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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Networking Working Group JP. Vasseur, Ed. 2 Internet-Draft Cisco Systems, Inc 3 Intended status: Standards Track JL. Le Roux 4 Expires: April 21, 2007 France Telecom 5 A. Ayyangar 6 Nuova Systems 7 E. Oki 8 NTT 9 A. Atlas 10 Google 11 A. Dolganow 12 Alcatel 13 Y. Ikejiri 14 NTT Communications Corporation 15 K. Kumaki 16 KDDI Corporation 17 October 18, 2006 19 Path Computation Element (PCE) communication Protocol (PCEP) - Version 1 20 draft-ietf-pce-pcep-03.txt 22 Status of this Memo 24 By submitting this Internet-Draft, each author represents that any 25 applicable patent or other IPR claims of which he or she is aware 26 have been or will be disclosed, and any of which he or she becomes 27 aware will be disclosed, in accordance with Section 6 of BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF), its areas, and its working groups. Note that 31 other groups may also distribute working documents as Internet- 32 Drafts. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 The list of current Internet-Drafts can be accessed at 40 http://www.ietf.org/ietf/1id-abstracts.txt. 42 The list of Internet-Draft Shadow Directories can be accessed at 43 http://www.ietf.org/shadow.html. 45 This Internet-Draft will expire on April 21, 2007. 47 Copyright Notice 48 Copyright (C) The Internet Society (2006). 50 Abstract 52 This document specifies the Path Computation Element communication 53 Protocol (PCEP) for communications between a Path Computation Client 54 (PCC) and a Path Computation Element (PCE), or between two PCEs. 55 Such interactions include path computation requests and path 56 computation replies as well as notifications of specific states 57 related to the use of a PCE in the context of MPLS and GMPLS Traffic 58 Engineering. The PCEP protocol is designed to be flexible and 59 extensible so as to easily allow for the addition of further messages 60 and objects, should further requirements be expressed in the future. 62 Requirements Language 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 RFC 2119 [RFC2119]. 68 Table of Contents 70 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 6 73 4. Transport protocol . . . . . . . . . . . . . . . . . . . . . . 6 74 5. Architectural Protocol Overview (Model) . . . . . . . . . . . 7 75 5.1. Problem . . . . . . . . . . . . . . . . . . . . . . . . . 7 76 5.2. Architectural Protocol Overview . . . . . . . . . . . . . 7 77 5.2.1. Initialization Phase . . . . . . . . . . . . . . . . . 8 78 5.2.2. Path computation request sent by a PCC to a PCE . . . 9 79 5.2.3. Path computation reply sent by the PCE to a PCC . . . 10 80 5.2.4. Notification . . . . . . . . . . . . . . . . . . . . . 12 81 5.2.5. Termination of the PCEP Session . . . . . . . . . . . 13 82 6. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . . 14 83 6.1. Common header . . . . . . . . . . . . . . . . . . . . . . 14 84 6.2. Open message . . . . . . . . . . . . . . . . . . . . . . . 15 85 6.3. Keepalive message . . . . . . . . . . . . . . . . . . . . 16 86 6.4. Path Computation Request (PCReq) message . . . . . . . . . 17 87 6.5. Path Computation Reply (PCRep) message . . . . . . . . . . 18 88 6.6. Notification (PCNtf) message . . . . . . . . . . . . . . . 19 89 6.7. Error (PCErr) Message . . . . . . . . . . . . . . . . . . 20 90 6.8. Close message . . . . . . . . . . . . . . . . . . . . . . 21 91 7. Object Formats . . . . . . . . . . . . . . . . . . . . . . . . 21 92 7.1. Common object header . . . . . . . . . . . . . . . . . . . 21 93 7.2. OPEN object . . . . . . . . . . . . . . . . . . . . . . . 23 94 7.3. RP Object . . . . . . . . . . . . . . . . . . . . . . . . 24 95 7.3.1. Object definition . . . . . . . . . . . . . . . . . . 24 96 7.3.2. Handling of the RP object . . . . . . . . . . . . . . 26 97 7.4. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . . 27 98 7.5. END-POINT Object . . . . . . . . . . . . . . . . . . . . . 28 99 7.6. BANDWIDTH Object . . . . . . . . . . . . . . . . . . . . . 29 100 7.7. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 30 101 7.8. ERO Object . . . . . . . . . . . . . . . . . . . . . . . . 33 102 7.9. RRO Object . . . . . . . . . . . . . . . . . . . . . . . . 33 103 7.10. LSPA Object . . . . . . . . . . . . . . . . . . . . . . . 34 104 7.11. IRO Object . . . . . . . . . . . . . . . . . . . . . . . . 36 105 7.12. SVEC Object . . . . . . . . . . . . . . . . . . . . . . . 36 106 7.12.1. Notion of Dependent and Synchronized path 107 computation requests . . . . . . . . . . . . . . . . . 36 108 7.12.2. SVEC Object . . . . . . . . . . . . . . . . . . . . . 38 109 7.12.3. Handling of the SVEC Object . . . . . . . . . . . . . 39 110 7.13. NOTIFICATION Object . . . . . . . . . . . . . . . . . . . 40 111 7.14. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . . 43 112 7.15. LOAD-BALANCING Object . . . . . . . . . . . . . . . . . . 46 113 7.16. CLOSE Object . . . . . . . . . . . . . . . . . . . . . . . 47 114 8. Manageability Considerations . . . . . . . . . . . . . . . . . 48 115 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 116 9.1. TCP Port . . . . . . . . . . . . . . . . . . . . . . . . . 48 117 9.2. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . 48 118 9.3. PCEP Object . . . . . . . . . . . . . . . . . . . . . . . 49 119 9.4. Notification . . . . . . . . . . . . . . . . . . . . . . . 50 120 9.5. PCEP Error . . . . . . . . . . . . . . . . . . . . . . . . 51 121 10. PCEP Finite State Machine (FSM) . . . . . . . . . . . . . . . 52 122 11. Security Considerations . . . . . . . . . . . . . . . . . . . 58 123 11.1. PCEP Authentication and Integrity . . . . . . . . . . . . 59 124 11.2. PCEP Privacy . . . . . . . . . . . . . . . . . . . . . . . 59 125 11.3. Protection against Denial of Service attacks . . . . . . . 59 126 11.4. Request input shaping/policing . . . . . . . . . . . . . . 60 127 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 60 128 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 60 129 13.1. Normative References . . . . . . . . . . . . . . . . . . . 60 130 13.2. Informative References . . . . . . . . . . . . . . . . . . 61 131 Appendix A. Compliance with the PCECP Requirement Document . . . 62 132 Appendix B. PCEP Variables . . . . . . . . . . . . . . . . . . . 62 133 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 63 134 Intellectual Property and Copyright Statements . . . . . . . . . . 65 136 1. Terminology 138 Terminology used in this document 140 Explicit path: full explicit path from start to destination made of a 141 list of strict hops where a hop may be an abstract node such as an 142 AS. 144 IGP Area: OSPF Area or IS-IS level. 146 Inter-domain TE LSP: A TE LSP whose path transits across at least two 147 different domains where a domain can either be an IGP area, an 148 Autonomous System or a sub-AS (BGP confederations). 150 PCC: Path Computation Client: any client application requesting a 151 path computation to be performed by a Path Computation Element. 153 PCE: Path Computation Element: an entity (component, application or 154 network node) that is capable of computing a network path or route 155 based on a network graph and applying computational constraints. 157 PCEP Peer: an element involved in a PCEP session (i.e. a PCC or the 158 PCE). 160 TED: Traffic Engineering Database which contains the topology and 161 resource information of the domain. The TED may be fed by IGP 162 extensions or potentially by other means. 164 TE LSP: Traffic Engineering Label Switched Path. 166 Strict/loose path: mix of strict and loose hops comprising of at 167 least one loose hop representing the destination where a hop may be 168 an abstract node such as an AS. 170 Within this document, when describing PCE-PCE communications, the 171 requesting PCE fills the role of a PCC. This provides a saving in 172 documentation without loss of function. 174 2. Introduction 176 [RFC4655]describes the motivations and architecture for a PCE-based 177 model for the computation of MPLS and GMPLS TE LSPs. The model 178 allows the separation of PCE from PCC, and allows cooperation between 179 PCEs. This necessitates a communication protocol between PCC and 180 PCE, and between PCEs. 182 [RFC4657] states the generic requirements for such a protocol 183 including the requirement for using the same protocol between PCC and 184 PCE, and between PCEs. Additional application-specific requirements 185 (for scenarios such as inter-area, inter-AS, etc.) are not included 186 in [RFC4657], but there is a requirement that any solution protocol 187 must be easily extensible to handle other requirements as they are 188 introduced in application-specific requirements documents. Examples 189 of such application-specific requirements are 190 [I-D.ietf-pce-pcecp-interarea-reqs], 191 [I-D.ietf-pce-interas-pcecp-reqs] and [I-D.ietf-pce-inter-layer-req]. 193 This document specifies the Path Computation Element communication 194 Protocol (PCEP) for communications between a Path Computation Client 195 (PCC) and a Path Computation Element (PCE), or between two PCEs. 196 Such interactions include path computation requests and path 197 computation replies as well as notifications of specific states 198 related to the use of a PCE in the context of MPLS and GMPLS Traffic 199 Engineering. 201 The PCEP protocol is designed to be flexible and extensible so as to 202 easily allow for the addition of further messages and objects, should 203 further requirements be expressed in the future. 205 3. Assumptions 207 [RFC4655] describes various types of PCE. PCEP does not make any 208 assumption and thus does not impose any constraint on the nature of 209 the PCE. 211 Moreover, it is assumed that the PCE gets the required information so 212 as to perform the computation of TE LSP that usually requires network 213 topology and resource information. Such information can be gathered 214 by routing protocols or by some other means, the gathering of which 215 is out of the scope of this document. 217 Similarly, no assumption is made on the discovery method used by a 218 PCC to discover a set of PCEs (e.g. via static configuration or 219 dynamic discovery) and on the algorithm used to select a PCE. For 220 the sake of reference [RFC4674] defines a list of requirements for 221 dynamic PCE discovery and IGP-based solution for such PCE discovery 222 are specified in [I-D.ietf-pce-disco-proto-ospf] and 223 [I-D.ietf-pce-disco-proto-isis]. 