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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (April 10, 2008) is 5860 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2370 (Obsoleted by RFC 5250) ** Obsolete normative reference: RFC 2740 (ref. 'OSPFV3') (Obsoleted by RFC 5340) Summary: 4 errors (**), 0 flaws (~~), 1 warning (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network working group M. Chen 2 Internet Draft Renhai Zhang 3 Expires: October 2008 Huawei Technologies Co.,Ltd 4 Category: Standards Track Xiaodong Duan 5 China Mobile 6 April 10, 2008 8 OSPF Extensions in Support of Inter-AS Multiprotocol Label Switching 9 (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering 10 draft-ietf-ccamp-ospf-interas-te-extension-03.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 other 22 groups may also distribute working documents as Internet-Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html 35 This Internet-Draft will expire on October 10, 2008. 37 Abstract 39 This document describes extensions to the OSPF version 2 and 3 40 protocols to support Multiprotocol Label Switching (MPLS) and 41 Generalized MPLS (GMPLS) Traffic Engineering (TE) for multiple 42 Autonomous Systems (ASes). OSPF-TE v2 and v3 extensions are defined 43 for the flooding of TE information about inter-AS links which can be 44 used to perform inter-AS TE path computation. 46 No support for flooding TE information from outside the AS is 47 proposed or defined in this document. 49 Conventions used in this document 51 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 52 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 53 document are to be interpreted as described in RFC-2119 [RFC2119]. 55 Table of Contents 57 1. Introduction.................................................3 58 2. Problem Statement............................................3 59 2.1. A Note on Non-Objectives................................4 60 2.2. Per-Domain Path Determination...........................4 61 2.3. Backward Recursive Path Computation.....................6 62 3. Extensions to OSPF...........................................7 63 3.1. LSA Definitions.........................................8 64 3.1.1. Inter-AS-TE-v2 LSA.................................8 65 3.1.2. Inter-AS-TE-v3 LSA.................................8 66 3.2. LSA Payload.............................................9 67 3.2.1. Link TLV...........................................9 68 3.3. Sub-TLV Detail.........................................10 69 3.3.1. Remote AS Number Sub-TLV..........................10 70 3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................11 71 3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................11 72 4. Procedure for Inter-AS TE Links.............................12 73 4.1. Origin of Proxied TE Information.......................13 74 5. Security Considerations.....................................14 75 6. IANA Considerations.........................................14 76 6.1. Inter-AS TE OSPF LSA...................................15 77 6.1.1. Inter-AS-TE-v2 LSA................................15 78 6.1.2. Inter-AS-TE-v3 LSA................................15 79 6.2. OSPF LSA Sub-TLVs type.................................15 80 7. Acknowledgments.............................................15 81 8. References..................................................15 82 8.1. Normative References...................................15 83 8.2. Informative References.................................16 84 Authors' Addresses.............................................17 85 Intellectual Property Statement................................17 86 Disclaimer of Validity.........................................18 87 Copyright Statement............................................18 89 1. Introduction 91 [OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support 92 intra-area Traffic Engineering (TE). The extensions provide a way of 93 encoding the TE information for TE-enabled links within the network 94 (TE links) and flooding this information within an area. Type 10 95 opaque LSAs [RFC2370] are used to carry such TE information. Two top- 96 level TLVs are defined in [OSPF-TE]: Router Address TLV and Link TLV. 97 The Link TLV has several nested sub-TLVs which describe the TE 98 attributes for a TE link. 100 [OSPF-V3-TE] defines similar extensions to OSPFv3 [OSPFV3]. It 101 defines a new LSA, which is referred to as the Intra-Area-TE LSA, to 102 advertise TE information. [OSPF-V3-TE] uses "Traffic Engineering 103 Extensions to OSPF" [OSPF-TE] as a base for TLV definitions and 104 defines some new TLVs and sub-TLVs to extend TE capabilities to IPv6 105 networks. 