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Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: A change in PCED information MUST not trigger any SPF computation at a receiving router. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (May 2007) is 5484 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) -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO' ** Obsolete normative reference: RFC 3784 (Obsoleted by RFC 5305) == Outdated reference: draft-ietf-isis-caps has been published as RFC 4971 ** Obsolete normative reference: RFC 3567 (Obsoleted by RFC 5304) -- No information found for draft-ietf-pce-disco-proto-ospf - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'PCED-OSPF' == Outdated reference: draft-ietf-pce-pcep has been published as RFC 5440 Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J.L. Le Roux (Editor) 3 Internet Draft France Telecom 4 Intended Status: Standards Track 5 Expires: November 2007 J.P. Vasseur (Editor) 6 Cisco System Inc. 8 Yuichi Ikejiri 9 NTT Communications 11 Raymond Zhang 12 BT Infonet 14 May 2007 16 IS-IS protocol extensions for Path Computation Element (PCE) Discovery 18 draft-ietf-pce-disco-proto-isis-05.txt 20 Status of this Memo 22 By submitting this Internet-Draft, each author represents that any 23 applicable patent or other IPR claims of which he or she is aware 24 have been or will be disclosed, and any of which he or she becomes 25 aware will be disclosed, in accordance with Section 6 of BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF), its areas, and its working groups. Note that 29 other groups may also distribute working documents as Internet- 30 Drafts. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 The list of current Internet-Drafts can be accessed at 38 http://www.ietf.org/ietf/1id-abstracts.txt. 40 The list of Internet-Draft Shadow Directories can be accessed at 41 http://www.ietf.org/shadow.html. 43 Copyright Notice 45 Copyright (C) The IETF Trust (2007). All rights reserved. 47 Abstract 49 There are various circumstances where it is highly desirable for a 50 Path Computation Client (PCC) to be able to dynamically and 51 automatically discover a set of Path Computation Elements (PCE), 52 along with some information that can be used for PCE selection. When 53 the PCE is a Label Switching Router (LSR) participating in the 54 Interior Gateway Protocol (IGP), or even a server participating 55 passively in the IGP, a simple and efficient way to discover PCEs 56 consists of using IGP flooding. For that purpose this document 57 defines extensions to the Intermediate System to Intermediate System 58 (IS-IS) routing protocol for the advertisement of PCE Discovery 59 information within an IS-IS area or within the entire IS-IS routing 60 domain. 62 Conventions used in this document 64 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 65 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 66 document are to be interpreted as described in [RFC2119]. 68 Table of Contents 70 1. Terminology.................................................3 71 2. Introduction................................................4 72 3. Overview....................................................5 73 3.1. PCE Information.............................................5 74 3.1.1. PCE Discovery Information...................................5 75 3.1.2. PCE Congestion Information..................................6 76 3.2. Flooding Scope..............................................6 77 4. IS-IS Extensions............................................7 78 4.1. The IS-IS PCED Sub-TLV......................................7 79 4.1.1. PCE-ADDRESS Sub-TLV.........................................8 80 4.1.2. The PATH-SCOPE Sub-TLV......................................8 81 4.1.3. PCE-DOMAIN Sub-TLV.........................................10 82 4.1.4. NEIG-PCE-DOMAIN Sub-TLV....................................11 83 4.1.5. PCE-CAP-FLAGS Sub-TLV......................................11 84 4.1.6. The CONGESTION Sub-TLV.....................................12 85 5. Elements of Procedure......................................13 86 5.1.1. CONGESTION Sub-TLV Specific Procedures.....................14 87 6. Backward Compatibility.....................................14 88 7. IANA Considerations........................................15 89 7.1. IS-IS Sub-TLV..............................................15 90 7.2. PCED Sub-TLVs