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Chen 2 Internet Draft Renhai Zhang 3 Category: Standards Track Huawei Technologies Co.,Ltd 4 Created: July 27, 2008 Xiaodong Duan 5 Expires: January 27, 2009 China Mobile 7 OSPF Extensions in Support of Inter-AS Multiprotocol Label Switching 8 (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering 10 draft-ietf-ccamp-ospf-interas-te-extension-06.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that 15 any applicable patent or other IPR claims of which he or she is 16 aware have been or will be disclosed, and any of which he or she 17 becomes aware will be disclosed, in accordance with Section 6 of 18 BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six 26 months and may be updated, replaced, or obsoleted by other documents 27 at any time. It is inappropriate to use Internet-Drafts as 28 reference material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html 36 This Internet-Draft will expire on January 23, 2009. 38 Abstract 40 This document describes extensions to the OSPF version 2 and 3 41 protocols to support Multiprotocol Label Switching (MPLS) and 42 Generalized MPLS (GMPLS) Traffic Engineering (TE) for multiple 43 Autonomous Systems (ASes). OSPF-TE v2 and v3 extensions are defined 44 for the flooding of TE information about inter-AS links which can be 45 used to perform inter-AS TE path computation. 47 No support for flooding information from within one AS to another AS 48 is proposed or defined in this document. 50 Conventions used in this document 52 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 53 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 54 document are to be interpreted as described in RFC-2119 [RFC2119]. 56 Table of Contents 58 1. Introduction.................................................3 59 2. Problem Statement............................................3 60 2.1. A Note on Non-Objectives................................4 61 2.2. Per-Domain Path Determination...........................5 62 2.3. Backward Recursive Path Computation.....................6 63 3. Extensions to OSPF...........................................7 64 3.1. LSA Definitions.........................................8 65 3.1.1. Inter-AS-TE-v2 LSA.................................8 66 3.1.2. Inter-AS-TE-v3 LSA.................................9 67 3.2. LSA Payload.............................................9 68 3.2.1. Link TLV..........................................10 69 3.3. Sub-TLV Detail.........................................11 70 3.3.1. Remote AS Number Sub-TLV..........................11 71 3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................11 72 3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................12 73 4. Procedure for Inter-AS TE Links.............................13 74 4.1. Origin of Proxied TE Information.......................14 75 5. Security Considerations.....................................15 76 6. IANA Considerations.........................................15 77 6.1. Inter-AS TE OSPF LSA...................................16 78 6.1.1. Inter-AS-TE-v2 LSA................................16 79 6.1.2. Inter-AS-TE-v3 LSA................................16 80 6.2. OSPF LSA Sub-TLVs type.................................16 81 7. Acknowledgments.............................................16 82 8. References..................................................16 83 8.1. Normative References...................................16 84 8.2. Informative References.................................17 85 Authors' Addresses.............................................18 86 Intellectual Property Statement................................18 87 Disclaimer of Validity.........................................19 88 Copyright Statement............................................19 90 1. Introduction 92 [OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support 93 intra-area Traffic Engineering (TE). The extensions provide a way of 94 encoding the TE information for TE-enabled links within the network 95 (TE links) and flooding this information within an area. Type 10 96 opaque Link State Advertisements (LSAs) [RFC5250] are used to carry 97 such TE information. Two top-level Type Length Values (TLVs) are 98 defined in [OSPF-TE]: Router Address TLV and Link TLV. The Link TLV 99 has several nested sub-TLVs which describe the TE attributes for a 100 TE link. 102 [OSPF-V3-TE] defines similar extensions to OSPFv3 [OSPFV3]. It 103 defines a new LSA, which is referred to as the Intra-Area-TE LSA, to 104 advertise TE information. [OSPF-V3-TE] uses "Traffic Engineering 105 Extensions to OSPF" [OSPF-TE] as a base for TLV definitions and 106 defines some new TLVs and sub-TLVs to extend TE capabilities to IPv6 107 networks. 