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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 1142 (Obsoleted by RFC 7142) ** Obsolete normative reference: RFC 4971 (Obsoleted by RFC 7981) ** Obsolete normative reference: RFC 5316 (Obsoleted by RFC 9346) == Outdated reference: A later version (-12) exists of draft-ietf-pce-pcep-domain-sequence-05 Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group D. Dhody 3 Internet-Draft U. Palle 4 Intended status: Experimental Huawei Technologies India Pvt Ltd 5 Expires: March 19, 2015 September 15, 2014 7 ISIS Protocol Extensions for Boundary Node Discovery (BND) 8 draft-dhody-pce-bn-discovery-isis-09 10 Abstract 12 The Path Computation Element (PCE) may be used for computing multi- 13 domain (Area or AS) Multiprotocol Label Switching (MPLS) and 14 Generalized MPLS (GMPLS) Traffic Engineered (TE) Label Switch Path 15 (LSP). 17 In this circumstance, it is highly desirable to be able to 18 dynamically and automatically discover a set of Boundary Nodes (BN) 19 along with their domain information in a simple way. For that 20 purpose, this document defines extensions to the Intermediate System 21 to Intermediate System(IS-IS) routing protocol for the advertisement 22 of Boundary Node (BN)Discovery information within an IS-IS area or 23 within the entire IS-IS routing domain. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on March 19, 2015. 42 Copyright Notice 44 Copyright (c) 2014 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. Applications . . . . . . . . . . . . . . . . . . . . . . . . 4 63 4. Existing Mechanisms . . . . . . . . . . . . . . . . . . . . . 6 64 4.1. ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 4.2. Inter-AS TE Link . . . . . . . . . . . . . . . . . . . . 6 66 4.3. ISIS Area Topology . . . . . . . . . . . . . . . . . . . 6 67 5. Other Considerations . . . . . . . . . . . . . . . . . . . . 6 68 5.1. Static Configurations . . . . . . . . . . . . . . . . . . 6 69 5.2. Importance of Domain Information along with BNs . . . . . 6 70 5.3. Relationship to Domain-Sequence . . . . . . . . . . . . . 7 71 6. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 6.1. Boundary Node (BN) Discovery Information . . . . . . . . 7 73 6.2. Flooding Scope . . . . . . . . . . . . . . . . . . . . . 7 74 7. The IS-IS BND Sub-TLV . . . . . . . . . . . . . . . . . . . . 7 75 7.1. BN-ADDRESS Sub-TLV . . . . . . . . . . . . . . . . . . . 8 76 7.2. BN-DOMAIN Sub-TLV . . . . . . . . . . . . . . . . . . . . 9 77 8. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 9 78 9. Backward Compatibility . . . . . . . . . . . . . . . . . . . 10 79 10. Impact on Network . . . . . . . . . . . . . . . . . . . . . . 10 80 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 81 12. Security Considerations . . . . . . . . . . . . . . . . . . . 11 82 13. Manageability Considerations . . . . . . . . . . . . . . . . 11 83 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 84 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 85 15.1. Normative References . . . . . . . . . . . . . . . . . . 11 86 15.2. Informative References . . . . . . . . . . . . . . . . . 12 88 1. Introduction 90 This document defines extensions to IS-IS [ISO10589] to allow a 91 boundary node in an IS-IS routing domain to advertise its location, 92 along with domain information. 94 Generic capability advertisement mechanisms for IS-IS are defined in 95 [RFC4971]. These allow a router to advertise its capabilities within 96 an IS-IS area or an entire IS-IS routing domain. This document 97 leverages this generic capability advertisement mechanism to fully 98 satisfy the dynamic BN discovery. 100 This document defines a new sub-TLV (named the BN Discovery (BND))to 101 be carried within the IS-IS Router Capability TLV ([RFC4971]). 103 The BN information advertised is detailed in Section 6. Protocol 104 extensions and procedures are defined in Section 7 and Section 8. 106 A detailed description about the need for auto discovery of Boundary 107 Nodes (BN) and thier domains is also provided in this document. 