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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-07 == Outdated reference: draft-ietf-pce-pcep-extension-for-pce-controller has been published as RFC 9050 == Outdated reference: A later version (-18) exists of draft-ietf-pce-pcep-yang-13 Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group C. Filsfils 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track S. Sivabalan 5 Expires: December 24, 2020 Ciena Corporation 6 J. Tantsura 7 Apstra, Inc. 8 J. Hardwick 9 Metaswitch Networks 10 S. Previdi 11 C. Li 12 Huawei Technologies 13 June 22, 2020 15 Carrying Binding Label/Segment-ID in PCE-based Networks. 16 draft-ietf-pce-binding-label-sid-03 18 Abstract 20 In order to provide greater scalability, network opacity, and service 21 independence, Segment Routing (SR) utilizes a Binding Segment 22 Identifier (BSID). It is possible to associate a BSID to RSVP-TE 23 signaled Traffic Engineering Label Switching Path or binding Segment- 24 ID (SID) to SR Traffic Engineering path. Such a binding label/SID 25 can be used by an upstream node for steering traffic into the 26 appropriate TE path to enforce SR policies. This document proposes 27 an approach for reporting binding label/SID to Path Computation 28 Element (PCE) for supporting PCE-based Traffic Engineering policies. 30 Requirements Language 32 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 33 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 34 "OPTIONAL" in this document are to be interpreted as described in BCP 35 14 [RFC2119] [RFC8174] when, and only when, they appear in all 36 capitals, as shown here. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at https://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on December 24, 2020. 55 Copyright Notice 57 Copyright (c) 2020 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (https://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 73 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 74 3. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . 6 75 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 76 5. Binding SID in SR-ERO . . . . . . . . . . . . . . . . . . . . 8 77 6. Binding SID in SRv6-ERO . . . . . . . . . . . . . . . . . . . 8 78 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 79 7.1. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 9 80 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 81 9. Manageability Considerations . . . . . . . . . . . . . . . . 10 82 9.1. Control of Function and Policy . . . . . . . . . . . . . 10 83 9.2. Information and Data Models . . . . . . . . . . . . . . . 10 84 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 10 85 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 10 86 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 10 87 9.6. Impact On Network Operations . . . . . . . . . . . . . . 11 88 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 89 10.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 11 90 10.1.1. TE-PATH-BINDING TLV . . . . . . . . . . . . . . . . 11 91 10.2. PCEP Error Type and Value . . . . . . . . . . . . . . . 11 92 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 93 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 94 12.1. Normative References . . . . . . . . . . . . . . . . . . 12 95 12.2. Informative References . . . . . . . . . . . . . . . . . 13 97 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 15 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 100 1. Introduction 102 A PCE can compute Traffic Engineering paths (TE paths) through a 103 network that are subject to various constraints. Currently, TE paths 104 are either set up using the RSVP-TE signaling protocol or Segment 105 Routing (SR). We refer to such paths as RSVP-TE paths and SR-TE 106 paths respectively in this document. 