109 Requirements for establishing Multiprotocol Label Switching Traffic 110 Engineering (MPLS-TE) Label Switched Paths (LSPs) that cross 111 multiple Autonomous Systems (ASes) are described in [INTER-AS-TE- 112 REQ]. As described in [INTER-AS-TE-REQ], a method SHOULD provide the 113 ability to compute a path spanning multiple ASes. So a path 114 computation entity that may be the head-end Label Switching Router 115 (LSR), an AS Border Router (ASBR), or a Path Computation Element 116 (PCE [PCE]) needs to know the TE information not only of the links 117 within an AS, but also of the links that connect to other ASes. 119 In this document, two new separate LSAs are defined to advertise 120 inter-AS TE information for OSPFv2 and OSPFv3 respectively, and 121 three new sub-TLVs are added to the existing Link TLV to extend TE 122 capabilities for inter-AS Traffic Engineering. The detailed 123 definitions and procedures are discussed in the following sections. 125 This document does not propose or define any mechanisms to advertise 126 any other extra-AS TE information within OSPF. See Section 2.1 for a 127 full list of non-objectives for this work. 129 2. Problem Statement 131 As described in [INTER-AS-TE-REQ], in the case of establishing an 132 inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] 133 may include the following elements in the Explicit Route Object (ERO) 134 in order to describe the path of the LSP: 136 - a set of AS numbers as loose hops; and/or 138 - a set of LSRs including ASBRs as loose hops. 140 Two methods for determining inter-AS paths are currently being 141 discussed. The per-domain method [PD-PATH] determines the path one 142 domain at a time. The backward recursive method [BRPC] uses 143 cooperation between PCEs to determine an optimum inter-domain path. 144 The sections that follow examine how inter-AS TE link information 145 could be useful in both cases. 147 2.1. A Note on Non-Objectives 149 It is important to note that this document does not make any change 150 to the confidentiality and scaling assumptions surrounding the use 151 of ASes in the Internet. In particular, this document is conformant 152 to the requirements set out in [INTER-AS-TE-REQ]. 154 The following features are explicitly excluded: 156 o There is no attempt to distribute TE information from within one 157 AS to another AS. 159 o There is no mechanism proposed to distribute any form of TE 160 reachability information for destinations outside the AS. 162 o There is no proposed change to the PCE architecture or usage. 164 o TE aggregation is not supported or recommended. 166 o There is no exchange of private information between ASes. 168 o No OSPF adjacencies are formed on the inter-AS link. 170 Note also that the extensions proposed in this document are used 171 only to advertise information about inter-AS TE links. As such these 172 extensions address an entirely different problem from L1VPN Auto- 173 Discovery [L1VPN-OSPF-AD] which defines how TE information about 174 links between Customer Edge (CE) equipment and Provider Edge (PE) 175 equipment can be advertised in OSPF-TE alongside the auto-discovery 176 information for the CE-PE links. There is no overlap between this 177 document and [L1VPN-OSPF-AD]. 179 2.2. Per-Domain Path Determination 181 In the per-domain method of determining an inter-AS path for an 182 MPLS-TE LSP, when an LSR that is an entry-point to an AS receives a 183 Path message from an upstream AS with an ERO containing a next hop 184 that is an AS number, it needs to find which LSRs (ASBRs) within the 185 local AS are connected to the downstream AS so that it can compute a 186 TE LSP segment across the local AS to one of those LSRs and forward 187 the Path message to it and hence into the next AS. See Figure 1 for 188 an example: 190 R1------R3----R5-----R7------R9-----R11 191 | | \ | / | 192 | | \ | ---- | 193 | | \ | / | 194 R2------R4----R6 --R8------R10----R12 195 : : 196 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 198 Figure 1: Inter-AS Reference Model 200 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 201 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 202 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 204 If an inter-AS TE LSP is planned to be established from R1 to R12, 205 the AS sequence will be: AS1, AS2, AS3. 