idnits 2.17.1 draft-ietf-pce-stateful-pce-21.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. 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 and authors Copyright Line does not match the current year -- The document date (June 19, 2017) is 2502 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references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 8051 == Outdated reference: A later version (-16) exists of draft-ietf-pce-gmpls-pcep-extensions-11 == Outdated reference: A later version (-11) exists of draft-ietf-pce-pce-initiated-lsp-09 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-02 == Outdated reference: A later version (-18) exists of draft-ietf-pce-pceps-14 -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) -- Obsolete informational reference (is this intentional?): RFC 7525 (Obsoleted by RFC 9325) Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group E. Crabbe 3 Internet-Draft Oracle 4 Intended status: Standards Track I. Minei 5 Expires: December 21, 2017 Google, Inc. 6 J. Medved 7 Cisco Systems, Inc. 8 R. Varga 9 Pantheon Technologies SRO 10 June 19, 2017 12 PCEP Extensions for Stateful PCE 13 draft-ietf-pce-stateful-pce-21 15 Abstract 17 The Path Computation Element Communication Protocol (PCEP) provides 18 mechanisms for Path Computation Elements (PCEs) to perform path 19 computations in response to Path Computation Clients (PCCs) requests. 21 Although PCEP explicitly makes no assumptions regarding the 22 information available to the PCE, it also makes no provisions for PCE 23 control of timing and sequence of path computations within and across 24 PCEP sessions. This document describes a set of extensions to PCEP 25 to enable stateful control of MPLS-TE and GMPLS LSPs via PCEP. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on December 21, 2017. 44 Copyright Notice 46 Copyright (c) 2017 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3. Motivation and Objectives for Stateful PCE . . . . . . . . . 5 65 3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 5 66 3.1.1. Background . . . . . . . . . . . . . . . . . . . . . 5 67 3.1.2. Why a Stateful PCE? . . . . . . . . . . . . . . . . . 6 68 3.1.3. Protocol vs. Configuration . . . . . . . . . . . . . 7 69 3.2. Objectives . . . . . . . . . . . . . . . . . . . . . . . 7 70 4. New Functions to Support Stateful PCEs . . . . . . . . . . . 8 71 5. Overview of Protocol Extensions . . . . . . . . . . . . . . . 9 72 5.1. LSP State Ownership . . . . . . . . . . . . . . . . . . . 9 73 5.2. New Messages . . . . . . . . . . . . . . . . . . . . . . 9 74 5.3. Error Reporting . . . . . . . . . . . . . . . . . . . . . 10 75 5.4. Capability Advertisement . . . . . . . . . . . . . . . . 10 76 5.5. IGP Extensions for Stateful PCE Capabilities 77 Advertisement . . . . . . . . . . . . . . . . . . . . . . 11 78 5.6. State Synchronization . . . . . . . . . . . . . . . . . . 12 79 5.7. LSP Delegation . . . . . . . . . . . . . . . . . . . . . 15 80 5.7.1. Delegating an LSP . . . . . . . . . . . . . . . . . . 15 81 5.7.2. Revoking a Delegation . . . . . . . . . . . . . . . . 16 82 5.7.3. Returning a Delegation . . . . . . . . . . . . . . . 18 83 5.7.4. Redundant Stateful PCEs . . . . . . . . . . . . . . . 18 84 5.7.5. Redelegation on PCE Failure . . . . . . . . . . . . . 19 85 5.8. LSP Operations . . . . . . . . . . . . . . . . . . . . . 19 86 5.8.1. Passive Stateful PCE Path Computation 87 Request/Response . . . . . . . . . . . . . . . . . . 19 88 5.8.2. Switching from Passive Stateful to Active Stateful . 21 89 5.8.3. Active Stateful PCE LSP Update . . . . . . . . . . . 22 90 5.9. LSP Protection . . . . . . . . . . . . . . . . . . . . . 23 91 5.10. PCEP Sessions . . . . . . . . . . . . . . . . . . . . . . 23 92 6. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . . 23 93 6.1. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 24 94 6.2. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 26 95 6.3. The PCErr Message . . . . . . . . . . . . . . . . . . . . 28 96 6.4. The PCReq Message . . . . . . . . . . . . . . . . . . . . 29 97 6.5. The PCRep Message . . . . . . . . . . . . . . . . . . . . 30 98 7. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 30 99 7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 30 100 7.1.1. Stateful PCE Capability TLV . . . . . . . . . . . . . 30 101 7.2. SRP Object . . . . . . . . . . . . . . . . . . . . . . . 31 102 7.3. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 33 103 7.3.1. LSP-IDENTIFIERS TLVs . . . . . . . . . . . . . . . . 35 104 7.3.2. Symbolic Path Name TLV . . . . . . . . . . . . . . . 38 105 7.3.3. LSP Error Code TLV . . . . . . . . . . . . . . . . . 39 106 7.3.4. RSVP Error Spec TLV . . . . . . . . . . . . . . . . . 40 107 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 108 8.1. PCE Capabilities in IGP Advertisements . . . . . . . . . 41 109 8.2. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . 41 110 8.3. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 42 111 8.4. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 42 112 8.5. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 43 113 8.6. Notification Object . . . . . . . . . . . . . . . . . . . 43 114 8.7. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 44 115 8.8. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 44 116 8.9. LSP-ERROR-CODE TLV . . . . . . . . . . . . . . . . . . . 45 117 9. Manageability Considerations . . . . . . . . . . . . . . . . 45 118 9.1. Control Function and Policy . . . . . . . . . . . . . . . 45 119 9.2. Information and Data Models . . . . . . . . . . . . . . . 46 120 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 47 121 9.4. Verifying Correct Operation . . . . . . . . . . . . . . . 47 122 9.5. Requirements on Other Protocols and Functional Components 47 123 9.6. Impact on Network Operation . . . . . . . . . . . . . . . 47 124 10. Security Considerations . . . . . . . . . . . . . . . . . . . 48 125 10.1. Vulnerability . . . . . . . . . . . . . . . . . . . . . 48 126 10.2. LSP State Snooping . . . . . . . . . . . . . . . . . . . 48 127 10.3. Malicious PCE . . . . . . . . . . . . . . . . . . . . . 49 128 10.4. Malicious PCC . . . . . . . . . . . . . . . . . . . . . 49 129 11. Contributing Authors . . . . . . . . . . . . . . . . . . . . 49 130 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50 131 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 50 132 13.1. Normative References . . . . . . . . . . . . . . . . . . 50 133 13.2. Informative References . . . . . . . . . . . . . . . . . 51 134 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 136 1. Introduction 138 [RFC5440] describes the Path Computation Element Communication 139 Protocol (PCEP). PCEP defines the communication between a Path 140 Computation Client (PCC) and a Path Computation Element (PCE), or 141 between PCEs, enabling computation of Multiprotocol Label Switching 142 (MPLS) for Traffic Engineering Label Switched Path (TE LSP) 143 characteristics. Extensions for support of Generalized MPLS (GMPLS) 144 in PCEP are defined in [I-D.ietf-pce-gmpls-pcep-extensions] 145 This document specifies a set of extensions to PCEP to enable 146 stateful control of LSPs within and across PCEP sessions in 147 compliance with [RFC4657]. It includes mechanisms to effect Label 148 Switched Path (LSP) state synchronization between PCCs and PCEs, 149 delegation of control over LSPs to PCEs, and PCE control of timing 150 and sequence of path computations within and across PCEP sessions. 152 Extensions to permit the PCE to drive creation of an LSP are defined 153 in [I-D.ietf-pce-pce-initiated-lsp], which specifies PCE-initiated 154 LSP creation. 156 1.1. Requirements Language 158 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 159 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 160 document are to be interpreted as described in [RFC2119]. 162 2. Terminology 164 This document uses the following terms defined in [RFC5440]: PCC, 165 PCE, PCEP Peer, PCEP Speaker. 167 This document uses the following terms defined in [RFC4655]: TED. 169 This document uses the following terms defined in [RFC3031]: LSP. 171 This document uses the following terms defined in [RFC8051]: Stateful 172 PCE, Passive Stateful PCE, Active Stateful PCE, Delegation, LSP State 173 Database. 175 The following terms are defined in this document: 177 Revocation: an operation performed by a PCC on a previously 178 delegated LSP. Revocation revokes the rights granted to the PCE 179 in the delegation operation. 181 Redelegation Timeout Interval: the period of time a PCC waits for, 182 when a PCEP session is terminated, before revoking LSP delegation 183 to a PCE and attempting to redelegate LSPs associated with the 184 terminated PCEP session to an alternate PCE. The Redelegation 185 Timeout Interval is a PCC-local value that can be either operator- 186 configured or dynamically computed by the PCC based on local 187 policy. 189 State Timeout Interval: the period of time a PCC waits for, when a 190 PCEP session is terminated, before flushing LSP state associated 191 with that PCEP session and reverting to operator-defined default 192 parameters or behaviors. The State Timeout Interval is a PCC- 193 local value that can be either operator-configured or dynamically 194 computed by the PCC based on local policy. 196 LSP State Report: an operation to send LSP state (Operational / 197 Admin Status, LSP attributes configured at the PCC and set by a 198 PCE, etc.) from a PCC to a PCE. 200 LSP Update Request: an operation where an Active Stateful PCE 201 requests a PCC to update one or more attributes of an LSP and to 202 re-signal the LSP with updated attributes. 204 SRP-ID-number: a number used to correlate errors and LSP State 205 Reports to LSP Update Requests. It is carried in the SRP 206 (Stateful PCE Request Parameters) Object described in Section 7.2. 208 Within this document, PCEP communications are described through PCC- 209 PCE relationship. The PCE architecture also supports the PCE-PCE 210 communication, by having the requesting PCE fill the role of a PCC, 211 as usual. 213 The message formats in this document are specified using Routing 214 Backus-Naur Format (RBNF) encoding as specified in [RFC5511]. 216 3. Motivation and Objectives for Stateful PCE 218 3.1. Motivation 220 [RFC8051] presents several use cases, demonstrating scenarios that 221 benefit from the deployment of a stateful PCE. The scenarios apply 222 equally to MPLS-TE and GMPLS deployments. 224 3.1.1. Background 226 Traffic engineering has been a goal of the MPLS architecture since 227 its inception ([RFC3031], [RFC2702], [RFC3346]). In the traffic 228 engineering system provided by [RFC3630], [RFC5305], and [RFC3209] 229 information about network resources utilization is only available as 230 total reserved capacity by traffic class on a per interface basis; 231 individual LSP state is available only locally on each LER for its 232 own LSPs. In most cases, this makes good sense, as distribution and 233 retention of total LSP state for all LERs within in the network would 234 be prohibitively costly. 236 Unfortunately, this visibility in terms of global LSP state may 237 result in a number of issues for some demand patterns, particularly 238 within a common setup and hold priority. This issue affects online 239 traffic engineering systems. 241 A sufficiently over-provisioned system will by definition have no 242 issues routing its demand on the shortest path. However, lowering 243 the degree to which network over-provisioning is required in order to 244 run a healthy, functioning network is a clear and explicit promise of 245 MPLS architecture. In particular, it has been a goal of MPLS to 246 provide mechanisms to alleviate congestion scenarios in which 247 "traffic streams are inefficiently mapped onto available resources; 248 causing subsets of network resources to become over-utilized while 249 others remain underutilized" ([RFC2702]). 251 3.1.2. Why a Stateful PCE? 253 [RFC4655] defines a stateful PCE to be one in which the PCE maintains 254 "strict synchronization between the PCE and not only the network 255 states (in term of topology and resource information), but also the 256 set of computed paths and reserved resources in use in the network." 257 [RFC4655] also expressed a number of concerns with regard to a 258 stateful PCE, specifically: 260 o Any reliable synchronization mechanism would result in significant 261 control plane overhead 263 o Out-of-band TED synchronization would be complex and prone to race 264 conditions 266 o Path calculations incorporating total network state would be 267 highly complex 269 In general, stress on the control plane will be directly proportional 270 to the size of the system being controlled and the tightness of the 271 control loop, and indirectly proportional to the amount of over- 272 provisioning in terms of both network capacity and reservation 273 overhead. 