108 As per [RFC8402] SR allows a headend node to steer a packet flow 109 along any path. The headend node is said to steer a flow into an 110 Segment Routing Policy (SR Policy). Further, as per 111 [I-D.ietf-spring-segment-routing-policy], an SR Policy is a framework 112 that enables instantiation of an ordered list of segments on a node 113 for implementing a source routing policy with a specific intent for 114 traffic steering from that node. 116 As described in [RFC8402], Binding Segment Identifier (BSID) is bound 117 to an Segment Routed (SR) Policy, instantiation of which may involve 118 a list of SIDs. Any packets received with an active segment equal to 119 BSID are steered onto the bound SR Policy. A BSID may be either a 120 local (SR Local Block (SRLB)) or a global (SR Global Block (SRGB)) 121 SID. As per Section 6.4 of [I-D.ietf-spring-segment-routing-policy] 122 a BSID can also be associated with any type of interfaces or tunnel 123 to enable the use of a non-SR interface or tunnels as segments in a 124 SID-list. 126 [RFC5440] describes the Path Computation Element Protocol (PCEP) for 127 communication between a Path Computation Client (PCC) and a PCE or 128 between a pair of PCEs as per [RFC4655]. [RFC8231] specifies 129 extension to PCEP that allows a PCC to delegate its LSPs to a 130 stateful PCE. A stateful PCE can then update the state of LSPs 131 delegated to it. [RFC8281] specifies a mechanism allowing a PCE to 132 dynamically instantiate an LSP on a PCC by sending the path and 133 characteristics. The PCEP extension to setup and maintain SR-TE 134 paths is specified in [RFC8664]. 136 [RFC8664] provides a mechanism for a network controller (acting as a 137 PCE) to instantiate candidate paths for an SR Policy onto a head-end 138 node (acting as a PCC) using PCEP. For more information on the SR 139 Policy Architecture, see [I-D.ietf-spring-segment-routing-policy]. 141 Binding label/SID has local significance to the ingress node of the 142 corresponding TE path. When a stateful PCE is deployed for setting 143 up TE paths, it may be desirable to report the binding label or SID 144 to the stateful PCE for the purpose of enforcing end-to-end TE/SR 145 policy. A sample Data Center (DC) use-case is illustrated in the 146 following diagram. In the MPLS DC network, an SR LSP (without 147 traffic engineering) is established using a prefix SID advertised by 148 BGP (see [RFC8669]). In IP/MPLS WAN, an SR-TE LSP is setup using the 149 PCE. The list of SIDs of the SR-TE LSP is {A, B, C, D}. The gateway 150 node 1 (which is the PCC) allocates a binding SID X and reports it to 151 the PCE. In order for the access node to steer the traffic over the 152 SR-TE LSP, the PCE passes the SID stack {Y, X} where Y is the prefix 153 SID of the gateway node-1 to the access node. In the absence of the 154 binding SID X, the PCE should pass the SID stack {Y, A, B, C, D} to 155 the access node. This example also illustrates the additional 156 benefit of using the binding SID to reduce the number of SIDs imposed 157 on the access nodes with a limited forwarding capacity. 159 SID stack 160 {Y, X} +-----+ 161 _ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE | 162 | +-----+ 163 | ^ 164 | | Binding 165 | .-----. | SID (X) .-----. 166 | ( ) | ( ) 167 V .--( )--. | .--( )--. 168 +------+ ( ) +-------+ ( ) +-------+ 169 |Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway| 170 | Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 | 171 +------+ ( SR path ) +-------+ ( SR-TE path ) +-------+ 172 '--( )--' Prefix '--( )--' 173 ( ) SID of ( ) 174 '-----' Node-1 '-----' 175 is Y SIDs for SR-TE LSP: 176 {A, B, C, D} 178 Figure 1: A sample Use-case of Binding SID 180 A PCC could report the binding label/SID allocated by it to the 181 stateful PCE via Path Computation State Report (PCRpt) message. It 182 is also possible for a stateful PCE to request a PCC to allocate a 183 specific binding label/SID by sending an Path Computation Update 184 Request (PCUpd) message. If the PCC can successfully allocate the 185 specified binding value, it reports the binding value to the PCE. 186 Otherwise, the PCC sends an error message to the PCE indicating the 187 cause of the failure. A local policy or configuration at the PCC 188 SHOULD dictate if the binding label/SID needs to be assigned. 190 In this document, we introduce a new OPTIONAL TLV that a PCC can use 191 in order to report the binding label/SID associated with a TE LSP, or 192 a PCE to request a PCC to allocate a specific binding label/SID 193 value. This TLV is intended for TE LSPs established using RSVP-TE, 194 SR, or any other future method. Also, in the case of SR-TE LSPs, the 195 TLV can carry a binding MPLS label (for SR-TE path with MPLS data- 196 plane) or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with 197 IPv6 data-plane). Binding value means either MPLS label or SID 198 throughout this document. 