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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network work group Mach Chen 2 Internet Draft Renhai Zhang 3 Expires: March 2008 Huawei Technologies Co.,Ltd 4 Category: Standards Track September 6, 2007 6 OSPF Traffic Engineering (OSPF-TE) Extensions in Support of Inter-AS 7 Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) 8 Traffic Engineering 9 draft-ietf-ccamp-ospf-interas-te-extension-01.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that 14 any applicable patent or other IPR claims of which he or she is 15 aware have been or will be disclosed, and any of which he or she 16 becomes aware will be disclosed, in accordance with Section 6 of 17 BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that other 21 groups may also distribute working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html 34 This Internet-Draft will expire on March 6, 2008. 36 Abstract 38 This document describes extensions to the OSPF v2 and v3 Traffic 39 Engineering (OSPF-TE) mechanisms to support Multiprotocol Label 40 Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering(TE) 41 for multiple Autonomous Systems (ASes). It defines OSPF-TE extensions 42 for the flooding of TE information about inter-AS links which can be 43 used to perform inter-AS TE path computation. 45 Conventions used in this document 47 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 48 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 49 document are to be interpreted as described in RFC-2119 [RFC2119]. 51 Table of Contents 53 1. Introduction.................................................2 54 2. Problem Statement............................................3 55 2.1. A Note on Non-Objectives................................3 56 2.2. Per-Domain Path Determination...........................4 57 2.3. Backward Recursive Path Computation.....................6 58 3. Extensions to OSPF-TE........................................7 59 3.1. Remote AS Number Sub-TLV................................7 60 3.2. Inter-AS Link Type......................................8 61 3.3. Link ID.................................................8 62 4. Procedure for Inter-AS TE Links..............................8 63 5. Security Considerations......................................9 64 6. IANA Considerations.........................................10 65 6.1. OSPF LSA Sub-TLVs type.................................10 66 6.2. OSPF TE Link Type......................................10 67 7. Acknowledgments.............................................10 68 8. References..................................................11 69 8.1. Normative References...................................11 70 8.2. Informative References.................................11 71 Authors' Addresses.............................................12 72 Intellectual Property Statement................................12 73 Disclaimer of Validity.........................................13 74 Copyright Statement............................................13 76 1. Introduction 78 [OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support 79 intra-area Traffic Engineering (TE). The extensions provide a way of 80 encoding the TE information for TE-enabled links within the network 81 (TE links) and flooding this information within an area. Type 10 82 opaque LSAs [RFC2370] are used to carry such TE information. Two top- 83 level TLVs are defined in [OSPF-TE]: Router Address TLV and Link TLV. 84 The Link TLV has several nested sub-TLVs which describe the TE 85 attributes for a TE link. 87 [OSPF-TE-V3] defines similar extensions to OSPFv3 [OSPFV3]. 89 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 90 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 91 (ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- 92 TE-REQ], a method SHOULD provide the ability to compute a path 93 spanning multiple ASes. So a path computation entity that may be the 94 head-end Label Switching Router (LSR), an AS Border Router (ASBR), or 95 a Path Computation Element (PCE [PCE]) needs to know the TE 96 information not only of the links within an AS, but also of the links 97 that connect to other ASes. 99 In this document, some extensions to OSPF-TE are defined in support 100 of carrying inter-AS TE link information for inter-AS Traffic 101 Engineering. A new sub-TLV is added to the Link TLV and a new link 102 type is introduced. The extensions are equally applicable to OSPFv2 103 and OSPFv3 as identical extensions to [OSPF-TE] and [OSPF-TE-V3]. The 104 detailed definitions and procedures are discussed in the following 105 sections. 