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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-22) exists of draft-ietf-idr-flow-spec-v6-11 == Outdated reference: A later version (-27) exists of draft-ietf-idr-rfc5575bis-25 == Outdated reference: A later version (-23) exists of draft-ietf-idr-flowspec-l2vpn-15 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-13 == Outdated reference: A later version (-22) exists of draft-ietf-teas-yang-path-computation-08 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Dhody 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track A. Farrel 5 Expires: December 3, 2020 Old Dog Consulting 6 Z. Li 7 Huawei Technologies 8 June 1, 2020 10 PCEP Extension for Flow Specification 11 draft-ietf-pce-pcep-flowspec-09 13 Abstract 15 The Path Computation Element (PCE) is a functional component capable 16 of selecting paths through a traffic engineering network. These 17 paths may be supplied in response to requests for computation, or may 18 be unsolicited instructions issued by the PCE to network elements. 19 Both approaches use the PCE Communication Protocol (PCEP) to convey 20 the details of the computed path. 22 Traffic flows may be categorized and described using "Flow 23 Specifications". RFC XXXX defines the Flow Specification and 24 describes how Flow Specification Components are used to describe 25 traffic flows. RFC XXXX also defines how Flow Specifications may be 26 distributed in BGP to allow specific traffic flows to be associated 27 with routes. 29 This document specifies a set of extensions to PCEP to support 30 dissemination of Flow Specifications. This allows a PCE to indicate 31 what traffic should be placed on each path that it is aware of. 33 RFC Editor Note: Please replace XXXX in the Abstract with the RFC 34 number assigned to draft-ietf-idr-rfc5575bis when it is published. 35 Please remove this note. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at https://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on December 3, 2020. 54 Copyright Notice 56 Copyright (c) 2020 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (https://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 3. Procedures for PCE Use of Flow Specifications . . . . . . . . 5 74 3.1. Context for PCE Use of Flow Specifications . . . . . . . 5 75 3.2. Elements of Procedure . . . . . . . . . . . . . . . . . . 6 76 3.2.1. Capability Advertisement . . . . . . . . . . . . . . 6 77 3.2.2. Dissemination Procedures . . . . . . . . . . . . . . 7 78 3.2.3. Flow Specification Synchronization . . . . . . . . . 8 79 4. PCE FlowSpec Capability TLV . . . . . . . . . . . . . . . . . 9 80 5. PCEP FLOWSPEC Object . . . . . . . . . . . . . . . . . . . . 9 81 6. Flow Filter TLV . . . . . . . . . . . . . . . . . . . . . . . 11 82 7. Flow Specification TLVs . . . . . . . . . . . . . . . . . . . 12 83 8. Detailed Procedures . . . . . . . . . . . . . . . . . . . . . 15 84 8.1. Default Behavior and Backward Compatibility . . . . . . . 16 85 8.2. Composite Flow Specifications . . . . . . . . . . . . . . 16 86 8.3. Modifying Flow Specifications . . . . . . . . . . . . . . 16 87 8.4. Multiple Flow Specifications . . . . . . . . . . . . . . 16 88 8.5. Adding and Removing Flow Specifications . . . . . . . . . 17 89 8.6. VPN Identifiers . . . . . . . . . . . . . . . . . . . . . 17 90 8.7. Priorities and Overlapping Flow Specifications . . . . . 17 91 9. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . . 18 92 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 93 10.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 21 94 10.1.1. PCEP FLOWSPEC Object Flag Field . . . . . . . . . . 21 95 10.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 22 96 10.3. Flow Specification TLV Type Indicators . . . . . . . . . 22 97 10.4. PCEP Error Codes . . . . . . . . . . . . . . . . . . . . 23 98 10.5. PCE Capability Flag . . . . . . . . . . . . . . . . . . 24 99 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 24 100 12. Security Considerations . . . . . . . . . . . . . . . . . . . 24 101 13. Manageability Considerations . . . . . . . . . . . . . . . . 25 102 13.1. Management of Multiple Flow Specifications . . . . . . . 25 103 13.2. Control of Function through Configuration and Policy . . 26 104 13.3. Information and Data Models . . . . . . . . . . . . . . 27 105 13.4. Liveness Detection and Monitoring . . . . . . . . . . . 27 106 13.5. Verifying Correct Operation . . . . . . . . . . . . . . 27 107 13.6. Requirements on Other Protocols and Functional 108 Components . . . . . . . . . . . . . . . . . . . . . . . 27 109 13.7. Impact on Network Operation . . . . . . . . . . . . . . 27 110 13.8. Other Considerations . . . . . . . . . . . . . . . . . . 28 111 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 112 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 113 15.1. Normative References . . . . . . . . . . . . . . . . . . 28 114 15.2. Informative References . . . . . . . . . . . . . . . . . 29 115 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 31 116 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 118 1. Introduction 120 [RFC4655] defines the Path Computation Element (PCE), a functional 121 component capable of computing paths for use in traffic engineering 122 networks. PCE was originally conceived for use in Multiprotocol 123 Label Switching (MPLS) for Traffic Engineering (TE) networks to 124 derive the routes of Label Switched Paths (LSPs). However, the scope 125 of PCE was quickly extended to make it applicable to Generalized MPLS 126 (GMPLS)-controlled networks, and more recent work has brought other 127 traffic engineering technologies and planning applications into scope 128 (for example, Segment Routing (SR) [RFC8664]). 130 [RFC5440] describes the Path Computation Element Communication 131 Protocol (PCEP). PCEP defines the communication between a Path 132 Computation Client (PCC) and a PCE, or between PCE and PCE, enabling 133 computation of path for MPLS-TE LSPs. 135 Stateful PCE [RFC8231] specifies a set of extensions to PCEP to 136 enable control of TE-LSPs by a PCE that retains state about the LSPs 137 provisioned in the network (a stateful PCE). [RFC8281] describes the 138 setup, maintenance, and teardown of LSPs initiated by a stateful PCE 139 without the need for local configuration on the PCC, thus allowing 140 for a dynamic network that is centrally controlled. [RFC8283] 141 introduces the architecture for PCE as a central controller and 142 describes how PCE can be viewed as a component that performs 143 computation to place 'flows' within the network and decide how these 144 flows are routed. 146 The description of traffic flows by the combination of multiple Flow 147 Specification Components and their dissemination as traffic flow 148 specifications (Flow Specifications) is described for BGP in 149 [I-D.ietf-idr-rfc5575bis]. A Flow Specification is comprised of 150 traffic filtering rules and actions. The routers that receive a Flow 151 Specification can classify received packets according to the traffic 152 filtering rules and can direct packets based on the actions. 154 When a PCE is used to initiate tunnels (such as TE-LSPs or SR paths) 155 using PCEP, it is important that the head end of the tunnels 156 understands what traffic to place on each tunnel. The data flows 157 intended for a tunnel can be described using Flow Specification 158 Components. When PCEP is in use for tunnel initiation it makes sense 159 for that same protocol to be used to distribute the Flow 160 Specification Components that describe what data is to flow on those 161 tunnels. 