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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TEAS Working Group Q. Zhao 3 Internet-Draft Z. Li 4 Intended status: Informational B. Khasanov 5 Expires: September 9, 2020 D. Dhody 6 Huawei Technologies 7 K. Ke 8 Tencent Holdings Ltd. 9 L. Fang 10 Expedia, Inc. 11 C. Zhou 12 Cisco Systems 13 B. Zhang 14 Telus Communications 15 A. Rachitskiy 16 Mobile TeleSystems JLLC 17 A. Gulida 18 LLC "Lifetech" 19 March 8, 2020 21 The Use Cases for Path Computation Element (PCE) as a Central Controller 22 (PCECC). 23 draft-ietf-teas-pcecc-use-cases-05 25 Abstract 27 The Path Computation Element (PCE) is a core component of a Software- 28 Defined Networking (SDN) system. It can compute optimal paths for 29 traffic across a network and can also update the paths to reflect 30 changes in the network or traffic demands. PCE was developed to 31 derive paths for MPLS Label Switched Paths (LSPs), which are supplied 32 to the head end of the LSP using the Path Computation Element 33 Communication Protocol (PCEP). 35 SDN has a broader applicability than signaled MPLS traffic-engineered 36 (TE) networks, and the PCE may be used to determine paths in a range 37 of use cases including static LSPs, segment routing (SR), Service 38 Function Chaining (SFC), and most forms of a routed or switched 39 network. It is, therefore, reasonable to consider PCEP as a control 40 protocol for use in these environments to allow the PCE to be fully 41 enabled as a central controller. 43 This document describes general considerations for PCECC deployment 44 and examines its applicability and benefits, as well as its 45 challenges and limitations, through a number of use cases. PCEP 46 extensions required for stateful PCE usage are covered in separate 47 documents. 49 This is a living document to catalogue the use cases for PCECC. 50 There is currently no intention to publish this work as an RFC. 52 Requirements Language 54 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 55 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 56 "OPTIONAL" in this document are to be interpreted as described in BCP 57 14 [RFC2119] [RFC8174] when, and only when, they appear in all 58 capitals, as shown here. 60 Status of This Memo 62 This Internet-Draft is submitted in full conformance with the 63 provisions of BCP 78 and BCP 79. 65 Internet-Drafts are working documents of the Internet Engineering 66 Task Force (IETF). Note that other groups may also distribute 67 working documents as Internet-Drafts. The list of current Internet- 68 Drafts is at https://datatracker.ietf.org/drafts/current/. 70 Internet-Drafts are draft documents valid for a maximum of six months 71 and may be updated, replaced, or obsoleted by other documents at any 72 time. It is inappropriate to use Internet-Drafts as reference 73 material or to cite them other than as "work in progress." 75 This Internet-Draft will expire on September 9, 2020. 77 Copyright Notice 79 Copyright (c) 2020 IETF Trust and the persons identified as the 80 document authors. All rights reserved. 82 This document is subject to BCP 78 and the IETF Trust's Legal 83 Provisions Relating to IETF Documents 84 (https://trustee.ietf.org/license-info) in effect on the date of 85 publication of this document. Please review these documents 86 carefully, as they describe your rights and restrictions with respect 87 to this document. Code Components extracted from this document must 88 include Simplified BSD License text as described in Section 4.e of 89 the Trust Legal Provisions and are provided without warranty as 90 described in the Simplified BSD License. 92 Table of Contents 94 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 95 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 96 3. Application Scenarios . . . . . . . . . . . . . . . . . . . . 4 97 3.1. Use Cases of PCECC for Label Management . . . . . . . . . 4 98 3.2. Using PCECC for SR . . . . . . . . . . . . . . . . . . . 6 99 3.2.1. PCECC SID Allocation . . . . . . . . . . . . . . . . 7 100 3.2.2. Use Cases of PCECC for SR Best Effort (BE) Path . . . 8 101 3.2.3. Use Cases of PCECC for SR Traffic Engineering (TE) 102 Path . . . . . . . . . . . . . . . . . . . . . . . . 8 103 3.3. Use Cases of PCECC for TE LSP . . . . . . . . . . . . . . 9 104 3.3.1. PCECC Load Balancing (LB) Use Case . . . . . . . . . 11 105 3.3.2. PCECC and Inter-AS TE . . . . . . . . . . . . . . . . 13 106 3.4. Use Cases of PCECC for Multicast LSPs . . . . . . . . . . 16 107 3.4.1. Using PCECC for P2MP/MP2MP LSPs' Setup . . . . . . . 16 108 3.4.2. Use Cases of PCECC for the Resiliency of P2MP/MP2MP 109 LSPs . . . . . . . . . . . . . . . . . . . . . . . . 17 110 3.5. Use Cases of PCECC for LSP in the Network Migration . . . 19 111 3.6. Use Cases of PCECC for L3VPN and PWE3 . . . . . . . . . . 21 112 3.7. Using PCECC for Traffic Classification Information . . . 22 113 3.8. Use Cases of PCECC for SRv6 . . . . . . . . . . . . . . . 22 114 3.9. Use Cases of PCECC for SFC . . . . . . . . . . . . . . . 24 115 3.10. Use Cases of PCECC for Native IP . . . . . . . . . . . . 24 116 3.11. Use Cases of PCECC for Local Protection (RSVP-TE) . . . . 25 117 3.12. Use Cases of PCECC for BIER . . . . . . . . . . . . . . . 25 118 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 119 5. Security Considerations . . . . . . . . . . . . . . . . . . . 26 120 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 121 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 122 7.1. Normative References . . . . . . . . . . . . . . . . . . 26 123 7.2. Informative References . . . . . . . . . . . . . . . . . 26 124 Appendix A. Using reliable P2MP TE based multicast delivery for 125 distributed computations (MapReduce-Hadoop) . . . . 30 126 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 128 1. Introduction 130 An Architecture for Use of PCE and PCEP [RFC5440] in a Network with 131 Central Control [RFC8283] describes SDN architecture where the Path 132 Computation Element (PCE) determines paths for variety of different 133 usecases, with PCEP as a general southbound communication protocol 134 with all the nodes along the path.. 136 [I-D.ietf-pce-pcep-extension-for-pce-controller] introduces the 137 procedures and extensions for PCEP to support the PCECC architecture 138 [RFC8283]. 140 This draft describes the various usecases for the PCECC architecture. 142 This is a living document to catalogue the use cases for PCECC. 143 There is currently no intention to publish this work as an RFC. 145 2. Terminology 147 The following terminology is used in this document. 149 IGP: Interior Gateway Protocol. Either of the two routing 150 protocols, Open Shortest Path First (OSPF) or Intermediate System 151 to Intermediate System (IS-IS). 153 PCC: Path Computation Client: any client application requesting a 154 path computation to be performed by a Path Computation Element. 156 PCE: Path Computation Element. An entity (component, application, 157 or network node) that is capable of computing a network path or 158 route based on a network graph and applying computational 159 constraints. 161 PCECC: PCE as a central controller. Extension of PCE to support SDN 162 functions as per [RFC8283]. 164 TE: Traffic Engineering. 166 3. Application Scenarios 168 In the following sections, several use cases are described, 169 showcasing scenarios that benefit from the deployment of PCECC. 171 3.1. Use Cases of PCECC for Label Management 173 As per [RFC8283], in some cases, the PCE-based controller can take 174 responsibility for managing some part of the MPLS label space for 175 each of the routers that it controls, and it may taker wider 176 responsibility for partitioning the label space for each router and 177 allocating different parts for different uses, communicating the 178 ranges to the router using PCEP. 180 [I-D.ietf-pce-pcep-extension-for-pce-controller] describe a mode 181 where LSPs are provisioned as explicit label instructions at each hop 182 on the end-to-end path. Each router along the path must be told what 183 label forwarding instructions to program and what resources to 184 reserve. The controller uses PCEP to communicate with each router 185 along the path of the end-to-end LSP. For this to work, the PCE- 186 based controller will take responsibility for managing some part of 187 the MPLS label space for each of the routers that it controls. An 188 extension to PCEP could be done to allow a PCC to inform the PCE of 189 such a label space to control. 