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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) == Outdated reference: A later version (-30) exists of draft-ietf-pce-pcep-extension-native-ip-05 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TEAS Working Group A. Wang 3 Internet-Draft China Telecom 4 Intended status: Experimental B. Khasanov 5 Expires: February 11, 2021 Huawei Technologies 6 Q. Zhao 7 Etheric Networks 8 H. Chen 9 Futurewei 10 August 10, 2020 12 PCE in Native IP Network 13 draft-ietf-teas-pce-native-ip-10 15 Abstract 17 This document defines the architecture for traffic engineering within 18 native IP network, using multiple BGP sessions strategy and PCE 19 -based central control mechanism. It uses the Central Control 20 Dynamic Routing (CCDR) procedures described in this document, and the 21 Path Computation Element Communication Protocol (PCEP) extension 22 specified in draft ietf-pce-pcep-extension-native-ip. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on February 11, 2021. 41 Copyright Notice 43 Copyright (c) 2020 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. CCDR Architecture in Simple Topology . . . . . . . . . . . . 4 61 4. CCDR Architecture in Large Scale Topology . . . . . . . . . . 5 62 5. CCDR Multiple BGP Sessions Strategy . . . . . . . . . . . . . 6 63 6. PCEP Extension for Key Parameters Delivery . . . . . . . . . 8 64 7. Deployment Consideration . . . . . . . . . . . . . . . . . . 9 65 7.1. Scalability . . . . . . . . . . . . . . . . . . . . . . . 9 66 7.2. High Availability . . . . . . . . . . . . . . . . . . . . 9 67 7.3. Incremental deployment . . . . . . . . . . . . . . . . . 10 68 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 69 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 70 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11 71 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 72 11.1. Normative References . . . . . . . . . . . . . . . . . . 11 73 11.2. Informative References . . . . . . . . . . . . . . . . . 12 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 76 1. Introduction 78 [RFC8735] describes the scenarios and simulation results for traffic 79 engineering in the native IP network to provide End-to-End (E2E) 80 performance assurance and QoS using PCE based centralized control, 81 referred to as Centralized Control Dynamic Routing (CCDR). Based on 82 the various scenarios and analysis as per [RFC8735], the solution for 83 traffic engineering in native IP network should meet the following 84 criteria: 86 o Same solution for native IPv4 and IPv6 traffic. 88 o Support for intra-domain and inter-domain scenarios. 90 o Achieve End to End traffic assurance, with determined QoS 91 behavior. 93 o No upgrade to forwarding behaviour of the router. 95 o Capable to exploit the power of centrally control and the 96 flexibility/robustness of distributed control protocol. 98 o Coping with the differentiation requirements for large amount 99 traffic and prefixes. 101 o Adjust the optimal path dynamically upon the change of network 102 status. No physical links resources reservation in advance. 104 Stateful PCE [RFC8231] specifies a set of extensions to PCEP to 105 enable stateful control of paths such as MPLS-TE Label Switched 106 Paths(LSP)s between and across PCEP sessions in compliance with 107 [RFC4657]. It includes mechanisms to achieve state synchronization 108 between Path Computation Clients(PCCs) and PCEs, delegation of 109 control of LSPs to PCEs, and PCE control of timing and sequence of 110 path computations within and across PCEP sessions. Furthermore, 111 [RFC8281] specifies a mechanism to dynamically instantiate LSPs on a 112 PCC based on the requests from a stateful PCE or a controller using 113 stateful PCE. [RFC8283] introduces the architecture for PCE as a 114 central controller as an extension of the architecture described in 115 [RFC4655] and assumes the continued use of PCEP as the protocol used 116 between PCE and PCC.[RFC8283] further examines the motivations and 117 applicability for PCEP as a Southbound Interface (SBI), and 118 introduces the implications for the protocol. 