2892 10.3.1.1. Breaking Ties (Routes Received from External Peers) 2894 If an LS has connections to several external peers, there will be 2895 multiple Adj-TRIBs-In associated with these peers. These databases 2896 might contain several equally preferable routes to the same 2897 destination, all of which were advertised by external peers. The 2898 local LS shall select one of these routes according to the following 2899 rules: 2901 - If the LS is configured to use the MultiExitDisc attribute to 2902 break ties, and the candidate routes differ in the value of the 2903 MultiExitDisc attribute, then select the route that has the 2904 lowest value of MultiExitDisc, else 2905 - Select the route that was advertised by the external LS that has 2906 the lowest TRIP Identifier. 2908 10.3.2. External Updates 2910 The external update process is concerned with the distribution of 2911 routing information to external peers. As part of Phase 3 route 2912 selection process, the LS has updated its Adj-TRIBs-Out. All newly 2913 installed routes and all newly unfeasible routes for which there is 2914 no replacement route MUST be advertised to external peers by means of 2915 UPDATE messages. 2917 Any routes in the Loc-TRIB marked as withdrawn MUST be removed. 2918 Changes to the reachable destinations within its own ITAD SHALL also 2919 be advertised in an UPDATE message. 2921 10.3.3. Controlling Routing Traffic Overhead 2923 The TRIP protocol constrains the amount of routing traffic (that is, 2924 UPDATE messages) in order to limit both the link bandwidth needed to 2925 advertise UPDATE messages and the processing power needed by the 2926 Decision Process to digest the information contained in the UPDATE 2927 messages. 2929 10.3.3.1. Frequency of Route Advertisement 2931 The parameter MinRouteAdvertisementInterval determines the minimum 2932 amount of time that must elapse between advertisements of routes to a 2933 particular destination from a single LS. This rate limiting procedure 2934 applies on a per-destination basis, although the value of 2935 MinRouteAdvertisementInterval is set on a per LS peer basis. 2937 Two UPDATE messages sent from a single LS that advertise feasible 2938 routes to some common set of destinations received from external 2939 peers MUST be separated by at least MinRouteAdvertisementInterval. 2940 Clearly, this can only be achieved precisely by keeping a separate 2941 timer for each common set of destinations. This would be unwarranted 2942 overhead. Any technique which ensures that the interval between two 2943 UPDATE messages sent from a single LS that advertise feasible routes 2944 to some common set of destinations received from external peers will 2945 be at least MinRouteAdvertisementInterval, and will also ensure a 2946 constant upper bound on the interval is acceptable. 2948 Two UPDATE messages, sent from a single LS to an external peer, that 2949 advertise feasible routes to some common set of destinations received 2950 from internal peers MUST be separated by at least 2951 MinRouteAdvertisementInterval. 2953 Since fast convergence is needed within an ITAD, this rate limiting 2954 procedure does not apply to routes received from internal peers and 2955 being broadcast to other internal peers. To avoid long-lived black 2956 holes, the procedure does not apply to the explicit withdrawal of 2957 routes (that is, routes whose destinations explicitly withdrawn by 2958 UPDATE messages. 2960 This procedure does not limit the rate of route selection, but only 2961 the rate of route advertisement. If new routes are selected multiple 2962 times while awaiting the expiration of MinRouteAdvertisementInterval, 2963 the last route selected shall be advertised at the end of 2964 MinRouteAdvertisementInterval. 