191 [RFC8664] specifies extensions to PCEP that allow a stateful PCE to 192 compute, update or initiate SR-TE paths. 193 [I-D.zhao-pce-pcep-extension-pce-controller-sr] describes the 194 mechanism for PCECC to allocate and provision the node/prefix/ 195 adjacency label (SID) via PCEP. To make such allocation PCE needs to 196 be aware of the label space from Segment Routing Global Block (SRGB) 197 or Segment Routing Local Block (SRLB) [RFC8402] of the node that it 198 controls. A mechanism for a PCC to inform the PCE of such a label 199 space to control is needed within PCEP. The full SRGB/SRLB of a node 200 could be learned via existing IGP or BGP-LS mechanism too. 202 [I-D.li-pce-controlled-id-space] defines a PCEP extension to support 203 advertisement of the MPLS label space to the PCE to control. 205 There have been various proposals for Global Labels, the PCECC 206 architecture could be used as means to learn the label space of 207 nodes, and could also be used to determine and provision the global 208 label range. 210 +------------------------------+ +------------------------------+ 211 | PCE DOMAIN 1 | | PCE DOMAIN 2 | 212 | +--------+ | | +--------+ | 213 | | | | | | | | 214 | | PCECC1 | ---------PCEP---------- | PCECC2 | | 215 | | | | | | | | 216 | | | | | | | | 217 | +--------+ | | +--------+ | 218 | ^ ^ | | ^ ^ | 219 | / \ PCEP | | PCEP / \ | 220 | V V | | V V | 221 | +--------+ +--------+ | | +--------+ +--------+ | 222 | |NODE 11 | | NODE 1n| | | |NODE 21 | | NODE 2n| | 223 | | | ...... | | | | | | ...... | | | 224 | | PCECC | | PCECC | | | | PCECC | |PCECC | | 225 | |Enabled | | Enabled| | |Enabled | |Enabled | | 226 | +--------+ +--------+ | | +--------+ +--------+ | 227 | | | | 228 +------------------------------+ +------------------------------+ 230 Figure 1: PCECC for Label Management 232 o PCC would advertise the PCECC capability to the PCE (central 233 controller-PCECC) 234 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 236 o The PCECC could also learn the label range set aside by the PCC 237 ([I-D.li-pce-controlled-id-space]). 239 o Optionally, the PCECC could determine the shared MPLS global label 240 range for the network. 242 o In the case that the shared global label range need to be 243 negotiated across multiple domains, the central controllers of 244 these domains would also need to negotiate a common global 245 label range across domains. 247 o The PCECC would need to set the shared global label range to 248 all PCC nodes in the network. 250 3.2. Using PCECC for SR 252 Segment Routing (SR) leverages the source routing paradigm. Using 253 SR, a source node steers a packet through a path without relying on 254 hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is 255 specified as an ordered list of instructions called "segments". Each 256 segment is an instruction to route the packet to a specific place in 257 the network, or to perform a specific service on the packet. A 258 database of segments can be distributed through the network using a 259 routing protocol (such as IS-IS or OSPF) or by any other means. PCEP 260 (and PCECC) could be one such means. 262 [RFC8664] specify the SR specific PCEP extensions. PCECC may further 263 use PCEP protocol for SR SID (Segment Identifier) distribution to the 264 SR nodes (PCC) with some benefits. If the PCECC allocates and 265 maintains the SID in the network for the nodes and adjacencies; and 266 further distributes them to the SR nodes directly via the PCEP 267 session has some advantage over the configurations on each SR node 268 and flooding via IGP, especially in a SDN environment. 270 When the PCECC is used for the distribution of the node segment ID 271 and adjacency segment ID, the node segment ID is allocated from the 272 SRGB of the node. For the allocation of adjacency segment ID, the 273 allocation is from the SRLB of the node as described in 274 [I-D.zhao-pce-pcep-extension-pce-controller-sr]. 276 [RFC8355] identifies various protection and resiliency usecases for 277 SR. Path protection lets the ingress node be in charge of the 278 failure recovery (used for SR-TE). Also protection can be performed 279 by the node adjacent to the failed component, commonly referred to as 280 local protection techniques or fast-reroute (FRR) techniques. In 281 case of PCECC, the protection paths can be pre-computed and setup by 282 the PCE. 284 The following example illustrate the use case where the node SID and 285 adjacency SID are allocated by the PCECC. 287 192.0.2.1/32 288 +----------+ 289 | R1(1001) | 290 +----------+ 291 | 292 +----------+ 293 | R2(1002) | 192.0.2.2/32 294 +----------+ 295 * | * * 296 * | * * 297 *link1| * * 298 192.0.2.4/32 * | *link2 * 192.0.2.5/32 299 +-----------+ 9001| * +-----------+ 300 | R4(1004) | | * | R5(1005) | 301 +-----------+ | * +-----------+ 302 * | *9003 * + 303 * | * * + 304 * | * * + 305 +-----------+ +-----------+ 306 192.0.2.3/32 | R3(1003) | |R6(1006) |192.0.2.6/32 307 +-----------+ +-----------+ 308 | 309 +-----------+ 310 | R8(1008) | 192.0.2.8/32 311 +-----------+ 313 3.2.1. PCECC SID Allocation 315 Each node (PCC) is allocated a node-SID by the PCECC. The PCECC 316 needs to update the label map of each node to all the nodes in the 317 domain. On receiving the label map, each node (PCC) uses the local 318 routing information to determine the next-hop and download the label 319 forwarding instructions accordingly. The forwarding behavior and the 320 end result is same as IGP based Node-SID in SR. Thus, from anywhere 321 in the domain, it enforces the ECMP-aware shortest-path forwarding of 322 the packet towards the related node. 324 For each adjacency in the network, PCECC can allocate an Adj-SID. 325 The PCECC sends PCInitiate message to update the label map of each 326 Adj to the corresponding nodes in the domain. Each node (PCC) 327 download the label forwarding instructions accordingly. The 328 forwarding behavior and the end result is similar to IGP based "Adj- 329 SID" in SR. 331 The various mechanism are described in 332 [I-D.zhao-pce-pcep-extension-pce-controller-sr]. 334 3.2.2. Use Cases of PCECC for SR Best Effort (BE) Path 336 In this mode of the solution, the PCECC just need to allocate the 337 node segment ID and adjacency ID (without calculating the explicit 338 path for the SR path). The ingress of the forwarding path just need 339 to encapsulate the destination node segment ID on top of the packet. 340 All the intermediate nodes will forward the packet based on the 341 destination node SID. It is similar to the LDP LSP. 343 R1 may send a packet to R8 simply by pushing an SR header with 344 segment list {1008} (Node SID for R8). The path would be the based 345 on the routing/nexthop calculation on the routers. 347 3.2.3. Use Cases of PCECC for SR Traffic Engineering (TE) Path 349 SR-TE paths may not follow an IGP SPT. Such paths may be chosen by a 350 PCECC and provisioned on the ingress node of the SR-TE path. The SR 351 header consists of a list of SIDs (or MPLS labels). The header has 352 all necessary information so that, the packets can be guided from the 353 ingress node to the egress node of the path; hence, there is no need 354 for any signaling protocol. For the case where strict traffic 355 engineering path is needed, all the adjacency SID are stacked, 356 otherwise a combination of node-SID or adj-SID can be used for the 357 SR-TE paths. 359 Note that the bandwidth reservations is only guaranteed at controller 360 and through the enforce of the bandwidth admission control. As for 361 the RSVP-TE LSP case, the control plane signaling also does the link 362 bandwidth reservation in each hop of the path. 364 The SR traffic engineering path examples are explained as bellow: 366 Note that the node SID for each node is allocated from the SRGB and 367 adjacency SID for each link are allocated from the SRLB for each 368 node. 370 Example 1: 372 R1 may send a packet P1 to R8 simply by pushing an SR header with 373 segment list {1008}. Based on the best path, it could be: 374 R1-R2-R3-R8. 