109 The IS-IS extensions defined in this document allow for BN discovery 110 within an IS-IS routing domain. Boundary Node can be an Area Border 111 Router (ABR) or Autonomous System Border Router (ASBR). 113 This document defines a set of sub-TLVs that are nested within each 114 other. When the degree of nesting TLVs is 2 (a TLV is carried within 115 another TLV) the TLV carried within a TLV is called a sub-TLV. 116 Strictly speaking, when the degree of nesting is 3, a sub-sub-TLV is 117 carried within a sub-TLV that is itself carried within a TLV. For 118 the sake of terminology simplicity, a TLV carried within another TLV 119 is called a sub-TLV regardless of the degree of nesting. 121 1.1. Requirements Language 123 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 124 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 125 document are to be interpreted as described in [RFC2119]. 127 2. Terminology 129 The following terminology is used in this document. 131 ABR: IS-IS Area Border Router. Routers used to connect two IGP 132 areas. 134 AS: Autonomous System. 136 ASBR: Autonomous System Border Router. Router used to connect 137 together ASes of the same or different service providers via one 138 or more inter-AS links 140 BN: A boundary node is either an ABR in the context of inter-area 141 Traffic Engineering or an ASBR in the context of inter-AS Traffic 142 Engineering. 144 BND: Boundary Node Discovery 145 BRPC: Backward Recursive Path Computation 147 Domain: Any collection of network elements within a common sphere of 148 address management or path computational responsibility. Examples 149 of domains include Interior Gateway Protocol (IGP) areas and 150 Autonomous Systems (ASs). 152 H-PCE: Hierarchical PCE. 154 IGP: Interior Gateway Protocol. Either of the two routing 155 protocols, Open Shortest Path First (OSPF) or Intermediate System 156 to Intermediate System (IS-IS). 158 LSA: Link State Advertisement. 160 IS-IS: Intermediate System to Intermediate System. 162 PCE: Path Computation Element. An entity (component, application, 163 or network node) that is capable of computing a network path or 164 route based on a network graph and applying computational 165 constraints. 167 TLV: Type-Length-Variable data encoding. 169 3. Applications 171 Backward Recursive Path Computation (BRPC) procedure as defined in 172 [RFC5441], requires Path Computation Element (PCE) [RFC4655] to be 173 aware of the BNs for the inter-domain path computation. This 174 information would be either statically configured at PCE or learned 175 via some mechanism, as listed in Section 4. 177 In case of static configuration, as shown in the Figure 1, incase of 178 ISIS Backbone area(L2), configuration of BNs at PCE5 is extensive. 179 BRPC procedure guarantees a best path only if BNs are selected 180 correctly, any change in BNs at run time may lead to sub-optimal 181 path. Also Administrator need to configure ABR / ASBR ID in such a 182 way that it is reachable from all the domains, BND TLV can take care 183 of this automatically. 185 +--------------------------+ +--------------------------+ 186 | +------+| | +------+| 187 | Area1(L1) | PCE1 || | Area2(L1) | PCE2 || 188 | +--+---+| | +--+---+| 189 | | | | 190 | +---------------------+----------+--------------------+ | 191 | | +------+ +------+| |+------+ +------+ | | 192 | | | BN1 | | BN2 || || BN3 | | BN4 | | | 193 | | +--+---+ +--+---+| |+--+---+ +---+--+ | | 194 +----+----|-----------+----+ +---+-----------+----+-----+ 195 | | | | | | 196 | +-----------+-------+ +------+-----------+ | 197 | | | | 198 | | | | 199 | ++----++ | 200 | Backbone(L2) | PCE5 | | 201 | ++----++ | 202 | | | | 203 | | | | 204 | +-----------+-------+ +------+----------+ | 205 | | | | | | 206 | | | | | | 207 +----+----+-----------+----+ +---+----------+-----+-----+ 208 | | +--+---+ +--+---+| |+--+---+ +--+---+ | | 209 | | | BN5 | | BN6 || || BN7 | | BN8 | | | 210 | | +------+ +------+| |+------+ +------+ | | 211 | +---------------------+----------+--------------------+ | 212 | | | | 213 | +------+| | +------+| 214 | Area3(L1) | PCE3 || | Area4(L1) | PCE4 || 215 | +--+---+| | +--+---+| 216 +--------------------------+ +--------------------------+ 218 Figure 1: ISIS Area Topology 220 The problems with existing mechanism to discover Boundary nodes are 221 listed in Section 4. 