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Flags is us...' == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: An SR-TE path consists of one or more SID(s) where each SID is associated with the identifier that represents the node or adjacency corresponding to the SID. This identifier is referred to as the 'Node or Adjacency Identifier' (NAI). As described later, a NAI can be represented in various formats (e.g., IPv4 address, IPv6 address, etc). Furthermore, a NAI is used only for troubleshooting purposes, and MUST not be used to replace or modify any fields in a data packet header. An SR-ERO object consists of one or more ERO subobjects described in the following section. == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: The 'L' Flag indicates whether the subobject represents a loose-hop in the explicit route [RFC3209]. If this flag is unset, a PCC MUST not overwrite the SID value present in the SR-ERO subobject. Otherwise, a PCC MAY expand or replace one or more SID value(s) in the received SR-ERO based on its local policy. -- The document date (July 12, 2013) is 3938 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-03) exists of draft-crabbe-pce-pce-initiated-lsp-01 == Outdated reference: A later version (-01) exists of draft-filsfils-rtgwg-segment-routing-00 == Outdated reference: A later version (-11) exists of draft-ietf-pce-pcep-mib-04 == Outdated reference: A later version (-21) exists of draft-ietf-pce-stateful-pce-05 == Outdated reference: A later version (-05) exists of draft-previdi-isis-segment-routing-extensions-01 == Outdated reference: A later version (-05) exists of draft-psenak-ospf-segment-routing-extensions-01 Summary: 0 errors (**), 0 flaws (~~), 13 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Sivabalan 3 Internet-Draft J. Medved 4 Intended status: Standards Track C. Filsfils 5 Expires: January 13, 2014 Cisco Systems, Inc. 6 E. Crabbe 7 Google, Inc. 8 R. Raszuk 9 NTT I3 10 July 12, 2013 12 PCEP Extensions for Segment Routing 13 draft-sivabalan-pce-segment-routing-01.txt 15 Abstract 17 Segment Routing (SR) enables any head-end node to select any path 18 without relying on a hop-by-hop signaling technique (e.g., LDP or 19 RSVP-TE). It depends only on "segments" that are advertised by Link- 20 State Interior Gateway Protocols (IGPs). A Segment Routed Path can 21 be derived from a variety of mechanisms, including an IGP Shortest 22 Path Tree (SPT), explicit configuration, or a Path Computation 23 Element (PCE). This document specifies extensions to the Path 24 Computation Element Protocol (PCEP) that allow a stateful PCE to 25 compute and instantiate Traffic Engineering paths, as well as a PCC 26 to request a path subject to certain constraint(s) and optimization 27 criteria in SR networks. 29 Requirements Language 31 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 33 document are to be interpreted as described in [RFC2119]. 35 Status of this Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at http://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on January 13, 2014. 51 Copyright Notice 53 Copyright (c) 2013 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 3. Overview of PCEP Operation in SR Networks . . . . . . . . . . 6 71 4. SR-Specific PCEP Message Extensions . . . . . . . . . . . . . 7 72 4.1. The PCReq Message . . . . . . . . . . . . . . . . . . . . 7 73 4.2. The PCRep Message . . . . . . . . . . . . . . . . . . . . 7 74 4.3. The PCInitiate Message . . . . . . . . . . . . . . . . . . 8 75 4.4. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 8 76 4.5. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 9 77 5. Object Formats . . . . . . . . . . . . . . . . . . . . . . . . 9 78 5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 9 79 5.1.1. The SR PCE Capability TLV . . . . . . . . . . . . . . 9 80 5.2. The RP Object . . . . . . . . . . . . . . . . . . . . . . 11 81 5.2.1. The LSP-PATH-TYPE TLV . . . . . . . . . . . . . . . . 11 82 5.3. The SR-ERO Object . . . . . . . . . . . . . . . . . . . . 12 83 5.3.1. The SR-ERO Subobject . . . . . . . . . . . . . . . . . 