idnits 2.17.00 (12 Aug 2021) /tmp/idnits46911/draft-ietf-pce-segment-routing-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 432 has weird spacing: '...L' Flag indic...' == Line 438 has weird spacing: '... Type is th...' == Line 441 has weird spacing: '... Length conta...' == Line 454 has weird spacing: '... 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: As defined in [RFC5440], a PCEP message consists of a common header followed by a variable length body made up of mandatory and/or optional objects. This document does not require any changes in the format of PCReq and PCRep messages specified in [RFC5440], PCInitiate message specified in [I-D.ietf-pce-pce-initiated-lsp], and PCRpt and PCUpd messages specified in [I-D.ietf-pce-stateful-pce]. However, PCEP messages pertaining to SR-TE LSP MUST include PATH-SETUP-TYPE TLV in the RP or SRP object to clearly identify that SR-TE LSP is intended. In other words, a PCEP speaker MUST not infer whether or not a PCEP message pertains to SR-TE LSP from any other object or TLV. == 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 LSP [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 (October 4, 2016) is 2055 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: draft-ietf-isis-segment-routing-extensions has been published as RFC 8667 == Outdated reference: draft-ietf-ospf-segment-routing-extensions has been published as RFC 8665 == Outdated reference: draft-ietf-pce-lsp-setup-type has been published as RFC 8408 == Outdated reference: draft-ietf-pce-pce-initiated-lsp has been published as RFC 8281 == Outdated reference: draft-ietf-pce-pcep-mib has been published as RFC 7420 == Outdated reference: draft-ietf-pce-stateful-pce has been published as RFC 8231 == Outdated reference: A later version (-05) exists of draft-tantsura-idr-bgp-ls-segment-routing-msd-01 == Outdated reference: A later version (-02) exists of draft-tantsura-isis-segment-routing-msd-01 Summary: 0 errors (**), 0 flaws (~~), 15 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: April 7, 2017 Cisco Systems, Inc. 6 E. Crabbe 7 Oracle 8 R. Raszuk 9 Mirantis Inc. 10 V. Lopez 11 Telefonica I+D 12 J. Tantsura 13 Individual 14 W. Henderickx 15 Nokia 16 J. Hardwick 17 Metaswitch Networks 18 October 4, 2016 20 PCEP Extensions for Segment Routing 21 draft-ietf-pce-segment-routing-08 23 Abstract 25 Segment Routing (SR) enables any head-end node to select any path 26 without relying on a hop-by-hop signaling technique (e.g., LDP or 27 RSVP-TE). It depends only on "segments" that are advertised by Link- 28 State Interior Gateway Protocols (IGPs). A Segment Routed Path can 29 be derived from a variety of mechanisms, including an IGP Shortest 30 Path Tree (SPT), explicit configuration, or a Path Computation 31 Element (PCE). This document specifies extensions to the Path 32 Computation Element Protocol (PCEP) that allow a stateful PCE to 33 compute and initiate Traffic Engineering (TE) paths, as well as a PCC 34 to request a path subject to certain constraint(s) and optimization 35 criteria in SR networks. 37 Requirements Language 39 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 40 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 41 document are to be interpreted as described in [RFC2119]. 43 Status of This Memo 45 This Internet-Draft is submitted in full conformance with the 46 provisions of BCP 78 and BCP 79. 48 Internet-Drafts are working documents of the Internet Engineering 49 Task Force (IETF). Note that other groups may also distribute 50 working documents as Internet-Drafts. The list of current Internet- 51 Drafts is at http://datatracker.ietf.org/drafts/current/. 53 Internet-Drafts are draft documents valid for a maximum of six months 54 and may be updated, replaced, or obsoleted by other documents at any 55 time. It is inappropriate to use Internet-Drafts as reference 56 material or to cite them other than as "work in progress." 58 This Internet-Draft will expire on April 7, 2017. 60 Copyright Notice 62 Copyright (c) 2016 IETF Trust and the persons identified as the 63 document authors. All rights reserved. 65 This document is subject to BCP 78 and the IETF Trust's Legal 66 Provisions Relating to IETF Documents 67 (http://trustee.ietf.org/license-info) in effect on the date of 68 publication of this document. Please review these documents 69 carefully, as they describe your rights and restrictions with respect 70 to this document. Code Components extracted from this document must 71 include Simplified BSD License text as described in Section 4.e of 72 the Trust Legal Provisions and are provided without warranty as 73 described in the Simplified BSD License. 75 Table of Contents 77 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 78 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 79 3. Overview of PCEP Operation in SR Networks . . . . . . . . . . 5 80 4. SR-Specific PCEP Message Extensions . . . . . . . . . . . . . 7 81 5. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 7 82 5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 7 83 5.1.1. The SR PCE Capability TLV . . . . . . . . . . . . . . 