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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group Z. Li 3 Internet-Draft S. Peng 4 Intended status: Standards Track Huawei Technologies 5 Expires: June 18, 2021 M. Negi 6 RtBrick Inc 7 Q. Zhao 8 Etheric Networks 9 C. Zhou 10 HPE 11 December 15, 2020 13 PCEP Procedures and Protocol Extensions for Using PCE as a Central 14 Controller (PCECC) for Segment Routing (SR) MPLS Segment Identifier 15 (SID) Allocation and Distribution. 16 draft-ietf-pce-pcep-extension-pce-controller-sr-00 18 Abstract 20 The Path Computation Element (PCE) is a core component of Software- 21 Defined Networking (SDN) systems. It can compute optimal paths for 22 traffic across a network and can also update the paths to reflect 23 changes in the network or traffic demands. 25 PCE was developed to derive paths for MPLS Label Switched Paths 26 (LSPs), which are supplied to the head end of the LSP using the Path 27 Computation Element Communication Protocol (PCEP). But SDN has a 28 broader applicability than signaled (G)MPLS traffic-engineered (TE) 29 networks, and the PCE may be used to determine paths in a range of 30 use cases. PCEP has been proposed as a control protocol for use in 31 these environments to allow the PCE to be fully enabled as a central 32 controller. 34 A PCE-based Central Controller (PCECC) can simplify the processing of 35 a distributed control plane by blending it with elements of SDN and 36 without necessarily completely replacing it. Thus, the LSP can be 37 calculated/set up/initiated and the label forwarding entries can also 38 be downloaded through a centralized PCE server to each network device 39 along the path while leveraging the existing PCE technologies as much 40 as possible. 42 This document specifies the procedures and PCEP extensions when a 43 PCE-based controller is also responsible for configuring the 44 forwarding actions on the routers, in addition to computing the paths 45 for packet flows in a segment routing (SR) network and telling the 46 edge routers what instructions to attach to packets as they enter the 47 network. PCECC is further enhanced for SR SID (Segment Identifier) 48 allocation and distribution. 50 Status of This Memo 52 This Internet-Draft is submitted in full conformance with the 53 provisions of BCP 78 and BCP 79. 55 Internet-Drafts are working documents of the Internet Engineering 56 Task Force (IETF). Note that other groups may also distribute 57 working documents as Internet-Drafts. The list of current Internet- 58 Drafts is at https://datatracker.ietf.org/drafts/current/. 60 Internet-Drafts are draft documents valid for a maximum of six months 61 and may be updated, replaced, or obsoleted by other documents at any 62 time. It is inappropriate to use Internet-Drafts as reference 63 material or to cite them other than as "work in progress." 65 This Internet-Draft will expire on June 18, 2021. 67 Copyright Notice 69 Copyright (c) 2020 IETF Trust and the persons identified as the 70 document authors. All rights reserved. 72 This document is subject to BCP 78 and the IETF Trust's Legal 73 Provisions Relating to IETF Documents 74 (https://trustee.ietf.org/license-info) in effect on the date of 75 publication of this document. Please review these documents 76 carefully, as they describe your rights and restrictions with respect 77 to this document. Code Components extracted from this document must 78 include Simplified BSD License text as described in Section 4.e of 79 the Trust Legal Provisions and are provided without warranty as 80 described in the Simplified BSD License. 82 Table of Contents 84 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 85 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 86 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 87 3. PCECC SR . . . . . . . . . . . . . . . . . . . . . . . . . . 5 88 4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 6 89 5. Procedures for Using the PCE as a Central Controller (PCECC) 90 in Segment Routing . . . . . . . . . . . . . . . . . . . . . 6 91 5.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 6 92 5.2. New LSP Functions . . . . . . . . . . . . . . . . . . . . 6 93 5.3. PCECC Capability Advertisement . . . . . . . . . . . . . 7 94 5.4. PCEP session IP address and TED Router ID . . . . . . . . 7 95 5.5. LSP Operations . . . . . . . . . . . . . . . . . . . . . 8 96 5.5.1. PCECC Segment Routing (SR) . . . . . . . . . . . . . 8 97 5.5.1.1. PCECC SR Node/Prefix SID allocation . . . . . . . 8 98 5.5.1.2. PCECC SR Adjacency Label allocation . . . . . . . 10 99 5.5.1.3. Redundant PCEs . . . . . . . . . . . . . . . . . 12 100 5.5.1.4. Re Delegation and Clean up . . . . . . . . . . . 12 101 5.5.1.5. Synchronization of Label Allocations . . . . . . 13 102 5.5.1.6. PCC-Based Allocations . . . . . . . . . . . . . . 13 103 5.5.1.7. Binding SID . . . . . . . . . . . . . . . . . . . 13 104 6. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . . 14 105 6.1. Central Control Instructions . . . . . . . . . . . . . . 14 106 6.1.1. The PCInitiate Message . . . . . . . . . . . . . . . 14 107 6.1.2. The PCRpt message . . . . . . . . . . . . . . . . . . 15 108 7. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . . 16 109 7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 16 110 7.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 16 111 7.2. SR-TE Path Setup . . . . . . . . . . . . . . . . . . . . 17 112 7.3. CCI Object . . . . . . . . . . . . . . . . . . . . . . . 17 113 7.4. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 19 114 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 21 115 8.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 22 116 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22 117 10. Manageability Considerations . . . . . . . . . . . . . . . . 22 118 10.1. Control of Function and Policy . . . . . . . . . . . . . 22 119 10.2. Information and Data Models . . . . . . . . . . . . . . 23 120 10.3. Liveness Detection and Monitoring . . . . . . . . . . . 23 121 10.4. Verify Correct Operations . . . . . . . . . . . . . . . 23 122 10.5. Requirements On Other Protocols . . . . . . . . . . . . 23 123 10.6. Impact On Network Operations . . . . . . . . . . . . . . 23 124 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 125 11.1. PCECC-CAPABILITY sub-TLV . . . . . . . . . . . . . . . . 23 126 11.2. PCEP Object . . . . . . . . . . . . . . . . . . . . . . 24 127 11.3. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 24 128 11.4. CCI Object Flag Field for SR . . . . . . . . . . . . . . 24 129 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 130 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 131 13.1. Normative References . . . . . . . . . . . . . . . . . . 25 132 13.2. Informative References . . . . . . . . . . . . . . . . . 