2966 10.3.3.2. Frequency of Route Origination 2968 The parameter MinITADOriginationInterval determines the minimum 2969 amount of time that must elapse between successive advertisements of 2970 UPDATE messages that report changes within the advertising LS's own 2971 ITAD. 2973 10.3.3.3. Jitter 2975 To minimize the likelihood that the distribution of TRIP messages by 2976 a given LS will contain peaks, jitter should be applied to the timers 2977 associated with MinITADOriginationInterval, KeepAlive, and 2978 MinRouteAdvertisementInterval. A given LS shall apply the same jitter 2979 to each of these quantities regardless of the destinations to which 2980 the updates are being sent; that is, jitter will not be applied on a 2981 "per peer" basis. 2983 The amount of jitter to be introduced shall be determined by 2984 multiplying the base value of the appropriate timer by a random 2985 factor that is uniformly distributed in the range from 0.75 to 1.0. 2987 10.3.4. Efficient Organization of Routing Information 2989 Having selected the routing information that it will advertise, a 2990 TRIP speaker may use methods to organize this information in an 2991 efficient manner. These methods are discussed in the following 2992 sections. 2994 10.3.4.1. Information Reduction 2996 Information reduction may imply a reduction in granularity of policy 2997 control - after information is collapsed, the same policies will 2998 apply to all destinations and paths in the equivalence class. 3000 The Decision Process may optionally reduce the amount of information 3001 that it will place in the Adj-TRIBs-Out by any of the following 3002 methods: 3004 - ReachableRoutes: A set of destinations can be usually represented 3005 in compact form. For example, a set of E.164 phone numbers can be 3006 represented in more compact form using E.164 prefixes. 3007 - AdvertisementPath: AdvertisementPath information can be 3008 represented as ordered AP_SEQUENCEs or unordered AP_SETs. AP_SETs 3009 are used in the route aggregation algorithm described in Section 3010 5.4.4. They reduce the size of the AP_PATH information by listing 3011 each ITAD number only once, regardless of how many times it may 3012 have appeared in multiple advertisement paths that were 3013 aggregated. 3015 An AP_SET implies that the destinations advertised in the UPDATE 3016 message can be reached through paths that traverse at least some of 3017 the constituent ITADs. AP_SETs provide sufficient information to 3018 avoid route looping; however their use may prune potentially feasible 3019 paths, since such paths are no longer listed individually as in the 3020 form of AP_SEQUENCEs. In practice this is not likely to be a problem, 3021 since once a call arrives at the edge of a group of ITADs, the LS at 3022 that point is likely to have more detailed path information and can 3023 distinguish individual paths to destinations. 3025 10.3.4.2. Aggregating Routing Information 3027 Aggregation is the process of combining the characteristics of 3028 several different routes in such a way that a single route can be 3029 advertised. Aggregation can occur as part of the decision process to 3030 reduce the amount of routing information that is placed in the Adj- 3031 TRIBs-Out. 3033 Aggregation reduces the amount of information an LS must store and 3034 exchange with other LSs. Routes can be aggregated by applying the 3035 following procedure separately to attributes of like type. 3037 Routes that have the following attributes shall not be aggregated 3038 unless the corresponding attributes of each route are identical: 3039 MultiExitDisc, NextHopServer. 3041 Attributes that have different type codes cannot be aggregated. 3042 Attributes of the same type code may be aggregated. The rules for 3043 aggregating each attribute MUST be provided together with attribute 3044 definition. For example, aggregation rules for TRIP's basic 3045 attributes, e.g., ReachableRoutes and AdvertisementPath, are given in 3046 Section 5. 3048 10.4. Route Selection Criteria 3050 Generally speaking, additional rules for comparing routes among 3051 several alternatives are outside the scope of this document. There 3052 are two exceptions: 3054 - If the local ITAD appears in the AdvertisementPath of the new 3055 route being considered, then that new route cannot be viewed as 3056 better than any other route. If such a route were ever used, a 3057 routing loop could result (see Section 6.3). 