registry.....................................15 91 8. Security Considerations....................................15 92 9. Manageability Considerations...............................16 93 9.1. Control of Policy and Functions............................16 94 9.2. Information and Data Model.................................16 95 9.3. Liveness Detection and Monitoring..........................16 96 9.4. Verify Correct Operations..................................16 97 9.5. Requirements on Other Protocols and Functional 98 Components...............................................16 99 9.6. Impact on Network Operations...............................17 100 10. Acknowledgments............................................17 101 11. References.................................................17 102 11.1. Normative References.......................................17 103 11.2. Informative References.....................................18 104 12. Editors' Addresses:........................................18 105 13. Contributors' Adresses:....................................18 106 14. Intellectual Property Statement............................19 108 1. Terminology 110 Terminology used in this document 112 AS: Autonomous System. 114 IGP: Interior Gateway Protocol. Either of the two routing 115 protocols Open Shortest Path First (OSPF) or Intermediate System 116 to Intermediate system (IS-IS). 118 Intra-area TE LSP: A TE LSP whose path does not cross IGP area 119 boundaries. 121 Intra-AS TE LSP: A TE LSP whose path does not cross AS boundaries. 123 Inter-area TE LSP: A TE LSP whose path transits two or 124 more IGP areas. That is a TE-LSP that crosses at least one IGP 125 area boundary. 127 Inter-AS TE LSP: A TE LSP whose path transits two or more 128 ASes or sub-ASes (BGP confederations). That is a TE-LSP that 129 crosses at least one AS boundary. 131 IS-IS LSP: Link State PDU 133 LSR: Label Switching Router. 135 PCC: Path Computation Client: Any client application requesting a 136 path computation to be performed by a Path Computation Element. 138 PCE: Path Computation Element: An entity (component, application, 139 or network node) that is capable of computing a network path or 140 route based on a network graph, and applying computational 141 constraints. 143 PCE-Domain: In a PCE context this refers to any collection of 144 network elements within a common sphere of address management or 145 path computational responsibility (referred to as "domain" in 146 [RFC4655]). Examples of PCE-Domains include IGP areas and ASes. 148 This should be distinguished from an IS-IS routing domain as 149 defined by [ISO]. 151 PCEP: Path Computation Element communication Protocol. 153 TE LSP: Traffic Engineered Label Switched Path. 155 2. Introduction 157 [RFC4655] describes the motivations and architecture for a Path 158 Computation Element (PCE)-based path computation model for Multi 159 Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic 160 Engineered Label Switched Paths (TE-LSPs). The model allows for the 161 separation of the PCE from a Path Computation Client (PCC) (also 162 referred to as a non co-located PCE) and allows for cooperation 163 between PCEs. This relies on a communication protocol between PCC and 164 PCE, and between PCEs. The requirements for such a communication 165 protocol can be found in [RFC4657] and the communication protocol is 166 defined in [PCEP]. 168 The PCE architecture requires that a PCC be aware of the location of 169 one or more PCEs in its domain, and also potentially of some PCEs in 170 other domains, e.g. in case of inter-domain TE LSP computation. 172 A network may contain a large number of PCEs with potentially 173 distinct capabilities. In such a context it is highly desirable to 174 have a mechanism for automatic and dynamic PCE discovery, which 175 allows PCCs to automatically discover a set of PCEs, along with 176 additional information about each PCE that may be required for the 177 PCC to perform PCE selection. Additionally, it is valuable for a PCC 178 to dynamically detect new PCEs or any modification of the PCE 179 information. Detailed requirements for such a PCE discovery mechanism 180 are provided in [RFC4674]. 182 Moreover, it may also be useful to discover when a PCE experiences 183 processing congestion and when it exits such a state, in order for 184 the PCCs to take some appropriate actions (e.g. redirect their 185 requests to another PCE). Note that the PCE selection algorithm 186 applied by a PCC is out of the scope of this document. 