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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-19) exists of draft-ietf-lsr-isis-srv6-extensions-14 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-11 == Outdated reference: A later version (-15) exists of draft-ietf-lsr-ospfv3-srv6-extensions-02 == Outdated reference: A later version (-14) exists of draft-ietf-idr-bgpls-srv6-ext-07 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-16 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group C. Li 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track M. Negi 5 Expires: November 29, 2021 RtBrick Inc 6 S. Sivabalan 7 Ciena Corporation 8 M. Koldychev 9 Cisco Systems, Inc. 10 P. Kaladharan 11 RtBrick Inc 12 Y. Zhu 13 China Telecom 14 May 28, 2021 16 PCEP Extensions for Segment Routing leveraging the IPv6 data plane 17 draft-ietf-pce-segment-routing-ipv6-09 19 Abstract 21 The Source Packet Routing in Networking (SPRING) architecture 22 describes how Segment Routing (SR) can be used to steer packets 23 through an IPv6 or MPLS network using the source routing paradigm. 24 SR enables any head-end node to select any path without relying on a 25 hop-by-hop signaling technique (e.g., LDP or RSVP-TE). 27 It depends only on "segments" that are advertised by Link- State 28 IGPs. A Segment Routed Path can be derived from a variety of 29 mechanisms, including an IGP Shortest Path Tree (SPT), explicit 30 configuration, or a Path Computation Element (PCE). 32 Since SR can be applied to both MPLS and IPv6 forwarding plane, a PCE 33 should be able to compute SR-Path for both MPLS and IPv6 forwarding 34 plane. This document describes the extensions required for SR 35 support for IPv6 data plane in Path Computation Element communication 36 Protocol (PCEP). The PCEP extension and mechanism to support SR-MPLS 37 is described in RFC 8664. This document extends it to support SRv6 38 (SR over IPv6). 40 Requirements Language 42 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 43 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 44 "OPTIONAL" in this document are to be interpreted as described in BCP 45 14 [RFC2119] [RFC8174] when, and only when, they appear in all 46 capitals, as shown here. 48 Status of This Memo 50 This Internet-Draft is submitted in full conformance with the 51 provisions of BCP 78 and BCP 79. 53 Internet-Drafts are working documents of the Internet Engineering 54 Task Force (IETF). Note that other groups may also distribute 55 working documents as Internet-Drafts. The list of current Internet- 56 Drafts is at https://datatracker.ietf.org/drafts/current/. 58 Internet-Drafts are draft documents valid for a maximum of six months 59 and may be updated, replaced, or obsoleted by other documents at any 60 time. It is inappropriate to use Internet-Drafts as reference 61 material or to cite them other than as "work in progress." 63 This Internet-Draft will expire on November 29, 2021. 65 Copyright Notice 67 Copyright (c) 2021 IETF Trust and the persons identified as the 68 document authors. All rights reserved. 70 This document is subject to BCP 78 and the IETF Trust's Legal 71 Provisions Relating to IETF Documents 72 (https://trustee.ietf.org/license-info) in effect on the date of 73 publication of this document. Please review these documents 74 carefully, as they describe your rights and restrictions with respect 75 to this document. Code Components extracted from this document must 76 include Simplified BSD License text as described in Section 4.e of 77 the Trust Legal Provisions and are provided without warranty as 78 described in the Simplified BSD License. 80 Table of Contents 82 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 83 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 84 3. Overview of PCEP Operation in SRv6 Networks . . . . . . . . . 5 85 3.1. Operation Overview . . . . . . . . . . . . . . . . . . . 6 86 3.2. SRv6-Specific PCEP Message Extensions . . . . . . . . . . 7 87 4. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 7 88 4.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 7 89 4.1.1. The SRv6 PCE Capability sub-TLV . . . . . . . . . . . 7 90 4.2. The RP/SRP Object . . . . . . . . . . . . . . . . . . . . 9 91 4.3. ERO . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 92 4.3.1. SRv6-ERO Subobject . . . . . . . . . . . . . . . . . 9 93 4.3.1.1. SID Structure . . . . . . . . . . . . . . . . . . 11 94 4.4. RRO . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 95 4.4.1. SRv6-RRO Subobject . . . . . . . . . . . . . . . . . 13 97 5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 14 98 5.1. Exchanging the SRv6 Capability . . . . . . . . . . . . . 14 99 5.2. ERO Processing . . . . . . . . . . . . . . . . . . . . . 15 100 5.2.1. SRv6 ERO Validation . . . . . . . . . . . . . . . . . 15 101 5.2.2. Interpreting the SRv6-ERO . . . . . . . . . . . . . . 16 102 5.3. RRO Processing . . . . . . . . . . . . . . . . . . . . . 17 103 6. Security Considerations . . . . . . . . . . . . . . . . . . . 17 104 7. Manageability Considerations . . . . . . . . . . . . . . . . 17 105 7.1. Control of Function and Policy . . . . . . . . . . . . . 17 106 7.2. Information and Data Models . . . . . . . . . . . . . . . 17 107 7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 17 108 7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 18 109 7.5. Requirements On Other Protocols . . . . . . . . . . . . . 18 110 7.6. Impact On Network Operations . . . . . . . . . . . . . . 18 111 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 18 112 8.1. Cisco's Commercial Delivery . . . . . . . . . . . . . . . 18 113 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 114 9.1. PCEP ERO and RRO subobjects . . . . . . . . . . . . . . . 19 115 9.2. New SRv6-ERO Flag Registry . . . . . . . . . . . . . . . 19 116 9.3. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators . . . 20 117 9.4. SRv6 PCE Capability Flags . . . . . . . . . . . . . . . . 