107 2. Problem Statement 109 As described in [INTER-AS-TE-REQ], in the case of establishing an 110 inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] 111 may include the following elements in the Explicit Route Object (ERO) 112 in order to describe the path of the LSP: 114 - a set of AS numbers as loose hops; and/or 116 - a set of LSRs including ASBRs as loose hops. 118 Two methods for determining inter-AS paths are currently discussed. 119 The per-domain method [PD-PATH] determines the path one domain at a 120 time. The backward recursive method [BRPC] uses cooperation between 121 PCEs to determine an optimum inter-domain path. The sections that 122 follow examine how inter-AS TE link information could be useful in 123 both cases. 125 2.1. A Note on Non-Objectives 127 It is important to note that this document does not make any change 128 to the confidentiality and scaling assumptions surrounding the use of 129 ASes in the Internet. In particular, this document is conformant to 130 the requirements set out in [INTER-AS-TE-REQ]. 132 The following lists of features are explicit exclusions. 134 o There is no attempt to distribute TE information from within one 135 AS to another AS. 137 o There is no mechanism proposed to distribute any form of TE 138 reachability information for destinations outside the AS. 140 o There is no proposed change to the PCE architecture or usage. 142 o TE aggregation is not supported or recommended. 144 o There is no exchange of private information between ASes. 146 o No OSPF adjacencies are formed on the inter-AS link. 148 Note further that the extensions proposed in this document are 149 limited to use for information about inter-AS TE links. L1VPN Auto- 150 Discovery [L1VPN-OSPF-AD] defines how TE information about links 151 between Customer Edge (CE) equipment and Provider Edge (PE) equipment 152 can be advertised in OSPF-TE alongside the auto-discovery information 153 for the CE-PE links. That is separate functionality and does not 154 overlap with the function defined in this document. 156 2.2. Per-Domain Path Determination 158 In the per-domain method of determining an inter-AS path for an MPLS- 159 TE LSP, when an LSR that is an entry-point to an AS receives a PATH 160 message from an upstream AS with an ERO containing a next hop that is 161 an AS number, it needs to find which LSRs (ASBRs) within the local AS 162 are connected to the downstream AS so that it can compute a TE LSP 163 segment across the AS to one of those LSRs and forward the PATH 164 message to the LSR and hence into the next AS. See the figure below 165 for an example: 167 R1------R3----R5-----R7------R9-----R11 168 | | \ | / | 169 | | \ | ---- | 170 | | \ | / | 171 R2------R4----R6 --R8------R10----R12 172 : : 173 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 175 Figure 1: Inter-AS Reference Model 177 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 178 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 179 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 181 If an inter-AS TE LSP is planned to be established from R1 to R12, 182 the AS sequence is limited as: AS1, AS2, AS3. 184 Suppose that the Path message enters AS2 from R3. The next hop in the 185 ERO shows AS3, and R5 must determine a path segment across AS2 to 186 reach AS3. It has a choice of three exit points from AS2 (R6, R7, and 187 R8) and it needs to know which of these provide TE connectivity to 188 AS3, and whether the TE connectivity (for example, available 189 bandwidth) is adequate for the requested LSP. 191 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 192 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 193 connects to R9. Since there may be multiple exist ASBRs that are 194 connected to R9 (both R7 and R8 in this example), R5 also needs to 195 know the TE properties of the inter-AS TE links so that it can select 196 the correct exit ASBR. 198 Once the path message reaches the exit ASBR, any choice of inter-AS 199 TE link can be made by the ASBR if not already made by entry ASBR 200 that computed the segment. 202 More details can be found in the Section 4.0 of [PD-PATH], which 203 clearly points out why advertising of inter-AS links is desired. 205 To enable R5 to make the correct choice of exit ASBR the following 206 information is needed: 208 o List of all inter-AS TE links for the local AS. 210 o TE properties of each inter-AS TE link. 212 o AS number of the neighboring AS connected to by each inter-AS TE 213 link. 215 o Identity (TE Router ID) of the neighboring ASBR connected to by 216 each inter-AS TE link. 218 In GMPLS networks further information may also be required to select 219 the correct TE links as defined in [GMPLS-TE]. 