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Xu 5 Expires: December 24, 2021 ZTE Corporation 6 June 22, 2021 8 PCEP Procedures and Protocol Extensions for Using PCE as a Central 9 Controller (PCECC) of BIER 10 draft-chen-pce-pcep-extension-pce-controller-bier-01 12 Abstract 14 This draft specifies the procedures and PCEP protocol extensions for 15 using the PCE as the central controller for BIER. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on December 24, 2021. 34 Copyright Notice 36 Copyright (c) 2021 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Conventions used in this document . . . . . . . . . . . . . . 3 53 3. PCECC BIER Requirements . . . . . . . . . . . . . . . . . . . 3 54 4. Procedures for Using the PCE as the Central Controller 55 (PCECC) in BIER . . . . . . . . . . . . . . . . . . . . . . . 3 56 4.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 3 57 4.2. New Functions . . . . . . . . . . . . . . . . . . . . . . 4 58 4.3. PCECC Capability Advertisement . . . . . . . . . . . . . 4 59 4.4. BIER Path Operations . . . . . . . . . . . . . . . . . . 4 60 4.4.1. PCECC Bit Index Explicit Replication (BIER) . . . . . 4 61 4.4.1.1. PCECC BIER information allocation . . . . . . . . 5 62 4.4.1.2. Redundant PCEs . . . . . . . . . . . . . . . . . 5 63 4.4.1.3. Re Delegation and Cleanup . . . . . . . . . . . . 5 64 4.4.1.4. Synchronization of BIER information Allocations . 5 65 4.5. PCEP messages . . . . . . . . . . . . . . . . . . . . . . 5 66 4.5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . 5 67 4.5.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . 5 68 4.5.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . 6 69 4.5.3. CCI object . . . . . . . . . . . . . . . . . . . . . 6 70 4.5.3.1. BIER Encapsulation Sub TLV . . . . . . . . . . . 7 71 4.5.4. FEC Object . . . . . . . . . . . . . . . . . . . . . 8 72 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 73 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 74 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 75 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 76 9. Normative References . . . . . . . . . . . . . . . . . . . . 8 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 79 1. Introduction 81 [RFC8283]introduces the architecture for PCE as a central controller 82 as an extension of the architecture described in[RFC4655] and assumes 83 the continued use of PCEP as the protocol used between PCE and PCC. 84 [RFC8283]further examines the motivations and applicability for PCEP 85 as a Southbound Interface (SBI), and introduces the implications for 86 the protocol. 88 [I-D.ietf-pce-pcep-extension-for-pce-controller]specifies the 89 procedures and PCEP protocol extensions for using the PCE as the 90 central controller for static LSPs, where LSPs can be provisioned as 91 explicit label instructions at each hop on the end-to-end path. Each 92 router along the path must be told what label-forwarding instructions 93 to program and what resources to reserve. The PCE-based controller 94 keeps a view of the network and determines the paths of the end-to- 95 end LSPs, and the controller uses PCEP to communicate with each 96 router along the path of the end-to-end LSP. 98 [RFC8279] defines a Bit Index Explicit Replication (BIER) 99 architecture where all intended multicast receivers are encoded as a 100 bitmask in the multicast packet header within different 101 encapsulations such as described in [RFC8296]. A router that 102 receives such a packet will forward the packet based on the bit 103 position in the packet header towards the receiver(s) following a 104 precomputed tree for each of the bits in the packet. Each receiver 105 is represented by a unique bit in the bitmask. 107 This document specifies the procedures and PCEP protocol extensions 108 when a PCE-based controller is also responsible for configuring the 109 forwarding actions on the routers (BIER information distribution in 110 this case). 112 2. Conventions used in this document 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in RFC2119. 118 3. PCECC BIER Requirements 120 Following key requirements for PCECC-BIER should be considered 121 when`designing the PCECC based solution: 123 o PCEP speaker supporting this draft needs to have the capability to 124 advertise its PCECC-BIER capability to its peers. 126 o PCEP speaker not supporting this draft needs to be able to reject 127 PCECC-BIER related message with a reason code that indicates no 128 support for PCECC. 130 o PCEP procedures needs to provide a means to update (or cleanup) 131 the BIER related informations (BIER subdomain-id, BFR-id and BSL 132 etc) to the PCC. 134 o PCEP procedures needs to provide a means to synchronize the BIER 135 related informations (BIER subdomain-id, BFR-id and BSL etc) 136 between PCE to PCC in the PCEP messages. 