275 Despite these concerns in terms of implementation complexity and 276 scalability, several TE algorithms exist today that have been 277 demonstrated to be extremely effective in large TE systems, providing 278 both rapid convergence and significant benefits in terms of 279 optimality of resource usage [MXMN-TE]. All of these systems share 280 at least two common characteristics: the requirement for both global 281 visibility of a flow (or in this case, a TE LSP) state and for 282 ordered control of path reservations across devices within the system 283 being controlled. While some approaches have been suggested in order 284 to remove the requirements for ordered control (See [MPLS-PC]), these 285 approaches are highly dependent on traffic distribution, and do not 286 allow for multiple simultaneous LSP priorities representing diffserv 287 classes. 289 The use cases described in [RFC8051] demonstrate a need for 290 visibility into global inter-PCC LSP state in PCE path computations, 291 and for PCE control of sequence and timing in altering LSP path 292 characteristics within and across PCEP sessions. 294 3.1.3. Protocol vs. Configuration 296 Note that existing configuration tools and protocols can be used to 297 set LSP state, such as a Command Line Interface (CLI) tool. However, 298 this solution has several shortcomings: 300 o Scale & Performance: configuration operations often have 301 transactional semantics which are typically heavyweight and often 302 require processing of additional configuration portions beyond the 303 state being directly acted upon, with corresponding cost in CPU 304 cycles, negatively impacting both PCC stability LSP update rate 305 capacity. 307 o Security: when a PCC opens a configuration channel allowing a PCE 308 to send configuration, a malicious PCE may take advantage of this 309 ability to take over the PCC. In contrast, the PCEP extensions 310 described in this document only allow a PCE control over a very 311 limited set of LSP attributes. 313 o Interoperability: each vendor has a proprietary information model 314 for configuring LSP state, which limits interoperability of a 315 stateful PCE with PCCs from different vendors. The PCEP 316 extensions described in this document allow for a common 317 information model for LSP state for all vendors. 319 o Efficient State Synchronization: configuration channels may be 320 heavyweight and unidirectional, therefore efficient state 321 synchronization between a PCC and a PCE may be a problem. 323 3.2. Objectives 325 The objectives for the protocol extensions to support stateful PCE 326 described in this document are as follows: 328 o Allow a single PCC to interact with a mix of stateless and 329 stateful PCEs simultaneously using the same protocol, i.e. PCEP. 331 o Support efficient LSP state synchronization between the PCC and 332 one or more active or passive stateful PCEs. 334 o Allow a PCC to delegate control of its LSPs to an active stateful 335 PCE such that a given LSP is under the control of a single PCE at 336 any given time. 338 * A PCC may revoke this delegation at any time during the 339 lifetime of the LSP. If LSP delegation is revoked while the 340 PCEP session is up, the PCC MUST notify the PCE about the 341 revocation. 343 * A PCE may return an LSP delegation at any point during the 344 lifetime of the PCEP session. If LSP delegation is returned by 345 the PCE while the PCEP session is up, the PCE MUST notify the 346 PCC about the returned delegation. 348 o Allow a PCE to control computation timing and update timing across 349 all LSPs that have been delegated to it. 351 o Enable uninterrupted operation of PCC's LSPs in the event of a PCE 352 failure or while control of LSPs is being transferred between 353 PCEs. 355 4. New Functions to Support Stateful PCEs 357 Several new functions are required in PCEP to support stateful PCEs. 358 A function can be initiated either from a PCC towards a PCE (C-E) or 359 from a PCE towards a PCC (E-C). The new functions are: 361 Capability advertisement (E-C,C-E): both the PCC and the PCE must 362 announce during PCEP session establishment that they support PCEP 363 Stateful PCE extensions defined in this document. 365 LSP state synchronization (C-E): after the session between the PCC 366 and a stateful PCE is initialized, the PCE must learn the state of 367 a PCC's LSPs before it can perform path computations or update LSP 368 attributes in a PCC. 370 LSP Update Request (E-C): a PCE requests modification of attributes 371 on a PCC's LSP. 373 LSP State Report (C-E): a PCC sends an LSP state report to a PCE 374 whenever the state of an LSP changes. 376 LSP control delegation (C-E,E-C): a PCC grants to a PCE the right to 377 update LSP attributes on one or more LSPs; the PCE becomes the 378 authoritative source of the LSP's attributes as long as the 379 delegation is in effect (See Section 5.7); the PCC may withdraw 380 the delegation or the PCE may give up the delegation at any time. 382 Similarly to [RFC5440], no assumption is made about the discovery 383 method used by a PCC to discover a set of PCEs (e.g., via static 384 configuration or dynamic discovery) and on the algorithm used to 385 select a PCE. 387 5. Overview of Protocol Extensions 389 5.1. LSP State Ownership 391 In PCEP (defined in [RFC5440]), LSP state and operation are under the 392 control of a PCC (a PCC may be an LSR or a management station). 393 Attributes received from a PCE are subject to PCC's local policy. 394 The PCEP extensions described in this document do not change this 395 behavior. 397 An active stateful PCE may have control of a PCC's LSPs that were 398 delegated to it, but the LSP state ownership is retained by the PCC. 399 In particular, in addition to specifying values for LSP's attributes, 400 an active stateful PCE also decides when to make LSP modifications. 402 Retaining LSP state ownership on the PCC allows for: 404 o a PCC to interact with both stateless and stateful PCEs at the 405 same time 407 o a stateful PCE to only modify a small subset of LSP parameters, 408 i.e. to set only a small subset of the overall LSP state; other 409 parameters may be set by the operator, for example through command 410 line interface (CLI) commands 412 o a PCC to revert delegated LSP to an operator-defined default or to 413 delegate the LSPs to a different PCE, if the PCC get disconnected 414 from a PCE with currently delegated LSPs 416 5.2. New Messages 418 In this document, we define the following new PCEP messages: 420 Path Computation State Report (PCRpt): a PCEP message sent by a PCC 421 to a PCE to report the status of one or more LSPs. Each LSP State 422 Report in a PCRpt message MAY contain the actual LSP's path, 423 bandwidth, operational and administrative status, etc. An LSP 424 Status Report carried on a PCRpt message is also used in 425 delegation or revocation of control of an LSP to/from a PCE. The 426 PCRpt message is described in Section 6.1. 428 Path Computation Update Request (PCUpd): a PCEP message sent by a 429 PCE to a PCC to update LSP parameters, on one or more LSPs. Each 430 LSP Update Request on a PCUpd message MUST contain all LSP 431 parameters that a PCE wishes to be set for a given LSP. An LSP 432 Update Request carried on a PCUpd message is also used to return 433 LSP delegations if at any point PCE no longer desires control of 434 an LSP. The PCUpd message is described in Section 6.2. 436 The new functions defined in Section 4 are mapped onto the new 437 messages as shown in the following table. 439 +----------------------------------------+--------------+ 440 | Function | Message | 441 +----------------------------------------+--------------+ 442 | Capability Advertisement (E-C,C-E) | Open | 443 | State Synchronization (C-E) | PCRpt | 444 | LSP State Report (C-E) | PCRpt | 445 | LSP Control Delegation (C-E,E-C) | PCRpt, PCUpd | 446 | LSP Update Request (E-C) | PCUpd | 447 +----------------------------------------+--------------+ 449 Table 1: New Function to Message Mapping 451 5.3. Error Reporting 453 Error reporting is done using the procedures defined in [RFC5440], 454 and reusing the applicable error types and error values of [RFC5440] 455 wherever appropriate. The current document defines new error values 456 for several error types to cover failures specific to stateful PCE. 458 5.4. Capability Advertisement 460 During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) 461 advertise their support of stateful PCEP extensions. A PCEP Speaker 462 includes the "Stateful PCE Capability" TLV, described in 463 Section 7.1.1, in the OPEN Object to advertise its support for PCEP 464 stateful extensions. The Stateful Capability TLV includes the 'LSP 465 Update' Flag that indicates whether the PCEP Speaker supports LSP 466 parameter updates. 468 The presence of the Stateful PCE Capability TLV in PCC's OPEN Object 469 indicates that the PCC is willing to send LSP State Reports whenever 470 LSP parameters or operational status changes. 472 The presence of the Stateful PCE Capability TLV in PCE's OPEN message 473 indicates that the PCE is interested in receiving LSP State Reports 474 whenever LSP parameters or operational status changes. 476 The PCEP extensions for stateful PCEs MUST NOT be used if one or both 477 PCEP Speakers have not included the Stateful PCE Capability TLV in 478 their respective OPEN message. If the PCEP Speaker on the PCC 479 supports the extensions of this draft but did not advertise this 480 capability, then upon receipt of PCUpd message from the PCE, it MUST 481 generate a PCErr with error-type 19 (Invalid Operation), error-value 482 2 (Attempted LSP Update Request if the stateful PCE capability was 483 not advertised)(see Section 8.5) and it SHOULD terminate the PCEP 484 session. If the PCEP Speaker on the PCE supports the extensions of 485 this draft but did not advertise this capability, then upon receipt 486 of a PCRpt message from the PCC, it MUST generate a PCErr with error- 487 type 19 (Invalid Operation), error-value 5 (Attempted LSP State 488 Report if stateful PCE capability was not advertised) (see 489 Section 8.5) and it SHOULD terminate the PCEP session. 491 LSP delegation and LSP update operations defined in this document may 492 only be used if both PCEP Speakers set the LSP-UPDATE-CAPABILITY Flag 493 in the "Stateful Capability" TLV to 'Updates Allowed (U Flag = 1)'. 494 If this is not the case and LSP delegation or LSP update operations 495 are attempted, then a PCErr with error-type 19 (Invalid Operation) 496 and error-value 1 (Attempted LSP Update Request for a non-delegated 497 LSP) (see Section 8.5) MUST be generated. Note that, even if one of 498 the PCEP speakers does not set the LSP-UPDATE-CAPABILITY flag in its 499 "Stateful Capability" TLV, a PCE can still operate as a passive 500 stateful PCE by accepting LSP State Reports from the PCC in order to 501 build and maintain an up to date view of the state of the PCC's LSPs. 503 5.5. IGP Extensions for Stateful PCE Capabilities Advertisement 505 When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs 506 are either LSRs or servers also participating in the IGP, an 507 effective mechanism for PCE discovery within an IGP routing domain 508 consists of utilizing IGP advertisements. Extensions for the 509 advertisement of PCE Discovery Information are defined for OSPF and 510 for IS-IS in [RFC5088] and [RFC5089] respectively. 512 The PCE-CAP-FLAGS sub-TLV, defined in [RFC5089], is an optional sub- 513 TLV used to advertise PCE capabilities. It MAY be present within the 514 PCED sub-TLV carried by OSPF or IS-IS. [RFC5088] and [RFC5089] 515 provide the description and processing rules for this sub-TLV when 516 carried within OSPF and IS-IS, respectively. 518 The format of the PCE-CAP-FLAGS sub-TLV is included below for easy 519 reference: 521 Type: 5 523 Length: Multiple of 4. 525 Value: This contains an array of units of 32 bit flags with the most 526 significant bit as 0. Each bit represents one PCE capability. 528 PCE capability bits are defined in [RFC5088]. This document defines 529 new capability bits for the stateful PCE as follows: 531 Bit Capability 532 11 Active Stateful PCE capability 533 12 Passive Stateful PCE capability 535 Note that while active and passive stateful PCE capabilities may be 536 advertised during discovery, PCEP Speakers that wish to use stateful 537 PCEP MUST negotiate stateful PCEP capabilities during PCEP session 538 setup, as specified in the current document. A PCC MAY initiate 539 stateful PCEP capability negotiation at PCEP session setup even if it 540 did not receive any IGP PCE capability advertisements. 542 5.6. State Synchronization 544 The purpose of State Synchronization is to provide a checkpoint-in- 545 time state replica of a PCC's LSP state in a PCE. State 546 Synchronization is performed immediately after the Initialization 547 phase ([RFC5440]). 549 During State Synchronization, a PCC first takes a snapshot of the 550 state of its LSPs state, then sends the snapshot to a PCE in a 551 sequence of LSP State Reports. Each LSP State Report sent during 552 State Synchronization has the SYNC Flag in the LSP Object set to 1. 