200 Additionally, to support the PCE based central controller [RFC8283] 201 operation where the PCE would take responsibility for managing some 202 part of the MPLS label space for each of the routers that it 203 controls, the PCE could directly make the binding label/SID 204 allocation and inform the PCC. See 205 [I-D.ietf-pce-pcep-extension-for-pce-controller] for details. 207 2. Terminology 209 The following terminologies are used in this document: 211 BSID: Binding Segment Identifier. 213 LER: Label Edge Router. 215 LSP: Label Switched Path. 217 LSR: Label Switching Router. 219 PCC: Path Computation Client. 221 PCE: Path Computation Element 223 PCEP: Path Computation Element Protocol. 225 RSVP-TE: Resource ReserVation Protocol-Traffic Engineering. 227 SID: Segment Identifier. 229 SR: Segment Routing. 231 SRGB: Segment Routing Global Block. 233 SRLB: Segment Routing Local Block. 235 TLV: Type, Length, and Value. 237 3. Path Binding TLV 239 The new optional TLV is called "TE-PATH-BINDING TLV" (whose format is 240 shown in the figure below) is defined to carry binding label or SID 241 for a TE path. This TLV is associated with the LSP object specified 242 in ([RFC8231]). The type of this TLV is to be allocated by IANA. 244 0 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | Type | Length | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | BT | Reserved | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 ~ Binding Value (variable length) ~ 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 Figure 2: TE-PATH-BINDING TLV 256 TE-PATH-BINDING TLV is a generic TLV such that it is able to carry 257 MPLS label binding as well as SRv6 Binding SID. It is formatted 258 according to the rules specified in [RFC5440]. 260 Binding Type (BT): A one byte field identifies the type of binding 261 included in the TLV. This document specifies the following BT 262 values: 264 o BT = 0: The binding value is an MPLS label carried in the format 265 specified in [RFC5462] where only the label value is valid, and 266 other fields fields MUST be considered invalid. The Length MUST 267 be set to 7. 269 o BT = 1: Similar to the case where BT is 0 except that all the 270 fields on the MPLS label entry are set on transmission. However, 271 the receiver MAY choose to override TC, S, and TTL values 272 according its local policy. The Length MUST be set to 8. 274 o BT = 2: The binding value is a SRv6 SID with a format of an 16 275 byte IPv6 address, representing the binding SID for SRv6. The 276 Length MUST be set to 20. 278 Reserved: MUST be set to 0 while sending and ignored on receipt. 280 Binding Value: A variable length field, padded with trailing zeros to 281 a 4-byte boundary. For the BT as 0, the 20 bits represents the MPLS 282 label. For the BT as 1, the 32-bits represents the label stack entry 283 as per [RFC5462]. For the BT as 2, the 128-bits represent the SRv6 284 SID. 286 4. Operation 288 The binding value is allocated by the PCC and reported to a PCE via 289 PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV, 290 it would ignore the TLV in accordance with ([RFC5440]). If a PCE 291 recognizes the TLV but does not support the TLV, it MUST send PCErr 292 with Error-Type = 2 (Capability not supported). 294 If a TE-PATH-BINDING TLV is absent in PCRpt message, PCE MUST assume 295 that the corresponding LSP does not have any binding. If there are 296 more than one TE-PATH-BINDING TLVs, only the first TLV MUST be 297 processed and the rest MUST be silently ignored. If a PCE recognizes 298 an invalid binding value (e.g., label value from the reserved label 299 space when MPLS label binding is used), it MUST send the PCErr 300 message with Error-Type = 10 ("Reception of an invalid object") and 301 Error Value = 2 ("Bad label value") as specified in [RFC8664]. 303 If a PCE requires a PCC to allocate a specific binding value, it may 304 do so by sending a PCUpd or PCInitiate message containing a TE-PATH- 305 BINDING TLV. If the value can be successfully allocated, the PCC 306 reports the binding value to the PCE. If the PCC considers the 307 binding value specified by the PCE invalid, it MUST send a PCErr 308 message with Error-Type = TBD2 ("Binding label/SID failure") and 309 Error Value = TBD3 ("Invalid SID"). If the binding value is valid, 310 but the PCC is unable to allocate the binding value, it MUST send a 311 PCErr message with Error-Type = TBD2 ("Binding label/SID failure") 312 and Error Value = TBD4 ("Unable to allocate the specified label/ 313 SID"). 