27 133 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 30 134 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31 136 1. Introduction 138 The Path Computation Element (PCE) [RFC4655] was developed to offload 139 the path computation function from routers in an MPLS traffic- 140 engineered network. Since then, the role and function of the PCE has 141 grown to cover a number of other uses (such as GMPLS [RFC7025]) and 142 to allow delegated control [RFC8231] and PCE-initiated use of network 143 resources [RFC8281]. 145 According to [RFC7399], Software-Defined Networking (SDN) refers to a 146 separation between the control elements and the forwarding components 147 so that software running in a centralized system, called a 148 controller, can act to program the devices in the network to behave 149 in specific ways. A required element in an SDN architecture is a 150 component that plans how the network resources will be used and how 151 the devices will be programmed. It is possible to view this 152 component as performing specific computations to place traffic flows 153 within the network given knowledge of the availability of network 154 resources, how other forwarding devices are programmed, and the way 155 that other flows are routed. This is the function and purpose of a 156 PCE, and the way that a PCE integrates into a wider network control 157 system (including an SDN system) is presented in [RFC7491]. 159 In early PCE implementations, where the PCE was used to derive paths 160 for MPLS Label Switched Paths (LSPs), paths were requested by network 161 elements (known as Path Computation Clients (PCCs)), and the results 162 of the path computations were supplied to network elements using the 163 Path Computation Element Communication Protocol (PCEP) [RFC5440]. 164 This protocol was later extended to allow a PCE to send unsolicited 165 requests to the network for LSP establishment [RFC8281]. 167 [RFC8283] introduces the architecture for PCE as a central controller 168 as an extension of the architecture described in [RFC4655] and 169 assumes the continued use of PCEP as the protocol used between PCE 170 and PCC. [RFC8283] further examines the motivations and 171 applicability for PCEP as a Southbound Interface (SBI), and 172 introduces the implications for the protocol. 173 [I-D.ietf-teas-pcecc-use-cases] describes the use cases for the PCE- 174 based Central Controller (PCECC) architecture. 176 [I-D.ietf-pce-pcep-extension-for-pce-controller] specify the 177 procedures and PCEP extensions for using the PCE as the central 178 controller for static LSPs, where LSPs can be provisioned as explicit 179 label instructions at each hop on the end-to-end path. 181 Segment Routing (SR) technology leverages the source routing and 182 tunneling paradigms. A source node can choose a path without relying 183 on hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path 184 is specified as a set of "segments" advertised by link-state routing 185 protocols (IS-IS or OSPF). [RFC8402] provides an introduction to SR 186 architecture. The corresponding IS-IS and OSPF extensions are 187 specified in [RFC8667] and [RFC8665] , respectively. It relies on a 188 series of forwarding instructions being placed in the header of a 189 packet. The segment routing architecture supports operations that 190 can be used to steer packet flows in a network, thus providing a form 191 of traffic engineering. [RFC8664] specify the SR specific PCEP 192 extensions. 194 PCECC may further use PCEP for SR SID (Segment Identifier) allocation 195 and distribution on the SR nodes with some benefits. 197 This document specifies the procedures and PCEP extensions when a 198 PCE-based controller is also responsible for configuring the 199 forwarding actions on the routers (SR SID allocation and distribution 200 in this case), in addition to computing the paths for packet flows in 201 a segment routing network and telling the edge routers what 202 instructions to attach to packets as they enter the network. 204 Only SR using MPLS dataplane (SR-MPLS) is in the scope of this 205 document. Refer [I-D.dhody-pce-pcep-extension-pce-controller-srv6] 206 for use of PCECC technique for SR in IPv6 (SRv6) dataplane. 208 1.1. Requirements Language 210 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 211 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 212 "OPTIONAL" in this document are to be interpreted as described in BCP 213 14 [RFC2119] [RFC8174] when, and only when, they appear in all 214 capitals, as shown here. 216 2. Terminology 218 Terminologies used in this document is the same as described in the 219 draft [RFC8283] and [I-D.ietf-teas-pcecc-use-cases]. 221 3. PCECC SR 223 [RFC8664] specifies extensions to PCEP that allow a stateful PCE to 224 compute, update, or initiate SR-TE paths. An ingress node of an SR- 225 TE path appends all outgoing packets with a list of MPLS labels 226 (SIDs). This is encoded in SR-ERO subobject, capable of carrying a 227 label (SID) as well as the identity of the node/adjacency label 228 (SID). 230 The notion of segment and SID is defined in [RFC8402], which fits the 231 MPLS architecture [RFC3031] as the label which is managed by a local 232 allocation process of LSR (similarly to other MPLS signaling 233 protocols) [RFC8660]. The SR information such as node/adjacency 234 label (SID) is flooded via IGP as specified in [RFC8667] and 235 [RFC8665]. 237 As per [RFC8283], PCE as a central controller can allocate and 238 provision the node/prefix/adjacency label (SID) via PCEP. 240 The rest of the processing is similar to existing stateful PCE with 241 SR mechanism. 243 For the purpose of this document, it is assumed that the label range 244 to be used by a PCE is set on both PCEP peers. Further, a global 245 label range is assumed to be set on all PCEP peers in the SR domain. 246 This document also allows a case where the label space is maintained 247 by PCC itself, and the labels are allocated by the PCC, in this case, 248 the PCE should request the allocation from PCC as described in 249 Section 5.5.1.6. 251 4. PCEP Requirements 253 Following key requirements for PCECC-SR should be considered when` 254 designing the PCECC-based solution: 256 o A PCEP speaker supporting this draft needs to have the capability 257 to advertise its PCECC-SR capability to its peers. 259 o PCEP procedures need to allow for PCC-based label/SID allocations. 261 o PCEP procedures need means to update (or clean up) the label-map 262 entry to the PCC. 264 o PCEP procedures need to provide a mean to synchronize the SR 265 labels allocations between the PCE to the PCC via PCEP messages. 