553 The set of LSPs for which state is synchronized with a PCE is 554 determined by the PCC's local configuration (see more details in 555 Section 9.1) and MAY also be determined by stateful PCEP capabilities 556 defined in other documents, such as 557 [I-D.ietf-pce-stateful-sync-optimizations]. 559 The end of synchronization marker is a PCRpt message with the SYNC 560 Flag set to 0 for an LSP Object with PLSP-ID equal to the reserved 561 value 0 (see Section 7.3). In this case, the LSP Object SHOULD NOT 562 include the SYMBOLIC-PATH-NAME TLV and SHOULD include the LSP- 563 IDENTIFIERS TLV with the special value of all zeroes. The PCRpt 564 message MUST include an empty ERO as its intended path and SHOULD NOT 565 include the optional RRO object for its actual path. If the PCC has 566 no state to synchronize, it SHOULD only send the end of 567 synchronization marker. 569 A PCE SHOULD NOT send PCUpd messages to a PCC before State 570 Synchronization is complete. A PCC SHOULD NOT send PCReq messages to 571 a PCE before State Synchronization is complete. This is to allow the 572 PCE to get the best possible view of the network before it starts 573 computing new paths. 575 Either the PCE or the PCC MAY terminate the session using the PCEP 576 session termination procedures during the synchronization phase. If 577 the session is terminated, the PCE MUST clean up state it received 578 from this PCC. The session reestablishment MUST be re-attempted per 579 the procedures defined in [RFC5440], including use of a back-off 580 timer. 582 If the PCC encounters a problem which prevents it from completing the 583 LSP state synchronization, it MUST send a PCErr message with error- 584 type 20 (LSP State Synchronization Error) and error-value 5 585 (indicating an internal PCC error) to the PCE and terminate the 586 session. 588 The PCE does not send positive acknowledgements for properly received 589 synchronization messages. It MUST respond with a PCErr message with 590 error-type 20 (LSP State Synchronization Error) and error-value 1 591 (indicating an error in processing the PCRpt) (see Section 8.5) if it 592 encounters a problem with the LSP State Report it received from the 593 PCC and it MUST terminate the session. 595 A PCE implementing a limit on the resources a single PCC can occupy, 596 MUST send a PCNtf message with Notification Type 4 (Stateful PCE 597 resource limit exceeded) and Notification Value 1 (Entering resource 598 limit exceeded state) in response to the PCRpt message triggering 599 this condition in the synchronization phase and MUST terminate the 600 session. 602 The successful State Synchronization sequence is shown in Figure 1. 604 +-+-+ +-+-+ 605 |PCC| |PCE| 606 +-+-+ +-+-+ 607 | | 608 |-----PCRpt, SYNC=1----->| (Sync start) 609 | | 610 |-----PCRpt, SYNC=1----->| 611 | . | 612 | . | 613 | . | 614 |-----PCRpt, SYNC=1----->| 615 | . | 616 | . | 617 | . | 618 | | 619 |-----PCRpt, SYNC=0----->| (End of sync marker 620 | | LSP State Report 621 | | for PLSP-ID=0) 622 | | (Sync done) 624 Figure 1: Successful state synchronization 626 The sequence where the PCE fails during the State Synchronization 627 phase is shown in Figure 2. 629 +-+-+ +-+-+ 630 |PCC| |PCE| 631 +-+-+ +-+-+ 632 | | 633 |-----PCRpt, SYNC=1----->| 634 | | 635 |-----PCRpt, SYNC=1----->| 636 | . | 637 | . | 638 | . | 639 |-----PCRpt, SYNC=1----->| 640 | | 641 |-PCRpt, SYNC=1 | 642 | \ ,-PCErr | 643 | \ / | 644 | \/ | 645 | /\ | 646 | / `-------->| (Ignored) 647 |<--------` | 649 Figure 2: Failed state synchronization (PCE failure) 651 The sequence where the PCC fails during the State Synchronization 652 phase is shown in Figure 3. 654 +-+-+ +-+-+ 655 |PCC| |PCE| 656 +-+-+ +-+-+ 657 | | 658 |-----PCRpt, SYNC=1----->| 659 | | 660 |-----PCRpt, SYNC=1----->| 661 | . | 662 | . | 663 | . | 664 |-------- PCErr=? ------>| 665 | | 667 Figure 3: Failed state synchronization (PCC failure) 669 Optimizations to the synchronization procedures and alternate 670 mechanisms of providing the synchronization function are outside the 671 scope of this document and are discussed elsewhere (see 672 [I-D.ietf-pce-stateful-sync-optimizations]). 674 5.7. LSP Delegation 676 If during Capability advertisement both the PCE and the PCC have 677 indicated that they support LSP Update, then the PCC may choose to 678 grant the PCE a temporary right to update (a subset of) LSP 679 attributes on one or more LSPs. This is called "LSP Delegation", and 680 it MAY be performed at any time after the Initialization phase, 681 including during the State Synchronization phase. 683 A PCE MAY return an LSP delegation at any time if it no longer wishes 684 to update the LSP's state. A PCC MAY revoke an LSP delegation at any 685 time. Delegation, Revocation, and Return are done individually for 686 each LSP. 688 In the event of a delegation being rejected or returned by a PCE, the 689 PCC SHOULD react based on local policy. It can, for example, either 690 retry delegating to the same PCE using an exponentially increasing 691 timer or delegate to an alternate PCE. 693 5.7.1. Delegating an LSP 695 A PCC delegates an LSP to a PCE by setting the Delegate flag in LSP 696 State Report to 1. If the PCE does not accept the LSP Delegation, it 697 MUST immediately respond with an empty LSP Update Request which has 698 the Delegate flag set to 0. If the PCE accepts the LSP Delegation, 699 it MUST set the Delegate flag to 1 when it sends an LSP Update 700 Request for the delegated LSP (note that this may occur at a later 701 time). The PCE MAY also immediately acknowledge a delegation by 702 sending an empty LSP Update Request which has the Delegate flag set 703 to 1. 705 The delegation sequence is shown in Figure 4. 707 +-+-+ +-+-+ 708 |PCC| |PCE| 709 +-+-+ +-+-+ 710 | | 711 |---PCRpt, Delegate=1--->| LSP Delegated 712 | | 713 |---PCRpt, Delegate=1--->| 714 | . | 715 | . | 716 | . | 717 |<--(PCUpd,Delegate=1)---| Delegation confirmed 718 | | 719 |---PCRpt, Delegate=1--->| 720 | | 722 Figure 4: Delegating an LSP 724 Note that for an LSP to remain delegated to a PCE, the PCC MUST set 725 the Delegate flag to 1 on each LSP State Report sent to the PCE. 727 5.7.2. Revoking a Delegation 729 5.7.2.1. Explicit Revocation 731 When a PCC decides that a PCE is no longer permitted to modify an 732 LSP, it revokes that LSP's delegation to the PCE. A PCC may revoke 733 an LSP delegation at any time during the LSP's life time. A PCC 734 revoking an LSP delegation MAY immediately remove the updated 735 parameters provided by the PCE and revert to the operator-defined 736 parameters, but to avoid traffic loss, it SHOULD do so in a make- 737 before-break fashion. If the PCC has received but not yet acted on 738 PCUpd messages from the PCE for the LSP whose delegation is being 739 revoked, then it SHOULD ignore these PCUpd messages when processing 740 the message queue. All effects of all messages for which processing 741 started before the revocation took place MUST be allowed to complete 742 and the result MUST be given the same treatment as any LSP that had 743 been previously delegated to the PCE (e.g. the state MAY immediately 744 revert to the operator-defined parameters). 746 If a PCEP session with the PCE to which the LSP is delegated exists 747 in the UP state during the revocation, the PCC MUST notify that PCE 748 by sending an LSP State Report with the Delegate flag set to 0, as 749 shown in Figure 5. 751 +-+-+ +-+-+ 752 |PCC| |PCE| 753 +-+-+ +-+-+ 754 | | 755 |---PCRpt, Delegate=1--->| 756 | | 757 |<--(PCUpd,Delegate=1)---| Delegation confirmed 758 | . | 759 | . | 760 | . | 761 |---PCRpt, Delegate=0--->| PCC revokes delegation 762 | | 764 Figure 5: Revoking a Delegation 766 After an LSP delegation has been revoked, a PCE can no longer update 767 LSP's parameters; an attempt to update parameters of a non-delegated 768 LSP will result in the PCC sending a PCErr message with error-type 19 769 (Invalid Operation), error-value 1 (attempted LSP Update Request for 770 a non-delegated LSP) (see Section 8.5). 772 5.7.2.2. Revocation on Redelegation Timeout 774 When a PCC's PCEP session with a PCE terminates unexpectedly, the PCC 775 MUST wait the time interval specified in Redelegation Timeout 776 Interval before revoking LSP delegations to that PCE and attempting 777 to redelegate LSPs to an alternate PCE. If a PCEP session with the 778 original PCE can be reestablished before the Redelegation Timeout 779 Interval timer expires, LSP delegations to the PCE remain intact. 781 Likewise, when a PCC's PCEP session with a PCE terminates 782 unexpectedly, and the PCC does not succeed in redelegating its LSPs, 783 the PCC MUST wait for the State Timeout Interval before flushing any 784 LSP state associated with that PCE. Note that the State Timeout 785 Interval timer may expire before the PCC has redelegated the LSPs to 786 another PCE, for example if a PCC is not connected to any active 787 stateful PCE or if no connected active stateful PCE accepts the 788 delegation. In this case, the PCC MUST flush any LSP state set by 789 the PCE upon expiration of the State Timeout Interval and revert to 790 operator-defined default parameters or behaviors. This operation 791 SHOULD be done in a make-before-break fashion. 793 The State Timeout Interval MUST be greater than or equal to the 794 Redelegation Timeout Interval and MAY be set to infinity (meaning 795 that until the PCC specifically takes action to change the parameters 796 set by the PCE, they will remain intact). 798 5.7.3. Returning a Delegation 800 In order to keep a delegation, a PCE MUST set the Delegate flag to 1 801 on each LSP Update Request sent to the PCC. A PCE that no longer 802 wishes to update an LSP's parameters SHOULD return the LSP delegation 803 back to the PCC by sending an empty LSP Update Request which has the 804 Delegate flag set to 0. If a PCC receives an LSP Update Request with 805 the Delegate flag set to 0 (whether the LSP Update Request is empty 806 or not), it MUST treat this as a delegation return. 808 +-+-+ +-+-+ 809 |PCC| |PCE| 810 +-+-+ +-+-+ 811 | | 812 |---PCRpt, Delegate=1--->| LSP delegated 813 | . | 814 | . | 815 | . | 816 |<--PCUpd, Delegate=0----| Delegation returned 817 | | 818 |---PCRpt, Delegate=0--->| No delegation for LSP 819 | | 821 Figure 6: Returning a Delegation 823 If a PCC cannot delegate an LSP to a PCE (for example, if a PCC is 824 not connected to any active stateful PCE or if no connected active 825 stateful PCE accepts the delegation), the LSP delegation on the PCC 826 will time out within a configurable Redelegation Timeout Interval and 827 the PCC MUST flush any LSP state set by a PCE at the expiration of 828 the State Timeout Interval and revert to operator-defined default 829 parameters or behaviors. 831 5.7.4. Redundant Stateful PCEs 833 In a redundant configuration where one PCE is backing up another PCE, 834 the backup PCE may have only a subset of the LSPs in the network 835 delegated to it. The backup PCE does not update any LSPs that are 836 not delegated to it. In order to allow the backup to operate in a 837 hot-standby mode and avoid the need for state synchronization in case 838 the primary fails, the backup receives all LSP State Reports from a 839 PCC. When the primary PCE for a given LSP set fails, after expiry of 840 the Redelegation Timeout Interval, the PCC SHOULD delegate to the 841 redundant PCE all LSPs that had been previously delegated to the 842 failed PCE. Assuming that the State Timeout Interval had been 843 configured to be greater than the Redelegation Timeout Interval (as 844 MANDATORY), and assuming that the primary and redundant PCEs take 845 similar decisions, this delegation change will not cause any changes 846 to the LSP parameters. 848 5.7.5. Redelegation on PCE Failure 850 On failure, the goal is to: 1) avoid any traffic loss on the LSPs 851 that were updated by the PCE that crashed 2) minimize the churn in 852 the network in terms of ownership of the LSPs, 3) not leave any 853 "orphan" (undelegated) LSPs and 4) be able to control when the state 854 that was set by the PCE can be changed or purged. The values chosen 855 for the Redelegation Timeout and State Timeout values affect the 856 ability to accomplish these goals. 858 This section summarizes the behaviour with regards to LSP delegation 859 and LSP state on a PCE failure. 861 If the PCE crashes but recovers within the Redelegation Timeout, both 862 the delegation state and the LSP state are kept intact. 