12 84 5.3.2. NAI Associated with SID . . . . . . . . . . . . . . . 14 85 5.3.3. SR-ERO Processing . . . . . . . . . . . . . . . . . . 15 86 6. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 15 87 7. Management Considerations . . . . . . . . . . . . . . . . . . 16 88 7.1. Policy . . . . . . . . . . . . . . . . . . . . . . . . . . 16 89 7.2. The PCEP Data Model . . . . . . . . . . . . . . . . . . . 16 90 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 91 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 92 9.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . 16 93 9.1.1. LSP-SIG-TYPE field in the LSP object . . . . . . . . . 16 94 9.2. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 17 95 9.3. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . . 17 96 9.3.1. LSP-PATH-TYPE Indicators . . . . . . . . . . . . . . . 17 97 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17 98 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 99 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 100 12.1. Normative References . . . . . . . . . . . . . . . . . . . 18 101 12.2. Informative References . . . . . . . . . . . . . . . . . . 19 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 104 1. Introduction 106 SR technology leverages the source routing and tunneling paradigms. 107 A source node can choose a path without relying on hop-by-hop 108 signaling protocols such as LDP or RSVP-TE. Each path is specified 109 as a set of "segments" advertised by link-state routing protocols 110 (IS-IS or OSPF). [I-D.filsfils-rtgwg-segment-routing] provides an 111 introduction to SR technology. The corresponding IS-IS and OSPF 112 extensions are specified in 113 [I-D.previdi-isis-segment-routing-extensions] and 114 [I-D.psenak-ospf-segment-routing-extensions], respectively. Two 115 types of segments have been defined; nodal and adjacency segments. A 116 nodal segment represents a path to a node, whereas an adjacency 117 segment represents a specific adjacency to a node. The SR 118 architecture can be applied to MPLS forwarding plane without any 119 change as well as IPv6 forwarding plane with a new type of routing 120 extension header. A Segment Identifier (SID) is a 32-bit value. In 121 the case of the MPLS data plane, an SR path corresponds to an MPLS 122 Label Switching Path (LSP) 124 A Segment Routed path (SR path) can be derived from an IGP Shortest 125 Path Tree (SPT). Segment Routed Traffic Engineering paths (SR-TE 126 paths) may not follow IGP SPT. Such paths may be chosen by a 127 suitable network planning tool and provisioned on the source node of 128 the SR-TE path. 130 [RFC5440] describes Path Computation Element Protocol (PCEP) for 131 communication between a Path Computation Client (PCC) and a Path 132 Control Element (PCE) or between one a pair of PCEs. A PCE computes 133 paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs) based on 134 various constraints and optimization criteria. 135 [I-D.ietf-pce-stateful-pce] specifies extensions to PCEP that allow a 136 stateful PCE to compute and recommend network paths in compliance 137 with [RFC4657] and defines objects and TLVs for MPLS-TE LSPs. 138 Stateful PCEP extensions provide synchronization of LSP state between 139 a PCC and a PCE or between a pair of PCEs, delegation of LSP control, 140 reporting of LSP state from a PCC to a PCE, controlling the setup and 141 path routing of an LSP from a PCE to a PCC. Stateful PCEP extensions 142 are intended for an operational model in which LSPs are configured on 143 the PCC, and control over them is delegated to the PCE. 145 A mechanism to dynamically instantiate LSPs on a PCC based on the 146 requests from a stateful PCE or a controller using stateful PCE is 147 specified in [I-D.crabbe-pce-pce-initiated-lsp]. Such mechanism is 148 useful in Software Driven Networks (SDN) applications, such as demand 149 engineering, or bandwidth calendaring. 