3058 - In order to achieve successful distributed operation, only routes 3059 with a likelihood of stability can be chosen. Thus, an ITAD must 3060 avoid using unstable routes, and it must not make rapid 3061 spontaneous changes to its choice of route. Quantifying the terms 3062 "unstable" and "rapid" in the previous sentence will require 3063 experience, but the principle is clear. 3065 10.5. Originating TRIP Routes 3067 An LS may originate local routes by injecting routing information 3068 acquired by some other means (e.g. via an intra-domain routing 3069 protocol or through manual configuration or some dynamic registration 3070 mechanism/protocol) into TRIP. An LS that originates TRIP routes 3071 shall assign the degree of preference to these routes by passing them 3072 through the Decision Process (see Section 10.2). To TRIP local routes 3073 are identical to external routes and are subjected to the same two 3074 phase route selection mechanism. A local route which is selected into 3075 the Ext-TRIB MUST be advertised to all internal LSs. The decision 3076 whether to distribute non-TRIP acquired routes within an ITAD via 3077 TRIP or not depends on the environment within the ITAD (e.g. type of 3078 intra-domain routing protocol) and should be controlled via 3079 configuration. 3081 11. TRIP Transport 3083 This specification defines the use of TCP as the transport layer for 3084 TRIP. TRIP uses TCP port 6069. Running TRIP over other transport 3085 protocols is for further study. 3087 12. ITAD Topology 3089 There are no restrictions on the intra-domain topology of TRIP LSs. 3090 For example, LSs in an ITAD can be configured in a full mesh, star, 3091 or any other connected topology. Similarly, there are no restrictions 3092 on the topology of TRIP ITADs. For example, the ITADs can be 3093 organized in a flat topology (mesh or ring) or in multi-level 3094 hierarchy or any other topology. 3096 The border between two TRIP ITADs may be located either on the link 3097 between two TRIP LSs or it may coincide on a TRIP LS. In the latter 3098 case, the same TRIP LS will be member in more than one ITAD, and it 3099 appears to be an internal peer to LSs in each ITAD it is member of. 3101 13. IANA Considerations 3103 This document creates a new IANA registry for TRIP parameters. The 3104 following TRIP parameters are included in the registry: 3105 - TRIP Capabilities 3106 - TRIP Attributes 3107 - TRIP Address Families 3108 - TRIP Application Protocols 3109 - TRIP ITAD Numbers 3110 The sub-registries for each of these parameters are discussed in the 3111 sections below. 3113 13.1. TRIP Capabilities 3115 Requests to add TRIP capabilities other than those defined in Section 3116 4.2.1.1 must be submitted to iana@iana.org. Following the assigned 3117 number policies outlined in [11], Capability Codes in the range 3118 32768-65535 are reserved for Private Use (these are the codes with 3119 the first bit of the code value equal to 1). This document reserves 3120 value 0. Capability Codes 1 and 2 have been assigned in Section 3121 4.2.1.1. Capability Codes in the range 2-32767 are controlled by 3122 IANA, and are allocated subject to the Specification Required (IETF 3123 RFC or equivalent) condition. The specification MUST include a 3124 description of the capability, the possible values it may take, and 3125 what constitutes a capability mismatch. 3127 13.2. TRIP Attributes 3129 This document reserves Attribute Type Codes 224-255 for Private Use 3130 (these are the codes with the first three bits of the code equal to 3131 1). This document reserves value 0. Attribute Type Codes 1 through 11 3132 have already been allocated by this document. Attribute Type Codes 1 3133 through 11 are defined in Sections 5.1 through 5.11. 