107 Requirements for establishing Multiprotocol Label Switching Traffic 108 Engineering (MPLS-TE) Label Switched Paths (LSPs) that cross multiple 109 Autonomous Systems (ASes) are described in [INTER-AS-TE-REQ]. As 110 described in [INTER-AS-TE-REQ], a method SHOULD provide the ability 111 to compute a path spanning multiple ASes. So a path computation 112 entity that may be the head-end Label Switching Router (LSR), an AS 113 Border Router (ASBR), or a Path Computation Element (PCE [PCE]) needs 114 to know the TE information not only of the links within an AS, but 115 also of the links that connect to other ASes. 117 In this document, two new separate Link State Advertisements (LSAs) 118 are defined to advertise inter-AS TE information for OSPFv2 and 119 OSPFv3 respectively, and three new sub-TLVs are added to the existing 120 Link TLV to extend TE capabilities for inter-AS Traffic Engineering. 121 The detailed definitions and procedures are discussed in the 122 following sections. 124 This document does not propose or define any mechanisms to advertise 125 any other extra-AS TE information within OSPF. See Section 2.1 for a 126 full list of non-objectives for this work. 128 2. Problem Statement 130 As described in [INTER-AS-TE-REQ], in the case of establishing an 131 inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] 132 may include the following elements in the Explicit Route Object (ERO) 133 in order to describe the path of the LSP: 135 - a set of AS numbers as loose hops; and/or 136 - a set of LSRs including ASBRs as loose hops. 138 Two methods for determining inter-AS paths are currently being 139 discussed. The per-domain method [PD-PATH] determines the path one 140 domain at a time. The backward recursive method [BRPC] uses 141 cooperation between PCEs to determine an optimum inter-domain path. 142 The sections that follow examine how inter-AS TE link information 143 could be useful in both cases. 145 2.1. A Note on Non-Objectives 147 It is important to note that this document does not make any change 148 to the confidentiality and scaling assumptions surrounding the use of 149 ASes in the Internet. In particular, this document is conformant to 150 the requirements set out in [INTER-AS-TE-REQ]. 152 The following features are explicitly excluded: 154 o There is no attempt to distribute TE information from within one 155 AS to another AS. 157 o There is no mechanism proposed to distribute any form of TE 158 reachability information for destinations outside the AS. 160 o There is no proposed change to the PCE architecture or usage. 162 o TE aggregation is not supported or recommended. 164 o There is no exchange of private information between ASes. 166 o No OSPF adjacencies are formed on the inter-AS link. 168 Note also that the extensions proposed in this document are used only 169 to advertise information about inter-AS TE links. As such these 170 extensions address an entirely different problem from L1VPN Auto- 171 Discovery [L1VPN-OSPF-AD] which defines how TE information about 172 links between Customer Edge (CE) equipment and Provider Edge (PE) 173 equipment can be advertised in OSPF-TE alongside the auto-discovery 174 information for the CE-PE links. There is no overlap between this 175 document and [L1VPN-OSPF-AD]. 177 2.2. Per-Domain Path Determination 179 In the per-domain method of determining an inter-AS path for an MPLS- 180 TE LSP, when an LSR that is an entry-point to an AS receives a Path 181 message from an upstream AS with an ERO containing a next hop that is 182 an AS number, it needs to find which LSRs (ASBRs) within the local AS 183 are connected to the downstream AS so that it can compute a TE LSP 184 segment across the local AS to one of those LSRs and forward the PATH 185 message to it and hence into the next AS. See Figure 1 for an example: 187 R1------R3----R5-----R7------R9-----R11 188 | | \ | / | 189 | | \ | ---- | 190 | | \ | / | 191 R2------R4----R6 --R8------R10----R12 192 : : 193 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 195 Figure 1: Inter-AS Reference Model 197 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 198 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 199 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 201 If an inter-AS TE LSP is planned to be established from R1 to R12, 202 the AS sequence will be: AS1, AS2, AS3. 204 Suppose that the Path message enters AS2 from R3. The next hop in the 205 ERO shows AS3, and R5 must determine a path segment across AS2 to 206 reach AS3. It has a choice of three exit points from AS2 (R6, R7, and 207 R8) and it needs to know which of these provide TE connectivity to 208 AS3, and whether the TE connectivity (for example, available 209 bandwidth) is adequate for the requested LSP. 211 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 212 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 213 connects to R9. Since there may be multiple ASBRs that are connected 214 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 215 properties of the inter-AS TE links so that it can select the correct 216 exit ASBR. 218 Once the path message reaches the exit ASBR, any choice of inter-AS 219 TE link can be made by the ASBR if not already made by entry ASBR 220 that computed the segment. 