138 4. Procedures for Using the PCE as the Central Controller (PCECC) in 139 BIER 141 4.1. Stateful PCE Model 143 Active stateful PCE is described in [RFC8231]. PCE as a central 144 controller (PCECC) reuses existing Active stateful PCE mechanism as 145 much as possible to control the LSP. 147 4.2. New Functions 149 This document uses the same PCEP messages and its extensions which 150 are described in [I-D.ietf-pce-pcep-extension-for-pce-controller]for 151 PCECC-BIER as well. 153 PCEP messages PCRpt, PCInitiate, PCUpd are also used to send LSP 154 Reports, LSP setup and LSP update respectively. The extended 155 PCInitiate message described in 156 [I-D.ietf-pce-pcep-extension-for-pce-controller] is used to download 157 or cleanup central controller's instructions (CCIs) (BIER related 158 informations in scope of this document). The extended PCRpt message 159 described in [I-D.ietf-pce-pcep-extension-for-pce-controller] is also 160 used to report the CCIs (BIER related informations) from PCC to PCE. 162 [I-D.ietf-pce-pcep-extension-for-pce-controller]specify an object 163 called CCI for the encoding of central controller's instructions.This 164 document extends the CCI by defining another object-type for BIER. 166 4.3. PCECC Capability Advertisement 168 During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) 169 advertise their support of PCECC extensions. A PCEP Speaker includes 170 the "PCECC Capability" sub-TLV, described in 171 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 173 This document adds B-bit in PCECC-CAPABILITY sub-TLV for BIER. 175 4.4. BIER Path Operations 177 The PCEP messages pertaining to PCECC-BIER MUST include PATH-SETUP- 178 TYPE TLV [RFC8408] with PST=TBD in the SRP object to clearly identify 179 the PCECC-BIER LSP is intended. 181 4.4.1. PCECC Bit Index Explicit Replication (BIER) 183 BIER as described in [RFC8402] defines an architecture where all 184 intended multicast receivers are encoded as a bitmask in the 185 multicast packet header within different encapsulations such as 186 described in [RFC8296]. 188 [RFC8401] defines IS-IS extensions to distribute the BIER 189 information(BIER subdomain-id, BFR-id and BSL etc).This document 190 proposes a new mechanism where PCE allocates centrally and uses PCEP 191 to advertise the BIER information(BIER subdomain-id, BFR-id and BSL 192 etc). In some deployments PCE (and PCEP) are better suited than IGP 193 because of centralized nature of PCE and direct TCP based PCEP 194 session to the node. 196 4.4.1.1. PCECC BIER information allocation 198 Each node (PCC) is allocated BIER information by the PCECC.The BIER 199 information mainly includes BIER subdomain-id, BFR-id, BSL, BFR 200 prefix, BSL, Encapsulation Type, BIFT ID,Max SI and BFR nexthop. 202 The PCECC allocate the BIER subdomain-id, BFR-id , BFR prefix, BSL, 203 Encapsulation Type, BIFT ID, and Max SI to the PCC, On receiving the 204 BIER information allocation, each node (PCC) uses IGP protocol to 205 distribute BIER related information to other nodes. The node 206 calculate the nexthop. 208 4.4.1.2. Redundant PCEs 210 [I-D.litkowski-pce-state-sync] describes synchronization mechanism 211 between the stateful PCEs. The BIER informations allocated by a PCE 212 MUST also be synchronized among PCEs for PCECC BIER state 213 synchronization. 215 4.4.1.3. Re Delegation and Cleanup 217 [I-D.ietf-pce-pcep-extension-for-pce-controller] describes the action 218 needed for CCIs for the Basic PCECC LSP on this terminated 219 session.Similarly actions should be applied for the BIER information 220 as well. 222 4.4.1.4. Synchronization of BIER information Allocations 224 [I-D.ietf-pce-pcep-extension-for-pce-controller]describes the 225 synchronization of Central Controller's Instructions (CCI) via LSP 226 state synchronization as described in [RFC8231] and [RFC8232].Same 227 procedures should be applied for BIER information as well. 229 4.5. PCEP messages 231 4.5.1. The OPEN Object 233 4.5.1.1. PCECC Capability sub-TLV 235 [I-D.ietf-pce-pcep-extension-for-pce-controller] defined the 236 PCECCCAPABILITY TLV. A new B-bit is defined in PCECC-CAPABILITY sub- 237 TLV for PCECC-BIER: 239 0 1 2 3 240 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 1 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 | Type=TBD | Length | 243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 244 | Flags |B|I|S| 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 Figure 1 249 B (PCECC-BIER-CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it 250 indicates that the PCEP speaker is capable for PCECC-BIER capability 251 and PCE would allocate BIER information on this session. 253 4.5.2. PATH-SETUP-TYPE TLV 255 The PATH-SETUP-TYPE TLV is defined in [RFC8408]. PST = TBD is used 256 when Path is setup via PCECC BIER mode.On a PCRpt/PCUpd/PCInitiate 257 message, the PST=TBD indicates that this path was setup via a PCECC- 258 BIER based mechanism where either the BIER informations were 259 allocated/instructed by PCE via PCECC mechanism. 261 4.5.3. CCI object 263 The Central Control Instructions (CCI) Object is used by the PCE to 264 specify the forwarding instructions is defined in 265 [I-D.ietf-pce-pcep-extension-for-pce-controller]. This document 266 defines another object-type for BIER purpose. 