20 118 9.5. New Path Setup Type . . . . . . . . . . . . . . . . . . . 21 119 9.6. ERROR Objects . . . . . . . . . . . . . . . . . . . . . . 21 120 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 121 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 122 11.1. Normative References . . . . . . . . . . . . . . . . . . 21 123 11.2. Informative References . . . . . . . . . . . . . . . . . 23 124 Appendix A. Contributor . . . . . . . . . . . . . . . . . . . . 25 125 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 127 1. Introduction 129 As per [RFC8402], with Segment Routing (SR), a node steers a packet 130 through an ordered list of instructions, called segments. A segment 131 can represent any instruction, topological or service-based. A 132 segment can have a semantic local to an SR node or global within an 133 SR domain. SR allows to enforce a flow through any path and service 134 chain while maintaining per-flow state only at the ingress node of 135 the SR domain. Segments can be derived from different components: 136 IGP, BGP, Services, Contexts, Locater, etc. The list of segment 137 forming the path is called the Segment List and is encoded in the 138 packet header. Segment Routing can be applied to the IPv6 139 architecture with the Segment Routing Header (SRH) [RFC8754]. A 140 segment is encoded as an IPv6 address. An ordered list of segments 141 is encoded as an ordered list of IPv6 addresses in the routing 142 header. The active segment is indicated by the Destination Address 143 of the packet. Upon completion of a segment, a pointer in the new 144 routing header is incremented and indicates the next segment. 146 Segment Routing use cases are described in [RFC7855] and [RFC8354]. 147 Segment Routing protocol extensions are defined in [RFC8667], and 148 [RFC8666]. 150 As per [RFC8754], an SRv6 Segment is a 128-bit value. "SRv6 SID" or 151 simply "SID" are often used as a shorter reference for "SRv6 152 Segment". Further details are in an illustration provided in 153 [I-D.ietf-spring-srv6-network-programming]. 155 The SR architecture can be applied to the MPLS forwarding plane 156 without any change, in which case an SR path corresponds to an MPLS 157 Label Switching Path (LSP). The SR is applied to IPV6 forwarding 158 plane using SRH. A SR path can be derived from an IGP Shortest Path 159 Tree (SPT), but SR-TE paths may not follow IGP SPT. Such paths may 160 be chosen by a suitable network planning tool, or a PCE and 161 provisioned on the ingress node. 163 [RFC5440] describes Path Computation Element communication Protocol 164 (PCEP) for communication between a Path Computation Client (PCC) and 165 a Path Computation Element (PCE) or between a pair of PCEs. A PCE or 166 a PCC operating as a PCE (in hierarchical PCE environment) computes 167 paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs) based on 168 various constraints and optimization criteria. [RFC8231] specifies 169 extensions to PCEP that allow a stateful PCE to compute and recommend 170 network paths in compliance with [RFC4657] and defines objects and 171 TLVs for MPLS-TE LSPs. Stateful PCEP extensions provide 172 synchronization of LSP state between a PCC and a PCE or between a 173 pair of PCEs, delegation of LSP control, reporting of LSP state from 174 a PCC to a PCE, controlling the setup and path routing of an LSP from 175 a PCE to a PCC. Stateful PCEP extensions are intended for an 176 operational model in which LSPs are configured on the PCC, and 177 control over them is delegated to the PCE. 179 A mechanism to dynamically initiate LSPs on a PCC based on the 180 requests from a stateful PCE or a controller using stateful PCE is 181 specified in [RFC8281]. As per [RFC8664], it is possible to use a 182 stateful PCE for computing one or more SR-TE paths taking into 183 account various constraints and objective functions. Once a path is 184 chosen, the stateful PCE can initiate an SR-TE path on a PCC using 185 PCEP extensions specified in [RFC8281] using the SR specific PCEP 186 extensions specified in [RFC8664]. [RFC8664] specifies PCEP 187 extensions for supporting a SR-TE LSP for MPLS data plane. This 188 document extends [RFC8664] to support SR for IPv6 data plane. 189 Additionally, using procedures described in this document, a PCC can 190 request an SRv6 path from either stateful or a stateless PCE. This 191 specification relies on the PATH-SETUP-TYPE TLV and procedures 192 specified in [RFC8408]. 194 This specification provides a mechanism for a network controller 195 (acting as a PCE) to instantiate candidate paths for an SR Policy 196 onto a head-end node (acting as a PCC) using PCEP. For more 197 information on the SR Policy Architecture, see 198 [I-D.ietf-spring-segment-routing-policy]. 200 2. Terminology 202 This document uses the following terms defined in [RFC5440]: PCC, 203 PCE, PCEP Peer. 205 This document uses the following terms defined in [RFC8051]: Stateful 206 PCE, Delegation. 208 The message formats in this document are specified using Routing 209 Backus-Naur Format (RBNF) encoding as specified in [RFC5511]. 211 NAI: Node or Adjacency Identifier. 213 PCC: Path Computation Client. 215 PCE: Path Computation Element. 217 PCEP: Path Computation Element Protocol. 219 SR: Segment Routing. 221 SID: Segment Identifier. 223 SRv6: Segment Routing for IPv6 forwarding plane. 225 SRH: IPv6 Segment Routing Header. 227 SR Path: IPv6 Segment List (List of IPv6 SIDs representing a path in 228 IPv6 SR domain) 230 Further, note that the term LSP used in the PCEP specifications, 231 would be equivalent to a SRv6 Path (represented as a list of SRv6 232 segments) in the context of supporting SRv6 in PCEP. 234 3. Overview of PCEP Operation in SRv6 Networks 236 Basic operations for PCEP speakers is as per [RFC8664]. SRv6 Paths 237 computed by a PCE can be represented as an ordered list of SRv6 238 segments of 128-bit value. "SRv6 SID" or simply "SID" are often used 239 as a shorter reference for "SRv6 Segment" in this document. 