225 4. Transport protocol 227 PCEP operates over TCP using a well-known TCP port (to be assigned by 228 IANA). This allows the requirements of reliable messaging and flow 229 control to be met without further protocol work. 231 An implementation may decide to keep the TCP session alive for an 232 unlimited time (this may for instance be appropriate when path 233 computation requests are sent on a frequent basis so as to avoid to 234 open a TCP session each time a path computation request is needed 235 that would incur additional processing delays). Conversely, in some 236 other circumstances, it may be desirable to systematically open and 237 close the TCP connection for each PCEP request (for instance when 238 sending of path computation request is a rare event). 240 5. Architectural Protocol Overview (Model) 242 The aim of this section is to describe the PCEP protocol model in the 243 spirit of [RFC4101]. An architecture protocol overview (the big 244 picture of the protocol) is provided in this section. Protocol 245 details can be found in further sections. 247 5.1. Problem 249 The PCE-based architecture used for the computation of MPLS and GMPLS 250 TE LSP is described in [RFC4655]. When the PCC and the PCE are not 251 collocated, a communication protocol between the PCC and the PCE is 252 needed. PCEP is such a protocol designed specifically for 253 communications between a PCC and a PCE or between two PCEs: a PCC may 254 use PCEP to send a path computation request for one or more TE LSP(s) 255 to a PCE and such a PCE may reply with a set of computed path(s) if 256 one or more path(s) satisfying the set of constraints can be found. 258 5.2. Architectural Protocol Overview 260 PCEP operates over TCP, which allows the requirements of reliable 261 messaging and flow control to be met without further protocol work. 263 Several PCEP messages are defined: 265 - Open and Keepalive messages are used to initiate and maintain a 266 PCEP session respectively. 268 - PCReq: a PCEP message sent by a PCC to a PCE to request a path 269 computation. 271 - PCRep: a PCEP message sent by a PCE to a PCC in reply to a path 272 computation request. A PCRep message can either contain a set of 273 computed path(s) if the request could be satisfied or a negative 274 reply otherwise. 276 - PCNtf: a PCEP notification message either sent by a PCC to a PCE or 277 a PCE to a PCC to notify of specific event. 279 - PCErr: a PCEP message sent upon the occurrence of a protocol error 280 condition. 282 - Close message: a message used to close a PCEP session. 284 The set of available PCE(s) may be either statically configured on a 285 PCC or dynamically discovered. 287 The mechanisms used to discover one or more PCE(s) and to select a 288 PCE are out of the scope of this document. 290 A PCC may have PCEP sessions with more than one PCE and similarly a 291 PCE may have PCEP sessions with multiple PCCs. 293 The establishment of a PCEP session is always inititated by the PCC. 295 5.2.1. Initialization Phase 297 The initialization phase consists of two successive steps (described 298 in a schematic form in Figure 1): 300 1) Establishment of a TCP connection (3-way handshake) between the 301 PCC and the PCE. 303 2) Establishment of a PCEP session over the TCP connection. 305 Once the TCP connection is established, the PCC and the PCE (also 306 referred to as "PCEP peers") initiate a PCEP session establishment 307 during which various session parameters are negotiated. These 308 parameters are carried within Open messages and include the keepalive 309 timer, the Deadtimer and potentially other detailed capabilities and 310 policy rules that specify the conditions under which path computation 311 requests may be sent to the PCE. If the PCEP session establishment 312 phase fails because the PCEP peers disagree on the exchanged 313 parameters or one of the PCEP peers does not answer after the 314 expiration of the establishment timer, the TCP connection is 315 immediately closed. Successive retries are permitted but an 316 implementation SHOULD make use of an exponential back-off session 317 establishment retry procedure. 319 Keepalive messages are used to acknowledge Open messages and once the 320 PCEP session has been successfully established, Keepalive messages 321 are exchanged between PCEP peers to ensure the liveness of the PCEP 322 session. 324 A single PCEP session can exist between a pair a PCEP peers. 326 Details about the Open message and the Keepalive messages can be 327 found in . (Section 6.2) and Section 6.3 respectively. 329 +-+-+ +-+-+ 330 |PCC| |PCE| 331 +-+-+ +-+-+ 332 | | 333 |---- Open message --->| 334 | | 335 |<--- Open message ----| 336 | | 337 | | 338 | | 339 |<--- Keepalive -------| 340 | | 341 |---- Keepalive ------>| 343 Figure 1: PCEP Initialization phase (initiated by a PCC) 345 5.2.2. Path computation request sent by a PCC to a PCE 347 +-+-+ +-+-+ 348 |PCC| |PCE| 349 +-+-+ +-+-+ 350 1)Path computation | | 351 event | | 352 2)PCE Selection | | 353 3)Path computation |---- PCReq message--->| 354 request sent to | | 355 the selected PCE | | 357 Figure 2: Path computation request 359 Once a PCC (or a PCE) has successfully established a PCEP session 360 with one or more PCEs, if an event is triggered that requires the 361 computation of a set of path(s), the PCC first selects one of more 362 PCE(s) to send the request to. Note that the PCE selection decision 363 process may have taken place prior to the PCEP session establishment. 365 Once the PCC has selected a PCE, it sends a path computation request 366 to the PCE (PCReq message) that contains a variety of objects that 367 specify the set of constraints and attributes for the path to be 368 computed. For example "Compute a TE LSP path with source IP 369 address=x.y.z.t, destination IP address=x'.y'.z'.t', bandwidth=B 370 Mbit/s, Setup/Hold priority=P, ...". Additionally, the PCC may 371 desire to specify the urgency of such request by assigning a request 372 priority. Each request is uniquely identified by a request-id number 373 and the PCC-PCE address pair. The process is shown in a schematic 374 form in figure 2. 376 Details about the PCReq message can be found in Section 6.4 378 5.2.3. Path computation reply sent by the PCE to a PCC 379 +-+-+ +-+-+ 380 |PCC| |PCE| 381 +-+-+ +-+-+ 382 | | 383 |---- PCReq message--->| 384 | |1) Path computation 385 | |request received 386 | | 387 | |2)Path successfully 388 | |computed 389 | | 390 | |3) Computed path(s) sent 391 | |to the PCC 392 |<--- PCRep message ---| 393 | (Positive reply) | 395 Figure 3a: Path computation request with successful path computation 397 +-+-+ +-+-+ 398 |PCC| |PCE| 399 +-+-+ +-+-+ 400 | | 401 | | 402 |---- PCReq message--->| 403 | |1) Path computation 404 | |request received 405 | | 406 | |2) No Path found that 407 | |satisfies the request 408 | | 409 | |3) Negative reply sent to 410 | |the PCC (optionally with 411 | |various additional 412 | |information) 413 |<--- PCRep message ---| 414 | (Negative reply) | 416 Figure 3b: Path computation request with unsuccessful path computation 417 Upon receiving a path computation request from a PCC, the PCE 418 triggers a path computation, the result of which can either be: 420 - Positive (Figure 3-a): the PCE manages to compute a path satisfying 421 the set of required constraints, in which case the PCE returns the 422 set of computed path(s) to the requesting PCC. Note that PCEP 423 supports the capability to send a single request which requires the 424 computation of more than one path (e.g. computation of a set of link- 425 diverse paths). 427 - Negative (Figure 3-b): no path could be found that satisfies the 428 set of constraints. In this case, a PCE may provide the set of 429 constraints that led to the path computation failure. Upon receiving 430 a negative reply, a PCC may decide to resend a modified request or 431 take any other appropriate action. 433 Details about the PCRep message can be found in Section 6.5. 435 5.2.4. Notification 437 There are several circumstances whereby a PCE may want to notify a 438 PCC of a specific event. For example, suppose that the PCE suddenly 439 experiences some congestion that would lead to unacceptable response 440 times. The PCE may want to notify one or more PCCs that some of 441 their requests (listed in the notification) will not be satisfied or 442 may experience unacceptable delays. Upon receiving such 443 notification, the PCC may decide to redirect it(s) path computation 444 request(s) towards another PCE, if an alternate PCE is available. 445 Similarly, a PCC may desire to notify a PCE of particular event such 446 as the cancellation of pending request(s). 448 +-+-+ +-+-+ 449 |PCC| |PCE| 450 +-+-+ +-+-+ 451 1)Path computation | | 452 event | | 453 2)PCE Selection | | 454 3)Path computation |---- PCReq message--->| 455 request X sent to | |4) Path computation 456 the selected PCE | |triggered 457 | | 458 | | 459 5) Path computation| | 460 request X cancelled| | 461 |---- PCNtf message -->| 462 | |6) Path computation 463 | |request X cancelled 465 Figure 4: Example of PCC notification (request cancellation) sent to a PCE 467 +-+-+ +-+-+ 468 |PCC| |PCE| 469 +-+-+ +-+-+ 470 1)Path computation | | 471 event | | 472 2)PCE Selection | | 473 3)Path computation |---- PCReq message--->| 474 request X sent to | |4) Path computation 475 the selected PCE | |triggered 476 | | 477 | | 478 | |5) PCE experiencing 479 | |congestion 480 | | 481 | |6) Path computation 482 | |request X cancelled 483 | | 484 |<--- PCNtf message----| 486 Figure 5: Example of PCE notification (request(s) cancellation) sent to a PCC 488 Details about the PCNtf message can be found in Section 6.6. 490 5.2.5. Termination of the PCEP Session 492 When one of the PCEP peers desires to terminate a PCEP session it 493 first sends a PCEP Close message and then close the TCP connection. 495 If the PCEP session is terminated by the PCE, the PCC clears all the 496 states related to pending requests previously sent to the PCE. 497 Similarly, if the PCC terminates a PCEP session the PCE clears all 498 pending path computation requests sent by the PCC in question as well 499 as the related states. A Close message can only be sent to terminate 500 a PCEP session if the PCEP session has previously been established. 502 In case of TCP connection failure, the PCEP session SHOULD be 503 maintained for a period of time equal to the DeadTimer. 505 Details about the Close message can be found in Section 6.8. 507 6. PCEP Messages 509 A PCEP message consists of a common header followed by a variable 510 length body made of a set of objects that can either be mandatory or 511 optional. In the context of this document, an object is said to be 512 mandatory in a PCEP message when the object MUST be included for the 513 message to be considered as valid. Thus a PCEP message with a 514 missing mandatory object MUST be considered as a malformed message 515 and such condition MUST trigger an Error message. Conversely, if an 516 object is optional, the object may or may not be present. 