864 If the PCE crashes but does not recover within the Redelegation 865 Timeout, the delegation state is returned to the PCC. If the PCC can 866 redelegate the LSPs to another PCE, and that PCE accepts the 867 delegations, there will be no change in LSP state. If the PCC cannot 868 redelegate the LSPs to another PCE, then upon expiration of the State 869 Timeout Interval, the state set by the PCE is removed and the LSP 870 reverts to operator-defined parameters, which may cause a change in 871 the LSP state. Note that an operator may choose to use an infinite 872 State Timeout Interval if he wishes to maintain the PCE state 873 indefinitely. Note also that flushing the state should be 874 implemented using make-before-break to avoid traffic loss. 876 If there is a standby PCE, the Redelegation Timeout may be set to 0 877 through policy on the PCC, causing the LSPs to be redelegated 878 immediately to the PCC, which can delegate them immediately to the 879 standby PCE. Assuming that the PCC can redelegate the LSP to the 880 standby PCE within the State Timeout Interval, and assuming the 881 standby PCE takes similar decisions as the failed PCE, the LSP state 882 will be kept intact. 884 5.8. LSP Operations 886 5.8.1. Passive Stateful PCE Path Computation Request/Response 887 +-+-+ +-+-+ 888 |PCC| |PCE| 889 +-+-+ +-+-+ 890 | | 891 1) Path computation |----- PCReq message --->| 892 request sent to | |2) Path computation 893 PCE | | request received, 894 | | path computed 895 | | 896 |<---- PCRep message ----|3) Computed paths 897 | (Positive reply) | sent to the PCC 898 | (Negative reply) | 899 4) LSP State change | | 900 event | | 901 | | 902 5) LSP State Report |----- PCRpt message --->| 903 sent to all | . | 904 stateful PCEs | . | 905 | . | 906 6) Repeat for each |----- PCRpt message --->| 907 LSP state change | | 908 | | 910 Figure 7: Passive Stateful PCE Path Computation Request/Response 912 Once a PCC has successfully established a PCEP session with a passive 913 stateful PCE and the PCC's LSP state is synchronized with the PCE 914 (i.e. the PCE knows about all PCC's existing LSPs), if an event is 915 triggered that requires the computation of a set of paths, the PCC 916 sends a path computation request to the PCE ([RFC5440], 917 Section 4.2.3). The PCReq message MAY contain the LSP Object to 918 identify the LSP for which the path computation is requested. 920 Upon receiving a path computation request from a PCC, the PCE 921 triggers a path computation and returns either a positive or a 922 negative reply to the PCC ([RFC5440], Section 4.2.4). 924 Upon receiving a positive path computation reply, the PCC receives a 925 set of computed paths and starts to setup the LSPs. For each LSP, it 926 MAY send an LSP State Report carried on a PCRpt message to the PCE, 927 indicating that the LSP's status is "Going-up". 929 Once an LSP is up or active, the PCC MUST send an LSP State Report 930 carried on a PCRpt message to the PCE, indicating that the LSP's 931 status is 'Up' or 'Active' respectively. If the LSP could not be set 932 up, the PCC MUST send an LSP State Report indicating that the LSP is 933 "Down' and stating the cause of the failure. Note that due to timing 934 constraints, the LSP status may change from 'Going-up' to 'Up' (or 935 'Down') before the PCC has had a chance to send an LSP State Report 936 indicating that the status is 'Going-up'. In such cases, the PCC MAY 937 choose to only send the PCRpt indicating the latest status ('Active', 938 'Up' or 'Down'). 940 Upon receiving a negative reply from a PCE, a PCC MAY resend a 941 modified request or take any other appropriate action. For each 942 requested LSP, it SHOULD also send an LSP State Report carried on a 943 PCRpt message to the PCE, indicating that the LSP's status is 'Down'. 945 There is no direct correlation between PCRep and PCRpt messages. For 946 a given LSP, multiple LSP State Reports will follow a single PCRep 947 message, as a PCC notifies a PCE of the LSP's state changes. 949 A PCC MUST send each LSP State Report to each stateful PCE that is 950 connected to the PCC. 952 Note that a single PCRpt message MAY contain multiple LSP State 953 Reports. 955 The passive stateful model for stateful PCEs is described in 956 [RFC4655], Section 6.8. 958 5.8.2. Switching from Passive Stateful to Active Stateful 960 This section deals with the scenario of an LSP transitioning from a 961 passive stateful to an active stateful mode of operation. When the 962 LSP has no working path, prior to delegating the LSP, the PCC MUST 963 first use the procedure defined in Section 5.8.1 to request the 964 initial path from the PCE. This is required because the action of 965 delegating the LSP to a PCE using a PCRpt message is not an explicit 966 request to the PCE to compute a path for the LSP. The only explicit 967 way for a PCC to request a path from PCE is to send a PCReq message. 968 The PCRpt message MUST NOT be used by the PCC to attempt to request a 969 path from the PCE. 971 When the LSP is delegated after its setup, it may be useful for the 972 PCC to communicate to the PCE the locally configured intended 973 configuration parameters, so that the PCE may reuse them in its 974 computations. Such parameters MAY be acquired through an out of band 975 channel, or MAY be communicated in the PCRpt message delegating the 976 LSPs, by including them as part of the intented-attribute-list as 977 explained in Section 6.1. An implementation MAY allow policies on 978 the PCC to determine the configuration parameters to be sent to the 979 PCE. 981 5.8.3. Active Stateful PCE LSP Update 983 +-+-+ +-+-+ 984 |PCC| |PCE| 985 +-+-+ +-+-+ 986 | | 987 1) LSP State |-- PCRpt, Delegate=1 -->| 988 Synchronization | . | 989 | . |2) PCE decides to 990 | . | update the LSP 991 | | 992 |<---- PCUpd message ----|3) PCUpd message sent 993 | | to PCC 994 | | 995 | | 996 4) LSP State Report |---- PCRpt message ---->| 997 sent(->Going-up) | . | 998 | . | 999 | . | 1000 5) LSP State Report |---- PCRpt message ---->| 1001 sent (->Up|Down) | | 1002 | | 1004 Figure 8: Active Stateful PCE 1006 Once a PCC has successfully established a PCEP session with an active 1007 stateful PCE, the PCC's LSP state is synchronized with the PCE (i.e. 1008 the PCE knows about all PCC's existing LSPs). After LSPs have been 1009 delegated to the PCE, the PCE can modify LSP parameters of delegated 1010 LSPs. 1012 To update an LSP, a PCE MUST send the PCC an LSP Update Request using 1013 a PCUpd message. The LSP Update Request contains a variety of 1014 objects that specify the set of constraints and attributes for the 1015 LSP's path. Each LSP Update Request MUST have a unique identifier, 1016 the SRP-ID-number, carried in the SRP (Stateful PCE Request 1017 Parameters) Object described in Section 7.2. The SRP-ID-number is 1018 used to correlate errors and state reports to LSP Update Requests. A 1019 single PCUpd message MAY contain multiple LSP Update Requests. 1021 Upon receiving a PCUpd message the PCC starts to setup LSPs specified 1022 in LSP Update Requests carried in the message. For each LSP, it MAY 1023 send an LSP State Report carried on a PCRpt message to the PCE, 1024 indicating that the LSP's status is 'Going-up'. If the PCC decides 1025 that the LSP parameters proposed in the PCUpd message are 1026 unacceptable, it MUST report this error by including the LSP-ERROR- 1027 CODE TLV (Section 7.3.3) with LSP error-value="Unacceptable 1028 parameters" in the LSP object in the PCRpt message to the PCE. Based 1029 on local policy, it MAY react further to this error by revoking the 1030 delegation. If the PCC receives a PCUpd message for an LSP object 1031 identified with a PLSP-ID that does not exist on the PCC, it MUST 1032 generate a PCErr with error-type 19 (Invalid Operation), error-value 1033 3, (Attempted LSP Update Request for an LSP identified by an unknown 1034 PSP-ID) (see Section 8.5). 1036 Once an LSP is up, the PCC MUST send an LSP State Report (PCRpt 1037 message) to the PCE, indicating that the LSP's status is 'Up'. If 1038 the LSP could not be set up, the PCC MUST send an LSP State Report 1039 indicating that the LSP is 'Down' and stating the cause of the 1040 failure. A PCC MAY compress LSP State Reports to only reflect the 1041 most up to date state, as discussed in the previous section. 1043 A PCC MUST send each LSP State Report to each stateful PCE that is 1044 connected to the PCC. 1046 PCErr and PCRpt messages triggered as a result of a PCUpd message 1047 MUST include the SRP-ID-number from the PCUpd. This provides 1048 correlation of requests and errors and acknowledgement of state 1049 processing. The PCC MAY compress state when processing PCUpd. In 1050 this case, receipt of a higher SRP-ID-number implicitly acknowledges 1051 processing all the updates with lower SRP-ID-number for the specific 1052 LSP (as per Section 7.2). 1054 A PCC MUST NOT send to any PCE a Path Computation Request for a 1055 delegated LSP. Should the PCC decide it wants to issue a Path 1056 Computation Request on a delegated LSP, it MUST perform Delegation 1057 Revocation procedure first. 1059 5.9. LSP Protection 1061 LSP protection and interaction with stateful PCE, as well as the 1062 extensions necessary to implement this functionality will be 1063 discussed in a separate document. 1065 5.10. PCEP Sessions 1067 A permanent PCEP session MUST be established between a stateful PCE 1068 and the PCC. In the case of session failure, session reestablishment 1069 MUST be re-attempted per the procedures defined in [RFC5440]. 1071 6. PCEP Messages 1073 As defined in [RFC5440], a PCEP message consists of a common header 1074 followed by a variable-length body made of a set of objects. For 1075 each PCEP message type, a set of rules is defined that specify the 1076 set of objects that the message can carry. 1078 6.1. The PCRpt Message 1080 A Path Computation LSP State Report message (also referred to as 1081 PCRpt message) is a PCEP message sent by a PCC to a PCE to report the 1082 current state of an LSP. A PCRpt message can carry more than one LSP 1083 State Reports. A PCC can send an LSP State Report either in response 1084 to an LSP Update Request from a PCE, or asynchronously when the state 1085 of an LSP changes. The Message-Type field of the PCEP common header 1086 for the PCRpt message is 10. 1088 The format of the PCRpt message is as follows: 1090 ::= 1091 1092 Where: 1094 ::= [] 1096 ::= [] 1097 1098 1099 Where: 1100 ::= 1101 [] 1102 1104 ::=[] 1105 [] 1107 Where: 1108 is represented by the ERO object defined in 1109 section 7.9 of [RFC5440]. 1110 consists of the actual computed and 1111 signaled values of the and objects 1112 defined in [RFC5440]. 1113 is represented by the RRO object defined in 1114 section 7.10 of [RFC5440]. 1115 is the attribute-list defined in 1116 section 6.5 of [RFC5440] and extended by PCEP extensions. 1118 The SRP object (see Section 7.2) is OPTIONAL. If the PCRpt message 1119 is not in response to a PCupd message, the SRP object MAY be omitted. 1120 When the PCC does not include the SRP object, the PCE MUST treat this 1121 as an SRP object with an SRP-ID-number equal to the reserved value 1122 0x00000000. The reserved value 0x00000000 indicates that the state 1123 reported is not as a result of processing a PCUpd message. 1125 If the PCRpt message is in response to a PCUpd message, the SRP 1126 object MUST be included and the value of the SRP-ID-number in the SRP 1127 Object MUST be the same as that sent in the PCUpd message that 1128 triggered the state that is reported. If the PCC compressed several 1129 PCUpd messages for the same LSP by only processing the one with the 1130 highest number, then it should use the SRP-ID-number of that request. 1131 No state compression is allowed for state reporting, e.g. PCRpt 1132 messages MUST NOT be pruned from the PCC's egress queue even if 1133 subsequent operations on the same LSP have been completed before the 1134 PCRpt message has been sent to the TCP stack. The PCC MUST 1135 explicitly report state changes (including removal) for paths it 1136 manages. 1138 The LSP object (see Section 7.3) is REQUIRED, and it MUST be included 1139 in each LSP State Report on the PCRpt message. If the LSP object is 1140 missing, the receiving PCE MUST send a PCErr message with Error- 1141 type=6 (Mandatory Object missing) and Error-value 8 (LSP object 1142 missing). 1144 If the LSP transitioned to non-operational state, the PCC SHOULD 1145 include the LSP-ERROR-TLV (Section 7.3.3) with the relevant LSP Error 1146 Code to report the error to the PCE. 1148 The intended path, represented by the ERO object, is REQUIRED. If 1149 the ERO object is missing, the receiving PCE MUST send a PCErr 1150 message with Error-type=6 (Mandatory Object missing) and Error-value 1151 9 (ERO object missing). The ERO may be empty if the PCE does not 1152 have a path for a delegated LSP. 1154 The actual path, represented by the RRO object, SHOULD be included in 1155 PCRpt by the PCC when the path is up or active, but MAY be omitted if 1156 the path is down due to a signaling error or another failure. 