267 5. Procedures for Using the PCE as a Central Controller (PCECC) in 268 Segment Routing 270 5.1. Stateful PCE Model 272 Active stateful PCE is described in [RFC8231]. PCE as a Central 273 Controller (PCECC) reuses the existing active stateful PCE mechanism 274 as much as possible to control the LSPs. 276 5.2. New LSP Functions 278 Several new functions are required in PCEP to support PCECC as 279 described in [I-D.ietf-pce-pcep-extension-for-pce-controller]. This 280 document reuses the existing messages to support PCECC-SR. 282 The PCEP messages PCRpt, PCInitiate, PCUpd are used to send LSP 283 Reports, LSP setup, and LSP update respectively. The extended 284 PCInitiate message described in 285 [I-D.ietf-pce-pcep-extension-for-pce-controller] is used to download 286 or clean up central controller's instructions (CCIs) (SR SID in the 287 scope of this document). The extended PCRpt message described in 288 [I-D.ietf-pce-pcep-extension-for-pce-controller] is also used to 289 report the CCIs (SR SIDs) from PCC to PCE. 291 [I-D.ietf-pce-pcep-extension-for-pce-controller] specify an object 292 called CCI for the encoding of the central controller's instructions. 293 This document extends the CCI by defining a new object-type for 294 segment routing. The PCEP messages are extended in this document to 295 handle the PCECC operations for SR. 297 5.3. PCECC Capability Advertisement 299 During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) 300 advertise their support of PCECC extensions. A PCEP Speaker includes 301 the "PCECC Capability" sub-TLV, described in 302 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 304 A new S-bit is added in the PCECC-CAPABILITY sub-TLV to indicate 305 support for PCECC-SR. A PCC MUST set the S-bit in the PCECC- 306 CAPABILITY sub-TLV and include the SR-PCE-CAPABILITY sub-TLV 307 ([RFC8664]) in the OPEN Object (inside the PATH-SETUP-TYPE-CAPABILITY 308 TLV) to support the PCECC SR extensions defined in this document. If 309 the S-bit is set in the PCECC-CAPABILITY sub-TLV and the SR-PCE- 310 CAPABILITY sub-TLV is not advertised in the OPEN Object, PCE SHOULD 311 send a PCErr message with Error-Type=19 (Invalid Operation) and 312 Error-value=TBD4 (SR capability was not advertised) and terminate the 313 session. 315 The rest of the processing is as per 316 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 318 5.4. PCEP session IP address and TED Router ID 320 A PCE may construct its Traffic Engineering Database (TED) by 321 participating in the IGP ([RFC3630] and [RFC5305] for MPLS-TE; 322 [RFC4203] and [RFC5307] for GMPLS). An alternative is offered by 323 BGP-LS [RFC7752] and [I-D.dhodylee-pce-pcep-ls]. 325 A PCEP [RFC5440] speaker could use any local IP address while 326 creating a TCP session. It is important to link the session IP 327 address with the Router ID in TED for successful PCECC operations. 329 During PCEP Initialization Phase, the PCC SHOULD advertise the TE 330 mapping information by including the "Node Attributes TLV" 331 [I-D.dhodylee-pce-pcep-ls] with "IPv4/IPv6 Router-ID of Local Node", 332 in the OPEN Object for this purpose. [RFC7752] describes the usage 333 as auxiliary Router-IDs that the IGP might be using, e.g., for TE 334 purposes. If there are more than one auxiliary Router-ID of a given 335 type, then multiple TLVs are used to encode them. 337 If "IPv4/IPv6 Router-ID" TLV is not present, the TCP session IP 338 address is directly used for mapping purpose. 340 5.5. LSP Operations 342 [RFC8664] specify the PCEP extension to allow a stateful PCE to 343 compute and initiate SR-TE paths, as well as a PCC to request a path 344 subject to certain constraint(s) and optimization criteria in SR 345 networks. 347 The Path Setup Type for segment routing (PST=1) is used on the PCEP 348 session with the Ingress as per [RFC8664]. 350 5.5.1. PCECC Segment Routing (SR) 352 Segment Routing (SR) as described in [RFC8402] depends on "segments" 353 that are advertised by Interior Gateway Protocols (IGPs). The SR- 354 node allocates and advertises the SID (node, adj, etc) and flood them 355 via the IGP. This document proposes a new mechanism where PCE 356 allocates the SID (label/index/SID) centrally and uses PCEP to 357 advertise them. In some deployments, PCE (and PCEP) are better 358 suited than IGP because of the centralized nature of PCE and direct 359 TCP based PCEP sessions to the node. 361 5.5.1.1. PCECC SR Node/Prefix SID allocation 363 Each node (PCC) is allocated a node-SID by the PCECC. The PCECC 364 sends PCInitiate message to update the label map of each node to all 365 the nodes in the domain. The TE router ID is determined from the TED 366 or from "IPv4/IPv6 Router-ID" Sub-TLV [I-D.dhodylee-pce-pcep-ls], in 367 the OPEN Object Section 5.4. 369 It is RECOMMENDED that PCEP session with PCECC-SR capability to use a 370 different session IP address during TCP session establishment than 371 the node Router ID in TEDB, to make sure that the PCEP session does 372 not get impacted by the SR Node/Prefix Label maps (Section 5.4). 374 If a node (PCC) receives a PCInitiate message with a CCI encoding a 375 SID, out of the range set aside for the SR Global Block (SRGB), it 376 MUST send a PCErr message with Error-type=TBD (PCECC failure) and 377 Error-value=TBD (Label out of range) (defined in 378 [I-D.ietf-pce-pcep-extension-for-pce-controller]) and MUST include 379 the SRP object to specify the error is for the corresponding central 380 control instruction via the PCInitiate message. 382 On receiving the label map, each node (PCC) uses the local routing 383 information to determine the next-hop and download the label 384 forwarding instructions accordingly. The PCInitiate message in this 385 case does not use the LSP object but uses a new FEC object defined in 386 this document. 388 +---------+ +-------+ 389 |PCC | | PCE | 390 |192.0.2.3| +-------+ 391 +------| | | 392 | PCC +---------+ | 393 | 192.0.2.2| | | 394 +------| | | | 395 |PCC +----------+ | | 396 |192.0.2.1| | | | 397 +---------+ | | | 398 | | | | 399 |<--------PCInitiate,FEC=192.0.2.1------------------| Label Map 400 | | | CC-ID=X | update 401 |--------PCRpt,CC-ID=X----------------------------->| CCI 402 |Find | | | 403 |Nexthop|<--------PCInitiate,FEC=192.0.2.1----------| Label Map 404 |locally| | CC-ID=Y | update 405 | |-------PCRpt,CC-ID=Y---------------------->| CCI 406 | | | | 407 | | |<----PCInitiate,FEC=192.0.2.1------| Label Map 408 | | | CC-ID=Z | update 409 | | |-----PCRpt,CC-ID=Z---------------->| CCI 410 | | | | 412 The forwarding behavior and the end result is similar to IGP based 413 "Node-SID" in SR. Thus, from anywhere in the domain, it enforces the 414 ECMP-aware shortest-path forwarding of the packet towards the related 415 node as per [RFC8402]. 417 PCE relies on the Node/Prefix Label clean up using the same 418 PCInitiate message as per [RFC8281]. 