241 [RFC8664] defined a new Explicit Route Object (ERO) subobject denoted 242 by "SR-ERO subobject" capable of carrying a SID as well as the 243 identity of the node/adjacency represented by the SID. SR-capable 244 PCEP speakers should be able to generate and/or process such ERO 245 subobject. An ERO containing SR-ERO subobjects can be included in 246 the PCEP Path Computation Reply (PCRep) message defined in [RFC5440], 247 the PCEP LSP Initiate Request message (PCInitiate) defined in 248 [RFC8281], as well as in the PCEP LSP Update Request (PCUpd) and PCEP 249 LSP State Report (PCRpt) messages defined in defined in [RFC8231]. 251 This document define new subobjects "SRv6-ERO" and "SRv6-RRO" in ERO 252 and RRO respectively to carry SRv6 SID (IPv6 Address). SRv6-capable 253 PCEP speakers MUST be able to generate and/or process this. 255 When a PCEP session between a PCC and a PCE is established, both PCEP 256 speakers exchange their capabilities to indicate their ability to 257 support SRv6 specific functionality. 259 In summary, this document: 261 o Defines a new PCEP capability for SRv6. 263 o Defines a new subobject SRv6-ERO in ERO. 265 o Defines a new subobject SRv6-RRO in RRO. 267 o Defines a new path setup type carried in the PATH-SETUP-TYPE TLV 268 and the PATH-SETUP-TYPE-CAPABILITY TLV. 270 3.1. Operation Overview 272 In SR networks, an ingress node of an SR path appends all outgoing 273 packets with an SR header consisting of a list of SIDs (IPv6 Prefix 274 in case of SRv6). The header has all necessary information to guide 275 the packets from the ingress node to the egress node of the path, and 276 hence there is no need for any signaling protocol. 278 For IPv6 in control plane with MPLS data-plane, mechanism remains 279 same as [RFC8664] 281 This document describes extensions to SR path for IPv6 data plane. 282 SRv6 Path (i.e. ERO) consists of an ordered set of SRv6 SIDs(see 283 details in Figure 2). 285 A PCC or PCE indicates its ability to support SRv6 during the PCEP 286 session Initialization Phase via a new SRv6-PCE-CAPABILITY sub-TLV 287 (see details in Section 4.1.1). 289 3.2. SRv6-Specific PCEP Message Extensions 291 As defined in [RFC5440], a PCEP message consists of a common header 292 followed by a variable length body made up of mandatory and/or 293 optional objects. This document does not require any changes in the 294 format of PCReq and PCRep messages specified in [RFC5440], PCInitiate 295 message specified in [RFC8281], and PCRpt and PCUpd messages 296 specified in [RFC8231]. However, PCEP messages pertaining to SRv6 297 MUST include PATH-SETUP-TYPE TLV in the RP or SRP object to clearly 298 identify that SRv6 is intended. 300 4. Object Formats 302 4.1. The OPEN Object 304 4.1.1. The SRv6 PCE Capability sub-TLV 306 This document defines a new Path Setup Type (PST) [RFC8408] for SRv6, 307 as follows: 309 o PST = TBD2: Path is setup using SRv6. 311 A PCEP speaker MUST indicate its support of the function described in 312 this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN 313 object with this new PST included in the PST list. 315 This document also defines the SRv6-PCE-CAPABILITY sub-TLV. PCEP 316 speakers use this sub-TLV to exchange information about their SRv6 317 capability. If a PCEP speaker includes PST=TBD2 in the PST List of 318 the PATH-SETUP-TYPE-CAPABILITY TLV then it MUST also include the 319 SRv6-PCE-CAPABILITY sub-TLV inside the PATH-SETUP-TYPE-CAPABILITY 320 TLV. 322 The format of the SRv6-PCE-CAPABILITY sub-TLV is shown in the 323 following figure: 325 0 1 2 3 326 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 1 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | Type=TBD1 | Length | 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 330 | Reserved | Flags |N|X| 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 | MSD-Type | MSD-Value | MSD-Type | MSD-Value | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 // ... // 335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 336 | MSD-Type | MSD-Value | Padding | 337 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 Figure 1: SRv6-PCE-CAPABILITY sub-TLV format 341 The code point for the TLV type (TBD1) is to be defined by IANA. The 342 TLV length is variable. 344 The value comprises of - 346 Reserved: 2 octet, this field MUST be set to 0 on transmission, 347 and ignored on receipt. 349 Flags: 2 octet, two bits are currently assigned in this document. 351 N bit: A PCC sets this flag bit to 1 to indicate that it is 352 capable of resolving a Node or Adjacency Identifier (NAI) to a 353 SRv6-SID. 355 X bit: A PCC sets this bit to 1 to indicate that it does not 356 impose any limit on MSD (irrespective of the MSD-Type). 358 Unassigned bits MUST be set to 0 and ignored on receipt. 360 A pair of (MSD-Type, MSD-Value): Where MSD-Type (1 octet) is as 361 per the IGP MSD Type registry created by [RFC8491] and populated 362 with SRv6 MSD types as per [I-D.ietf-lsr-isis-srv6-extensions]; 363 MSD-Value (1 octet) is as per [RFC8491]. 365 This sub-TLV format is compliant with the PCEP TLV format defined in 366 [RFC5440]. That is, the sub-TLV is composed of 2 octets for the 367 type, 2 octets specifying the length, and a Value field. The Type 368 field when set to TBD1 identifies the SRv6-PCE-CAPABILITY sub-TLV and 369 the presence of the sub-TLV indicates the support for the SRv6 paths 370 in PCEP. The Length field defines the length of the value portion in 371 octets. The TLV is padded to 4-octet alignment, and padding is not 372 included in the Length field. The number of (MSD-Type,MSD-Value) 373 pairs can be determined from the Length field of the TLV. 375 4.2. The RP/SRP Object 377 In order to indicate the SRv6 path, RP or SRP object MUST include the 378 PATH-SETUP-TYPE TLV specified in [RFC8408]. This document defines a 379 new Path Setup Type (PST=TBD2) for SRv6. 381 The LSP-IDENTIFIERS TLV MAY be present for the above PST type. 383 4.3. ERO 385 In order to support SRv6, new subobject "SRv6-ERO" is defined in ERO. 387 4.3.1. SRv6-ERO Subobject 389 An SRv6-ERO subobject is formatted as shown in the following figure. 