268 CCI Object-Type is TBD for BIER as below 270 0 1 2 3 271 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 1 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 273 | CC-ID | 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 275 | subdomain-ID | Algorithm | Flags |C|O| 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 277 | BFR-ID | Reserved | 278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 279 | | 280 // Optional TLV // 281 | | 282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 284 Figure 2 286 The field CC-ID is as described in 287 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 289 BIER subdomain-ID: Unique value identifying the BIER subdomain. (as 290 defined in [RFC8401]. 292 The 0 and C bit was defined in 293 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 295 BFR-ID: A 2-octet field encoding the BFR-id, as documented in 296 [RFC8279]. 298 Optional TLV: There are two optional TLV are defined in this draft. 300 4.5.3.1. BIER Encapsulation Sub TLV 302 0 1 2 3 303 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 1 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 305 | Type | Length | 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 | Flage | ET| Reserved | 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 | Max SI |BS Len | BIFT-id | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 312 Figure 3 314 The code point for the TLV type is to be defined by IANA. 316 Length:4 318 ET-Flag:ET(Encapsulation type) Flag,There are two Encapsulation 319 Types: 321 o 0b00-MPLS encapsulation. 323 o 0b01-Non-MPLS encapsulation. 325 Max SI: A 1 octet field encoding the Maximum Set Identifier(Section 1 326 of [RFC8279] ) used in the encapsulation for this BIER subdomain for 327 this BitString length. 329 Local BitString Length (BS Len): Encoded BitString length as per 330 [RFC8296]. 332 BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id 333 range. 335 4.5.4. FEC Object 337 BIER information is always associated with a host prefix, so we reuse 338 FEC Object 1'IPv4 Node ID' and FEC Object-Type 2 'IPv6 Node ID' 339 defined in [I-D.zhao-pce-pcep-extension-pce-controller-sr] to carry 340 the BFR prefix. 342 5. Security Considerations 344 TBD. 346 6. IANA Considerations 348 TBD. 350 7. Contributors 352 The following author contributed significantly to this document: 354 Dhruv Dhody 356 Huawei 358 rdhruv.ietf@gmail.com 360 8. Acknowledgements 362 TBD. 364 9. Normative References 366 [I-D.ietf-pce-pcep-extension-for-pce-controller] 367 Li, Z., Peng, S., Negi, M. S., Zhao, Q., and C. Zhou, 368 "PCEP Procedures and Protocol Extensions for Using PCE as 369 a Central Controller (PCECC) of LSPs", draft-ietf-pce- 370 pcep-extension-for-pce-controller-14 (work in progress), 371 March 2021. 373 [I-D.litkowski-pce-state-sync] 374 Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter 375 Stateful Path Computation Element (PCE) Communication 376 Procedures.", draft-litkowski-pce-state-sync-10 (work in 377 progress), February 2021. 379 [I-D.zhao-pce-pcep-extension-pce-controller-sr] 380 Li, Z., Peng, S., Negi, M. S., Zhao, Q., and C. Zhou, 381 "PCEP Procedures and Protocol Extensions for Using PCE as 382 a Central Controller (PCECC) for Segment Routing (SR) MPLS 383 Segment Identifier (SID) Allocation and Distribution.", 384 draft-zhao-pce-pcep-extension-pce-controller-sr-09 (work 385 in progress), November 2020. 387 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 388 Element (PCE)-Based Architecture", RFC 4655, 389 DOI 10.17487/RFC4655, August 2006, 390 . 392 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 393 Computation Element Communication Protocol (PCEP) 394 Extensions for Stateful PCE", RFC 8231, 395 DOI 10.17487/RFC8231, September 2017, 396 . 398 [RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 399 and D. Dhody, "Optimizations of Label Switched Path State 400 Synchronization Procedures for a Stateful PCE", RFC 8232, 401 DOI 10.17487/RFC8232, September 2017, 402 . 404 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 405 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 406 Explicit Replication (BIER)", RFC 8279, 407 DOI 10.17487/RFC8279, November 2017, 408 . 410 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 411 Architecture for Use of PCE and the PCE Communication 412 Protocol (PCEP) in a Network with Central Control", 413 RFC 8283, DOI 10.17487/RFC8283, December 2017, 414 . 416 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 417 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 418 for Bit Index Explicit Replication (BIER) in MPLS and Non- 419 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 420 2018, . 422 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 423 Zhang, "Bit Index Explicit Replication (BIER) Support via 424 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 425 . 427 [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. 428 Hardwick, "Conveying Path Setup Type in PCE Communication 429 Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, 430 July 2018, . 432 Authors' Addresses 434 Ran Chen 435 ZTE Corporation 437 Email: chen.ran@zte.com.cn 439 Chun Zhu 440 ZTE Corporation 442 Email: zhu.chun@zte.com.cn 444 BenChong Xu 445 ZTE Corporation 447 Email: xu.benchong@zte.com.cn