221 The example above shows how this information is needed at the entry 222 point ASBRs for each AS (or the PCEs that provide computation 223 services for the ASBRs), but this information is also needed 224 throughout the local AS if path computation function is fully 225 distributed among LSRs in the local AS, for example to support LSPs 226 that have start points (ingress nodes) within the AS. 228 2.3. Backward Recursive Path Computation 230 Another scenario using PCE techniques has the same problem. [BRPC] 231 defines a PCE-based TE LSP computation method (called Backward 232 Recursive Path Computation) to compute optimal inter-domain 233 constrained MPLS-TE or GMPLS LSPs. In this path computation method, a 234 specific set of traversed domains (ASes) are assumed to be selected 235 before computation starts. Each downstream PCE in domain(i) returns 236 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 237 tree of potential paths. Each tree consists of the set of paths from 238 all Boundary Nodes located in domain(i) to the destination where each 239 path satisfies the set of required constraints for the TE LSP 240 (bandwidth, affinities, etc.). 242 So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide 243 connectivity from the upstream AS. In order that the tree of paths 244 provided by one PCE to its neighbor can be correlated, the identities 245 of the ASBRs for each path need to be referenced, so the PCE must 246 know the identities of the ASBRs in the remote AS reached by any 247 inter-AS TE link, and, in order that it provides only suitable paths 248 in the tree, the PCE must know the TE properties of the inter-AS TE 249 links. See the following figure as an example: 251 PCE1<------>PCE2<-------->PCE3 252 / : : 253 / : : 254 R1------R3----R5-----R7------R9-----R11 255 | | \ | / | 256 | | \ | ---- | 257 | | \ | / | 258 R2------R4----R6 --R8------R10----R12 259 : : 260 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 262 Figure 2: BRPC for Inter-AS Reference Model 264 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 265 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 266 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 267 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path 268 computation and are responsible for path segment computation within 269 their own domains. 271 If an inter-AS TE LSP is planned to be established from R1 to R12, 272 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 273 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 274 request originated from the PCC (R1) is relayed by PCE1 and PCE2 275 along the PCE chain to PCE3, then PCE3 begins to compute the path 276 segments from the entry boundary nodes that provide connection from 277 AS2 to the destination (R12). But, to provide suitable path segments, 278 PCE3 must determine which entry boundary nodes provide connectivity 279 to its upstream neighbor AS (identified by its AS number), and must 280 know the TE properties of the inter-AS TE links. In the same way, 281 PCE2 also needs to determine the entry boundary nodes according to 282 its upstream neighbor AS and the inter-AS TE link capabilities. 284 Thus, to support Backward Recursive Path Computation the same 285 information as listed in Section 2.2 is required. 287 3. Extensions to OSPF-TE 289 Note that this document does not define mechanisms for distribution 290 of TE information from one AS to another, does not distribute any 291 form of TE reachability information for destinations outside the AS, 292 does not change the PCE architecture or usage, does not suggest or 293 recommend any form of TE aggregation, and does not feed private 294 information between ASes. See section 2.1. 296 The extensions defined in this document allow an inter-AS TE link 297 advertisement to be easily identified as such by the use of a new 298 link type. A new sub-TLV to the Link TLV is defined to carry the 299 information about the neighboring AS. The extensions are equally 300 applicable to TE distribution using OSPFv2 and OSPFv3. 302 3.1. Remote AS Number Sub-TLV 304 As described in [OSPF-TE], the Link TLV describes a single link and 305 consists of a set of sub-TLVs. A new sub-TLV, the Remote AS Number 306 sub-TLV is added to the Link TLV when advertising inter-AS links. The 307 Remote AS Number sub-TLV specifies the AS number of the neighboring 308 AS to which the advertised link connects. The Remote AS number sub- 309 TLV is mandatory for an inter-AS TE link. 311 The Remote AS number sub-TLV is TLV type 21 (which needs to be 312 confirmed by IANA), and is four octets in length. The format is as 313 follows: 315 0 1 2 3 316 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 1 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 | Type | Length | 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | Remote AS Number | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 The Remote AS number field has 4 octets. When only two octets are 324 used for the AS number, as in current deployments, the left (high- 325 order) two octets MUST be set to zero. 327 3.2. Inter-AS Link Type 329 To identify a link as an inter-AS link and allow easy identification 330 of these new advertisements, a new Link Type value is defined for use 331 in the Link Type sub-TLV. The value of the Link Type for an inter-AS 332 point-to-point link is 3 (which needs to be confirmed by IANA). 