376 Example 2: 378 R1 may send a packet P2 to R8 by pushing an SR header with segment 379 list {1002, 9001, 1008}. The path should be: R1-R2-link1-R3-R8. 381 Example 3: 383 R1 may send a packet P3 to R8 via R4 by pushing an SR header with 384 segment list {1004, 1008}. The path could be : R1-R2-R4-R3-R8 386 The local protection examples for SR TE path are explained below: 388 Example 4: local link protection: 390 o R1 may send a packet P4 to R8 by pushing an SR header with segment 391 list {1002, 9001, 1008}. The path should be: R1-R2-link1-R3-R8. 393 o When node R2 receives the packet from R1 which has the header of 394 link1-R3-R8, and also find out there is a link failure of link1, 395 then the R2 can enforce the traffic over the bypass to send out 396 the packet with header of R3-R8 through link2. 398 Example 5: local node protection: 400 o R1 may send a packet P5 to R8 by pushing an SR header with segment 401 list {1004, 1008}. The path could be : R1-R2-R4-R3-R8. 403 o When node R2 receives the packet from R1 which has the header of 404 {1004, 1008}, and also finds out there is a node failure for 405 node4, then it can enforce the traffic over the bypass and send 406 out the packet with header of {1005, 1008} to node5 instead of 407 node4. 409 3.3. Use Cases of PCECC for TE LSP 411 In the Section 3.2 the case of SR path via PCECC is discussed. 412 Although those cases give the simplicity and scalability, but there 413 are existing functionalities for the traffic engineering path such as 414 the bandwidth guarantee, monitoring where SR based solution are 415 complex. Also there are cases where the depth of the label stack is 416 an issue for existing deployment and certain vendors. 418 So to address these issues, PCECC architecture also support the TE 419 LSP functionalities. To achieve this, the existing PCEP can be used 420 to communicate between the PCECC and nodes along the path. This is 421 similar to static LSPs, where LSPs can be provisioned as explicit 422 label instructions at each hop on the end-to-end path. Each router 423 along the path must be told what label- forwarding instructions to 424 program and what resources to reserve. The PCE-based controller 425 keeps a view of the network and determines the paths of the end-to- 426 end LSPs, and the controller uses PCEP to communicate with each 427 router along the path of the end-to-end LSP. 429 192.0.2.1/32 430 +----------+ 431 | R1 | 432 +----------+ 433 | | 434 |link1 | 435 | |link2 436 +----------+ 437 | R2 | 192.0.2.2/32 438 +----------+ 439 link3 * | * * link4 440 * | * * 441 *link5| * * 442 192.0.2.4/32 * | *link6 * 192.0.2.5/32 443 +-----------+ | * +-----------+ 444 | R4 | | * | R5 | 445 +-----------+ | * +-----------+ 446 * | * * + 447 link10 * | * *link7 + 448 * | * * + 449 +-----------+ +-----------+ 450 192.0.2.3/32 | R3 | |R6 |192.0.2.6/32 451 +-----------+ +-----------+ 452 | | 453 |link8 | 454 | |link9 455 +-----------+ 456 | R8 | 192.0.2.8/32 457 +-----------+ 459 Figure 2: PCECC TE LSP Setup Example 461 o Based on path computation request / delegation or PCE initiation, 462 the PCECC receives the PCECC request with constraints and 463 optimization criteria. 465 o PCECC would calculate the optimal path according to given 466 constrains (e.g. bandwidth). 468 o PCECC would provision each node along the path and assign incoming 469 and outgoing labels from R1 to R8 with the path: {R1, link1, 470 1001}, {1001, R2, link3, 2003], {2003, R4, link10, 4010}, {4010, 471 R3, link8, 3008}, {3008, R8}. 473 o For the end to end protection, PCECC program each node along the 474 path from R1 to R8 with the secondary path: {R1, link2, 1002}, 475 {1002, R2, link4, 2004], {2004, R5, link7, 5007}, {5007, R3, 476 link9, 3009}, {3009, R8}. 478 o It is also possible to have a bypass path for the local protection 479 setup by the PCECC. For example, the primary path as above, then 480 to protect the node R4 locally, PCECC can program the bypass path 481 like this: {R2, link5, 2005}, {2005, R3}. By doing this, the node 482 R4 is locally protected at R2. 484 3.3.1. PCECC Load Balancing (LB) Use Case 486 Very often many service providers use TE tunnels for solving issues 487 with non-deterministic paths in their networks. One example of such 488 applications is usage of TEs in the mobile backhaul (MBH). Consider 489 the following topology - 491 TE1 --------------> 492 +---------+ +--------+ +--------+ +--------+ +------+ +---+ 493 | Access |----| Access |----| AGG 1 |----| AGG N-1|----|Core 1|--|SR1| 494 | SubNode1| | Node 1 | +--------+ +--------+ +------+ +---+ 495 +---------+ +--------+ | | | ^ | 496 | Access | Access | AGG Ring 1 | | | 497 | SubRing 1 | Ring 1 | | | | | 498 +---------+ +--------+ +--------+ | | | 499 | Access | | Access | | AGG 2 | | | | 500 | SubNode2| | Node 2 | +--------+ | | | 501 +---------+ +--------+ | | | | | 502 | | | | | | | 503 | | | +----TE2----|-+ | 504 +---------+ +--------+ +--------+ +--------+ +------+ +---+ 505 | Access | | Access |----| AGG 3 |----| AGG N |----|Core N|--|SRn| 506 | SubNodeN|----| Node N | +--------+ +--------+ +------+ +---+ 507 +---------+ +--------+ 509 This MBH architecture uses L2 access rings and sub-rings. L3 starts 510 at the aggregation layer. For the sake of simplicity, the figure 511 shows only one access sub-ring, access ring and aggregation ring 512 (AGG1...AGGN), connected by Nx10GE interfaces. Aggregation domain 513 runs its own IGP. There are two Egress routers (AGG N-1,AGG N) that 514 are connected to the Core domain via L2 interfaces. Core also have 515 connections to service routers, RSVP-TEs are used for MPLS transport 516 inside the ring. There could be at least 2 tunnels (one way) from 517 each AGG router to egress AGG routers. There are also many L2 access 518 rings connected to AGG routers. 520 Service deployment made by means of either L2VPNs (VPLS) or L3VPNs. 521 Those services use MPLS TE as transport towards egress AGG routers. 522 TE tunnels could be also used as transport towards service routers in 523 case of seamless MPLS based architecture in the future. 525 There is a need to solve the following tasks: 527 o Perform automatic load-balance amongst TE tunnels according to 528 current traffic load. 530 o TE bandwidth (BW) management: Provide guaranteed BW for specific 531 service: HSI, IPTV, etc., provide time-based BW reservation (BoD) 532 for other services. 534 o Simplify development of TE tunnels by automation without any 535 manual intervention. 537 o Provide flexibility for Service Router placement (anywhere in the 538 network by creation of transport LSPs to them). 540 Since other tasks are already considered by other PCECC use cases, in 541 this section, the focus is on load balancing (LB) task. LB task 542 could be solved by means of PCECC in the following way: 544 o After application or network service or operator can ask SDN 545 controller (PCECC) for LSP based LB between AGG X and AGG N/AGG 546 N-1 (egress AGG routers which have connections to core) via North 547 Bound Interface (NBI). Each of these would have associated 548 constrains (i.e. Path Setup Type (PST), bandwidth, inclusion or 549 exclusion specific links or nodes, number of paths, objective 550 function (OF), need for disjoint LSP paths etc.). 552 o PCECC could calculate multiple (Say N) LSPs according to given 553 constrains, calculation is based on results of Objective Function 554 (OF) [RFC5541], constraints, endpoints, same or different 555 bandwidth (BW) , different links (in case of disjoint paths) and 556 other constrains. 558 o Depending on given LSP Path setup type (PST), PCECC would use 559 download instructions to the PCC. At this stage it is assumed the 560 PCECC is aware of the label space it controls and in case of SR 561 the SID allocation and distribution is already done. 563 o PCECC would send PCInitiate PCEP message [RFC8281] towards ingress 564 AGG X router(PCC) for each of N LSPs and receives PCRpt PCEP 565 message [RFC8231] back from PCCs. If the PST is PCECC-SR, the 566 PCECC would include the SID stack as per [RFC8664]. If the PST is 567 PCECC (basic), then the PCECC would assigns labels along the 568 calculated path; and set up the path by sending central controller 569 instructions in PCEP message to each node along the path of the 570 LSP as per [I-D.ietf-pce-pcep-extension-for-pce-controller] and 571 then send PCUpd message to the ingress AGG X router with 572 information about new LSP and AGG X(PCC) would respond with PCRpt 573 with LSP status. 