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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-03 == Outdated reference: A later version (-14) exists of draft-ietf-pce-pcep-extension-for-pce-controller-02 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-13 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--).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: May 6, 2020 J. Tantsura 6 Apstra, Inc. 7 J. Hardwick 8 Metaswitch Networks 9 S. Previdi 10 C. Li 11 Huawei Technologies 12 November 3, 2019 14 Carrying Binding Label/Segment-ID in PCE-based Networks. 15 draft-ietf-pce-binding-label-sid-01 17 Abstract 19 In order to provide greater scalability, network opacity, and service 20 independence, Segment Routing (SR) utilizes a Binding Segment 21 Identifier (BSID). It is possible to associate a BSID to RSVP-TE 22 signaled Traffic Engineering Label Switching Path or binding Segment- 23 ID (SID) to SR Traffic Engineering path. Such a binding label/SID 24 can be used by an upstream node for steering traffic into the 25 appropriate TE path to enforce SR policies. This document proposes 26 an approach for reporting binding label/SID to Path Computation 27 Element (PCE) for 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 May 6, 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 . . . . . . . . . . . . . . . . . . . . 9 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 . . . . . . . . . . . . . . 11 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 . . . . . . . . . . . . . . . . . . . . . . 12 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 (SR Local Block (SRLB)) or a global (SR Global Block (SRGB)) 119 SID. As per Section 6.4 of [I-D.ietf-spring-segment-routing-policy] 120 a BSID can also be associated with any type of interfaces or tunnel 121 to enable the use of a non-SR interface or tunnels as segments in a 122 SID-list. 124 [RFC5440] describes the Path Computation Element Protocol (PCEP) for 125 communication between a Path Computation Client (PCC) and a PCE or 126 between a pair of PCEs as per [RFC4655]. [RFC8231] specifies 127 extension to PCEP that allows a PCC to delegate its LSPs to a 128 stateful PCE. A stateful PCE can then update the state of LSPs 129 delegated to it. [RFC8281] specifies a mechanism allowing a PCE to 130 dynamically instantiate an LSP on a PCC by sending the path and 131 characteristics. The PCEP extension to setup and maintain SR-TE 132 paths is specified in [I-D.ietf-pce-segment-routing]. 134 [I-D.ietf-pce-segment-routing] provides a mechanism for a network 135 controller (acting as a PCE) to instantiate candidate paths for an SR 136 Policy onto a head-end node (acting as a PCC) using PCEP. For more 137 information on the SR Policy Architecture, see 138 [I-D.ietf-spring-segment-routing-policy]. 140 Binding label/SID has local significance to the ingress node of the 141 corresponding TE path. When a stateful PCE is deployed for setting 142 up TE paths, it may be desirable to report the binding label or SID 143 to the stateful PCE for the purpose of enforcing end-to-end TE/SR 144 policy. A sample Data Center (DC) use-case is illustrated in the 145 following diagram. In the MPLS DC network, an SR LSP (without 146 traffic engineering) is established using a prefix SID advertised by 147 BGP (see [I-D.ietf-idr-bgp-prefix-sid]). In IP/MPLS WAN, an SR-TE 148 LSP is setup using the PCE. The list of SIDs of the SR-TE LSP is {A, 149 B, C, D}. The gateway node 1 (which is the PCC) allocates a binding 150 SID X and reports it to the PCE. In order for the access node to 151 steer the traffic over the SR-TE LSP, the PCE passes the SID stack 152 {Y, X} where Y is the prefix SID of the gateway node-1 to the access 153 node. In the absence of the binding SID X, the PCE should pass the 154 SID stack {Y, A, B, C, D} to the access node. This example also 155 illustrates the additional benefit of using the binding SID to reduce 156 the number of SIDs imposed on the access nodes with a limited 157 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 (TC, S, and TTL) fields MUST be considered invalid. 267 The Length MUST be set to 6. 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. 