518 A flag referred to as the P flag is defined in the common header of 519 each PCEP object (see Section 7.1) that can be set by a PCEP peer to 520 enforce a PCE to take into account the related information during the 521 path computation. For example, the METRIC object allows a PCC to 522 specify a bounded acceptable path cost. The COST object is optional 523 but a PCC may set a flag to ensure that such constraint is taken into 524 account. Similarly to the previous case, if such constraint cannot 525 be taken into account by the PCE, this should trigger an Error 526 message. 528 For each PCEP message type a set of rules is defined that specify the 529 set of objects that the message can carry. We use the Backus-Naur 530 Form (BNF) to specify such rules. Square brackets refer to optional 531 sub-sequences. An implementation MUST form the PCEP messages using 532 the object ordering specified in this document. 534 6.1. Common header 535 0 1 2 3 536 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 1 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | Ver | Flags | Message-Type | Reserved | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | Message-Lenght | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 Figure 6: PCEP message common header 544 Ver (Version - 4 bits): PCEP protocol version number. Current 545 version is version 1. 547 Flags (8 bits): no flags are currently defined. 549 Message-Type (8 bits): 551 The following message types are currently defined (to be confirmed by 552 IANA). 553 Value Meaning 554 1 Open 555 2 Keepalive 556 3 Path Computation Request 557 4 Path Computation Reply 558 5 Notification 559 6 Error 560 7 Close 561 Message Length (32 bits): total length of the PCEP message expressed 562 in bytes including the common header. 564 6.2. Open message 566 The Open message is a PCEP message sent by a PCC to a PCE and a PCE 567 to a PCC in order to establish a PCEP session. The Message-Type 568 field of the PCEP common header for the Open message is set to 1 (To 569 be confirmed by IANA). 571 Once the TCP connection has been successfully established, the first 572 message sent by the PCC to the PCE or by the PCE to the PCC MUST be 573 an Open message. Any message received prior to an Open message MUST 574 trigger a protocol error condition and the PCEP session MUST be 575 terminated. The Open message is used to establish a PCEP session 576 between the PCEP peers. During the establishment phase the PCEP 577 peers exchange several session characteristics. If both parties 578 agree on such characteristics the PCEP session is successfully 579 established. 581 Open message 582 ::= 583 584 The Open message MUST contain exactly one OPEN object (see 585 Section 7.2). Various session characteristics are specified within 586 the OPEN object. 588 Once an Open message has been sent to a PCEP peer, the sender MUST 589 start an initialization timer called KeepWait after the expiration of 590 which if neither an Open message has been received nor a PCErr 591 message in case of disagreement of the session characteristics, the 592 TCP connection MUST be released (see Section 10for details). 594 The KeepWait timer has a fixed value of 1 minute. 596 Upon the receipt of an Open message, the receiving PCEP peer MUST 597 determine whether the suggested PCEP session characteristics are 598 acceptable. If at least one of the characteristic(s) is not 599 acceptable by the receiving peer, it MUST send an Error message. The 600 Error message SHOULD also contain the related Open object: for each 601 unacceptable session parameter, an acceptable parameter value SHOULD 602 be proposed in the appropriate field of the Open object in place of 603 the originally proposed value. The PCEP peer MAY decide to resend an 604 Open message with different session characteristics. If a second 605 Open message is received with the same set of parameters or with 606 parameters that are still unacceptable, the receiving peer MUST send 607 an Error message and it MUST immediately close the TCP connection. 608 Details about error message can be found in Section 7.14. 610 If the PCEP session characteristics are acceptable, the receiving 611 PCEP peer MUST consequently send a Keepalive message (defined in 612 Section 6.3) that would serve as an acknowledgment. 614 The PCEP session is considered as established once both PCEP peers 615 have received a Keepalive message from their peer. 617 6.3. Keepalive message 619 A Keepalive message is a PCEP message sent by a PCC or a PCE in order 620 to keep the session in active state. The Message-Type field of the 621 PCEP common header for the Keepalive message is set to 2 (To be 622 confirmed by IANA). The Keepalive message does not contain any 623 object. 625 Keepalive: PCEP has its own keepalive mechanism used to ensure of the 626 liveness of the PCEP session. This requires the determination of the 627 frequency at which each PCEP peer sends keepalive messages. 628 Asymmetric values may be chosen; thus there is no constraints 629 mandating the use of identical keepalive frequencies by both PCEP 630 peers. The DeadTimer is defined as the period of time after the 631 expiration of which a PCEP peer declares the session down if no PCEP 632 message has been received (keepalive or any other PCEP message: thus, 633 any PCEP message acts as a keepalive message). Similarly, there is 634 no constraints mandating the use of identical DeadTimers by both PCEP 635 peers. The minimum KeepAliveTimer value is 1 second. 637 Keepalive messages are used either to acknowledge an Open message if 638 the receiving PCEP peer agrees on the session characteristics and to 639 ensure the liveness of the PCEP session. Keepalive messages are sent 640 at the frequency specified in the OPEN object carried within an Open 641 message. Because any PCEP message may serve as Keepalive an 642 implementation may either decide to send Keepalive messages at the 643 same frequency regardless on whether other PCEP messages might have 644 been sent since the last sent Keepalive message or may decide to 645 differ the sending of the next Keepalive message based on the time at 646 which the last PCEP message (other than Keepalive) was sent. 648 Keepalive message 649 ::= 651 6.4. Path Computation Request (PCReq) message 653 A Path Computation Request message (also referred to as a PCReq 654 message) is a PCEP message sent by a PCC to a PCE so as to request a 655 path computation. The Message-Type field of the PCEP common header 656 for the PCReq message is set to 3 (To be confirmed by IANA). 658 There are two mandatory objects that MUST be included within a PCReq 659 message: the RP and the END-POINTS objects (see section Section 7). 660 If one of these objects is missing, the receiving PCE MUST send an 661 error message to the requesting PCC. Other objects are optional. 663 The format of a PCReq message is as follows: 664 ::= 665 [] 666 668 where: 669 ::=[] 670 ::=[] 672 ::= 673 [] 674 [] 675 [] 676 [] 677 [] 678 [] 679 [] 680 The SVEC, RP, END-POINTS, LSPA, BANDWIDTH, METRIC, ERO, IRO and LOAD- 681 BALANCING objects are defined in Section 7. The special case of two 682 BANDWIDTH objects is discussed in details in Section 7.6. 684 6.5. Path Computation Reply (PCRep) message 686 The PCEP Path Computation Reply message (also referred to as a PCRep 687 message) is a PCEP message sent by a PCE to a requesting PCC in 688 response to a previously received PCReq message. The Message-Type 689 field of the PCEP common header is set to 4 (To be confirmed by 690 IANA). 692 The PCRep message MUST contain at least one RP object. For each 693 reply that is bundled into a single PCReq message, an RP object MUST 694 be included that contains a Request-ID-number identical to the one 695 specified in the RP object carried in the corresponding PCReq message 696 (see Section 7.3for the definition of the RP object). 698 A PCRep message may contain a set of computed path(s) corresponding 699 to either a single path computation request with load-balancing (see 700 Section 7.15) or multiple path computation requests originated by a 701 requesting PCC. The PCReq message may also contain multiple 702 acceptable paths corresponding to the same request. 704 The bundling of multiple replies to a set of path computation 705 requests within a single PCRep message is supported by the PCEP 706 protocol. If a PCE receives non-synchronized path computation 707 requests by means of one or more PCReq messages from a requesting PCC 708 it may decide to bundle the computed paths within a single PCRep 709 message so as to reduce the control plane load. Note that the 710 counter side of such an approach is the introduction of additional 711 delays for some path computation requests of the set. Conversely, a 712 PCE that receives multiple requests within the same PCReq message, 713 may decide to provide each computed path in separate PCRep messages. 715 If the path computation request can be satisfied (the PCE finds a set 716 of path(s) that satisfy the set of constraint(s)), the set of 717 computed path(s) specified by means of ERO object(s) is inserted in 718 the PCRep message. The ERO object is defined in Section 7.8. Such a 719 situation where multiple computed paths are provided in a PCRep 720 message is discussed in detail in Section 7.12. Furthermore, when a 721 PCC requests the computation a set of paths for a total amount of 722 bandwidth of X by means of a LOAD-BALANCING object carried within a 723 PCReq message, the ERO of each computed path may be followed by a 724 BANDWIDTH object as discussed in section Section 7.15. 726 If the path computation request cannot be satisfied, the PCRep 727 message MUST include a NO-PATH object. The NO-PATH object (described 728 in Section 7.4) may also comprise other information (e.g reasons for 729 the path computation failure). 731 The format of a PCRep message is as follows: 732 ::= 733 [] 734 736 where: 737 ::=[] 738 ::=[] 740 ::= 741 [] 742 [] 744 ::=[] 746 ::= 747 [] 748 [] 749 [] 750 [] 752 6.6. Notification (PCNtf) message 754 The PCEP Notification message (also referred to as the PCNtf message) 755 can either be sent by a PCE to a PCC or by a PCC to a PCE so as to 756 notify of a specific event. The Message-Type field of the PCEP 757 common header is set to 5 (To be Confirmed by IANA). 759 The PCNtf message MUST carry at least one NOTIFICATION object and may 760 contain several NOTIFICATION objects should the PCE or the PCC intend 761 to notify of multiple events. The NOTIFICATION object is defined in 762 Section 7.13. The PCNtf message may also contain an RP object (see 763 Section 7.3 when the notification refers to a particular path 764 computation request. 766 The PCNtf message may be sent by a PCC or a PCE in response to a 767 request or in an unsolicited manner. 769 The format of a PCNtf message is as follows: 770 ::= 771 773 ::= [] 775 ::= [] 776 778 :== 780 := 782 6.7. Error (PCErr) Message 784 The PCEP Error message (also referred to as a PCErr message) is sent 785 when a protocol error condition is met. The Message-Type field of 786 the PCEP common header is set to 6. 