3135 Attribute Type Codes in the range 12-223 are controlled by IANA, and 3136 require a Specification document (RFC or equivalent). The 3137 specification MUST provide all information required in Section 5.12 3138 of this document. 3140 Attribute Type Code registration requests must be sent to 3141 iana@iana.org. In addition to the specification requirement, the 3142 request MUST include an indication of who has change control over the 3143 attribute and contact information (postal and email address). 3145 13.3. Destination Address Families 3147 This document reserves address family 0. Requests to add TRIP address 3148 families other than those defined in Section 5.1.1.1 ( address 3149 families 1, 2, and 3), i.e., in the range 3-32767, must be submitted 3150 to iana@iana.org. The request MUST include a brief description of the 3151 address family, its alphabet, and special processing rules and 3152 guidelines, such as guidelines for aggregation, if any. The requests 3153 are subject to Expert Review. This document reserves addresss family 3154 codes 32768-65535 for vendor-specific applications. 3156 13.4. TRIP Application Protocols 3158 This document creates a new IANA registry for TRIP application 3159 protocols. This document reserves application protocol code 0. 3160 Requests to add TRIP application protocols other than those defined 3161 in Section 5.1.1.1 (application protocols 1 through 4), i.e., in the 3162 range 5- 32767 must be submitted to iana@iana.org. The request MUST 3163 include a brief background on the application protocol, and a 3164 description of how TRIP can be used to advertise routes for that 3165 protocol. The requests are subject to Expert Review. This document 3166 reserves application protocol codes 32768-65535 for vendor-specific 3167 applications. 3169 13.5. ITAD Numbers 3171 This document reserves ITAD number 0. ITAD numbers in the range 1- 3172 255 are designated for Private Use. ITAD numbers in the range from 3173 256 to (2**32-1) are allocated by IANA on a First-Come-First-Serve 3174 basis. Requests for ITAD numbers must be submitted to iana@iana.org. 3175 The requests MUST include the following: 3176 - Information about the organization that will administer the ITAD. 3177 - Contact information (postal and email address). 3179 14. Security Considerations 3181 This section covers security between peer TRIP LSs when TRIP runs 3182 over TCP in an IP environment. 3184 A security mechanism is clearly needed to prevent unauthorized 3185 entities from using the protocol defined in this document for setting 3186 up unauthorized peer sessions with other TRIP LSs or interfering with 3187 authorized peer sessions. The security mechanism for the protocol 3188 when transported over TCP in an IP network is IPsec [12]. IPsec uses 3189 two protocols to provide traffic security: Authentication Header (AH) 3190 [13] and Encapsulating Security Payload (ESP) [14]. 3192 The AH header affords data origin authentication, connectionless 3193 integrity and optional anti-replay protection of messages passed 3194 between the peer LSs. The ESP header provides origin authentication, 3195 connectionless integrity, anti-replay protection, and, in addition, 3196 confidentiality of messages. 3198 Implementations of the protocol defined in this document employing 3199 the ESP header SHALL comply with section 5 of [14], which defines a 3200 minimum set of algorithms for integrity checking and encryption. 3201 Similarly, implementations employing the AH header SHALL comply with 3202 section 5 of [13], which defines a minimum set of algorithms for 3203 integrity checking using manual keys. 3205 Implementations SHOULD use IKE [15] to permit more robust keying 3206 options. Implementations employing IKE SHOULD support authentication 3207 with RSA signatures and RSA public key encryption. 