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. 277 Reserved: MUST be set to 0 while sending and ignored on receipt. 279 Binding Value: A variable length field, padded with trailing zeros to 280 a 4-byte boundary. For the BT as 0, the 20 bits represents the MPLS 281 label. For the BT as 1, the 32-bits represents the label stack entry 282 as per [RFC5462]. For the BT as 2, the 128-bits represent the SRv6 283 SID. 285 4. Operation 287 The binding value is allocated by the PCC and reported to a PCE via 288 PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV, 289 it would ignore the TLV in accordance with ([RFC5440]). If a PCE 290 recognizes the TLV but does not support the TLV, it MUST send PCErr 291 with Error-Type = 2 (Capability not supported). 293 If a TE-PATH-BINDING TLV is absent in PCRpt message, PCE MUST assume 294 that the corresponding LSP does not have any binding. If there are 295 more than one TE-PATH-BINDING TLVs, only the first TLV MUST be 296 processed and the rest MUST be silently ignored. If a PCE recognizes 297 an invalid binding value (e.g., label value from the reserved label 298 space when MPLS label binding is used), it MUST send the PCErr 299 message with Error-Type = 10 ("Reception of an invalid object") and 300 Error Value = 2 ("Bad label value") as specified in 301 [I-D.ietf-pce-segment-routing]. 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 2). 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 [I-D.ietf-pce-segment-routing] defines a new ERO subobject "SR-ERO 355 subobject" capable of carrying a SID as well as the identity of the 356 node/adjacency (NAI) represented by the SID. The NAI Type (NT) field 357 indicates the type and format of the NAI contained in the SR-ERO. In 358 case of binding SID, the NAI MUST NOT be included and NT MUST be set 359 to zero. So as per Section 5.2.1 of [I-D.ietf-pce-segment-routing], 360 for NT=0, the F bit is set to 1, the S bit needs to be zero and the 361 Length is 8. Further the M bit is set. If these conditions are not 362 met, the entire ERO MUST be considered invalid and a PCErr message is 363 sent with Error-Type = 10 ("Reception of an invalid object") and 364 Error-Value = 11 ("Malformed object"). 366 6. Binding SID in SRv6-ERO/ 368 [I-D.ietf-pce-segment-routing] defines a new ERO subobject "SRv6-ERO 369 subobject" for SRv6 SID. The NAI MUST NOT be included and NT MUST be 370 set to zero. So as per Section 5.2.1 of 371 [I-D.ietf-pce-segment-routing], for NT=0, the F bit is set to 1, the 372 S bit needs to be zero and the Length is 24. If these conditions are 373 not met, the entire ERO is considered invalid and a PCErr message is 374 sent with Error-Type = 10 ("Reception of an invalid object") and 375 Error-Value = 11 ("Malformed object") (as per 376 [I-D.ietf-pce-segment-routing]). 378 7. Implementation Status 380 [Note to the RFC Editor - remove this section before publication, as 381 well as remove the reference to RFC 7942.] 383 This section records the status of known implementations of the 384 protocol defined by this specification at the time of posting of this 385 Internet-Draft, and is based on a proposal described in [RFC7942]. 386 The description of implementations in this section is intended to 387 assist the IETF in its decision processes in progressing drafts to 388 RFCs. Please note that the listing of any individual implementation 389 here does not imply endorsement by the IETF. Furthermore, no effort 390 has been spent to verify the information presented here that was 391 supplied by IETF contributors. This is not intended as, and must not 392 be construed to be, a catalog of available implementations or their 393 features. Readers are advised to note that other implementations may 394 exist. 396 According to [RFC7942], "this will allow reviewers and working groups 397 to assign due consideration to documents that have the benefit of 398 running code, which may serve as evidence of valuable experimentation 399 and feedback that have made the implemented protocols more mature. 400 It is up to the individual working groups to use this information as 401 they see fit". 