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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-03 == Outdated reference: A later version (-14) exists of draft-ietf-pce-pcep-extension-for-pce-controller-02 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-12 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group S. Sivabalan 3 Internet-Draft C. Filsfils 4 Intended status: Standards Track Cisco Systems, Inc. 5 Expires: March 9, 2020 J. Tantsura 6 Apstra, Inc. 7 J. Hardwick 8 Metaswitch Networks 9 S. Previdi 10 C. Li 11 Huawei Technologies 12 September 6, 2019 14 Carrying Binding Label/Segment-ID in PCE-based Networks. 15 draft-ietf-pce-binding-label-sid-00 17 Abstract 19 In order to provide greater scalability, network opacity, and service 20 independence, SR utilizes a Binding Segment Identifier (BSID). It is 21 possible to associate a BSID to RSVP-TE signaled Traffic Engineering 22 Label Switching Path or binding Segment-ID (SID) to Segment Routed 23 (SR) Traffic Engineering path. Such a binding label/SID can be used 24 by an upstream node for steering traffic into the appropriate TE path 25 to enforce SR policies. This document proposes an approach for 26 reporting binding label/SID to Path Computation Element (PCE) for 27 supporting PCE-based Traffic Engineering policies. 29 Requirements Language 31 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 33 "OPTIONAL" in this document are to be interpreted as described in BCP 34 14 [RFC2119] [RFC8174] when, and only when, they appear in all 35 capitals, as shown here. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at https://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on March 9, 2020. 54 Copyright Notice 56 Copyright (c) 2019 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (https://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 73 3. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . 6 74 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 75 5. Binding SID in SR-ERO . . . . . . . . . . . . . . . . . . . . 8 76 6. Binding SID in SRv6-ERO/ . . . . . . . . . . . . . . . . . . 8 77 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 78 7.1. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 9 79 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 80 9. Manageability Considerations . . . . . . . . . . . . . . . . 10 81 9.1. Control of Function and Policy . . . . . . . . . . . . . 10 82 9.2. Information and Data Models . . . . . . . . . . . . . . . 10 83 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 10 84 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 10 85 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 10 86 9.6. Impact On Network Operations . . . . . . . . . . . . . . 10 87 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 88 10.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 11 89 10.1.1. TE-PATH-BINDING TLV . . . . . . . . . . . . . . . . 11 90 10.2. PCEP Error Type and Value . . . . . . . . . . . . . . . 11 91 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 92 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 93 12.1. Normative References . . . . . . . . . . . . . . . . . . 12 94 12.2. Informative References . . . . . . . . . . . . . . . . . 13 95 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 15 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 98 1. Introduction 100 A PCE can compute Traffic Engineering paths (TE paths) through a 101 network that are subject to various constraints. Currently, TE paths 102 are either set up using the RSVP-TE signaling protocol or Segment 103 Routing (SR). We refer to such paths as RSVP-TE paths and SR-TE 104 paths respectively in this document. 106 As per [RFC8402] SR allows a headend node to steer a packet flow 107 along any path. The headend node is said to steer a flow into an 108 Segment Routing Policy (SR Policy). Further, as per 109 [I-D.ietf-spring-segment-routing-policy], an SR Policy is a framework 110 that enables instantiation of an ordered list of segments on a node 111 for implementing a source routing policy with a specific intent for 112 traffic steering from that node. 114 As described in [RFC8402], Binding Segment Identifier (BSID) is bound 115 to an Segment Routed (SR) Policy, instantiation of which may involve 116 a list of SIDs. Any packets received with an active segment equal to 117 BSID are steered onto the bound SR Policy. A BSID may be