7 84 5.2. The RP/SRP Object . . . . . . . . . . . . . . . . . . . . 9 85 5.3. ERO Object . . . . . . . . . . . . . . . . . . . . . . . 9 86 5.3.1. SR-ERO Subobject . . . . . . . . . . . . . . . . . . 9 87 5.3.2. NAI Associated with SID . . . . . . . . . . . . . . . 11 88 5.3.3. ERO Processing . . . . . . . . . . . . . . . . . . . 13 89 5.4. RRO Object . . . . . . . . . . . . . . . . . . . . . . . 14 90 5.4.1. RRO Processing . . . . . . . . . . . . . . . . . . . 14 91 5.5. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 15 92 6. Backward Compatibility . . . . . . . . . . . . . . . . . . . 15 93 7. Management Considerations . . . . . . . . . . . . . . . . . . 15 94 7.1. Policy . . . . . . . . . . . . . . . . . . . . . . . . . 15 95 7.2. The PCEP Data Model . . . . . . . . . . . . . . . . . . . 16 97 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 98 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 99 9.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 16 100 9.2. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 16 101 9.3. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 17 102 9.4. New Path Setup Type . . . . . . . . . . . . . . . . . . . 17 103 9.5. New Metric Type . . . . . . . . . . . . . . . . . . . . . 17 104 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 105 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 106 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 107 12.1. Normative References . . . . . . . . . . . . . . . . . . 18 108 12.2. Informative References . . . . . . . . . . . . . . . . . 19 109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 111 1. Introduction 113 SR technology leverages the source routing and tunneling paradigms. 114 A source node can choose a path without relying on hop-by-hop 115 signaling protocols such as LDP or RSVP-TE. Each path is specified 116 as a set of "segments" advertised by link-state routing protocols 117 (IS-IS or OSPF). [I-D.filsfils-rtgwg-segment-routing] provides an 118 introduction to SR architecture. The corresponding IS-IS and OSPF 119 extensions are specified in 120 [I-D.ietf-isis-segment-routing-extensions] and 121 [I-D.ietf-ospf-segment-routing-extensions], respectively. SR 122 architecture defines a "segment" as a piece of information advertised 123 by a link-state routing protocols, e.g. an IGP prefix or an IGP 124 adjacency. Several types of segments are defined. A Node segment 125 represents an ECMP-aware shortest-path computed by IGP to a specific 126 node, and is always global within SR/IGP domain. An Adjacency 127 Segment represents unidirectional adjacency. An Adjacency Segment is 128 local to the node which advertises it. Both Node segments and 129 Adjacency segments can be used for SR Traffic Engineering (SR-TE). 131 The SR architecture can be applied to the MPLS forwarding plane 132 without any change, in which case an SR path corresponds to an MPLS 133 Label Switching Path (LSP). This document is relevant to MPLS 134 forwarding plane only and assumes that a 32-bit Segment Identifier 135 (SID) represents an absolute value of MPLS label entry. In this 136 document, "Node-SID" and "Adjacency-SID" denote Node Segment 137 Identifier and Adjacency Segment Identifier respectively. 139 A Segment Routed path (SR path) can be derived from an IGP Shortest 140 Path Tree (SPT). SR-TE paths may not follow IGP SPT. Such paths may 141 be chosen by a suitable network planning tool and provisioned on the 142 ingress node of the SR-TE path. 144 [RFC5440] describes Path Computation Element Protocol (PCEP) for 145 communication between a Path Computation Client (PCC) and a Path 146 Computation Element (PCE) or between one a pair of PCEs. A PCE or a 147 PCC operating as a PCE (in hierarchical PCE environment) computes 148 paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs) based on 149 various constraints and optimization criteria. 150 [I-D.ietf-pce-stateful-pce] specifies extensions to PCEP that allow a 151 stateful PCE to compute and recommend network paths in compliance 152 with [RFC4657] and defines objects and TLVs for MPLS-TE LSPs. 153 Stateful PCEP extensions provide synchronization of LSP state between 154 a PCC and a PCE or between a pair of PCEs, delegation of LSP control, 155 reporting of LSP state from a PCC to a PCE, controlling the setup and 156 path routing of an LSP from a PCE to a PCC. Stateful PCEP extensions 157 are intended for an operational model in which LSPs are configured on 158 the PCC, and control over them is delegated to the PCE. 160 A mechanism to dynamically initiate LSPs on a PCC based on the 161 requests from a stateful PCE or a controller using stateful PCE is 162 specified in [I-D.ietf-pce-pce-initiated-lsp]. Such mechanism is 163 useful in Software Driven Networks (SDN) applications, such as on 164 demand engineering, or bandwidth calendaring. 