1158 The intended-attribute-list maps to the attribute-list in Section 6.5 1159 of [RFC5440] and is used to convey the requested parameters of the 1160 LSP path. This is needed in order to support the switch from passive 1161 to active stateful PCE as described in Section 5.8.2. When included 1162 as part of the intended-attribute-list, the meaning of the BANDWIDTH 1163 object is the requested bandwidth as intended by the operator. In 1164 this case, the BANDWIDTH Object-Type of 1 SHOULD be used. Similarly, 1165 to indicate a limiting constraint, the METRIC object SHOULD be 1166 included as part of the intended-attribute-list with the B flag set 1167 and with a specific metric value. To indicate the optimization 1168 metric, the METRIC object SHOULD be included as part of the intended- 1169 attribute-list with the B flag unset and the metric value set to 1170 zero. Note that the intended-attribute-list is optional and thus may 1171 be omitted. In this case, the PCE MAY use the values in the actual- 1172 attribute-list as the requested parameters for the path. 1174 The actual-attribute-list consists of the actual computed and 1175 signaled values of the BANDWIDTH and METRIC objects defined in 1176 [RFC5440]. When included as part of the actual-attribute-list, 1177 Object-Type 2 ([RFC5440]) SHOULD be used for the BANDWIDTH object and 1178 the C flag SHOULD be set in the METRIC object ([RFC5440]). 1180 Note that the ordering of intended-path, actual-attribute-list, 1181 actual-path and intended-attribute-list is chosen to retain 1182 compatibility with implementations of an earlier version of this 1183 standard. 1185 A PCE may choose to implement a limit on the resources a single PCC 1186 can occupy. If a PCRpt is received that causes the PCE to exceed 1187 this limit, the PCE MUST notify the PCC using a PCNtf message with 1188 Notification Type 4 (Stateful PCE resource limit exceeded) and 1189 Notification Value 1 (Entering resource limit exceeded state) and 1190 MUST terminate the session. 1192 6.2. The PCUpd Message 1194 A Path Computation LSP Update Request message (also referred to as 1195 PCUpd message) is a PCEP message sent by a PCE to a PCC to update 1196 attributes of an LSP. A PCUpd message can carry more than one LSP 1197 Update Request. The Message-Type field of the PCEP common header for 1198 the PCUpd message is 11. 1200 The format of a PCUpd message is as follows: 1202 ::= 1203 1204 Where: 1206 ::= [] 1208 ::= 1209 1210 1211 Where: 1212 ::= 1214 Where: 1215 is represented by the ERO object defined in 1216 section 7.9 of [RFC5440]. 1217 is the attribute-list defined in [RFC5440] 1218 and extended by PCEP extensions. 1220 There are three mandatory objects that MUST be included within each 1221 LSP Update Request in the PCUpd message: the SRP Object (see 1222 Section 7.2), the LSP object (see Section 7.3) and the ERO object (as 1223 defined in [RFC5440], which represents the intended path. If the SRP 1224 object is missing, the receiving PCC MUST send a PCErr message with 1225 Error-type=6 (Mandatory Object missing) and Error-value=10 (SRP 1226 object missing). If the LSP object is missing, the receiving PCC 1227 MUST send a PCErr message with Error-type=6 (Mandatory Object 1228 missing) and Error-value=8 (LSP object missing). If the ERO object 1229 is missing, the receiving PCC MUST send a PCErr message with Error- 1230 type=6 (Mandatory Object missing) and Error-value=9 (ERO object 1231 missing). 1233 The ERO in the PCUpd may be empty if the PCE cannot find a valid path 1234 for a delegated LSP. One typical situation resulting in this empty 1235 ERO carried in the PCUpd message is that a PCE can no longer find a 1236 strict SRLG-disjoint path for a delegated LSP after a link failure. 1237 The PCC SHOULD implement a local policy to decide the appropriate 1238 action to be taken: either tear down the LSP, or revoke the 1239 delegation and use a locally computed path, or keep the existing LSP. 1241 A PCC only acts on an LSP Update Request if permitted by the local 1242 policy configured by the network manager. Each LSP Update Request 1243 that the PCC acts on results in an LSP setup operation. An LSP 1244 Update Request MUST contain all LSP parameters that a PCE wishes to 1245 be set for the LSP. A PCC MAY set missing parameters from locally 1246 configured defaults. If the LSP specified in the Update Request is 1247 already up, it will be re-signaled. 1249 The PCC SHOULD minimize the traffic interruption, and MAY use the 1250 make-before-break procedures described in [RFC3209] in order to 1251 achieve this goal. If the make-before-break procedures are used, two 1252 paths will briefly co-exist. The PCC MUST send separate PCRpt 1253 messages for each, identified by the LSP-IDENTIFIERS TLV. When the 1254 old path is torn down after the head end switches over the traffic, 1255 this event MUST be reported by sending a PCRpt message with the LSP- 1256 IDENTIFIERS-TLV of the old path and the R bit set. The SRP-ID-number 1257 that the PCC associates with this PCRpt MUST be 0x00000000. Thus, a 1258 make-before-break operation will typically result in at least two 1259 PCRpt messages, one for the new path and one for the removal of the 1260 old path (more messages may be possible if intermediate states are 1261 reported). 1263 If the path setup fails due to an RSVP signaling error, the error is 1264 reported to the PCE. The PCC will not attempt to resignal the path 1265 until it is prompted again by the PCE with a subsequent PCUpd 1266 message. 1268 A PCC MUST respond with an LSP State Report to each LSP Update 1269 Request it processed to indicate the resulting state of the LSP in 1270 the network (even if this processing did not result in changing the 1271 state of the LSP). The SRP-ID-number included in the PCRpt MUST 1272 match that in the PCUpd. A PCC MAY respond with multiple LSP State 1273 Reports to report LSP setup progress of a single LSP. In that case, 1274 the SRP-ID-number MUST be included for the first message, for 1275 subsequent messages the reserved value 0x00000000 SHOULD be used. 1277 Note that a PCC MUST process all LSP Update Requests - for example, 1278 an LSP Update Request is sent when a PCE returns delegation or puts 1279 an LSP into non-operational state. The protocol relies on TCP for 1280 message-level flow control. 1282 If the rate of PCUpd messages sent to a PCC for the same target LSP 1283 exceeds the rate at which the PCC can signal LSPs into the network, 1284 the PCC MAY perform state compression on its ingress queue. The 1285 compression algorithm is based on the fact that each PCUpd request 1286 contains the complete LSP state the PCE wishes to be set and works as 1287 follows: when the PCC starts processing a PCUpd message at the head 1288 of its ingress queue, it may search the queue forward for more recent 1289 PCUpd messages pertaining that particular LSP, prune all but the 1290 latest one from the queue and process only the last one as that 1291 request contains the most up-to-date desired state for the LSP. The 1292 PCC MUST NOT send PCRpt nor PCErr messages for requests which were 1293 pruned from the queue in this way. This compression step may be 1294 performed only while the LSP is not being signaled, e.g. if two PCUpd 1295 arrive for the same LSP in quick succession and the PCC started the 1296 signaling of the changes relevant to the first PCUpd, then it MUST 1297 wait until the signaling finishes (and report the new state via a 1298 PCRpt) before attempting to apply the changes indicated in the second 1299 PCUpd. 1301 Note also that it is up to the PCE to handle inter-LSP dependencies; 1302 for example, if ordering of LSP set-ups is required, the PCE has to 1303 wait for an LSP State Report for a previous LSP before starting the 1304 update of the next LSP. 1306 If the PCUpd cannot be satisfied (for example due to unsupported 1307 object or TLV), the PCC MUST respond with a PCErr message indicating 1308 the failure (see Section 7.3.3). 1310 6.3. The PCErr Message 1312 If the stateful PCE capability has been advertised on the PCEP 1313 session, the PCErr message MAY include the SRP object. If the error 1314 reported is the result of an LSP update request, then the SRP-ID- 1315 number MUST be the one from the PCUpd that triggered the error. If 1316 the error is unsolicited, the SRP object MAY be omitted. This is 1317 equivalent to including an SRP object with SRP-ID-number equal to the 1318 reserved value 0x00000000. 1320 The format of a PCErr message from [RFC5440] is extended as follows: 1322 ::= 1323 ( [] ) | 1324 [] 1326 ::=[] 1328 ::=[ | ] 1329 1331 ::=[] 1333 ::=[] 1335 ::=[] 1337 6.4. The PCReq Message 1339 A PCC MAY include the LSP object in the PCReq message (see 1340 Section 7.3) if the stateful PCE capability has been negotiated on a 1341 PCEP session between the PCC and a PCE. 1343 The definition of the PCReq message from [RFC5440] is extended to 1344 optionally include the LSP object after the END-POINTS object. The 1345 encoding from [RFC5440] will become: 1347 ::= 1348 [] 1349 1350 Where: 1352 ::=[] 1353 ::=[] 1355 ::= 1356 1357 [] 1358 [] 1359 [] 1360 [] 1361 [[]] 1362 [] 1363 [] 1365 6.5. The PCRep Message 1367 A PCE MAY include the LSP object in the PCRep message (see 1368 (Section 7.3) if the stateful PCE capability has been negotiated on a 1369 PCEP session between the PCC and the PCE and the LSP object was 1370 included in the corresponding PCReq message from the PCC. 1372 The definition of the PCRep message from [RFC5440] is extended to 1373 optionally include the LSP object after the RP object. The encoding 1374 from [RFC5440] will become: 1376 ::= 1377 1379 Where: 1381 ::=[] 1383 ::= 1384 [] 1385 [] 1386 [] 1387 [] 1389 7. Object Formats 1391 The PCEP objects defined in this document are compliant with the PCEP 1392 object format defined in [RFC5440]. The P flag and the I flag of the 1393 PCEP objects defined in the current document MUST be set to 0 on 1394 transmission and SHOULD be ignored on receipt since the P and I flags 1395 are exclusively related to path computation requests. 1397 7.1. OPEN Object 1399 This document defines one new optional TLV for use in the OPEN 1400 Object. 1402 7.1.1. Stateful PCE Capability TLV 1404 The STATEFUL-PCE-CAPABILITY TLV is an optional TLV for use in the 1405 OPEN Object for stateful PCE capability advertisement. Its format is 1406 shown in the following figure: 1408 0 1 2 3 1409 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 1410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1411 | Type=16 | Length=4 | 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1413 | Flags |U| 1414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1416 Figure 9: STATEFUL-PCE-CAPABILITY TLV format 1418 The type (16 bits) of the TLV is 16. The length field is 16 bit-long 1419 and has a fixed value of 4. 1421 The value comprises a single field - Flags (32 bits): 1423 U (LSP-UPDATE-CAPABILITY - 1 bit): if set to 1 by a PCC, the U Flag 1424 indicates that the PCC allows modification of LSP parameters; if 1425 set to 1 by a PCE, the U Flag indicates that the PCE is capable of 1426 updating LSP parameters. The LSP-UPDATE-CAPABILITY Flag must be 1427 advertised by both a PCC and a PCE for PCUpd messages to be 1428 allowed on a PCEP session. 1430 Unassigned bits are considered reserved. They MUST be set to 0 on 1431 transmission and MUST be ignored on receipt. 1433 A PCEP speaker operating in passive stateful PCE mode advertises the 1434 stateful PCE capability with the U flag set to 0. A PCEP speaker 1435 operating in active stateful PCE mode advertises the stateful PCE 1436 capability with the U Flag set to 1. 1438 Advertisement of the stateful PCE capability implies support of LSPs 1439 that are signaled via RSVP, as well as the objects, TLVs and 1440 procedures defined in this document. 1442 7.2. SRP Object 1444 The SRP (Stateful PCE Request Parameters) object MUST be carried 1445 within PCUpd messages and MAY be carried within PCRpt and PCErr 1446 messages. The SRP object is used to correlate between update 1447 requests sent by the PCE and the error reports and state reports sent 1448 by the PCC. 1450 SRP Object-Class is 33. 1452 SRP Object-Type is 1. 1454 The format of the SRP object body is shown in Figure 10: 1456 0 1 2 3 1457 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 1458 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1459 | Flags | 1460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1461 | SRP-ID-number | 1462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1463 | | 1464 // Optional TLVs // 1465 | | 1466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1468 Figure 10: The SRP Object format 1470 The SRP object body has a variable length and may contain additional 1471 TLVs. 1473 Flags (32 bits): None defined yet. 1475 SRP-ID-number (32 bits): The SRP-ID-number value in the scope of the 1476 current PCEP session uniquely identify the operation that the PCE has 1477 requested the PCC to perform on a given LSP. The SRP-ID-number is 1478 incremented each time a new request is sent to the PCC, and may wrap 1479 around. 1481 The values 0x00000000 and 0xFFFFFFFF are reserved. 1483 Optional TLVs MAY be included within the SRP object body. The 1484 specification of such TLVs is outside the scope of this document. 