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Yeung 5 Expires: April 2003 Procket Networks 6 draft-katz-yeung-ospf-traffic-09.txt K. Kompella 7 Juniper Networks 8 October 2002 10 Traffic Engineering Extensions to OSPF Version 2 11 *** Draft *** 13 Status 15 This document is an Internet-Draft and is in full conformance with 16 all provisions of Section 10 of RFC2026. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 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 Copyright Notice 36 Copyright (C) The Internet Society (2002). All Rights Reserved. 38 Abstract 40 This document describes extensions to the OSPF protocol version 2 to 41 support intra-area Traffic Engineering, using Opaque Link State 42 Advertisements. 44 Changes 46 (This section to be removed before publication). 48 Per comments from the OSPF WG mailing list, the following changes 49 were made: 51 - State that operation over multi-access networks with more than two 52 TE devices is not expressly forbidden. 53 - Fix figure in 2.3.1. 54 - Specify that a Remote Interface IP Address sub-TLV is optional for 55 a multi-access link. 57 1. Introduction 59 This document specifies a method of adding traffic engineering 60 capabilities to OSPF Version 2 [1]. The architecture of traffic 61 engineering is described in [2]. The semantic content of the 62 extensions is essentially identical to the corresponding extensions 63 to IS-IS [3]. It is expected that the traffic engineering extensions 64 to OSPF will continue to mirror those in IS-IS. 66 The extensions provide a way of describing the traffic engineering 67 topology (including bandwidth and administrative constraints) and 68 distributing this information within a given OSPF area. This 69 topology does not necessarily match the regular routed topology, 70 though this proposal depends on Network LSAs to describe multiaccess 71 links. 73 1.1. Applicability 75 Many of the extensions specified in this document are in response to 76 the requirements stated in [2], and thus are referred to as "traffic 77 engineering extensions", and are also commonly associated with MPLS 78 Traffic Engineering. A more accurate (albeit bland) designation is 79 "extended link attributes", as what is proposed is simply to add more 80 attributes to links in OSPF advertisements. 82 The information made available by these extensions can be used to 83 build an extended link state database just as router LSAs are used to 84 build a "regular" link state database; the difference is that the 85 extended link state database (referred to below as the traffic 86 engineering database) has additional link attributes. Uses of the 87 traffic engineering database include: 89 o monitoring the extended link attributes; 90 o local constraint-based source routing; and 91 o global traffic engineering. 93 For example, an OSPF-speaking device can participate in an OSPF area, 94 build a traffic engineering database, and thereby report on the 95 reservation state of links in that area. 97 In "local constraint-based source routing", a router R can compute a 98 path from a source node A to a destination node B; typically, A is R 99 itself, and B is specified by a "router address" (see below). This 100 path may be subject to various constraints on the attributes of the 101 links and nodes that the path traverses, e.g., use green links that 102 have unreserved bandwidth of at least 10Mbps. This path could then 103 be used to carry some subset of the traffic from A to B, forming a 104 simple but effective means of traffic engineering. How the subset of 105 traffic is determined, and how the path is instantiated is beyond the 106 scope of this document; suffice it to say that one means of defining 107 the subset of traffic is "those packets whose IP destinations were 108 learned from B", and one means of instantiating paths is using MPLS 109 tunnels. As an aside, note that constraint-based routing can be NP- 110 hard, or even unsolvable, depending on the nature of the attributes 111 and constraints and thus many implementations will use heuristics. 112 Consequently, we don't attempt to sketch an algorithm here. 114 Finally, for "global traffic engineering", a device can build a 115 traffic engineering database, input a traffic matrix and an 116 optimization function, crunch on the information, and thus compute 117 optimal or near-optimal routing for the entire network. The device 118 can subsequently monitor the traffic engineering topology and react 119 to changes by recomputing the optimal routes. 121 1.2. Limitations 123 As mentioned above, this document specifies extensions and procedures 124 for intra-area distribution of Traffic Engineering information. 125 Methods for inter-area and inter-AS (Autonomous System) are not 126 discussed here. 128 The extensions specified in this document capture the reservation 129 state of point-to-point links. The reservation state of multiaccess 130 links may not be accurately reflected, except in the special case 131 that there are only two devices in the multiaccess subnetwork. 132 Operation over multiaccess networks with more than two devices is not 133 specifically prohibited. More accurate description of the 134 reservation state of multi-access networks is for further study. 