391 0 1 2 3 392 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 1 393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 394 |L| Type=TBD3 | Length | NT | Flags |V|T|F|S| 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | Reserved | Endpoint Behavior | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 | | 399 | SRv6 SID (optional) | 400 | (128-bit) | 401 | | 402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 403 // NAI (variable, optional) // 404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 405 | SID Structure (optional) | 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 Figure 2: SRv6-ERO Subobject Format 410 The fields in the SRv6-ERO Subobject are as follows: 412 The 'L' Flag: Indicates whether the subobject represents a loose-hop 413 (see [RFC3209]). If this flag is set to zero, a PCC MUST NOT 414 overwrite the SID value present in the SRv6-ERO subobject. 415 Otherwise, a PCC MAY expand or replace one or more SID values in the 416 received SRv6-ERO based on its local policy. 418 Type: indicates the content of the subobject, i.e. when the field is 419 set to TBD3, the suboject is a SRv6-ERO subobject representing a SRv6 420 SID. 422 Length: Contains the total length of the subobject in octets. The 423 Length MUST be at least 24, and MUST be a multiple of 4. An SRv6-ERO 424 subobject MUST contain at least one of a SRv6-SID or an NAI. The S 425 and F bit in the Flags field indicates whether the SRv6-SID or NAI 426 fields are absent. 428 NAI Type (NT): Indicates the type and format of the NAI contained in 429 the object body, if any is present. If the F bit is set to zero (see 430 below) then the NT field has no meaning and MUST be ignored by the 431 receiver. This document reuses NT types defined in [RFC8664]: 433 If NT value is 0, the NAI MUST NOT be included. 435 When NT value is 2, the NAI is as per the 'IPv6 Node ID' format 436 defined in [RFC8664], which specifies an IPv6 address. This is 437 used to identify the owner of the SRv6 Identifier. This is 438 optional, as the LOC (the locater portion) of the SRv6 SID serves 439 a similar purpose (when present). 441 When NT value is 4, the NAI is as per the 'IPv6 Adjacency' format 442 defined in [RFC8664], which specify a pair of IPv6 addresses. 443 This is used to identify the IPv6 Adjacency and used with the SRv6 444 Adj-SID. 446 When NT value is 6, the NAI is as per the 'link-local IPv6 447 addresses' format defined in [RFC8664], which specify a pair of 448 (global IPv6 address, interface ID) tuples. It is used to 449 identify the IPv6 Adjacency and used with the SRv6 Adj-SID. 451 SR-MPLS specific NT types are not valid in SRv6-ERO. 453 Flags: Used to carry additional information pertaining to the 454 SRv6-SID. This document defines the following flag bits. The other 455 bits MUST be set to zero by the sender and MUST be ignored by the 456 receiver. 458 o S: When this bit is set to 1, the SRv6-SID value in the subobject 459 body is absent. In this case, the PCC is responsible for choosing 460 the SRv6-SID value, e.g., by looking up in the SR-DB using the NAI 461 which, in this case, MUST be present in the subobject. If the S 462 bit is set to 1 then F bit MUST be set to zero. 464 o F: When this bit is set to 1, the NAI value in the subobject body 465 is absent. The F bit MUST be set to 1 if NT=0, and otherwise MUST 466 be set to zero. The S and F bits MUST NOT both be set to 1. 468 o T: When this bit is set to 1, the SID Structure value in the 469 subobject body is present. The T bit MUST be set to 0 when S bit 470 is set to 1. If the T bit is set when the S bit is set, the T bit 471 MUST be ignored. Thus, the T bit indicates the presence of an 472 optional 8-byte SID Structure when SRv6 SID is included. The SID 473 Structure is defined in Section 4.3.1.1. 475 o V: The "SID verification" bit usage is as per Section 5.1 of 476 [I-D.ietf-spring-segment-routing-policy]. 478 Reserved: MUST be set to zero while sending and ignored on receipt. 480 Endpoint Behavior: A 16 bit field representing the behavior 481 associated with the SRv6 SIDs. This information is optional and 482 plays no role in the fields in SRH imposed on the packet. It could 483 be used for maintainability and diagnostic purpose. If behavior is 484 not known, 0 is used. The list of Endpoint behavior are defined in 485 [I-D.ietf-spring-srv6-network-programming]. 487 SRv6 SID: SRv6 Identifier is the 128 bit IPv6 addresses representing 488 the SRv6 segment. 490 NAI: The NAI associated with the SRv6-SID. The NAI's format depends 491 on the value in the NT field, and is described in [RFC8664]. 493 At least one of the SRv6-SID or the NAI MUST be included in the 494 SRv6-ERO subobject, and both MAY be included. 496 4.3.1.1. SID Structure 498 The SID Structure is an optional part of the SR-ERO subobject, as 499 described in Section 4.3.1. It is formatted as shown in the 500 following figure. 502 0 1 2 3 503 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 1 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | LB Length | LN Length | Fun. Length | Arg. Length | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | Reserved | Flags | 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 Figure 3: SID Structure Format 512 where: 514 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 516 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 518 Fun. Length: 1 octet. SRv6 SID Function length in bits. 520 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. 522 The sum of all four sizes in the SID Structure must be lower or equal 523 to 128 bits. If the sum of all four sizes advertised in the SID 524 Structure is larger than 128 bits, the corresponding SRv6 SID MUST be 525 considered as an Error. A PCErr message with Error-Type = 10 526 ("Reception of an invalid object") and Error-Value = TBD ("Invalid 527 SRv6 SID Structure"). 529 Reserved: MUST be set to zero while sending and ignored on receipt. 