188 When PCCs are LSRs participating in the IGP (OSPF, IS-IS), and PCEs 189 are either LSRs or servers also participating in the IGP, an 190 effective mechanism for PCE discovery within an IGP routing domain 191 consists of utilizing IGP advertisements. 193 This document defines IS-IS extensions to allow a PCE in an IS-IS 194 routing domain to advertise its location along with some information 195 useful to a PCC for PCE selection, so as to satisfy dynamic PCE 196 discovery requirements set forth in [RFC4674]. This document also 197 defines extensions allowing a PCE in an IS-IS routing domain to 198 advertise its processing congestion state. 200 Generic capability advertisement mechanisms for IS-IS are defined in 201 [IS-IS-CAP]. These allow a router to advertise its capabilities 202 within an IS-IS area or an entire IS-IS routing domain. This document 203 leverages this generic capability advertisement mechanism to fully 204 satisfy the aforementioned dynamic PCE discovery requirements. 206 This document defines a new sub-TLV (named PCE Discovery (PCED) to be 207 carried within the IS-IS Router Capability TLV ([IS-IS-CAP]). 209 The PCE information advertised is detailed in section 3. Protocol 210 extensions and procedures are defined in section 4 and 5. 212 This document does not define any new IS-IS elements of procedure. 213 The procedures defined in [IS-IS-CAP] MUST be used. 215 The IS-IS extensions defined in this document allow for PCE discovery 216 within an IS-IS Routing domain. Solutions for PCE discovery across AS 217 boundaries are beyond the scope of this document, and for further 218 study. 220 This document defines a set of sub-TLVs that are nested within each 221 other. When the degree of nesting TLVs is 2 (a TLV is carried within 222 another TLV) the TLV carried within a TLV is called a sub-TLV. 223 Strictly speaking, when the degree of nesting is 3, a subsub-TLV is 224 carried within a sub-TLV that is itself carried within a TLV. For the 225 sake of terminology simplicity, we refer to sub-TLV, a TLV carried 226 within a TLV regardless of the degree of nesting. 228 3. Overview 230 3.1. PCE Information 232 The PCE information advertised via IS-IS falls into two categories: 233 PCE Discovery information and PCE Congestion information. 235 3.1.1. PCE Discovery Information 237 The PCE Discovery information is comprised of: 239 - The PCE location: an IPv4 and/or IPv6 address that is used to reach 240 the PCE. It is RECOMMENDED to use an address that is always 241 reachable; 243 - The PCE path computation scope (i.e. inter-area, inter-AS, inter- 244 layer); 246 - The set of one or more PCE-Domain(s) into which the PCE has 247 visibility and can compute paths; 249 - The set of one or more neighbor PCE-Domain(s) towards which a PCE 250 can compute paths; 252 - A set of communication capabilities (e.g. support for request 253 prioritization) and path computation specific capabilities 254 (e.g. supported constraints). 256 Optional elements to describe more complex capabilities may also be 257 advertised. 259 PCE Discovery information is by nature fairly static and does not 260 change with PCE activity. Changes in PCE Discovery information may 261 occur as a result of PCE configuration updates, PCE 262 deployment/activation, PCE deactivation/suppression, or PCE failure. 263 Hence, this information is not expected to change frequently. 265 3.1.2. PCE Congestion Information 267 The PCE Congestion information is optional and can be used to report 268 a PCE's processing congestion state along with an estimated 269 congestion duration. This is dynamic information, which may change 270 with PCE activity. 272 Procedures for a PCE to move from a processing congestion state to a 273 non-congestion state are beyond the scope of this document, but the 274 rate at which a PCE Status change is advertised MUST NOT impact by 275 any means the IGP scalability. Particular attention should be given 276 on procedures to avoid state oscillations. 278 3.2. Flooding Scope 280 The flooding scope for PCE information advertised through IS-IS can 281 be a single L1 area, a L1 area and the L2 sub-domain, or the entire 282 IS-IS routing domain. 