120 This document defines the framework for traffic engineering within 121 native IP network, using multiple BGP session strategy, to meet the 122 above criteria in dynamical and centrally control mode. The 123 framework is referred as CCDR framework. It depends on the central 124 control (PCE) element to compute the optimal path for selected 125 traffic, and utilizes the dynamic routing behavior of traditional 126 IGP/BGP protocols to forward such traffic. 128 The control messages between PCE and underlying network node are 129 transmitted via Path Computation Element Communications Protocol 130 (PCEP) protocol. The related PCEP extensions are provided in draft 131 [I-D.ietf-pce-pcep-extension-native-ip]. 133 2. Terminology 135 This document uses the following terms defined in [RFC5440]: 137 o PCE 139 o PCEP 141 o PCC 143 The following terms are used in this document: 145 o CCDR: Central Control Dynamic Routing 146 o E2E: End to End 148 o ECMP: Equal-Cost Multipath 150 o RR: Route Reflector 152 o SDN: Software Defined Network 154 3. CCDR Architecture in Simple Topology 156 Figure 1 illustrates the CCDR architecture for traffic engineering in 157 simple topology. The topology is comprised by four devices which are 158 SW1, SW2, R1, R2. There are multiple physical links between R1 and 159 R2. Traffic between prefix PF11(on SW1) and prefix PF21(on SW2) is 160 normal traffic, traffic between prefix PF12(on SW1) and prefix 161 PF22(on SW2) is priority traffic that should be treated with 162 priority. 164 In Intra-AS scenario, IGP and BGP are deployed between R1 and R2. In 165 inter-AS scenario, only native BGP protocol is deployed. The traffic 166 between each address pair may change in real time and the 167 corresponding source/destination addresses of the traffic may also 168 change dynamically. 170 The key ideas of the CCDR framework for this simple topology are the 171 followings: 173 o Build two BGP sessions between R1 and R2, via the different 174 loopback addresses on these routers. 176 o Send different prefixes via the established BGP sessions. For 177 example, PF11/PF21 via the BGP session 1 and PF12/PF22 via the BGP 178 session 2. 180 o Set the explicit peer route on R1 and R2 respectively for BGP next 181 hop to different physical link addresses between R1 and R2. Such 182 explicit peer route can be set in the format of static route to 183 BGP peer address, which is different from the route learned from 184 the IGP protocol. 186 After the above actions, the bi-direction traffic between the PF11 187 and PF21, and the bi-direction traffic between PF12 and PF22 will go 188 through different physical links between R1 and R2, each set of 189 traffic pass through different dedicated physical links. 191 If there is more traffic between PF12 and PF22 that needs to be 192 assured , one can add more physical links between R1 and R2 to reach 193 the the next hop for BGP session 2. In this cases the prefixes that 194 advertised by the BGP peers need not be changed. 196 If, for example, there is bi-direction traffic from another address 197 pair that needs to be assured (for example prefix PF13/PF23), and the 198 total volume of assured traffic does not exceed the capacity of the 199 previously provisioned physical links, one need only to advertise the 200 newly added source/destination prefixes via the BGP session 2. The 201 bi-direction traffic between PF13/PF23 will go through the assigned 202 dedicated physical links as the traffic between PF12/PF22. 204 Such decouple philosophy gives network operator flexible control 205 capability on the network traffic, achieve the determined QoS 206 assurance effect to meet the application's requirement. The router 207 needs only support native IP and multiple BGP sessions setup via 208 different loopback addresses. 210 +-----+ 211 +----------+ PCE +--------+ 212 | +-----+ | 213 | | 214 | BGP Session 1(lo11/lo21)| 215 +-------------------------+ 216 | | 217 | BGP Session 2(lo12/lo22)| 218 +-------------------------+ 219 PF12 | | PF22 220 PF11 | | PF21 221 +---+ +-----+-----+ +-----+-----+ +---+ 222 |SW1+---------+(lo11/lo12)+-------------+(lo21/lo22)+--------------+SW2| 223 +---+ | R1 +-------------+ R2 | +---+ 224 +-----------+ +-----------+ 226 Figure 1: CCDR framework in simple topology 228 4. CCDR Architecture in Large Scale Topology 230 When the assured traffic spans across the large scale network, as 231 that illustrated in Figure 2, the multiple BGP sessions cannot be 232 established hop by hop, especially for the iBGP within one AS. 234 For such scenario, we should consider using the Route Reflector (RR) 235 [RFC4456] to achieve the similar effect. Every edge router will 236 establish two BGP sessions with the RR via different loopback 237 addresses respectively. The other steps for traffic differentiation 238 are same as that described in the CCDR framework for simple topology. 