3209 A Security Association (SA) [12] is a simplex "connection" that 3210 affords security services to the traffic carried by it. Security 3211 services are afforded to an SA by the use of AH, or ESP, but not 3212 both. Two types of SAs are defined: transport mode and tunnel mode 3213 [12]. A transport mode SA is a security association between two 3214 hosts, and is appropriate for protecting the TRIP session between two 3215 peer LSs. 3217 Appendix 1: TRIP FSM State Transitions and Actions 3219 This Appendix discusses the transitions between states in the TRIP 3220 FSM in response to TRIP events. The following is the list of these 3221 states and events when the negotiated Hold Time value is non-zero. 3223 TRIP States: 3224 1 - Idle 3225 2 - Connect 3226 3 - Active 3227 4 - OpenSent 3228 5 - OpenConfirm 3229 6 - Established 3231 TRIP Events: 3232 1 - TRIP Start 3233 2 - TRIP Stop 3234 3 - TRIP Transport connection open 3235 4 - TRIP Transport connection closed 3236 5 - TRIP Transport connection open failed 3237 6 - TRIP Transport fatal error 3238 7 - ConnectRetry timer expired 3239 8 - Hold Timer expired 3240 9 - KeepAlive timer expired 3241 10 - Receive OPEN message 3242 11 - Receive KEEPALIVE message 3243 12 - Receive UPDATE messages 3244 13 - Receive NOTIFICATION message 3246 The following table describes the state transitions of the TRIP FSM 3247 and the actions triggered by these transitions. 3249 Event Actions Message Sent Next State 3250 -------------------------------------------------------------------- 3251 Idle (1) 3252 1 Initialize resources none 2 3253 Start ConnectRetry timer 3254 Initiate a transport connection 3255 others none none 1 3257 Connect(2) 3258 1 none none 2 3259 3 Complete initialization OPEN 4 3260 Clear ConnectRetry timer 3261 5 Restart ConnectRetry timer none 3 3262 7 Restart ConnectRetry timer none 2 3263 Initiate a transport connection 3264 others Release resources none 1 3266 Active (3) 3267 1 none none 3 3268 3 Complete initialization OPEN 4 3269 Clear ConnectRetry timer 3270 5 Close connection 3 3271 Restart ConnectRetry timer 3272 7 Restart ConnectRetry timer none 2 3273 Initiate a transport connection 3274 others Release resources none 1 3276 OpenSent(4) 3277 1 none none 4 3278 4 Close transport connection none 3 3279 Restart ConnectRetry timer 3280 6 Release resources none 1 3281 10 Process OPEN is OK KEEPALIVE 5 3282 Process OPEN failed NOTIFICATION 1 3283 others Close transport connection NOTIFICATION 1 3284 Release resources 3286 OpenConfirm (5) 3287 1 none none 5 3288 4 Release resources none 1 3289 6 Release resources none 1 3290 9 Restart KeepAlive timer KEEPALIVE 5 3291 11 Complete initialization none 6 3292 Restart Hold Timer 3293 13 Close transport connection 1 3294 Release resources 3295 others Close transport connection NOTIFICATION 1 3296 Release resources 3298 Established (6) 3299 1 none none 6 3300 4 Release resources none 1 3301 6 Release resources none 1 3302 9 Restart KeepAlive timer KEEPALIVE 6 3303 11 Restart Hold Timer KEEPALIVE 6 3304 12 Process UPDATE is OK UPDATE 6 3305 Process UPDATE failed NOTIFICATION 1 3306 13 Close transport connection 1 3307 Release resources 3308 others Close transport connection NOTIFICATION 1 3309 Release resources 3310 ----------------------------------------------------------------- 3312 The following is a condensed version of the above state transition 3313 table. 3315 Events| Idle | Connect | Active | OpenSent | OpenConfirm | Estab 3316 | (1) | (2) | (3) | (4) | (5) | (6) 3317 |---------------------------------------------------------- 3318 1 | 2 | 2 | 3 | 4 | 5 | 6 3319 | | | | | | 3320 2 | 1 | 1 | 1 | 1 | 1 | 1 3321 | | | | | | 3322 3 | 1 | 4 | 4 | 1 | 1 | 1 3323 | | | | | | 3324 4 | 1 | 1 | 1 | 3 | 1 | 1 3325 | | | | | | 3326 5 | 1 | 3 | 3 | 1 | 1 | 1 3327 | | | | | | 3328 6 | 1 | 1 | 1 | 1 | 1 | 1 3329 | | | | | | 3330 7 | 1 | 2 | 2 | 1 | 1 | 1 3331 | | | | | | 3332 8 | 1 | 1 | 1 | 1 | 1 | 1 3333 | | | | | | 3334 9 | 1 | 1 | 1 | 1 | 5 | 6 3335 | | | | | | 3336 10 | 1 | 1 | 1 | 1 or 5 | 1 | 1 3337 | | | | | | 3338 11 | 1 | 1 | 1 | 1 | 6 | 6 3339 | | | | | | 3340 12 | 1 | 1 | 1 | 1 | 1 | 1 or 6 3341 | | | | | | 3342 13 | 1 | 1 | 1 | 1 | 1 | 1 3343 | | | | | | 3344 -------------------------------------------------------------- 3346 Appendix 2: Implementation Recommendations 3348 This section presents some implementation recommendations. 