207 Suppose that the Path message enters AS2 from R3. The next hop in 208 the ERO shows AS3, and R5 must determine a path segment across AS2 209 to reach AS3. It has a choice of three exit points from AS2 (R6, R7, 210 and R8) and it needs to know which of these provide TE connectivity 211 to AS3, and whether the TE connectivity (for example, available 212 bandwidth) is adequate for the requested LSP. 214 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 215 (say R9), R5 needs to know which of its exit ASBRs has a TE link 216 that connects to R9. Since there may be multiple ASBRs that are 217 connected to R9 (both R7 and R8 in this example), R5 also needs to 218 know the TE properties of the inter-AS TE links so that it can 219 select the correct exit ASBR. 221 Once the path message reaches the exit ASBR, any choice of inter-AS 222 TE link can be made by the ASBR if not already made by entry ASBR 223 that computed the segment. 225 More details can be found in the Section 4. of [PD-PATH], which 226 clearly points out why advertising of inter-AS links is desired. 228 To enable R5 to make the correct choice of exit ASBR the following 229 information is needed: 231 o List of all inter-AS TE links for the local AS. 233 o TE properties of each inter-AS TE link. 235 o AS number of the neighboring AS connected to by each inter-AS TE 236 link. 238 o Identity (TE Router ID) of the neighboring ASBR connected to by 239 each inter-AS TE link. 241 In GMPLS networks further information may also be required to select 242 the correct TE links as defined in [GMPLS-TE]. 244 The example above shows how this information is needed at the entry 245 point ASBRs for each AS (or the PCEs that provide computation 246 services for the ASBRs), but this information is also needed 247 throughout the local AS if path computation function is fully 248 distributed among LSRs in the local AS, for example to support LSPs 249 that have start points (ingress nodes) within the AS. 251 2.3. Backward Recursive Path Computation 253 Another scenario using PCE techniques has the same problem. [BRPC] 254 defines a PCE-based TE LSP computation method (called Backward 255 Recursive Path Computation) to compute optimal inter-domain 256 constrained MPLS-TE or GMPLS LSPs. In this path computation method, 257 a specific set of traversed domains (ASes) are assumed to be 258 selected before computation starts. Each downstream PCE in domain(i) 259 returns to its upstream neighbor PCE in domain(i-1) a multipoint-to- 260 point tree of potential paths. Each tree consists of the set of 261 paths from all Boundary Nodes located in domain(i) to the 262 destination where each path satisfies the set of required 263 constraints for the TE LSP (bandwidth, affinities, etc.). 265 So a PCE needs to select Boundary Nodes (that is, ASBRs) that 266 provide connectivity from the upstream AS. In order that the tree of 267 paths provided by one PCE to its neighbor can be correlated, the 268 identities of the ASBRs for each path need to be referenced, so the 269 PCE must know the identities of the ASBRs in the remote AS reached 270 by any inter-AS TE link, and, in order that it provides only 271 suitable paths in the tree, the PCE must know the TE properties of 272 the inter-AS TE links. See the following figure as an example: 274 PCE1<------>PCE2<-------->PCE3 275 / : : 276 / : : 277 R1------R3----R5-----R7------R9-----R11 278 | | \ | / | 279 | | \ | ---- | 280 | | \ | / | 281 R2------R4----R6 --R8------R10----R12 282 : : 283 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 285 Figure 2: BRPC for Inter-AS Reference Model 287 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 288 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 289 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 290 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS 291 path computation and are responsible for path segment computation 292 within their own domain(s). 