166 It is possible to use a stateful PCE for computing one or more SR-TE 167 paths taking into account various constraints and objective 168 functions. Once a path is chosen, the stateful PCE can initiate an 169 SR-TE path on a PCC using PCEP extensions specified in 170 [I-D.ietf-pce-pce-initiated-lsp] using the SR specific PCEP 171 extensions specified in this document. Additionally, using 172 procedures described in this document, a PCC can request an SR path 173 from either stateful or a stateless PCE. This specification relies 174 on the PATH-SETUP-TYPE TLV and procedures specified in 175 [I-D.ietf-pce-lsp-setup-type]. 177 2. Terminology 179 The following terminologies are used in this document: 181 ERO: Explicit Route Object 183 IGP: Interior Gateway Protocol 185 IS-IS: Intermediate System to Intermediate System 187 LSR: Label Switching Router 189 MSD: Maximum SID Depth 191 NAI: Node or Adjacency Identifier 192 OSPF: Open Shortest Path First 194 PCC: Path Computation Client 196 PCE: Path Computation Element 198 PCEP: Path Computation Element Protocol 200 RRO: Record Route Object 202 SID: Segment Identifier 204 SR: Segment Routing 206 SR-TE: Segment Routed Traffic Engineering 208 TED: Traffic Engineering Database 210 3. Overview of PCEP Operation in SR Networks 212 In SR networks, an ingress node of an SR path appends all outgoing 213 packets with an SR header consisting of a list of SIDs (or MPLS 214 labels in the context of this document). The header has all 215 necessary information to guide the packets from the ingress node to 216 the egress node of the path, and hence there is no need for any 217 signaling protocol. 219 In a PCEP session, LSP information is carried in the Explicit Route 220 Object (ERO), which consists of a sequence of subobjects. Various 221 types of ERO subobjects have been specified in [RFC3209], [RFC3473], 222 and [RFC3477]. In SR networks, an ingress node of an SR path appends 223 all outgoing packets with an SR header consisting of a list of SIDs 224 (or MPLS labels in the context of this document). SR-TE LSPs 225 computed by a PCE can be represented in one of the following forms: 227 o An ordered set of IP address(es) representing network nodes/links: 228 In this case, the PCC needs to convert the IP address(es) into the 229 corresponding MPLS labels by consulting its Traffic Engineering 230 Database (TED). 232 o An ordered set of SID(s). 234 o An ordered set of both MPLS label(s) and IP address(es): In this 235 case, the PCC needs to convert the IP address(es) into the 236 corresponding SID(s) by consulting its TED. 238 This document defines a new ERO subobject denoted by "SR-ERO 239 subobject" capable of carrying a SID as well as the identity of the 240 node/adjacency represented by the SID. SR-capable PCEP speakers 241 should be able to generate and/or process such ERO subobject. An ERO 242 containing SR-ERO subobjects can be included in the PCEP Path 243 Computation Reply (PCRep) message defined in [RFC5440], the PCEP LSP 244 Initiate Request message (PCInitiate) defined in 245 [I-D.ietf-pce-pce-initiated-lsp], as well as in the PCEP LSP Update 246 Request (PCUpd) and PCEP LSP State Report (PCRpt) messages defined in 247 defined in [I-D.ietf-pce-stateful-pce]. 249 When a PCEP session between a PCC and a PCE is established, both PCEP 250 speakers exchange their capabilites to indicate their ability to 251 support SR-specific functionality. Furthermore, an LSP initially 252 established via RSVP-TE signaling can be updated with SR-TE path. 253 This capability is useful when a network is migrated from RSVP-TE to 254 SR-TE technology. Similarly, an LSP initially created with SR-TE 255 signaling can be updated using RSVP-TE if necessary. 257 A PCC MAY include an RRO object containing the recorded LSP in PCReq 258 and PCRpt messages as specified in [RFC5440] and 259 [I-D.ietf-pce-stateful-pce] respectively. This document defines a 260 new RRO subobject for SR networks. Methods used by a PCC to record 261 SR-TE LSP are outside the scope of this document. 263 In summary, this document: 265 o Defines a new PCEP capability, new ERO subobject, new RRO 266 subobject, a new TLV, and new PCEP error codes. 268 o Specifies how two PCEP speakers can establish a PCEP session that 269 can carry information about SR-TE paths. 271 o Specifies processing rules of ERO subobject. 273 o Defines a new path setup type carried in the PATH-SETUP-TYPE TLV 274 for SR-TE LSP. 276 The extensions specified in this document complement the existing 277 PCEP specifications to support SR-TE path. As such, the PCEP 278 messages (e.g., Path Computation Request, Path Computation Reply, 279 Path Computation Report, Path Computation Update, Path Computation 280 Initiate, etc.,) MUST be formatted according to [RFC5440], 281 [I-D.ietf-pce-stateful-pce], [I-D.ietf-pce-pce-initiated-lsp], and 282 any other applicable PCEP specifications. 284 4. SR-Specific PCEP Message Extensions 286 As defined in [RFC5440], a PCEP message consists of a common header 287 followed by a variable length body made up of mandatory and/or 288 optional objects. This document does not require any changes in the 289 format of PCReq and PCRep messages specified in [RFC5440], PCInitiate 290 message specified in [I-D.ietf-pce-pce-initiated-lsp], and PCRpt and 291 PCUpd messages specified in [I-D.ietf-pce-stateful-pce]. However, 292 PCEP messages pertaining to SR-TE LSP MUST include PATH-SETUP-TYPE 293 TLV in the RP or SRP object to clearly identify that SR-TE LSP is 294 intended. In other words, a PCEP speaker MUST not infer whether or 295 not a PCEP message pertains to SR-TE LSP from any other object or 296 TLV. 298 5. Object Formats 300 5.1. The OPEN Object 302 This document defines a new optional TLV for use in the OPEN Object. 