163 This document specifies a set of extensions to PCEP to support 164 dissemination of Flow Specifications Components. For convenience we 165 term the description of a traffic flow using Flow Specification 166 Components as a "Flow Specification" and it must be understood that 167 this is not the same as the same term used in 168 [I-D.ietf-idr-rfc5575bis] since no action is explicitly included in 169 the encoding. 171 The extensions defined in this document include the creation, update, 172 and withdrawal of Flow Specifications via PCEP, and can be applied to 173 tunnels initiated by the PCE or to tunnels where control is delegated 174 to the PCE by the PCC. Furthermore, a PCC requesting a new path can 175 include Flow Specifications in the request to indicate the purpose of 176 the tunnel allowing the PCE to factor this into the path computation. 178 Flow Specifications are carried in TLVs within a new object called 179 the FLOWSPEC object defined in this document. The flow filtering 180 rules indicated by the Flow Specifications are mainly defined by BGP 181 Flow Specifications. 183 2. Terminology 185 This document uses the following terms defined in [RFC5440]: PCC, 186 PCE, PCEP Peer. 188 The following term from [I-D.ietf-idr-rfc5575bis] is used frequently 189 throughout this document: 191 Flow Specification (FlowSpec): A Flow Specification is an n-tuple 192 consisting of several matching criteria that can be applied to IP 193 traffic, including filters and actions. Each FlowSpec consists of 194 a set of filters and a set of actions. 196 However, in the context of this document, no action is specified as 197 part of the FlowSpec since the action "forward all matching traffic 198 onto the associated path" is implicit. How an implementation decides 199 how to filter traffic that matches a Flow Specification does not form 200 part of this specification, but a flag is provided to indicate that 201 the sender of a PCEP message that includes a Flow Specification is 202 intended to be installed as a Longest Prefix Match route, or as a 203 Flow Specification policy. 205 This document uses the terms "stateful PCE" and "active PCE" as 206 advocated in [RFC7399]. 208 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 209 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 210 "OPTIONAL" in this document are to be interpreted as described in BCP 211 14 [RFC2119] [RFC8174] when, and only when, they appear in all 212 capitals, as shown here. 214 3. Procedures for PCE Use of Flow Specifications 216 3.1. Context for PCE Use of Flow Specifications 218 In the PCE architecture there are five steps in the setup and use of 219 LSPs: 221 1. Decide which LSPs to set up. The decision may be made by a user, 222 by a PCC, or by the PCE. There can be a number of triggers for 223 this including user intervention and dynamic response to changes 224 in traffic demands. 226 2. Decide what properties to assign to an LSP. This can include 227 bandwidth reservations, priorities, and DSCP (i.e., MPLS Traffic 228 Class field). This function is also determined by user 229 configuration or response to predicted or observed traffic 230 demands. 232 3. Decide what traffic to put on the LSP. This is effectively 233 determining which traffic flows to assign to which LSPs, and 234 practically, this is closely linked to the first two decisions 235 listed above. 237 4. Cause the LSP to be set up and modified to have the right 238 characteristics. This will usually involve the PCE advising or 239 instructing the PCC which will then signal the LSP across the 240 network. 242 5. Tell the head end what traffic to put on the LSP. This may 243 happen after or at the same time as the LSP is set up. This step 244 is the subject of this document. 246 3.2. Elements of Procedure 248 There are three elements of procedure: 250 o A PCE and a PCC must be able to indicate whether or not they 251 support the use of Flow Specifications. 253 o A PCE or PCC must be able to include Flow Specifications in PCEP 254 messages with clear understanding of the applicability of those 255 Flow Specifications in each case. This includes whether the use 256 of such information is mandatory, constrained, or optional, and 257 how overlapping Flow Specifications will be resolved. 259 o Flow Specification information/state must be synchronized between 260 PCEP peers so that, on recovery, the peers have the same 261 understanding of which Flow Specifications apply. 263 The following subsections describe these points. 265 3.2.1. Capability Advertisement 267 As with most PCEP capability advertisements, the ability to support 268 Flow Specifications can be indicated in the PCEP OPEN message or in 269 IGP PCE capability advertisements. 271 3.2.1.1. PCEP OPEN Message 273 During PCEP session establishment, a PCC or PCE that supports the 274 procedures described in this document announces this fact by 275 including the "PCE FlowSpec Capability" TLV (described in Section 4) 276 in the OPEN Object carried in the PCEP Open message. 278 The presence of the PCE FlowSpec Capability TLV in the OPEN Object in 279 a PCE's OPEN message indicates that the PCE can distribute FlowSpecs 280 to PCCs and can receive FlowSpecs in messages from PCCs. 282 The presence of the PCE FlowSpec Capability TLV in the OPEN Object in 283 a PCC's OPEN message indicates that the PCC supports the FlowSpec 284 functionality described in this document. 286 If either one of a pair of PCEP peers does not indicate support of 287 the functionality described in this document by not including the PCE 288 FlowSpec Capability TLV in the OPEN Object in its OPEN message, then 289 the other peer MUST NOT include a FLOWSPEC object in any PCEP message 290 sent to the peer that does not support the procedures. If a FLOWSPEC 291 object is received when support has not been indicated, the receiver 292 will respond with a PCErr message reporting the objects containing 293 the FlowSpec as described in [RFC5440]: that is, it will use 'Unknown 294 Object' if it does not support this specification, and 'Not supported 295 object' if it supports this specification but has not chosen to 296 support FLOWSPEC objects on this PCEP session. 298 3.2.1.2. IGP PCE Capabilities Advertisement 300 The ability to advertise support for PCEP and PCE features in IGP 301 advertisements is provided for OSPF in [RFC5088] and for IS-IS in 302 [RFC5089]. The mechanism uses the PCE Discovery TLV which has a PCE- 303 CAP-FLAGS sub-TLV containing bit-flags each of which indicates 304 support for a different feature. 306 This document defines a new PCE-CAP-FLAGS sub-TLV bit, the FlowSpec 307 Capable flag (bit number TBD1). Setting the bit indicates that an 308 advertising PCE supports the procedures defined in this document. 310 Note that while PCE FlowSpec Capability may be advertised during 311 discovery, PCEP speakers that wish to use Flow Specification in PCEP 312 MUST negotiate PCE FlowSpec Capability during PCEP session setup, as 313 specified in Section 3.2.1.1. A PCC MAY initiate PCE FlowSpec 314 Capability negotiation at PCEP session setup even if it did not 315 receive any IGP PCE capability advertisement, and a PCEP peer that 316 advertised support for FlowSpec in the IGP is not obliged to support 317 these procedures on any given PCEP session. 