223 Hierarchal PCE (H-PCE) [RFC6805] mechanim MAY require a parent PCE to 224 be aware of child domain's boundary node, child PCE in any case 225 should be aware of all its boundary nodes and can use mechnims as 226 described in this document. 228 4. Existing Mechanisms 230 4.1. ISIS 232 o As specified in [RFC1142] ABR/ASBR can be identified but not their 233 domain information. As stated in Section 5.2, Selection of 234 correct BN is based on domain and thus it is ineffective. 236 o Selection of ABR/ASBR based on ISIS Database is not a good idea, 237 first it requires PCE to look into ISIS core Database thus adding 238 to coupling, second it MAY require Border Gateway Protocol (BGP) 239 routes to be redistributed into ISIS which is also not a good 240 network design principle. 242 4.2. Inter-AS TE Link 244 o [RFC5316] specifies how to advertise TE properties of inter-AS 245 links; through which ASBR and remote AS can be discovered, but ABR 246 and their domain information cannot be discovered via above RFC. 248 o AS is made up of multiple Area, there maybe a need to clearly 249 identify a BN by combination of both AS number and Area-id. Refer 250 [DOMAIN-SEQ]. 252 4.3. ISIS Area Topology 254 o To uniquely identify an ISIS L1 area, an unique area Id MUST be 255 assigned. There is no other way to learn this information. BND 256 can be used to advertise this information. 258 5. Other Considerations 260 5.1. Static Configurations 262 A simple solution would be to configure BNs (ABR and ASBR) at PCE(s) 263 along with their domain information. As this information is fairly 264 static this could work in simple situations. But as PCE are being 265 used in bigger and multiple domains, any sort of static 266 configurations would put extra effort on the system administrator. 267 Selection of correct BNs is the core of any inter-domain path 268 computation procedure, we feel this information should be dynamically 269 learned and maintained. 271 5.2. Importance of Domain Information along with BNs 273 There are methods to learn BNs dynamically from IGP, but the 274 knowledge of neighboring-domains is not possible to obtain. Without 275 this the correct BN based on the domain-path can't be selected. 276 [RFC5441] mentions: 278 "Note that PCE(i) only considers the entry BNs of domain(i), i.e., 279 only the BNs that provide connectivity from domain(i-1). In other 280 words, the set BN-en(k,i) is only made of those BNs that provide 281 connectivity from domain (i-1) to domain(i). " 283 This selection of correct BNs providing connectivity between correct 284 domains cannot be made by the information obtained from IGP. Without 285 the correct selection we would not be following [RFC5441]. 287 5.3. Relationship to Domain-Sequence 289 [DOMAIN-SEQ] provides a standard representation of Domain Sequence in 290 all deployment scenarios. The Domain Information carried in the BN- 291 DOMAIN sub-tlv is same as the sub-objects inside the domain sequence. 293 6. Overview 295 6.1. Boundary Node (BN) Discovery Information 297 The BN discovery information is composed of: 299 o The BN location: an IPv4 and/or IPv6 address that is used to reach 300 the BN. It is RECOMMENDED to use an address that is always 301 reachable from all connected domains; 303 o The set of two or more Domain(s) into which the BN has 304 connectivity; 306 Changes in BN discovery information may occur as a result of BN 307 configuration update or domain status change. 309 6.2. Flooding Scope 311 The flooding scope for BN information advertised through IS-IS can be 312 a single L1 area, an L1 area and the L2 sub-domain, or the entire IS- 313 IS routing domain. 315 7. The IS-IS BND Sub-TLV 317 The IS-IS BND sub-TLV contains a non-ordered set of sub-TLVs. 319 The format of the IS-IS BND sub-TLV and its sub-TLVs is identical to 320 the TLV format used by the Traffic Engineering Extensions to IS-IS 321 [RFC5305]. That is, the TLV is comprised of 1 octet for the type, 1 322 octet specifying the TLV length, and a value field. The Length field 323 defines the length of the value portion in octets. 