222 More details can be found in the Section 4. of [PD-PATH], which 223 clearly points out why advertising of inter-AS links is desired. 225 To enable R5 to make the correct choice of exit ASBR the following 226 information is needed: 228 o List of all inter-AS TE links for the local AS. 230 o TE properties of each inter-AS TE link. 232 o AS number of the neighboring AS connected to by each inter-AS TE 233 link. 235 o Identity (TE Router ID) of the neighboring ASBR connected to by 236 each inter-AS TE link. 238 In GMPLS networks further information may also be required to select 239 the correct TE links as defined in [GMPLS-TE]. 241 The example above shows how this information is needed at the entry 242 point ASBRs for each AS (or the PCEs that provide computation 243 services for the ASBRs), but this information is also needed 244 throughout the local AS if path computation function is fully 245 distributed among LSRs in the local AS, for example to support LSPs 246 that have start points (ingress nodes) within the AS. 248 2.3. Backward Recursive Path Computation 250 Another scenario using PCE techniques has the same problem. [BRPC] 251 defines a PCE-based TE LSP computation method (called Backward 252 Recursive Path Computation) to compute optimal inter-domain 253 constrained MPLS-TE or GMPLS LSPs. In this path computation method, a 254 specific set of traversed domains (ASes) are assumed to be selected 255 before computation starts. Each downstream PCE in domain(i) returns 256 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 257 tree of potential paths. Each tree consists of the set of paths from 258 all Boundary Nodes located in domain(i) to the destination where each 259 path satisfies the set of required constraints for the TE LSP 260 (bandwidth, affinities, etc.). 262 So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide 263 connectivity from the upstream AS. In order that the tree of paths 264 provided by one PCE to its neighbor can be correlated, the identities 265 of the ASBRs for each path need to be referenced, so the PCE must 266 know the identities of the ASBRs in the remote AS reached by any 267 inter-AS TE link, and, in order that it provides only suitable paths 268 in the tree, the PCE must know the TE properties of the inter-AS TE 269 links. See the following figure as an example: 271 PCE1<------>PCE2<-------->PCE3 272 / : : 273 / : : 274 R1------R3----R5-----R7------R9-----R11 275 | | \ | / | 276 | | \ | ---- | 277 | | \ | / | 278 R2------R4----R6 --R8------R10----R12 279 : : 280 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 282 Figure 2: BRPC for Inter-AS Reference Model 284 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 285 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 286 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 287 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path 288 computation and are responsible for path segment computation within 289 their own domain(s). 291 If an inter-AS TE LSP is planned to be established from R1 to R12, 292 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 293 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 294 request originated from the PCC (R1) is relayed by PCE1 and PCE2 295 along the PCE chain to PCE3, then PCE3 begins to compute the path 296 segments from the entry boundary nodes that provide connection from 297 AS2 to the destination (R12). But, to provide suitable path segments, 298 PCE3 must determine which entry boundary nodes provide connectivity 299 to its upstream neighbor AS (identified by its AS number), and must 300 know the TE properties of the inter-AS TE links. In the same way, 301 PCE2 also needs to determine the entry boundary nodes according to 302 its upstream neighbor AS and the inter-AS TE link capabilities. 304 Thus, to support Backward Recursive Path Computation the same 305 information listed in Section 2.2 is required. The AS number of the 306 neighboring AS connected to by each inter-AS TE link is particularly 307 important. 309 3. Extensions to OSPF 311 Note that this document does not define mechanisms for distribution 312 of TE information from one AS to another, does not distribute any 313 form of TE reachability information for destinations outside the AS, 314 does not change the PCE architecture or usage, does not suggest or 315 recommend any form of TE aggregation, and does not feed private 316 information between ASes. See section 2.1. 