319 3.2.2. Dissemination Procedures 321 This section describes the procedures to support Flow Specifications 322 in PCEP messages. 324 The primary purpose of distributing Flow Specification information is 325 to allow a PCE to indicate to a PCC what traffic it should place on a 326 path (such as an LSP or an SR path). This means that the Flow 327 Specification may be included in: 329 o PCInitiate messages so that an active PCE can indicate the traffic 330 to place on a path at the time that the PCE instantiates the path. 332 o PCUpd messages so that an active PCE can indicate or change the 333 traffic to place on a path that has already been set up. 335 o PCRpt messages so that a PCC can report the traffic that the PCC 336 plans to place on the path. 338 o PCReq messages so that a PCC can indicate what traffic it plans to 339 place on a path at the time it requests the PCE to perform a 340 computation in case that information aids the PCE in its work. 342 o PCRep messages so that a PCE that has been asked to compute a path 343 can suggest which traffic could be placed on a path that a PCC may 344 be about to set up. 346 o PCErr messages so that issues related to paths and the traffic 347 they carry can be reported to the PCE by the PCC, and so that 348 problems with other PCEP messages that carry Flow Specifications 349 can be reported. 351 To carry Flow Specifications in PCEP messages, this document defines 352 a new PCEP object called the PCEP FLOWSPEC object. The object is 353 OPTIONAL in the messages described above and MAY appear more than 354 once in each message. 356 The PCEP FLOWSPEC object carries zero or one Flow Filter TLV which 357 describes a traffic flow. 359 The inclusion of multiple PCEP FLOWSPEC objects allows multiple 360 traffic flows to be placed on a single path. 362 Once a PCE and PCC have established that they can both support the 363 use of Flow Specifications in PCEP messages, such information may be 364 exchanged at any time for new or existing paths. 366 The application and prioritization of Flow Specifications is 367 described in Section 8.7. 369 As per [RFC8231], any attributes of the path received from a PCE are 370 subject to PCC's local policy. This holds good for the Flow 371 Specifications as well. 373 3.2.3. Flow Specification Synchronization 375 The Flow Specifications are carried along with the LSP State 376 information as per [RFC8231] making the Flow Specifications part of 377 the LSP database (LSP-DB). Thus, the synchronization of the Flow 378 Specification information is done as part of LSP-DB synchronization. 379 This may be achieved using normal state synchronization procedures as 380 described in [RFC8231] or enhanced state synchronization procedures 381 as defined in [RFC8232]. 383 The approach selected will be implementation and deployment specific 384 and will depend on issues such as how the databases are constructed 385 and what level of synchronization support is needed. 387 4. PCE FlowSpec Capability TLV 389 The PCE-FLOWSPEC-CAPABILITY TLV is an optional TLV that can be 390 carried in the OPEN Object [RFC5440] to exchange PCE FlowSpec 391 capabilities of the PCEP speakers. 393 The format of the PCE-FLOWSPEC-CAPABILITY TLV follows the format of 394 all PCEP TLVs as defined in [RFC5440] and is shown in Figure 1. 396 0 1 2 3 397 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 1 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | Type=TBD2 | Length=2 | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | Value=0 | Padding | 402 +---------------------------------------------------------------+ 404 Figure 1: PCE-FLOWSPEC-CAPABILITY TLV format 406 The type of the PCE-FLOWSPEC-CAPABILITY TLV is TBD2 and it has a 407 fixed length of 2 octets. The Value field is set to default value 0. 408 The two bytes of padding MUST be set to zero and ignored on receipt. 410 The inclusion of this TLV in an OPEN object indicates that the sender 411 can perform FlowSpec handling as defined in this document. 413 5. PCEP FLOWSPEC Object 415 The PCEP FLOWSPEC object defined in this document is compliant with 416 the PCEP object format defined in [RFC5440]. It is OPTIONAL in the 417 PCReq, PCRep, PCErr, PCInitiate, PCRpt, and PCUpd messages and MAY be 418 present zero, one, or more times. Each instance of the object 419 specifies a traffic flow. 421 The PCEP FLOWSPEC object carries a FlowSpec filter rule encoded in a 422 TLV (as defined in Section 6). 424 The FLOWSPEC Object-Class is TBD3 (to be assigned by IANA). 426 The FLOWSPEC Object-Type is 1. 428 The format of the body of the PCEP FLOWSPEC object is shown in 429 Figure 2 430 0 1 2 3 431 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 1 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | FS-ID | 434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 435 | AFI | Reserved | Flags |L|R| 436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 | | 438 // TLVs // 439 | | 440 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 Figure 2: PCEP FLOWSPEC Object Body Format 444 FS-ID (32-bits): A PCEP-specific identifier for the FlowSpec 445 information. A PCE or PCC creates an FS-ID for each FlowSpec that it 446 originates, and the value is unique within the scope of that PCE or 447 PCC and is constant for the lifetime of a PCEP session. All 448 subsequent PCEP messages can identify the FlowSpec using the FS-ID. 449 The values 0 and 0xFFFFFFFF are reserved and MUST NOT be used. 451 AFI (16-bits): Address Family Identifier as used in BGP [RFC4760] 452 (AFI=1 for IPv4 or VPNv4, AFI=2 for IPv6 and VPNv6 as per as per 453 [I-D.ietf-idr-flow-spec-v6]). 455 Reserved (8-bits): MUST be set to zero on transmission and ignored on 456 receipt. 458 Flags (8-bits): Two flags are currently assigned - 460 R bit: The Remove bit is set when a PCEP FLOWSPEC object is 461 included in a PCEP message to indicate removal of the Flow 462 Specification from the associated tunnel. If the bit is clear, 463 the Flow Specification is being added or modified. 465 L bit: The Longest Prefix Match (LPM) bit is set to indicate that 466 the Flow Specification is to be installed as a route subject to 467 longest prefix match forwarding. If the bit is clear, the Flow 468 Specification described by the Flow Filter TLV (see Section 6) is 469 to be installed as a Flow Specification. If the bit is set, only 470 Flow Specifications that describe IPv4 or IPv6 destinations are 471 meaningful in the Flow Filter TLV. If the L is set and the 472 receiver does not support the use of Flow Specifications that are 473 present in the Flow Filter TLV for the installation of a route 474 subject to longest prefix match forwarding, then the PCEP peer 475 MUST respond with a PCErr message with error-type TBD8 (FlowSpec 476 Error) and error-value 5 (Unsupported LPM Route). 478 Unassigned bits MUST be set to zero on transmission and ignored on 479 receipt. 481 If the PCEP speaker receives a message with R bit set in the FLOWSPEC 482 object and the Flow Specification identified with a FS-ID does not 483 exist, it MUST generate a PCErr with Error-type TBD8 (FlowSpec 484 Error), error-value 4 (Unknown FlowSpec). 486 If the PCEP speaker does not understand or support the AFI in the 487 FLOWSPEC message, the PCEP peer MUST respond with a PCErr message 488 with error-type TBD8 (FlowSpec Error), error-value 2 (Malformed 489 FlowSpec). 