420 The above example Figure 1 depicts the FEC and PCEP speakers that 421 uses IPv4 address. Similarly an IPv6 address (such as 2001:DB8::1) 422 can be used during PCEP session establishment in the FEC object as 423 described in this specification. 425 In the case where the label/SID allocation is made by the PCC itself 426 (see Section 5.5.1.6), the PCE could request an allocation to be made 427 by the PCC, and where the PCC would send a PCRpt with the allocated 428 label/SID encoded in the CC-ID object as shown in Figure 2. 430 +---------+ +-------+ 431 |PCC | | PCE | 432 |192.0.2.3| +-------+ 433 +------| | | 434 | PCC +---------+ | 435 | 192.0.2.2| | | 436 +------| | | | 437 |PCC +----------+ | | 438 |192.0.2.1| | | | 439 +---------+ | | | 440 | | | | 441 |<--------PCInitiate,FEC=192.0.2.1------------------| Label Map 442 | | | CC-ID=X,C=1 | request 443 |--------PCRpt,CC-ID=X,Label----------------------->| CCI 444 |Find | | | 445 |Nexthop|<--------PCInitiate,FEC=192.0.2.1----------| Label Map 446 |locally| | CC-ID=Y,C=0,Label | update 447 | |-------PCRpt,CC-ID=Y---------------------->| CCI 448 | | | | 449 | | |<----PCInitiate,FEC=192.0.2.1------| Label Map 450 | | | CC-ID=Z,C=0,Label | update 451 | | |-----PCRpt,CC-ID=Z---------------->| CCI 452 | | | | 454 It should be noted that in this example, the request is made to the 455 node 192.0.2.1 with C bit set in the CCI object to indicate that the 456 allocation needs to be done by this PCC and it responds with the 457 allocated label/SID to the PCE. The PCE would further inform the 458 other PCCs in the network about the label-map allocation without 459 setting the C bit. 461 5.5.1.2. PCECC SR Adjacency Label allocation 463 For PCECC-SR, apart from node-SID, Adj-SID is used where each 464 adjacency is allocated an Adj-SID by the PCECC. The PCECC sends the 465 PCInitiate message to update the label map of each adjacency to the 466 corresponding nodes in the domain. Each node (PCC) download the 467 label forwarding instructions accordingly. Similar to SR Node/Prefix 468 Label allocation, the PCInitiate message in this case does not use 469 the LSP object but uses the new FEC object defined in this document. 471 +---------+ +-------+ 472 |PCC | | PCE | 473 |192.0.2.3| +-------+ 474 +------| | | 475 | PCC +---------+ | 476 | 192.0.2.2| | | 477 +------| | | | 478 |PCC +----------+ | | 479 |192.0.2.1| | | | 480 +---------+ | | | 481 | | | | 482 |<-------PCInitiate,FEC=198.51.100.1--------------| Label Map 483 | | | 198.51.100.2 | update 484 | | | CC-ID=A | CCI 485 |--------PCRpt,CC-ID=A--------------------------->| 486 | | | | 487 | |<------PCInitiate,FEC=198.51.100.2------| Label Map 488 | | | 198.51.100.1 | update 489 | | | CC-ID=B | CCI 490 | |-------PCRpt,CC-ID=B------------------->| 491 | | | | 493 The forwarding behavior and the end result is similar to IGP based 494 "Adj-SID" in SR. 496 PCE relies on the Adj label clean up using the same PCInitiate 497 message as per [RFC8281]. 499 The above example Figure 3 depicts FEC object and PCEP speakers that 500 uses an IPv4 address. Similarly an IPv6 address (such as 501 2001:DB8::1, 2001:DB8::2) can be used during the PCEP session 502 establishment in the FEC object as described in this specification. 504 The handling of adjacencies on the LAN subnetworks is specified in 505 [RFC8402]. PCECC MUST assign Adj-SID for every pair of routers in 506 the LAN. The rest of the protocol mechanism remains the same. 508 In the case where the label/SID map allocation is made by the PCC 509 itself (see Section 5.5.1.6), the PCE could request an allocation to 510 be made by the PCC, and where the PCC would send a PCRpt with the 511 allocated label/SID encoded in the CC-ID object as shown in Figure 4. 513 +---------+ +-------+ 514 |PCC | | PCE | 515 |192.0.2.3| +-------+ 516 +------| | | 517 | PCC +---------+ | 518 | 192.0.2.2| | | 519 +------| | | | 520 |PCC +----------+ | | 521 |192.0.2.1| | | | 522 +---------+ | | | 523 | | | | 524 |<-------PCInitiate,FEC=198.51.100.1--------------| Label Map 525 | | | 198.51.100.2 | request 526 | | | CC-ID=A,C=1 | CCI 527 |--------PCRpt,CC-ID=A,Label1-------------------->| 528 | | | | 529 | |<------PCInitiate,FEC=198.51.100.2------| Label Map 530 | | | 198.51.100.1 | request 531 | | | CC-ID=B,C=1 | CCI 532 | |-------PCRpt,CC-ID=B,Label2------------>| 533 | | | | 535 In this example, the request is made to the node 192.0.2.1 with the C 536 bit set in the CCI object to indicate that the allocation needs to be 537 done by this PCC for the adjacency (198.51.100.1 - 198.51.100.2) and 538 it responds with the allocated label/SID to the PCE. Similarly, 539 another request is made to the node 192.0.2.2 with the C bit set in 540 the CCI object to indicate that the allocation needs to be done by 541 this PCC for the adjacency (198.51.100.2 - 198.51.100.1). 543 5.5.1.3. Redundant PCEs 545 [I-D.litkowski-pce-state-sync] describes the synchronization 546 mechanism between the stateful PCEs. The SR SIDs allocated by a PCE 547 MUST also be synchronized among PCEs for PCECC SR state 548 synchronization. Note that the SR SIDs are independent of the SR-TE 549 LSPs, and remains intact till any topology change. The redundant 550 PCEs MUST have a common view of all SR SIDs allocated in the domain. 552 5.5.1.4. Re Delegation and Clean up 554 [I-D.ietf-pce-pcep-extension-for-pce-controller] describes the action 555 needed for CCIs for the static LSPs on a terminated session. Same 556 holds true for the CCI for SR SID as well. 558 5.5.1.5. Synchronization of Label Allocations 560 [I-D.ietf-pce-pcep-extension-for-pce-controller] describes the 561 synchronization of Central Controller's Instructions (CCI) via LSP 562 state synchronization as described in [RFC8231] and [RFC8232]. Same 563 procedures are applied for the CCI for SR SID as well. 565 5.5.1.6. PCC-Based Allocations 567 The PCE can request the PCC to allocate the label/SID using the 568 PCInitiate message. The C flag in the CCI object is set to 1 to 569 indicate that the allocation needs to be done by the PCC. The PCC 570 would allocate the SID/Label/Index and would report to the PCE using 571 the PCRpt message. 573 If the value of the SID/Label/Index is 0 and the C flag is set to 1, 574 it indicates that the PCE is requesting the allocation to be done by 575 the PCC. If the SID/Label/Index is 'n' and the C flag is set to 1 in 576 the CCI object, it indicates that the PCE requests a specific value 577 'n' for the SID/Label/Index. If the allocation is successful, the 578 PCC should report via PCRpt message with the CCI object. Else, it 579 MUST send a PCErr message with Error-Type = TBD ("PCECC failure") and 580 Error Value = TBD ("Invalid CCI") (defined in 581 [I-D.ietf-pce-pcep-extension-for-pce-controller]). If the value of 582 the SID/Label/Index in the CCI object is valid, but the PCC is unable 583 to allocate it, it MUST send a PCErr message with Error-Type = TBD 584 ("PCECC failure") and Error Value = TBD ("Unable to allocate the 585 specified CCI") (defined in 586 [I-D.ietf-pce-pcep-extension-for-pce-controller]). 