151 It is possible to use a stateful PCE for computing one or more SR-TE 152 paths taking into account various constraints and objective 153 functions. Once a path is chosen, the stateful PCE can instantiate 154 an SR-TE path on the PCC using PCEP extensions specified in 155 [I-D.crabbe-pce-pce-initiated-lsp] along with the SR specific PCEP 156 extensions provided in this document. Similarly, a PCC can request 157 an SR path from either stateful or a stateless PCE. 159 2. Terminology 161 The following terminologies are used in this document: 163 ERO: Explicit Route Object 165 IGP: Interior Gateway Protocol 167 IS-IS: Intermediate System to Intermediate System 169 LSR: Label Switching Router 171 MSD: Maximum SID Depth 173 NAI: Node or Adjacency Identifier 175 OSPF: Open Shortest Path First 177 PCC: Path Computation Client 179 PCE: Path Computation Element 181 PCEP: Path Computation Element Protocol 183 RRO: Record Route Object 185 SID: Segment Identifier 187 SR: Segment Routing 189 SR-ERO: Segment Routed Explicit Route Object 191 SR Path: Segment Routed Path 193 SR-RRO: Segment Routed Record Route Object 195 SR-TE Path: Segment Routed Traffic Engineering Path 197 3. Overview of PCEP Operation in SR Networks 199 In SR networks, an ingress node of an SR path appends all outgoing 200 packets with an SR header consisting of a list of Segment IDs (SIDs). 201 The header has all necessary information to guide the packets from 202 the ingress node to the egress node of the path, and hence there is 203 no need for any signaling protocol. A SID can represent a nodal 204 segment representing a path to a node or adjacency segment 205 representing path over a specific adjacency. 207 In a PCEP session, path information is carried in the Explicit Route 208 Object (ERO), which consists of a sequence of subobjects. Various 209 types of ERO subobjects have been specified in [RFC3209], [RFC3473], 210 and [RFC3477]. In SR networks, a PCE needs to specify ERO containing 211 SIDs, and a PCC should be capable of processing such ERO. An ERO 212 containing SIDs can be included in the Path Computation LSP Initiate 213 Request message (PCInitiate) defined in 214 [I-D.crabbe-pce-pce-initiated-lsp], as well as in the Path 215 Computation LSP Update Request (PCUpd) and Path Computation LSP State 216 Report (PCRpt) messages defined in Report (PCRpt) messages defined in 217 [I-D.ietf-pce-stateful-pce]. 219 When a PCEP session between a PCC and a PCE is established, both PCEP 220 Speakers exchange information to indicate their ability to support 221 SR-specific functionality. A PCEP session can carry EROs of 222 different types. However, an ERO carrying SIDs MUST NOT include any 223 other form of EROs, i.e., all subobjects within an ERO MUST represent 224 SID. Furthermore, if an SR path is established using SR-ERO, 225 subsequent PCEP Update and Report messages for that path MUST NOT 226 contain other ERO types. This document specifies new error codes to 227 handle these errors. Should the need to change the ERO type arise, 228 the SR path must be deleted and re-created using a new ERO type. 230 A PCC MAY include an ERO object in a PCRpt message. In SR networks, 231 a PCC MAY learn the SR actual path actually taken by data packets and 232 report that path to a PCE. Methods used by a PCC to learn SR-TE 233 paths are outside the scope of this document. 235 In summary, this document: 237 o Defines a new PCEP capability, new subobjects, a new TLV, and new 238 PCEP error codes 240 o Specifies how two PCEP Speakers can establish a PCEP session that 241 can cary segment routing paths 243 o Defines the formats of SR-specific PCEP messages in Backus-Naur 244 Format (BNF). 246 This document specifies SR extensions for the stateless PCE model 247 defined in [RFC5440], as well as for the active stateful and passive 248 stateful PCE models defined in [I-D.ietf-pce-stateful-pce]. 250 4. SR-Specific PCEP Message Extensions 252 As defined in [RFC5440], a PCEP message consists of a common header 253 followed by a variable length body made up of mandatory and/or 254 optional objects. PCEP messages an their formats for stateless PCE 255 are defined in [RFC5440]. PCEP messages and their formats for 256 stateful PCE are defined in [I-D.ietf-pce-stateful-pce]. Finally, 257 PCEP messages and their formats for PCE-initiated LSP instantiation 258 are defined in [I-D.crabbe-pce-pce-initiated-lsp]. 