788 The PCErr message may be sent by a PCC or a PCE in response to a 789 request or in an unsolicited manner. In the former case, the PCErr 790 message MUST include the set of RP objects related to the pending 791 path computation request(s) that triggered the protocol error 792 condition. In the later case (unsollicited), no RP object is 793 inserted in the PCErr message. No RP object is inserted in a PCErr 794 when the error condition occurred during the initialization phase. A 795 PCErr message MUST contain a PCEP-ERROR object specifying the PCEP 796 error condition. The PCEP-ERROR object is defined in section 797 Section 7.14. 799 The format of a PCErr message is as follows: 800 ::= 801 802 [] 804 :==[] 805 ::=[] 806 808 :==[] 810 :==[] 811 The procedure upon the reception of a PCErr message is defined in 812 Section 7.14. 814 6.8. Close message 816 The Close message is a PCEP message sent by either a PCC to a PCE or 817 by a PCE to a PCC in order to close a PCEP session. The Message-Type 818 field of the PCEP common header for the Open message is set to 7 (To 819 be confirmed by IANA). 821 Close message 822 ::= 823 824 The Close message MUST contain exactly one CLOSE object (see 825 Section 6.8). 827 Upon the receipt of a Close message, the receiving PCEP peer MUST 828 cancel all pending requests and MUST close the TCP connection. 830 7. Object Formats 832 7.1. Common object header 833 A PCEP object carried within a PCEP message consists of one or more 834 32-bit words with a common header which has the following format: 835 0 1 2 3 836 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 1 837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 838 | Object-Class | OT |Res|P|I| Object Length (bytes) | 839 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 840 | | 841 // (Object body) // 842 | | 843 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 845 Figure 8: PCEP common object header 847 Object-Class (8 bits): identifies the PCEP object class. 849 OT (Object-Type - 4 bits): identifies the PCEP object type. 851 The Object-Class and Object-Type fields are managed by IANA. 853 The Object-Class and Object-Type fields uniquely identify each PCEP 854 object. 856 Res flags (2 bits). Reserved field (MUST be set to 0). 858 P flag (Processing-Rule - 1-bit): the P flag allows a PCC to specify 859 in a PCReq message sent to a PCE whether the object must be taken 860 into account by the PCE during path computation or is just optional. 861 When the P flag is set, the object MUST be taken into account by the 862 PCE. Conversely, when the P flag is cleared, the object is optional 863 and the PCE is free to ignore it if not supported. 865 I flag (Ignore - 1 bit): the I flag is used by a PCE in a PCRep 866 message to indicate to a PCC whether or not an optional object was 867 processed. The PCE MAY include the ignored optional object in its 868 reply and set the I flag to indicate that the optional object was 869 ignored during path computation. When the I flag is cleared, the PCE 870 indicates that the optional object was processed during the path 871 computation. The setting of the I flag for optional objects is 872 purely indicative and optional. The I flag MUST be cleared if the P 873 flag is set. 875 If the PCE does not understand an object with the P Flag set or 876 understands the object but decides to ignore the object, the entire 877 PCEP message MUST be rejected and the PCE MUST send a PCErr message 878 with Error-Type="Unknown Object" or "Not supported Object". 880 Object Length (16 bits). Specifies the total object length including 881 the header, in bytes. The Object Length field MUST always be a 882 multiple of 4, and at least 4. The maximum object content length is 883 65528 bytes. 885 7.2. OPEN object 887 The OPEN object MUST be present in each Open message and may be 888 present in PCErr message. There MUST be only one OPEN object per 889 Open or PCErr message. 891 The OPEN object contains a set of fields used to specify the PCEP 892 protocol version, Keepalive frequency, DeadTimer, PCEP session ID 893 along with various flags. The OPEN object may also contain a set of 894 TLVs used to convey various session characteristics such as the 895 detailed PCE capabilities, policy rules and so on. No such TLV is 896 currently defined. 898 OPEN Object-Class is to be assigned by IANA (recommended value=1) 900 OPEN Object-Type is to be assigned by IANA (recommended value=1) 902 The format of the OPEN object body is as follows: 903 0 1 2 3 904 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 1 905 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 906 | Ver | Keepalive | Deadtimer | SID | Flags | 907 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 908 | | 909 // Optional TLV(s) // 910 | | 911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 913 Figure 9: OPEN Object format 914 Ver (Ver - 3 bits): PCEP version. Current version is 1. 916 Keepalive (8 bits): minimum period of time (in seconds) between the 917 sending of PCEP messages. The minimum value for the Keepalive is 1 918 second. When set to 0, once the session is established, no further 919 keepalives need to be sent to the remote peer. A RECOMMENDED value 920 for the keepalive frequency is 30 seconds. 922 DeadTimer (8 bits): specifies the amount of time after the expiration 923 of which a PCEP peer declares the session with the sender of the Open 924 message down if no PCEP message has been received. The DeadTimer 925 MUST be set to 0 if the Keepalive is set to 0. A RECOMMENDED value 926 for the DeadTimer is 4 times the value of the Keepalive. 928 SID (PCEP session-ID - 8 bits): specifies a 2 octet unsigned PCEP 929 session number that identifies the current session. The SID MUST be 930 incremented each time a new PCEP session is established and is mainly 931 used for logging and troubleshooting purposes. 933 Flags (5 bits): No Flags are currently defined. 935 Optional TLVs may be included within the OPEN object body to specify 936 PCC or PCE characteristics. The specification of such TLVs is 937 outside the scope of this document. 939 When present in an Open message, the OPEN object specifies the 940 proposed PCEP session characteristics. Upon receiving unacceptable 941 PCEP session characteristics during the PCEP session initialization 942 phase, the receiving PCEP peer (PCE) MAY include a PCEP object within 943 the PCErr message so as to propose alternative session characteristic 944 values. 946 7.3. RP Object 948 The RP (Request Parameters) object MUST be carried within each PCReq 949 and PCRep messages and MAY be carried within PCNtf and PCErr 950 messages. The P flag of the RP object MUST be set. The RP object is 951 used to specify various characteristics of the path computation 952 request. 954 7.3.1. Object definition 956 RP Object-Class is to be assigned by IANA (recommended value=2) 958 RP Object-Type is to be assigned by IANA (recommended value=1) 959 The format of the RP object body is as follows: 960 0 1 2 3 961 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 1 962 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 963 | Reserved | Flags |F|O|B|R| Pri | 964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 965 | Request-ID-number | 966 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 967 | | 968 // Optional TLV(s) // 969 | | 970 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 972 Figure 10: RP object body format 974 The RP object body has a variable length and may contain additional 975 TLVs. No TLVs are currently defined. 977 Flags: 18 bits - The following flags are currently defined: 979 Pri (Priority - 3 bits): the Priority field may be used by the 980 requesting PCC to specify to the PCE the request's priority from 1 to 981 7. The decision of which priority should be used for a specific 982 request is of a local matter and MUST be set to 0 when unused. 983 Furthermore, the use of the path computation request priority by the 984 PCE's requests scheduler is implementation specific and out of the 985 scope of this document. Note that it is not required for a PCE to 986 support the priority field: in this case, it is RECOMMENDED to set 987 the priority field to 0 by the PCC in the RP object. If the PCE does 988 not take into account the request priority, it is RECOMMENDED to set 989 the priority field to 0 in the RP object carried within the 990 corresponding PCRep message, regardless of the priority value 991 contained in the RP object carried within the corresponding PCReq 992 message. A higher numerical value of the priority field reflects a 993 higher priority. Note that it is the responsibility of the network 994 administrator to make use of the priority values in a consistent 995 manner across the various PCC(s). The ability of a PCE to support 996 requests prioritization may be dynamically discovered by the PCC(s) 997 by means of PCE capability discovery. If not advertised by the PCE, 998 a PCC may decide to set the request priority and will learn the 999 ability of the PCE the support request prioritization by observing 1000 the Priority field of the RP object received in the PCRep message. 1001 If the value of the Pri field is set to 0, this means that the PCE 1002 does not support the handling of request priorities: in other words, 1003 the path computation request has been honoured but without taking the 1004 request priority into account. 1006 R (Reoptimization - 1 bit): when set, the requesting PCC specifies 1007 that the PCReq message relates to the reoptimization of an existing 1008 TE LSP in which case, in addition to the TE LSP attributes, the 1009 current path of the existing TE LSP to be reoptimized MUST be 1010 provided in the PCReq (except for 0-bandwidth TE LSP) message by 1011 means of an RRO object defined in Section 7.9. 1013 B (Bi-directional - 1 bit): when set, the PCC specifies that the path 1014 computation request relates to a bidirectional TE LSP that has the 1015 same traffic engineering requirements including fate sharing, 1016 protection and restoration, LSRs, and resource requirements (e.g. 1017 latency and jitter) in each direction. When cleared, the TE LSP is 1018 unidirectional. 1020 O (strict/lOose - 1 bit): when set, in a PCReq message, this 1021 indicates that a strict/loose path is acceptable. Otherwise, when 1022 cleared, this indicates to the PCE that an explicit path is required. 1023 In a PCRep message, when the O bit is set this indicates that the 1024 returned path is strict/loose, otherwise (the O bit is cleared), the 1025 returned path is explicit. 