588 If the PCC wishes to withdraw or modify the previously assigned 589 label/SID, it MUST send a PCRpt message without any SID/Label/Index 590 or with the SID/Label/Index containing the new value respectively in 591 the CCI object. The PCE would further trigger the removal of the 592 central controller instruction as per this document. 594 5.5.1.7. Binding SID 596 A PCECC can allocate and provision the node/prefix/adjacency label 597 (SID) via PCEP. Another SID called binding SID is described in 598 [I-D.ietf-pce-binding-label-sid], the PCECC mechanism can also be 599 used to allocate the binding SID. 601 A procedure for binding label/SID allocation is described in 602 [I-D.ietf-pce-pcep-extension-for-pce-controller] and is applicable 603 for all path setup types (including SR paths). 605 6. PCEP Messages 607 As defined in [RFC5440], a PCEP message consists of a common header 608 followed by a variable-length body made of a set of objects that can 609 be either mandatory or optional. An object is said to be mandatory 610 in a PCEP message when the object must be included for the message to 611 be considered valid. For each PCEP message type, a set of rules is 612 defined that specify the set of objects that the message can carry. 613 An implementation MUST form the PCEP messages using the object 614 ordering specified in this document. 616 6.1. Central Control Instructions 618 6.1.1. The PCInitiate Message 620 The PCInitiate message defined in [RFC8281] and extended in 621 [I-D.ietf-pce-pcep-extension-for-pce-controller] is further extended 622 to support SR based central control instructions. 624 The format of the extended PCInitiate message is as follows: 626 ::= 627 628 Where: 629 is defined in [RFC5440] 631 ::= 632 [] 634 ::= 635 (| 636 | 637 ) 639 ::= 640 ( 641 )| 642 ( 643 ) 645 ::= 646 [] 648 Where: 649 and 650 are as per 651 [RFC8281]. 653 The LSP and SRP object is defined in [RFC8231]. 655 When the PCInitiate message is used to distribute SR SIDs, the SRP, 656 the FEC and the CCI objects MUST be present. The error handling for 657 missing SRP or CCI object is as per 658 [I-D.ietf-pce-pcep-extension-for-pce-controller]. If the FEC object 659 is missing, the receiving PCC MUST send a PCErr message with Error- 660 type=6 (Mandatory Object missing) and Error-value=TBD5 (FEC object 661 missing). 663 To clean up, the R (remove) bit in the SRP object and the 664 corresponding FEC and the CCI object are included. 666 6.1.2. The PCRpt message 668 The PCRpt message can be used to report the SR central controller 669 instructions received from the PCECC during the state synchronization 670 phase or as an acknowledgment to the PCInitiate message. 672 The format of the PCRpt message is as follows: 674 ::= 675 676 Where: 678 ::= [] 680 ::= (| 681 ) 683 ::= [] 684 685 687 ::= [] 688 ( 689 )| 690 ( 691 ) 693 ::= 694 [] 696 Where: 697 is as per [RFC8231] and the LSP and SRP object are 698 also defined in [RFC8231]. 700 When PCRpt message is used to report the label map allocations, the 701 FEC and CCI objects MUST be present. The error handling for the 702 missing CCI object is as per 703 [I-D.ietf-pce-pcep-extension-for-pce-controller]. If the FEC object 704 is missing, the receiving PCE MUST send a PCErr message with Error- 705 type=6 (Mandatory Object missing) and Error-value=TBD5 (FEC object 706 missing). 708 7. PCEP Objects 710 7.1. OPEN Object 712 7.1.1. PCECC Capability sub-TLV 714 [I-D.ietf-pce-pcep-extension-for-pce-controller] defined the PCECC- 715 CAPABILITY sub-TLV. 717 A new S-bit is defined in PCECC-CAPABILITY sub-TLV for PCECC-SR: 719 0 1 2 3 720 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 1 721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 722 | Type=TBD | Length=4 | 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 724 | Flags |S|L| 725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 [Editor's Note - The above figure is included for ease of the reader 728 but should be removed before publication.] 730 S (PCECC-SR-CAPABILITY - 1 bit - TBD1): If set to 1 by a PCEP 731 speaker, it indicates that the PCEP speaker is capable of PCECC-SR 732 capability and the PCE allocates the Node and Adj label/SID on this 733 session. 735 7.2. SR-TE Path Setup 737 The PATH-SETUP-TYPE TLV is defined in [RFC8408]. A PST value of 1 is 738 used when Path is setup via SR mode as per [RFC8664]. The procedure 739 for SR-TE path setup as specified in [RFC8664] remians unchanged. 741 7.3. CCI Object 743 The Central Control Instructions (CCI) Object used by the PCE to 744 specify the controller instructions is defined in 745 [I-D.ietf-pce-pcep-extension-for-pce-controller]. This document 746 defines another object-type for SR-MPLS purpose. 748 CCI Object-Type is TBD6 for SR-MPLS as below - 750 0 1 2 3 751 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 1 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 | CC-ID | 754 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 755 | MT-ID | Algorithm | Flags |B|P|G|C|N|E|V|L| 756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 757 // SID/Label/Index (variable) // 758 +---------------------------------------------------------------+ 759 | | 760 // Optional TLV // 761 | | 762 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 763 The field CC-ID is as described in 764 [I-D.ietf-pce-pcep-extension-for-pce-controller]. Following new 765 fields are defined for CCI Object-Type TBD6 - 767 MT-ID: Multi-Topology ID (as defined in [RFC4915]). 769 Algorithm: Single octet identifying the algorithm the SID is 770 associated with. See [RFC8665]. 772 Flags: is used to carry any additional information pertaining to the 773 CCI. The following bits are defined - 775 * L-Bit (Local/Global): If set, then the value/index carried by 776 the CCI object has local significance. If not set, then the 777 value/index carried by this object has global significance. 779 * V-Bit (Value/Index): If set, then the CCI carries an absolute 780 value. If not set, then the CCI carries an index. 782 * E-Bit (Explicit-Null): If set, any upstream neighbor of the 783 node that advertised the SID MUST replace the SID with the 784 Explicit-NULL label (0 for IPv4) before forwarding the packet. 