304 5.1.1. The SR PCE Capability TLV 306 The SR-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN 307 Object to exchange SR capability of PCEP speakers. The format of the 308 SR-PCE-CAPABILITY TLV is shown in the following figure: 310 0 1 2 3 311 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 1 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | Type=TBD | Length=4 | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 | Reserved | Flags |L| MSD | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 Figure 1: SR-PCE-CAPABILITY TLV format 320 The code point for the TLV type is to be defined by IANA. The TLV 321 length is 4 octets. 323 The 32-bit value is formatted as follows. The "Maximum SID Depth" (1 324 octet) field (MSD) specifies the maximum number of SIDs (MPLS label 325 stack depth in context of this document) that a PCC is capable of 326 imposing on a packet. The "Reserved" (2 octets) field is unused, and 327 MUST be set to zero on transmission and ignored on reception. The 328 "Flags" field is 1 octect long, and this document defines the 329 following flag: 331 o L-flag: A PCC sets this flag to 1 to indicate that it does not 332 impose any limit on MSD. 334 5.1.1.1. Exchanging SR Capability 336 By including the SR-PCE-CAPABILITY TLV in the OPEN message destined 337 to a PCE, a PCC indicates that it is capable of supporting the head- 338 end functions for SR-TE LSP. By including the TLV in the OPEN 339 message destined to a PCC, a PCE indicates that it is capable of 340 computing SR-TE paths. 342 The number of SIDs that can be imposed on a packet depends on PCC's 343 data plane's capability. An MSD value MUST be non-zero otherwise the 344 receiver of the SR-PCE-CAPABILITY TLV MUST assume that the sender is 345 not capable of imposing a MSD of any depth and hence is not SR-TE 346 capable. 348 Note that the MSD value exchanged via SR-PCE-CAPABILITY TLV indicates 349 the SID/label imposition limit for the PCC node. However, if a PCE 350 learns MSD value of a PCC node via different means, e.g routing 351 protocols, as specified in: [I-D.tantsura-isis-segment-routing-msd]; 352 [I-D.tantsura-ospf-segment-routing-msd]; 353 [I-D.tantsura-idr-bgp-ls-segment-routing-msd], then it ignores the 354 MSD value in the SR-PCE-CAPABILITY TLV. Furthermore, whenever a PCE 355 learns MSD for a link via different means, it MUST use that value for 356 that link regardless of the MSD value exchanged via SR-PCE-CAPABILITY 357 TLV. 359 Once an SR-capable PCEP session is established with a non-zero MSD 360 value, the corresponding PCE MUST NOT send SR-TE paths with number of 361 SIDs exceeding that MSD value. If a PCC needs to modify the MSD 362 value, the PCEP session MUST be closed and re-established with the 363 new MSD value. If a PCEP session is established with a non-zero MSD 364 value, and the PCC receives an SR-TE path containing more SIDs than 365 specified in the MSD value, the PCC MUST send a PCErr message with 366 Error-Type 10 (Reception of an invalid object) and Error-Value 3 367 (Unsupported number of Segment ERO). If a PCEP session is 368 established with an MSD value of zero, then the PCC MAY specify an 369 MSD for each path computation request that it sends to the PCE. 371 The SR Capability TLV is meaningful only in the OPEN message sent 372 from a PCC to a PCE. As such, a PCE does not need to set MSD value 373 in outbound message to a PCC. Similarly, a PCC ignores any MSD value 374 received from a PCE. If a PCE receives multiple SR-PCE-CAPABILITY 375 TLVs in an OPEN message, it processes only the first TLV received. 377 5.2. The RP/SRP Object 379 In order to setup an SR-TE LSP using SR, RP or SRP object MUST PATH- 380 SETUP-TYPE TLV specified in [I-D.ietf-pce-lsp-setup-type]. This 381 document defines a new Path Setup Type (PST) for SR as follows: 383 o PST = 1: Path is setup using Segment Routing Traffic Engineering 384 technique. 386 5.3. ERO Object 388 An SR-TE path consists of one or more SID(s) where each SID MAY be 389 associated with the identifier that represents the node or adjacency 390 corresponding to the SID. This identifier is referred to as the 391 'Node or Adjacency Identifier' (NAI). As described later, a NAI can 392 be represented in various formats (e.g., IPv4 address, IPv6 address, 393 etc). Furthermore, a NAI is used for troubleshooting purposes and, 394 if necessary, to derive SID value as described below. 396 The ERO object specified in [RFC5440] is used to carry SR-TE path 397 information. In order to carry SID and/or NAI, this document defines 398 a new ERO subobject referred to as "SR-ERO subobject" whose format is 399 specified in the following section. An ERO object carrying an SR-TE 400 path consists of one or more ERO subobject(s), and MUST carry only 401 SR-ERO subobject. Note that an SR-ERO subobject does not need to 402 have both SID and NAI. However, at least one of them MUST be 403 present. 