1027 F (Fail - 1 bit): when set, the requesting PCC requires the 1028 computation of a new path for a TE LSP that has failed in which case 1029 the path of the existing TE LSP MUST be provided in the PCReq (except 1030 for 0-bandwidth TE LSP) message by means of an RRO object defined in 1031 Section 7.9. This is to avoid double bandwidth booking should the 1032 TED not be yet updated or the corresponding resources not be yet 1033 released. 1035 Request-ID-number (32 bits). The Request-ID-number value combined 1036 with the source IP address of the PCC and the PCE address uniquely 1037 identify the path computation request context. The Request-ID-number 1038 MUST be incremented each time a new request is sent to the PCE. The 1039 value 0x0000000 is considered as invalid. If no path computation 1040 reply is received from the PCE, and the PCC wishes to resend its 1041 request, the same Request-ID-number MUST be used. Conversely, 1042 different Request-ID-number MUST be used for different requests sent 1043 to a PCE. The same Request-ID-number may be used for path 1044 computation requests sent to different PCEs. The path computation 1045 reply is unambiguously identified by the IP source address of the 1046 replying PCE. 1048 7.3.2. Handling of the RP object 1050 If a PCReq message is received without containing an RP object, the 1051 PCE MUST send a PCErr message to the requesting PCC with Error- 1052 type="Required Object missing" and Error-value="RP Object missing". 1054 If the O bit of the RP message carried within a PCReq message is set 1055 and local policy has been configured on the PCE to not provide 1056 explicit path(s) (for instance, for confidentiality reasons), a PCErr 1057 message MUST be sent by the PCE to the requesting PCC and the pending 1058 path computation request MUST be discarded. The Error-type is 1059 "Policy Violation" and Error-value is "O bit set". 1061 R bit: when the R bit of the RP object is set in a PCReq message, 1062 this indicates that the path computation request relates to the 1063 reoptimization of an existing TE LSP. In this case, the PCC MUST 1064 also provide the explicit or strict/loose path by including an RRO 1065 object in the PCReq message so as to avoid double bandwidth counting 1066 if and only if the TE LSP is a non 0-bandwidth TE LSP. If the PCC 1067 has previously requested a non-explicit path (O bit set), a 1068 reoptimization can still be requested by the PCC but this implies for 1069 the PCE to be either stateful (keep track of the previously computed 1070 path with the associated list of strict hops) or to have the ability 1071 to retrieve the complete required path segment. Alternatively the 1072 PCC MUST be able to inform PCE of the working path with associated 1073 list of strict hops in PCReq. The absence of an RRO in the PCReq 1074 message for a non 0-bandwidth TE LSP when the R bit of the RP object 1075 is set MUST trigger the sending of a PCErr message with Error- 1076 type="Required Object Missing" and Error-value="RRO Object missing 1077 for reoptimization". 1079 If the PCC receives a PCRep message that contains a RP object 1080 referring to an unknown Request-ID-Number, the PCC MUST send a PCErr 1081 message with Error-Type="Unknown request reference". 1083 7.4. NO-PATH Object 1085 The No-PATH object is used in PCRep messages in response to an 1086 unsuccessful path computation request (the PCE could not find a path 1087 satisfying the set of constraints). When a PCE cannot find a path 1088 satisfying a set of constraints, it MUST include a NO-PATH object in 1089 the PCRep message. The NO-PATH object is used to report the 1090 impossibility to find a path that satisfies the set of constraints. 1091 Optionally, if the PCE supports such capability, the PCRep message 1092 MAY also contain a list of objects that specify the set of 1093 constraints that could not be satisfied. The PCE MAY just replicate 1094 the object that was received that was the cause of the unsuccessful 1095 computation or MAY optionally report a suggested value for which a 1096 path could have been found. 1098 NO-PATH Object-Class is to be assigned by IANA (recommended value=3) 1100 NO-PATH Object-Type is to be assigned by IANA (recommended value=1) 1101 The format of the NO-PATH object body is as follows: 1102 0 1 2 3 1103 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 1104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1105 |C| Flags | Reserved | 1106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1108 Figure 11: NO-PATH object format 1109 The NO-PATH object body has a fixed length of 4 octets. 1111 Flags (16 bits). The following flags are currently defined: 1113 C flag (1 bit): when set, the PCE indicates the set of unsatisfied 1114 constraints (reasons why a path could not be found) in the PCRep 1115 message by including the relevant PCEP objects. When cleared, no 1116 reason is specified. 1118 Example: consider the case of a PCC that sends a path computation 1119 request to a PCE for a TE LSP of X MBits/s. Suppose that PCE cannot 1120 find a path for X MBits/s. In this case, the PCE must include in the 1121 PCRep message a NO-PATH object. Optionally the PCE may also include 1122 the original BANDWIDTH object so as to indicate that the reason for 1123 the unsuccessful computation is the bandwidth constraint (in this 1124 case, the C flag is set). If the PCE supports such capability it may 1125 alternatively include the BANDWIDTH Object and report a value of Y in 1126 the bandwidth field of the BANDWIDTH object (in this case, the C flag 1127 is set) where Y refers to the bandwidth for which a TE LSP with the 1128 same other characteristics could have been computed. 1130 When the NO-PATH object is absent from a PCRep message, the path 1131 computation request has been fully satisfied and the corresponding 1132 path(s) is/are provided in the PCRep message. 1134 7.5. END-POINT Object 1136 The END-POINTS object is used in a PCReq message to specify the 1137 source IP address and the destination IP address of the path for 1138 which a path computation is requested. Note that the source and 1139 destination addresses specified in the END-POINTS object may or may 1140 not correspond to the source and destination IP address of the TE LSP 1141 but rather to a path segment. Two END-POINTS objects (for IPv4 and 1142 IPv6) are defined. 1144 END-POINTS Object-Class is to be assigned by IANA (recommended 1145 value=4) 1147 END-POINTS Object-Type is to be assigned by IANA (recommended value=1 1148 for IPv4 and 2 for IPv6) 1149 The format of the END-POINTS object body for IPv4 (Object-Type=1) is 1150 as follows: 1152 0 1 2 3 1153 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 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1155 | Source IPv4 address | 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1157 | Destination IPv4 address | 1158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1160 Figure 12: END-POINTS object body format for IPv4 1162 The format of the END-POINTS object for IPv6 (Object-Type=2) is as follows: 1164 0 1 2 3 1165 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 1166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1167 | | 1168 | Source IPv6 address (16 bytes) | 1169 | | 1170 | | 1171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1172 | | 1173 | Destination IPv6 address (16 bytes) | 1174 | | 1175 | | 1176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1178 Figure 13: END-POINTS object body format for IPv6 1180 The END-POINTS object body has a fixed length of 8 octets for IPv4 1181 and 32 octets for IPv6. 1183 7.6. BANDWIDTH Object 1185 The BANDWIDTH object is optional and can be used to specify the 1186 requested bandwidth for a TE LSP. In the case of a non existing TE 1187 LSP, the BANDWIDTH object MUST be included in the PCReq message so as 1188 to specify the required bandwidth for the new TE LSP. In the case of 1189 the reoptimization of an existing TE LSP, the bandwidth of the 1190 existing TE LSP MUST also be included in addition to the requested 1191 bandwidth if and only if the two values differ. Consequently, two 1192 Object-Type are defined that refer to the requested bandwidth and the 1193 bandwidth of a existing TE LSP for which a reoptimization is being 1194 performed. 1196 The BANDWIDTH object may be carried within PCReq and PCRep messages. 1198 The absence of the BANDWIDTH object MUST be interpreted by the PCE as 1199 a path computation request related to a 0 bandwidth TE LSP. 1201 BANDWIDTH Object-Class is to be assigned by IANA (recommended 1202 value=5) 1204 Two Object-Type are defined for the BANDWIDTH object: 1206 o Requested bandwidth: BANDWIDTH Object-Type is to be assigned by 1207 IANA (recommended value=1) 1209 o Bandwidth of an existing TE LSP for which a reoptimization is 1210 requested. BANDWIDTH Object-Type is to be assigned by IANA 1211 (recommended value=2) 1213 The format of the BANDWIDTH object body is as follows: 1214 0 1 2 3 1215 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 1216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1217 | Bandwidth | 1218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1220 Figure 14: BANDWIDTH object body format 1221 Bandwidth: 32 bits. The requested bandwidth is encoded in 32 bits in 1222 IEEE floating point format, expressed in bytes per second. 1224 The BANDWIDTH object body has a fixed length of 4 octets. 1226 7.7. METRIC Object 1228 The METRIC object is optional and can be used for several purposes. 1230 In a PCReq message, a PCC MAY insert a METRIC object: 1232 o To indicate the metric that MUST be optimized by the path 1233 computation algorithm. Currently, two metrics are defined: the 1234 IGP cost and the TE metric (see [RFC3785]). 1236 o To indicate a bound on the path cost than MUST NOT be exceeded for 1237 the path to be considered as acceptable by the PCC. 1239 In a PCRep message, the METRIC object MAY be inserted so as to 1240 provide the cost for the computed path. It MAY also be inserted 1241 within a PCRep with the NO-PATH object to indicate that the metric 1242 constraint could not be satisfied. 1244 The path computation algorithmic aspects used by the PCE to optimize 1245 a path with respect to a specific metric are outside the scope of 1246 this document. 1248 It must be understood that such path metric is only meaningful if 1249 used consistently: for instance, if the delay of a path computation 1250 segment is exchanged between two PCE residing in different domains, 1251 consistent ways of defining the delay must be used. 1253 The absence of the METRIC object MUST be interpreted by the PCE as a 1254 path computation request for which the PCE may choose the metric to 1255 be used. 1257 METRIC Object-Class is to be assigned by IANA (recommended value=6) 1259 METRIC Object-Type is to be assigned by IANA (recommended value=1) 1261 The format of the METRIC object body is as follows: 1262 0 1 2 3 1263 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 1264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1265 | Reserved | Flags |C|B| T | 1266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1267 | metric-value | 1268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1270 Figure 15: METRIC object body format 1272 T (Type - 8 bits): Specifies the metric type. 1274 Two values are currently defined: 1276 o T=1: The IGP metric 1278 o T=2: The TE cost 1280 B (Bound - 1 bit): When set in a PCReq message, the metric-value 1281 indicates a bound (a maximum) for the path cost that must not be 1282 exceeded for the PCC to consider the computed path as acceptable. 