786 * N-Bit (No-PHP): If set, then the penultimate hop MUST NOT pop 787 the SID before delivering packets to the node that advertised 788 the SID. 790 * C-Bit (PCC Allocation): If the bit is set to 1, it indicates 791 that the allocation needs to be done by the PCC for this 792 central controller instruction. A PCE set this bit to request 793 the PCC to make an allocation from its SR label/ID space. A 794 PCC would set this bit to indicate that it has allocated the 795 CC-ID and report it to the PCE. 797 * Following bits are applicable when the SID represents an Adj- 798 SID only, it MUST be ignored for others - 800 + G-Bit (Group): When set, the G-Flag indicates that the Adj- 801 SID refers to a group of adjacencies (and therefore MAY be 802 assigned to other adjacencies as well). 804 + P-Bit (Persistent): When set, the P-Flag indicates that the 805 Adj-SID is persistently allocated, i.e., the Adj-SID value 806 remains consistent across router restart and/or interface 807 flap. 809 + B-Bit (Backup): If set, the Adj-SID refers to an adjacency 810 that is eligible for protection (e.g., using IP Fast Reroute 811 or MPLS-FRR (MPLS-Fast Reroute) as described in Section 2.1 812 of [RFC8402]. 814 + All unassigned bits MUST be set to zero at transmission and 815 ignored at receipt. 817 SID/Label/Index: According to the V and L flags, it contains either: 819 A 32-bit index defining the offset in the SID/Label space 820 advertised by this router. 822 A 24-bit label where the 20 rightmost bits are used for 823 encoding the label value. 825 7.4. FEC Object 827 The FEC Object is used to specify the FEC information and MAY be 828 carried within PCInitiate or PCRpt message. 830 FEC Object-Class is TBD3. 832 FEC Object-Type is 1 'IPv4 Node ID'. 834 0 1 2 3 835 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 1 836 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 837 | IPv4 Node ID | 838 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 840 FEC Object-Type is 2 'IPv6 Node ID'. 842 0 1 2 3 843 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 1 844 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 845 | | 846 // IPv6 Node ID (16 bytes) // 847 | | 848 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 850 FEC Object-Type is 3 'IPv4 Adjacency'. 852 0 1 2 3 853 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 1 854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 855 | Local IPv4 address | 856 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 857 | Remote IPv4 address | 858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 860 FEC Object-Type is 4 'IPv6 Adjacency'. 862 0 1 2 3 863 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 1 864 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 865 | | 866 // Local IPv6 address (16 bytes) // 867 | | 868 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 869 | | 870 // Remote IPv6 address (16 bytes) // 871 | | 872 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 874 FEC Object-Type is 5 'Unnumbered Adjacency with IPv4 NodeIDs'. 876 0 1 2 3 877 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 1 878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 879 | Local Node-ID | 880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 881 | Local Interface ID | 882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 883 | Remote Node-ID | 884 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 885 | Remote Interface ID | 886 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 888 FEC Object-Type is 6 'Linklocal IPv6 Adjacency'. 890 0 1 2 3 891 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 1 892 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 893 // Local IPv6 address (16 octets) // 894 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 895 | Local Interface ID | 896 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 897 // Remote IPv6 address (16 octets) // 898 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 899 | Remote Interface ID | 900 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 902 The FEC objects are as follows: 904 IPv4 Node ID: where IPv4 Node ID is specified as an IPv4 address of 905 the Node. FEC Object-type is 1, and the Object-Length is 4 in this 906 case. 908 IPv6 Node ID: where IPv6 Node ID is specified as an IPv6 address of 909 the Node. FEC Object-type is 2, and the Object-Length is 16 in this 910 case. 912 IPv4 Adjacency: where Local and Remote IPv4 address is specified as 913 pair of IPv4 addresses of the adjacency. FEC Object-type is 3, and 914 the Object-Length is 8 in this case. 916 IPv6 Adjacency: where Local and Remote IPv6 address is specified as 917 pair of IPv6 addresses of the adjacency. FEC Object-type is 4, and 918 the Object-Length is 32 in this case. 920 Unnumbered Adjacency with IPv4 NodeID: where a pair of Node ID / 921 Interface ID tuple is used. FEC Object-type is 5, and the Object- 922 Length is 16 in this case. 924 Linklocal IPv6 Adjacency: where a pair of (global IPv6 address, 925 interface ID) tuple is used. FEC object-type is 6, and the Object- 926 Length is 40 in this case. 928 8. Implementation Status 930 [Note to the RFC Editor - remove this section before publication, as 931 well as remove the reference to RFC 7942.] 933 This section records the status of known implementations of the 934 protocol defined by this specification at the time of posting of this 935 Internet-Draft, and is based on a proposal described in [RFC7942]. 936 The description of implementations in this section is intended to 937 assist the IETF in its decision processes in progressing drafts to 938 RFCs. Please note that the listing of any individual implementation 939 here does not imply endorsement by the IETF. Furthermore, no effort 940 has been spent to verify the information presented here that was 941 supplied by IETF contributors. This is not intended as, and must not 942 be construed to be, a catalog of available implementations or their 943 features. Readers are advised to note that other implementations may 944 exist. 946 According to [RFC7942], "this will allow reviewers and working groups 947 to assign due consideration to documents that have the benefit of 948 running code, which may serve as evidence of valuable experimentation 949 and feedback that have made the implemented protocols more mature. 951 It is up to the individual working groups to use this information as 952 they see fit". 954 8.1. Huawei's Proof of Concept based on ONOS 956 The PCE function was developed in the ONOS open source platform. 957 This extension was implemented on a private version as a proof of 958 concept for PCECC. 960 o Organization: Huawei 962 o Implementation: Huawei's PoC based on ONOS 964 o Description: PCEP as a southbound plugin was added to ONOS. To 965 support PCECC-SR, an earlier version of this I-D was implemented. 966 Refer https://wiki.onosproject.org/display/ONOS/PCEP+Protocol 968 o Maturity Level: Prototype 970 o Coverage: Partial 972 o Contact: satishk@huawei.com 974 9. Security Considerations 976 The security considerations described in 977 [I-D.ietf-pce-pcep-extension-for-pce-controller] apply to the 978 extensions described in this document. 