260 This document defines changes to PCEP messages and their formats 261 required to carry SR-specific information. 263 4.1. The PCReq Message 265 This document does not specify any changes to the PCReq message 266 format. This document proposes a new optional TLV carried in the RP 267 Object (Section 5.2.1), which can be used by a PCC to request path 268 computation for one or more SR TE Paths. 270 4.2. The PCRep Message 272 This document defines the format of the PCRep message carrying SR TE 273 Paths. The message is sent by a PCE to a PCC in response to a 274 previously received PCReq message, where the PCC requested 275 computation of SR TE Paths. The format of the SR-specific PCRep 276 message is as follows: 278 ::= 279 280 Where: 282 ::=[] 284 ::= 285 [] 286 [] 288 Where: 289 ::=[] 291 The RP and NO-PATH Objects are defined in [RFC5440]. The 292 object contains the SR TE path and is defined in Section 5.3. 294 4.3. The PCInitiate Message 296 The format of the PCInitiate message is as follows: 298 ::= 299 300 Where: 302 ::= 303 [] 305 ::= 306 307 309 The object contains the SR TE path and is defined in 310 Section 5.3. The object in the Common Header MUST include the 311 SYMBOLIC-PATH-NAME TLV. 313 4.4. The PCRpt Message 315 An SR-specific PCRpt message is sent by a PCC to a PCE to report the 316 current state of an SR TE Path. A PCRpt message can carry more than 317 one LSP State Report, but all LSP State reports in the SR-Specific 318 PCRpt message MUST be for SR TE Paths. A PCC can send an LSP State 319 Report either in response to an LSP Update Request from a PCE, or 320 asynchronously when the state of an SR TE Path changes. 322 The format of the SR-specific PCRpt message is as follows: 324 ::= 325 326 Where: 328 ::= [] 330 ::= 331 332 334 Where: 335 ::= 337 The object contains the actual SR TE path used by the PCC 338 and is defined in Section 5.3. The actual SR TE Path may be 339 different from the programmed SR TE Path, for example, when the 340 programmed SR TE Path contains loose hops and the PCC must compute 341 the path between loose hops locally. 343 The and objects are defined in 344 [I-D.ietf-pce-stateful-pce]. The object MUST include the 345 SYMBOLIC-PATH-NAME TLV. The LSP-sig-type filed in the LSP object 346 MUST be set to TBD (Segment Routing). 348 4.5. The PCUpd Message 350 An SR-Specific PCUpd message is sent by a PCE to a PCC to update an 351 SR TE Path. A PCUpd message can carry more than one LSP Update 352 Request. 354 The format of the SR-specific PCUpd message is as follows: 356 ::= 357 358 Where: 360 ::= [] 362 ::= 363 364 365 Where: 366 ::= 368 The object contains the SR TE path computed by the PCE, and 369 is defined in Section 5.3. The and objects are defined 370 in [I-D.ietf-pce-stateful-pce]. The LSP object MUST include the 371 SYMBOLIC-PATH-NAME TLV. The LSP-sig-type filed in the LSP object 372 MUST be set to TBD (Segment Routing). Note that compared to the 373 RSVP-TE-specific PCUpd message defined in 374 [I-D.ietf-pce-stateful-pce], the path in the SR-specific PCUpd 375 message does not have attributes, only hops specified in the 376 object. 378 5. Object Formats 380 5.1. The OPEN Object 382 This document defines a new optional TLV for use in the OPEN Object. 384 5.1.1. The SR PCE Capability TLV 386 The SR-PCE-CAPABILITY TLV is an optional TLV for use in the OPEN 387 Object to negotiate Segment Routing capability on the PCEP session. 388 The format of the SR-PCE-CAPABILITY TLV is shown in the following 389 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 | Type=TBD | Length=4 | 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | Reserved | Flags | MSD | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 Figure 1: SR-PCE-CAPABILITY TLV format 401 The code point for the TLV type is to be defined by IANA. The TLV 402 length is 4 octets. 