531 Flags: Currentky no flags are defined. Unassigned bits must be set 532 to zero while sending and ignored on receipt. 534 The SRv6 SID Structure TLV provides the detailed encoding information 535 of an SRv6 SID, which is useful in the use cases that require to know 536 the SRv6 SID structure. When a PCEP speaker receives the SRv6 SID 537 and its structure information, the SRv6 SID can be parsed based on 538 the SRv6 SID Structure TLV and/or possible local policies. The 539 cunsumers of SRv6 SID structure MAY be other use cases, and the 540 processing and usage of SRv6 SID structure TLV are different based on 541 use cases. This is out of the scope of this document, and will be 542 described in other documents. 544 4.4. RRO 546 In order to support SRv6, new subobject "SRv6-RRO" is defined in RRO. 548 4.4.1. SRv6-RRO Subobject 550 A PCC reports an SRv6 path to a PCE by sending a PCRpt message, per 551 [RFC8231]. The RRO on this message represents the SID list that was 552 applied by the PCC, that is, the actual path taken. The procedures 553 of [RFC8664] with respect to the RRO apply equally to this 554 specification without change. 556 An RRO contains one or more subobjects called "SRv6-RRO subobjects" 557 whose format is shown below: 559 0 1 2 3 560 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 1 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 | Type=TBD4 | Length | NT | Flags |V|T|F|S| 563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 | Reserved | Endpoint Behavior | 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 | | 567 | SRv6 SID | 568 | (128-bit) | 569 | | 570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 571 // NAI (variable) // 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 | SID Structure (optional) | 574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 576 Figure 4: SRv6-RRO Subobject Format 578 The format of the SRv6-RRO subobject is the same as that of the 579 SRv6-ERO subobject, but without the L flag. 581 The V flag has no meaning in the SRv6-RRO and is ignored on receipt 582 at the PCE. 584 Ordering of SRv6-RRO subobjects by PCC in PCRpt message remains as 585 per [RFC8664]. 587 5. Procedures 589 5.1. Exchanging the SRv6 Capability 591 A PCC indicates that it is capable of supporting the head-end 592 functions for SRv6 by including the SRv6-PCE-CAPABILITY sub-TLV in 593 the Open message that it sends to a PCE. A PCE indicates that it is 594 capable of computing SRv6 paths by including the SRv6-PCE-CAPABILITY 595 sub-TLV in the Open message that it sends to a PCC. 597 If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV with a 598 PST list containing PST=TBD2, but the SRv6-PCE-CAPABILITY sub-TLV is 599 absent, then the PCEP speaker MUST send a PCErr message with Error- 600 Type 10 (Reception of an invalid object) and Error-Value TBD5 (to be 601 assigned by IANA) (Missing PCE-SRv6-CAPABILITY sub-TLV) and MUST then 602 close the PCEP session. If a PCEP speaker receives a PATH-SETUP- 603 TYPE-CAPABILITY TLV with a SRv6-PCE-CAPABILITY sub-TLV, but the PST 604 list does not contain PST=TBD2, then the PCEP speaker MUST ignore the 605 SRv6-PCE-CAPABILITY sub-TLV. 607 The number of SRv6 SIDs that can be imposed on a packet depends on 608 the PCC's IPv6 data plane's capability. If a PCC sets the X flag to 609 1 then the MSD is not used and MUST NOT be included. If a PCE 610 receives an SRv6-PCE-CAPABILITY sub-TLV with the X flag set to 1 then 611 it MUST ignore any MSD-Type, MSD-Value fields and MUST assume that 612 the sender can impose any length of SRH. If a PCC sets the X flag to 613 zero, then it sets the SRv6 MSD-Type, MSD-Value fields that it can 614 impose on a packet. If a PCE receives an SRv6-PCE-CAPABILITY sub-TLV 615 with the X flag and SRv6 MSD-Type, MSD-Value fields both set to zero 616 then it is considered as an error and the PCE MUST respond with a 617 PCErr message (Error-Type=1 "PCEP session establishment failure" and 618 Error-Value=1 "reception of an invalid Open message or a non Open 619 message."). In case the MSD-Type in SRv6-PCE-CAPABILITY sub-TLV 620 received by the PCE does not correspond to one of the SRv6 MSD types, 621 the PCE MUST respond with a PCErr message (Error-Type=1 "PCEP session 622 establishment failure" and Error-Value=1 "reception of an invalid 623 Open message or a non Open message."). 625 Note that the MSD-Type, MSD-Value exchanged via the SRv6-PCE- 626 CAPABILITY sub-TLV indicates the SRv6 SID imposition limit for the 627 PCC node. However, if a PCE learns these via different means, e.g 628 routing protocols, as specified in: 629 [I-D.ietf-lsr-ospfv3-srv6-extensions]; 630 [I-D.ietf-lsr-isis-srv6-extensions]; [I-D.ietf-idr-bgpls-srv6-ext], 631 then it ignores the values in the SRv6-PCE-CAPABILITY sub-TLV. 632 Furthermore, whenever a PCE learns the other advanced SRv6 MSD via 633 different means, it MUST use that value regardless of the values 634 exchanged in the SRv6-PCE-CAPABILITY sub-TLV. 636 Once an SRv6-capable PCEP session is established with a non-zero SRv6 637 MSD value, the corresponding PCE MUST NOT send SRv6 paths with a 638 number of SIDs exceeding that SRv6 MSD value (based on the SRv6 MSD 639 Type). If a PCC needs to modify the SRv6 MSD value, it MUST close 640 the PCEP session and re-establish it with the new value. If a PCEP 641 session is established with a non-zero SRv6 MSD value, and the PCC 642 receives an SRv6 path containing more SIDs than specified in the SRv6 643 MSD value (based on the SRv6 MSD type), the PCC MUST send a PCErr 644 message with Error-Type 10 (Reception of an invalid object) and 645 Error-Value 3 (Unsupported number of Segment ERO subobjects). If a 646 PCEP session is established with an SRv6 MSD value of zero, then the 647 PCC MAY specify an SRv6 MSD for each path computation request that it 648 sends to the PCE, by including a "maximum SID depth" metric object on 649 the request similar to [RFC8664]. 