240 As shown in Figure 2, if we select R3 as the RR, every edge router(R1 241 and R7 in this example) will build two BGP session with the RR. If 242 the PCE selects the dedicated path as R1-R2-R4-R7, then the operator 243 should set the explicit peer routes via PCEP protocol on these 244 routers respectively, pointing to the BGP next hop (loopback 245 addresses of R1 and R7, which are used to send the prefix of the 246 assured traffic) to the selected forwarding address. 248 +-----+ 249 +----------------+ PCE +------------------+ 250 | +--+--+ | 251 | | | 252 | | | 253 | ++-+ | 254 +------------------+R3+-------------------+ 255 PF12 | +--+ | PF22 256 PF11 | | PF21 257 +---+ ++-+ +--+ +--+ +-++ +---+ 258 |SW1+-------+R1+----------+R5+----------+R6+---------+R7+--------+SW2| 259 +---+ ++-+ +--+ +--+ +-++ +---+ 260 | | 261 | | 262 | +--+ +--+ | 263 +------------+R2+----------+R4+-----------+ 264 +--+ +--+ 265 Figure 2: CCDR framework in large scale network 267 5. CCDR Multiple BGP Sessions Strategy 269 In general situation, different applications may require different 270 QoS criteria, which may include: 272 o Traffic that requires low latency and is not sensitive to packet 273 loss. 275 o Traffic that requires low packet loss and can endure higher 276 latency. 278 o Traffic that requires low jitter. 280 These different traffic requirements can be summarized in the 281 following table: 283 +----------------+-------------+---------------+-----------------+ 284 | Prefix Set No. | Latency | Packet Loss | Jitter | 285 +----------------+-------------+---------------+-----------------+ 286 | 1 | Low | Normal | Don't care | 287 +----------------+-------------+---------------+-----------------+ 288 | 2 | Normal | Low | Dont't care | 289 +----------------+-------------+---------------+-----------------+ 290 | 3 | Normal | Normal | Low | 291 +----------------+-------------+---------------+-----------------+ 292 Table 1. Traffic Requirement Criteria 294 For Prefix Set No.1, we can select the shortest distance path to 295 carry the traffic; for Prefix Set No.2, we can select the path that 296 is comprised by under loading links from end to end; For Prefix Set 297 No.3, we can let all assured traffic pass the determined single path, 298 no Equal Cost Multipath (ECMP) distribution on the parallel links is 299 desired. 301 It is almost impossible to provide an End-to-End (E2E) path 302 efficiently with latency, jitter, packet loss constraints to meet the 303 above requirements in large scale IP-based network via the 304 distributed routing protocol, but these requirements can be solved 305 with the assistance of PCE, as that described in [RFC4655] and 306 [RFC8283] because the PCE has the overall network view, can collect 307 real network topology and network performance information about the 308 underlying network, select the appropriate path to meet various 309 network performance requirements of different traffics. 311 The framework to implement the CCDR Multiple BGP sessions strategy 312 are the followings. Here PCE is the main component of the Software 313 Definition Network (SDN) controller and is responsible for optimal 314 path computation for priority traffic. 316 o SDN controller gets topology via BGP-LS[RFC7752] and link 317 utilization information via existing Network Monitor System (NMS) 318 from the underlying network. 320 o PCE calculates the appropriate path upon application's 321 requirements, sends the key parameters to edge/RR routers(R1, R7 322 and R3 in Fig.3) to establish multiple BGP sessions and advertises 323 different prefixes via them. The loopback addresses used for BGP 324 sessions should be planned in advance and distributed in the 325 domain. 327 o PCE sends the route information to the routers (R1,R2,R4,R7 in 328 Fig.3) on forwarding path via PCEP 329 [I-D.ietf-pce-pcep-extension-native-ip], to build the path to the 330 BGP next-hop of the advertised prefixes. 332 o If the assured traffic prefixes were changed but the total volume 333 of assured traffic does not exceed the physical capacity of the 334 previous E2E path, PCE needs only change the prefixed advertised 335 via the edge routers (R1,R7 in Fig.3). 