403 7.1. Huawei 405 o Organization: Huawei 407 o Implementation: Huawei's Router and Controller 409 o Description: An experimental code-point is used and plan to 410 request early code-point allocation from IANA after WG adoption. 412 o Maturity Level: Production 414 o Coverage: Full 416 o Contact: chengli13@huawei.com 418 8. Security Considerations 420 The security considerations described in [RFC5440], [RFC8231], 421 [RFC8281] and [I-D.ietf-pce-segment-routing] are applicable to this 422 specification. No additional security measure is required. 424 As described [I-D.ietf-pce-segment-routing], SR allows a network 425 controller to instantiate and control paths in the network. A rouge 426 PCE can manipulate binding SID allocations to move traffic around for 427 some other LSPs that uses BSID in its SR-ERO. 429 Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions 430 only be activated on authenticated and encrypted sessions across PCEs 431 and PCCs belonging to the same administrative authority, using 432 Transport Layer Security (TLS) [RFC8253], as per the recommendations 433 and best current practices in BCP195 [RFC7525] (unless explicitly set 434 aside in [RFC8253]). 436 9. Manageability Considerations 438 All manageability requirements and considerations listed in 439 [RFC5440], [RFC8231], and [I-D.ietf-pce-segment-routing] apply to 440 PCEP protocol extensions defined in this document. In addition, 441 requirements and considerations listed in this section apply. 443 9.1. Control of Function and Policy 445 A PCC implementation SHOULD allow the operator to configure the 446 policy based on which PCC needs to allocates the binding label/SID. 448 9.2. Information and Data Models 450 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 451 include policy configuration for binding label/SID allocation. 453 9.3. Liveness Detection and Monitoring 455 Mechanisms defined in this document do not imply any new liveness 456 detection and monitoring requirements in addition to those already 457 listed in [RFC5440]. 459 9.4. Verify Correct Operations 461 Mechanisms defined in this document do not imply any new operation 462 verification requirements in addition to those already listed in 463 [RFC5440], [RFC8231], and [I-D.ietf-pce-segment-routing]. 465 9.5. Requirements On Other Protocols 467 Mechanisms defined in this document do not imply any new requirements 468 on other protocols. 470 9.6. Impact On Network Operations 472 Mechanisms defined in [RFC5440], [RFC8231], and 473 [I-D.ietf-pce-segment-routing] also apply to PCEP extensions defined 474 in this document. Further, the mechanism described in this document 475 can help the operator to request control of the LSPs at a particular 476 PCE. 478 10. IANA Considerations 480 10.1. PCEP TLV Type Indicators 482 This document defines a new PCEP TLV; IANA is requested to make the 483 following allocations from the "PCEP TLV Type Indicators" sub- 484 registry of the PCEP Numbers registry, as follows: 486 Value Name Reference 488 TBD1 TE-PATH-BINDING This document 490 10.1.1. TE-PATH-BINDING TLV 492 IANA is requested to create a sub-registry to manage the value of the 493 Binding Type field in the TE-PATH-BINDING TLV. 495 Value Description Reference 497 0 MPLS Label This document 498 1 MPLS Label Stack This document 499 Entry 500 2 SRv6 SID This document 502 10.2. PCEP Error Type and Value 504 This document defines a new Error-type and Error-Values for the PCErr 505 message. IANA is requested to allocate new error-type and error- 506 values within the "PCEP-ERROR Object Error Types and Values" 507 subregistry of the PCEP Numbers registry, as follows: 509 Error-Type Meaning 510 ---------- ------- 511 TBD2 Binding label/SID failure: 513 Error-value = TBD3: Invalid SID 514 Error-value = TBD4: Unable to allocate 515 the specified 516 label/SID 518 11. Acknowledgements 520 We like to thank Milos Fabian for his valuable comments. 522 12. References 524 12.1. Normative References 526 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 527 Requirement Levels", BCP 14, RFC 2119, 528 DOI 10.17487/RFC2119, March 1997, 529 . 531 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 532 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 533 DOI 10.17487/RFC5440, March 2009, 534 . 