1283 When the B flag is cleared, the metric-value field MUST be set to 1284 0x0000. The B flag MUST always be cleared in a PCRep message. 1286 C (Cost - 1 bit): When set in a PECReq message, this indicates that 1287 the PCE MUST provide the computed path cost (should a path satisfying 1288 the constraints be found) in the PCRep message for the corresponding 1289 metric. 1291 Metric-value (32 bits): metric value encoded in 32 bits in IEEE 1292 floating point format. 1294 The METRIC object body has a fixed length of 8 octets. 1296 Multiple METRIC Objects MAY be inserted in a PCRep or the PCReq 1297 message. 1299 In a PCReq message the presence of multiple METRIC object can be used 1300 to specify a multi-parameters (e.g. a metric may be a constraint or a 1301 parameter to minimize/maximize) objective function or multiple bounds 1302 for different constraints where at most one METRIC object must be 1303 used to indicate the metric to optimize (B-flag is cleared): the 1304 other METRIC object MUST be used to reflect bound constraints (B-Flag 1305 is set). 1307 A METRIC object used to indicate the metric to optimize during the 1308 path computation MUST have the B-Flag cleared, the metric-value field 1309 set to 0x0000 and the T-Flag set to the appropriate value. 1311 A METRIC object used to reflect a bound MUST have the B-Flag set, the 1312 T-Flag and metric-value field set to the appropriate values. 1314 In a PCRep message, unless not allowed by PCE policy, at least one 1315 METRIC object MUST be present that reports the computed path cost if 1316 the C bit of the METRIC object was set in the corresponding path 1317 computation request (the B-flag MUST be cleared); optionally the 1318 PCRep message MAY contain additional METRIC objects that correspond 1319 to bound constraints, in which case the metric-value MUST be equal to 1320 the corresponding path metric cost (the B-flag MUST be set). If no 1321 path satisfying the constraints could be found by the PCE, the METRIC 1322 objects MAY also be present in the PCRep message with the NO-PATH 1323 object to indicate the constraint metric that could be satisfied. 1325 Example: if a PCC sends a path computation request to a PCE where the 1326 metric to optimize is the IGP metric and the TE metric must not 1327 exceed the value of M, two METRIC object are inserted in the PCReq 1328 message: 1330 o First METRIC Object with B=0, T=1, C=1, metric-value=0x0000 1332 o Second METRIC Object with B=1, T=2, metric-value=M 1334 If a path satisfying the set of constraints can be found by the PCE 1335 and no policy preventing to provide the path cost in place, the PCE 1336 inserts one METRIC object with B=0, T=1, metric-value= computed IGP 1337 path cost. Additionally, the PCE may insert a second METRIC object 1338 with B=1, T=2, metric-value= computed TE path cost: the second METRIC 1339 object MUST be inserted if the corresponding C bit was set in the 1340 path computation request. 1342 7.8. ERO Object 1344 The ERO object is used to encode a TE LSP. The ERO Object is carried 1345 within a PCRep message to provide the computed TE LSP should have the 1346 path computation been successful. 1348 The contents of this object are identical in encoding to the contents 1349 of the Explicit Route Object defined in [RFC3209], [RFC3473] and 1350 [RFC3477]. That is, the object is constructed from a series of sub- 1351 objects. Any RSVP ERO sub-object already defined or that could be 1352 defined in the future for use in the ERO is acceptable in this 1353 object. 1355 PCEP ERO sub-object types correspond to RSVP ERO sub-object types. 1357 Since the explicit path is available for immediate signaling by the 1358 MPLS or GMPLS control plane, the meanings of all of the sub-objects 1359 and fields in this object are identical to those defined for the ERO. 1361 ERO Object-Class is to be assigned by IANA (recommended value=7) 1363 ERO Object-Type is to be assigned by IANA (recommended value=1) 1365 7.9. RRO Object 1367 The RRO object is used to record the route followed by a TE LSP. The 1368 PCEP RRO object is exclusively carried within a PCReq message so as 1369 to specify the route followed by a TE LSP for which a reoptimization 1370 is desired. 1372 The contents of this object are identical in encoding to the contents 1373 of the Route Record Object defined in [RFC3209], [RFC3473] and 1374 [RFC3477]. That is, the object is constructed from a series of sub- 1375 objects. Any RSVP RRO sub-object already defined or that could be 1376 defined in the future for use in the RRO is acceptable in this 1377 object. 1379 The meanings of all of the sub-objects and fields in this object are 1380 identical to those defined for the RRO. 1382 PCEP RRO sub-object types correspond to RSVP RRO sub-object types. 1384 RRO Object-Class is to be assigned by IANA (recommended value=8) 1386 RRO Object-Type is to be assigned by IANA (recommended value=1) 1388 7.10. LSPA Object 1390 The LSPA object is optional and specifies various TE LSP attributes 1391 to be taken into account by the PCE during path computation. The 1392 LSPA (LSP Attributes) object can either be carried within a PCReq 1393 message or a PCRep message in case of unsuccessful path computation 1394 (in this case, the PCRep message also contains a NO-PATH object and 1395 the LSPA object is used to indicate the set of constraint(s) that 1396 could not be satisfied). Most of the fields of the LSPA object are 1397 identical to the fields of the SESSION-ATTRIBUTE object defined in 1398 [RFC3209] and [RFC4090]. When absent from the PCReq message, this 1399 means that the Setup and Holding priorities are equal to 0, and there 1400 are no affinity constraints. 1402 LSPA Object-Class is to be assigned by IANA (recommended value=9) 1404 Two Objects-Types are defined for the LSPA object: LSPA without 1405 resource affinity (Object-Type to be assigned by IANA with 1406 recommended value=1) and LSPA with resource affinity (Object-type=2). 1408 The format of the LSPA object body with and without resource affinity 1409 are as follows: 1410 0 1 2 3 1411 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 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1413 | Setup Prio | Holding Prio | Flags |L| Reserved | 1414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1415 | | 1416 // Optional TLV(s) // 1417 | | 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1420 Figure 16: LSPA object body format (without resource affinity) 1422 0 1 2 3 1423 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 1424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1425 | Exclude-any | 1426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1427 | Include-any | 1428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1429 | Include-all | 1430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1431 | Setup Prio | Holding Prio | Flags |L| Reserved | 1432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1433 | | 1434 // Optional TLV(s) // 1435 | | 1436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1438 Figure 17: LSPA object body format (with resource affinity) 1440 Setup Prio (Setup Priority - 8 bits). The priority of the session 1441 with respect to taking resources, in the range of 0 to 7. The value 1442 0 is the highest priority. The Setup Priority is used in deciding 1443 whether this session can preempt another session. 1445 Holding Prio (Holding Priority - 8 bits). The priority of the 1446 session with respect to holding resources, in the range of 0 to 7. 1447 The value 0 is the highest priority. Holding Priority is used in 1448 deciding whether this session can be preempted by another session. 1449 Flags 1451 The flag L corresponds to the "Local protection desired" bit 1452 ([RFC3209]) of the SESSION-ATTRIBUTE Object. 1454 L Flag (Local protection desired). When set, this means that the 1455 computed path must include links protected with Fast Reroute as 1456 defined in [RFC4090]. 1458 7.11. IRO Object 1460 The IRO (Include Route Object) object is optional and can be used to 1461 specify that the computed path MUST traverse a set of specified 1462 network elements. The IRO object MAY be carried within PCReq and 1463 PCRep messages. When carried within a PCRep message with the NO-PATH 1464 object, the IRO indicates the set of elements that fail the PCE to 1465 find a path. 1467 IRO Object-Class is to be assigned by IANA (recommended value=10) 1469 IRO Object-Type is to be assigned by IANA (recommended value=1) 1471 0 1 2 3 1472 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 1473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1474 | | 1475 // (Subobjects) // 1476 | | 1477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1479 Figure 18: IRO object body format 1480 Subobjects The IRO object is made of sub-object(s) identical to the 1481 ones defined in [RFC3209], [RFC3473] and [RFC3477] for use in EROs. 1483 The following subobject types are supported. 1485 Type Subobject 1486 1 IPv4 prefix 1487 2 IPv6 prefix 1488 4 Unnumbered Interface ID 1489 32 Autonomous system number 1490 The L bit of such sub-object has no meaning within an IRO object. 1492 7.12. SVEC Object 1494 7.12.1. Notion of Dependent and Synchronized path computation requests 1496 Independent versus dependent path computation requests: path 1497 computation requests are said to be independent if they are not 1498 related to each other. Conversely a set of dependent path 1499 computation requests is such that they MUST be computed 1500 simultaneously: a typical example of dependent requests is the 1501 computation of a set of diverse paths. 1503 Synchronized versus non-synchronized path computation requests: a set 1504 of path computation requests is said to be non-synchronized if their 1505 respective treatment (path computations) can be performed by a PCE in 1506 a serialized and independent fashion. 1508 There are various circumstances where the synchronization of a set of 1509 path computations may be beneficial or required. 