491 The following TLVs can be used in the FLOWSPEC object: 493 o Speaker Entity Identifier TLV: As specified in [RFC8232], SPEAKER- 494 ENTITY-ID TLV encodes a unique identifier for the node that does 495 not change during the lifetime of the PCEP speaker. This is used 496 to uniquely identify the FlowSpec originator and thus used in 497 conjunction with FS-ID to uniquely identify the FlowSpec 498 information. This TLV MUST be included. If the TLV is missing, 499 the PCEP peer MUST respond with a PCErr message with error-type 500 TBD8 (FlowSpec Error), error-value 2 (Malformed FlowSpec). 502 o Flow Filter TLV (variable): One TLV MAY be included. The Flow 503 Filter TLV is OPTIONAL when the R bit is set. The TLV MUST be 504 present when the R bit is clear. If the TLV is missing when the R 505 bit is clear, the PCEP peer MUST respond with a PCErr message with 506 error-type TBD8 (FlowSpec Error) and error-value 2 (Malformed 507 FlowSpec). 509 6. Flow Filter TLV 511 A new PCEP TLV is defined to convey Flow Specification filtering 512 rules that specify what traffic is carried on a path. The TLV 513 follows the format of all PCEP TLVs as defined in [RFC5440]. The 514 Type field values come from the codepoint space for PCEP TLVs and has 515 the value TBD4. 517 The Value field contains one or more sub-TLVs (the Flow Specification 518 TLVs) as defined in Section 7. Only one Flow Filter TLV can be 519 present and represents the complete definition of a Flow 520 Specification for traffic to be placed on the tunnel. This tunnel is 521 indicated by the PCEP message in which the PCEP FLOWSPEC object is 522 carried. The set of Flow Specification TLVs in a single instance of 523 a Flow Filter TLV are combined to indicate the specific Flow 524 Specification. 526 Further Flow Specifications can be included in a PCEP message by 527 including additional FLOWSPEC objects. 529 7. Flow Specification TLVs 531 The Flow Filter TLV carries one or more Flow Specification TLV. The 532 Flow Specification TLV follows the format of all PCEP TLVs as defined 533 in [RFC5440]. However, the Type values are selected from a separate 534 IANA registry (see Section 10) rather than from the common PCEP TLV 535 registry. 537 Type values are chosen so that there can be commonality with Flow 538 Specifications defined for use with BGP [I-D.ietf-idr-rfc5575bis]. 539 This is possible because the BGP Flow Spec encoding uses a single 540 octet to encode the type where as PCEP uses two octets. Thus the 541 space of values for the Type field is partitioned as shown in 542 Figure 3. 544 Range | 545 ---------------+--------------------------------------------------- 546 0 | Reserved - must not be allocated. 547 | 548 1 .. 255 | Per BGP registry defined by 549 | [I-D.ietf-idr-rfc5575bis] and 550 | [I-D.ietf-idr-flow-spec-v6]. 551 | Not to be allocated in this registry. 552 | 553 256 .. 65535 | New PCEP Flow Specifications allocated according 554 | to the registry defined in this document. 556 Figure 3: Flow Specification TLV Type Ranges 558 [I-D.ietf-idr-rfc5575bis] is the reference for the registry "Flow 559 Spec Component Types" and defines the allocations it contains. 560 [I-D.ietf-idr-flow-spec-v6] requested for another registry "Flow Spec 561 IPv6 Component Types" and requested initial allocations in it. If 562 the AFI (in the FLOWSPEC object) is set to IPv4, the range 1..255 is 563 as per "Flow Spec Component Types" [I-D.ietf-idr-rfc5575bis]; if the 564 AFI is set to IPv6, the range 1..255 is as per "Flow Spec IPv6 565 Component Types" [I-D.ietf-idr-flow-spec-v6]. When future BGP 566 specifications (such as [I-D.ietf-idr-flowspec-l2vpn]) make further 567 allocations to the aforementioned registries, they are also inherited 568 for PCEP usage. 570 The content of the Value field in each TLV is specific to the type/ 571 AFI and describes the parameters of the Flow Specification. The 572 definition of the format of many of these Value fields is inherited 573 from BGP specifications. Specifically, the inheritance is from 574 [I-D.ietf-idr-rfc5575bis] and [I-D.ietf-idr-flow-spec-v6], but may 575 also be inherited from future BGP specifications. 577 When multiple Flow Specification TLVs are present in a single Flow 578 Filter TLV they are combined to produce a more detailed specification 579 of a flow. For examples and rules about how this is achieved, see 580 [I-D.ietf-idr-rfc5575bis]. 582 An implementation that receives a PCEP message carrying a Flow 583 Specification TLV with a type value that it does not recognize or 584 does not support MUST respond with a PCErr message with error-type 585 TBD8 (FlowSpec Error), error-value 1 (Unsupported FlowSpec) and MUST 586 NOT install the Flow Specification. 588 When used in other protocols (such as BGP), these Flow Specifications 589 are also associated with actions to indicate how traffic matching the 590 Flow Specification should be treated. In PCEP, however, the only 591 action is to associate the traffic with a tunnel and to forward 592 matching traffic onto that path, so no encoding of an action is 593 needed. 595 Section 8.7 describes how overlapping Flow Specifications are 596 prioritized and handled. 598 All Flow Specification TLVs with Types in the range 1 to 255 have 599 Values defined for use in BGP (for example, in 600 [I-D.ietf-idr-rfc5575bis], [I-D.ietf-idr-flow-spec-v6], and 601 [I-D.ietf-idr-flowspec-l2vpn]) and are set using the BGP encoding, 602 but without the type octet (the relevant information is in the Type 603 field of the TLV). The Value field is padded with trailing zeros to 604 achieve 4-byte alignment. 606 This document defines following new types - 607 +-------+-------------------------+-----------------------------+ 608 | Type | Description | Value defined in | 609 | | | | 610 +-------+-------------------------+-----------------------------+ 611 | TBD5 | Route Distinguisher | [This.I-D] | 612 +-------+-------------------------+-----------------------------+ 613 | TBD6 | IPv4 Multicast Flow | [This.I-D] | 614 +-------+-------------------------+-----------------------------+ 615 | TBD7 | IPv6 Multicast Flow | [This.I-D] | 616 +-------+-------------------------+-----------------------------+ 618 Figure 4: Table of Flow Specification TLV Types defined in this 619 document 621 To allow identification of a VPN in PCEP via a Route Distinguisher 622 (RD) [RFC4364], a new TLV - ROUTE-DISTINGUISHER TLV is defined in 623 this document. A Flow Specification TLV with Type TBD5 (ROUTE- 624 DISTINGUISHER TLV) carries an RD Value, used to identify that other 625 flow filter information (for example, an IPv4 destination prefix) is 626 associated with a specific VPN identified by the RD. See Section 8.6 627 for further discussion of VPN identification. 629 0 1 2 3 630 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 1 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 | Type=[TBD5] | Length=8 | 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 | Route Distinguisher | 635 | | 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 Figure 5: The Format of the ROUTE-DISTINGUISHER TLV 640 The format of RD is as per [RFC4364]. 642 Although it may be possible to describe a multicast Flow 643 Specification from the combination of other Flow Specification TLVs 644 with specific values, it is more convenient to use a dedicated Flow 645 Specification TLV. Flow Specification TLVs with Type values TBD6 and 646 TBD7 are used to identify a multicast flow for IPv4 and IPv6 647 respectively. The Value field is encoded as shown in Figure 6. 