575 o AGG X as ingress router now have N LSPs towards AGG N and AGG N-1 576 which are available for installing to router's forwarding and LB 577 of traffic between them. Traffic distribution between those LSPs 578 depends on particular realization of hash-function on that router. 580 o Since PCECC is aware of TEDB (TE state) and LSP-DB, it can manage 581 and prevent possible over-subscriptions and limit number of 582 available LB states. Via PCECC mechanism the control can take 583 quick actions into the network by directly provisioning the 584 central control instructions. 586 3.3.2. PCECC and Inter-AS TE 588 There are various signaling options for establishing Inter-AS TE LSP: 589 contiguous TE LSP [RFC5151], stitched TE LSP [RFC5150], nested TE LSP 590 [RFC4206]. 592 Requirements for PCE-based Inter-AS setup [RFC5376] describe the 593 approach and PCEP functionality that are needed for establishing 594 Inter-AS TE LSPs. 596 [RFC5376] also gives Inter- and Intra-AS PCE Reference Model that is 597 provided below in shorten form for the sake of simplicity. 599 Inter-AS Inter-AS 600 PCC <-->PCE1<--------->PCE2 601 :: :: :: 602 :: :: :: 603 R1----ASBR1====ASBR3---R3---ASBR5 604 | AS1 | | PCC | 605 | | | AS2 | 606 R2----ASBR2====ASBR4---R4---ASBR6 607 :: :: 608 :: :: 609 Intra-AS Intra-AS 610 PCE3 PCE4 612 Figure 3: Shorten form of Inter- and Intra-AS PCE Reference Model 613 [RFC5376] 615 The PCECC belonging to different domain can co-operate to setup 616 inter-AS TE LSP. The stateful H-PCE [I-D.ietf-pce-stateful-hpce] 617 mechanism could also be used to first establish a per-domain PCECC 618 LSP. These could be stitched together to form inter-AS TE LSP as 619 described in [I-D.dugeon-pce-stateful-interdomain]. 621 For the sake of simplicity, here after the focus is on a simplified 622 Inter-AS case when both AS1 and AS2 belong to the same service 623 provider administration. In that case Inter and Intra-AS PCEs could 624 be combined in one single PCE if such combined PCE performance is 625 enough for handling all path computation request and setup. There is 626 a potential to use a single PCE for both ASes if the scalability and 627 performance are enough. The PCE would require interfaces (PCEP and 628 BGP-LS) to both domains. PCECC redundancy mechanisms are described 629 in [RFC8283]. Thus routers in AS1 and AS2 (PCCs) can send PCEP 630 messages towards same PCECC. 632 +----BGP-LS------+ +------BGP-LS-----+ 633 | | | | 634 +-PCEP-|----++-+-------PCECC-----PCEP--++-+-|-------+ 635 +-:------|----::-:-+ +--::-:-|-------:---+ 636 | : | :: : | | :: : | : | 637 | : RR1 :: : | | :: : RR2 : | 638 | v v: : | LSP1 | :: v v | 639 | R1---------ASBR1=======================ASBR3--------R3 | 640 | | v : | | :v | | 641 | +----------ASBR2=======================ASBR4---------+ | 642 | | Region 1 : | | : Region 1 | | 643 |----------------:-| |--:-------------|--| 644 | | v | LSP2 | v | | 645 | +----------ASBR5=======================ASBR6---------+ | 646 | Region 2 | | Region 2 | 647 +------------------+ <--------------> +-------------------+ 648 MPLS Domain 1 Inter-AS MPLS Domain 2 649 <=======AS1=======> <========AS2=======> 651 Figure 4: Particular case of Inter-AS PCE 653 In a case of PCECC Inter-AS TE scenario where service provider 654 controls both domains (AS1 and AS2), each of them have own IGP and 655 MPLS transport. There is a need is to setup Inter-AS LSPs for 656 transporting different services on top of them (Voice, L3VPN etc.). 657 Inter-AS links with different capacity exist in several regions. The 658 task is not only to provision those Inter-AS LSPs with given 659 constrains but also calculate the path and pre-setup the backup 660 Inter-AS LSPs that will be used if primary LSP fails. 662 As per the Figure 4, LSP1 from R1 to R3 goes via ASBR1 and ASBR3, and 663 it is the primary Inter-AS LSP. R1-R3 LSP2 that go via ASBR5 and 664 ASBR6 is the backup one. In addition there could also be a bypass 665 LSP setup to protect against ASBR or inter-AS link failure. 667 After the addition of PCECC functionality to PCE (SDN controller), 668 PCECC based Inter-AS TE model SHOULD follow as PCECC usecase for TE 669 LSP as requirements of [RFC5376] with the following details: 671 o Since PCECC needs to know the topology of both domains AS1 and 672 AS2, PCECC could use BGP-LS peering with routers (or RRs) in both 673 domains. 675 o PCECC needs to PCEP connectivity towards all routers in both 676 domains (see also section 4 in [RFC5376]) in a similar manner as a 677 SDN controller. 679 o After operator's application or service orchestrator will create 680 request for tunnel creation of specific service, PCECC should 681 receive that request via NBI (NBI type is implementation 682 dependent, could be NETCONF/Yang, REST etc.). Then PCECC would 683 calculate the optimal path based on Objective Function (OF) and 684 given constraints (i.e. path setup type, bandwidth etc.), 685 including those from [RFC5376]: priority, AS sequence, preferred 686 ASBR, disjoint paths, protection. On this step we would have two 687 paths: R1-ASBR1-ASBR3-R3, R1-ASBR5-ASBR6-R3 689 o Depending on given LSP PST (PCECC or PCECC-SR), PCECC would use 690 central control download instructions to the PCC. At this stage 691 it is assumed the PCECC is aware of the label space it controls 692 and in case of SR the SID allocation and distribution is already 693 done. 695 o PCECC would send PCInitiate PCEP message [RFC8281] towards ingress 696 router R1 (PCC) in AS1 and receives PCRpt PCEP message [RFC8231] 697 back from PCC. If the PST is PCECC-SR, the PCECC would include 698 the SID stack as per [RFC8664]. It may also include binding SID 699 based on AS boundary. The backup SID stack could also be 700 installed at ingress but more importantly each node along the SR 701 path could also do local protection just based on the top segment. 702 If the PST is PCECC (basic), then the PCECC would assigns labels 703 along the calculated paths (R1-ASBR1-ASBR3-R3, R1-ASBR5-ASBR6-R3); 704 and set up the path by sending central controller instructions in 705 PCEP message to each node along the path of the LSPs as per 706 [I-D.ietf-pce-pcep-extension-for-pce-controller] and then send 707 PCUpd message to the ingress R1 router with information about new 708 LSPs and R1 would respond with PCRpt with LSP(s) status. 710 o After that step R1 now have primary and backup TEs (LSP1 and LSP2) 711 towards R3. It is up to router implementation how to make 712 switchover to backup LSP2 if LSP1 fails. 714 3.4. Use Cases of PCECC for Multicast LSPs 716 The current multicast LSPs are setup either using the RSVP-TE P2MP or 717 mLDP protocols. The setup of these LSPs may require manual 718 configurations and complex signaling when the protection is 719 considered. By using the PCECC solution, the multicast LSP can be 720 computed and setup through centralized controller which has the full 721 picture of the topology and bandwidth usage for each link. It not 722 only reduces the complex configurations comparing the distributed 723 RSVP-TE P2MP or mLDP signaling, but also it can compute the disjoint 724 primary path and secondary P2MP path efficiently. 726 3.4.1. Using PCECC for P2MP/MP2MP LSPs' Setup 728 It is assumed the PCECC is aware of the label space it controls for 729 all nodes and make allocations accordingly. 731 +----------+ 732 | R1 | Root node of the multicast LSP 733 +----------+ 734 |6000 735 +----------+ 736 Transit Node | R2 | 737 branch +----------+ 738 * | * * 739 9001* | * *9002 740 * | * * 741 +-----------+ | * +-----------+ 742 | R4 | | * | R5 | Transit Nodes 743 +-----------+ | * +-----------+ 744 * | * * + 745 9003* | * * +9004 746 * | * * + 747 +-----------+ +-----------+ 748 | R3 | | R6 | Leaf Node 749 +-----------+ +-----------+ 750 9005| 751 +-----------+ 752 | R8 | Leaf Node 753 +-----------+ 755 The P2MP examples are explained here, where R1 is root and R8 and R6 756 are the leaves. 