980 As per [RFC8231], it is RECOMMENDED that these PCEP extensions only 981 be activated on authenticated and encrypted sessions across PCEs and 982 PCCs belonging to the same administrative authority, using Transport 983 Layer Security (TLS) [RFC8253] as per the recommendations and best 984 current practices in [RFC7525] (unless explicitly set aside in 985 [RFC8253]). 987 10. Manageability Considerations 989 10.1. Control of Function and Policy 991 A PCE or PCC implementation SHOULD allow to configure to enable/ 992 disable PCECC SR capability as a global configuration. The 993 implementation SHOULD also allow setting the local IP address used by 994 the PCEP session. 996 10.2. Information and Data Models 998 [RFC7420] describes the PCEP MIB, this MIB can be extended to get the 999 PCECC SR capability status. 1001 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 1002 enable/disable PCECC SR capability. 1004 10.3. Liveness Detection and Monitoring 1006 Mechanisms defined in this document do not imply any new liveness 1007 detection and monitoring requirements in addition to those already 1008 listed in [RFC5440]. 1010 10.4. Verify Correct Operations 1012 Mechanisms defined in this document do not imply any new operation 1013 verification requirements in addition to those already listed in 1014 [RFC5440] and [RFC8231]. 1016 10.5. Requirements On Other Protocols 1018 PCEP extensions defined in this document do not put new requirements 1019 on other protocols. 1021 10.6. Impact On Network Operations 1023 PCEP implementation SHOULD allow a limit to be placed on the rate of 1024 PCLabelUpd messages sent by PCE and processed by PCC. It SHOULD also 1025 allow sending a notification when a rate threshold is reached. 1027 11. IANA Considerations 1029 11.1. PCECC-CAPABILITY sub-TLV 1031 [I-D.ietf-pce-pcep-extension-for-pce-controller] defines the PCECC- 1032 CAPABILITY sub-TLV and requests that IANA to create a new sub- 1033 registry to manage the value of the PCECC-CAPABILITY sub-TLV's Flag 1034 field. 1036 IANA is requested to allocate a new bit in the PCECC-CAPABILITY sub- 1037 TLV Flag Field sub-registry, as follows: 1039 Bit Description Reference 1040 TBD1 SR This document 1042 11.2. PCEP Object 1044 IANA is requested to allocate new code-points for the new FEC object 1045 and a new Object-Type for CCI object in "PCEP Objects" sub-registry 1046 as follows: 1048 Object-Class Name Object-Type Reference 1049 Value 1050 TBD3 FEC 1: IPv4 Node ID This document 1051 2: IPv6 Node ID This document 1052 3: IPv4 Adjacency This document 1053 4: IPv6 Adjacency This document 1054 5: Unnumbered Adjacency with This document 1055 IPv4 NodeID 1056 6: Linklocal IPv6 Adjacency This document 1057 TBD CCI 1058 TBD6: SR-MPLS This document 1060 11.3. PCEP-Error Object 1062 IANA is requested to allocate a new error-value within the "PCEP- 1063 ERROR Object Error Types and Values" sub-registry of the PCEP Numbers 1064 registry for the following errors: 1066 Error-Type Meaning 1067 ---------- ------- 1068 6 Mandatory Object missing. 1070 Error-value = TBD5 : FEC object missing 1071 19 Invalid operation. 1073 Error-value = TBD4 : SR capability was 1074 not advertised 1076 11.4. CCI Object Flag Field for SR 1078 IANA is requested to create a new sub-registry to manage the Flag 1079 field of the CCI Object-Type=TBD6 for SR called "CCI Object Flag 1080 Field for SR". New values are to be assigned by Standards Action 1081 [RFC8126]. Each bit should be tracked with the following qualities: 1083 o Bit number (counting from bit 0 as the most significant bit) 1084 o Capability description 1085 o Defining RFC 1087 Following bits are defined for the CCI Object flag field for SR in 1088 this document as follows: 1090 Bit Description Reference 1091 0-7 Unassigned This document 1092 8 B-Bit - Backup This document 1093 9 P-Bit - Persistent This document 1094 10 G-Bit - Group This document 1095 11 C-Bit - PCC Allocation This document 1096 12 N-Bit - No-PHP This document 1097 13 E-Bit - Explicit-Null This document 1098 14 V-Bit - Value/Index This document 1099 15 L-Bit - Local/Global This document 1101 12. Acknowledgments 1103 We would like to thank Robert Tao, Changjing Yan, Tieying Huang, 1104 Avantika, and Aijun Wang for their useful comments and suggestions. 1106 13. References 1108 13.1. Normative References 1110 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1111 Requirement Levels", BCP 14, RFC 2119, 1112 DOI 10.17487/RFC2119, March 1997, 1113 . 1115 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 1116 (TE) Extensions to OSPF Version 2", RFC 3630, 1117 DOI 10.17487/RFC3630, September 2003, 1118 . 1120 [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 1121 Support of Generalized Multi-Protocol Label Switching 1122 (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, 1123 . 1125 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 1126 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 1127 RFC 4915, DOI 10.17487/RFC4915, June 2007, 1128 . 1130 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1131 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1132 2008, . 1134 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 1135 in Support of Generalized Multi-Protocol Label Switching 1136 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 1137 . 1139 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1140 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1141 DOI 10.17487/RFC5440, March 2009, 1142 . 1144 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 1145 S. Ray, "North-Bound Distribution of Link-State and 1146 Traffic Engineering (TE) Information Using BGP", RFC 7752, 1147 DOI 10.17487/RFC7752, March 2016, 1148 . 1150 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1151 Code: The Implementation Status Section", BCP 205, 1152 RFC 7942, DOI 10.17487/RFC7942, July 2016, 1153 . 1155 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1156 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1157 May 2017, . 1159 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 1160 Computation Element Communication Protocol (PCEP) 1161 Extensions for Stateful PCE", RFC 8231, 1162 DOI 10.17487/RFC8231, September 2017, 1163 . 1165 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 1166 "PCEPS: Usage of TLS to Provide a Secure Transport for the 1167 Path Computation Element Communication Protocol (PCEP)", 1168 RFC 8253, DOI 10.17487/RFC8253, October 2017, 1169 . 1171 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 1172 Computation Element Communication Protocol (PCEP) 1173 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 1174 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 1175 . 