315 If a PCC receives TE-PATH-BINDING TLV in any message other than PCUpd 316 or PCInitiate, it MUST close the corresponding PCEP session with the 317 reason "Reception of a malformed PCEP message" (according to 318 [RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in 319 any message other than a PCRpt or if the TE-PATH-BINDING TLV is 320 associated with any object other than LSP object, the PCE MUST close 321 the corresponding PCEP session with the reason "Reception of a 322 malformed PCEP message" (according to [RFC5440]). 324 If a PCC wishes to withdraw or modify a previously reported binding 325 value, it MUST send a PCRpt message without any TE-PATH-BINDING TLV 326 or with the TE-PATH-BINDING TLV containing the new binding value 327 respectively. 329 If a PCE wishes to modify a previously requested binding value, it 330 MUST send a PCUpd message with TE-PATH-BINDING TLV containing the new 331 binding value. Absence of TE-PATH-BINDING TLV in PCUpd message means 332 that the PCE does not specify a binding value in which case the 333 binding value allocation is governed by the PCC's local policy. 335 If a PCC receives a valid binding value from a PCE which is different 336 than the current binding value, it MUST try to allocate the new 337 value. If the new binding value is successfully allocated, the PCC 338 MUST report the new value to the PCE. Otherwise, it MUST send a 339 PCErr message with Error-Type = TBD2 ("Binding label/SID failure") 340 and Error Value = TBD4 ("Unable to allocate the specified label/ 341 SID"). 343 In some cases, a stateful PCE can request the PCC to allocate a 344 binding value. It may do so by sending a PCUpd message containing an 345 empty TE-PATH-BINDING TLV, i.e., no binding value is specified 346 (making the length field of the TLV as 4). A PCE can also make the 347 request PCC to allocate a binding at the time of initiation by 348 sending a PCInitiate message with an empty TE-PATH-BINDING TLV. 350 5. Binding SID in SR-ERO 352 In PCEP messages, LSP route information is carried in the Explicit 353 Route Object (ERO), which consists of a sequence of subobjects. 354 [RFC8664] defines a new ERO subobject "SR-ERO subobject" capable of 355 carrying a SID as well as the identity of the node/adjacency (NAI) 356 represented by the SID. The NAI Type (NT) field indicates the type 357 and format of the NAI contained in the SR-ERO. In case of binding 358 SID, the NAI MUST NOT be included and NT MUST be set to zero. So as 359 per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the 360 S bit needs to be zero and the Length is 8. Further the M bit is 361 set. If these conditions are not met, the entire ERO MUST be 362 considered invalid and a PCErr message is sent with Error-Type = 10 363 ("Reception of an invalid object") and Error-Value = 11 ("Malformed 364 object"). 366 6. Binding SID in SRv6-ERO 368 [RFC8664] defines a new ERO subobject "SRv6-ERO subobject" for SRv6 369 SID. The NAI MUST NOT be included and NT MUST be set to zero. So as 370 per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the 371 S bit needs to be zero and the Length is 24. If these conditions are 372 not met, the entire ERO is considered invalid and a PCErr message is 373 sent with Error-Type = 10 ("Reception of an invalid object") and 374 Error-Value = 11 ("Malformed object") (as per [RFC8664]). 376 7. Implementation Status 378 [Note to the RFC Editor - remove this section before publication, as 379 well as remove the reference to RFC 7942.] 381 This section records the status of known implementations of the 382 protocol defined by this specification at the time of posting of this 383 Internet-Draft, and is based on a proposal described in [RFC7942]. 384 The description of implementations in this section is intended to 385 assist the IETF in its decision processes in progressing drafts to 386 RFCs. Please note that the listing of any individual implementation 387 here does not imply endorsement by the IETF. Furthermore, no effort 388 has been spent to verify the information presented here that was 389 supplied by IETF contributors. This is not intended as, and must not 390 be construed to be, a catalog of available implementations or their 391 features. Readers are advised to note that other implementations may 392 exist. 