284 4. IS-IS Extensions 286 4.1. The IS-IS PCED Sub-TLV 288 The IS-IS PCED sub-TLV is made of a set of non ordered sub-TLVs. 290 The format of the IS-IS PCED sub-TLV and its sub-TLVs is identical to 291 the TLV format used by the Traffic Engineering Extensions to IS-IS 292 [RFC3784]. That is, the TLV is composed of 1 octet for the type, 1 293 octet specifying the TLV length, and a value field. The Length field 294 defines the length of the value portion in bytes. 296 The IS-IS PCED sub-TLV has the following format: 298 TYPE: To be assigned by IANA (suggested value = 5) 299 LENGTH: Variable 300 VALUE: set of sub-TLVs 302 Sub-TLVs types are under IANA control. 304 Currently six sub-TLVs are defined (suggested type values to be 305 assigned by IANA): 307 Sub-TLV type Length Name 309 1 variable PCE-ADDRESS sub-TLV 310 2 3 PATH-SCOPE sub-TLV 311 3 variable PCE-DOMAIN sub-TLV 312 4 variable NEIG-PCE-DOMAIN sub-TLV 313 5 variable PCE-CAP-FLAGS sub-TLV 314 6 1 CONGESTION sub-TLV 316 The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within 317 the PCED sub-TLV. 319 The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They 320 MAY be present in the PCED sub-TLV to facilitate selection of inter- 321 domain PCEs. 323 The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED 324 sub-TLV to facilitate the PCE selection process. 326 The CONGESTION sub-TLV is optional and MAY be present in the PCED 327 sub-TLV, to indicate a PCE's processing congestion state. 329 Any non recognized sub-TLV MUST be silently ignored. 331 Additional sub-TLVs could be added in the future to advertise 332 additional PCE information. 334 The PCED sub-TLV is carried within an IS-IS CAPABILITY TLV defined in 335 [IS-IS-CAP]. 337 The following sub-sections describe the sub-TLVs which may be carried 338 within the PCED sub-TLV. 340 4.1.1. PCE-ADDRESS Sub-TLV 342 The PCE-ADDRESS sub-TLV specifies the IP address that can be 343 used to reach the PCE. It is RECOMMENDED to make use of an address 344 that is always reachable, provided the PCE is alive. 346 The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the 347 PCED sub-TLV. It MAY appear twice, when the PCE has both an IPv4 and 348 IPv6 address. It MUST NOT appear more than once for the same address 349 type. 351 The PCE-ADDRESS sub-TLV has the following format: 353 TYPE: To be assigned by IANA (Suggested value =1) 354 LENGTH: 5 for IPv4 address and 17 for IPv6 address 355 VALUE: This comprises one octet indicating the address-type and 4 356 or 16 bytes encoding the IPv4 or IPv6 address to be used 357 to reach the PCE. 359 Address-type: 360 1 IPv4 361 2 IPv6 363 4.1.2. The PATH-SCOPE Sub-TLV 365 The PATH-SCOPE sub-TLV indicates the PCE path computation scope, 366 which refers to the PCE's ability to compute or take part in the 367 computation of intra-area, inter-area, inter-AS, or inter-layer_TE 368 LSP(s). 370 The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the 371 PCED sub-TLV. There MUST be exactly one instance of the PATH-SCOPE 372 sub-TLV within each PCED sub-TLV. 374 The PATH-SCOPE sub-TLV contains a set of bit flags indicating the 375 supported path scopes, and four fields indicating PCE preferences. 377 The PATH-SCOPE sub-TLV has the following format: 379 TYPE: To be assigned by IANA (Suggested value =2) 380 LENGTH: 3 381 VALUE: This comprises a one-byte flags field where flag 382 represents a supported path scope, followed by a 2-bytes 383 preferences field indicating PCE preferences. 385 Here is the structure of the bits flag: 387 +-+-+-+-+-+-+-+-+ 388 |0|1|2|3|4|5|Res| 389 +-+-+-+-+-+-+-+-+ 391 Bit Path Scope 393 0 L bit: Can compute intra-area path 394 1 R bit: Can act as PCE for inter-area TE LSP computation 395 2 Rd bit: Can act as a default PCE for inter-area TE LSP 396 computation 397 3 S bit: Can act as PCE for inter-AS TE LSP computation 398 4 Sd bit: Can act as a default PCE for inter-AS TE LSPs 399 computation 400 5 Y bit: Can compute or take part into the computation of 401 paths across layers 402 6-7 Reserved for future usage. 404 Here is the structure of the preferences field 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 |PrefL|PrefR|PrefS|PrefY| Res | 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 410 Res: Reserved for future usage. 412 Pref-L field: PCE's preference for intra-area TE LSPs computation. 414 Pref-R field: PCE's preference for inter-area TE LSPs computation. 416 Pref-S field: PCE's preference for inter-AS TE LSPs computation. 418 Pref-Y field: PCE's preference for inter-layer TE LSPs computation. 420 Res: Reserved for future usage. 