either a 118 local (SRLB) or a global (SRGB) SID. As per Section 6.4 of 119 [I-D.ietf-spring-segment-routing-policy] a BSID can also be 120 associated with any type of interfaces or tunnel to enable the use of 121 a non-SR interface or tunnels as segments in a SID-list. 123 [RFC5440] describes the Path Computation Element Protocol (PCEP) for 124 communication between a Path Computation Client (PCC) and a PCE or 125 between a pair of PCEs as per [RFC4655]. [RFC8231] specifies 126 extension to PCEP that allows a PCC to delegate its LSPs to a 127 stateful PCE. A stateful PCE can then update the state of LSPs 128 delegated to it. [RFC8281] specifies a mechanism allowing a PCE to 129 dynamically instantiate an LSP on a PCC by sending the path and 130 characteristics. The PCEP extension to setup and maintain SR-TE 131 paths is specified in [I-D.ietf-pce-segment-routing]. 133 [I-D.ietf-pce-segment-routing] provides a mechanism for a network 134 controller (acting as a PCE) to instantiate candidate paths for an SR 135 Policy onto a head-end node (acting as a PCC) using PCEP. For more 136 information on the SR Policy Architecture, see 137 [I-D.ietf-spring-segment-routing-policy]. 139 Binding label/SID has local significance to the ingress node of the 140 corresponding TE path. When a stateful PCE is deployed for setting 141 up TE paths, it may be desirable to report the binding label or SID 142 to the stateful PCE for the purpose of enforcing end-to-end TE/SR 143 policy. A sample Data Center (DC) use-case is illustrated in the 144 following diagram. In the MPLS DC network, an SR LSP (without 145 traffic engineering) is established using a prefix SID advertised by 146 BGP (see [I-D.ietf-idr-bgp-prefix-sid]). In IP/MPLS WAN, an SR-TE 147 LSP is setup using the PCE. The list of SIDs of the SR-TE LSP is {A, 148 B, C, D}. The gateway node 1 (which is the PCC) allocates a binding 149 SID X and reports it to the PCE. In order for the access node to 150 steer the traffic over the SR-TE LSP, the PCE passes the SID stack 151 {Y, X} where Y is the prefix SID of the gateway node-1 to the access 152 node. In the absence of the binding SID X, the PCE should pass the 153 SID stack {Y, A, B, C, D} to the access node. This example also 154 illustrates the additional benefit of using the binding SID to reduce 155 the number of SIDs imposed on the access nodes with a limited 156 forwarding capacity. 158 SID stack 159 {Y, X} +-----+ 160 _ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE | 161 | +-----+ 162 | ^ 163 | | Binding 164 | .-----. | SID (X) .-----. 165 | ( ) | ( ) 166 V .--( )--. | .--( )--. 167 +------+ ( ) +-------+ ( ) +-------+ 168 |Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway| 169 | Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 | 170 +------+ ( SR path ) +-------+ ( SR-TE path ) +-------+ 171 '--( )--' Prefix '--( )--' 172 ( ) SID of ( ) 173 '-----' Node-1 '-----' 174 is Y SIDs for SR-TE LSP: 175 {A, B, C, D} 177 Figure 1: A sample Use-case of Binding SID 179 A PCC could report the binding label/SID allocated by it to the 180 stateful PCE via Path Computation State Report (PCRpt) message. It 181 is also possible for a stateful PCE to request a PCC to allocate a 182 specific binding label/SID by sending an Path Computation Update 183 Request (PCUpd) message. If the PCC can successfully allocate the 184 specified binding value, it reports the binding value to the PCE. 185 Otherwise, the PCC sends an error message to the PCE indicating the 186 cause of the failure. A local policy or configuration at the PCC 187 SHOULD dictate if the binding label/SID needs to be assigned. 189 In this document, we introduce a new OPTIONAL TLV that a PCC can use 190 in order to report the binding label/SID associated with a TE LSP, or 191 a PCE to request a PCC to allocate a specific binding label/SID 192 value. This TLV is intended for TE LSPs established using RSVP-TE, 193 SR, or any other future method. Also, in the case of SR-TE LSPs, the 194 TLV can carry a binding MPLS label (for SR-TE path with MPLS data- 195 plane) or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with 196 IPv6 data-plane). Binding value means either MPLS label or SID 197 throughout this document. 199 Additionally, to support the PCE based central controller [RFC8283] 200 operation where the PCE would take responsibility for managing some 201 part of the MPLS label space for each of the routers that it 202 controls, the PCE could directly make the binding label/SID 203 allocation and inform the PCC. See 204 [I-D.ietf-pce-pcep-extension-for-pce-controller] for details. 