337 o If the volume of assured traffic exceeds the capacity of previous 338 calculated path, PCE can recalculate and add the appropriate paths 339 to accommodate the exceeding traffic. After that, PCE needs to 340 update on-path routers to build the forwarding path hop by hop. 342 +------------+ 343 | Application| 344 +------+-----+ 345 | 346 +--------+---------+ 347 +----------+SDN Controller/PCE+-----------+ 348 | +--------^---------+ | 349 | | | 350 | | | 351 PCEP | BGP-LS|PCEP | PCEP 352 | | | 353 | +v-+ | 354 +------------------+R3+-------------------+ 355 PF12 | +--+ | PF22 356 PF11 | | PF21 357 +---+ +v-+ +--+ +--+ +-v+ +---+ 358 |SW1+-------+R1+----------+R5+----------+R6+---------+R7+--------+SW2| 359 +---+ ++-+ +--+ +--+ +-++ +---+ 360 | | 361 | | 362 | +--+ +--+ | 363 +------------+R2+----------+R4+-----------+ 365 Figure 3: CCDR framework for Multi-BGP deployment 367 6. PCEP Extension for Key Parameters Delivery 369 The PCEP protocol needs to be extended to transfer the following key 370 parameters: 372 o Peer addresses pair that is used to build the BGP session 374 o Advertised prefixes and their associated BGP session. 376 o Explicit route information to BGP next hop of advertised prefixes. 378 Once the router receives such information, it should establish the 379 BGP session with the peer appointed in the PCEP message, advertise 380 the prefixes that contained in the corresponding PCEP message, and 381 build the end to end dedicated path hop by hop. 383 The dedicated path is preferred by making sure that the explicit 384 route created by PCE has the higher priority (lower route preference) 385 than the route information created by any other protocols (including 386 the route manually configured). 388 All above dynamically created states (BGP sessions, Prefix advertised 389 prefix, Explicit route) will be cleared on the expiration of state 390 timeout interval which is based on the existing Stateful PCE 391 [RFC8231] and PCECC [RFC8283] mechanism. 393 Details of communications between PCEP and BGP subsystems in router's 394 control plane are out of scope of this draft and will be described in 395 separate draft [I-D.ietf-pce-pcep-extension-native-ip] . 397 7. Deployment Consideration 399 7.1. Scalability 401 In CCDR framework, PCE needs only influence the edge routers for the 402 prefixes advertisement via the multiple BGP sessions deployment. The 403 route information for these prefixes within the on-path routers were 404 distributed via the BGP protocol. 406 For multiple domains deployment, the PCE or the pool of PCEs that 407 reponsible for these domains need only control the edge router to 408 build multiple EBGP sessions, all other procedures are the same that 409 in one domain. 411 Unlike the solution from BGP Flowspec, the on-path router need only 412 keep the specific policy routes to the BGP next-hop of the 413 differentiate prefixes, not the specific routes to the prefixes 414 themselves. This can lessen the burden from the table size of policy 415 based routes for the on-path routers, and has more expandability when 416 comparing with the solution from BGP flowspec or Openflow. For 417 example, if we want to differentiate 1000 prefixes from the normal 418 traffic, CCDR needs only one explicit peer route in every on-path 419 router, but the BGP flowspec or Openflow needs 1000 policy routes on 420 them. 422 7.2. High Availability 424 The CCDR framework is based on the distributed IP protocol. If the 425 PCE failed, the forwarding plane will not be impacted, as the BGP 426 session between all devices will not flap, and the forwarding table 427 will remain unchanged. 429 If one node on the optimal path is failed, the priority traffic will 430 fall over to the best-effort forwarding path. One can even design 431 several assurance paths to load balance/hot-standby the priority 432 traffic to meet the path failure situation. 434 For high availability of PCE/SDN-controller, operator should rely on 435 existing high availability solutions for SDN controller, such as 436 clustering technology and deployment. 438 7.3. Incremental deployment 440 Not every router within the network will support the PCEP extension 441 that defined in [I-D.ietf-pce-pcep-extension-native-ip] 442 simultaneously. 