422 The L, R, S, and Y bits are set when the PCE can act as a PCE for 423 intra-area, inter-area, inter-AS or inter-layer TE LSPs computation 424 respectively. These bits are non-exclusive. 426 When set the Rd bit indicates that the PCE can act as a default PCE 427 for inter-area TE LSP computation (that is the PCE can compute a path 428 towards any neighbor area). Similarly, when set, the Sd bit indicates 429 that the PCE can act as a default PCE for inter-AS TE LSP computation 430 (the PCE can compute a path towards any neighbor AS). 432 When the Rd and Sd bit are set, the PCED sub-TLV MUST NOT contain any 433 NEIG-PCE-DOMAIN sub-TLV (see 4.1.4). 435 When the R/S bit is cleared, the Rd/Sd bit SHOULD be cleared and MUST 436 be ignored. 438 The PrefL, PrefR, PrefS and PrefY fields are each three bits long and 439 allow the PCE to specify a preference for each computation scope, 440 where 7 reflects the highest preference. Such preference can be used 441 for weighted load balancing of requests. An operator may decide to 442 configure a preference for each computation scope to each PCE so as 443 to balance the path computation load among them. The algorithms used 444 by a PCC to balance its path computation requests according to such 445 PCE preference are out of the scope of this document and is a matter 446 for local or network wide policy. The same or distinct preferences 447 may be used for each scopes. For instance an operator that wants a 448 PCE capable of both inter-area and inter-AS computation to be used 449 preferably for inter-AS computation may configure a PrefS higher than 450 the PrefR. 452 When the L bit, R bit, S bit or Y bit are cleared the PrefL, PrefR, 453 PrefS, PrefY fields SHOULD respectively be set to 0 and MUST be 454 ignored. 456 Both reserved fields SHOULD be set to zero on transmission and MUST 457 be ignored on receipt. 459 4.1.3. PCE-DOMAIN Sub-TLV 461 The PCE-DOMAIN sub-TLV specifies a PCE-Domain (areas and/or ASes) 462 where the PCE has topology visibility and through which the PCE can 463 compute paths. 465 The PCE-DOMAIN sub-TLV MAY be present when PCE-Domains cannot be 466 inferred by other IGP information, for instance when the PCE is 467 inter-domain capable (i.e. when the R bit or S bit is set) and the 468 flooding scope is the entire routing domain (see section 5 for a 469 discussion of how the flooding scope is set and interpreted). 471 A PCED sub-TLV MAY include multiple PCE-DOMAIN sub-TLVs when the PCE 472 has visibility in multiple PCE-Domains. 474 The PCE-DOMAIN sub-TLV has the following format: 476 TYPE: To be assigned by IANA (Suggested value =3) 477 LENGTH: Variable 478 VALUE: This comprises one octet indicating the domain-type (area ID 479 or AS Number) and a variable length IS-IS area ID or a 32 bits AS 480 number, identifying a PCE-domain where the PCE has visibility. 482 Two domain types are defined: 483 1 Area ID 484 2 AS Number 486 The Area ID is the area address as defined in [ISO]. 488 When coded in two bytes (which is the current defined format as the 489 time of writing this document), the AS Number field MUST have its 490 left two bytes set to 0. 492 4.1.4. NEIG-PCE-DOMAIN Sub-TLV 494 The NEIG-PCE-DOMAIN sub-TLV specifies a neighbour PCE-domain (area, 495 AS) toward which a PCE can compute paths. It means that the PCE can 496 take part in the computation of inter-domain TE LSPs whose path 497 transits this neighbour PCE-domain. 499 A PCED sub-TLV MAY include several NEIG-PCE-DOMAIN sub-TLVs when the 500 PCE can compute paths towards several neighbour PCE-domains. 502 The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN 503 sub-TLV: 505 TYPE: To be assigned by IANA (Suggested value =4) 506 LENGTH: Variable 507 VALUE: This comprises one octet indicating the domain-type (area ID 508 or AS Number) and a variable length IS-IS area ID or a 32 bits AS 509 number, identifying a PCE-domain towards which the PCE can compute 510 paths. 512 Two domain types are defined: 513 1 Area ID 514 2 AS Number 516 The Area ID is the area address as defined in [ISO]. 518 When coded in two bytes (which is the current defined format as the 519 time of writing this document), the AS Number field MUST have its 520 left two bytes set to 0. 522 The NEIG-PCE-DOMAIN sub-TLV MUST be present if the R bit is set and 523 the Rd bit is cleared, and/or, if the S bit is set and the Sd bit is 524 cleared. 