1511 Consider the case of a set of N TE LSPs for which a PCC needs to send 1512 path computation requests to a PCE. The first solution consists of 1513 sending N separate PCReq messages to the selected PCE. In this case, 1514 the path computation requests are non synchronized. Note that the 1515 PCC may chose to distribute the set of N requests across K PCEs for 1516 load balancing purpose. Considering that M (with M+-+-+-+-+-+-+ | | 2217 | | | KeepWait |----+ | 2218 | +--| |<---+ | 2219 |+-----+-+-+-+-+-+-+ | | 2220 || | | | 2221 || | | | 2222 || V | | 2223 || +->+-+-+-+-+-+-+----+ | 2224 || | | OpenWait |-------+ 2225 || +--| |<------+ 2226 ||+----+-+-+-+-+-+-+<---+ | 2227 ||| | | | 2228 ||| | | | 2229 ||| V | | 2230 ||| +->+-+-+-+-+-+-+ | | 2231 ||| | |TCPPending |----+ | 2232 ||| +--| | | 2233 |||+---+-+-+-+-+-+-+<---+ | 2234 |||| | | | 2235 |||| | | | 2236 |||| V | | 2237 |||+--->+-+-+-+-+ | | 2238 ||+---->| Idle |-------+ | 2239 |+----->| |----------+ 2240 +------>+-+-+-+-+ 2242 Figure 15: PCEP Finite State Machine for the PCC 2244 PCEP defines the following set of variables: 2246 TCPConnect: timer (in seconds) started after having initialized a TCP 2247 connection using the PCEP well-known TCP port. The value of the 2248 TCPConnect timer is 60 seconds. 2250 TCPRetry: specifies the number of times the system has tried to 2251 establish a TCP connection with a PCEP peer without success. 2253 TCPMaxRetry: Maximum number of times the system tries to establish a 2254 TCP connection using the PCEP well-known TCP port before going back 2255 to the Idle state. The value of the TCPMaxRetry is 5. 2257 OpenWait: timer (in seconds) that corresponds to the amount of time a 2258 PCEP peer will wait to receive an Open message from the PCEP peer 2259 after the expiration of which the system releases the PCEP resource 2260 and go back to the Idle state. 2262 KeepWait: timer that corresponds to the amount of time a PCEP peer 2263 will wait to receive a KeepAlive or a PCErr message from the PCEP 2264 peer after the expiration of which the system releases the PCEP 2265 resource and go back to the Idle state. The KeepWait timer has a 2266 fixed value of 1 minute. 2268 OpenRetry: specifies the number of times the system has received an 2269 Open message with unacceptable PCEP session characteristics. 2271 The following two states variable are defined: 2273 RemoteOK: the RemoteOK variable is a Boolean set to 1 if the system 2274 has received an acceptable Open message. 2276 LocalOK: the LocalOK variable is a Boolean set to 1 if the system has 2277 received a Keepalive message acknowledging that the Open message sent 2278 to the peer was valid. 2280 Idle State: 2282 The idle state is the initial PCEP state where PCEP (also referred to 2283 as "the system") waits for an initialization event that can either be 2284 manually triggered by the user (configuration) or automatically 2285 triggered by various events. In Idle state, PCEP resources are 2286 allocated (memory, potential process, ...) but no PCEP messages are 2287 accepted from any PCEP peer. The system listens the well-known PCEP 2288 TCP port. 2290 The following set of variable are initialized: 2292 TCPRetry=0, 2294 LocalOK=0, 2296 RemoteOK=0, 2298 OpenRetry=0. 2300 Upon detection of a local initialization event (e.g. user 2301 configuration to establish a PCEP session with a particular PCEP 2302 peer, local event triggering the establishment of a PCEP session with 2303 a PCEP peer, ...), the system: 2305 o Starts the TCPConnect timer, 2307 o Initiates of a TCP connection with the PCEP peer, 2309 o Increments the TCPRetry variable, 2311 o Moves to the TCPPending state. 2313 Upon receiving a TCP connection on the well-known PCEP TCP port, if 2314 the PCE is in congested state, the PCE MUST immediately send a PCErr 2315 with Notification-type=2, Notification-value=1 along with the 2316 optional CONGESTION-DURATION TLV (see Section 7.13). 2318 Upon receiving a TCP connection on the well-known PCEP TCP port, if 2319 the TCP connection establishment succeeds, the system: 2321 o Sends an Open message, 2323 o Starts the OpenWait timer, 2325 o Stars the KeepWait timer, 2327 o Moves to the OpenWait state. 2329 It is expected that an implementation will use an exponentially 2330 increase timer between automatically generated Initialization events 2331 and between retrials of TCP connection establishments. 2333 TCPPending State 2335 If the TCP connection establishment succeeds, the system: 2337 o Sends an Open message, 2339 o Starts the OpenWait timer, 2341 o Starts the KeepWait timer, 2343 o Moves to the OpenWait state. 2345 If the TCP connection establishement fails (an error is detected 2346 during the TCP connection establishment) or the TCPConnectTimer 2347 expires: 2349 If TCPRetry =TCPMaxRetry the system moves to the Idle State 2351 If TCPRetry < TCPMaxRetry the system: 2353 o Starts the TCPConnect timer, 2355 o Initiates of a TCP connection with the PCEP peer, 2357 o Increments the TCPRetry variable, 2359 o Stays in the TPCPending state. 2361 If the system detects that the PCEP peer tries to simultaneously 2362 establish a TCP connection, it stops the TCP connection establishment 2363 if and only if the PCEP peer has a higher IP address and moves to the 2364 Idle state. This guarantees that in case of "collision" a single TCP 2365 connection is established. 2367 OpenWait State: 2369 In the OpenWait state, the system waits for an Open message from its 2370 PCEP peer. 2372 If the system receives an Open message from the PCEP peer before the 2373 expiration of the OpenWait timer, PCEP checks the PCEP session 2374 attributes (Keepalive frequency, DeadTimer, ...). 2376 If an error is detected (e.g. malformed Open message, presence of two 2377 Open objects, ...), PCEP generates an error notification, the PCEP 2378 peer sends a PCErr message with Error-Type=1 and Error-value=1. The 2379 system releases the PCEP resources for the PCEP peer, closes the TCP 2380 connection and moves to the Idle state. 2382 If no errors are detected, PCEP increments the OpenRetry variable. 2384 If OpenRetry=2, the PCEP peer sends a PCErr with Error-Type=1 and 2385 Error-value=5, the system releases the PCEP resources for that peer, 2386 and moves back to the Idle state. 2388 If no errors are detected and the session characteristics are 2389 acceptable to the local system, the system: 2391 o Sends a Keepalive message to the PCEP peer, 2393 o Starts the Keepalive timer, 2395 o Sets the RemoteOK variable to 1. 2397 If LocalOK=1 the system moves to the UP state. 2399 If LocalOK=0 the system moves to the KeepWait state. 2401 If no errors are detected but the session charateristics are 2402 unacceptable and non-negotiable, the PCEP peer sends a PCErr with 2403 Error-Type=1 and Error-value=3, the system releases the PCEP 2404 resources for that peer, and moves back to the Idle state. 2406 If no errors are detected, OpenRetry=1, the session charateristics 2407 are unacceptable but negotiable (such as the Keepalive frequency or 2408 the DeadTimer), the system: 2410 o sends a PCErr message with Error-Type=1 and Error-value=4 that 2411 contains proposed acceptable session characteristics, 2413 o If LocalOK=1, the system stays in the OpenWait state 2415 o If LocalOK=0, the system moves to the KeepWait state 2417 If no Open message is received before the expiration of the OpenWait 2418 timer, the PCEP peer sends a PCErr message with Error-Type=1 and 2419 Error-value=2, the system releases the PCEP resources for the PCEP 2420 peer, closes the TCP connection and moves to the Idle state. 2422 KeepWait State 2424 In the Keepwait state, the system waits for the receipt of a 2425 Keepalive from its PCEP peer acknowledging its Open message or a 2426 PCErr message in response to unacceptable PCEP session 2427 characteristics proposed in the Open message. 2429 If a Keepalive message is received before the expiration of the 2430 KeepWait timer, LocalOK=1 2432 If RemoteOK=1, the system moves to the UP state. 2434 If RemoteOK=0, the system moves to the OpenWait State. 2436 If a PCErr message is received before the expiration of the KeepWait 2437 timer: 2439 1. If the proposed values are unacceptable, the PCEP peer sends a 2440 PCErr message with Error-Type=1 and Error-value=6 and the system 2441 releases the PCEP resources for that PCEP peer, closes the TCP 2442 connection and moves to the Idle state. 2444 2. If the proposed values are acceptable, the sytem adjusts its PCEP 2445 session characteristics according to the proposed values received 2446 in the PCErr message restarts the KeepWait timer and sends a new 2447 Open message. If RemoteOK=1, the system stays in the KeepWait 2448 state. If RemoteOK=0, the system moves to the OpenWait state. 2450 If neither a Keepalive nor a PCErr is received after the expiration 2451 of the KeepWait timer, the PCEP peer sends a PCErr message with 2452 Error-Type=1 and Error-value=7 and, system releases the PCEP 2453 resources for that PCEP peer, closes the TCP connection and moves to 2454 the Idle State. 2456 UP State 2458 In the UP state, the PCEP peer starts exchanging PCEP messages 2459 according to the session characteristics. 2461 If the Keepalive timer expires, the systens sends a Keepalive 2462 message. 2464 If no PCEP message (Keepalive, PCReq, PCRep, PCNtf) is received from 2465 the PCEP peer after the expiration of the DeadTimer, the systems 2466 sends a PCErr message with a PCEP-ERROR object (Error-type=9, Error- 2467 value=1), terminates PCEP session according to the procedure defined 2468 in Section 6.8, releases the PCEP resources for that PCEP peer, 2469 closes the TCP connection and moves to the Idle State. 2471 If a malformed PCEP message is received or the TCP connection fails, 2472 the systems sends a PCEP CLOSE message, the system releases the PCEP 2473 resources for that PCEP peer, closes the TCP connection and moves to 2474 the Idle State. 2476 11. Security Considerations 2478 The PCEP protocol could be the target of the following attacks: 2480 o Spoofing (PCC or PCE impersonation) 2482 o Snooping (message interception) 2484 o Falsification 2486 o Denial of Service 2488 A PCEP attack may have significant impact, particularly in an 2489 inter-AS context as PCEP facilitates inter-AS path establishment. 2490 Several mechanisms are proposed below, so as to ensure 2491 authentication, integrity and privacy of PCEP Communications, and 2492 also to protect against DoS attacks. 2494 11.1. PCEP Authentication and Integrity 2496 It is RECOMMENDED to use TCP-MD5 [RFC1321] signature option to 2497 provide for the authenticity and integrity of PCEP messages. This 2498 will allow protecting against PCE or PCC impersonation and also 2499 against message content falsification. 2501 This requires the maintenance, exchange and configuration of MD-5 2502 keys on PCCs and PCEs. Note that such maintenance may be especially 2503 onerous to the operators as pointed out in 2504 [I-D.ietf-rpsec-bgpsecrec]. Hence it is important to limit the 2505 number of keys while ensuring the required level of security. 