394 According to [RFC7942], "this will allow reviewers and working groups 395 to assign due consideration to documents that have the benefit of 396 running code, which may serve as evidence of valuable experimentation 397 and feedback that have made the implemented protocols more mature. 398 It is up to the individual working groups to use this information as 399 they see fit". 401 7.1. Huawei 403 o Organization: Huawei 405 o Implementation: Huawei's Router and Controller 407 o Description: An experimental code-point is used and plan to 408 request early code-point allocation from IANA after WG adoption. 410 o Maturity Level: Production 412 o Coverage: Full 414 o Contact: chengli13@huawei.com 416 8. Security Considerations 418 The security considerations described in [RFC5440], [RFC8231], 419 [RFC8281] and [RFC8664] are applicable to this specification. No 420 additional security measure is required. 422 As described [RFC8664], SR allows a network controller to instantiate 423 and control paths in the network. A rouge PCE can manipulate binding 424 SID allocations to move traffic around for some other LSPs that uses 425 BSID in its SR-ERO. 427 Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions 428 only be activated on authenticated and encrypted sessions across PCEs 429 and PCCs belonging to the same administrative authority, using 430 Transport Layer Security (TLS) [RFC8253], as per the recommendations 431 and best current practices in BCP195 [RFC7525] (unless explicitly set 432 aside in [RFC8253]). 434 9. Manageability Considerations 436 All manageability requirements and considerations listed in 437 [RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions 438 defined in this document. In addition, requirements and 439 considerations listed in this section apply. 441 9.1. Control of Function and Policy 443 A PCC implementation SHOULD allow the operator to configure the 444 policy based on which PCC needs to allocates the binding label/SID. 446 9.2. Information and Data Models 448 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 449 include policy configuration for binding label/SID allocation. 451 9.3. Liveness Detection and Monitoring 453 Mechanisms defined in this document do not imply any new liveness 454 detection and monitoring requirements in addition to those already 455 listed in [RFC5440]. 457 9.4. Verify Correct Operations 459 Mechanisms defined in this document do not imply any new operation 460 verification requirements in addition to those already listed in 461 [RFC5440], [RFC8231], and [RFC8664]. 463 9.5. Requirements On Other Protocols 465 Mechanisms defined in this document do not imply any new requirements 466 on other protocols. 468 9.6. Impact On Network Operations 470 Mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply 471 to PCEP extensions defined in this document. Further, the mechanism 472 described in this document can help the operator to request control 473 of the LSPs at a particular PCE. 475 10. IANA Considerations 477 10.1. PCEP TLV Type Indicators 479 This document defines a new PCEP TLV; IANA is requested to make the 480 following allocations from the "PCEP TLV Type Indicators" sub- 481 registry of the PCEP Numbers registry, as follows: 483 Value Name Reference 485 TBD1 TE-PATH-BINDING This document 487 10.1.1. TE-PATH-BINDING TLV 489 IANA is requested to create a sub-registry to manage the value of the 490 Binding Type field in the TE-PATH-BINDING TLV. 492 Value Description Reference 494 0 MPLS Label This document 495 1 MPLS Label Stack This document 496 Entry 497 2 SRv6 SID This document 499 10.2. PCEP Error Type and Value 501 This document defines a new Error-type and Error-Values for the PCErr 502 message. IANA is requested to allocate new error-type and error- 503 values within the "PCEP-ERROR Object Error Types and Values" 504 subregistry of the PCEP Numbers registry, as follows: 506 Error-Type Meaning 507 ---------- ------- 508 TBD2 Binding label/SID failure: 510 Error-value = TBD3: Invalid SID 511 Error-value = TBD4: Unable to allocate 512 the specified 513 label/SID 515 11. Acknowledgements 517 We like to thank Milos Fabian and Mrinmoy Das for thier valuable 518 comments. 520 12. References 522 12.1. Normative References 524 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 525 Requirement Levels", BCP 14, RFC 2119, 526 DOI 10.17487/RFC2119, March 1997, 527 . 529 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 530 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 531 DOI 10.17487/RFC5440, March 2009, 532 . 