1486 Every request to update an LSP receives a new SRP-ID-number. This 1487 number is unique per PCEP session and is incremented each time an 1488 operation is requested from the PCE. Thus, for a given LSP there may 1489 be more than one SRP-ID-number unacknowledged at a given time. The 1490 value of the SRP-ID-number is echoed back by the PCC in PCErr and 1491 PCRpt messages to allow for correlation between requests made by the 1492 PCE and errors or state reports generated by the PCC. If the error 1493 or report were not as a result of a PCE operation (for example in the 1494 case of a link down event), the reserved value of 0x00000000 is used 1495 for the SRP-ID-number. The absence of the SRP object is equivalent 1496 to an SRP object with the reserved value of 0x00000000. An SRP-ID- 1497 number is considered unacknowledged and cannot be reused until a 1498 PCErr or PCRpt arrives with an SRP-ID-number equal or higher for the 1499 same LSP. In case of SRP-ID-number wrapping the last SRP-ID-number 1500 before the wrapping MUST be explicitly acknowledged, to avoid a 1501 situation where SRP-ID-numbers remain unacknowledged after the wrap. 1503 This means that the PCC may need to issue two PCUpd messages on 1504 detecting a wrap. 1506 7.3. LSP Object 1508 The LSP object MUST be present within PCRpt and PCUpd messages. The 1509 LSP object MAY be carried within PCReq and PCRep messages if the 1510 stateful PCE capability has been negotiated on the session. The LSP 1511 object contains a set of fields used to specify the target LSP, the 1512 operation to be performed on the LSP, and LSP Delegation. It also 1513 contains a flag indicating to a PCE that the LSP state 1514 synchronization is in progress. This document focuses on LSPs that 1515 are signaled with RSVP, many of the TLVs used with the LSP object 1516 mirror RSVP state. 1518 LSP Object-Class is 32. 1520 LSP Object-Type is 1. 1522 The format of the LSP object body is shown in Figure 11: 1524 0 1 2 3 1525 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 1526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1527 | PLSP-ID | Flag | O |A|R|S|D| 1528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1529 // TLVs // 1530 | | 1531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1533 Figure 11: The LSP Object format 1535 PLSP-ID (20 bits): A PCEP-specific identifier for the LSP. A PCC 1536 creates a unique PLSP-ID for each LSP that is constant for the 1537 lifetime of a PCEP session. The PCC will advertise the same PLSP-ID 1538 on all PCEP sessions it maintains at a given times. The mapping of 1539 the Symbolic Path Name to PLSP-ID is communicated to the PCE by 1540 sending a PCRpt message containing the SYMBOLIC-PATH-NAME TLV. All 1541 subsequent PCEP messages then address the LSP by the PLSP-ID. The 1542 values of 0 and 0xFFFFF are reserved. Note that the PLSP-ID is a 1543 value that is constant for the lifetime of the PCEP session, during 1544 which time for an RSVP-signaled LSP there might be a different RSVP 1545 identifiers (LSP-id, tunnel-id) allocated to it. 1547 Flags (12 bits), starting from the least significant bit: 1549 D (Delegate - 1 bit): On a PCRpt message, the D Flag set to 1 1550 indicates that the PCC is delegating the LSP to the PCE. On a 1551 PCUpd message, the D flag set to 1 indicates that the PCE is 1552 confirming the LSP Delegation. To keep an LSP delegated to the 1553 PCE, the PCC must set the D flag to 1 on each PCRpt message for 1554 the duration of the delegation - the first PCRpt with the D flag 1555 set to 0 revokes the delegation. To keep the delegation, the PCE 1556 must set the D flag to 1 on each PCUpd message for the duration of 1557 the delegation - the first PCUpd with the D flag set to 0 returns 1558 the delegation. 1560 S (SYNC - 1 bit): The S Flag MUST be set to 1 on each PCRpt sent 1561 from a PCC during State Synchronization. The S Flag MUST be set 1562 to 0 in other messages sent from the PCC. When sending a PCUpd 1563 message, the PCE MUST set the S Flag to 0. 1565 R(Remove - 1 bit): On PCRpt messages the R Flag indicates that the 1566 LSP has been removed from the PCC and the PCE SHOULD remove all 1567 state from its database. Upon receiving an LSP State Report with 1568 the R Flag set to 1 for an RSVP-signaled LSP, the PCE SHOULD 1569 remove all state for the path identified by the LSP-IDENTIFIERS 1570 TLV from its database. When the all-zeros LSP-IDENTIFIERS TLV is 1571 used, the PCE SHOULD remove all state for the PLSP-ID from its 1572 database. When sending a PCUpd message, the PCE MUST set the R 1573 Flag to 0. 1575 A(Administrative - 1 bit): On PCRpt messages, the A Flag indicates 1576 the PCC's target operational status for this LSP. On PCUpd 1577 messages, the A Flag indicates the LSP status that the PCE desires 1578 for this LSP. In both cases, a value of '1' means that the 1579 desired operational state is active, and a value of '0' means that 1580 the desired operational state is inactive. A PCC ignores the A 1581 flag on a PCUpd message unless the operator's policy allows the 1582 PCE to control the corresponding LSP's administrative state. 1584 O(Operational - 3 bits): On PCRpt messages, the O Field represents 1585 the operational status of the LSP. 1587 The following values are defined: 1589 0 - DOWN: not active. 1591 1 - UP: signalled. 1593 2 - ACTIVE: up and carrying traffic. 1595 3 - GOING-DOWN: LSP is being torn down, resources are being 1596 released. 1598 4 - GOING-UP: LSP is being signalled. 1600 5-7 - Reserved: these values are reserved for future use. 1602 Unassigned bits are considered reserved. They MUST be set to 0 on 1603 transmission and MUST be ignored on receipt. When sending a PCUpd 1604 message, the PCE MUST set the O Field to 0. 1606 TLVs that may be included in the LSP Object are described in the 1607 following sections. Other optional TLVs, that are not defined in 1608 this document, MAY also be included within the LSP Object body. 1610 7.3.1. LSP-IDENTIFIERS TLVs 1612 The LSP-IDENTIFIERS TLV MUST be included in the LSP object in PCRpt 1613 messages for RSVP-signaled LSPs. If the TLV is missing, the PCE will 1614 generate an error with error-type 6 (mandatory object missing) and 1615 error-value 11 (LSP-IDENTIFIERS TLV missing) and close the session. 1616 The LSP-IDENTIFIERS TLV MAY be included in the LSP object in PCUpd 1617 messages for RSVP-signaled LSPs. The special value of all zeros for 1618 this TLV is used to refer to all paths pertaining to a particular 1619 PLSP-ID. There are two LSP-IDENTIFIERS TLVs, one for IPv4 and one 1620 for IPv6. 1622 It is the responsibility of the PCC to send to the PCE the 1623 identifiers for each RSVP incarnation of the tunnel. For example, in 1624 a make-before-break scenario, the PCC MUST send a separate PCRpt for 1625 the old and for the reoptimized paths, and explicitly report removal 1626 of any of these paths using the R bit in the LSP object. 1628 The format of the IPV4-LSP-IDENTIFIERS TLV is shown in the following 1629 figure: 1631 0 1 2 3 1632 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 1633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1634 | Type=18 | Length=16 | 1635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1636 | IPv4 Tunnel Sender Address | 1637 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1638 | LSP ID | Tunnel ID | 1639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1640 | Extended Tunnel ID | 1641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1642 | IPv4 Tunnel Endpoint Address | 1643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1645 Figure 12: IPV4-LSP-IDENTIFIERS TLV format 1647 The type (16 bits) of the TLV is 18. The length field is 16 bit-long 1648 and has a fixed value of 16. The value contains the following 1649 fields: 1651 IPv4 Tunnel Sender Address: contains the sender node's IPv4 address, 1652 as defined in [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4 1653 Sender Template Object. 1655 LSP ID: contains the 16-bit 'LSP ID' identifier defined in 1656 [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4 Sender Template 1657 Object. A value of 0 MUST be used if the LSP is not yet signaled. 1659 Tunnel ID: contains the 16-bit 'Tunnel ID' identifier defined in 1660 [RFC3209], Section 4.6.1.1 for the LSP_TUNNEL_IPv4 Session Object. 1662 Extended Tunnel ID: contains the 32-bit 'Extended Tunnel ID' 1663 identifier defined in [RFC3209], Section 4.6.1.1 for the 1664 LSP_TUNNEL_IPv4 Session Object. 1666 IPv4 Tunnel Endpoint Address: contains the egress node's IPv4 1667 address, as defined in [RFC3209], Section 4.6.1.1 for the 1668 LSP_TUNNEL_IPv4 Sender Template Object. 1670 The format of the IPV6-LSP-IDENTIFIERS TLV is shown in the following 1671 figure: 1673 0 1 2 3 1674 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 1675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1676 | Type=19 | Length=52 | 1677 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1678 | | 1679 + + 1680 | IPv6 tunnel sender address | 1681 + (16 octets) + 1682 | | 1683 + + 1684 | | 1685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1686 | LSP ID | Tunnel ID | 1687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1688 | | 1689 + + 1690 | Extended Tunnel ID | 1691 + (16 octets) + 1692 | | 1693 + + 1694 | | 1695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1696 | | 1697 + + 1698 | IPv6 tunnel endpoint address | 1699 + (16 octets) + 1700 | | 1701 + + 1702 | | 1703 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1705 Figure 13: IPV6-LSP-IDENTIFIERS TLV format 1707 The type (16 bits) of the TLV is 19. The length field is 16 bit-long 1708 and has a fixed value of 52. The value contains the following 1709 fields: 1711 IPv6 Tunnel Sender Address: contains the sender node's IPv6 address, 1712 as defined in [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6 1713 Sender Template Object. 1715 LSP ID: contains the 16-bit 'LSP ID' identifier defined in 1716 [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6 Sender Template 1717 Object. A value of 0 MUST be used if the LSP is not yet signaled. 1719 Tunnel ID: contains the 16-bit 'Tunnel ID' identifier defined in 1720 [RFC3209], Section 4.6.1.2 for the LSP_TUNNEL_IPv6 Session Object. 1722 Extended Tunnel ID: contains the 128-bit 'Extended Tunnel ID' 1723 identifier defined in [RFC3209], Section 4.6.1.2 for the 1724 LSP_TUNNEL_IPv6 Session Object. 1726 IPv6 Tunnel Endpoint Address: contains the egress node's IPv6 1727 address, as defined in [RFC3209], Section 4.6.1.2 for the 1728 LSP_TUNNEL_IPv6 Session Object. 1730 The Tunnel ID remains constant over the life time of a tunnel. 1732 7.3.2. Symbolic Path Name TLV 1734 Each LSP MUST have a symbolic path name that is unique in the PCC. 1735 The symbolic path name is a human-readable string that identifies an 1736 LSP in the network. The symbolic path name MUST remain constant 1737 throughout an LSP's lifetime, which may span across multiple 1738 consecutive PCEP sessions and/or PCC restarts. The symbolic path 1739 name MAY be specified by an operator in a PCC's configuration. If 1740 the operator does not specify a unique symbolic name for an LSP, then 1741 the PCC MUST auto-generate one. 1743 The PCE uses the symbolic path name as a stable identifier for the 1744 LSP. If the PCEP session restarts, or the PCC restarts, or the PCC 1745 re-delegates the LSP to a different PCE, the symbolic path name for 1746 the LSP remains constant and can be used to correlate across the PCEP 1747 session instances. 1749 The other protocol identifiers for the LSP cannot reliably be used to 1750 identify the LSP across multiple PCEP sessions, for the following 1751 reasons. 1753 o The PLSP-ID is unique only within the scope of a single PCEP 1754 session. 1756 o The LSP-IDENTIFIERS TLV is only guaranteed to be present for LSPs 1757 that are signalled with RSVP-TE, and may change during the 1758 lifetime of the LSP. 1760 The SYMBOLIC-PATH-NAME TLV MUST be included in the LSP object in the 1761 LSP State Report (PCRpt) message when during a given PCEP session an 1762 LSP is first reported to a PCE. A PCC sends to a PCE the first LSP 1763 State Report either during State Synchronization, or when a new LSP 1764 is configured at the PCC. 1766 The initial PCRpt creates a binding between the symbolic path name 1767 and the PLSP-ID for the LSP which lasts for the duration of the PCEP 1768 session. The PCC MAY omit the symbolic path name from subsequent LSP 1769 State Reports for that LSP on that PCEP session, and just use the 1770 PLSP-ID. 1772 The format of the SYMBOLIC-PATH-NAME TLV is shown in the following 1773 figure: 1775 0 1 2 3 1776 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 1777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1778 | Type=17 | Length (variable) | 1779 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1780 | | 1781 // Symbolic Path Name // 1782 | | 1783 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1785 Figure 14: SYMBOLIC-PATH-NAME TLV format 1787 Type (16 bits): The type is 17. 1789 Length (16 bits): indicates the total length of the TLV in octets and 1790 MUST be greater than 0. The TLV MUST be zero-padded so that the TLV 1791 is 4-octet aligned. 