334 The use of multi-access inter-AS TE links is for future study. 336 3.3. Link ID 338 For an inter-AS link, the Link ID carried in the Link ID sub-TLV is 339 the remote ASBR identifier which could be any address of the remote 340 ASBR(e.g., the TE Router ID, Router ID or interface address of the 341 remote ASBR reached through this inter-AS link). The TE Router ID is 342 RECOMMENDED. 344 4. Procedure for Inter-AS TE Links 346 When TE is enabled on an inter-AS link and the link is up, the ASBR 347 SHOULD advertise this link using the normal procedures for OSPF-TE 348 [OSPF-TE]. When either the link is down or TE is disabled on the 349 link , the ASBR SHOULD withdraw the advertisement. When there are 350 changes to the TE parameters for the link (for example, when the 351 available bandwidth changes) the ASBR SHOULD re-advertise the link, 352 but the ASBR MUST take precautions against excessive re- 353 advertisements as described in [OSPF-TE]. 355 Hellos MUST NOT be exchanged (and consequently, an OSPF adjacency 356 MUST NOT be formed) over the inter-AS link. 358 The information advertised comes from the ASBR's knowledge of the TE 359 capabilities of the link, the ASBR's knowledge of the current status 360 and usage of the link, and configuration at the ASBR of the remote AS 361 number and remote ASBR TE Router ID. 363 The TE link advertisement SHOULD be carried in a Type 10 Opaque LSA 364 if the flooding scope is to be limited to within the single IGP area 365 to which the ASBR belongs, or MAY be carried in a Type 11 Opaque LSA 366 if the information should reach all routers (including area border 367 routers, ASBRs, and PCEs) in the AS. The choice between the use of a 368 Type 10 or Type 11 Opaque LSA is a network-wide policy choice, and 369 configuration control SHOULD be provided in ASBR implementations that 370 support the advertisement of inter-AS TE links. 372 Legacy routers receiving an advertisement for an inter-AS TE link are 373 able to ignore it because the Link Type carries an unknown value. 374 They will continue to flood the LSA, but will not attempt to use the 375 information received as if the link were an intra-AS TE link. 377 Since there is no OSPF adjacency running on the inter-AS link, the 378 local ASBR SHOULD do a "proxy" advertisement for the backward 379 direction of an inter-AS TE link, which facilitates a path 380 computation entity to do a 2-way check before including the link in a 381 path computation. As the objective of such a "proxy" advertisement is 382 to avoid using an inter-AS TE link when the backward direction of the 383 inter-AS TE link is unavailable or unsuitable, only some mandatory or 384 essential TE information needs to be advertised, i.e. the Link ID, 385 the Link Type, and the Remote AS number of an inter-AS TE link. 387 Routers or PCEs that are capable of processing advertisements of 388 inter-AS TE links SHOULD NOT use such links to compute paths that 389 exit an AS to a remote ASBR and then immediately re-enter the AS 390 through another TE link. Such paths would constitute extremely rare 391 occurrences and SHOULD NOT be allowed except as the result of 392 specific policy configurations at the router or PCE computing the 393 path. 395 5. Security Considerations 397 The protocol extensions defined in this document are relatively minor 398 and can be secured within the AS in which they are used by the 399 existing OSPF security mechanisms. 401 There is no exchange of information between ASes, and no change to 402 the OSPF security relationship between the ASes. In particular, since 403 no OSPF adjacency is formed on the inter-AS links, there is no 404 requirement for OSPF security between the ASes. 406 It should be noted, however, that some of the information included in 407 these new advertisements(the remote AS number and the remote ASBR ID) 408 are obtained from a neighboring administration and cannot be verified 409 in anyway. Since the means of delivery of this information is likely 410 to be part of a commercial relationship, the source of the 411 information should be carefully checked before it is entered as 412 configuration information at the ASBR responsible for advertising the 413 inter-AS TE links. 