651 The N flag, X flag and (MSD-Type,MSD-Value) pair inside the SRv6-PCE- 652 CAPABILITY sub-TLV are meaningful only in the Open message sent from 653 a PCC to a PCE. As such, a PCE MUST set the flags to zero and not 654 include any (MSD-Type,MSD-Value) pair in the SRv6-PCE-CAPABILITY sub- 655 TLV in an outbound message to a PCC. Similarly, a PCC MUST ignore 656 N,X flag and any (MSD-Type,MSD-Value) pair received from a PCE. If a 657 PCE receives multiple SRv6-PCE-CAPABILITY sub-TLVs in an Open 658 message, it processes only the first sub-TLV received. 660 5.2. ERO Processing 662 The ERO processing remains as per [RFC5440] and [RFC8664]. 664 5.2.1. SRv6 ERO Validation 666 If a PCC does not support the SRv6 PCE Capability and thus cannot 667 recognize the SRv6-ERO or SRv6-RRO subobjects, it will respond 668 according to the rules for a malformed object per [RFC5440]. 670 On receiving an SRv6-ERO, a PCC MUST validate that the Length field, 671 the S bit, the F bit, the T bit, and the NT field are consistent, as 672 follows. 674 o If NT=0, the F bit MUST be 1, the S bit MUST be zero and the 675 Length MUST be 24. 677 o If NT=2, the F bit MUST be zero. If the S bit is 1, the Length 678 MUST be 24, otherwise the Length MUST be 40. 680 o If NT=4, the F bit MUST be zero. If the S bit is 1, the Length 681 MUST be 40, otherwise the Length MUST be 56. 683 o If NT=6, the F bit MUST be zero. If the S bit is 1, the Length 684 MUST be 48, otherwise the Length MUST be 64. 686 o NT types (1,3, and 5) are not valid for SRv6. 688 o If T bit is 1, then S bit MUST be zero. 690 If a PCC finds that the NT field, Length field, S bit, F bit, and T 691 bit are not consistent, it MUST consider the entire ERO invalid and 692 MUST send a PCErr message with Error-Type = 10 ("Reception of an 693 invalid object") and Error-Value = 11 ("Malformed object"). 695 If a PCEP speaker that does not recognize the NT value received in 696 SRv6-ERO subobject, it would behave as per [RFC8664]. 698 In case a PCEP speaker receives the SRv6-ERO subobject, when the PST 699 is not set to TBD2 or SRv6-PCE-CAPABILITY sub-TLV was not exchanged, 700 it MUST send a PCErr message with Error-Type = 19 ("Invalid 701 Operation") and Error-Value = TBD5 ("Attempted SRv6 when the 702 capability was not advertised"). 704 If a PCC receives a list of SRv6 segments, and the number of SRv6 705 segments exceeds the SRv6 MSD that the PCC can impose on the packet 706 (SRH), it MUST send a PCErr message with Error-Type = 10 ("Reception 707 of an invalid object") and Error-Value = TBD ("Unsupported number of 708 Segment ERO subobjects") as per [RFC8664]. 710 When a PCEP speaker detects that all subobjects of ERO are not of 711 type TBD3, and if it does not handle such ERO, it MUST send a PCErr 712 message with Error-Type = 10 ("Reception of an invalid object") and 713 Error-Value = TBD ("Non-identical ERO subobjects")as per [RFC8664]. 715 5.2.2. Interpreting the SRv6-ERO 717 The SRv6-ERO contains a sequence of subobjects. According to 718 [I-D.ietf-spring-segment-routing-policy], each SRv6-ERO subobject in 719 the sequence identifies a segment that the traffic will be directed 720 to, in the order given. That is, the first subobject identifies the 721 first segment the traffic will be directed to, the second SRv6-ERO 722 subobject represents the second segment, and so on. 724 The PCC interprets the SRv6-ERO by converting it to an SRv6 SRH plus 725 a next hop. The PCC sends packets along the segment routed path by 726 prepending the SRH onto the packets and sending the resulting, 727 modified packet to the next hop. 729 5.3. RRO Processing 731 The syntax checking rules that apply to the SRv6-RRO subobject are 732 identical to those of the SRv6-ERO subobject, except as noted below. 734 If a PCEP speaker receives an SRv6-RRO subobject in which both SRv6 735 SID and NAI are absent, it MUST consider the entire RRO invalid and 736 send a PCErr message with Error-Type = 10 ("Reception of an invalid 737 object") and Error-Value = TBD6 ("Both SID and NAI are absent in 738 SRv6-RRO subobject"). 740 If a PCE detects that the subobjects of an RRO are a mixture of 741 SRv6-RRO subobjects and subobjects of other types, then it MUST send 742 a PCErr message with Error-Type = 10 ("Reception of an invalid 743 object") and Error-Value = TBD7 ("RRO mixes SRv6-RRO subobjects with 744 other subobject types"). 746 6. Security Considerations 748 The security considerations described in [RFC5440], [RFC8231] and 749 [RFC8281], [RFC8664], are applicable to this specification. No 750 additional security measure is required. 752 7. Manageability Considerations 754 All manageability requirements and considerations listed in 755 [RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions 756 defined in this document. In addition, requirements and 757 considerations listed in this section apply. 759 7.1. Control of Function and Policy 761 A PCEP implementation SHOULD allow the operator to configure the 762 policy based on which it allocates the SIDs. 764 7.2. Information and Data Models 766 The PCEP YANG module is defined in [I-D.ietf-pce-pcep-yang]. An 767 implementation SHOULD allow the operator to view the SIDs allocated 768 to the LSP for the SR path. 770 7.3. Liveness Detection and Monitoring 772 Mechanisms defined in this document do not imply any new liveness 773 detection and monitoring requirements in addition to those already 774 listed in [RFC5440]. 776 7.4. Verify Correct Operations 778 Mechanisms defined in this document do not imply any new operation 779 verification requirements in addition to those already listed in 780 [RFC5440], [RFC8231], and [RFC8664] . 782 7.5. Requirements On Other Protocols 784 Mechanisms defined in this document do not imply any new requirements 785 on other protocols. 787 7.6. Impact On Network Operations 789 Mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply 790 to PCEP extensions defined in this document. 792 8. Implementation Status 794 [Note to the RFC Editor - remove this section before publication, as 795 well as remove the reference to [RFC7942]. 