1793 Symbolic Path Name (variable): symbolic name for the LSP, unique in 1794 the PCC. It SHOULD be a string of printable ASCII characters, 1795 without a NULL terminator. 1797 7.3.3. LSP Error Code TLV 1799 The LSP Error code TLV is an optional TLV for use in the LSP object 1800 to convey error information. When an LSP Update Request fails, an 1801 LSP State Report MUST be sent to report the current state of the LSP, 1802 and SHOULD contain the LSP-ERROR-CODE TLV indicating the reason for 1803 the failure. Similarly, when a PCRpt is sent as a result of an LSP 1804 transitioning to non-operational state, the LSP-ERROR-CODE TLV SHOULD 1805 be included to indicate the reason for the transition. 1807 The format of the LSP-ERROR-CODE TLV is shown in the following 1808 figure: 1810 0 1 2 3 1811 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 1812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1813 | Type=20 | Length=4 | 1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1815 | LSP Error Code | 1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1818 Figure 15: LSP-ERROR-CODE TLV format 1820 The type (16 bits) of the TLV is 20. The length field is 16 bit-long 1821 and has a fixed value of 4. The value contains an error code that 1822 indicates the cause of the failure. 1824 The following LSP Error Codes are currently defined: 1826 Value Meaning 1827 1 Unknown reason 1828 2 Limit reached for PCE-controlled LSPs 1829 3 Too many pending LSP update requests 1830 4 Unacceptable parameters 1831 5 Internal error 1832 6 LSP administratively brought down 1833 7 LSP preempted 1834 8 RSVP signaling error 1836 7.3.4. RSVP Error Spec TLV 1838 The RSVP-ERROR-SPEC TLV is an optional TLV for use in the LSP object 1839 to carry RSVP error information. It includes the RSVP ERROR_SPEC or 1840 USER_ERROR_SPEC Object ([RFC2205] and [RFC5284]) which were returned 1841 to the PCC from a downstream node. If the set up of an LSP fails at 1842 a downstream node which returned an ERROR_SPEC to the PCC, the PCC 1843 SHOULD include in the PCRpt for this LSP the LSP-ERROR-CODE TLV with 1844 LSP Error Code = "RSVP signaling error" and the RSVP-ERROR-SPEC TLV 1845 with the relevant RSVP ERROR-SPEC or USER_ERROR_SPEC Object. 1847 The format of the RSVP-ERROR-SPEC TLV is shown in the following 1848 figure: 1850 0 1 2 3 1851 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 1852 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1853 | Type=21 | Length (variable) | 1854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1855 | | 1856 + RSVP ERROR_SPEC or USER_ERROR_SPEC Object + 1857 | | 1858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1860 Figure 16: RSVP-ERROR-SPEC TLV format 1862 Type (16 bits): The type is 21. 1864 Length (16 bits): indicates the total length of the TLV in octets. 1865 The TLV MUST be zero-padded so that the TLV is 4-octet aligned. 1867 Value (variable): contains the RSVP ERROR_SPEC or USER_ERROR_SPEC 1868 Object: as specified in [RFC2205] and [RFC5284], including the object 1869 header. 1871 8. IANA Considerations 1873 This document requests IANA actions to allocate code points for the 1874 protocol elements defined in this document. 1876 8.1. PCE Capabilities in IGP Advertisements 1878 IANA is requested to confirm the early allocation of the following 1879 bits in the OSPF Parameters "PCE Capability Flags" registry, and to 1880 update the reference in the registry to point to this document, when 1881 it is an RFC: 1883 Bit Meaning Reference 1884 11 Active Stateful PCE This document 1885 capability 1886 12 Passive Stateful PCE This document 1887 capability 1889 8.2. PCEP Messages 1891 IANA is requested to confirm the early allocation of the following 1892 message types within the "PCEP Messages" sub-registry of the PCEP 1893 Numbers registry, and to update the reference in the registry to 1894 point to this document, when it is an RFC: 1896 Value Meaning Reference 1897 10 Report This document 1898 11 Update This document 1900 8.3. PCEP Objects 1902 IANA is requested to confirm the early allocation of the following 1903 object-class values and object types within the "PCEP Objects" sub- 1904 registry of the PCEP Numbers registry, and to update the reference in 1905 the registry to point to this document, when it is an RFC:. 1907 Object-Class Value Name Reference 1909 32 LSP This document 1910 Object-Type 1911 1 1912 33 SRP This document 1913 Object-Type 1914 1 1916 8.4. LSP Object 1918 This document requests that a new sub-registry, named "LSP Object 1919 Flag Field", is created within the "Path Computation Element Protocol 1920 (PCEP) Numbers" registry to manage the Flag field of the LSP object. 1921 New values are to be assigned by Standards Action [RFC5226]. Each 1922 bit should be tracked with the following qualities: 1924 o Bit number (counting from bit 0 as the most significant bit) 1926 o Capability description 1928 o Defining RFC 1930 The following values are defined in this document: 1932 Bit Description Reference 1934 0-4 Reserved This document 1935 5-7 Operational (3 bits) This document 1936 8 Administrative This document 1937 9 Remove This document 1938 10 SYNC This document 1939 11 Delegate This document 1941 8.5. PCEP-Error Object 1943 IANA is requested to confirm the early allocation of the following 1944 Error Types and Error Values within the "PCEP-ERROR Object Error 1945 Types and Values" sub-registry of the PCEP Numbers registry, and to 1946 update the reference in the registry to point to this document, when 1947 it is an RFC: 1949 Error-Type Meaning 1950 6 Mandatory Object missing 1952 Error-value=8: LSP Object missing 1953 Error-value=9: ERO Object missing 1954 Error-value=10: SRP Object missing 1955 Error-value=11: LSP-IDENTIFIERS TLV missing 1956 19 Invalid Operation 1958 Error-value=1: Attempted LSP Update Request for a non- 1959 delegated LSP. The PCEP-ERROR Object 1960 is followed by the LSP Object that 1961 identifies the LSP. 1962 Error-value=2: Attempted LSP Update Request if the 1963 stateful PCE capability was not 1964 advertised. 1965 Error-value=3: Attempted LSP Update Request for an LSP 1966 identified by an unknown PLSP-ID. 1967 Error-value=5: Attempted LSP State Report if stateful 1968 PCE capability was not advertised. 1969 20 LSP State synchronization error. 1971 Error-value=1: A PCE indicates to a PCC that it can 1972 not process (an otherwise valid) LSP 1973 State Report. The PCEP-ERROR Object is 1974 followed by the LSP Object that 1975 identifies the LSP. 1976 Error-value=5: A PCC indicates to a PCE that it can 1977 not complete the state synchronization, 1979 8.6. Notification Object 1981 IANA is requested to confirm the early allocation of the following 1982 Notification Types and Notification Values within the "Notification 1983 Object" sub-registry of the PCEP Numbers registry, and to update the 1984 reference in the registry to point to this document, when it is an 1985 RFC: 1987 Notification-Type Meaning 1988 4 Stateful PCE resource limit exceeded 1990 Notification-value=1: Entering resource limit 1991 exceeded state 1993 Note to IANA: the early allocation included an additional 1994 Notification value 2 for "Exiting resource limit exceeded state". 1995 This Notification value is no longer required. 1997 8.7. PCEP TLV Type Indicators 1999 IANA is requested to confirm the early allocation of the following 2000 TLV Type Indicator values within the "PCEP TLV Type Indicators" sub- 2001 registry of the PCEP Numbers registry, and to update the reference in 2002 the registry to point to this document, when it is an RFC: 2004 Value Meaning Reference 2005 16 STATEFUL-PCE-CAPABILITY This document 2006 17 SYMBOLIC-PATH-NAME This document 2007 18 IPV4-LSP-IDENTIFIERS This document 2008 19 IPV6-LSP-IDENTIFIERS This document 2009 20 LSP-ERROR-CODE This document 2010 21 RSVP-ERROR-SPEC This document 2012 8.8. STATEFUL-PCE-CAPABILITY TLV 2014 This document requests that a new sub-registry, named "STATEFUL-PCE- 2015 CAPABILITY TLV Flag Field", is created within the "Path Computation 2016 Element Protocol (PCEP) Numbers" registry to manage the Flag field in 2017 the STATEFUL-PCE-CAPABILITY TLV of the PCEP OPEN object (class = 1). 2018 New values are to be assigned by Standards Action [RFC5226]. Each 2019 bit should be tracked with the following qualities: 2021 o Bit number (counting from bit 0 as the most significant bit) 2023 o Capability description 2025 o Defining RFC 2027 The following values are defined in this document: 2029 Bit Description Reference 2031 31 LSP-UPDATE-CAPABILITY This document 2033 8.9. LSP-ERROR-CODE TLV 2035 This document requests that a new sub-registry, named "LSP-ERROR-CODE 2036 TLV Error Code Field", is created within the "Path Computation 2037 Element Protocol (PCEP) Numbers" registry to manage the LSP Error 2038 code field of the LSP-ERROR-CODE TLV. This field specifies the 2039 reason for failure to update the LSP. 2041 New values are to be assigned by Standards Action [RFC5226]. Each 2042 value should be tracked with the following qualities: value, 2043 description and defining RFC. The following values are defined in 2044 this document: 2046 Value Meaning 2047 1 Unknown reason 2048 2 Limit reached for PCE-controlled LSPs 2049 3 Too many pending LSP update requests 2050 4 Unacceptable parameters 2051 5 Internal error 2052 6 LSP administratively brought down 2053 7 LSP preempted 2054 8 RSVP signaling error 2056 9. Manageability Considerations 2058 All manageability requirements and considerations listed in [RFC5440] 2059 apply to PCEP extensions defined in this document. In addition, 2060 requirements and considerations listed in this section apply. 2062 9.1. Control Function and Policy 2064 In addition to configuring specific PCEP session parameters, as 2065 specified in [RFC5440], Section 8.1, a PCE or PCC implementation MUST 2066 allow configuring the stateful PCEP capability and the LSP Update 2067 capability. A PCC implementation SHOULD allow the operator to 2068 specify multiple candidate PCEs for and a delegation preference for 2069 each candidate PCE. A PCC SHOULD allow the operator to specify an 2070 LSP delegation policy where LSPs are delegated to the most-preferred 2071 online PCE. A PCC MAY allow the operator to specify different LSP 2072 delegation policies. 2074 A PCC implementation which allows concurrent connections to multiple 2075 PCEs SHOULD allow the operator to group the PCEs by administrative 2076 domains and it MUST NOT advertise LSP existence and state to a PCE if 2077 the LSP is delegated to a PCE in a different group. 2079 A PCC implementation SHOULD allow the operator to specify whether the 2080 PCC will advertise LSP existence and state for LSPs that are not 2081 controlled by any PCE (for example, LSPs that are statically 2082 configured at the PCC). 2084 A PCC implementation SHOULD allow the operator to specify both the 2085 Redelegation Timeout Interval and the State Timeout Interval. The 2086 default value of the Redelegation Timeout Interval SHOULD be set to 2087 30 seconds. An operator MAY also configure a policy that will 2088 dynamically adjust the Redelegation Timeout Interval, for example 2089 setting it to zero when the PCC has an established session to a 2090 backup PCE. The default value for the State Timeout Interval SHOULD 2091 be set to 60 seconds. 2093 After the expiration of the State Timeout Interval, the LSP reverts 2094 to operator-defined default parameters. A PCC implementation MUST 2095 allow the operator to specify the default LSP parameters. To achieve 2096 a behavior where the LSP retains the parameters set by the PCE until 2097 such time that the PCC makes a change to them, a State Timeout 2098 Interval of infinity SHOULD be used. Any changes to LSP parameters 2099 SHOULD be done in make-before-break fashion. 2101 LSP Delegation is controlled by operator-defined policies on a PCC. 2102 LSPs are delegated individually - different LSPs may be delegated to 2103 different PCEs. An LSP is delegated to at most one PCE at any given 2104 point in time. A PCC implementation SHOULD support the delegation 2105 policy, when all PCC's LSPs are delegated to a single PCE at any 2106 given time. Conversely, the policy revoking the delegation for all 2107 PCC's LSPs SHOULD also be supported. 2109 A PCC implementation SHOULD allow the operator to specify delegation 2110 priority for PCEs. This effectively defines the primary PCE and one 2111 or more backup PCEs to which primary PCE's LSPs can be delegated when 2112 the primary PCE fails. 2114 Policies defined for stateful PCEs and PCCs should eventually fit in 2115 the Policy-Enabled Path Computation Framework defined in [RFC5394], 2116 and the framework should be extended to support Stateful PCEs. 2118 9.2. Information and Data Models 2120 The PCEP YANG module [I-D.ietf-pce-pcep-yang] should include 2122 o advertised stateful capabilities and synchronization status per 2123 PCEP session 2125 o the delegation status of each configured LSP. 2127 The PCEP MIB [RFC7420] could also be updated to include this 2128 information. 