206 2. Terminology 208 The following terminologies are used in this document: 210 BSID: Binding Segment Identifier. 212 LER: Label Edge Router. 214 LSP: Label Switched Path. 216 LSR: Label Switching Router. 218 PCC: Path Computation Client. 220 PCE: Path Computation Element 222 PCEP: Path Computation Element Protocol. 224 RSVP-TE: Resource ReserVation Protocol-Traffic Engineering. 226 SID: Segment Identifier. 228 SR: Segment Routing. 230 SRGB: Segment Routing Global Block. 232 SRLB: Segment Routing Local Block. 234 TLV: Type, Length, and Value. 236 3. Path Binding TLV 238 The new optional TLV is called "TE-PATH-BINDING TLV" whose format is 239 shown in the diagram below is defined to carry binding label or SID 240 for a TE path. This TLV is associated with the LSP object specified 241 in ([RFC8231]). The type of this TLV is to be allocated by IANA. 243 0 1 2 3 244 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 1 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 | Type | Length | 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | BT | Reserved | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 ~ Binding Value (variable length) ~ 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 Figure 2: TE-PATH-BINDING TLV 255 TE-PATH-BINDING TLV is a generic TLV such that it is able to carry 256 MPLS label binding as well as SRV6 Binding SID. It is formatted 257 according to the rules specified in [RFC5440]. 259 Binding Type (BT): A one byte field identifies the type of binding 260 included in the TLV. This document specifies the following BT 261 values: 263 o BT = 0: The binding value is an MPLS label carried in the format 264 specified in [RFC5462] where only the label value is valid, and 265 other fields (TC, S, and TTL) fields MUST be considered invalid. 266 The Length MUST be set to 6. 268 o BT = 1: Similar to the case where BT is 0 except that all the 269 fields on the MPLS label entry are set on transmission. However, 270 the receiver MAY choose to override TC, S, and TTL values 271 according its local policy. 273 o BT = 2: The binding value is a SRv6 SID with a format of an 16 274 byte IPv6 address, representing the binding SID for SRv6. 276 Reserved: MUST be set to 0 while sending and ignored on receipt. 278 Binding Value: A variable length field, padded with trailing zeros to 279 a 4-byte boundary. For the BT as 0, the 20 bits represents the MPLS 280 label. For the BT as 1, the 32-bits represents the label stack entry 281 as per [RFC5462]. For the BT as 2, the 128-bits represent the SRv6 282 SID. 284 4. Operation 286 The binding value is allocated by the PCC and reported to a PCE via 287 PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV, 288 it MUST ignore the TLV in accordance with ([RFC5440]). If a PCE 289 recognizes the TLV but does not support the TLV, it MUST send PCErr 290 with Error-Type = 2 (Capability not supported). 292 If a TE-PATH-BINDING TLV is absent in PCRpt message, PCE MUST assume 293 that the corresponding LSP does not have any binding. If there are 294 more than one TE-PATH-BINDING TLVs, only the first TLV MUST be 295 processed and the rest MUST be silently ignored. If a PCE recognizes 296 an invalid binding value (e.g., label value from the reserved label 297 space when MPLS label binding is used), it MUST send the PCErr 298 message with Error-Type = 10 ("Reception of an invalid object") and 299 Error Value = TBD ("Bad label value") as specified in 300 [I-D.ietf-pce-segment-routing]. 302 If a PCE requires a PCC to allocate a specific binding value, it may 303 do so by sending a PCUpd or PCInitiate message containing a TE-PATH- 304 BINDING TLV. If the value can be successfully allocated, the PCC 305 reports the binding value to the PCE. If the PCC considers the 306 binding value specified by the PCE invalid, it MUST send a PCErr 307 message with Error-Type = TBD ("Binding label/SID failure") and Error 308 Value = TBD ("Invalid SID"). If the binding value is valid, but the 309 PCC is unable to allocate the binding value, it MUST send a PCErr 310 message with Error-Type = TBD ("Binding label/SID failure") and Error 311 Value = TBD ("Unable to allocate the specified label/SID"). 