136 This document also does not support unnumbered links. This 137 deficiency is addressed in [4]; see also [5] and [6]. 139 1.3. Conventions 141 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 142 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 143 document are to be interpreted as described in RFC 2119 [7]. 145 2. LSA Format 147 2.1. LSA type 149 This extension makes use of the Opaque LSA [8]. 151 Three types of Opaque LSAs exist, each of which has different 152 flooding scope. This proposal uses only Type 10 LSAs, which have 153 area flooding scope. 155 One new LSA is defined, the Traffic Engineering LSA. This LSA 156 describes routers, point-to-point links, and connections to 157 multiaccess networks (similar to a Router LSA). For traffic 158 engineering purposes, the existing Network LSA suffices for 159 describing multiaccess links, so no additional LSA is defined for 160 this purpose. 162 2.2. LSA ID 164 The LSA ID of an Opaque LSA is defined as having eight bits of type 165 and 24 bits of type-specific data. The Traffic Engineering LSA uses 166 type 1. The remaining 24 bits are the Instance field, as follows: 168 0 1 2 3 169 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 1 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | 1 | Instance | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 The Instance field is an arbitrary value used to maintain multiple 175 Traffic Engineering LSAs. A maximum of 16777216 Traffic Engineering 176 LSAs may be sourced by a single system. The LSA ID has no 177 topological significance. 179 2.3. LSA Format Overview 181 2.3.1. LSA Header 183 The Traffic Engineering LSA starts with the standard LSA header: 185 0 1 2 3 186 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 1 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 | LS age | Options | 10 | 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 | 1 | Instance | 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 | Advertising Router | 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 | LS sequence number | 195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 196 | LS checksum | Length | 197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 2.3.2. TLV Header 201 The LSA payload consists of one or more nested Type/Length/Value 202 (TLV) triplets for extensibility. The format of each TLV is: 204 0 1 2 3 205 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 1 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | Type | Length | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Value... | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 The Length field defines the length of the value portion in octets 213 (thus a TLV with no value portion would have a length of zero). The 214 TLV is padded to four-octet alignment; padding is not included in 215 the length field (so a three octet value would have a length of 216 three, but the total size of the TLV would be eight octets). Nested 217 TLVs are also 32-bit aligned. Unrecognized types are ignored. 219 This memo defines Types 1 and 2. See the IANA Considerations section 220 for allocation of new Types. 222 2.4. LSA payload details 224 An LSA contains one top-level TLV. 226 There are two top-level TLVs defined: 228 1 - Router Address 229 2 - Link 231 2.4.1. Router Address TLV 233 The Router Address TLV specifies a stable IP address of the 234 advertising router that is always reachable if there is any 235 connectivity to it. This is typically implemented as a "loopback 236 address"; the key attribute is that the address does not become 237 unusable if an interface is down. In other protocols this is known 238 as the "router ID," but for obvious reasons this nomenclature is 239 avoided here. If a router advertises BGP routes with the BGP next 240 hop attribute set to the BGP router ID, then the Router Address 241 SHOULD be the same as the BGP router ID. 243 If IS-IS is also active in the domain, this address can also be used 244 to compute the mapping between the OSPF and IS-IS topologies. For 245 example, suppose a router R is advertising both IS-IS and OSPF 246 Traffic Engineering LSAs, and suppose further that some router S is 247 building a single Traffic Engineering Database (TED) based on both 248 IS-IS and OSPF TE information. R may then appear as two separate 249 nodes in S's TED; however, if both the IS-IS and OSPF LSAs generated 250 by R contain the same Router Address, then S can determine that the 251 IS-IS TE LSA and the OSPF TE LSA from R are indeed from a single 252 router. 254 The router address TLV is type 1, and has a length of 4, and the 255 value is the four octet IP address. It must appear in exactly one 256 Traffic Engineering LSA originated by a router. 258 2.4.2. Link TLV 260 The Link TLV describes a single link. It is constructed of a set of 261 sub-TLVs. There are no ordering requirements for the sub-TLVs. 263 Only one Link TLV shall be carried in each LSA, allowing for fine 264 granularity changes in topology. 266 The Link TLV is type 2, and the length is variable. 