2130 9.3. Liveness Detection and Monitoring 2132 PCEP extensions defined in this document do not require any new 2133 mechanisms beyond those already defined in [RFC5440], Section 8.3. 2135 9.4. Verifying Correct Operation 2137 Mechanisms defined in [RFC5440], Section 8.4 also apply to PCEP 2138 extensions defined in this document. In addition to monitoring 2139 parameters defined in [RFC5440], a stateful PCC-side PCEP 2140 implementation SHOULD provide the following parameters: 2142 o Total number of LSP updates 2144 o Number of successful LSP updates 2146 o Number of dropped LSP updates 2148 o Number of LSP updates where LSP setup failed 2150 A PCC implementation SHOULD provide a command to show for each LSP 2151 whether it is delegated, and if so, to which PCE. 2153 A PCC implementation SHOULD allow the operator to manually revoke LSP 2154 delegation. 2156 9.5. Requirements on Other Protocols and Functional Components 2158 PCEP extensions defined in this document do not put new requirements 2159 on other protocols. 2161 9.6. Impact on Network Operation 2163 Mechanisms defined in [RFC5440], Section 8.6 also apply to PCEP 2164 extensions defined in this document. 2166 Additionally, a PCEP implementation SHOULD allow a limit to be placed 2167 on the number of LSPs delegated to the PCE and on the rate of PCUpd 2168 and PCRpt messages sent by a PCEP speaker and processed from a peer. 2169 It SHOULD also allow sending a notification when a rate threshold is 2170 reached. 2172 A PCC implementation SHOULD allow a limit to be placed on the rate of 2173 LSP Updates to the same LSP to avoid signaling overload discussed in 2174 Section 10.3. 2176 10. Security Considerations 2178 10.1. Vulnerability 2180 This document defines extensions to PCEP to enable stateful PCEs. 2181 The nature of these extensions and the delegation of path control to 2182 PCEs results in more information being available for a hypothetical 2183 adversary and a number of additional attack surfaces which must be 2184 protected. 2186 The security provisions described in [RFC5440] remain applicable to 2187 these extensions. However, because the protocol modifications 2188 outlined in this document allow the PCE to control path computation 2189 timing and sequence, the PCE defense mechanisms described in 2190 [RFC5440] section 7.2 are also now applicable to PCC security. 2192 As a general precaution, it is RECOMMENDED that these PCEP extensions 2193 only be activated on authenticated and encrypted sessions across PCEs 2194 and PCCs belonging to the same administrative authority, using 2195 Transport Layer Security (TLS) [I-D.ietf-pce-pceps], as per the 2196 recommendations and best current practices in [RFC7525]. 2198 The following sections identify specific security concerns that may 2199 result from the PCEP extensions outlined in this document along with 2200 recommended mechanisms to protect PCEP infrastructure against related 2201 attacks. 2203 10.2. LSP State Snooping 2205 The stateful nature of this extension explicitly requires LSP status 2206 updates to be sent from PCC to PCE. While this gives the PCE the 2207 ability to provide more optimal computations to the PCC, it also 2208 provides an adversary with the opportunity to eavesdrop on decisions 2209 made by network systems external to PCE. This is especially true if 2210 the PCC delegates LSPs to multiple PCEs simultaneously. 2212 Adversaries may gain access to this information by eavesdropping on 2213 unsecured PCEP sessions, and might then use this information in 2214 various ways to target or optimize attacks on network infrastructure. 2215 For example by flexibly countering anti-DDoS measures being taken to 2216 protect the network, or by determining choke points in the network 2217 where the greatest harm might be caused. 2219 PCC implementations which allow concurrent connections to multiple 2220 PCEs SHOULD allow the operator to group the PCEs by administrative 2221 domains and they MUST NOT advertise LSP existence and state to a PCE 2222 if the LSP is delegated to a PCE in a different group. 2224 10.3. Malicious PCE 2226 The LSP delegation mechanism described in this document allows a PCC 2227 to grant effective control of an LSP to the PCE for the duration of a 2228 PCEP session. While this enables PCE control of the timing and 2229 sequence of path computations within and across PCEP sessions, it 2230 also introduces a new attack vector: an attacker may flood the PCC 2231 with PCUpd messages at a rate which exceeds either the PCC's ability 2232 to process them or the network's ability to signal the changes, 2233 either by spoofing messages or by compromising the PCE itself. 2235 A PCC is free to revoke an LSP delegation at any time without needing 2236 any justification. A defending PCC can do this by enqueueing the 2237 appropriate PCRpt message. As soon as that message is enqueued in 2238 the session, the PCC is free to drop any incoming PCUpd messages 2239 without additional processing. 2241 10.4. Malicious PCC 2243 A stateful session also results in an increased attack surface by 2244 placing a requirement for the PCE to keep an LSP state replica for 2245 each PCC. It is RECOMMENDED that PCE implementations provide a limit 2246 on resources a single PCC can occupy. A PCE implementing such a 2247 limit MUST send a PCNtf message with notification-type 4 (Stateful 2248 PCE resource limit exceeded) and notification-value 1 (Entering 2249 resource limit exceeded state) upon receiving an LSP state report 2250 causing it to exceed this threshold. 2252 Delegation of LSPs can create further strain on PCE resources and a 2253 PCE implementation MAY preemptively give back delegations if it finds 2254 itself lacking the resources needed to effectively manage the 2255 delegation. Since the delegation state is ultimately controlled by 2256 the PCC, PCE implementations SHOULD provide throttling mechanisms to 2257 prevent strain created by flaps of either a PCEP session or an LSP 2258 delegation. 2260 11. Contributing Authors 2262 Xian Zhang 2263 Huawei Technology 2264 F3-5-B R&D Center 2265 Huawei Industrial Base, Bantian, Longgang District 2266 Shenzhen, Guangdong 518129 2267 P.R.China 2268 EMail: zhang.xian@huawei.com 2270 Dhruv Dhody 2271 Huawei Technology 2272 Leela Palace 2273 Bangalore, Karnataka 560008 2274 INDIA 2275 EMail: dhruv.dhody@huawei.com 2277 Siva Sivabalan 2278 Cisco Systems, Inc. 2279 2000 Innovation Drive 2280 Kanata, Ontario K2K 3E8 2281 Canada 2282 EMail: msiva@cisco.com 2284 12. Acknowledgements 2286 We would like to thank Adrian Farrel, Cyril Margaria and Ramon 2287 Casellas for their contributions to this document. 2289 We would like to thank Shane Amante, Julien Meuric, Kohei Shiomoto, 2290 Paul Schultz and Raveendra Torvi for their comments and suggestions. 2291 Thanks also to Jon Hardwick, Oscar Gonzales de Dios, Tomas Janciga, 2292 Stefan Kobza, Kexin Tang, Matej Spanik, Jon Parker, Marek Zavodsky, 2293 Ambrose Kwong, Ashwin Sampath, Calvin Ying, Mustapha Aissaoui, 2294 Stephane Litkowski and Olivier Dugeon for helpful comments and 2295 discussions. 2297 13. References 2299 13.1. Normative References 2301 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2302 Requirement Levels", BCP 14, RFC 2119, 2303 DOI 10.17487/RFC2119, March 1997, 2304 . 2306 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. 2307 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 2308 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, 2309 September 1997, . 2311 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 2312 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 2313 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 2314 . 2316 [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. 2317 Zhang, "OSPF Protocol Extensions for Path Computation 2318 Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088, 2319 January 2008, . 2321 [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. 2322 Zhang, "IS-IS Protocol Extensions for Path Computation 2323 Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089, 2324 January 2008, . 2326 [RFC5284] Swallow, G. and A. Farrel, "User-Defined Errors for RSVP", 2327 RFC 5284, DOI 10.17487/RFC5284, August 2008, 2328 . 2330 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 2331 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 2332 DOI 10.17487/RFC5440, March 2009, 2333 . 2335 [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax 2336 Used to Form Encoding Rules in Various Routing Protocol 2337 Specifications", RFC 5511, DOI 10.17487/RFC5511, April 2338 2009, . 2340 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 2341 Stateful Path Computation Element (PCE)", RFC 8051, 2342 DOI 10.17487/RFC8051, January 2017, 2343 . 2345 13.2. Informative References 2347 [I-D.ietf-pce-gmpls-pcep-extensions] 2348 Margaria, C., Dios, O., and F. Zhang, "PCEP extensions for 2349 GMPLS", draft-ietf-pce-gmpls-pcep-extensions-11 (work in 2350 progress), October 2015. 2352 [I-D.ietf-pce-pce-initiated-lsp] 2353 Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 2354 Extensions for PCE-initiated LSP Setup in a Stateful PCE 2355 Model", draft-ietf-pce-pce-initiated-lsp-09 (work in 2356 progress), March 2017. 2358 [I-D.ietf-pce-pcep-yang] 2359 Dhody, D., Hardwick, J., Beeram, V., and j. 2360 jefftant@gmail.com, "A YANG Data Model for Path 2361 Computation Element Communications Protocol (PCEP)", 2362 draft-ietf-pce-pcep-yang-02 (work in progress), March 2363 2017. 2365 [I-D.ietf-pce-pceps] 2366 Lopez, D., Dios, O., Wu, Q., and D. Dhody, "Secure 2367 Transport for PCEP", draft-ietf-pce-pceps-14 (work in 2368 progress), May 2017. 2370 [I-D.ietf-pce-stateful-sync-optimizations] 2371 Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 2372 and D. Dhody, "Optimizations of Label Switched Path State 2373 Synchronization Procedures for a Stateful PCE", draft- 2374 ietf-pce-stateful-sync-optimizations-10 (work in 2375 progress), March 2017. 2377 [MPLS-PC] Chaieb, I., Le Roux, JL., and B. Cousin, "Improved MPLS-TE 2378 LSP Path Computation using Preemption", Global 2379 Information Infrastructure Symposium, July 2007. 2381 [MXMN-TE] Danna, E., Mandal, S., and A. Singh, "Practical linear 2382 programming algorithm for balancing the max-min fairness 2383 and throughput objectives in traffic engineering", 2384 INFOCOM, 2012 Proceedings IEEE Page(s): 846-854, 2012. 2386 [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. 2387 McManus, "Requirements for Traffic Engineering Over MPLS", 2388 RFC 2702, DOI 10.17487/RFC2702, September 1999, 2389 . 2391 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 2392 Label Switching Architecture", RFC 3031, 2393 DOI 10.17487/RFC3031, January 2001, 2394 . 2396 [RFC3346] Boyle, J., Gill, V., Hannan, A., Cooper, D., Awduche, D., 2397 Christian, B., and W. Lai, "Applicability Statement for 2398 Traffic Engineering with MPLS", RFC 3346, 2399 DOI 10.17487/RFC3346, August 2002, 2400 . 2402 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 2403 (TE) Extensions to OSPF Version 2", RFC 3630, 2404 DOI 10.17487/RFC3630, September 2003, 2405 . 2407 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 2408 Element (PCE)-Based Architecture", RFC 4655, 2409 DOI 10.17487/RFC4655, August 2006, 2410 . 2412 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 2413 Element (PCE) Communication Protocol Generic 2414 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 2415 2006, . 2417 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2418 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2419 DOI 10.17487/RFC5226, May 2008, 2420 . 2422 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 2423 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2424 2008, . 2426 [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash, 2427 "Policy-Enabled Path Computation Framework", RFC 5394, 2428 DOI 10.17487/RFC5394, December 2008, 2429 . 2431 [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. 2432 Hardwick, "Path Computation Element Communication Protocol 2433 (PCEP) Management Information Base (MIB) Module", 2434 RFC 7420, DOI 10.17487/RFC7420, December 2014, 2435 . 2437 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 2438 "Recommendations for Secure Use of Transport Layer 2439 Security (TLS) and Datagram Transport Layer Security 2440 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2441 2015, . 2443 Authors' Addresses 2445 Edward Crabbe 2446 Oracle 2447 1501 4th Ave, suite 1800 2448 Seattle, WA 98101 2449 US 2451 Email: edward.crabbe@oracle.com 2453 Ina Minei 2454 Google, Inc. 2455 1600 Amphitheatre Parkway 2456 Mountain View, CA 94043 2457 US 2459 Email: inaminei@google.com 2460 Jan Medved 2461 Cisco Systems, Inc. 2462 170 West Tasman Dr. 2463 San Jose, CA 95134 2464 US 2466 Email: jmedved@cisco.com 2468 Robert Varga 2469 Pantheon Technologies SRO 2470 Mlynske Nivy 56 2471 Bratislava 821 05 2472 Slovakia 2474 Email: robert.varga@pantheon.tech