649 0 1 2 3 650 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 1 651 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 652 | Reserved |S|G| Src Mask Len | Grp Mask Len | 653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 ~ Source Address ~ 655 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 ~ Group multicast Address ~ 657 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 Figure 6: Multicast Flow Specification TLV Encoding 661 The address fields and address mask lengths of the two Multicast Flow 662 Specification TLVs contain source and group prefixes for matching 663 against packet flows noting that the two address fields are 32 bits 664 for an IPv4 Multicast Flow and 128 bits for an IPv6 Multicast Flow. 666 The Reserved field MUST be set to zero and ignored on receipt. 668 Two bit flags (S and G) are defined to describe the multicast 669 wildcarding in use. If the S bit is set, then source wildcarding is 670 in use and the values in the Source Mask Length and Source Address 671 fields MUST be ignored. If the G bit is set, then group wildcarding 672 is in use and the values in the Group Mask Length and Group multicast 673 Address fields MUST be ignored. The G bit MUST NOT be set unless the 674 S bit is also set: if a Multicast Flow Specification TLV is received 675 with S bit = 0 and G bit = 1 the receiver MUST respond with a PCErr 676 with Error-type TBD8 (FlowSpec Error) and error-value 2 (Malformed 677 FlowSpec). 679 The three multicast mappings may be achieved as follows: 681 (S, G) - S bit = 0, G bit = 0, the Source Address and Group 682 multicast Address prefixes are both used to define the multicast 683 flow. 685 (*, G) - S bit = 1, G bit = 0, the Group multicast Address prefix, 686 but the Source Address prefix is ignored. 688 (*, *) = S bit = 1, G bit = 1, the Source Address and Group 689 multicast Address prefixes are both ignored. 691 8. Detailed Procedures 693 This section outlines some specific detailed procedures for using the 694 protocol extensions defined in this document. 696 8.1. Default Behavior and Backward Compatibility 698 The default behavior is that no Flow Specification is applied to a 699 tunnel. That is, the default is that the FLOWSPEC object is not used 700 as is the case in all systems before the implementation of this 701 specification. 703 In this case, it is a local matter (such as through configuration) 704 how tunnel head ends are instructed what traffic to place on a 705 tunnel. 707 [RFC5440] describes how receivers respond when they see unknown PCEP 708 objects. 710 8.2. Composite Flow Specifications 712 Flow Specifications may be represented by a single Flow Specification 713 TLV or may require a more complex description using multiple Flow 714 Specification TLVs. For example, a flow indicated by a source- 715 destination pair of IPv6 addresses would be described by the 716 combination of Destination IPv6 Prefix and Source IPv6 Prefix Flow 717 Specification TLVs. 719 8.3. Modifying Flow Specifications 721 A PCE may want to modify a Flow Specification associated with a 722 tunnel, or a PCC may want to report a change to the Flow 723 Specification it is using with a tunnel. 725 It is important that the specific Flow Specification is identified so 726 that it is clear that this is a modification of an existing flow and 727 not the addition of a new flow as described in Section 8.4. The FS- 728 ID field of the PCEP FLOWSPEC object is used to identify a specific 729 Flow Specification. 731 When modifying a Flow Specification, all Flow Specification TLVs for 732 the intended specification of the flow MUST be included in the PCEP 733 FLOWSPEC object and the FS-ID MUST be retained from the previous 734 description of the flow. 736 8.4. Multiple Flow Specifications 738 It is possible that multiple flows will be place on a single tunnel. 739 In some cases it is possible to to define these within a single PCEP 740 FLOWSPEC object: for example, two Destination IPv4 Prefix TLVs could 741 be included to indicate that packets matching either prefix are 742 acceptable. PCEP would consider this as a single Flow Specification 743 identified by a single FS-ID. 745 In other scenarios the use of multiple Flow Specification TLVs would 746 be confusing. For example, if flows from A to B and from C to D are 747 to be included then using two Source IPv4 Prefix TLVs and two 748 Destination IPv4 Prefix TLVs would be confusing (are flows from A to 749 D included?). In these cases, each Flow Specification is carried in 750 its own PCEP FLOWSPEC object with multiple objects present on a 751 single PCEP message. Use of separate objects also allows easier 752 removal and modification of Flow Specifications. 754 8.5. Adding and Removing Flow Specifications 756 The Remove bit in the PCEP FLOWSPEC object is left clear when a Flow 757 Specification is being added or modified. 759 To remove a Flow Specification, a PCEP FLOWSPEC object is included 760 with the FS-ID matching the one being removed, and the R bit set to 761 indicate removal. In this case it is not necessary to include any 762 Flow Specification TLVs. 764 If the R bit is set and Flow Specification TLVs are present, an 765 implementation MAY ignore them. If the implementation checks the 766 Flow Specification TLVs against those recorded for the FS-ID of the 767 Flow Specification being removed and finds a mismatch, the Flow 768 Specification MUST still be removed and the implementation SHOULD 769 record a local exception or log. 771 8.6. VPN Identifiers 773 VPN instances are identified in BGP using Route Distinguishers (RDs) 774 [RFC4364]. These values are not normally considered to have any 775 meaning outside of the network, and they are not encoded in data 776 packets belonging to the VPNs. However, RDs provide a useful way of 777 identifying VPN instances and are often manually or automatically 778 assigned to VPNs as they are provisioned. 780 Thus the RD provides a useful way to indicate that traffic for a 781 particular VPN should be placed on a given tunnel. The tunnel head 782 end will need to interpret this Flow Specification not as a filter on 783 the fields of data packets, but using the other mechanisms that it 784 already uses to identify VPN traffic. This could be based on the 785 incoming port (for port-based VPNs) or may leverage knowledge of the 786 VRF that is in use for the traffic. 788 8.7. Priorities and Overlapping Flow Specifications 790 Flow specifications can overlap. For example, two different flow 791 specifications may be identical except for the length of the prefix 792 in the destination address. In these cases the PCC must determine 793 how to prioritize the flow specifications so as to know to which path 794 to assign packets that match both flow specifications. That is, the 795 PCC must assign a precedence to the flow specifications so that it 796 checks each incoming packet for a match in a predictable order. 798 The processing of BGP Flow Specifications is described in 799 [I-D.ietf-idr-rfc5575bis]. Section 5.1 of that document explains the 800 order of traffic filtering rules to be executed by an implementation 801 of that specification. 803 PCCs MUST apply the same ordering rules as defined in 804 [I-D.ietf-idr-rfc5575bis]. 806 Furthermore, it is possible that Flow Specifications will be 807 distributed by BGP as well as by PCEP as described in this document. 