294 If an inter-AS TE LSP is planned to be established from R1 to R12, 295 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 296 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 297 request originated from the PCC (R1) is relayed by PCE1 and PCE2 298 along the PCE chain to PCE3, then PCE3 begins to compute the path 299 segments from the entry boundary nodes that provide connection from 300 AS2 to the destination (R12). But, to provide suitable path segments, 301 PCE3 must determine which entry boundary nodes provide connectivity 302 to its upstream neighbor AS (identified by its AS number), and must 303 know the TE properties of the inter-AS TE links. In the same way, 304 PCE2 also needs to determine the entry boundary nodes according to 305 its upstream neighbor AS and the inter-AS TE link capabilities. 307 Thus, to support Backward Recursive Path Computation the same 308 information listed in Section 2.2 is required. The AS number of the 309 neighboring AS connected to by each inter-AS TE link is particularly 310 important. 312 3. Extensions to OSPF 314 Note that this document does not define mechanisms for distribution 315 of TE information from one AS to another, does not distribute any 316 form of TE reachability information for destinations outside the AS, 317 does not change the PCE architecture or usage, does not suggest or 318 recommend any form of TE aggregation, and does not feed private 319 information between ASes. See section 2.1. 321 The extensions defined in this document allow an inter-AS TE link 322 advertisement to be easily identified as such by the use of two new 323 types of LSA, which are referred to as Inter-AS-TE-v2 LSA and Inter- 324 AS-TE-v3 LSA. Three new sub-TLVs are added to the Link TLV to carry 325 the information about the neighboring AS and the remote ASBR. 327 While some of the TE information of an inter-AS TE link may be 328 available within the AS from other protocols, in order to avoid any 329 dependency on where such protocols are processed, this mechanism 330 carries all the information needed for the required TE operations. 332 3.1. LSA Definitions 334 3.1.1. Inter-AS-TE-v2 LSA 336 For the advertisement of OSPFv2 inter-AS TE links, a new Opaque LSA, 337 the Inter-AS-TE-v2 LSA, is defined in this document. The Inter-AS- 338 TE-v2 LSA has the same format as "Traffic Engineering LSA" which is 339 defined in [OSPF-TE]. 341 The inter-AS TE link advertisement SHOULD be carried in a Type 10 342 Opaque LSA if the flooding scope is to be limited to within the 343 single IGP area to which the ASBR belongs, or MAY be carried in a 344 Type 11 Opaque LSA if the information is intended to reach all 345 routers (including area border routers, ASBRs, and PCEs) in the AS. 346 The choice between the use of a Type 10 or Type 11 Opaque LSA is a 347 AS-wide policy choice, and configuration control of it SHOULD be 348 provided in ASBR implementations that support the advertisement of 349 inter-AS TE links. 351 The Link State ID of an Opaque LSA as defined in [RFC5250] is 352 divided into two parts. One of them is the Opaque type (8-bit), the 353 other is the Opaque ID (24-bit). The suggested value for the Opaque 354 type of Inter-AS-TE-v2 LSA is TBD and will be assigned by IANA (see 355 Section 6.1). We suggest the value 6. The Opaque ID (in this 356 document called the Instance) of the Inter-AS-TE-v2 LSA is an 357 arbitrary value used to uniquely identify Traffic Engineering LSAs. 358 The Link State ID has no topological significance. 360 The TLVs within the body of an Inter-AS-TE-v2 LSA have the same 361 format as used in OSPF-TE. The payload of the TLVs consists of one 362 or more nested Type/Length/Value triplets. New sub-TLVs specifically 363 for inter-AS TE Link advertisement are described in Section 3.2. 365 3.1.2. Inter-AS-TE-v3 LSA 367 In this document, a new LS type is defined for OSPFv3 inter-AS TE 368 link advertisement. The new LS type function code is 11 (which needs 369 to be confirmed by IANA see Section 6.1). 371 The format of an Inter-AS-TE-v3 LSA follows the standard definition 372 of an OSPFv3 LSA as defined in [OSPFV3]. 