405 When building the MPLS label stack from ERO, a PCC MUST assume that 406 SR-ERO subobjects are organized as a last-in-first-out stack. The 407 first subobject relative to the beginning of ERO contains the 408 information about the topmost label. The last subobject contains 409 information about the bottommost label. 411 5.3.1. SR-ERO Subobject 413 An SR-ERO subobject consists of a 32-bit header followed by the SID 414 and the NAI associated with the SID. The SID is a 32-bit number. 415 The size of the NAI depends on its respective type, as described in 416 the following sections. 418 0 1 2 3 419 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 1 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 |L| Type | Length | ST | Flags |F|S|C|M| 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | SID | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 // NAI (variable) // 426 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 Figure 2: SR-ERO Subobject format 430 The fields in the SR-ERO Subobject are as follows: 432 The 'L' Flag indicates whether the subobject represents a loose-hop 433 in the LSP [RFC3209]. If this flag is unset, a PCC MUST not 434 overwrite the SID value present in the SR-ERO subobject. 435 Otherwise, a PCC MAY expand or replace one or more SID value(s) in 436 the received SR-ERO based on its local policy. 438 Type is the type of the SR-ERO subobject. This document defines the 439 SR-ERO subobject type, and requests a new codepoint from IANA. 441 Length contains the total length of the subobject in octets, 442 including the L, Type and Length fields. Length MUST be at least 443 8, and MUST be a multiple of 4. As mentioned earlier, an SR-ERO 444 subobject MUST have at least SID or NAI. The length should take 445 into consideration SID or NAI only if they are not null. The 446 flags described below used to indicate whether SID or NAI field is 447 null. 449 SID Type (ST) indicates the type of information associated with the 450 SID contained in the object body. When ST value is 0, SID MUST 451 NOT be null and NAI MUST be null. Other ST values are described 452 later in this document. 454 Flags is used to carry any additional information pertaining to SID. 455 Currently, the following flag bits are defined: 457 * M: When this bit is set, the SID value represents an MPLS label 458 stack entry as specified in [RFC5462] where only the label 459 value is specified by the PCE. Other fields (TC, S, and TTL) 460 fields MUST be considered invalid, and PCC MUST set these 461 fields according to its local policy and MPLS forwarding rules. 463 * C: When this bit as well as the M bit are set, then the SID 464 value represents an MPLS label stack entry as specified in 465 [RFC5462], where all the entry's fields (Label, TC, S, and TTL) 466 are specified by the PCE. However, a PCC MAY choose to 467 override TC, S, and TTL values according its local policy and 468 MPLS forwarding rules. 470 * S: When this bit is set, the SID value in the subobject body is 471 null. In this case, the PCC is responsible for choosing the 472 SID value, e.g., by looking up its TED using the NAI which, in 473 this case, MUST be present in the subobject. 475 * F: When this bit is set, the NAI value in the subobject body is 476 null. 478 SID is the Segment Identifier. 480 NAI contains the NAI associated with the SID. Depending on the 481 value of ST, the NAI can have different format as described in the 482 following section. 484 5.3.2. NAI Associated with SID 486 This document defines the following NAIs: 488 'IPv4 Node ID' is specified as an IPv4 address. In this case, ST 489 value is 1, and the Length is 8 or 12 depending on either SID or 490 NAI or both are included in the subobject. 492 'IPv6 Node ID' is specified as an IPv6 address. In this case, ST 493 and Length are 2, and Length is 8, 20, or 24 depending on either 494 SID or NAI or both are included in the subobject. 496 'IPv4 Adjacency' is specified as a pair of IPv4 addresses. In this 497 case, ST value is 3. The Length is 8, 12, or 16 depending on 498 either SID or NAI or both are included in the subobject, and the 499 format of the NAI is shown in the following figure: 501 0 1 2 3 502 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 1 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 504 | Local IPv4 address | 505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 506 | Remote IPv4 address | 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 Figure 3: NAI for IPv4 Adjacency 511 'IPv6 Adjacency' is specified as a pair of IPv6 addresses. In this 512 case, ST valie is 4. The Length is 8, 36 or 40 depending on 513 whether SID or NAI or both included in the subobject,and the 514 format of the NAI is shown in the following figure: 516 0 1 2 3 517 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 1 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 // Local IPv6 address (16 bytes) // 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 // Remote IPv6 address (16 bytes) // 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 524 Figure 4: NAI for IPv6 adjacenc y 526 'Unnumbered Adjacency with IPv4 NodeIDs' is specified as a pair of 527 Node ID / Interface ID tuples. In this case, ST value is 5. The 528 Length is 8, 20, or 24 depending on whether SID or NAI or both 529 included in the subobject, and the format of the NAI is shown in 530 the following figure: 532 0 1 2 3 533 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 1 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 | Local Node-ID | 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | Local Interface ID | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | Remote Node-ID | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 | Remote Interface ID | 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 Figure 5: NAI for Unnumbered adjacency with IPv4 Node IDs 546 Editorial Note: We are yet to decide if another SID subobject is 547 required for unnumbered adjacency with 128 bit node ID. 549 5.3.3. ERO Processing 551 A PCEP speaker that does not recognize the SR-ERO subobject in PCRep, 552 PCInitiate, PCUpd or PCRpt messages MUST reject the entire PCEP 553 message and MUST send a PCErr message with Error-Type=3 ("Unknown 554 Object") and Error-Value=2 ("Unrecognized object Type") or Error- 555 Type=4 ("Not supported object") and Error-Value=2 ("Not supported 556 object Type"), defined in [RFC5440]. 558 When the SID represents an MPLS label (i.e. the M bit is set), its 559 value (20 most significant bits) MUST be larger than 15, unless it is 560 special purpose label, such as an Entropy Label Indicator (ELI). If 561 a PCEP speaker receives a label ERO subobject with an invalid value, 562 it MUST send a PCErr message with Error-Type = 10 ("Reception of an 563 invalid object") and Error Value = TBD ("Bad label value"). If both 564 M and C bits of an ERO subobject are set, and if a PCEP speaker finds 565 erroneous setting in one or more of TC, S, and TTL fields, it MUST 566 send a PCErr message with Error-Type = 10 ("Reception of an invalid 567 object") and Error-Value = TBD ("Bad label format"). 569 If a PCC receives a stack of SR-ERO subobjects, and the number of 570 stack exceeds the maximum number of SIDs that the PCC can impose on 571 the packet, it MAY send a PCErr message with Error-Type = 10 572 ("Reception of an invalid object") and Error-Value = TBD 573 ("Unsupported number of Segment ERO subobjects"). 575 When a PCEP speaker detects that all subobjects of ERO are not 576 identical, and if it does not handle such ERO, it MUST send a PCErr 577 message with Error-Type = 10 ("Reception of an invalid object") and 578 Error-Value = TBD ("Non-identical ERO subobjects"). 580 If a PCEP speaker receives an SR-ERO subobject in which both SID and 581 NAI are absent, it MUST consider the entire ERO object invalid and 582 send a PCErr message with Error-Type = 10 ("Reception of an invalid 583 object") and Error-Value = TBD ("Both SID and NAI are absent in ERO 584 subobject"). 586 When a PCEP speaker receives an SR-ERO subobject in which ST is 0, 587 SID MUST be present and NAI MUST NOT be present(i.e., S-flag MUST be 588 0, F-flag MUST be 1, and the Length MUST be 8). Otherwise, it MUST 589 consider the entire ERO object invalid and send a PCErr message with 590 Error-Type = 10 ("Reception of an invalid object") and Error-Value = 591 TBD ("Malformed object"). The PCEP speaker MAY include the malformed 592 SR-ERO object in the PCErr message as well. 594 5.4. RRO Object 596 A PCC can record SR-TE LSP and report the LSP to a PCE via RRO. An 597 RRO object contains one or more subobjects called "SR-RRO subobjects" 598 whose format is shown below: 600 0 1 2 3 601 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 1 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 | Type | Length | ST | Flags |F|S|C|M| 604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 | SID | 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 // NAI (variable) // 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 Figure 6: SR-RRO Subobject format 612 The format of SR-RRO subobject is the same as that of SR-ERO 613 subobject without L flag. 615 A PCC MUST assume that SR-RRO subobjects are organized such that the 616 first subobject relative to the beginning of RRO contains the 617 information about the topmost label, and the last subobject contains 618 information about the bottommost label of the SR-TE LSP. 620 5.4.1. RRO Processing 622 Processing rules of SR-RRO subobject are identical to those of SR-ERO 623 subobject. 625 If a PCEP speaker receives an SR-RRO subobject in which both SID and 626 NAI are absent, it MUST consider the entire RRO object invalid and 627 send a PCErr message with Error-Type = 10 ("Reception of an invalid 628 object") and Error-Value = TBD ("Both SID and NAI are absent in RRO 629 subobject"). 631 If a PCE detects that all subobjects of RRO are not identical, and if 632 it does not handle such RRO, it MUST send a PCErr message with Error- 633 Type = 10 ("Reception of an invalid object") and Error-Value = TBD 634 ("Non-identical RRO subobjects"). 