404 The 32-bit value is formatted as follows. The "Maximum SID Depth" (1 405 octet) field (MSD) specifies the maximum number of SIDs that a PCC is 406 capable of imposing on a packet. The "Flags" (1 octet) and 407 "Reserved" (2 octets) fields are currently unused, and MUST be set to 408 zero and ignored on receipt. 410 5.1.1.1. Negotiating SR Capability 412 The SR capability TLV is contained in the OPEN object. By including 413 the TLV in the OPEN message to a PCE, a PCC indicates its support for 414 SR-TE Paths. By including the TLV in the OPEN message to a PCC, a 415 PCE indicates that it is capable of computing SR-TE paths. 417 The number of SIDs that can be imposed on a packet depends on PCC's 418 data plane's capability. The default value of MSD is 0 meaning that 419 a PCC does not impose any limitation on the number of SIDs included 420 in any SR-TE path coming from PCE. Once an SR-capable PCEP session 421 is established with a non-default MSD value, the corresponding PCE 422 cannot send SR-TE paths with SIDs exceeding the MSD value. If a PCC 423 needs to modify the MSD value, the PCEP session must be closed and 424 re-established with the new MSD value. If a PCEP session is 425 established with a non-default MSD value, and the PCC receives an 426 SR-TE path containing more SIDs than specified in the MSD value, the 427 PCC MUST send out a PCErr message with Error-Type 10 (Reception of an 428 invalid object) and Error-value 3 (Unsupported number of Segment 429 ERO). 431 The SR Capability TLV is meaningful only in the OPEN message sent 432 from a PCC to a PCE. As such, a PCE does not need to set MSD value 433 in outbound message to a PCC. Similarly, an MSD value received by a 434 PCC is ignored. If there are multiple SR capability TLVs, only the 435 first TLV is processed. 437 All bits in the Reserved and Flags fields SHOULD be set to 0 on 438 outbound OPEN messages, and MUST be ignored on inbound OPEN messages. 440 5.2. The RP Object 442 This document defines a new optional TLV for use in the RP Object. 444 5.2.1. The LSP-PATH-TYPE TLV 446 A PCC can simultaneously support both RSVP-TE signaled MPLS LSPs as 447 well as SR-TE paths. In this case, the PCC needs to query and 448 receive paths specified with RSVP-TE EROs (defined in [RFC5440]) and 449 paths specified with SR-EROs (defined in this document). Thus, there 450 is a need for a PCC to identify the ERO type that it wishes to 451 receive from a PCE. 453 This document defines a new optional TLV called "LSP-PATH-TYPE" that 454 MAY be included in the RP object (defined in [RFC5440]) on a PCReq 455 message from a PCC to a PCE. The format of this TLV is shown in the 456 following figure: 458 0 1 2 3 459 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 1 460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 461 | Type= TBD | Length=1 | 462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 463 | LSP-Path-Type | 464 +-+-+-+-+-+-+-+-+ 466 Figure 2: LSP-PATH-TYPE TLV format 468 The type of the TLV is to be defined by IANA. The TLV length is 1 469 octets. 471 The 8-bit value contains the Path-Type (PT). The following values 472 for Path Type are defined: 474 o PT = 0: Requested path is to be used with RSVP-TE signaling 475 (default). 477 o PT = 1: SR-TE path is requested. 479 If this TLV is not included in the PCReq message, the default Path 480 Type of 0 is assumed, otherwise the path type specified in the TLV is 481 used. An RP object SHOULD carry no more than one LSP-PATH-TYPE TLV, 482 only the first is used if several are present, the others are 483 ignored. 485 5.3. The SR-ERO Object 487 An SR-TE path consists of one or more SID(s) where each SID is 488 associated with the identifier that represents the node or adjacency 489 corresponding to the SID. This identifier is referred to as the 490 'Node or Adjacency Identifier' (NAI). As described later, a NAI can 491 be represented in various formats (e.g., IPv4 address, IPv6 address, 492 etc). Furthermore, a NAI is used only for troubleshooting purposes, 493 and MUST not be used to replace or modify any fields in a data packet 494 header. An SR-ERO object consists of one or more ERO subobjects 495 described in the following section. 