758 o Based on the P2MP path computation request / delegation or PCE 759 initiation, the PCECC receives the PCECC request with constraints 760 and optimization criteria. 762 o PCECC would calculate the optimal P2MP path according to given 763 constrains (i.e.bandwidth). 765 o PCECC would provision each node along the path and assign incoming 766 and outgoing labels from R1 to {R6, R8} with the path: {R1, 6000}, 767 {6000, R2, {9001,9002}}, {9001, R4, 9003}, {9002, R5, 9004} {9003, 768 R3, 9005}, {9004, R6}, {9005, R8}. The main difference is in the 769 branch node instruction at R2 where two copies of packet are sent 770 towards R4 and R5 with 9001 and 9002 labels respectively. 772 The packet forwarding involves - 774 Step1: R1 may send a packet P1 to R2 simply by pushing an label of 775 6000 to the packet. 777 Step2: After R2 receives the packet with label 6000, it will 778 forwarding to R4 by swapping label to 9001 and by swapping label 779 of 9002 towards R5. 781 Step3: After R4 receives the packet with label 9001, it will 782 forwarding to R3 by swapping to 9003. After R5 receives the 783 packet with label 9002, it will forwarding to R6 by swapping to 784 9004. 786 Step4: After R3 receives the packet with label 9003, it will 787 forwarding to R8 by swapping to 9005 and when R5 receives the 788 packet with label 9004, it will swap to 9004 and send to R6. 790 Step5: Packet received at R8 and 9005 is popped; packet receives 791 at R6 and 9004 is popped. 793 3.4.2. Use Cases of PCECC for the Resiliency of P2MP/MP2MP LSPs 795 3.4.2.1. PCECC for the End-to-End Protection of the P2MP/MP2MP LSPs 797 In this section we describe the end-to-end managed path protection 798 service as well as the local protection with the operation management 799 in the PCECC network for the P2MP/MP2MP LSP. 801 An end-to-end protection principle can be applied for computing 802 backup P2MP or MP2MP LSPs. During computation of the primary 803 multicast trees, PCECC server may also take the computation of a 804 secondary tree into consideration. A PCE may compute the primary and 805 backup P2MP (or MP2MP) LSP together or sequentially. 807 +----+ +----+ 808 Root node of LSP | R1 |--| R11| 809 +----+ +----+ 810 / + 811 10/ +20 812 / + 813 +----------+ +-----------+ 814 Transit Node | R2 | | R3 | 815 +----------+ +-----------+ 816 | \ + + 817 | \ + + 818 10| 10\ +20 20+ 819 | \ + + 820 | \ + 821 | + \ + 822 +-----------+ +-----------+ Leaf Nodes 823 | R4 | | R5 | (Downstream LSR) 824 +-----------+ +-----------+ 826 In the example above, when the PCECC setup the primary multicast tree 827 from the root node R1 to the leaves, which is R1->R2->{R4, R5}, at 828 same time, it can setup the backup tree, which is R1->R11->R3->{R4, 829 R5}. Both the these two primary forwarding tree and secondary 830 forwarding tree will be downloaded to each routers along the primary 831 path and the secondary path. The traffic will be forwarded through 832 the R1->R2->{R4, R5} path normally, and when there is a node in the 833 primary tree fails (say R2), then the root node R1 will switch the 834 flow to the backup tree, which is R1->R11->R3->{R4, R5}. By using 835 the PCECC, the path computation and forwarding path downloading can 836 all be done without the complex signaling used in the P2MP RSVP-TE or 837 mLDP. 839 3.4.2.2. PCECC for the Local Protection of the P2MP/MP2MP LSPs 841 In this section we describe the local protection service in the PCECC 842 network for the P2MP/MP2MP LSP. 844 While the PCECC sets up the primary multicast tree, it can also build 845 the back LSP among PLR, the protected node, and MPs (the downstream 846 nodes of the protected node). In the cases where the amount of 847 downstream nodes are huge, this mechanism can avoid unnecessary 848 packet duplication on PLR and protect the network from traffic 849 congestion risk. 851 +------------+ 852 | R1 | Root Node 853 +------------+ 854 . 855 . 856 . 857 +------------+ Point of Local Repair/ 858 | R10 | Switchover Point 859 +------------+ (Upstream LSR) 860 / + 861 10/ +20 862 / + 863 +----------+ +-----------+ 864 Protected Node | R20 | | R30 | 865 +----------+ +-----------+ 866 | \ + + 867 | \ + + 868 10| 10\ +20 20+ 869 | \ + + 870 | \ + 871 | + \ + 872 +-----------+ +-----------+ Merge Point 873 | R40 | | R50 | (Downstream LSR) 874 +-----------+ +-----------+ 875 . . 876 . . 878 In the example above, when the PCECC setup the primary multicast path 879 around the PLR node R10 to protect node R20, which is R10->R20->{R40, 880 R50}, at same time, it can setup the backup path R10->R30->{R40, 881 R50}. Both the these two primary forwarding path and secondary 882 bypass forwarding path will be downloaded to each routers along the 883 primary path and the secondary bypass path. The traffic will be 884 forwarded through the R10->R20->{R40, R50} path normally, and when 885 there is a node failure for node R20, then the PLR node R10 will 886 switch the flow to the backup path, which is R10->R30->{R40, R50}. 887 By using the PCECC, the path computation and forwarding path 888 downloading can all be done without the complex signaling used in the 889 P2MP RSVP-TE or mLDP. 891 3.5. Use Cases of PCECC for LSP in the Network Migration 893 One of the main advantages for PCECC solution is that it has backward 894 compatibility naturally since the PCE server itself can function as a 895 proxy node of MPLS network for all the new nodes which may no longer 896 support the signaling protocols. 898 As it is illustrated in the following example, the current network 899 could migrate to a total PCECC controlled network gradually by 900 replacing the legacy nodes. During the migration, the legacy nodes 901 still need to signal using the existing MPLS protocol such as LDP and 902 RSVP-TE, and the new nodes setup their portion of the forwarding path 903 through PCECC directly. With the PCECC function as the proxy of 904 these new nodes, MPLS signaling can populate through network as 905 normal. 907 Example described in this section is based on network configurations 908 illustrated using the following figure: 910 +------------------------------------------------------------------+ 911 | PCE DOMAIN | 912 | +-----------------------------------------------------+ | 913 | | PCECC | | 914 | +-----------------------------------------------------+ | 915 | ^ ^ ^ ^ | 916 | | PCEP | | PCEP | | 917 | V V V V | 918 | +--------+ +--------+ +--------+ +--------+ +--------+ | 919 | | NODE 1 | | NODE 2 | | NODE 3 | | NODE 4 | | NODE 5 | | 920 | | |...| |...| |...| |...| | | 921 | | Legacy |if1| Legacy |if2|Legacy |if3| PCECC |if4| PCECC | | 922 | | Node | | Node | |Enabled | |Enabled | | Enabled| | 923 | +--------+ +--------+ +--------+ +--------+ +--------+ | 924 | | 925 +------------------------------------------------------------------+ 927 Example: PCECC Initiated LSP Setup In the Network Migration 929 In this example, there are five nodes for the TE LSP from head end 930 (Node1) to the tail end (Node5). Where the Node4 and Node5 are 931 centrally controlled and other nodes are legacy nodes. 933 o Node1 sends a path request message for the setup of LSP 934 destinating to Node5. 936 o PCECC sends to node1 a reply message for LSP setup with the path: 937 (Node1, if1),(Node2, if2), (Node3, if3), (Node4, if4), Node5. 939 o Node1, Node2, Node3 will setup the LSP to Node5 using the local 940 labels as usual. Node 3 with help of PCECC could proxy the 941 signaling. 943 o Then the PCECC will program the out-segment of Node3, the in- 944 segment/ out-segment of Node4, and the in-segment for Node5. 946 3.6. Use Cases of PCECC for L3VPN and PWE3 948 As described in [RFC8283], various network services may be offered 949 over a network. These include protection services (including Virtual 950 Private Network (VPN) services (such as Layer 3 VPNs [RFC4364] or 951 Ethernet VPNs [RFC7432]); or Pseudowires [RFC3985]. Delivering 952 services over a network in an optimal way requires coordination in 953 the way that network resources are allocated to support the services. 