808 In such cases implementations supporting both approaches MUST apply 809 the prioritization and ordering rules as set out in 810 [I-D.ietf-idr-rfc5575bis] regardless of which protocol distributed 811 the Flow Specifications, however implementations MAY provide a 812 configuration control to allow one protocol to take precedence over 813 the other as this may be particularly useful if the Flow 814 Specification make identical matches on traffic but have different 815 actions. It is RECOMMENDED that when two Flow Specifications 816 distributed by different protocols overlap, and especially when one 817 acts to replace another, that a message be logged for the operator to 818 understand the behaviour. 820 Section 13.1 of this document covers manageability considerations 821 relevant to the prioritized ordering of flow specifications. 823 An implementation that receives a PCEP message carrying a Flow 824 Specification that it cannot resolve against other Flow 825 Specifications already installed MUST respond with a PCErr message 826 with error-type TBD8 (FlowSpec Error), error-value 3 (Unresolvable 827 Conflict) and MUST NOT install the Flow Specification. 829 9. PCEP Messages 831 This section describes the format of messages that contain FLOWSPEC 832 objects. The only difference to previous message formats is the 833 inclusion of that object. 835 The figures in this section use the notation defined in [RFC5511]. 837 The FLOWSPEC object is OPTIONAL and MAY be carried in the PCEP 838 messages. 840 The PCInitiate message is defined in [RFC8281] and updated as below: 842 ::= 843 845 Where: 846 ::= 847 [] 849 ::= 850 ( | 851 ) 853 ::= 854 855 [] 856 857 [] 858 [] 860 Where: 861 ::= [] 863 The PCUpd message is defined in [RFC8231] and updated as below: 865 ::= 866 868 Where: 869 ::= 870 [] 872 ::= 873 874 875 [] 877 Where: 878 ::= 880 ::= [] 882 The PCRpt message is defined in [RFC8231] and updated as below: 884 ::= 885 887 Where: 888 ::= [] 890 ::= [] 891 892 893 [] 895 Where: 896 ::= 897 [] 898 900 ::= [] 902 The PCReq message is defined in [RFC5440] and updated in [RFC8231], 903 it is further updated below for flow specification: 905 ::= 906 [] 907 909 Where: 910 ::= [] 912 ::= [] 914 ::= 915 916 [] 917 [] 918 [] 919 [] 920 [[]] 921 [] 922 [] 923 [] 925 Where: 926 ::= [] 928 The PCRep message is defined in [RFC5440] and updated in [RFC8231], 929 it is further updated below for flow specification: 931 ::= 932 934 Where: 935 ::=[] 937 ::= 938 [] 939 [] 940 [] 941 [] 942 [] 944 Where: 945 ::= [] 947 10. IANA Considerations 949 IANA maintains the "Path Computation Element Protocol (PCEP) Numbers" 950 registry. This document requests IANA actions to allocate code 951 points for the protocol elements defined in this document. 953 10.1. PCEP Objects 955 Each PCEP object has an Object-Class and an Object-Type. IANA 956 maintains a subregistry called "PCEP Objects". IANA is requested to 957 make an assignment from this subregistry as follows: 959 Object-Class | Value Name | Object-Type | Reference 960 -------------+-------------+------------------------+---------------- 961 TBD3 | FLOWSPEC | 0: Reserved | [This.I-D] 962 | | 1: Flow Specification | [This.I-D] 964 10.1.1. PCEP FLOWSPEC Object Flag Field 966 This document requests that a new sub-registry, named "FLOWSPEC 967 Object Flag Field", is created within the "Path Computation Element 968 Protocol (PCEP) Numbers" registry to manage the Flag field of the 969 FLOWSPEC object. New values are to be assigned by Standards Action 970 [RFC8126]. Each bit should be tracked with the following qualities: 972 o Bit number (counting from bit 0 as the most significant bit) 974 o Capability description 976 o Defining RFC 978 The initial population of this registry is as follows: 980 Bit | Description | Reference 981 -----+--------------------+------------- 982 0-5 | Unnassigned | 983 6 | LPM (L bit) | [This.I-D] 984 7 | Remove (R bit) | [This.I-D] 986 10.2. PCEP TLV Type Indicators 988 IANA maintains a subregistry called "PCEP TLV Type Indicators". IANA 989 is requested to make an assignment from this subregistry as follows: 991 Value | Meaning | Reference 992 --------+------------------------------+------------- 993 TBD2 | PCE-FLOWSPEC-CAPABILITY TLV | [This.I-D] 994 TBD4 | FLOW FILTER TLV | [This.I-D] 996 10.3. Flow Specification TLV Type Indicators 998 IANA is requested to create a new subregistry call the "PCEP Flow 999 Specification TLV Type Indicators" registry. 1001 Allocations from this registry are to be made according to the 1002 following assignment policies [RFC8126]: 1004 Range | Assignment policy 1005 ---------------+--------------------------------------------------- 1006 0 | Reserved - must not be allocated. 1007 | 1008 1 .. 255 | Reserved - must not be allocated. 1009 | Usage mirrors the BGP FlowSpec registry 1010 | [I-D.ietf-idr-rfc5575bis] and 1011 | [I-D.ietf-idr-flow-spec-v6]. 1012 | 1013 256 .. 64506 | Specification Required 1014 | 1015 64507 .. 65531 | First Come First Served 1016 | 1017 65532 .. 65535 | Experimental 1019 IANA is requested to pre-populate this registry with values defined 1020 in this document as follows, taking the new values from the range 256 1021 to 64506: 1023 Value | Meaning 1024 -------+------------------------ 1025 TBD5 | Route Distinguisher 1026 TBD6 | IPv4 Multicast 1027 TBD7 | IPv6 Multicast 1029 10.4. PCEP Error Codes 1031 IANA maintains a subregistry called "PCEP-ERROR Object Error Types 1032 and Values". Entries in this subregistry are described by Error-Type 1033 and Error-value. IANA is requested to make the following assignment 1034 from this subregistry: 1036 Error-| Meaning | Error-value | Reference 1037 Type | | | 1038 -------+--------------------+----------------------------+----------- 1039 TBD8 | FlowSpec error | 0: Unassigned | [This.I-D] 1040 | | 1: Unsupported FlowSpec | [This.I-D] 1041 | | 2: Malformed FlowSpec | [This.I-D] 1042 | | 3: Unresolvable Conflict | [This.I-D] 1043 | | 4: Unknown FlowSpec | [This.I-D] 1044 | | 5: Unsupported LPM Route | [This.I-D] 1045 | | 6-255: Unassigned | [This.I-D] 1047 10.5. PCE Capability Flag 1049 IANA maintains a subregistry called "Open Shortest Path First v2 1050 (OSPFv2) Parameters" with a sub-registry called "Path Computation 1051 Element (PCE) Capability Flags". IANA is requested to assign a new 1052 capability bit from this registry as follows: 1054 Bit | Capability Description | Reference 1055 -------+-------------------------------+------------ 1056 TBD1 | FlowSpec | [This.I-D] 1058 11. Implementation Status 1060 [NOTE TO RFC EDITOR : This whole section and the reference to RFC 1061 7942 is to be removed before publication as an RFC] 1063 This section records the status of known implementations of the 1064 protocol defined by this specification at the time of posting of this 1065 Internet-Draft, and is based on a proposal described in [RFC7942]. 1066 The description of implementations in this section is intended to 1067 assist the IETF in its decision processes in progressing drafts to 1068 RFCs. Please note that the listing of any individual implementation 1069 here does not imply endorsement by the IETF. Furthermore, no effort 1070 has been spent to verify the information presented here that was 1071 supplied by IETF contributors. This is not intended as, and must not 1072 be construed to be, a catalog of available implementations or their 1073 features. Readers are advised to note that other implementations may 1074 exist. 1076 According to [RFC7942], "this will allow reviewers and working groups 1077 to assign due consideration to documents that have the benefit of 1078 running code, which may serve as evidence of valuable experimentation 1079 and feedback that have made the implemented protocols more mature. 