268 The following sub-TLVs are defined: 270 1 - Link type (1 octet) 271 2 - Link ID (4 octets) 272 3 - Local interface IP address (4 octets) 273 4 - Remote interface IP address (4 octets) 274 5 - Traffic engineering metric (4 octets) 275 6 - Maximum bandwidth (4 octets) 276 7 - Maximum reservable bandwidth (4 octets) 277 8 - Unreserved bandwidth (32 octets) 278 9 - Administrative group (4 octets) 280 This memo defines sub-Types 1 through 9. See the IANA Considerations 281 section for allocation of new sub-Types. 283 The Link Type and Link ID sub-TLVs are mandatory, i.e., must appear 284 exactly once. All other sub-TLVs defined here may occur at most 285 once. These restrictions need not apply to future sub-TLVs. 286 Unrecognized sub-TLVs are ignored. 288 Various values below use the (32 bit) IEEE Floating Point format. 289 For quick reference, this format is as follows: 291 0 1 2 3 292 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 1 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 |S| Exponent | Fraction | 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 where S is the sign; Exponent is the exponent base 2 in "excess 127" 298 notation; and Fraction is the mantissa - 1, with an implied binary 299 point in front of it. Thus the above represents the value 300 (-1)**(S) * 2**(Exponent-127) * (1 + Fraction) 302 For more details, refer to [9]. 304 2.5. Sub-TLV Details 306 2.5.1. Link Type 308 The Link Type sub-TLV defines the type of the link: 310 1 - Point-to-point 311 2 - Multiaccess 313 The Link Type sub-TLV is TLV type 1, and is one octet in length. 315 2.5.2. Link ID 317 The Link ID sub-TLV identifies the other end of the link. For point- 318 to-point links, this is the Router ID of the neighbor. For 319 multiaccess links, this is the interface address of the designated 320 router. The Link ID is identical to the contents of the Link ID 321 field in the Router LSA for these link types. 323 The Link ID sub-TLV is TLV type 2, and is four octets in length. 325 2.5.3. Local Interface IP Address 327 The Local Interface IP Address sub-TLV specifies the IP address(es) 328 of the interface corresponding to this link. If there are multiple 329 local addresses on the link, they are all listed in this sub-TLV. 331 The Local Interface IP Address sub-TLV is TLV type 3, and is 4N 332 octets in length, where N is the number of local addresses. 334 2.5.4. Remote Interface IP Address 336 The Remote Interface IP Address sub-TLV specifies the IP address(es) 337 of the neighbor's interface corresponding to this link. This and the 338 local address are used to discern multiple parallel links between 339 systems. If the Link Type of the link is Multiaccess, the Remote 340 Interface IP Addess is set to 0.0.0.0; alternatively, an 341 implementation MAY choose not to send this sub-TLV. 343 The Remote Interface IP Address sub-TLV is TLV type 4, and is 4N 344 octets in length, where N is the number of neighbor addresses. 346 2.5.5. Traffic Engineering Metric 348 The Traffic Engineering Metric sub-TLV specifies the link metric for 349 traffic engineering purposes. This metric may be different than the 350 standard OSPF link metric. Typically, this metric is assigned by a 351 network admistrator. 353 The Traffic Engineering Metric sub-TLV is TLV type 5, and is four 354 octets in length. 356 2.5.6. Maximum Bandwidth 358 The Maximum Bandwidth sub-TLV specifies the maximum bandwidth that 359 can be used on this link in this direction (from the system 360 originating the LSA to its neighbor), in IEEE floating point format. 361 This is the true link capacity. The units are bytes per second. 363 The Maximum Bandwidth sub-TLV is TLV type 6, and is four octets in 364 length. 366 2.5.7. Maximum Reservable Bandwidth 368 The Maximum Reservable Bandwidth sub-TLV specifies the maximum 369 bandwidth that may be reserved on this link in this direction, in 370 IEEE floating point format. Note that this may be greater than the 371 maximum bandwidth (in which case the link may be oversubscribed). 372 This SHOULD be user-configurable; the default value should be the 373 Maximum Bandwidth. The units are bytes per second. 375 The Maximum Reservable Bandwidth sub-TLV is TLV type 7, and is four 376 octets in length. 378 2.5.8. Unreserved Bandwidth 380 The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth 381 not yet reserved at each of the eight priority levels, in IEEE 382 floating point format. The values correspond to the bandwidth that 383 can be reserved with a setup priority of 0 through 7, arranged in 384 increasing order with priority 0 occurring at the start of the sub- 385 TLV, and priority 7 at the end of the sub-TLV. The initial values 386 (before any bandwidth is reserved) are all set to the Maximum 387 Reservable Bandwidth. Each value will be less than or equal to the 388 Maximum Reservable Bandwidth. The units are bytes per second. 390 The Unreserved Bandwidth sub-TLV is TLV type 8, and is 32 octets in 391 length. 393 2.5.9. Administrative Group 395 The Administrative Group sub-TLV contains a 4-octet bit mask assigned 396 by the network administrator. Each set bit corresponds to one 397 administrative group assigned to the interface. A link may belong to 398 multiple groups. 400 By convention the least significant bit is referred to as 'group 0', 401 and the most significant bit is referred to as 'group 31'. 