318 The extensions defined in this document allow an inter-AS TE link 319 advertisement to be easily identified as such by the use of two new 320 types of LSA, which are referred to as Inter-AS-TE-v2 LSA and Inter- 321 AS-TE-v3 LSA. Three new sub-TLVs are added to the Link TLV to carry 322 the information about the neighboring AS and the remote ASBR. 324 3.1. LSA Definitions 326 3.1.1. Inter-AS-TE-v2 LSA 328 For the advertisement of OSPFv2 inter-AS TE links, a new Opaque LSA, 329 the Inter-AS-TE-v2 LSA, is defined in this document. The Inter-AS-TE- 330 v2 LSA has the same format as "Traffic Engineering LSA" which is 331 defined in [OSPF-TE]. 333 The inter-AS TE link advertisement SHOULD be carried in a Type 10 334 Opaque LSA if the flooding scope is to be limited to within the 335 single IGP area to which the ASBR belongs, or MAY be carried in a 336 Type 11 Opaque LSA if the information is intended to reach all 337 routers (including area border routers, ASBRs, and PCEs) in the AS. 338 The choice between the use of a Type 10 or Type 11 Opaque LSA is a 339 AS-wide policy choice, and configuration control of it SHOULD be 340 provided in ASBR implementations that support the advertisement of 341 inter-AS TE links. 343 The Link State ID of an Opaque LSA as defined in [RFC2370] is divided 344 into two parts. One of them is the Opaque type (8-bit), the other is 345 the Opaque ID (24-bit). The suggested value for the Opaque type of 346 Inter-AS-TE-v2 LSA is TBD and will be assigned by IANA (see Section 347 6.1). We suggest the value 6. The Opaque ID (in this document called 348 the Instance) of the Inter-AS-TE-v2 LSA is an arbitrary value used to 349 uniquely identify Traffic Engineering LSAs. The Link State ID has no 350 topological significance. 352 The TLVs within the body of an Inter-AS-TE-v2 LSA have the same 353 format as used in OSPF-TE. The payload of the TLVs consists of one or 354 more nested Type/Length/Value triplets. New sub-TLVs specifically for 355 inter-AS TE Link advertisement are described in Section 3.2. 357 3.1.2. Inter-AS-TE-v3 LSA 359 In this document, a new LS type is defined for OSPFv3 inter-AS TE 360 link advertisement. The new LS type function code is 11 (which needs 361 to be confirmed by IANA see Section 6.1). 363 The format of an Inter-AS-TE-v3 LSA follows the standard definition 364 of an OSPFv3 LSA as defined in [OSPFV3]. 366 The high-order three bits of the LS type field of the OSPFv3 LSA 367 header encode generic properties of the LSA and are termed the U-bit, 368 S2-bit, and S1-bit [OSPFV3]. The remainder of the LS type carries the 369 LSA function code. 371 For the Inter-AS-TE-v3-LSA the bits are set as follows: 373 The U-bit is always set to 1 to indicate that an OSPFv3 router MUST 374 flood the LSA at its defined flooding scope even if it does not 375 recognize the LS type. 377 The S2 and S1 bits indicate the flooding scope of an LSA. For the 378 Inter-AS-TE-v3-LSA the S2 and S1 bits SHOULD be set to 01 to indicate 379 that the flooding scope is to be limited to within the single IGP 380 area to which the ASBR belongs, but MAY be set to 10 if the 381 information should reach all routers (including area border routers, 382 ASBRs, and PCEs) in the AS. The choice between the use of 01 or 10 is 383 a network-wide policy choice, and configuration control SHOULD be 384 provided in ASBR implementations that support the advertisement of 385 inter-AS TE links. 387 The Link State ID of the Inter-AS-TE-v3 LSA is an arbitrary value 388 used to uniquely identify Traffic Engineering LSAs. The LSA ID has no 389 topological significance. 391 The TLVs with the body of an Inter-AS-TE-v3 LSA have the same format 392 and semantic as defined above in [OSPF-V3-TE]. New sub-TLVs 393 specifically for inter-AS TE Link advertisement are described in 394 Section 3.2. 396 3.2. LSA Payload 398 Both the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA contain one top 399 level TLV: 401 2 - Link TLV 403 For the Inter-AS-TE-v2 LSA this TLV is defined in [OSPF-TE] and for 404 the Inter-AS-TE-v3 LSA this TLV is defined in [OSPF-V3-TE]. The sub- 405 TLVs carried in this TLV are described in the following sections. 407 3.2.1. Link TLV 409 The Link TLV describes a single link and consists a set of sub-TLVs. 410 The sub-TLVs for inclusion in the Link TLV of the Inter-AS-TE-v2 LSA 411 and Inter-AS-TE-v3 LSA are defined respectively in [OSPF-TE] and 413 [OSPF-V3-TE] and the list of sub-TLVs may be extended by other 414 documents. However, this document defines one exception as follows. 416 The Link ID sub-TLV [OSPF-TE] MUST NOT be used in the Link TLV of an 417 Inter-AS-TE-v2 LSA, and the Neighbor ID sub-TLV [OSPF-V3-TE] MUST NOT 418 be used in the Link TLV of an Inter-AS-TE-v3 LSA. Given that OSPF is 419 an IGP and should only be utilized between routers in the same 420 routing domain, the OSPF specific Link ID and Neighbor ID sub-TLVs 421 are not applicable to inter-AS links. 