313 If a PCC receives TE-PATH-BINDING TLV in any message other than PCUpd 314 or PCInitiate, it MUST close the corresponding PCEP session with the 315 reason "Reception of a malformed PCEP message" (according to 316 [RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in 317 any message other than a PCRpt or if the TE-PATH-BINDING TLV is 318 associated with any object other than LSP object, the PCE MUST close 319 the corresponding PCEP session with the reason "Reception of a 320 malformed PCEP message" (according to [RFC5440]). 322 If a PCC wishes to withdraw or modify a previously reported binding 323 value, it MUST send a PCRpt message without any TE-PATH-BINDING TLV 324 or with the TE-PATH-BINDING TLV containing the new binding value 325 respectively. 327 If a PCE wishes to modify a previously requested binding value, it 328 MUST send a PCUpd message with TE-PATH-BINDING TLV containing the new 329 binding value. Absence of TE-PATH-BINDING TLV in PCUpd message means 330 that the PCE does not specify a binding value in which case the 331 binding value allocation is governed by the PCC's local policy. 333 If a PCC receives a valid binding value from a PCE which is different 334 than the current binding value, it MUST try to allocate the new 335 value. If the new binding value is successfully allocated, the PCC 336 MUST report the new value to the PCE. Otherwise, it MUST send a 337 PCErr message with Error-Type = TBD ("Binding label/SID failure") and 338 Error Value = TBD ("Unable to allocate the specified label/SID"). 340 In some cases, a stateful PCE can request the PCC to allocate a 341 binding value. It may do so by sending a PCUpd message containing an 342 empty TE-PATH-BINDING TLV, i.e., no binding value is specified 343 (making the length field of the TLV as 2). A PCE can also make the 344 request PCC to allocate a binding at the time of initiation by 345 sending a PCInitiate message with an empty TE-PATH-BINDING TLV. 347 5. Binding SID in SR-ERO 349 In PCEP messages, LSP route information is carried in the Explicit 350 Route Object (ERO), which consists of a sequence of subobjects. 351 [I-D.ietf-pce-segment-routing] defines a new ERO subobject "SR-ERO 352 subobject" capable of carrying a SID as well as the identity of the 353 node/adjacency (NAI) represented by the SID. The NAI Type (NT) field 354 indicates the type and format of the NAI contained in the SR-ERO. In 355 case of binding SID, the NAI MUST NOT be included and NT MUST be set 356 to zero. So as per Section 5.2.1 of [I-D.ietf-pce-segment-routing], 357 for NT=0, the F bit MUST be 1, the S bit needs to be zero and the 358 Length MUST be 8. Further the M bit MUST be set. If these 359 conditions are not met, the entire ERO MUST be considered invalid and 360 a PCErr message is sent with Error-Type = 10 ("Reception of an 361 invalid object") and Error-Value = 11 ("Malformed object"). 363 6. Binding SID in SRv6-ERO/ 365 [I-D.ietf-pce-segment-routing] defines a new ERO subobject "SRv6-ERO 366 subobject" for SRv6 SID. The NAI MUST NOT be included and NT MUST be 367 set to zero. So as per Section 5.2.1 of 368 [I-D.ietf-pce-segment-routing], for NT=0, the F bit MUST be 1, the S 369 bit needs to be zero and the Length MUST be 24. If these conditions 370 are not met, the entire ERO is considered invalid and a PCErr message 371 is sent with Error-Type = 10 ("Reception of an invalid object") and 372 Error-Value = 11 ("Malformed object") (as per 373 [I-D.ietf-pce-segment-routing]). 375 7. Implementation Status 377 [Note to the RFC Editor - remove this section before publication, as 378 well as remove the reference to RFC 7942.] 379 This section records the status of known implementations of the 380 protocol defined by this specification at the time of posting of this 381 Internet-Draft, and is based on a proposal described in [RFC7942]. 382 The description of implementations in this section is intended to 383 assist the IETF in its decision processes in progressing drafts to 384 RFCs. Please note that the listing of any individual implementation 385 here does not imply endorsement by the IETF. Furthermore, no effort 386 has been spent to verify the information presented here that was 387 supplied by IETF contributors. This is not intended as, and must not 388 be construed to be, a catalog of available implementations or their 389 features. Readers are advised to note that other implementations may 390 exist. 