374 The high-order three bits of the LS type field of the OSPFv3 LSA 375 header encode generic properties of the LSA and are termed the U-bit, 376 S2-bit, and S1-bit [OSPFV3]. The remainder of the LS type carries 377 the LSA function code. 379 For the Inter-AS-TE-v3-LSA the bits are set as follows: 381 The U-bit is always set to 1 to indicate that an OSPFv3 router MUST 382 flood the LSA at its defined flooding scope even if it does not 383 recognize the LS type. 385 The S2 and S1 bits indicate the flooding scope of an LSA. For the 386 Inter-AS-TE-v3-LSA the S2 and S1 bits SHOULD be set to 01 to 387 indicate that the flooding scope is to be limited to within the 388 single IGP area to which the ASBR belongs, but MAY be set to 10 if 389 the information should reach all routers (including area border 390 routers, ASBRs, and PCEs) in the AS. The choice between the use of 391 01 or 10 is a network-wide policy choice, and configuration control 392 SHOULD be provided in ASBR implementations that support the 393 advertisement of inter-AS TE links. 395 The Link State ID of the Inter-AS-TE-v3 LSA is an arbitrary value 396 used to uniquely identify Traffic Engineering LSAs. The LSA ID has 397 no topological significance. 399 The TLVs with the body of an Inter-AS-TE-v3 LSA have the same format 400 and semantic as defined above in [OSPF-V3-TE]. New sub-TLVs 401 specifically for inter-AS TE Link advertisement are described in 402 Section 3.2. 404 3.2. LSA Payload 406 Both the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA contain one top 407 level TLV: 409 2 - Link TLV 411 For the Inter-AS-TE-v2 LSA this TLV is defined in [OSPF-TE] and for 412 the Inter-AS-TE-v3 LSA this TLV is defined in [OSPF-V3-TE]. The sub- 413 TLVs carried in this TLV are described in the following sections. 415 3.2.1. Link TLV 417 The Link TLV describes a single link and consists a set of sub-TLVs. 418 The sub-TLVs for inclusion in the Link TLV of the Inter-AS-TE-v2 LSA 419 and Inter-AS-TE-v3 LSA are defined respectively in [OSPF-TE] and 420 [OSPF-V3-TE] and the list of sub-TLVs may be extended by other 421 documents. However, this document defines one exception as follows. 423 The Link ID sub-TLV [OSPF-TE] MUST NOT be used in the Link TLV of an 424 Inter-AS-TE-v2 LSA, and the Neighbor ID sub-TLV [OSPF-V3-TE] MUST 425 NOT be used in the Link TLV of an Inter-AS-TE-v3 LSA. Given that 426 OSPF is an IGP and should only be utilized between routers in the 427 same routing domain, the OSPF specific Link ID and Neighbor ID sub- 428 TLVs are not applicable to inter-AS links. 430 Instead, the remote ASBR is identified by the inclusion of the 431 following new sub-TLVs defined in this document and described in the 432 subsequent sections. 434 21 - Remote AS Number sub-TLV 436 22 - IPv4 Remote ASBR ID sub-TLV 438 23 - IPv6 Remote ASBR ID sub-TLV 440 The Remote-AS-Number sub-TLV MUST be included in the Link TLV of 441 both the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA. At least one of 442 the IPv4-Remote-ASBR-ID sub-TLV and the IPv6-Remote-ASBR-ID sub-TLV 443 SHOULD be included in the Link TLV of the Inter-AS-TE-v2 LSA and 444 Inter-AS-TE-v3 LSA. Note that it is possible to include the IPv6- 445 Remote-ASBR-ID sub-TLV in the Link TLV of the Inter-AS-TE-v2 LSA, 446 and to include the IPv4-Remote-ASBR-ID sub-TLV in the Link TLV of 447 the Inter-AS-TE-v3 LSA because the sub-TLVs refer to ASBRs that are 448 in a different addressing scope (that is, a different AS) from that 449 where the OSPF LSA is used. 451 3.3. Sub-TLV Detail 453 3.3.1. Remote AS Number Sub-TLV 455 A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion 456 in the Link TLV when advertising inter-AS links. The Remote AS 457 Number sub-TLV specifies the AS number of the neighboring AS to 458 which the advertised link connects. The Remote AS number sub-TLV is 459 REQUIRED in a Link TLV that advertises an inter-AS TE link. 461 The Remote AS number sub-TLV is TLV type 21 (which needs to be 462 confirmed by IANA see Section 6.2), and is four octets in length. 463 The format is as follows: 465 0 1 2 3 466 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 1 467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 468 | Type | Length | 469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 | Remote AS Number | 471 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 473 The Remote AS number field has 4 octets. When only two octets are 474 used for the AS number, as in current deployments, the left (high- 475 order) two octets MUST be set to zero. 477 3.3.2. IPv4 Remote ASBR ID Sub-TLV 479 A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub- 480 TLV, can be included in the Link TLV when advertising inter-AS links. 