797 This section records the status of known implementations of the 798 protocol defined by this specification at the time of posting of this 799 Internet-Draft, and is based on a proposal described in [RFC7942]. 800 The description of implementations in this section is intended to 801 assist the IETF in its decision processes in progressing drafts to 802 RFCs. Please note that the listing of any individual implementation 803 here does not imply endorsement by the IETF. Furthermore, no effort 804 has been spent to verify the information presented here that was 805 supplied by IETF contributors. This is not intended as, and must not 806 be construed to be, a catalog of available implementations or their 807 features. Readers are advised to note that other implementations may 808 exist. 810 According to [RFC7942], "this will allow reviewers and working groups 811 to assign due consideration to documents that have the benefit of 812 running code, which may serve as evidence of valuable experimentation 813 and feedback that have made the implemented protocols more mature. 814 It is up to the individual working groups to use this information as 815 they see fit". 817 8.1. Cisco's Commercial Delivery 819 o Organization: Cisco Systems, Inc. 821 o Implementation: IOS-XR PCE and PCC. 823 o Description: Implementation with experimental codepoints. 825 o Maturity Level: Production 827 o Coverage: Partial 829 o Contact: ssidor@cisco.com 831 9. IANA Considerations 833 9.1. PCEP ERO and RRO subobjects 835 This document defines a new subobject type for the PCEP explicit 836 route object (ERO), and a new subobject type for the PCEP record 837 route object (RRO). The code points for subobject types of these 838 objects is maintained in the RSVP parameters registry, under the 839 EXPLICIT_ROUTE and ROUTE_RECORD objects. IANA is requested to 840 allocate code-points in the RSVP Parameters registry for each of the 841 new subobject types defined in this document. 843 Object Subobject Subobject Type 844 --------------------- -------------------------- ------------------ 845 EXPLICIT_ROUTE SRv6-ERO (PCEP-specific) TBD3 846 ROUTE_RECORD SRv6-RRO (PCEP-specific) TBD4 848 9.2. New SRv6-ERO Flag Registry 850 IANA is requested to create a new sub-registry, named "SRv6-ERO Flag 851 Field", within the "Path Computation Element Protocol (PCEP) Numbers" 852 registry to manage the Flag field of the SRv6-ERO subobject. New 853 values are to be assigned by Standards Action [RFC8126]. Each bit 854 should be tracked with the following qualities: 856 o Bit number (counting from bit 0 as the most significant bit) 858 o Capability description 860 o Defining RFC 862 The following values are defined in this document: 864 Bit Description Reference 865 ----- ------------------ -------------- 866 0-7 Unassigned 867 8 SID Verification (V) This document 868 9 SID Structure is This document 869 present (T) 870 10 NAI is absent (F) This document 871 11 SID is absent (S) This document 873 9.3. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators 875 IANA maintains a sub-registry, named "PATH-SETUP-TYPE-CAPABILITY Sub- 876 TLV Type Indicators", within the "Path Computation Element Protocol 877 (PCEP) Numbers" registry to manage the type indicator space for sub- 878 TLVs of the PATH-SETUP-TYPE-CAPABILITY TLV. IANA is requested to 879 make the following assignment: 881 Value Meaning Reference 882 ----- ------- --------- 883 TBD1 SRv6-PCE-CAPABILITY This Document 885 9.4. SRv6 PCE Capability Flags 887 IANA is requested to create a new sub-registry, named "SRv6 888 Capability Flag Field", within the "Path Computation Element Protocol 889 (PCEP) Numbers" registry to manage the Flag field of the SRv6-PCE- 890 CAPABILITY sub-TLV. New values are to be assigned by Standards 891 Action [RFC8126]. Each bit should be tracked with the following 892 qualities: 894 o Bit number (counting from bit 0 as the most significant bit) 896 o Capability description 898 o Defining RFC 900 The following values are defined in this document: 902 Bit Description Reference 904 0-13 Unassigned 905 14 Node or Adjacency This document 906 Identifier (NAI) is 907 supported (N) 908 15 Unlimited Maximum SID This document 909 Depth (X) 911 9.5. New Path Setup Type 913 [RFC8408] created a sub-registry within the "Path Computation Element 914 Protocol (PCEP) Numbers" registry called "PCEP Path Setup Types". 915 IANA is requested to allocate a new code point within this registry, 916 as follows: 918 Value Description Reference 919 ----- ----------- --------- 920 TBD2 Traffic engineering path is This Document 921 setup using SRv6. 923 9.6. ERROR Objects 925 IANA is requested to allocate code-points in the PCEP-ERROR Object 926 Error Types and Values registry for the following new error-values: 928 Error-Type Meaning 929 ---------- ------- 930 10 Reception of an invalid object 931 Error-value = TBD5 (Missing 932 PCE-SRv6-CAPABILITY sub-TLV) 933 Error-value = TBD6 (Both SID and NAI are absent 934 in SRv6-RRO subobject) 935 Error-value = TBD7 (RRO mixes SRv6-RRO subobjects 936 with other subobject types) 937 Error-value = TBD8 (Invalid SRv6 SID Structure) 938 19 Invalid Operation 939 Error-value = TBD5 (Attempted SRv6 when the 940 capability was not advertised) 942 10. Acknowledgements 944 The authors would like to thank Jeff Tentsura, Adrian Farrel, Aijun 945 Wang and Khasanov Boris for valuable suggestions. 947 11. References 949 11.1. Normative References 951 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 952 Requirement Levels", BCP 14, RFC 2119, 953 DOI 10.17487/RFC2119, March 1997, 954 . 956 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 957 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 958 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 959 . 961 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 962 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 963 DOI 10.17487/RFC5440, March 2009, 964 . 