3350 A.2.1: Multiple Networks Per Message 3352 The TRIP protocol allows for multiple address prefixes with the same 3353 advertisement path and next-hop server to be specified in one 3354 message. Making use of this capability is highly recommended. With 3355 one address prefix per message there is a substantial increase in 3356 overhead in the receiver. Not only does the system overhead increase 3357 due to the reception of multiple messages, but the overhead of 3358 scanning the routing table for updates to TRIP peers is incurred 3359 multiple times as well. One method of building messages containing 3360 many address prefixes per advertisement path and next hop from a 3361 routing table that is not organized per advertisement path is to 3362 build many messages as the routing table is scanned. As each address 3363 prefix is processed, a message for the associated advertisement path 3364 and next hop is allocated, if it does not exist, and the new address 3365 prefix is added to it. If such a message exists, the new address 3366 prefix is just appended to it. If the message lacks the space to hold 3367 the new address prefix, it is transmitted, a new message is 3368 allocated, and the new address prefix is inserted into the new 3369 message. When the entire routing table has been scanned, all 3370 allocated messages are sent and their resources released. Maximum 3371 compression is achieved when all the destinations covered by the 3372 address prefixes share a next hop server and common attributes, 3373 making it possible to send many address prefixes in one 4096-byte 3374 message. 3376 When peering with a TRIP implementation that does not compress 3377 multiple address prefixes into one message, it may be necessary to 3378 take steps to reduce the overhead from the flood of data received 3379 when a peer is acquired or a significant network topology change 3380 occurs. One method of doing this is to limit the rate of updates. 3381 This will eliminate the redundant scanning of the routing table to 3382 provide flash updates for TRIP peers. A disadvantage of this approach 3383 is that it increases the propagation latency of routing information. 3384 By choosing a minimum flash update interval that is not much greater 3385 than the time it takes to process the multiple messages this latency 3386 should be minimized. A better method would be to read all received 3387 messages before sending updates. 3389 A.2.2: Processing Messages on a Stream Protocol 3391 TRIP uses TCP as a transport mechanism. Due to the stream nature of 3392 TCP, all the data for received messages does not necessarily arrive 3393 at the same time. This can make it difficult to process the data as 3394 messages, especially on systems where it is not possible to determine 3395 how much data has been received but not yet processed. 3397 One method that can be used in this situation is to first try to read 3398 just the message header. For the KEEPALIVE message type, this is a 3399 complete message; for other message types, the header should first be 3400 verified, in particular the total length. If all checks are 3401 successful, the specified length, minus the size of the message 3402 header is the amount of data left to read. An implementation that 3403 would "hang" the routing information process while trying to read 3404 from a peer could set up a message buffer (4096 bytes) per peer and 3405 fill it with data as available until a complete message has been 3406 received. 3408 A.2.3: Reducing Route Flapping 3410 To avoid excessive route flapping an LS which needs to withdraw a 3411 destination and send an update about a more specific or less specific 3412 route SHOULD combine them into the same UPDATE message. 