497 5.3.1. The SR-ERO Subobject 499 An SR-ERO subobject consists of a 32-bit header followed by the SID 500 and the NAI associated with the SID. The SID is a 32-bit number. 501 The size of the NAI depends on its respective type, as described in 502 the following sections. 504 0 1 2 3 505 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 1 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 |L| Type | Length | ST | Flags |F|S|C|M| 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 | SID | 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 // NAI (variable) // 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 Figure 3: SR-ERO Subobject format 516 The fields in the ERO Subobject are as follows: 518 The 'L' Flag indicates whether the subobject represents a loose-hop 519 in the explicit route [RFC3209]. If this flag is unset, a PCC 520 MUST not overwrite the SID value present in the SR-ERO subobject. 521 Otherwise, a PCC MAY expand or replace one or more SID value(s) in 522 the received SR-ERO based on its local policy. 524 Type is the type of the SR-ERO Subobject. This document defines the 525 SR-ERO Subobject type. A new code point will be requested for the 526 SR-ERO Subobject from IANA. 528 Length contains the total length of the subobject in octets, 529 including the L, Type and Length fields. Length MUST be at least 530 4, and MUST be a multiple of 4. 532 SID Type (ST) indicates the type of information associated with the 533 SID contained in the object body. The SID-Type values are 534 described later in this document. 536 Flags is used to carry any additional information pertaining to SID. 537 Currently, the following flag bits are defined: 539 * M: When this bit is set, the SID value represents an MPLS label 540 stack entry as specified in [RFC5462] where only the label 541 value is specified by the PCE. Other fields (TC, S, and TTL) 542 fields MUST be considered invalid, and PCC MUST set these 543 fields according to its local policy and MPLS forwarding rules. 545 * C: When this bit as well as the M bit are set, then the SID 546 value represents an MPLS label stack entry as specified in 547 [RFC5462], where all the entry's fields (Label, TC, S, and TTL) 548 are specified by the PCE. However, a PCC MAY choose to 549 override TC, S, and TTL values according its local policy and 550 MPLS forwarding rules. 552 * S: When this bit is set, the SID value in the subobject body is 553 null. In this case, the PCC is responsible for choosing the 554 SID value, e.g., by looking up its Traffic Engineering Database 555 (TED) using node/adjacency identifier in the subobject body. 557 * F: When this bit is set, the NAI value in the subobject body is 558 null. 560 SID is the Segment Identifier. 562 NAI contains the NAI associated with the SID. Depending on the 563 value of ST, the NAI can have different format as described in the 564 following section. 566 5.3.2. NAI Associated with SID 568 This document defines the following NAIs: 570 'IPv4 Node ID' is specified as an IPv4 address. In this case, ST 571 and Length are 1 and 12 respectively. 573 'IPv6 Node ID' is specified as an IPv6 address. In this case, ST 574 and Length are 2 and 24 respectively. 576 'IPv4 Adjacency' is specified as a pair of IPv4 addresses. In this 577 case, ST and Length are 3 and 16, respectively, and the format of 578 the NAI is shown in the following figure: 580 0 1 2 3 581 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 1 582 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 583 | Local IPv4 address | 584 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 585 | Remote IPv4 address | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 Figure 4: NAI for IPv4 Adjacency 590 'IPv6 Adjacency' is specified as a pair of IPv6 addresses. In this 591 case, ST and Length are 4 and 40 respectively, and the format of 592 the NAI is shown in the following figure: 594 0 1 2 3 595 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 1 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 // Local IPv6 address (16 bytes) // 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 // Remote IPv6 address (16 bytes) // 