526 4.1.5. PCE-CAP-FLAGS Sub-TLV 528 The PCE-CAP-FLAGs sub-TLV is an optional sub-TLV used to indicate 529 PCEP related capabilities. It MAY be present within the PCED sub-TLV. 530 It MUST NOT be present more than once. 532 The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array 533 of units of 32 bit flags numbered from the most significant as bit 534 zero, where each bit represents one PCE capability. 536 The PCE-CAP-FLAGS sub-TLV has the following format: 538 TYPE: To be assigned by IANA (Suggested value =4) 539 LENGTH: Multiple of 4 540 VALUE: This contains an array of units of 32 bit flags numbered 541 from the most significant as bit zero, where each bit 542 represents one PCE capability. 544 The PCE capability registry is managed by IANA, it is common 545 with OSPF and defined in [PCED-OSPF]. 547 Reserved bits SHOULD be set to zero on transmission and MUST be 548 ignored on receipt. 550 4.1.6. The CONGESTION Sub-TLV 552 The CONGESTION sub-TLV is used to indicate that a PCE is experiencing 553 a processing congestion state and may optionally include expected PCE 554 congestion duration. 555 The CONGESTION sub-TLV is optional, it MAY be carried within the PCED 556 sub-TLV. It MUST NOT be present more than once. 558 The format of the CONGESTION sub-TLV is as follows: 560 TYPE: To be assigned by IANA (Suggested value =6) 561 LENGTH: 3 562 VALUE: This comprises a one byte of bit flags indicating the 563 congestion status, followed by a 2-bytes field indicating the 564 congestion duration. 566 Here is the TLV structure 568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 569 |C| Reserved| Congestion Duration | 570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 Value 574 -C bit: When set this indicates that the PCE is experiencing 575 congestion and cannot accept any new request. When 576 cleared this indicates that the PCE is not 577 experiencing congestion and can accept new requests. 579 -Congestion Duration: 2-bytes, the estimated PCE congestion 580 duration in seconds. 582 When C is set and the Congestion Duration field is equal to 0, this 583 means that the Congestion Duration is unknown. 585 When C is cleared the Congestion Duration SHOULD be set to 0 and MUST 586 be ignored. 588 5. Elements of Procedure 590 The PCED sub-TLV is advertised within an IS-IS Router Capability TLV 591 defined in [IS-IS-CAP]. As such, elements of procedures are inherited 592 from those defined in [IS-IS-CAP]. 594 The flooding scope is controlled by the S flag in the IS-IS Router 595 Capability TLV (see [IS-IS-CAP]). When the scope of the PCED sub-TLV 596 is area local it MUST be carried within an IS-IS Router Capability 597 TLV having the S bit cleared. When the scope of the PCED sub-TLV is 598 the entire IS-IS routing domain, it MUST be carried within an IS-IS 599 Router Capability TLV having the S bit set. Note that when only the L 600 bit of the PATH-SCOPE sub-TLV is set, the flooding scope MUST be area 601 local. 603 Note that a L1L2 node may include both in its L1 and L2 LSPs a PCED 604 TLV in a Router Capability TLV with the S bit cleared. This allows 605 restricting the flooding scope to the L1 area and the L2 sub-domain. 607 An IS-IS router MUST originate a new IS-IS LSP whenever there is a 608 change in a PCED TLV associated with a PCE it advertises. 610 When a PCE is deactivated, the IS-IS Router advertising this PCE MUST 611 originate a new IS-IS LSP that does no longer include the 612 corresponding PCED TLV. 614 The PCE address(s), i.e. the address(s) indicated within the PCE 615 ADDRESS sub-TLV, must be reachable via some prefix(es) advertised by 616 IS-IS; this allows speeding up the detection of a PCE failure. Note 617 that when the PCE address is no longer reachable, this means that the 618 PCE node has failed or has been torn down, or that there is no longer 619 IP connectivity to the PCE node. 621 The PCED sub-TLV is OPTIONAL. When an IS-IS LSP does not contain any 622 PCED TLV, this means that the PCE information of that node is 623 unknown. 625 A change in PCED information MUST not trigger any SPF computation at 626 a receiving router. 628 The way PCEs determine the information they advertise is out of the 629 scope of this document. Some information may be configured (e.g., 630 address, preferences, scope) and other information may be 631 automatically determined by the PCE (e.g. areas of visibility). 633 5.1.1. CONGESTION Sub-TLV Specific Procedures 635 When a PCE enters into a processing congestion state, the conditions 636 of which are implementation dependent, a new IS-IS LSP with a 637 CONGESTION sub-TLV with the C bit set and optionally a non-null 638 expected congestion duration MAY be generated. 