423 Instead, the remote ASBR is identified by the inclusion of the 424 following new sub-TLVs defined in this document and described in the 425 subsequent sections. 427 21 - Remote AS Number sub-TLV 429 22 - IPv4 Remote ASBR ID sub-TLV 431 23 - IPv6 Remote ASBR ID sub-TLV 433 The Remote-AS-Number sub-TLV MUST be included in the Link TLV of both 434 the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA. At least one of the 435 IPv4-Remote-ASBR-ID sub-TLV and the IPv6-Remote-ASBR-ID sub-TLV 436 SHOULD be included in the Link TLV of the Inter-AS-TE-v2 LSA and 437 Inter-AS-TE-v3 LSA. Note that it is possible to include the IPv6- 438 Remote-ASBR-ID sub-TLV in the Link TLV of the Inter-AS-TE-v2 LSA, and 439 to include the IPv4-Remote-ASBR-ID sub-TLV in the Link TLV of the 440 Inter-AS-TE-v3 LSA because the sub-TLVs refer to ASBRs that are in a 441 different addressing scope (that is, a different AS) from that where 442 the OSPF LSA is used. 444 3.3. Sub-TLV Detail 446 3.3.1. Remote AS Number Sub-TLV 448 A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion 449 in the Link TLV when advertising inter-AS links. The Remote AS Number 450 sub-TLV specifies the AS number of the neighboring AS to which the 451 advertised link connects. The Remote AS number sub-TLV is REQUIRED in 452 a Link TLV that advertises an inter-AS TE link. 454 The Remote AS number sub-TLV is TLV type 21 (which needs to be 455 confirmed by IANA see Section 6.2), and is four octets in length. The 456 format is as follows: 458 0 1 2 3 459 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 1 460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 461 | Type | Length | 462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 463 | Remote AS Number | 464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 The Remote AS number field has 4 octets. When only two octets are 467 used for the AS number, as in current deployments, the left (high- 468 order) two octets MUST be set to zero. 470 3.3.2. IPv4 Remote ASBR ID Sub-TLV 472 A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub- 473 TLV, can be included in the Link TLV when advertising inter-AS links. 474 The IPv4 Remote ASBR ID sub-TLV specifies the IPv4 identifier of the 475 remote ASBR to which the advertised inter-AS link connects. This 476 could be any stable and routable IPv4 address of the remote ASBR. Use 477 of the TE Router Address TE Router ID as specified in the Router 478 Address TLV [OSPF-TE] is RECOMMENDED. 480 The IPv4 Remote ASBR ID sub-TLV is TLV type 22 (which needs to be 481 confirmed by IANA see Section 6.2), and is four octets in length. Its 482 format is as follows: 484 0 1 2 3 485 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 1 486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 487 | Type | Length | 488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 | Remote ASBR ID | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 492 In OSPFv2 advertisements, the IPv4 Remote ASBR ID sub-TLV MUST be 493 included if the neighboring ASBR has an IPv4 address. If the 494 neighboring ASBR does not have an IPv4 address (not even an IPv4 TE 495 Router ID), the IPv6 Remote ASBR ID sub-TLV MUST be included instead. 496 An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub-TLV MAY 497 both be present in a Link TLV in OSPFv2 or OSPFv3. 499 3.3.3. IPv6 Remote ASBR ID Sub-TLV 501 A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub- 502 TLV, can be included in the Link TLV when advertising inter-AS links. 503 The IPv6 Remote ASBR ID sub-TLV specifies the identifier of the 504 remote ASBR to which the advertised inter-AS link connects. This 505 could be any stable, routable and global IPv6 address of the remote 506 ASBR. Use of the TE Router IPv6 Address IPv6 TE Router ID as 507 specified in the IPv6 Router Address as specified in the IPv6 Router 508 Address TLV [OSPF-V3-TE] is RECOMMENDED. 510 The IPv6 Remote ASBR ID sub-TLV is TLV type 23 (which needs to be 511 confirmed by IANA see Section 6.2), and is sixteen octets in length. 512 Its format is as follows: 514 0 1 2 3 515 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 1 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | Type | Length | 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | Remote ASBR ID | 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 | Remote ASBR ID (continued) | 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 523 | Remote ASBR ID (continued) | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | Remote ASBR ID (continued) | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 In OSPFv3 advertisements, the IPv6 Remote ASBR ID sub-TLV MUST be 529 included if the neighboring ASBR has an IPv6 address. If the 530 neighboring ASBR does not have an IPv6 address, the IPv4 Remote ASBR 531 ID sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV 532 and IPv6 Remote ASBR ID sub-TLV MAY both be present in a Link TLV in 533 OSPFv2 or OSPFv3. 