954 A PCE-based central controller can consider the whole network and all 955 components of a service at once when planning how to deliver the 956 service. It can then use PCEP to manage the network resources and to 957 install the necessary associations between those resources. 959 In the case of L3VPN, VPN labels can be assigned and distributed 960 through the PCECC PCEP among the PE router instead of using the BGP 961 protocols. 963 Example described in this section is based on network configurations 964 illustrated using the following figure: 966 +-------------------------------------------+ 967 | PCE DOMAIN | 968 | +-----------------------------------+ | 969 | | PCECC | | 970 | +-----------------------------------+ | 971 | ^ ^ ^ | 972 |PWE3/L3VPN | PCEP PCEP|LSP PWE3/L3VPN|PCEP | 973 | V V V | 974 +--------+ | +--------+ +--------+ +--------+ | +--------+ 975 | CE | | | PE1 | | NODE x | | PE2 | | | CE | 976 | |...... | |...| |...| |.....| | 977 | Legacy | |if1 | PCECC |if2|PCCEC |if3| PCECC |if4 | Legacy | 978 | Node | | | Enabled| |Enabled | |Enabled | | | Node | 979 +--------+ | +--------+ +--------+ +--------+ | +--------+ 980 | | 981 +-------------------------------------------+ 983 Example: Using PCECC for L3VPN and PWE3 985 In the case PWE3, instead of using the LDP signaling protocols, the 986 label and port pairs assigned to each pseudowire can be assigned 987 through PCECC among the PE routers and the corresponding forwarding 988 entries will be distributed into each PE routers through the extended 989 PCEP protocols and PCECC mechanism. 991 3.7. Using PCECC for Traffic Classification Information 993 As described in [RFC8283], traffic classification is an important 994 part of traffic engineering. It is the process of looking at a 995 packet to determine how it should be treated as it is forwarded 996 through the network. It applies in many scenarios including MPLS 997 traffic engineering (where it determines what traffic is forwarded 998 onto which LSPs); segment routing (where it is used to select which 999 set of forwarding instructions to add to a packet); and SFC (where it 1000 indicates along which service function path a packet should be 1001 forwarded). In conjunction with traffic engineering, traffic 1002 classification is an important enabler for load balancing. Traffic 1003 classification is closely linked to the computational elements of 1004 planning for the network functions just listed because it determines 1005 how traffic load is balanced and distributed through the network. 1006 Therefore, selecting what traffic classification should be performed 1007 by a router is an important part of the work done by a PCECC. 1009 Instructions can be passed from the controller to the routers using 1010 PCEP. These instructions tell the routers how to map traffic to 1011 paths or connections. Refer [I-D.ietf-pce-pcep-flowspec]. 1013 Along with traffic classification, there are few more question that 1014 needs to be considered once the path is setup - 1016 o how to use it 1018 o Whether it is a virtual link 1020 o Whether to advertise it in the IGP as a virtual link 1022 o What bits of this information to signal to the tail end 1024 These are out of scope of this document. 1026 3.8. Use Cases of PCECC for SRv6 1028 As per [RFC8402], with Segment Routing (SR), a node steers a packet 1029 through an ordered list of instructions, called segments. Segment 1030 Routing can be applied to the IPv6 architecture with the Segment 1031 Routing Header (SRH) [I-D.ietf-6man-segment-routing-header]. A 1032 segment is encoded as an IPv6 address. An ordered list of segments 1033 is encoded as an ordered list of IPv6 addresses in the routing 1034 header. The active segment is indicated by the Destination Address 1035 of the packet. Upon completion of a segment, a pointer in the new 1036 routing header is incremented and indicates the next segment. 1038 As per [I-D.ietf-6man-segment-routing-header], an SRv6 Segment is a 1039 128-bit value. "SRv6 SID" or simply "SID" are often used as a 1040 shorter reference for "SRv6 Segment". Further details are in An 1041 illustration is provided in 1042 [I-D.filsfils-spring-srv6-network-programming] where SRv6 SID is 1043 represented as LOC:FUNCT. 1045 [I-D.ietf-pce-segment-routing-ipv6] extends [RFC8664] to support SR 1046 for IPv6 data plane. Further a PCECC could be extended to support 1047 SRv6 SID allocation and distribution. 1049 2001:db8::1 1050 +----------+ 1051 | R1 | 1052 +----------+ 1053 | 1054 +----------+ 1055 | R2 | 2001:db8::2 1056 +----------+ 1057 * | * * 1058 * | * * 1059 *link1| * * 1060 2001:db8::4 * | *link2 * 2001:db8::5 1061 +-----------+ | * +-----------+ 1062 | R4 | | * | R5 | 1063 +-----------+ | * +-----------+ 1064 * | * * + 1065 * | * * + 1066 * | * * + 1067 +-----------+ +-----------+ 1068 2001:db8::3 | R3 | |R6 |2001:db8::6 1069 +-----------+ +-----------+ 1070 | 1071 +-----------+ 1072 | R8 | 2001:db8::8 1073 +-----------+ 1075 In this case, PCECC could assign the SRv6 SID (in form of a IPv6 1076 address) to be used for node and adjacency. Later SRv6 path in form 1077 of list of SRv6 SID could be used at the ingress. Some examples - 1079 o SRv6 SID-List={2001:db8::8} - The best path towards R8 1081 o SRv6 SID-List={2001:db8::5, 2001:db8::8} - The path towards R8 via 1082 R5 1084 3.9. Use Cases of PCECC for SFC 1086 Service Function Chaining (SFC) is described in [RFC7665]. It is the 1087 process of directing traffic in a network such that it passes through 1088 specific hardware devices or virtual machines (known as service 1089 function nodes) that can perform particular desired functions on the 1090 traffic. The set of functions to be performed and the order in which 1091 they are to be performed is known as a service function chain. The 1092 chain is enhanced with the locations at which the service functions 1093 are to be performed to derive a Service Function Path (SFP). Each 1094 packet is marked as belonging to a specific SFP, and that marking 1095 lets each successive service function node know which functions to 1096 perform and to which service function node to send the packet next. 1097 To operate an SFC network, the service function nodes must be 1098 configured to understand the packet markings, and the edge nodes must 1099 be told how to mark packets entering the network. Additionally, it 1100 may be necessary to establish tunnels between service function nodes 1101 to carry the traffic. Planning an SFC network requires load 1102 balancing between service function nodes and traffic engineering 1103 across the network that connects them. As per [RFC8283], these are 1104 operations that can be performed by a PCE-based controller, and that 1105 controller can use PCEP to program the network and install the 1106 service function chains and any required tunnels. 1108 PCECC can play the role for setting the traffic classification rules 1109 at the classifier as well as downloading the forwarding instructions 1110 to the SFFs so that they could process the NSH and forward 1111 accordingly. 1113 [Editor's Note - more details to be added] 1115 3.10. Use Cases of PCECC for Native IP 1117 [RFC8735] describes the scenarios, and suggestions for the "Centrally 1118 Control Dynamic Routing (CCDR)" architecture, which integrates the 1119 merit of traditional distributed protocols (IGP/BGP), and the power 1120 of centrally control technologies (PCE/SDN) to provide one feasible 1121 traffic engineering solution in various complex scenarios for the 1122 service provider. [I-D.ietf-teas-pce-native-ip] defines the 1123 framework for CCDR traffic engineering within Native IP network, 1124 using Dual/Multi-BGP session strategy and CCDR architecture. PCEP 1125 protocol can be used to transfer the key parameters between PCE and 1126 the underlying network devices (PCC) using PCECC technique. The 1127 central control instructions from PCECC to identify which prefix 1128 should be advertised on which BGP session. 