325 The IS-IS BND sub-TLV has the following format: 327 TYPE: To be assigned by IANA (suggested value 6) 328 LENGTH: Variable 329 VALUE: Set of sub-TLVs 331 Two sub-TLVs are defined: 333 Sub-TLV type Length Name 334 1 variable BN-ADDRESS sub-TLV 335 2 variable BN-DOMAIN sub-TLV 337 The BN-ADDRESS and BN-DOMAIN sub-TLVs MUST always be present within 338 the BND sub-TLV. 340 Any unrecognized sub-TLV MUST be silently ignored. 342 The BND sub-TLV is carried within an IS-IS CAPABILITY TLV defined in 343 [RFC4971]. 345 The following sub-sections describe the sub-TLVs. 347 7.1. BN-ADDRESS Sub-TLV 349 The BN-ADDRESS sub-TLV specifies an IP address that can be used to 350 reach the BN. It is RECOMMENDED to make use of an address that is 351 always reachable, provided the BN is alive and reachable. 353 The BN-ADDRESS sub-TLV is mandatory; it MUST be present within the 354 BND sub-TLV. It MAY appear twice, when the BN has both an IPv4 and 355 IPv6 address. It MUST NOT appear more than once for the same address 356 type. If it appears more than once for the same address type, only 357 the first occurrence is processed and any others MUST be ignored. 359 The BN-ADDRESS sub-TLV has the following format: 361 TYPE: 1 362 LENGTH: 5 for an IPv4 address or 17 for an IPv6 address. 363 VALUE: This comprises one octet indicating the address 364 -type and 4 or 16 octets encoding the IPv4 or 365 IPv6 address to be used to reach the BN. 367 Address-type: 368 1 IPv4 369 2 IPv6 371 7.2. BN-DOMAIN Sub-TLV 373 The BN-DOMAIN sub-TLV specifies a BN-Domain (area and/or AS) where 374 the BN has topology connectivity. 376 The BN-DOMAIN sub-TLV is mandatory; it MUST be present within the BND 377 TLV. 379 A BND sub-TLV MUST include two or more BN-DOMAIN sub-TLVs as the BN 380 has connectivity into multiple BN-Domains. 382 The BN-DOMAIN sub-TLV has the following format: 384 TYPE: 2 385 LENGTH: Variable 386 VALUE: This is composed of one octet indicating the 387 domain-type (area ID or AS Number) and a 388 variable length IS-IS area ID or a 32-bit AS 389 number, identifying a BN-Domain where the BN 390 has visibility and can compute paths. 392 Two domain types are defined: 394 1 Area ID 395 2 AS Number 397 The Area ID is the area address as defined in [ISO10589]. 399 When the AS number is coded in two octets, the AS Number field MUST 400 have its first two octets set to 0. 402 8. Elements of Procedure 404 The BND sub-TLV is advertised within an IS-IS Router Capability TLV 405 defined in [RFC4971]. As such, elements of procedures are inherited 406 from those defined in [RFC4971]. 408 The flooding scope is controlled by the S flag in the IS-IS Router 409 Capability TLV (see [RFC4971]). When the scope of the BND sub-TLV is 410 area local, it MUST be carried within an IS-IS Router Capability TLV 411 having the S bit cleared. When the scope of the BND sub-TLV is the 412 entire IS-IS routing domain, it MUST be carried within an IS-IS 413 Router Capability TLV having the S bit set. 415 Note that an L1L2 node may include a BND TLV in a Router Capability 416 TLV with the S bit cleared in both in its L1 and L2 LSPs. This 417 allows the flooding scope to be restricted to the L1 area and the L2 418 sub-domain. 420 When the BN function is deactivated, the IS-IS speaker MUST originate 421 a new IS-IS LSP that no longer includes the corresponding BND TLV. 423 The BN address (i.e., the address indicated within the BN-ADDRESS 424 sub-TLV) SHOULD be reachable via some prefixes advertised by IS-IS. 426 The BND sub-TLV information regarding a specific BN is only 427 considered current and useable when the router advertising this 428 information is itself reachable via IS-IS calculated paths at the 429 level of the LSP in which the BND sub-TLV appears. 