536 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 537 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 538 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 539 2009, . 541 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 542 "Recommendations for Secure Use of Transport Layer 543 Security (TLS) and Datagram Transport Layer Security 544 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 545 2015, . 547 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 548 Code: The Implementation Status Section", BCP 205, 549 RFC 7942, DOI 10.17487/RFC7942, July 2016, 550 . 552 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 553 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 554 May 2017, . 556 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 557 Computation Element Communication Protocol (PCEP) 558 Extensions for Stateful PCE", RFC 8231, 559 DOI 10.17487/RFC8231, September 2017, 560 . 562 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 563 "PCEPS: Usage of TLS to Provide a Secure Transport for the 564 Path Computation Element Communication Protocol (PCEP)", 565 RFC 8253, DOI 10.17487/RFC8253, October 2017, 566 . 568 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 569 Computation Element Communication Protocol (PCEP) 570 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 571 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 572 . 574 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 575 Decraene, B., Litkowski, S., and R. Shakir, "Segment 576 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 577 July 2018, . 579 [I-D.ietf-pce-segment-routing] 580 Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 581 and J. Hardwick, "PCEP Extensions for Segment Routing", 582 draft-ietf-pce-segment-routing-16 (work in progress), 583 March 2019. 585 12.2. Informative References 587 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 588 Element (PCE)-Based Architecture", RFC 4655, 589 DOI 10.17487/RFC4655, August 2006, 590 . 592 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 593 Architecture for Use of PCE and the PCE Communication 594 Protocol (PCEP) in a Network with Central Control", 595 RFC 8283, DOI 10.17487/RFC8283, December 2017, 596 . 598 [I-D.ietf-spring-segment-routing-policy] 599 Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and 600 P. Mattes, "Segment Routing Policy Architecture", draft- 601 ietf-spring-segment-routing-policy-03 (work in progress), 602 May 2019. 604 [I-D.ietf-idr-bgp-prefix-sid] 605 Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A., 606 and H. Gredler, "Segment Routing Prefix SID extensions for 607 BGP", draft-ietf-idr-bgp-prefix-sid-27 (work in progress), 608 June 2018. 610 [I-D.ietf-pce-pcep-extension-for-pce-controller] 611 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 612 and Protocol Extensions for Using PCE as a Central 613 Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 614 extension-for-pce-controller-02 (work in progress), July 615 2019. 617 [I-D.ietf-pce-pcep-yang] 618 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 619 YANG Data Model for Path Computation Element 620 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 621 yang-13 (work in progress), October 2019. 623 Appendix A. Contributor Addresses 625 Dhruv Dhody 626 Huawei Technologies 627 Divyashree Techno Park, Whitefield 628 Bangalore, Karnataka 560066 629 India 631 EMail: dhruv.ietf@gmail.com 633 Mahendra Singh Negi 635 EMail: mahend.ietf@gmail.com 637 Authors' Addresses 639 Siva Sivabalan 640 Cisco Systems, Inc. 641 2000 Innovation Drive 642 Kanata, Ontario K2K 3E8 643 Canada 645 EMail: msiva@cisco.com 647 Clarence Filsfils 648 Cisco Systems, Inc. 649 Pegasus Parc 650 De kleetlaan 6a, DIEGEM BRABANT 1831 651 BELGIUM 653 EMail: cfilsfil@cisco.com 655 Jeff Tantsura 656 Apstra, Inc. 658 EMail: jefftant.ietf@gmail.com 660 Jonathan Hardwick 661 Metaswitch Networks 662 100 Church Street 663 Enfield, Middlesex 664 UK 666 EMail: Jonathan.Hardwick@metaswitch.com 667 Stefano Previdi 668 Huawei Technologies 670 EMail: stefano@previdi.net 672 Cheng Li 673 Huawei Technologies 674 Huawei Campus, No. 156 Beiqing Rd. 675 Beijing 100095 676 China 678 EMail: chengli13@huawei.com