636 5.5. METRIC Object 638 If a PCEP session is established with an MSD value of zero, then the 639 PCC MAY specify the MSD for an individual path computation request 640 using the METRIC object defined in [RFC5440]. This document defines 641 a new type for the METRIC object to be used for this purpose as 642 follows: 644 o T = TBD (suggested value 11): Maximum SID Depth of the requested 645 path. 647 The PCC sets the metric-value to the MSD for this path. The PCC MUST 648 set the B (bound) bit to 1 in the METRIC object, which specifies that 649 the SID depth for the computed path MUST NOT exceed the metric-value. 651 If a PCEP session is established with a non-zero MSD value, then the 652 PCC MUST NOT send an MSD METRIC object. If the PCE receives a path 653 computation request with an MSD METRIC object on a session with a 654 non-zero MSD value then it MUST consider the request invalid and send 655 a PCErr with Error-Type = 10 ("Reception of an invalid object") and 656 Error-Value TBD ("Default MSD is specified for the PCEP session"). 658 6. Backward Compatibility 660 A PCEP speaker that does not support the SR PCEP capability cannot 661 recognize the SR-ERO or SR-RRO subobjects. As such, it MUST send a 662 PCEP error with Error-Type = 4 (Not supported object) and Error-Value 663 = 2 (Not supported object Type) as per [RFC5440]. 665 7. Management Considerations 667 7.1. Policy 669 PCEP implementation: 671 o Can enable SR PCEP capability either by default or via explicit 672 configuration. 674 o May generate PCEP error due to unsupported number of SR-ERO or SR- 675 RRO subobjects either by default or via explicit configuration. 677 7.2. The PCEP Data Model 679 A PCEP MIB module is defined in [I-D.ietf-pce-pcep-mib] needs be 680 extended to cover additional functionality provided by [RFC5440] and 681 [I-D.ietf-pce-pce-initiated-lsp]. Such extension will cover the new 682 functionality specified in this document. 684 8. Security Considerations 686 The security considerations described in [RFC5440] and 687 [I-D.ietf-pce-pce-initiated-lsp] are applicable to this 688 specification. No additional security measure is required. 690 9. IANA Considerations 692 9.1. PCEP Objects 694 This document defines a new sub-object type for the PCEP explicit 695 route object (ERO), and a new sub-object type for the PCEP record 696 route object (RRO). The code points for sub-object types of these 697 objects is maintained in the RSVP parameters registry, under the 698 EXPLICIT_ROUTE and ROUTE_RECORD objects. IANA is requested to 699 allocate code points in the RSVP Parameters registry for each of the 700 new sub-object types defined in this document, as follows: 702 Object Sub-Object Sub-Object Type 703 --------------------- -------------------------- ------------------ 704 EXPLICIT_ROUTE SR-ERO (PCEP-specific) TBD (recommended 36) 705 ROUTE_RECORD SR-RRO (PCEP-specific) TBD (recommended 36) 707 9.2. PCEP-Error Object 709 IANA is requested to allocate code-points in the PCEP-ERROR Object 710 Error Types and Values registry for the following new error-values: 712 Error-Type Meaning 713 ---------- ------- 714 10 Reception of an invalid object. 716 Error-value = TBD (recommended 2): Bad label value 717 Error-value = TBD (recommended 3): Unsupported number 718 of Segment ERO 719 subobjects 720 Error-value = TBD (recommended 4): Bad label format 721 Error-value = TBD (recommended 5): Non-identical ERO 722 subobjects 724 Error-value = TBD (recommended 6): Both SID and NAI 725 are absent in ERO 726 subobject 727 Error-value = TBD (recommended 7): Both SID and NAI 728 are absent in RRO 729 subobject 730 Error-value = TBD (recommended 9): Default MSD is 731 specified for the 732 PCEP session 733 Error-value = TBD (recommended 10): Non-identical RRO 734 subobjects 735 Error-value = TBD (recommended 11): Malformed object 737 9.3. PCEP TLV Type Indicators 739 IANA is requested to allocate a new code point in the PCEP TLV Type 740 Indicators registry, as follows: 742 Value Meaning Reference 743 ------------------------- ---------------------------- -------------- 744 TBD (recommended 26) SR-PCE-CAPABILITY This document 746 9.4. New Path Setup Type 748 [I-D.ietf-pce-lsp-setup-type] defines the PATH-SETUP-TYPE TLV and 749 requests that IANA creates a registry to manage the value of the 750 PATH_SETUP_TYPE TLV's PST field. IANA is requested to allocate a new 751 code point in the PCEP PATH_SETUP_TYPE TLV PST field registry, as 752 follows: 754 Value Description Reference 755 ------------------------- ---------------------------- -------------- 756 1 Traffic engineering path is This document 757 setup using Segment Routing 758 technique. 760 9.5. New Metric Type 762 IANA is requested to allocate a new code point in the PCEP METRIC 763 object T field registry, as follows: 765 Value Description Reference 766 ------------------------- ---------------------------- -------------- 767 TBD (recommended 11) Segment-ID (SID) Depth. This document 769 10. Contributors 771 The following people contributed to this document: 773 - Lakshmi Sharma 775 11. Acknowledgements 777 We like to thank Ina Minei, George Swallow, Marek Zavodsky and Tomas 778 Janciga for the valuable comments. 