2507 MD-5 signature faces some limitations, as per explained in [RFC2385]. 2508 Note that when one digest technique stronger than MD5 is specified 2509 and implemented, PCEP could be easily upgraded to use it. 2511 11.2. PCEP Privacy 2513 Ensuring PCEP communication privacy is of key importance, especially 2514 in an inter-AS context, where PCEP communication end-points do not 2515 reside in the same AS, as an attacker that intercept a PCE message 2516 could obtain sensitive information related to computed paths and 2517 resources. Privacy can be ensured thanks to encryption. To ensure 2518 privacy of PCEP communication, IPSec [RFC2406] tunnels MAY be used 2519 between PCC and PCEs or between PCEs. Note that this could also be 2520 used to ensure Authentication and Integrity, in which case, TCP MD-5 2521 option would not be required. 2523 11.3. Protection against Denial of Service attacks 2525 PCEP can be the target of TCP DoS attacks, such as for instance SYN 2526 attacks, as all protocols running on top of TCP. PCEP can use the 2527 same mechanisms as defined in [RFC3036] to mitigate the threat of 2528 such attacks: 2530 o A PCE should avoid promiscuous TCP listens for PCEP TCP session 2531 establishment. It should use only listens that are specific to 2532 authorized PCCs. 2534 o The use of the MD5 option helps somewhat since it prevents a SYN 2535 from being accepted unless the MD5 segment checksum is valid. 2536 However, the receiver must compute the checksum before it can 2537 decide to discard an otherwise acceptable SYN segment. 2539 o The use of access-list on the PCE so as to restrict access to 2540 authorized PCCs. 2542 11.4. Request input shaping/policing 2544 A PCEP implementation may be subject to Denial Of Service attacks 2545 consisting of sending a very large number of PCEP messages (e.g. 2546 PCReq messages). Thus, especially in multi-Service Providers 2547 environments, a PCE implementation should implement request input 2548 shaping/policing so as to throttle the amount of received PCEP 2549 messages without compromising the implementation behavior. 2551 12. Acknowledgements 2553 The authors would like to thank Dave Oran, Dean Cheng, Jerry Ash, 2554 Igor Bryskin, Carol Iturrade, Siva Sivabalan, Rich Bradford, Richard 2555 Douville and Jon Parker for their very valuable input. Special thank 2556 to Adrian Farrel for his very valuable suggestions. 2558 13. References 2560 13.1. Normative References 2562 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2563 Requirement Levels", BCP 14, RFC 2119, March 1997. 2565 [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. 2566 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 2567 Functional Specification", RFC 2205, September 1997. 2569 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 2570 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 2571 Tunnels", RFC 3209, December 2001. 2573 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 2574 (GMPLS) Signaling Resource ReserVation Protocol-Traffic 2575 Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. 2577 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 2578 in Resource ReSerVation Protocol - Traffic Engineering 2579 (RSVP-TE)", RFC 3477, January 2003. 2581 [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute 2582 Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 2583 May 2005. 2585 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 2586 Element (PCE)-Based Architecture", RFC 4655, August 2006. 2588 [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) 2589 Communication Protocol Generic Requirements", RFC 4657, 2590 September 2006. 2592 [RFC4674] Le Roux, J., "Requirements for Path Computation Element 2593 (PCE) Discovery", RFC 4674, October 2006. 2595 13.2. Informative References 2597 [I-D.ietf-ccamp-inter-domain-rsvp-te] 2598 Ayyangar, A. and J. Vasseur, "Inter domain GMPLS Traffic 2599 Engineering - RSVP-TE extensions", 2600 draft-ietf-ccamp-inter-domain-rsvp-te-03 (work in 2601 progress), March 2006. 2603 [I-D.ietf-pce-disco-proto-isis] 2604 Roux, J., "IS-IS protocol extensions for Path Computation 2605 Element (PCE) Discovery", 2606 draft-ietf-pce-disco-proto-isis-00 (work in progress), 2607 September 2006. 2609 [I-D.ietf-pce-disco-proto-ospf] 2610 Roux, J., "OSPF protocol extensions for Path Computation 2611 Element (PCE) Discovery", 2612 draft-ietf-pce-disco-proto-ospf-00 (work in progress), 2613 September 2006. 2615 [I-D.ietf-pce-inter-layer-req] 2616 Oki, E., "PCC-PCE Communication Requirements for Inter- 2617 Layer Traffic Engineering", 2618 draft-ietf-pce-inter-layer-req-02 (work in progress), 2619 June 2006. 2621 [I-D.ietf-pce-interas-pcecp-reqs] 2622 Bitar, N., "Inter-AS Requirements for the Path Computation 2623 Element Communication Protocol (PCECP)", 2624 draft-ietf-pce-interas-pcecp-reqs-00 (work in progress), 2625 August 2006. 2627 [I-D.ietf-pce-pcecp-interarea-reqs] 2628 Roux, J., "PCE Communication Protocol (PCECP) Specific 2629 Requirements for Inter-Area (G)MPLS Traffic Engineering", 2630 draft-ietf-pce-pcecp-interarea-reqs-02 (work in progress), 2631 June 2006. 2633 [I-D.ietf-rpsec-bgpsecrec] 2634 Christian, B. and T. Tauber, "BGP Security Requirements", 2635 draft-ietf-rpsec-bgpsecrec-06 (work in progress), 2636 June 2006. 2638 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 2639 April 1992. 2641 [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 2642 Signature Option", RFC 2385, August 1998. 2644 [RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security 2645 Payload (ESP)", RFC 2406, November 1998. 2647 [RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and 2648 B. Thomas, "LDP Specification", RFC 3036, January 2001. 2650 [RFC3785] Le Faucheur, F., Uppili, R., Vedrenne, A., Merckx, P., and 2651 T. Telkamp, "Use of Interior Gateway Protocol (IGP) Metric 2652 as a second MPLS Traffic Engineering (TE) Metric", BCP 87, 2653 RFC 3785, May 2004. 2655 [RFC4101] Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101, 2656 June 2005. 2658 Appendix A. Compliance with the PCECP Requirement Document 2660 The aim of this section is to list the set of requirements set forth 2661 in [RFC4657] that are not satisfied by the current revision of this 2662 document. This only concerns the requirements listed as MUST 2663 according to [RFC2119]. 2665 Here is the list of currently unsatisfied requirements: 2667 o Allow to select/prefer from advertised list of standard objective 2668 functions/options 2670 o Allow to customize objective function/options 2672 o Support "unsynchronized" & "synchronized" objective functions 2674 o Protocol recovery support resynchronization of information & 2675 requests between sender & receiver. 2677 Appendix B. PCEP Variables 2679 PCEP defines the following configurable variables: 2681 KeepAlive timer: minimum period of time between the sending of PCEP 2682 messages (Keepalive, PCReq, PCRep, PCNtf) to a PCEP peer. A 2683 suggested value for the Keepalive timer is 30 seconds. 2685 DeadTimer: period of timer after the expiration of which a PCEP peer 2686 declared the session down if no PCEP message has been received. 2688 SyncTimer: the SYNC timer is used in the case of synchronized path 2689 computation request using the SVEC object defined in Section 7.12.3. 2690 Consider the case where a PCReq message is received by a PCE that 2691 contains the SVEC object referring to M synchronized path computation 2692 requests. If after the expiration of the SYNC timer all the M path 2693 computation requests have not been received, a protocol error is 2694 triggered and the PCE MUST cancel the whole set of path computation 2695 requests. A RECOMMENDED value for the SYNC timer is 60 seconds. 2697 Authors' Addresses 2699 JP Vasseur (editor) 2700 Cisco Systems, Inc 2701 1414 Massachusetts Avenue 2702 Boxborough, MA 01719 2703 USA 2705 Email: jpv@cisco.com 2707 JL Le Roux 2708 France Telecom 2709 2, Avenue Pierre-Marzin 2710 Lannion, 22307 2711 FRANCE 2713 Email: jeanlouis.leroux@orange-ft.com 2715 Arthi Ayyangar 2716 Nuova Systems 2717 2600 San Tomas Expressway 2718 Santa Clara, CA 95051 2719 USA 2721 Email: arthi@nuovasystems.com 2722 Eiji Oki 2723 NTT 2724 Midori 3-9-11 2725 Musashino, Tokyo, 180-8585 2726 JAPAN 2728 Email: oki.eiji@lab.ntt.co.jp 2730 Alia Atlas 2731 Google 2732 1600 Amphitheatre Parkway 2733 Montain View, CA 94043 2734 USA 2736 Email: akatlas@alum.mit.edu 2738 Andrew Dolganow 2739 Alcatel 2740 600 March Road 2741 Ottawa, ON K2K 2E6 2742 CANADA 2744 Email: andrew.dolganow@alcatel.com 2746 Yuichi Ikejiri 2747 NTT Communications Corporation 2748 1-1-6 Uchisaiwai-cho, Chiyoda-ku 2749 Tokyo, 100-819 2750 JAPAN 2752 Email: y.ikejiri@ntt.com 2754 Kenji Kumaki 2755 KDDI Corporation 2756 Garden Air Tower Iidabashi, Chiyoda-ku, 2757 Tokyo, 102-8460 2758 JAPAN 2760 Email: ke-kumaki@kddi.com 2762 Full Copyright Statement 2764 Copyright (C) The Internet Society (2006). 2766 This document is subject to the rights, licenses and restrictions 2767 contained in BCP 78, and except as set forth therein, the authors 2768 retain all their rights. 2770 This document and the information contained herein are provided on an 2771 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2772 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2773 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2774 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2775 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2776 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2778 Intellectual Property 2780 The IETF takes no position regarding the validity or scope of any 2781 Intellectual Property Rights or other rights that might be claimed to 2782 pertain to the implementation or use of the technology described in 2783 this document or the extent to which any license under such rights 2784 might or might not be available; nor does it represent that it has 2785 made any independent effort to identify any such rights. Information 2786 on the procedures with respect to rights in RFC documents can be 2787 found in BCP 78 and BCP 79. 2789 Copies of IPR disclosures made to the IETF Secretariat and any 2790 assurances of licenses to be made available, or the result of an 2791 attempt made to obtain a general license or permission for the use of 2792 such proprietary rights by implementers or users of this 2793 specification can be obtained from the IETF on-line IPR repository at 2794 http://www.ietf.org/ipr. 2796 The IETF invites any interested party to bring to its attention any 2797 copyrights, patents or patent applications, or other proprietary 2798 rights that may cover technology that may be required to implement 2799 this standard. Please address the information to the IETF at 2800 ietf-ipr@ietf.org. 2802 Acknowledgment 2804 Funding for the RFC Editor function is provided by the IETF 2805 Administrative Support Activity (IASA).