392 According to [RFC7942], "this will allow reviewers and working groups 393 to assign due consideration to documents that have the benefit of 394 running code, which may serve as evidence of valuable experimentation 395 and feedback that have made the implemented protocols more mature. 396 It is up to the individual working groups to use this information as 397 they see fit". 399 7.1. Huawei 401 o Organization: Huawei 403 o Implementation: Huawei's Router and Controller 405 o Description: An experimental code-point is used and plan to 406 request early code-point allocation from IANA after WG adoption. 408 o Maturity Level: Production 410 o Coverage: Full 412 o Contact: mahendrasingh@huawei.com 414 8. Security Considerations 416 The security considerations described in [RFC5440], [RFC8231], 417 [RFC8281] and [I-D.ietf-pce-segment-routing] are applicable to this 418 specification. No additional security measure is required. 420 As described [I-D.ietf-pce-segment-routing], SR allows a network 421 controller to instantiate and control paths in the network. A rouge 422 PCE can manipulate binding SID allocations to move traffic around for 423 some other LSPs that uses BSID in its SR-ERO. 425 Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions 426 only be activated on authenticated and encrypted sessions across PCEs 427 and PCCs belonging to the same administrative authority, using 428 Transport Layer Security (TLS) [RFC8253], as per the recommendations 429 and best current practices in [RFC7525] (unless explicitly set aside 430 in [RFC8253]). 432 9. Manageability Considerations 434 All manageability requirements and considerations listed in 435 [RFC5440], [RFC8231], and [I-D.ietf-pce-segment-routing] apply to 436 PCEP protocol extensions defined in this document. In addition, 437 requirements and considerations listed in this section apply. 439 9.1. Control of Function and Policy 441 A PCC implementation SHOULD allow the operator to configure the 442 policy based on which PCC needs to allocates the binding label/SID. 444 9.2. Information and Data Models 446 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 447 include policy configuration for binding label/SID allocation. 449 9.3. Liveness Detection and Monitoring 451 Mechanisms defined in this document do not imply any new liveness 452 detection and monitoring requirements in addition to those already 453 listed in [RFC5440]. 455 9.4. Verify Correct Operations 457 Mechanisms defined in this document do not imply any new operation 458 verification requirements in addition to those already listed in 459 [RFC5440], [RFC8231], and [I-D.ietf-pce-segment-routing]. 461 9.5. Requirements On Other Protocols 463 Mechanisms defined in this document do not imply any new requirements 464 on other protocols. 466 9.6. Impact On Network Operations 468 Mechanisms defined in [RFC5440], [RFC8231], and 469 [I-D.ietf-pce-segment-routing] also apply to PCEP extensions defined 470 in this document. Further, the mechanism described in this document 471 can help the operator to request control of the LSPs at a particular 472 PCE. 474 10. IANA Considerations 476 10.1. PCEP TLV Type Indicators 478 This document defines a new PCEP TLV; IANA is requested to make the 479 following allocations from the "PCEP TLV Type Indicators" sub- 480 registry of the PCEP Numbers registry, as follows: 482 Value Name Reference 484 TBD TE-PATH-BINDING This document 486 10.1.1. TE-PATH-BINDING TLV 488 IANA is requested to create a sub-registry to manage the value of the 489 Binding Type field in the TE-PATH-BINDING TLV. 491 Value Description Reference 493 0 MPLS Label This document 494 1 MPLS Label Stack This document 495 Entry 496 2 SRv6 SID This document 498 10.2. PCEP Error Type and Value 500 This document defines a new Error-type and Error-Values for the PCErr 501 message. IANA is requested to allocate new error-type and error- 502 values within the "PCEP-ERROR Object Error Types and Values" 503 subregistry of the PCEP Numbers registry, as follows: 505 Error-Type Meaning 506 ---------- ------- 507 TBD Binding label/SID failure: 509 Error-value = TBD: Invalid SID 510 Error-value = TBD: Unable to allocate 511 the specified 512 label/SID 514 11. Acknowledgements 516 We like to thank Milos Fabian for his valuable comments. 518 12. References 520 12.1. Normative References 522 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 523 Requirement Levels", BCP 14, RFC 2119, 524 DOI 10.17487/RFC2119, March 1997, 525 . 