3414 A.2.4: TRIP Timers 3416 TRIP employs seven timers: ConnectRetry, Hold Time, KeepAlive, 3417 MaxPurgeTime, TripDisableTime, MinITADOriginationInterval, and 3418 MinRouteAdvertisementInterval The suggested value for the 3419 ConnectRetry timer is 120 seconds. The suggested value for the Hold 3420 Time is 90 seconds. The suggested value for the KeepAlive timer is 30 3421 seconds. The suggested value for the MaxPurgeTime timer is 10 3422 seconds. The suggested value for the TripDisableTime timer is 180 3423 seconds. The suggested value for the MinITADOriginationInterval is 30 3424 seconds. The suggested value for the MinRouteAdvertisementInterval is 3425 30 seconds. 3427 An implementation of TRIP MUST allow these timers to be configurable. 3429 A.2.5: AP_SET Sorting 3431 Another useful optimization that can be done to simplify this 3432 situation is to sort the ITAD numbers found in an AP_SET. This 3433 optimization is entirely optional. 3435 Acknowledgments 3437 We wish to thank Dave Oran for his insightful comments and 3438 suggestions. 3440 References 3442 [1] S. Bradner, "Keywords for use in RFCs to Indicate Requirement 3443 Levels," IETF RFC 2119, March 1997. 3445 [2] J. Rosenberg and H. Schulzrinne, "A Framework for a Gateway 3446 Location Protocol," IETF RFC 2871, June 2000. 3448 [3] Y. Rekhter and T. Li, "Border Gateway Protocol 4 (BGP-4)," IETF 3449 RFC 1771, March 1995. 3451 [4] J. Moy, "Open Shortest Path First Version 2," IETF RFC 2328, 3452 April, 1998. 3454 [5] "Intermediate System to Intermediate System Intra-Domain Routing 3455 Exchange Protocol for use in Conjunction with the 3456 Protocol for Providing the Connectionless-mode Network Service (ISO 3457 8473)," ISO DP 10589, February 1990. 3459 [6] J. Luciani, et al, "Server Cache Synchronization Protocol 3460 (SCSP)," IETF RFC 2334, April, 1998. 3462 [7] International Telecommunication Union, "Visual Telephone Systems 3463 and Equipment for Local Area Networks which Provide a Non-Guaranteed 3464 Quality of Service," Recommendation H.323, Telecommunication 3465 Standardization Sector of ITU, Geneva, Switzerland, May 1996. 3467 [8] M. Handley, H. Schulzrinne, E. Schooler, and J. Rosenberg, "SIP: 3468 Session Initiation Protocol," IETF RFC 2543, March 1999. 3470 [9] R. Braden, "Requirements for Internet Hosts -- Application and 3471 Support," IETF RFC 1123, October 1989. 3473 [10] R. Hinden and S. Deering, "IP Version 6 Addressing 3474 Architecture," IETF RFC 2373, July 1998. 3476 [11] T. Narten and H. Alvestrand, "Guidelines for Writing an IANA 3477 Considerations Section in RFCs," IETF RFC 2434, October 1998. 3479 [12] S. Kent and R. Atkinson, "Security Architecture for the Internet 3480 Protocol," IETF RFC 2401, November 1998. 3482 [13] S. Kent and R. Atkinson, "IP Authentication Header," IETF RFC 3483 2402, November 1998. 3485 [14] S. Kent and R. Atkinson, "IP Encapsulating Security Payload 3486 (ESP)," IETF RFC 2406, November 1998. 3488 [15] D. Harkins and D. Carrel, "The Internet Key Exchange (IKE)," 3489 IETF RFC 2409, November 1998. 3491 Authors' Addresses 3493 Jonathan Rosenberg 3494 dynamicsoft 3495 72 Eagle Rock Avenue 3496 First Floor 3497 East Hanover, NJ 07936 3498 973-952-5000 3499 email: jdrosen@dynamicsoft.com 3501 Hussein F. Salama 3502 Cisco Systems 3503 Mail Stop SJ-6/3 3504 170 W. Tasman Drive 3505 San Jose, CA 95134 3506 408-527-7147 3507 email: hsalama@cisco.com 3509 Matt Squire 3510 WindWire 3511 4825 Creekstone Drive 3512 Durham, NC 27703 3513 919-247-0820 3514 email: msquire@windwire.com 3516 Intellectual Property Notice 3518 The IETF takes no position regarding the validity or scope of any 3519 intellectual property or other rights that might be claimed to 3520 pertain to the implementation or use of the technology described in 3521 this document or the extent to which any license under such rights 3522 might or might not be available; neither does it represent that it 3523 has made any effort to identify any such rights. Information on the 3524 IETF's procedures with respect to rights in standards-track and 3525 standards-related documentation can be found in BCP-11. 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