535 4. Procedure for Inter-AS TE Links 537 When TE is enabled on an inter-AS link and the link is up, the ASBR 538 SHOULD advertise this link using the normal procedures for OSPF-TE 539 [OSPF-TE]. When either the link is down or TE is disabled on the link, 540 the ASBR SHOULD withdraw the advertisement. When there are changes to 541 the TE parameters for the link (for example, when the available 542 bandwidth changes) the ASBR SHOULD re-advertise the link, but the 543 ASBR MUST take precautions against excessive re-advertisements as 544 described in [OSPF-TE]. 546 Hellos MUST NOT be exchanged over the inter-AS link, and consequently, 547 an OSPF adjacency MUST NOT be formed. 549 The information advertised comes from the ASBR's knowledge of the TE 550 capabilities of the link, the ASBR's knowledge of the current status 551 and usage of the link, and configuration at the ASBR of the remote AS 552 number and remote ASBR TE Router ID. 554 Legacy routers receiving an advertisement for an inter-AS TE link are 555 able to ignore it because the Link Type carries an unknown value. 556 They will continue to flood the LSA, but will not attempt to use the 557 information received as if the link were an intra-AS TE link. 559 In the current operation of TE OSPF, the LSRs at each end of a TE 560 link emit LSAs describing the link. The databases in the LSRs then 561 have two entries (one locally generated, the other from the peer) 562 that describe the different 'directions' of the link. This enables 563 CSPF to do a two-way check on the link when performing path 564 computation and eliminate it from consideration unless both 565 directions of the link satisfy the required constraints. 567 In the case we are considering here (i.e., of a TE link to another AS) 568 there is, by definition, no IGP peering and hence no bi-directional 569 TE link information. In order for the CSPF route computation entity 570 to include the link as a candidate path, we have to find a way to get 571 LSAs describing its (bidirectional) TE properties into the TE 572 database. 574 This is achieved by the ASBR advertising, internally to its AS, 575 information about both directions of the TE link to the next AS. The 576 ASBR will normally generate an LSA describing its own side of a link; 577 here we have it 'proxy' for the ASBR at the edge of the other AS and 578 generate an additional LSA that describes that device's 'view' of the 579 link. 581 Only some essential TE information for the link needs to be 582 advertised; i.e., the Link Type, the Remote AS number and the Remote 583 ASBR ID. Routers or PCEs that are capable of processing 584 advertisements of inter-AS TE links SHOULD NOT use such links to 585 compute paths that exit an AS to a remote ASBR and then immediately 586 re-enter the AS through another TE link. Such paths would constitute 587 extremely rare occurrences and SHOULD NOT be allowed except as the 588 result of specific policy configurations at the router or PCE 589 computing the path. 591 4.1. Origin of Proxied TE Information 593 Section 4 describes how to an ASBR advertises TE link information as 594 a proxy for its neighbor ASBR, but does not describe where this 595 information comes from. 597 Although the source of this information is outside the scope of this 598 document, it is possible that it will be a configuration requirement 599 at the ASBR, as are other, local, properties of the TE link. Further, 600 where BGP is used to exchange IP routing information between the 601 ASBRs, a certain amount of additional local configuration about the 602 link and the remote ASBR is likely to be available. 604 We note further that it is possible, and may be operationally 605 advantageous, to obtain some of the required configuration 606 information from BGP. Whether and how to utilize these possibilities 607 is an implementation matter. 609 5. Security Considerations 611 The protocol extensions defined in this document are relatively minor 612 and can be secured within the AS in which they are used by the 613 existing OSPF security mechanisms. 615 There is no exchange of information between ASes, and no change to 616 the OSPF security relationship between the ASes. In particular, since 617 no OSPF adjacency is formed on the inter-AS links, there is no 618 requirement for OSPF security between the ASes. 620 Some of the information included in these new advertisements (e.g., 621 the remote AS number and the remote ASBR ID) is obtained manually 622 from a neighboring administration as part of commercial relationship. 