444 For such situations, router on the edge of domain can be upgraded 445 first, and then the traffic can be assured between different domains. 446 Within each domain, the traffic will be forwarded along the best- 447 effort path. Service provider can selectively upgrade the routers on 448 each domain in sequence. 450 8. Security Considerations 452 A PCE needs to assure calculation of E2E path based on the status of 453 network and the service requirements in real-time. 455 The PCE need consider the explicit route deployment order (for 456 example, from tail router to head router) to eliminate the possible 457 transient traffic loop. 459 The setup of BGP session, prefix advertisement and explicit peer 460 route establishment are all controlled by the PCE. To prevent the 461 bogus PCE to send harmful messages to the network nodes, the network 462 devices should authenticate the validity of PCE and keep secures 463 communication channel between them. Mechanism described in [RFC8253] 464 should be used to avoid such situation. 466 CCDR framework does not require the change of forward behavior on the 467 underlay devices, then there will no additional security impact on 468 the devices. 470 9. IANA Considerations 472 This document does not require any IANA actions. 474 10. Acknowledgement 476 The author would like to thank Deborah Brungard, Adrian Farrel, 477 Vishnu Beeram, Lou Berger, Dhruv Dhody, Raghavendra Mallya , Mike 478 Koldychev, Haomian Zheng, Penghui Mi, Shaofu Peng and Jessica Chen 479 for their supports and comments on this draft. 481 11. References 483 11.1. Normative References 485 [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route 486 Reflection: An Alternative to Full Mesh Internal BGP 487 (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006, 488 . 490 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 491 Element (PCE)-Based Architecture", RFC 4655, 492 DOI 10.17487/RFC4655, August 2006, 493 . 495 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 496 Element (PCE) Communication Protocol Generic 497 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 498 2006, . 500 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 501 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 502 DOI 10.17487/RFC5440, March 2009, 503 . 505 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 506 S. Ray, "North-Bound Distribution of Link-State and 507 Traffic Engineering (TE) Information Using BGP", RFC 7752, 508 DOI 10.17487/RFC7752, March 2016, 509 . 511 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 512 Computation Element Communication Protocol (PCEP) 513 Extensions for Stateful PCE", RFC 8231, 514 DOI 10.17487/RFC8231, September 2017, 515 . 517 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 518 "PCEPS: Usage of TLS to Provide a Secure Transport for the 519 Path Computation Element Communication Protocol (PCEP)", 520 RFC 8253, DOI 10.17487/RFC8253, October 2017, 521 . 523 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 524 Computation Element Communication Protocol (PCEP) 525 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 526 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 527 . 529 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 530 Architecture for Use of PCE and the PCE Communication 531 Protocol (PCEP) in a Network with Central Control", 532 RFC 8283, DOI 10.17487/RFC8283, December 2017, 533 . 535 [RFC8735] Wang, A., Huang, X., Kou, C., Li, Z., and P. Mi, 536 "Scenarios and Simulation Results of PCE in a Native IP 537 Network", RFC 8735, DOI 10.17487/RFC8735, February 2020, 538 . 540 11.2. Informative References 542 [I-D.ietf-pce-pcep-extension-native-ip] 543 Wang, A., Khasanov, B., Fang, S., and C. Zhu, "PCEP 544 Extension for Native IP Network", draft-ietf-pce-pcep- 545 extension-native-ip-05 (work in progress), February 2020. 547 Authors' Addresses 549 Aijun Wang 550 China Telecom 551 Beiqijia Town, Changping District 552 Beijing 102209 553 China 555 Email: wangaj3@chinatelecom.cn 557 Boris Khasanov 558 Huawei Technologies 559 Moskovskiy Prospekt 97A 560 St.Petersburg 196084 561 Russia 563 Email: khasanov.boris@huawei.com 564 Quintin Zhao 565 Etheric Networks 566 1009 S CLAREMONT ST 567 SAN MATEO, CA 94402 568 USA 570 Email: qzhao@ethericnetworks.com 572 Huaimo Chen 573 Futurewei 574 Boston, MA 575 USA 577 Email: huaimo.chen@futurewei.com