415 6. IANA Considerations 417 IANA is requested to make the following allocations from registries 418 under its control. 420 6.1. OSPF LSA Sub-TLVs type 422 IANA maintains the "Open Shortest Path First (OSPF) Traffic 423 Engineering TLVs" registry with sub-registry "Types for sub-TLVs in a 424 TE Link TLV". IANA is requested to assign a new sub-TLV as follows. 425 The number 21 is suggested as shown in Section 3.1. 427 Value Meaning 429 21 Remote AS Number sub-TLV. 431 6.2. OSPF TE Link Type 433 IANA is requested to create a new sub-registry "TE Link Types" of the 434 registry "Open Shortest Path First (OSPF) Traffic Engineering TLVs" 435 to track TE Link Types. 437 The sub-registry should read as follows: 439 [OSPF-TE] defines the Link Type sub-TLV of the Link TLV. The 440 following values are defined. 442 Value Meaning Reference 444 1 Point-to-point link [OSPF-TE] 446 2 Multi-access link [OSPF-TE] 448 3 Inter-AS link [this document] 450 New allocations from this registry are by IETF Standards Action. 452 7. Acknowledgments 454 The authors would like to thank Adrian Farrel, Acee Lindem, JP 455 Vasseur, Dean Cheng, and Jean-Louis Le Roux for their review and 456 comments to this document. 458 8. References 460 8.1. Normative References 462 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 463 Requirement Levels", BCP 14, RFC 2119, March 1997. 465 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 466 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 467 Tunnels", RFC 3209, December 2001. 469 [RFC2370] R. Coltun, "The OSPF Opaque LSA Option", RFC2370, July 470 1998. 472 [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 474 [OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering 475 (TE) Extensions to OSPF Version 2", RFC 3630, September 476 2003. 478 [GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in Support 479 of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 480 4203, October 2005. 482 8.2. Informative References 484 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 485 Engineering Requirements", RFC4216, November 2005. 487 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 488 path computation method for establishing Inter-domain", 489 draft-ietf-ccamp-inter-domain-pd-path-comp, (work in 490 progress). 492 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward 493 Recursive PCE-based Computation (BRPC) procedure to compute 494 shortest inter-domain Traffic Engineering Label Switched 495 Paths ", draft-ietf-pce-brpc, (work in progress) 497 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 498 Element (PCE)-Based Architecture", RFC4655, August 2006. 500 [OSPF-TE-V3] Ishiguro K., Manral V., Davey A., and Lindem A. "Traffic 501 Engineering Extensions to OSPF version 3", draft-ietf-ospf- 502 ospfv3-traffic, {work in progress}. 504 [OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 505 2740, April 1998. 507 [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- 508 Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in 509 progress). 511 Authors' Addresses 513 Mach Chen 514 Huawei Technologies Co.,Ltd 515 KuiKe Building, No.9 Xinxi Rd., 516 Hai-Dian District 517 Beijing, 100085 518 P.R. China 520 Email: mach@huawei.com 522 Renhai Zhang 523 Huawei Technologies Co.,Ltd 524 KuiKe Building, No.9 Xinxi Rd., 525 Hai-Dian District 526 Beijing, 100085 527 P.R. China 529 Email: zhangrenhai@huawei.com 531 Intellectual Property Statement 533 The IETF takes no position regarding the validity or scope of any 534 Intellectual Property Rights or other rights that might be claimed to 535 pertain to the implementation or use of the technology described in 536 this document or the extent to which any license under such rights 537 might or might not be available; nor does it represent that it has 538 made any independent effort to identify any such rights. 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Please address the information to the IETF at 553 ietf-ipr@ietf.org. 555 Disclaimer of Validity 557 This document and the information contained herein are provided on an 558 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 559 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 560 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 561 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 562 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 563 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 565 Copyright Statement 567 Copyright (C) The IETF Trust (2007). 569 This document is subject to the rights, licenses and restrictions 570 contained in BCP 78, and except as set forth therein, the authors 571 retain all their rights.