481 The IPv4 Remote ASBR ID sub-TLV specifies the IPv4 identifier of the 482 remote ASBR to which the advertised inter-AS link connects. This 483 could be any stable and routable IPv4 address of the remote ASBR. 484 Use of the TE Router Address TE Router ID as specified in the 485 Router Address TLV [OSPF-TE] is RECOMMENDED. 487 The IPv4 Remote ASBR ID sub-TLV is TLV type 22 (which needs to be 488 confirmed by IANA see Section 6.2), and is four octets in length. 489 Its format is as follows: 491 0 1 2 3 492 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 | Type | Length | 495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 | Remote ASBR ID | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 499 In OSPFv2 advertisements, the IPv4 Remote ASBR ID sub-TLV MUST be 500 included if the neighboring ASBR has an IPv4 address. If the 501 neighboring ASBR does not have an IPv4 address (not even an IPv4 TE 502 Router ID), the IPv6 Remote ASBR ID sub-TLV MUST be included instead. 503 An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub-TLV MAY 504 both be present in a Link TLV in OSPFv2 or OSPFv3. 506 3.3.3. IPv6 Remote ASBR ID Sub-TLV 508 A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub- 509 TLV, can be included in the Link TLV when advertising inter-AS links. 510 The IPv6 Remote ASBR ID sub-TLV specifies the identifier of the 511 remote ASBR to which the advertised inter-AS link connects. This 512 could be any stable, routable and global IPv6 address of the remote 513 ASBR. Use of the TE Router IPv6 Address IPv6 TE Router ID as 514 specified in the IPv6 Router Address as specified in the IPv6 Router 515 Address TLV [OSPF-V3-TE] is RECOMMENDED. 517 The IPv6 Remote ASBR ID sub-TLV is TLV type 23 (which needs to be 518 confirmed by IANA see Section 6.2), and is sixteen octets in length. 519 Its format is as follows: 521 0 1 2 3 522 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 1 523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 524 | Type | Length | 525 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 | Remote ASBR ID | 527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 | Remote ASBR ID (continued) | 529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 530 | Remote ASBR ID (continued) | 531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 532 | Remote ASBR ID (continued) | 533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 In OSPFv3 advertisements, the IPv6 Remote ASBR ID sub-TLV MUST be 536 included if the neighboring ASBR has an IPv6 address. If the 537 neighboring ASBR does not have an IPv6 address, the IPv4 Remote ASBR 538 ID sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV 539 and IPv6 Remote ASBR ID sub-TLV MAY both be present in a Link TLV in 540 OSPFv2 or OSPFv3. 542 4. Procedure for Inter-AS TE Links 544 When TE is enabled on an inter-AS link and the link is up, the ASBR 545 SHOULD advertise this link using the normal procedures for OSPF-TE 546 [OSPF-TE]. When either the link is down or TE is disabled on the 547 link, the ASBR SHOULD withdraw the advertisement. When there are 548 changes to the TE parameters for the link (for example, when the 549 available bandwidth changes) the ASBR SHOULD re-advertise the link, 550 but the ASBR MUST take precautions against excessive re- 551 advertisements as described in [OSPF-TE]. 553 Hellos MUST NOT be exchanged over the inter-AS link, and 554 consequently, an OSPF adjacency MUST NOT be formed. 556 The information advertised comes from the ASBR's knowledge of the TE 557 capabilities of the link, the ASBR's knowledge of the current status 558 and usage of the link, and configuration at the ASBR of the remote 559 AS number and remote ASBR TE Router ID. 561 Legacy routers receiving an advertisement for an inter-AS TE link 562 are able to ignore it because the Link Type carries an unknown value. 563 They will continue to flood the LSA, but will not attempt to use the 564 information received as if the link were an intra-AS TE link. 566 In the current operation of TE OSPF, the LSRs at each end of a TE 567 link emit LSAs describing the link. The databases in the LSRs then 568 have two entries (one locally generated, the other from the peer) 569 that describe the different 'directions' of the link. This enables 570 CSPF to do a two-way check on the link when performing path 571 computation and eliminate it from consideration unless both 572 directions of the link satisfy the required constraints. 