431 A change in the state of a BN (activate, deactivate, domain change) 432 MUST result in a corresponding change in the BND sub-TLV information 433 advertised by an IS-IS router (inserted, removed, updated) in its 434 LSP. The way BNs determine the information they advertise, and how 435 that information is made available to IS-IS, is out of the scope of 436 this document. Some information may be configured and other 437 information may be automatically determined by ISIS. 439 A change in information in the BND sub-TLV MUST NOT trigger any SPF 440 computation at a receiving router. 442 9. Backward Compatibility 444 The BND TLV defined in this document does not introduce any 445 interoperability issues. 447 An IS-IS router not supporting the BND sub-TLV will just silently 448 ignore the sub-TLV as specified in [RFC4971]. 450 10. Impact on Network 452 The routers acting as BNs will originate LSP with BND Tlv; As there 453 are only few BNs exist in the network, the performance impact in 454 flooding is very less. 456 11. IANA Considerations 458 IANA has defined a registry for the sub-TLVs carried in the IS-IS 459 Router Capability TLV defined in [RFC4971]. IANA has assigned a new 460 sub-TLV codepoint for the BND sub-TLV carried within the Router 461 Capability TLV. 463 Value Sub-TLV References 464 ----- -------- ---------- 465 To be BND sub-TLV (this document) 466 assigned 467 by IANA 469 12. Security Considerations 471 This document defines IS-IS extensions for BN discovery within an 472 administrative domain. Hence the security of the BN discovery relies 473 on the security of IS-IS. 475 Mechanisms defined to ensure authenticity and integrity of IS-IS LSPs 476 [RFC5304] and their TLVs, can be used to secure the BND sub-TLV as 477 well. 479 IS-IS provides no encryption mechanism for protecting the privacy of 480 LSPs and, in particular, the privacy of the BN discovery information. 482 13. Manageability Considerations 484 TBD 486 14. Acknowledgments 488 We would like to thank Quintin Zhao, Daniel King, Adrian Ferral, 489 Suresh babu, Pradeep Shastry, Saravana Kumar, Srinivasan and 490 Venugopal reddy k for their useful comments and suggestions. 492 15. References 494 15.1. Normative References 496 [RFC1142] Oran, D., "OSI IS-IS Intra-domain Routing Protocol", RFC 497 1142, February 1990. 499 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 500 Requirement Levels", BCP 14, RFC 2119, March 1997. 502 [RFC4971] Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate 503 System to Intermediate System (IS-IS) Extensions for 504 Advertising Router Information", RFC 4971, July 2007. 506 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 507 Authentication", RFC 5304, October 2008. 509 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 510 Support of Inter-Autonomous System (AS) MPLS and GMPLS 511 Traffic Engineering", RFC 5316, December 2008. 513 [ISO10589] 514 ISO, "Intermediate system to Intermediate system routeing 515 information exchange protocol for use in conjunction with 516 the Protocol for providing the Connectionless-mode Network 517 Service (ISO 8473)", ISO/IEC 10589:2002, Nov 2002. 519 15.2. Informative References 521 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 522 Element (PCE)-Based Architecture", RFC 4655, August 2006. 524 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 525 Engineering", RFC 5305, October 2008. 527 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 528 Backward-Recursive PCE-Based Computation (BRPC) Procedure 529 to Compute Shortest Constrained Inter-Domain Traffic 530 Engineering Label Switched Paths", RFC 5441, April 2009. 532 [RFC6805] King, D. and A. Farrel, "The Application of the Path 533 Computation Element Architecture to the Determination of a 534 Sequence of Domains in MPLS and GMPLS", RFC 6805, November 535 2012. 537 [DOMAIN-SEQ] 538 Dhody, D., Palle, U., and R. Casellas, "Standard 539 Representation Of Domain Sequence (draft-ietf-pce-pcep- 540 domain-sequence-05)", July 2014. 542 Authors' Addresses 544 Dhruv Dhody 545 Huawei Technologies India Pvt Ltd 546 Leela Palace 547 Bangalore, Karnataka 560008 548 India 550 EMail: dhruv.ietf@gmail.com 552 Udayasree Palle 553 Huawei Technologies India Pvt Ltd 554 Leela Palace 555 Bangalore, Karnataka 560008 556 India 558 EMail: udayasree.palle@huawei.com