623 The source and content of this information should be carefully 624 checked before it is entered as configuration information at the ASBR 625 responsible for advertising the inter-AS TE links. 627 It is worth noting that in the scenario we are considering a Border 628 Gateway Protocol (BGP) peering may exist between the two ASBRs and 629 this could be used to detect inconsistencies in configuration. For 630 example, if a different remote AS number is received in a BGP OPEN 631 [BGP] from that locally configured into OSPF-TE, as we describe here, 632 then something is amiss. Note, further, that if BGP is used to 633 exchange TE information as described in Section 4.1, the inter-AS BGP 634 session will need to be fully secured. 636 6. IANA Considerations 638 IANA is requested to make the following allocations from registries 639 under its control. 641 6.1. Inter-AS TE OSPF LSA 643 6.1.1. Inter-AS-TE-v2 LSA 645 IANA is requested to assign a new Opaque LSA type (TBD) to Inter-AS- 646 TE-v2 LSA. We suggest that the value 6 be assigned for the new Opaque 647 LSA type. 649 6.1.2. Inter-AS-TE-v3 LSA 651 IANA is requested to assign a new OSPFv3 LSA type function code (TBD) 652 to Inter-AS-TE-v3 LSA. We suggest that the value 11 be assigned for 653 the new OSPV3 LSA type function code. 655 6.2. OSPF LSA Sub-TLVs type 657 IANA maintains the "Open Shortest Path First (OSPF) Traffic 658 Engineering TLVs" registry with sub-registry "Types for sub-TLVs in a 659 TE Link TLV". IANA is requested to assign three new sub-TLVs as 660 follows. The following numbers are suggested (see section 3.3): 662 Value Meaning 664 21 Remote AS Number sub-TLV 666 22 IPv4 Remote ASBR ID sub-TLV 668 23 IPv6 Remote ASBR ID sub-TLV 670 7. Acknowledgments 672 The authors would like to thank Adrian Farrel, Acee Lindem, JP 673 Vasseur, Dean Cheng, and Jean-Louis Le Roux for their review and 674 comments to this document. 676 8. References 678 8.1. Normative References 680 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 681 Requirement Levels", BCP 14, RFC 2119, March 1997. 683 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 684 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 685 Tunnels", RFC 3209, December 2001. 687 [RFC2370] R. Coltun, "The OSPF Opaque LSA Option", RFC2370, July 688 1998. 690 [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 692 [OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering 693 (TE) Extensions to OSPF Version 2", RFC 3630, September 694 2003. 696 [OSPF-V3-TE] Ishiguro K., Manral V., Davey A., and Lindem A. "Traffic 697 Engineering Extensions to OSPF version 3", draft-ietf-ospf- 698 ospfv3-traffic, {work in progress}. 700 [GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in Support 701 of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 702 4203, October 2005. 704 [OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", 705 RFC 2740, April 1998. 707 8.2. Informative References 709 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 710 Engineering Requirements", RFC4216, November 2005. 712 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 713 path computation method for establishing Inter-domain", RFC 714 5152, February 2008. 716 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward 717 Recursive PCE-based Computation (BRPC) procedure to compute 718 shortest inter-domain Traffic Engineering Label Switched 719 Paths ", draft-ietf-pce-brpc, (work in progress) 721 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 722 Element (PCE)-Based Architecture", RFC4655, August 2006. 724 [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- 725 Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in 726 progress). 728 [BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", 729 RFC4271, January 2006 731 Authors' Addresses 733 Mach(Guoyi) Chen 734 Huawei Technologies Co.,Ltd 735 KuiKe Building, No.9 Xinxi Rd., 736 Hai-Dian District 737 Beijing, 100085 738 P.R. China 740 Email: mach@huawei.com 742 Renhai Zhang 743 Huawei Technologies Co.,Ltd 744 KuiKe Building, No.9 Xinxi Rd., 745 Hai-Dian District 746 Beijing, 100085 747 P.R. China 749 Email: zhangrenhai@huawei.com 751 Xiaodong Duan 752 China Mobile 753 53A,Xibianmennei Ave,Xunwu District 754 Beijing, China 756 Email: duanxiaodong@chinamobile.com 758 Intellectual Property Statement 760 The IETF takes no position regarding the validity or scope of any 761 Intellectual Property Rights or other rights that might be claimed to 762 pertain to the implementation or use of the technology described in 763 this document or the extent to which any license under such rights 764 might or might not be available; nor does it represent that it has 765 made any independent effort to identify any such rights. 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