527 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 528 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 529 DOI 10.17487/RFC5440, March 2009, 530 . 532 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 533 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 534 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 535 2009, . 537 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 538 "Recommendations for Secure Use of Transport Layer 539 Security (TLS) and Datagram Transport Layer Security 540 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 541 2015, . 543 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 544 Code: The Implementation Status Section", BCP 205, 545 RFC 7942, DOI 10.17487/RFC7942, July 2016, 546 . 548 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 549 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 550 May 2017, . 552 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 553 Computation Element Communication Protocol (PCEP) 554 Extensions for Stateful PCE", RFC 8231, 555 DOI 10.17487/RFC8231, September 2017, 556 . 558 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 559 "PCEPS: Usage of TLS to Provide a Secure Transport for the 560 Path Computation Element Communication Protocol (PCEP)", 561 RFC 8253, DOI 10.17487/RFC8253, October 2017, 562 . 564 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 565 Computation Element Communication Protocol (PCEP) 566 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 567 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 568 . 570 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 571 Decraene, B., Litkowski, S., and R. Shakir, "Segment 572 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 573 July 2018, . 575 [I-D.ietf-pce-segment-routing] 576 Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 577 and J. Hardwick, "PCEP Extensions for Segment Routing", 578 draft-ietf-pce-segment-routing-16 (work in progress), 579 March 2019. 581 12.2. Informative References 583 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 584 Element (PCE)-Based Architecture", RFC 4655, 585 DOI 10.17487/RFC4655, August 2006, 586 . 588 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 589 Architecture for Use of PCE and the PCE Communication 590 Protocol (PCEP) in a Network with Central Control", 591 RFC 8283, DOI 10.17487/RFC8283, December 2017, 592 . 594 [I-D.ietf-spring-segment-routing-policy] 595 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 596 bogdanov@google.com, b., and P. Mattes, "Segment Routing 597 Policy Architecture", draft-ietf-spring-segment-routing- 598 policy-03 (work in progress), May 2019. 600 [I-D.ietf-idr-bgp-prefix-sid] 601 Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A., 602 and H. Gredler, "Segment Routing Prefix SID extensions for 603 BGP", draft-ietf-idr-bgp-prefix-sid-27 (work in progress), 604 June 2018. 606 [I-D.ietf-pce-pcep-extension-for-pce-controller] 607 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 608 and Protocol Extensions for Using PCE as a Central 609 Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 610 extension-for-pce-controller-02 (work in progress), July 611 2019. 613 [I-D.ietf-pce-pcep-yang] 614 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 615 YANG Data Model for Path Computation Element 616 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 617 yang-12 (work in progress), July 2019. 619 Appendix A. Contributor Addresses 621 Dhruv Dhody 622 Huawei Technologies 623 Divyashree Techno Park, Whitefield 624 Bangalore, Karnataka 560066 625 India 627 EMail: dhruv.ietf@gmail.com 629 Mahendra Singh Negi 631 EMail: mahend.ietf@gmail.com 633 Authors' Addresses 635 Siva Sivabalan 636 Cisco Systems, Inc. 637 2000 Innovation Drive 638 Kanata, Ontario K2K 3E8 639 Canada 641 EMail: msiva@cisco.com 643 Clarence Filsfils 644 Cisco Systems, Inc. 645 Pegasus Parc 646 De kleetlaan 6a, DIEGEM BRABANT 1831 647 BELGIUM 649 EMail: cfilsfil@cisco.com 651 Jeff Tantsura 652 Apstra, Inc. 654 EMail: jefftant.ietf@gmail.com 656 Jonathan Hardwick 657 Metaswitch Networks 658 100 Church Street 659 Enfield, Middlesex 660 UK 662 EMail: Jonathan.Hardwick@metaswitch.com 663 Stefano Previdi 664 Huawei Technologies 666 EMail: stefano@previdi.net 668 Cheng Li 669 Huawei Technologies 670 Huawei Campus, No. 156 Beiqing Rd. 671 Beijing 100095 672 China 674 EMail: chengli13@huawei.com