574 In the case we are considering here (i.e., of a TE link to another 575 AS) there is, by definition, no IGP peering and hence no bi- 576 directional TE link information. In order for the CSPF route 577 computation entity to include the link as a candidate path, we have 578 to find a way to get LSAs describing its (bidirectional) TE 579 properties into the TE database. 581 This is achieved by the ASBR advertising, internally to its AS, 582 information about both directions of the TE link to the next AS. The 583 ASBR will normally generate an LSA describing its own side of a link; 584 here we have it 'proxy' for the ASBR at the edge of the other AS and 585 generate an additional LSA that describes that device's 'view' of 586 the link. 588 Only some essential TE information for the link needs to be 589 advertised; i.e., the Link Type, the Remote AS number and the Remote 590 ASBR ID. Routers or PCEs that are capable of processing 591 advertisements of inter-AS TE links SHOULD NOT use such links to 592 compute paths that exit an AS to a remote ASBR and then immediately 593 re-enter the AS through another TE link. Such paths would constitute 594 extremely rare occurrences and SHOULD NOT be allowed except as the 595 result of specific policy configurations at the router or PCE 596 computing the path. 598 4.1. Origin of Proxied TE Information 600 Section 4 describes how to an ASBR advertises TE link information as 601 a proxy for its neighbor ASBR, but does not describe where this 602 information comes from. 604 Although the source of this information is outside the scope of this 605 document, it is possible that it will be a configuration requirement 606 at the ASBR, as are other, local, properties of the TE link. Further, 607 where BGP is used to exchange IP routing information between the 608 ASBRs, a certain amount of additional local configuration about the 609 link and the remote ASBR is likely to be available. 611 We note further that it is possible, and may be operationally 612 advantageous, to obtain some of the required configuration 613 information from BGP. Whether and how to utilize these possibilities 614 is an implementation matter. 616 5. Security Considerations 618 The protocol extensions defined in this document are relatively 619 minor and can be secured within the AS in which they are used by the 620 existing OSPF security mechanisms. 622 There is no exchange of information between ASes, and no change to 623 the OSPF security relationship between the ASes. In particular, 624 since no OSPF adjacency is formed on the inter-AS links, there is no 625 requirement for OSPF security between the ASes. 627 Some of the information included in these new advertisements (e.g., 628 the remote AS number and the remote ASBR ID) is obtained manually 629 from a neighboring administration as part of commercial relationship. 630 The source and content of this information should be carefully 631 checked before it is entered as configuration information at the 632 ASBR responsible for advertising the inter-AS TE links. 634 It is worth noting that in the scenario we are considering a Border 635 Gateway Protocol (BGP) peering may exist between the two ASBRs and 636 this could be used to detect inconsistencies in configuration (e.g., 637 the administration that originally supplied the information may be 638 lying, or some manual mis-configurations or mistakes are made by the 639 operators). For example, if a different remote AS number is received 640 in a BGP OPEN [BGP] from that locally configured into OSPF-TE, as we 641 describe here, then local policy SHOULD be applied to determine 642 whether to alert the operator to a potential mis-configuration or to 643 suppress the OSPF advertisement of the inter-AS TE link. Note, 644 further, that if BGP is used to exchange TE information as described 645 in Section 4.1, the inter-AS BGP session SHOULD be secured using 646 mechanisms as described in [BGP] to provide authentication and 647 integrity checks. 649 6. IANA Considerations 651 IANA is requested to make the following allocations from registries 652 under its control. 