966 [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax 967 Used to Form Encoding Rules in Various Routing Protocol 968 Specifications", RFC 5511, DOI 10.17487/RFC5511, April 969 2009, . 971 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 972 Writing an IANA Considerations Section in RFCs", BCP 26, 973 RFC 8126, DOI 10.17487/RFC8126, June 2017, 974 . 976 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 977 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 978 May 2017, . 980 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 981 Computation Element Communication Protocol (PCEP) 982 Extensions for Stateful PCE", RFC 8231, 983 DOI 10.17487/RFC8231, September 2017, 984 . 986 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 987 Computation Element Communication Protocol (PCEP) 988 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 989 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 990 . 992 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 993 Decraene, B., Litkowski, S., and R. Shakir, "Segment 994 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 995 July 2018, . 997 [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. 998 Hardwick, "Conveying Path Setup Type in PCE Communication 999 Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, 1000 July 2018, . 1002 [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 1003 "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, 1004 DOI 10.17487/RFC8491, November 2018, 1005 . 1007 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 1008 and J. Hardwick, "Path Computation Element Communication 1009 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 1010 DOI 10.17487/RFC8664, December 2019, 1011 . 1013 [I-D.ietf-lsr-isis-srv6-extensions] 1014 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 1015 Z. Hu, "IS-IS Extension to Support Segment Routing over 1016 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-14 1017 (work in progress), April 2021. 1019 [I-D.ietf-spring-srv6-network-programming] 1020 Filsfils, C., Garvia, P. C., Leddy, J., Voyer, D., 1021 Matsushima, S., and Z. Li, "Segment Routing over IPv6 1022 (SRv6) Network Programming", draft-ietf-spring-srv6- 1023 network-programming-28 (work in progress), December 2020. 1025 11.2. Informative References 1027 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 1028 Element (PCE) Communication Protocol Generic 1029 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 1030 2006, . 1032 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1033 Code: The Implementation Status Section", BCP 205, 1034 RFC 7942, DOI 10.17487/RFC7942, July 2016, 1035 . 1037 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1038 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1039 Packet Routing in Networking (SPRING) Problem Statement 1040 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1041 2016, . 1043 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 1044 Stateful Path Computation Element (PCE)", RFC 8051, 1045 DOI 10.17487/RFC8051, January 2017, 1046 . 1048 [RFC8354] Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R., 1049 Ed., and M. Townsley, "Use Cases for IPv6 Source Packet 1050 Routing in Networking (SPRING)", RFC 8354, 1051 DOI 10.17487/RFC8354, March 2018, 1052 . 1054 [RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions 1055 for Segment Routing", RFC 8666, DOI 10.17487/RFC8666, 1056 December 2019, . 1058 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1059 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1060 Extensions for Segment Routing", RFC 8667, 1061 DOI 10.17487/RFC8667, December 2019, 1062 . 1064 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 1065 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1066 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 1067 . 1069 [I-D.ietf-spring-segment-routing-policy] 1070 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 1071 P. Mattes, "Segment Routing Policy Architecture", draft- 1072 ietf-spring-segment-routing-policy-11 (work in progress), 1073 April 2021. 1075 [I-D.ietf-lsr-ospfv3-srv6-extensions] 1076 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 1077 "OSPFv3 Extensions for SRv6", draft-ietf-lsr- 1078 ospfv3-srv6-extensions-02 (work in progress), February 1079 2021. 1081 [I-D.ietf-idr-bgpls-srv6-ext] 1082 Dawra, G., Filsfils, C., Talaulikar, K., Chen, M., 1083 Bernier, D., and B. Decraene, "BGP Link State Extensions 1084 for SRv6", draft-ietf-idr-bgpls-srv6-ext-07 (work in 1085 progress), March 2021. 1087 [I-D.ietf-pce-pcep-yang] 1088 Dhody, D., Hardwick, J., Beeram, V. P., and J. Tantsura, 1089 "A YANG Data Model for Path Computation Element 1090 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1091 yang-16 (work in progress), February 2021. 1093 Appendix A. Contributor 1095 The following persons contributed to this document: 1097 Dhruv Dhody 1098 Huawei Technologies 1099 Divyashree Techno Park, Whitefield 1100 Bangalore, Karnataka 560066 1101 India 1103 EMail: dhruv.ietf@gmail.com 1105 Huang Wumin 1106 Huawei Technologies 1107 Huawei Building, No. 156 Beiqing Rd. 1108 Beijing 100095 1109 China 1111 Email: huangwumin@huawei.com 1113 Shuping Peng 1114 Huawei Technologies 1115 Huawei Building, No. 156 Beiqing Rd. 1116 Beijing 100095 1117 China 1119 Email: pengshuping@huawei.com 1121 Authors' Addresses 1123 Cheng Li(Editor) 1124 Huawei Technologies 1125 Huawei Campus, No. 156 Beiqing Rd. 1126 Beijing 100095 1127 China 1129 EMail: c.l@huawei.com 1131 Mahendra Singh Negi 1132 RtBrick Inc 1133 Bangalore, Karnataka 1134 India 1136 EMail: mahend.ietf@gmail.com 1137 Siva Sivabalan 1138 Ciena Corporation 1140 EMail: msiva282@gmail.com 1142 Mike Koldychev 1143 Cisco Systems, Inc. 1144 Canada 1146 EMail: mkoldych@cisco.com 1148 Prejeeth Kaladharan 1149 RtBrick Inc 1150 Bangalore, Karnataka 1151 India 1153 EMail: prejeeth@rtbrick.com 1155 Yongqing Zhu 1156 China Telecom 1157 109 West Zhongshan Ave, Tianhe District 1158 Bangalore, Guangzhou 1159 P.R. China 1161 EMail: zhuyq8@chinatelecom.cn