640 When a PCE exists from the processing congestion state, the 641 conditions of which are implementation dependent, two cases are 642 considered: 643 - If the congestion duration in the previously originated 644 CONGESTION sub-TLV was null, a CONGESTION sub-TLV with the C bit 645 cleared SHOULD be generated; 646 - If the congestion duration in the previously originated 647 CONGESTION sub-TLV was non null, a CONGESTION sub-TLV with the C bit 648 cleared MAY be generated. Note that in some particular cases it may 649 be desired to originate a CONGESTION sub-TLV with the C bit cleared 650 if the congestion duration was over estimated. 652 The congestion duration allows a reduction in the amount of IS-IS 653 flooding, as only uncongested-to-congested state transitions are 654 advertised. 656 An IS-IS implementation SHOULD support an appropriate dampening 657 algorithm so as to dampen flooding of PCE Congestion information in 658 order to not impact the IS-IS scalability. It is RECOMMENDED to 659 introduce some hysteresis for congestion state transition, so as to 660 avoid state oscillations that may impact IS-IS performance. For 661 instance two thresholds MAY be configured: a resource congestion 662 upper-threshold and a resource congestion lower-threshold. An LSR 663 enters the congested state when the CPU load reaches the upper 664 threshold and leaves the congested state when the CPU load goes under 665 the lower threshold. 667 Upon receipt of an updated CONGESTION sub-TLV a PCC should take 668 appropriate actions. In particular, the PCC SHOULD stop sending 669 requests to a congested PCE, and SHOULD gradually start sending again 670 requests to a PCE that is no longer congested. 672 6. Backward Compatibility 674 The PCED sub-TLV defined in this document does not introduce any 675 interoperability issues. 677 An IS-IS router not supporting the PCED sub-TLV will just silently 678 ignore the TLV as specified in [IS-IS-CAP]. 680 7. IANA Considerations 682 7.1. IS-IS Sub-TLV 684 Once a registry for the IS-IS Router Capability sub-TLVs, defined in 685 [IS-IS-CAP] has been assigned, IANA will assign a new sub-TLV code- 686 point for the PCED sub-TLV carried within the Router Capability TLV. 688 Value Sub-TLV References 689 ----- -------- ---------- 690 5 PCED sub-TLV (this document) 692 7.2. PCED Sub-TLVs Registry 694 The PCED sub-TLV referenced above is constructed from sub-TLVs. Each 695 sub-TLV includes a 8-bit type identifier. 697 The IANA is requested to create a new sub-registry of the IS-IS 698 Router Capability sub-TLVs registry, named the "PCED sub-TLVs" 699 registry, and manage sub-TLV type identifiers as follows: 701 - sub-TLV Type 702 - sub-TLV Name 703 - Reference 705 This document defines five sub-TLVs as follows (suggested values): 707 Sub-TLV Sub-TLV 708 Type Name References 709 ----- -------- ---------- 710 1 PCE-ADDRESS This document 711 2 PATH-SCOPE This document 712 3 PCE-DOMAIN This document 713 4 NEIG-PCE-DOMAIN This document 714 5 PCE-CAP-FLAGS This document 715 6 CONGESTION This document 717 New sub-TLV type values may be allocated only by an IETF Consensus 718 action. 720 8. Security Considerations 722 This document defines IS-IS extensions for PCE discovery within an 723 administrative domain. Hence the security of the PCE discovery relies 724 on the security of IS-IS. 726 Mechanisms defined to ensure authenticity and integrity of IS-IS LSPs 727 [RFC3567], and their TLVs, can be used to secure the PCED sub-TLV as 728 well. 730 IS-IS provides no mechanism for protecting the privacy of LSPs, and 731 in particular the privacy of the PCE discovery information. 733 9. Manageability Considerations 735 Manageability considerations for PCE Discovery are addressed in 736 section 4.10 of [RFC4674]. 738 9.1. Control of Policy and Functions 740 Requirements on the configuration of PCE discovery parameters on PCCs 741 and PCEs are discussed in section 4.10.1 of [RFC4674]. 743 Particularly, a PCE implementation SHOULD allow configuring the 744 following parameters on the PCE: 745 -The PCE IPv4/IPv6 address(es) (see section 4.1.1) 746 -The PCE Scope, including the inter-domain functions (inter- 747 area, inter-AS, inter-layer), the preferences, and whether the 748 PCE can act as default PCE (see section 4.1.2) 749 -The PCE domains (see section 4.1.3) 750 -The neighbour PCE domains (see section 4.1.4) 751 -The PCE capabilities (see section 4.1.5) 753 9.2. Information and Data Model 755 A MIB module for PCE Discovery is defined in [PCED-MIB]. 