654 6.1. Inter-AS TE OSPF LSA 656 6.1.1. Inter-AS-TE-v2 LSA 658 IANA is requested to assign a new Opaque LSA type (TBD) to Inter-AS- 659 TE-v2 LSA. We suggest that the value 6 be assigned for the new 660 Opaque LSA type. 662 6.1.2. Inter-AS-TE-v3 LSA 664 IANA is requested to assign a new OSPFv3 LSA type function code (TBD) 665 to Inter-AS-TE-v3 LSA. We suggest that the value 11 be assigned for 666 the new OSPV3 LSA type function code. 668 6.2. OSPF LSA Sub-TLVs type 670 IANA maintains the "Open Shortest Path First (OSPF) Traffic 671 Engineering TLVs" registry with sub-registry "Types for sub-TLVs in 672 a TE Link TLV". IANA is requested to assign three new sub-TLVs as 673 follows. The following numbers are suggested (see section 3.3): 675 Value Meaning 677 21 Remote AS Number sub-TLV 679 22 IPv4 Remote ASBR ID sub-TLV 681 23 IPv6 Remote ASBR ID sub-TLV 683 7. Acknowledgments 685 The authors would like to thank Adrian Farrel, Acee Lindem, JP 686 Vasseur, Dean Cheng, and Jean-Louis Le Roux for their review and 687 comments to this document. 689 8. References 691 8.1. Normative References 693 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 694 Requirement Levels", BCP 14, RFC 2119, March 1997. 696 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 697 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 698 Tunnels", RFC 3209, December 2001. 700 [RFC5250] Berger, L., Bryskin, I., Zinin, A., and Coltun, R.,"The 701 OSPF Opaque LSA Option", RFC5250, July 2008. 703 [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 705 [OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic 706 Engineering (TE) Extensions to OSPF Version 2", RFC 3630, 707 September 2003. 709 [OSPF-V3-TE] Ishiguro K., Manral V., Davey A., and Lindem A., 710 "Traffic Engineering Extensions to OSPF version 3", draft- 711 ietf-ospf-ospfv3-traffic, {work in progress}. 713 [GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in 714 Support of Generalized Multi-Protocol Label Switching 715 (GMPLS)", RFC 4203, October 2005. 717 [OSPFV3] Coltun, R., Ferguson, D., Moy, J., and Lindem, A., "OSPF 718 for IPv6", RFC 5340, July 2008. 720 8.2. Informative References 722 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 723 Engineering Requirements", RFC4216, November 2005. 725 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 726 path computation method for establishing Inter-domain", 727 RFC 5152, February 2008. 729 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A 730 Backward Recursive PCE-based Computation (BRPC) procedure 731 to compute shortest inter-domain Traffic Engineering Label 732 Switched Paths", draft-ietf-pce-brpc, (work in progress) 734 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 735 Element (PCE)-Based Architecture", RFC4655, August 2006. 737 [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- 738 Discovery", RFC 5252, July 2008. 740 [BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", 741 RFC4271, January 2006 743 Authors' Addresses 745 Mach(Guoyi) Chen 746 Huawei Technologies Co.,Ltd 747 KuiKe Building, No.9 Xinxi Rd., 748 Hai-Dian District 749 Beijing, 100085 750 P.R. China 752 Email: mach@huawei.com 754 Renhai Zhang 755 Huawei Technologies Co.,Ltd 756 KuiKe Building, No.9 Xinxi Rd., 757 Hai-Dian District 758 Beijing, 100085 759 P.R. China 761 Email: zhangrenhai@huawei.com 763 Xiaodong Duan 764 China Mobile 765 53A,Xibianmennei Ave,Xunwu District 766 Beijing, China 768 Email: duanxiaodong@chinamobile.com 770 Intellectual Property Statement 772 The IETF takes no position regarding the validity or scope of any 773 Intellectual Property Rights or other rights that might be claimed 774 to pertain to the implementation or use of the technology described 775 in this document or the extent to which any license under such 776 rights might or might not be available; nor does it represent that 777 it has made any independent effort to identify any such rights. 778 Information on the procedures with respect to rights in RFC 779 documents can be found in BCP 78 and BCP 79. 781 Copies of IPR disclosures made to the IETF Secretariat and any 782 assurances of licenses to be made available, or the result of an 783 attempt made to obtain a general license or permission for the use 784 of such proprietary rights by implementers or users of this 785 specification can be obtained from the IETF on-line IPR repository 786 at http://www.ietf.org/ipr. 788 The IETF invites any interested party to bring to its attention any 789 copyrights, patents or patent applications, or other proprietary 790 rights that may cover technology that may be required to implement 791 this standard. 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