1080 It is up to the individual working groups to use this information as 1081 they see fit". 1083 At the time of posting the -04 version of this document, there are no 1084 known implementations of this mechanism. It is believed that two 1085 vendors are considering prototype implementations, but these plans 1086 are too vague to make any further assertions. 1088 12. Security Considerations 1090 We may assume that a system that utilizes a remote PCE is subject to 1091 a number of vulnerabilities that could allow spurious LSPs or SR 1092 paths to be established or that could result in existing paths being 1093 modified or torn down. Such systems, therefore, apply security 1094 considerations as described in [RFC5440], [RFC6952], and [RFC8253]. 1096 The description of Flow Specifications associated with paths set up 1097 or controlled by a PCE add a further detail that could be attacked 1098 without tearing down LSPs or SR paths, but causing traffic to be 1099 misrouted within the network. Therefore, the use of the security 1100 mechanisms for PCEP referenced above is important. 1102 Visibility into the information carried in PCEP does not have direct 1103 privacy concerns for end-users' data, however, knowledge of how data 1104 is routed in a network may make that data more vulnerable. Of 1105 course, the ability to interfere with the way data is routed also 1106 makes the data more vulnerable. Furthermore, knowledge of the 1107 connected end-points (such as multicast receivers or VPN sites) is 1108 usually considered private customer information. Therefore, 1109 implementations or deployments concerned with protecting privacy MUST 1110 apply the mechanisms described in the documents referenced above. 1112 Experience with Flow Specifications in BGP systems indicates that 1113 they can become complex and that the overlap of Flow Specifications 1114 installed in different orders can lead to unexpected results. 1115 Although this is not directly a security issue per se, the confusion 1116 and unexpected forwarding behavior may be engineered or exploited by 1117 an attacker. Therefore, implementers and operators SHOULD pay 1118 careful attention to the Manageability Considerations described in 1119 Section 13. 1121 13. Manageability Considerations 1123 The feature introduced by this document enables operational 1124 manageability of networks operated in conjunction with a PCE and 1125 using PCEP. Without this feature, but in the case of a stateful 1126 active PCE or with PCE-initiated services, additional manual 1127 configuration is needed to tell the head-ends what traffic to place 1128 on the network services (LSPs, SR paths, etc.). 1130 This section follows the advice and guidance of [RFC6123]. 1132 13.1. Management of Multiple Flow Specifications 1134 Experience with flow specification in BGP suggests that there can be 1135 a lot of complexity when two or more flow specifications overlap. 1136 This can arise, for example, with addresses indicated using prefixes, 1137 and could cause confusion about what traffic should be placed on 1138 which path. Unlike the behavior in a distributed routing system, it 1139 is not important that each head-end implementation applies the same 1140 rules to disambiguate overlapping Flow Specifications, but it is 1141 important that: 1143 o A network operator can easily find out what traffic is being 1144 placed on which path and why. This will facilitate analysis of 1145 the network and diagnosis of faults. 1147 o A PCE is able to correctly predict the effect of instructions it 1148 gives to a PCC. 1150 To that end, a PCC MUST enable an operator to view the the Flow 1151 Specifications that it has installed, and these MUST be presented in 1152 order of precedence such that when two Flow Specifications overlap, 1153 the one that will be serviced with higher precedence is presented to 1154 the operator first. 1156 A discussion of precedence ordering for flow specifications is found 1157 in Section 8.7. 1159 13.2. Control of Function through Configuration and Policy 1161 Support for the function described in this document implies that a 1162 functional element that is capable of requesting a PCE to compute and 1163 control a path is also able to configure the specification of what 1164 traffic should be placed on that path. Where there is a human 1165 involved in this action, configuration of the Flow Specification must 1166 be available through an interface (such as a graphical user interface 1167 or a command line interface). Where a distinct software component 1168 (i.e., one not co-implemented with the PCE) is used, a protocol 1169 mechanism will be required that could be PCEP itself or could be a 1170 data model such as extensions to the YANG model for requesting path 1171 computation [I-D.ietf-teas-yang-path-computation]. 1173 Implementations MAY be constructed with a configurable switch to say 1174 whether they support the functions defined in this document. 1175 Otherwise, such implementations MUST indicate that they support the 1176 function as described in Section 4. If an implementation supports 1177 configurable support of this function, that support MAY be 1178 configurable per peer or once for the whole implementation. 1180 As mentioned in Section 13.1, a PCE implementation SHOULD provide a 1181 mechanism to configure variations in the precedence ordering of Flow 1182 Specifications per PCC. 1184 13.3. Information and Data Models 1186 The YANG model in [I-D.ietf-pce-pcep-yang] can be used to model and 1187 monitor PCEP states and messages. To make that YANG model useful for 1188 the extensions described in this document, it will need to be 1189 augmented to cover the new protocol elements. 1191 Similarly, as noted in Section 13.2, the YANG model defined in 1192 [I-D.ietf-teas-yang-path-computation] could be extended to allow 1193 specification of Flow Specifications. 1195 Finally, as mentioned in Section 13.1, a PCC implementation SHOULD 1196 provide a mechanism to allow an operator to read the Flow 1197 Specifications from a PCC and to understand in what order they will 1198 be executed. This could be achieved using a new YANG model. 1200 13.4. Liveness Detection and Monitoring 1202 The extensions defined in this document do not require any additional 1203 liveness detection and monitoring support. See [RFC5440] and 1204 [RFC5886] for more information. 1206 13.5. Verifying Correct Operation 1208 The chief element of operation that needs to be verified (in addition 1209 to the operation of the protocol elements as described in [RFC5440]) 1210 is the installation, precedence, and correct operation of the Flow 1211 Specifications at a PCC. 1213 In addition to the YANG model for reading Flow Specifications 1214 described in Section 13.3, tools may be needed to inject Operations 1215 and Management (OAM) traffic at the PCC that matches specific 1216 criteria so that it can be monitored as traveling along the desired 1217 path. Such tools are outside the scope of this document. 1219 13.6. Requirements on Other Protocols and Functional Components 1221 This document places no requirements on other protocols or 1222 components. 