534 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 535 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 536 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 537 2009, . 539 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 540 "Recommendations for Secure Use of Transport Layer 541 Security (TLS) and Datagram Transport Layer Security 542 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 543 2015, . 545 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 546 Code: The Implementation Status Section", BCP 205, 547 RFC 7942, DOI 10.17487/RFC7942, July 2016, 548 . 550 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 551 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 552 May 2017, . 554 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 555 Computation Element Communication Protocol (PCEP) 556 Extensions for Stateful PCE", RFC 8231, 557 DOI 10.17487/RFC8231, September 2017, 558 . 560 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 561 "PCEPS: Usage of TLS to Provide a Secure Transport for the 562 Path Computation Element Communication Protocol (PCEP)", 563 RFC 8253, DOI 10.17487/RFC8253, October 2017, 564 . 566 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 567 Computation Element Communication Protocol (PCEP) 568 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 569 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 570 . 572 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 573 Decraene, B., Litkowski, S., and R. Shakir, "Segment 574 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 575 July 2018, . 577 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 578 and J. Hardwick, "Path Computation Element Communication 579 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 580 DOI 10.17487/RFC8664, December 2019, 581 . 583 12.2. Informative References 585 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 586 Element (PCE)-Based Architecture", RFC 4655, 587 DOI 10.17487/RFC4655, August 2006, 588 . 590 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 591 Architecture for Use of PCE and the PCE Communication 592 Protocol (PCEP) in a Network with Central Control", 593 RFC 8283, DOI 10.17487/RFC8283, December 2017, 594 . 596 [RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, 597 A., and H. Gredler, "Segment Routing Prefix Segment 598 Identifier Extensions for BGP", RFC 8669, 599 DOI 10.17487/RFC8669, December 2019, 600 . 602 [I-D.ietf-spring-segment-routing-policy] 603 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 604 P. Mattes, "Segment Routing Policy Architecture", draft- 605 ietf-spring-segment-routing-policy-07 (work in progress), 606 May 2020. 608 [I-D.ietf-pce-pcep-extension-for-pce-controller] 609 Zhao, Q., Li, Z., Negi, M., Peng, S., and C. Zhou, "PCEP 610 Procedures and Protocol Extensions for Using PCE as a 611 Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 612 extension-for-pce-controller-04 (work in progress), March 613 2020. 615 [I-D.ietf-pce-pcep-yang] 616 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 617 YANG Data Model for Path Computation Element 618 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 619 yang-13 (work in progress), October 2019. 621 Appendix A. Contributor Addresses 623 Dhruv Dhody 624 Huawei Technologies 625 Divyashree Techno Park, Whitefield 626 Bangalore, Karnataka 560066 627 India 629 EMail: dhruv.ietf@gmail.com 631 Mahendra Singh Negi 632 RtBrick India 633 N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3 634 Bangalore, Karnataka 560102 635 India 637 EMail: mahend.ietf@gmail.com 639 Mike Koldychev 640 Cisco Systems, Inc. 641 2000 Innovation Drive 642 Kanata, Ontario K2K 3E8 643 Canada 645 Email: mkoldych@cisco.com 647 Zafar Ali 648 Cisco Systems, Inc. 650 Email: zali@cisco.com 652 Authors' Addresses 654 Clarence Filsfils 655 Cisco Systems, Inc. 656 Pegasus Parc 657 De kleetlaan 6a, DIEGEM BRABANT 1831 658 BELGIUM 660 EMail: cfilsfil@cisco.com 662 Siva Sivabalan 663 Ciena Corporation 665 EMail: msiva282@gmail.com 666 Jeff Tantsura 667 Apstra, Inc. 669 EMail: jefftant.ietf@gmail.com 671 Jonathan Hardwick 672 Metaswitch Networks 673 100 Church Street 674 Enfield, Middlesex 675 UK 677 EMail: Jonathan.Hardwick@metaswitch.com 679 Stefano Previdi 680 Huawei Technologies 682 EMail: stefano@previdi.net 684 Cheng Li 685 Huawei Technologies 686 Huawei Campus, No. 156 Beiqing Rd. 687 Beijing 100095 688 China 690 EMail: chengli13@huawei.com