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 Figure 5: NAI for IPv6 adjacency 604 'Unnumbered Adjacency with IPv4 NodeIDs' is specified as a pair of 605 Node ID / Interface ID tuples. In this case, ST and Length are 5 606 and 24 respectively, and the format of the NAI is shown in the 607 following figure: 609 0 1 2 3 610 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 1 611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 | Local Node-ID | 613 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 614 | Local Interface ID | 615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 | Remote Node-ID | 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 | Remote Interface ID | 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 Figure 6: NAI for Unnumbered adjacency with IPv4 Node IDs 623 We are yet to decide if another SID subobject is required for 624 unnumbered adjacency with 128 bit node ID. 626 5.3.3. SR-ERO Processing 628 A PCEP Speaker that does not recognize the new ERO subobject in the 629 PCCreate, PCUpd or PCRpt message MUST reject the entire PCEP message 630 and MUST send a PCE error message with Error-Type=3 ("Unknown 631 Object") and Error-Value=2 ("Unrecognized object Type") or Error- 632 Type=4 ("Not supported object") and Error-Value=2 ("Not supported 633 object Type"), defined in [RFC5440]. 635 When the SID represents an MPLS label (i.e. the M bit is set), its 636 value (20 most significant bits) MUST be larger than 15, unless it is 637 special purpose label, such as an Entropy Label Indicator (ELI) or an 638 Entropy Label (EL). If a PCEP Speaker receives a label ERO subobject 639 with an invalid value, it MUST send the PCE error message with Error- 640 Type = "Reception of an invalid object" and Error-Value = "Bad label 641 value". If both M and C bits of an ERO subobject are set, and if a 642 PCEP Speaker finds erroneous setting in one or more of TC, S, and TTL 643 fields, it MUST send a PCE error with Error-Type = "Reception of an 644 invalid object" and Error-Value = "Bad label format". 646 If a PCC receives a stack of SR-ERO subobjects, and the number of 647 stack exceeds the maximum number of SIDs that the PCC can impose on 648 the packet, it MAY send a PCE error with Error-Type = "Reception of 649 an invalid object" and Error-Value = "Unsupported number of Segment 650 ERO subobjects". 652 6. Backward Compatibility 654 An LSR that does not support the SR PCEP capability negotiation 655 cannot recognize the SR-ERO subobjects. As such, it shall send a 656 PCEP error with Error-Type = 4 (Not supported object) and Error-Value 657 = 2 (Not supported object Type) as per [RFC5440]. 659 7. Management Considerations 661 7.1. Policy 663 PCEP implementation: 665 o Can enable SR-PCEP capability either by default or via explicit 666 configuration. 668 o May generate PCEP error due to unsupported number of SR-ERO 669 subobjects either by default or via explicit configuration. 671 7.2. The PCEP Data Model 673 A PCEP MIB module is defined in [I-D.ietf-pce-pcep-mib] needs be 674 extended to cover additional functionality provided by [RFC5440] and 675 [I-D.crabbe-pce-pce-initiated-lsp]. Such extension will cover the 676 new functionality specified in this document. 678 8. Security Considerations 680 The security considerations described in [RFC5440] and 681 [I-D.crabbe-pce-pce-initiated-lsp] are applicable to this 682 specification. No additional security measure is required. 684 9. IANA Considerations 686 9.1. PCEP Objects 688 IANA is requested to allocate a ERO subobject type (recommended value 689 = 5) for the SR-ERO subobject. 691 9.1.1. LSP-SIG-TYPE field in the LSP object 693 This document requests that a new value is allocated for Segment 694 Routing LSP Type in the LSP-SIG_TYPE registry. 