1130 3.11. Use Cases of PCECC for Local Protection (RSVP-TE) 1132 [I-D.cbrt-pce-stateful-local-protection] describes the need for the 1133 PCE to maintain and associate the local protection paths for the 1134 RSVP-TE LSP. Local protection requires the setup of a bypass at the 1135 PLR. This bypass can be PCC-initiated and delegated, or PCE- 1136 initiated. In either case, the PLR MUST maintain a PCEP session to 1137 the PCE. The Bypass LSPs need to mapped to the primary LSP. This 1138 could be done locally at the PLR based on a local policy but there is 1139 a need for a PCE to do the mapping as well to exert greater control. 1141 This mapping can be done via PCECC procedures where the PCE could 1142 instruct the PLR to the mapping and identify the primary LSP for 1143 which bypass should be used. 1145 3.12. Use Cases of PCECC for BIER 1147 Bit Index Explicit Replication (BIER) [RFC8279] defines an 1148 architecture where all intended multicast receivers are encoded as a 1149 bitmask in the multicast packet header within different 1150 encapsulations. A router that receives such a packet will forward 1151 the packet based on the bit position in the packet header towards the 1152 receiver(s) following a precomputed tree for each of the bits in the 1153 packet. Each receiver is represented by a unique bit in the bitmask. 1155 BIER-TE [I-D.ietf-bier-te-arch] shares architecture and packet 1156 formats with BIER. BIER-TE forwards and replicates packets based on 1157 a BitString in the packet header, but every BitPosition of the 1158 BitString of a BIER-TE packet indicates one or more adjacencies. 1159 BIER-TE Path can be derived from a PCE and used at the ingress as 1160 described in [I-D.chen-pce-bier]. 1162 Further, PCECC mechanims could be used for the allocation of bits for 1163 the BIER router for BIER as well as for the adjacencies for BIER-TE. 1164 PCECC based controller can use PCEP to instruct the BIER capable 1165 routers the meaning of the bits as well as other fields needed for 1166 BIER encapsulation. 1168 [Editor's Note - more details to be added] 1170 4. IANA Considerations 1172 This document does not require any action from IANA. 1174 5. Security Considerations 1176 TBD. 1178 6. Acknowledgments 1180 We would like to thank Adrain Farrel, Aijun Wang, Robert Tao, 1181 Changjiang Yan, Tieying Huang, Sergio Belotti, Dieter Beller, Andrey 1182 Elperin and Evgeniy Brodskiy for their useful comments and 1183 suggestions. 1185 7. References 1187 7.1. Normative References 1189 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1190 Requirement Levels", BCP 14, RFC 2119, 1191 DOI 10.17487/RFC2119, March 1997, 1192 . 1194 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1195 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1196 DOI 10.17487/RFC5440, March 2009, 1197 . 1199 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1200 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1201 May 2017, . 1203 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 1204 Architecture for Use of PCE and the PCE Communication 1205 Protocol (PCEP) in a Network with Central Control", 1206 RFC 8283, DOI 10.17487/RFC8283, December 2017, 1207 . 1209 7.2. Informative References 1211 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 1212 Edge-to-Edge (PWE3) Architecture", RFC 3985, 1213 DOI 10.17487/RFC3985, March 2005, 1214 . 1216 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 1217 Hierarchy with Generalized Multi-Protocol Label Switching 1218 (GMPLS) Traffic Engineering (TE)", RFC 4206, 1219 DOI 10.17487/RFC4206, October 2005, 1220 . 1222 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 1223 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 1224 2006, . 1226 [RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel, 1227 "Label Switched Path Stitching with Generalized 1228 Multiprotocol Label Switching Traffic Engineering (GMPLS 1229 TE)", RFC 5150, DOI 10.17487/RFC5150, February 2008, 1230 . 1232 [RFC5151] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur, "Inter- 1233 Domain MPLS and GMPLS Traffic Engineering -- Resource 1234 Reservation Protocol-Traffic Engineering (RSVP-TE) 1235 Extensions", RFC 5151, DOI 10.17487/RFC5151, February 1236 2008, . 1238 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 1239 Objective Functions in the Path Computation Element 1240 Communication Protocol (PCEP)", RFC 5541, 1241 DOI 10.17487/RFC5541, June 2009, 1242 . 1244 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 1245 Requirements for the Path Computation Element 1246 Communication Protocol (PCECP)", RFC 5376, 1247 DOI 10.17487/RFC5376, November 2008, 1248 . 1250 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 1251 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 1252 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 1253 2015, . 1255 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 1256 Chaining (SFC) Architecture", RFC 7665, 1257 DOI 10.17487/RFC7665, October 2015, 1258 . 1260 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 1261 Computation Element Communication Protocol (PCEP) 1262 Extensions for Stateful PCE", RFC 8231, 1263 DOI 10.17487/RFC8231, September 2017, 1264 . 1266 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 1267 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 1268 Explicit Replication (BIER)", RFC 8279, 1269 DOI 10.17487/RFC8279, November 2017, 1270 . 1272 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 1273 Computation Element Communication Protocol (PCEP) 1274 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 1275 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 1276 . 1278 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1279 Shakir, "Resiliency Use Cases in Source Packet Routing in 1280 Networking (SPRING) Networks", RFC 8355, 1281 DOI 10.17487/RFC8355, March 2018, 1282 . 1284 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1285 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1286 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1287 July 2018, . 1289 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 1290 and J. Hardwick, "Path Computation Element Communication 1291 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 1292 DOI 10.17487/RFC8664, December 2019, 1293 . 1295 [I-D.ietf-pce-stateful-hpce] 1296 Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., and D. King, 1297 "Hierarchical Stateful Path Computation Element (PCE)", 1298 draft-ietf-pce-stateful-hpce-15 (work in progress), 1299 October 2019. 1301 [I-D.ietf-pce-pcep-flowspec] 1302 Dhody, D., Farrel, A., and Z. Li, "PCEP Extension for Flow 1303 Specification", draft-ietf-pce-pcep-flowspec-08 (work in 1304 progress), March 2020. 1306 [I-D.ietf-pce-pcep-extension-for-pce-controller] 1307 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 1308 and Protocol Extensions for Using PCE as a Central 1309 Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 1310 extension-for-pce-controller-03 (work in progress), 1311 November 2019. 1313 [I-D.zhao-pce-pcep-extension-pce-controller-sr] 1314 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 1315 and Protocol Extensions for Using PCE as a Central 1316 Controller (PCECC) of SR-LSPs", draft-zhao-pce-pcep- 1317 extension-pce-controller-sr-05 (work in progress), July 1318 2019. 1320 [I-D.li-pce-controlled-id-space] 1321 Li, C., Chen, M., Dong, J., Li, Z., Wang, A., Cheng, W., 1322 and C. Zhou, "PCE Controlled ID Space", draft-li-pce- 1323 controlled-id-space-04 (work in progress), January 2020. 1325 [I-D.dugeon-pce-stateful-interdomain] 1326 Dugeon, O., Meuric, J., Lee, Y., and D. Ceccarelli, "PCEP 1327 Extension for Stateful Inter-Domain Tunnels", draft- 1328 dugeon-pce-stateful-interdomain-03 (work in progress), 1329 November 2019. 1331 [I-D.cbrt-pce-stateful-local-protection] 1332 Barth, C. and R. Torvi, "PCEP Extensions for RSVP-TE 1333 Local-Protection with PCE-Stateful", draft-cbrt-pce- 1334 stateful-local-protection-01 (work in progress), June 1335 2018. 1337 [I-D.filsfils-spring-srv6-network-programming] 1338 Filsfils, C., Camarillo, P., Leddy, J., 1339 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 1340 Network Programming", draft-filsfils-spring-srv6-network- 1341 programming-07 (work in progress), February 2019. 1343 [I-D.ietf-pce-segment-routing-ipv6] 1344 Negi, M., Li, C., Sivabalan, S., Kaladharan, P., and Y. 1345 Zhu, "PCEP Extensions for Segment Routing leveraging the 1346 IPv6 data plane", draft-ietf-pce-segment-routing-ipv6-03 1347 (work in progress), October 2019. 