757 9.3. Liveness Detection and Monitoring 759 PCE Discovery Protocol liveness detection relies upon IS-IS liveness 760 detection. IS-IS already includes a liveness detection mechanism 761 (Hello PDUs), and PCE discovery does not require additional 762 capabilities. 764 Procedures defined in section 5.1 allow a PCC detecting when a PCE 765 has been deactivated, or is no longer reachable. 767 9.4. Verify Correct Operations 769 The correlation of information advertised against information 770 received can be achieved by comparing the PCED information in the PCC 771 and in the PCE, which is stored in the PCED MIB [PCED-MIB]. The 772 number of dropped, corrupt, and rejected information elements are 773 stored in the PCED MIB. 775 9.5. Requirements on Other Protocols and Functional Components 777 The IS-IS extensions defined in this documents do not imply any 778 requirement on other protocols. 780 9.6. Impact on Network Operations 782 Frequent changes in PCE information, and particularly in PCE 783 congestion information, may have a significant impact on IS-IS and 784 might destabilize the operation of the network by causing the PCCs to 785 swap between PCEs. 787 As discussed in section 5.1, a PCE implementation SHOULD support an 788 appropriate dampening algorithm so as to dampen IS-IS flooding in 789 order to not impact the IS-IS scalability. 791 Also, as discussed in section 4.10.4 of [RFC4674], it MUST be 792 possible to apply at least the following controls: 794 - Configurable limit on the rate of announcement of changed 795 parameters at a PCE. 796 - Control of the impact on PCCs such as through discovery messages 797 rate-limiting. 798 - Configurable control of triggers that cause a PCC to swap to 799 another PCE. 801 10. Acknowledgments 803 We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike 804 Shand and Lou Berger for their useful comments and suggestions. 806 11. References 808 11.1. Normative References 810 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 811 Requirement Levels", BCP 14, RFC 2119, March 1997. 813 [ISO] "Intermediate System to Intermediate System Intra-Domain 814 Routeing Exchange Protocol for use in Conjunction with the 815 Protocol for Providing the Connectionless-mode Network 816 Service (ISO 8473)", ISO DP 10589, February 1990. 818 [RFC3784] Li, T., Smit, H., "IS-IS extensions for Traffic 819 Engineering", RFC 3784, June 2004. 821 [IS-IS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising 822 router information", draft-ietf-isis-caps, work in 823 progress. 825 [RFC3567] Li, T. and R. Atkinson, "Intermediate System to 826 Intermediate System (IS-IS) Cryptographic Authentication", 827 RFC 3567, July 2003. 829 [PCED-OSPF] Le Roux, Vasseur, et al. "OSPF protocol extensions for 830 Path Computation Element (PCE) Discovery", draft-ietf- 831 pce-disco-proto-ospf, work in progress. 833 11.2. Informative References 835 [RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation 836 Element (PCE)-based Architecture", RFC4655, August 2006. 838 [RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic 839 Requirements", RFC4657, September 2006. 841 [RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery", 842 RFC4674, October 2006. 844 [PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE) 845 communication Protocol (PCEP) - Version 1", draft-ietf-pce- 846 pcep, work in progress. 848 [PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path 849 Computation Element Discovery", draft-ietf-pce-disc-mib, 850 work in progress. 852 12. Editors' Addresses: 854 Jean-Louis Le Roux (Editor) 855 France Telecom 856 2, avenue Pierre-Marzin 857 22307 Lannion Cedex 858 FRANCE 859 Email: jeanlouis.leroux@orange-ftgroup.com 861 Jean-Philippe Vasseur (Editor) 862 Cisco Systems, Inc. 863 1414 Massachusetts avenue 864 Boxborough , MA - 01719 865 USA 866 Email: jpv@cisco.com 868 13. Contributors' Adresses: 870 Yuichi Ikejiri 871 NTT Communications Corporation 872 1-1-6, Uchisaiwai-cho, Chiyoda-ku 873 Tokyo 100-8019 874 JAPAN 875 Email: y.ikejiri@ntt.com 876 Raymond Zhang 877 BT Infonet 878 2160 E. Grand Ave. 879 El Segundo, CA 90025 880 USA 881 Email: raymond_zhang@bt-infonet.com 883 14. 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