696 Value Meaning 697 1 Segment Routing 699 9.2. PCEP-Error Object 701 This document defines new Error-Type and Error-Value for the 702 following new conditions: 704 Error-Type Meaning 705 10 Reception of an invalid object 706 Error-value=2: Bad label value 707 Error-value=3: Unsupported number of Segment ERO 708 subobjects 710 9.3. PCEP TLV Type Indicators 712 This document defines the following new PCEP TLVs: 714 Value Meaning Reference 715 -------- ------------------------------------ ----------------- 716 26 SR-PCE-CAPABILITY This document 717 27 LSP-PATH-TYPE This document 719 9.3.1. LSP-PATH-TYPE Indicators 721 This document requests that a registry is created to manage the value 722 of the LSP-Path-Type field in the LSP object, which defines the 723 technology of the LSP path. 725 Value Meaning 726 0 RSVP 727 1 Segment Routing 729 10. Contributors 731 The following people contributed to this document: 732 - Lakshmi Sharma (Cisco Systems) 734 11. Acknowledgements 736 We'd like to thank Ina Minei and George Swallow for valuable 737 comments. 739 12. References 740 12.1. Normative References 742 [I-D.crabbe-pce-pce-initiated-lsp] 743 Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 744 Extensions for PCE-initiated LSP Setup in a Stateful PCE 745 Model", draft-crabbe-pce-pce-initiated-lsp-01 (work in 746 progress), April 2013. 748 [I-D.filsfils-rtgwg-segment-routing] 749 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 750 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 751 Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, 752 "Segment Routing Architecture", 753 draft-filsfils-rtgwg-segment-routing-00 (work in 754 progress), June 2013. 756 [I-D.ietf-pce-pcep-mib] 757 Koushik, K., Stephan, E., Zhao, Q., King, D., and J. 758 Hardwick, "PCE communication protocol (PCEP) Management 759 Information Base", draft-ietf-pce-pcep-mib-04 (work in 760 progress), February 2013. 762 [I-D.ietf-pce-stateful-pce] 763 Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP 764 Extensions for Stateful PCE", 765 draft-ietf-pce-stateful-pce-05 (work in progress), 766 July 2013. 768 [I-D.previdi-isis-segment-routing-extensions] 769 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 770 Decraene, B., Litkowski, S., Geib, R., Milojevic, I., 771 Shakir, R., Ytti, S., Henderickx, W., and J. Tantsura, 772 "IS-IS Extensions for Segment Routing", 773 draft-previdi-isis-segment-routing-extensions-01 (work in 774 progress), July 2013. 776 [I-D.psenak-ospf-segment-routing-extensions] 777 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., and R. 778 Shakir, "OSPF Extensions for Segment Routing", 779 draft-psenak-ospf-segment-routing-extensions-01 (work in 780 progress), July 2013. 782 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 783 Requirement Levels", BCP 14, RFC 2119, March 1997. 785 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 786 (PCE) Communication Protocol (PCEP)", RFC 5440, 787 March 2009. 789 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 790 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 791 Class" Field", RFC 5462, February 2009. 793 12.2. Informative References 795 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 796 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 797 Tunnels", RFC 3209, December 2001. 799 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 800 (GMPLS) Signaling Resource ReserVation Protocol-Traffic 801 Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. 803 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 804 in Resource ReSerVation Protocol - Traffic Engineering 805 (RSVP-TE)", RFC 3477, January 2003. 807 [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) 808 Communication Protocol Generic Requirements", RFC 4657, 809 September 2006. 811 Authors' Addresses 813 Siva Sivabalan 814 Cisco Systems, Inc. 815 2000 Innovation Drive 816 Kanata, Ontario K2K 3E8 817 Canada 819 Email: msiva@cisco.com 821 Jan Medved 822 Cisco Systems, Inc. 823 170 West Tasman Dr. 824 San Jose, CA 95134 825 US 827 Email: jmedved@cisco.com 828 Clarence Filsfils 829 Cisco Systems, Inc. 830 Pegasus Parc 831 De kleetlaan 6a, DIEGEM BRABANT 1831 832 BELGIUM 834 Email: cfilsfil@cisco.com 836 Edward Crabbe 837 Google, Inc. 838 1600 Amphitheatre Parkway 839 Mountain View, CA 94043 840 US 842 Email: edward.crabbe@gmail.com 844 Robert Raszuk 845 NTT I3 846 101 S. Ellsworth Ave 847 San Mateo, CA 94401 848 US 850 Email: robert@raszuk.net