1177 [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. 1178 Hardwick, "Conveying Path Setup Type in PCE Communication 1179 Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, 1180 July 2018, . 1182 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 1183 and J. Hardwick, "Path Computation Element Communication 1184 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 1185 DOI 10.17487/RFC8664, December 2019, 1186 . 1188 [I-D.ietf-pce-pcep-extension-for-pce-controller] 1189 Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP 1190 Procedures and Protocol Extensions for Using PCE as a 1191 Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 1192 extension-for-pce-controller-09 (work in progress), 1193 November 2020. 1195 13.2. Informative References 1197 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 1198 Label Switching Architecture", RFC 3031, 1199 DOI 10.17487/RFC3031, January 2001, 1200 . 1202 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1203 Element (PCE)-Based Architecture", RFC 4655, 1204 DOI 10.17487/RFC4655, August 2006, 1205 . 1207 [RFC7025] Otani, T., Ogaki, K., Caviglia, D., Zhang, F., and C. 1208 Margaria, "Requirements for GMPLS Applications of PCE", 1209 RFC 7025, DOI 10.17487/RFC7025, September 2013, 1210 . 1212 [RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path 1213 Computation Element Architecture", RFC 7399, 1214 DOI 10.17487/RFC7399, October 2014, 1215 . 1217 [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. 1218 Hardwick, "Path Computation Element Communication Protocol 1219 (PCEP) Management Information Base (MIB) Module", 1220 RFC 7420, DOI 10.17487/RFC7420, December 2014, 1221 . 1223 [RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for 1224 Application-Based Network Operations", RFC 7491, 1225 DOI 10.17487/RFC7491, March 2015, 1226 . 1228 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1229 "Recommendations for Secure Use of Transport Layer 1230 Security (TLS) and Datagram Transport Layer Security 1231 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1232 2015, . 1234 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1235 Writing an IANA Considerations Section in RFCs", BCP 26, 1236 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1237 . 1239 [RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 1240 and D. Dhody, "Optimizations of Label Switched Path State 1241 Synchronization Procedures for a Stateful PCE", RFC 8232, 1242 DOI 10.17487/RFC8232, September 2017, 1243 . 1245 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 1246 Architecture for Use of PCE and the PCE Communication 1247 Protocol (PCEP) in a Network with Central Control", 1248 RFC 8283, DOI 10.17487/RFC8283, December 2017, 1249 . 1251 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1252 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1253 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1254 July 2018, . 1256 [RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S., 1257 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1258 Routing with the MPLS Data Plane", RFC 8660, 1259 DOI 10.17487/RFC8660, December 2019, 1260 . 1262 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 1263 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1264 Extensions for Segment Routing", RFC 8665, 1265 DOI 10.17487/RFC8665, December 2019, 1266 . 1268 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1269 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1270 Extensions for Segment Routing", RFC 8667, 1271 DOI 10.17487/RFC8667, December 2019, 1272 . 1274 [I-D.ietf-teas-pcecc-use-cases] 1275 Li, Z., Khasanov, B., Dhody, D., Zhao, Q., Ke, Z., Fang, 1276 L., Zhou, C., Communications, T., Rachitskiy, A., and A. 1277 Gulida, "The Use Cases for Path Computation Element (PCE) 1278 as a Central Controller (PCECC).", draft-ietf-teas-pcecc- 1279 use-cases-06 (work in progress), September 2020. 1281 [I-D.ietf-pce-pcep-yang] 1282 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1283 YANG Data Model for Path Computation Element 1284 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1285 yang-15 (work in progress), October 2020. 1287 [I-D.ietf-pce-binding-label-sid] 1288 Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J., 1289 Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID 1290 in PCE-based Networks.", draft-ietf-pce-binding-label- 1291 sid-05 (work in progress), October 2020. 1293 [I-D.litkowski-pce-state-sync] 1294 Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter 1295 Stateful Path Computation Element (PCE) Communication 1296 Procedures.", draft-litkowski-pce-state-sync-09 (work in 1297 progress), November 2020. 1299 [I-D.dhodylee-pce-pcep-ls] 1300 Dhody, D., Peng, S., Lee, Y., Ceccarelli, D., Wang, A., 1301 and G. Mishra, "PCEP extensions for Distribution of Link- 1302 State and TE Information", draft-dhodylee-pce-pcep-ls-19 1303 (work in progress), November 2020. 1305 [I-D.dhody-pce-pcep-extension-pce-controller-srv6] 1306 Li, Z., Peng, S., Geng, X., and M. Negi, "PCEP Procedures 1307 and Protocol Extensions for Using PCE as a Central 1308 Controller (PCECC) for SRv6", draft-dhody-pce-pcep- 1309 extension-pce-controller-srv6-05 (work in progress), 1310 November 2020. 1312 Appendix A. Contributor Addresses 1314 Dhruv Dhody 1315 Huawei Technologies 1316 Divyashree Techno Park, Whitefield 1317 Bangalore, Karnataka 560066 1318 India 1320 EMail: dhruv.ietf@gmail.com 1322 Satish Karunanithi 1323 Huawei Technologies 1324 Divyashree Techno Park, Whitefield 1325 Bangalore, Karnataka 560066 1326 India 1328 EMail: satishk@huawei.com 1330 Adrian Farrel 1331 Juniper Networks, Inc 1332 UK 1334 EMail: adrian@olddog.co.uk 1336 Xuesong Geng 1337 Huawei Technologies 1338 China 1340 Email: gengxuesong@huawei.com 1342 Udayasree Palle 1344 EMail: udayasreereddy@gmail.com 1346 Katherine Zhao 1347 Huawei Technologies 1348 2330 Central Expressway 1349 Santa Clara, CA 95050 1350 USA 1352 EMail: katherine.zhao@huawei.com 1354 Boris Zhang 1355 Telus Ltd. 1356 Toronto 1357 Canada 1359 EMail: boris.zhang@telus.com 1360 Alex Tokar 1361 Cisco Systems 1362 Slovak Republic 1364 EMail: atokar@cisco.com 1366 Authors' Addresses 1368 Zhenbin Li 1369 Huawei Technologies 1370 Huawei Bld., No.156 Beiqing Rd. 1371 Beijing 100095 1372 China 1374 EMail: lizhenbin@huawei.com 1376 Shuping Peng 1377 Huawei Technologies 1378 Huawei Bld., No.156 Beiqing Rd. 1379 Beijing 100095 1380 China 1382 EMail: pengshuping@huawei.com 1384 Mahendra Singh Negi 1385 RtBrick Inc 1386 N-17L, 18th Cross Rd, HSR Layout 1387 Bangalore, Karnataka 560102 1388 India 1390 EMail: mahend.ietf@gmail.com 1392 Quintin Zhao 1393 Etheric Networks 1394 1009 S CLAREMONT ST 1395 SAN MATEO, CA 94402 1396 USA 1398 EMail: qzhao@ethericnetworks.com 1399 Chao Zhou 1400 HPE 1402 EMail: chaozhou_us@yahoo.com