1224 13.7. Impact on Network Operation 1226 The use of the features described in this document clearly have an 1227 important impact on network traffic since they cause traffic to be 1228 routed on specific paths in the network. However, in practice, these 1229 changes make no direct changes to the network operation because 1230 traffic is already placed on those paths using some pre-existing 1231 configuration mechanism. Thus, the significant change is the 1232 reduction in mechanisms that have to be applied, rather than a change 1233 to how the traffic is passed through the network. 1235 13.8. Other Considerations 1237 No other manageability considerations are known at this time. 1239 14. Acknowledgements 1241 Thanks to Julian Lucek, Sudhir Cheruathur, Olivier Dugeon, Jayant 1242 Agarwal, Jeffrey Zhang, Acee Lindem, and Vishnu Payam Beeram for 1243 useful discussions. 1245 15. References 1247 15.1. Normative References 1249 [I-D.ietf-idr-flow-spec-v6] 1250 Loibl, C., Raszuk, R., and S. Hares, "Dissemination of 1251 Flow Specification Rules for IPv6", draft-ietf-idr-flow- 1252 spec-v6-11 (work in progress), April 2020. 1254 [I-D.ietf-idr-rfc5575bis] 1255 Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M. 1256 Bacher, "Dissemination of Flow Specification Rules", 1257 draft-ietf-idr-rfc5575bis-25 (work in progress), May 2020. 1259 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1260 Requirement Levels", BCP 14, RFC 2119, 1261 DOI 10.17487/RFC2119, March 1997, 1262 . 1264 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 1265 "Multiprotocol Extensions for BGP-4", RFC 4760, 1266 DOI 10.17487/RFC4760, January 2007, 1267 . 1269 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1270 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1271 DOI 10.17487/RFC5440, March 2009, 1272 . 1274 [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax 1275 Used to Form Encoding Rules in Various Routing Protocol 1276 Specifications", RFC 5511, DOI 10.17487/RFC5511, April 1277 2009, . 1279 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1280 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1281 May 2017, . 1283 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 1284 "PCEPS: Usage of TLS to Provide a Secure Transport for the 1285 Path Computation Element Communication Protocol (PCEP)", 1286 RFC 8253, DOI 10.17487/RFC8253, October 2017, 1287 . 1289 15.2. Informative References 1291 [I-D.ietf-idr-flowspec-l2vpn] 1292 Weiguo, H., Eastlake, D., Litkowski, S., and S. Zhuang, 1293 "BGP Dissemination of L2 Flow Specification Rules", draft- 1294 ietf-idr-flowspec-l2vpn-15 (work in progress), May 2020. 1296 [I-D.ietf-pce-pcep-yang] 1297 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1298 YANG Data Model for Path Computation Element 1299 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1300 yang-13 (work in progress), October 2019. 1302 [I-D.ietf-teas-yang-path-computation] 1303 Busi, I., Belotti, S., Lopezalvarez, V., Sharma, A., and 1304 Y. Shi, "Yang model for requesting Path Computation", 1305 draft-ietf-teas-yang-path-computation-08 (work in 1306 progress), December 2019. 1308 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 1309 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 1310 2006, . 1312 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1313 Element (PCE)-Based Architecture", RFC 4655, 1314 DOI 10.17487/RFC4655, August 2006, 1315 . 1317 [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. 1318 Zhang, "OSPF Protocol Extensions for Path Computation 1319 Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088, 1320 January 2008, . 1322 [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. 1323 Zhang, "IS-IS Protocol Extensions for Path Computation 1324 Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089, 1325 January 2008, . 1327 [RFC5886] Vasseur, JP., Ed., Le Roux, JL., and Y. Ikejiri, "A Set of 1328 Monitoring Tools for Path Computation Element (PCE)-Based 1329 Architecture", RFC 5886, DOI 10.17487/RFC5886, June 2010, 1330 . 1332 [RFC6123] Farrel, A., "Inclusion of Manageability Sections in Path 1333 Computation Element (PCE) Working Group Drafts", RFC 6123, 1334 DOI 10.17487/RFC6123, February 2011, 1335 . 1337 [RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of 1338 BGP, LDP, PCEP, and MSDP Issues According to the Keying 1339 and Authentication for Routing Protocols (KARP) Design 1340 Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013, 1341 . 1343 [RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path 1344 Computation Element Architecture", RFC 7399, 1345 DOI 10.17487/RFC7399, October 2014, 1346 . 1348 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1349 Code: The Implementation Status Section", BCP 205, 1350 RFC 7942, DOI 10.17487/RFC7942, July 2016, 1351 . 1353 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1354 Writing an IANA Considerations Section in RFCs", BCP 26, 1355 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1356 . 1358 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 1359 Computation Element Communication Protocol (PCEP) 1360 Extensions for Stateful PCE", RFC 8231, 1361 DOI 10.17487/RFC8231, September 2017, 1362 . 1364 [RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 1365 and D. Dhody, "Optimizations of Label Switched Path State 1366 Synchronization Procedures for a Stateful PCE", RFC 8232, 1367 DOI 10.17487/RFC8232, September 2017, 1368 . 1370 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 1371 Computation Element Communication Protocol (PCEP) 1372 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 1373 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 1374 . 1376 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 1377 Architecture for Use of PCE and the PCE Communication 1378 Protocol (PCEP) in a Network with Central Control", 1379 RFC 8283, DOI 10.17487/RFC8283, December 2017, 1380 . 1382 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 1383 and J. Hardwick, "Path Computation Element Communication 1384 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 1385 DOI 10.17487/RFC8664, December 2019, 1386 . 1388 Appendix A. Contributors 1390 Shankara 1391 Huawei Technologies 1392 Divyashree Techno Park, 1393 Whitefield Bangalore, 1394 Karnataka 1395 560066 1396 India 1398 Email: shankara@huawei.com 1400 Qiandeng Liang 1401 Huawei Technologies 1402 101 Software Avenue, 1403 Yuhuatai District 1404 Nanjing 1405 210012 1406 China 1408 Email: liangqiandeng@huawei.com 1410 Cyril Margaria 1411 Juniper Networks 1412 200 Somerset Corporate Boulevard, Suite 4001 1413 Bridgewater, NJ 1414 08807 1415 USA 1417 Email: cmargaria@juniper.net 1419 Colby Barth 1420 Juniper Networks 1421 200 Somerset Corporate Boulevard, Suite 4001 1422 Bridgewater, NJ 1423 08807 1424 USA 1426 Email: cbarth@juniper.net 1428 Xia Chen 1429 Huawei Technologies 1430 Huawei Bld., No.156 Beiqing Rd. 1431 Beijing 1432 100095 1433 China 1435 Email: jescia.chenxia@huawei.com 1437 Shunwan Zhuang 1438 Huawei Technologies 1439 Huawei Bld., No.156 Beiqing Rd. 1440 Beijing 1441 100095 1442 China 1444 Email: zhuangshunwan@huawei.com 1446 Cheng Li 1447 Huawei Technologies 1448 Huawei Campus, No. 156 Beiqing Rd. 1449 Beijing 100095 1450 China 1452 Email: chengli13@huawei.com 1454 Authors' Addresses 1456 Dhruv Dhody 1457 Huawei Technologies 1458 Divyashree Techno Park, Whitefield 1459 Bangalore, Karnataka 560066 1460 India 1462 Email: dhruv.ietf@gmail.com 1464 Adrian Farrel 1465 Old Dog Consulting 1467 Email: adrian@olddog.co.uk 1468 Zhenbin Li 1469 Huawei Technologies 1470 Huawei Bld., No.156 Beiqing Rd. 1471 Beijing 100095 1472 China 1474 Email: lizhenbin@huawei.com