403 The Administrative Group is also called Resource Class/Color [2]. 405 The Administrative Group sub-TLV is TLV type 9, and is four octets in 406 length. 408 3. Elements of Procedure 410 Routers shall originate Traffic Engineering LSAs whenever the LSA 411 contents change, and whenever otherwise required by OSPF (an LSA 412 refresh, for example). Note that this does not mean that every 413 change must be flooded immediately; an implementation MAY set 414 thresholds (for example, a bandwidth change threshold) that trigger 415 immediate flooding, and initiate flooding of other changes after a 416 short time interval. In any case, the origination of Traffic 417 Engineering LSAs SHOULD be rate-limited to at most one every 418 MinLSInterval [1]. 420 Upon receipt of a changed Traffic Engineering LSA or Network LSA 421 (since these are used in traffic engineering calculations), the 422 router should update its traffic engineering database. No SPF or 423 other route calculations are necessary. 425 4. Compatibility Issues 427 There should be no interoperability issues with routers that do not 428 implement these extensions, as the Opaque LSAs will be silently 429 ignored. 431 The result of having routers that do not implement these extensions 432 is that the traffic engineering topology will be missing pieces; 433 however, if the topology is connected, TE paths can still be 434 calculated and ought to work. 436 5. Normative References 438 [1] Moy, J., "OSPF Version 2", RFC 2328, April 1998. 440 [4] Kompella, K., Rekhter, Y., et al, "OSPF Extensions in Support of 441 Generalized MPLS," work in progress. 443 [6] Kompella, K., and Y. Rekhter, "Signalling Unnumbered Links in 444 RSVP-TE," work in progress. 446 [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement 447 Levels", BCP 14, RFC 2119, March 1997. 449 [8] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998. 451 [9] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic", 452 Standard 754-1985, 1985 (ISBN 1-5593-7653-8). 454 6. Informative References 456 [2] Awduche, D., et al, "Requirements for Traffic Engineering Over 457 MPLS," RFC 2702, September 1999. 459 [3] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering," 460 work in progress. 462 [5] Kompella, K., Rekhter, Y., and A. Kullberg, "Signalling 463 Unnumbered Links in CR-LDP," work in progress. 465 [10] Narten, T., and H. Alvestrand, "Guidelines for Writing an IANA 466 Considerations Section in RFCs", RFC 2434, BCP 26, October 1998. 468 [11] Murphy, S., Badger, M., and B. Wellington, "OSPF with Digital 469 Signatures", RFC 2154, June 1997. 471 7. Security Considerations 473 This document specifies the contents of Opaque LSAs in OSPFv2. As 474 Opaque LSAs are not used for SPF computation or normal routing, the 475 extensions specified here have no affect on IP routing. Tampering 476 with TE LSAs may have an effect on traffic engineering computations, 477 however, and it is suggested that whatever mechanisms are used for 478 securing the transmission of normal OSPF LSAs be applied equally to 479 all Opaque LSAs, including the TE LSAs specified here. 481 Note that the mechanisms in [1] and [11] apply to Opaque LSAs. It is 482 suggested that any future mechanisms proposed to secure/authenticate 483 OSPFv2 LSA exchanges be made general enough to be used with Opaque 484 LSAs. 486 8. IANA Considerations 488 The top level Types in a TE LSA as well as Types for sub-TLVs in a TE 489 Link TLV are to be registered with IANA. 491 Following the guidelines set in [10], top level Types in TE LSAs from 492 3 through 32767 are to be assigned by Expert Review (the said Expert 493 to be decided by the IESG). Types from 32768 through 65535 are 494 reserved for Private Use. In all cases, assigned values Types MUST 495 be registered with IANA. 497 Also, sub-Types of a TE Link TLV from 10 to 32767 are to be assigned 498 by Expert Review; values from 32768 through 32772 are reserved for 499 Private Use; and values from 32773 through 65535 are to be assigned 500 First Come First Served. In all cases, assigned values are to be 501 registered with IANA. 503 9. Authors' Addresses 505 Dave Katz 506 Juniper Networks 507 1194 N. Mathilda Ave. 508 Sunnyvale, CA 94089 USA 510 Phone: +1 408 745 2000 511 Email: dkatz@juniper.net 513 Derek M. Yeung 514 Procket Networks, Inc. 515 1100 Cadillac Court 516 Milpitas, CA 95035 USA 518 Phone: +1 408 635-7900 519 Email: myeung@procket.com 521 Kireeti Kompella 522 Juniper Networks 523 1194 N. Mathilda Ave. 524 Sunnyvale, CA 94089 USA 526 Phone: +1 408 745 2000 527 Email: kireeti@juniper.net 529 10. IPR Notices 531 The IETF takes no position regarding the validity or scope of any 532 intellectual property or other rights that might be claimed to 533 pertain to the implementation or use of the technology described in 534 this document or the extent to which any license under such rights 535 might or might not be available; neither does it represent that it 536 has made any effort to identify any such rights. Information on the 537 IETF's procedures with respect to rights in standards-track and 538 standards-related documentation can be found in BCP-11. 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