1349 [I-D.ietf-6man-segment-routing-header] 1350 Filsfils, C., Dukes, D., Previdi, S., Leddy, J., 1351 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1352 (SRH)", draft-ietf-6man-segment-routing-header-26 (work in 1353 progress), October 2019. 1355 [I-D.ietf-teas-pce-native-ip] 1356 Wang, A., Zhao, Q., Khasanov, B., and H. Chen, "PCE in 1357 Native IP Network", draft-ietf-teas-pce-native-ip-05 (work 1358 in progress), January 2020. 1360 [RFC8735] Wang, A., Huang, X., Kou, C., Li, Z., and P. Mi, 1361 "Scenarios and Simulation Results of PCE in a Native IP 1362 Network", RFC 8735, DOI 10.17487/RFC8735, February 2020, 1363 . 1365 [I-D.ietf-bier-te-arch] 1366 Eckert, T., Cauchie, G., and M. Menth, "Path Engineering 1367 for Bit Index Explicit Replication (BIER-TE)", draft-ietf- 1368 bier-te-arch-06 (work in progress), February 2020. 1370 [I-D.chen-pce-bier] 1371 Chen, R., Zhang, Z., Dhanaraj, S., and F. Qin, "PCEP 1372 Extensions for BIER-TE", draft-chen-pce-bier-06 (work in 1373 progress), November 2019. 1375 [MAP-REDUCE] 1376 Lee, K., Choi, T., Ganguly, A., Wolinsky, D., Boykin, P., 1377 and R. Figueiredo, "Parallel Processing Framework on a P2P 1378 System Using Map and Reduce Primitives", , may 2011, 1379 . 1381 [MPLS-DC] Afanasiev, D. and D. Ginsburg, "MPLS in DC and inter-DC 1382 networks: the unified forwarding mechanism for network 1383 programmability at scale", , march 2014, 1384 . 1387 7.3. URIs 1389 [1] https://hadoop.apache.org/ 1391 Appendix A. Using reliable P2MP TE based multicast delivery for 1392 distributed computations (MapReduce-Hadoop) 1394 MapReduce model of distributed computations in computing clusters is 1395 widely deployed. In Hadoop [1] 1.0 architecture MapReduce operations 1396 on big data performs by means of Master-Slave architecture in the 1397 Hadoop Distributed File System (HDFS), where NameNode has the 1398 knowledge about resources of the cluster and where actual data 1399 (chunks) for particular task are located (which DataNode). Each 1400 chunk of data (64MB or more) should have 3 saved copies in different 1401 DataNodes based on their proximity. 1403 Proximity level currently has semi-manual allocation and based on 1404 Rack IDs (Assumption is that closer data are better because of access 1405 speed/smaller latency). 1407 JobTracker node is responsible for computation tasks, scheduling 1408 across DataNodes and also have Rack-awareness. Currently transport 1409 protocols between NameNode/JobTracker and DataNodes are based on IP 1410 unicast. It has simplicity as pros but has numerous drawbacks 1411 related with its flat approach. 1413 It is clear that we should go beyond of one DC for Hadoop cluster 1414 creation and move towards distributed clusters. In that case we need 1415 to handle performance and latency issues. Latency depends on speed 1416 of light in fiber links and also latency introduced by intermediate 1417 devices in between. The last one is closely correlated with network 1418 device architecture and performance. Current performance of NPU 1419 based routers should be enough for creating distribute Hadoop 1420 clusters with predicted latency. Performance of SW based routers 1421 (mainly as VNF) together with additional HW features such as DPDK are 1422 promising but require additional research and testing. 1424 Main question is how can we create simple but effective architecture 1425 for distributed Hadoop cluster? 1427 There is research [MAP-REDUCE] which show how usage of multicast tree 1428 could improve speed of resource or cluster members discovery inside 1429 the cluster as well as increase redundancy in communications between 1430 cluster nodes. 1432 Is traditional IP based multicast enough for that? We doubt it 1433 because it requires additional control plane (IGMP, PIM) and a lot of 1434 signaling, that is not suitable for high performance computations, 1435 that are very sensitive to latency. 1437 P2MP TE tunnels looks much more suitable as potential solution for 1438 creation of multicast based communications between Master and Slave 1439 nodes inside cluster. Obviously these P2MP tunnels should be 1440 dynamically created and turned down (no manual intervention). Here, 1441 the PCECC comes to play with main objective to create optimal 1442 topology of each particular request for MapReduce computation and 1443 also create P2MP tunnels with needed parameters such as bandwidth and 1444 delay. 1446 This solution would require to use MPLS label based forwarding inside 1447 the cluster. Usage of label based forwarding inside DC was proposed 1448 by Yandex [MPLS-DC]. Technically it is already possible because MPLS 1449 on switches is already supported by some vendors, MPLS also exists on 1450 Linux and OVS. 1452 The following framework can make this task: 1454 +--------+ 1455 | APP | 1456 +--------+ 1457 | NBI (REST API,...) 1458 | 1459 PCEP +----------+ REST API 1460 +---------+ +---| PCECC |----------+ 1461 | Client |---|---| | | 1462 +---------+ | +----------+ | 1463 | | | | | | 1464 +-----|---+ |PCEP| | 1465 +--------+ | | | | | 1466 | | | | | | 1467 | REST API | | | | | 1468 | | | | | | 1469 +-------------+ | | | | +----------+ 1470 | Job Tracker | | | | | | NameNode | 1471 | | | | | | | | 1472 +-------------+ | | | | +----------+ 1473 +------------------+ | +-----------+ 1474 | | | | 1475 |---+-----P2MP TE--+-----|-----------| | 1476 +----------+ +----------+ +----------+ 1477 | DataNode1| | DataNode2| | DataNodeN| 1478 |TaskTraker| |TaskTraker| .... |TaskTraker| 1479 +----------+ +----------+ +----------+ 1481 Communication between Master nodes (JobTracker and NameNode) and 1482 PCECC via REST API MAY be either done directly or via cluster manager 1483 such as Mesos. 1485 Phase 1: Distributed cluster resources discovery During this phase 1486 Master Nodes SHOULD identify and find available Slave nodes according 1487 to computing request from application (APP). NameNode SHOULD query 1488 PCECC about available DataNodes, NameNode MAY provide additional 1489 constrains to PCECC such as topological proximity, redundancy level. 1491 PCECC SHOULD analyze the topology of distributed cluster and perform 1492 constrain based path calculation from client towards most suitable 1493 NameNodes. PCECC SHOULD reply to NameNode the list of most suitable 1494 DataNodes and their resource capabilities. Topology discovery 1495 mechanism for PCECC will be added later to that framework. 1497 Phase 2: PCECC SHOULD create P2MP LSP from client towards those 1498 DataNodes by means of PCEP messages following previously calculated 1499 path. 1501 Phase 3. NameNode SHOULD send this information to client, PCECC 1502 informs client about optimal P2MP path towards DataNodes via PCEP 1503 message. 1505 Phase 4. Client sends data blocks to those DataNodes for writing via 1506 created P2MP tunnel. 1508 When this task will be finished, P2MP tunnel could be turned down. 1510 Authors' Addresses 1512 Quintin Zhao 1513 Huawei Technologies 1514 125 Nagog Technology Park 1515 Acton, MA 01719 1516 US 1518 Email: quintinzhao@gmail.com 1520 Zhenbin (Robin) Li 1521 Huawei Technologies 1522 Huawei Bld., No.156 Beiqing Rd. 1523 Beijing 100095 1524 China 1526 Email: lizhenbin@huawei.com 1528 Boris Khasanov 1529 Huawei Technologies 1530 Moskovskiy Prospekt 97A 1531 St.Petersburg 196084 1532 Russia 1534 Email: khasanov.boris@huawei.com 1536 Dhruv Dhody 1537 Huawei Technologies 1538 Divyashree Techno Park, Whitefield 1539 Bangalore, Karnataka 560066 1540 India 1542 Email: dhruv.ietf@gmail.com 1543 King Ke 1544 Tencent Holdings Ltd. 1545 Shenzhen 1546 China 1548 Email: kinghe@tencent.com 1550 Luyuan Fang 1551 Expedia, Inc. 1552 USA 1554 Email: luyuanf@gmail.com 1556 Chao Zhou 1557 Cisco Systems 1559 Email: chao.zhou@cisco.com 1561 Boris Zhang 1562 Telus Communications 1564 Email: Boris.zhang@telus.com 1566 Artem Rachitskiy 1567 Mobile TeleSystems JLLC 1568 Nezavisimosti ave., 95 1569 Minsk 220043 1570 Belarus 1572 Email: arachitskiy@mts.by 1574 Anton Gulida 1575 LLC "Lifetech" 1576 Krasnoarmeyskaya str., 24 1577 Minsk 220030 1578 Belarus 1580 Email: anton.gulida@life.com.by