780 12. References 782 12.1. Normative References 784 [I-D.filsfils-rtgwg-segment-routing] 785 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 786 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 787 Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, 788 "Segment Routing Architecture", draft-filsfils-rtgwg- 789 segment-routing-01 (work in progress), October 2013. 791 [I-D.ietf-isis-segment-routing-extensions] 792 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 793 Litkowski, S., and J. Tantsura, "IS-IS Extensions for 794 Segment Routing", draft-ietf-isis-segment-routing- 795 extensions-00 (work in progress), April 2014. 797 [I-D.ietf-ospf-segment-routing-extensions] 798 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 799 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 800 Extensions for Segment Routing", draft-ietf-ospf-segment- 801 routing-extensions-00 (work in progress), June 2014. 803 [I-D.ietf-pce-lsp-setup-type] 804 Sivabalan, S., Medved, J., Minei, I., Crabbe, E., and R. 805 Varga, "Conveying path setup type in PCEP messages", 806 draft-ietf-pce-lsp-setup-type-00 (work in progress), 807 October 2014. 809 [I-D.ietf-pce-pce-initiated-lsp] 810 Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 811 Extensions for PCE-initiated LSP Setup in a Stateful PCE 812 Model", draft-ietf-pce-pce-initiated-lsp-01 (work in 813 progress), June 2014. 815 [I-D.ietf-pce-pcep-mib] 816 Koushik, K., Stephan, E., Zhao, Q., King, D., and J. 817 Hardwick, "PCE communication protocol (PCEP) Management 818 Information Base", draft-ietf-pce-pcep-mib-04 (work in 819 progress), February 2013. 821 [I-D.ietf-pce-stateful-pce] 822 Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP 823 Extensions for Stateful PCE", draft-ietf-pce-stateful- 824 pce-05 (work in progress), July 2013. 826 [I-D.tantsura-idr-bgp-ls-segment-routing-msd] 827 Tantsura, J., Mirsky, G., Sivabalan, S., and U. Chunduri, 828 "Signaling Maximum SID Depth using Border Gateway Protocol 829 Link-State", draft-tantsura-idr-bgp-ls-segment-routing- 830 msd-01 (work in progress), July 2016. 832 [I-D.tantsura-isis-segment-routing-msd] 833 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 834 Depth) using IS-IS", draft-tantsura-isis-segment-routing- 835 msd-01 (work in progress), July 2016. 837 [I-D.tantsura-ospf-segment-routing-msd] 838 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 839 Depth) using OSPF", draft-tantsura-ospf-segment-routing- 840 msd-01 (work in progress), September 2016. 842 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 843 Requirement Levels", BCP 14, RFC 2119, 844 DOI 10.17487/RFC2119, March 1997, 845 . 847 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 848 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 849 DOI 10.17487/RFC5440, March 2009, 850 . 852 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 853 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 854 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 855 2009, . 857 12.2. Informative References 859 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 860 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 861 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 862 . 864 [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label 865 Switching (GMPLS) Signaling Resource ReserVation Protocol- 866 Traffic Engineering (RSVP-TE) Extensions", RFC 3473, 867 DOI 10.17487/RFC3473, January 2003, 868 . 870 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 871 in Resource ReSerVation Protocol - Traffic Engineering 872 (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, 873 . 875 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 876 Element (PCE) Communication Protocol Generic 877 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 878 2006, . 880 Authors' Addresses 882 Siva Sivabalan 883 Cisco Systems, Inc. 884 2000 Innovation Drive 885 Kanata, Ontario K2K 3E8 886 Canada 888 Email: msiva@cisco.com 890 Jan Medved 891 Cisco Systems, Inc. 892 170 West Tasman Dr. 893 San Jose, CA 95134 894 US 896 Email: jmedved@cisco.com 898 Clarence Filsfils 899 Cisco Systems, Inc. 900 Pegasus Parc 901 De kleetlaan 6a, DIEGEM BRABANT 1831 902 BELGIUM 904 Email: cfilsfil@cisco.com 905 Edward Crabbe 906 Oracle 907 1501 4th Ave, suite 1800 908 Seattle, WA 98101 909 USA 911 Email: edward.crabbe@oracle.com 913 Robert Raszuk 914 Mirantis Inc. 915 100-615 National Ave. 916 Mountain View, CA 94043 917 US 919 Email: robert@raszuk.net 921 Victor Lopez 922 Telefonica I+D 923 Don Ramon de la Cruz 82-84 924 Madrid 28045 925 Spain 927 Email: vlopez@tid.es 929 Jeff Tantsura 930 Individual 931 444 San Antonio Rd, 10A 932 Palo Alto, CA 94306 933 USA 935 Email: jefftant.ietf@gmail.com 937 Wim Henderickx 938 Nokia 939 Copernicuslaan 50 940 Antwerp 2018, CA 95134 941 BELGIUM 943 Email: wim.henderickx@alcatel-lucent.com 944 Jon Hardwick 945 Metaswitch Networks 946 100 Church Street 947 Enfield, Middlesex 948 UK 950 Email: jon.hardwick@metaswitch.com