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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 12, 2019 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 11, 2019 21 The Use Cases for Path Computation Element (PCE) as a Central Controller 22 (PCECC). 23 draft-ietf-teas-pcecc-use-cases-03 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 Requirements Language 51 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 52 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 53 "OPTIONAL" in this document are to be interpreted as described in BCP 54 14 [RFC2119] [RFC8174] when, and only when, they appear in all 55 capitals, as shown here. 57 Status of This Memo 59 This Internet-Draft is submitted in full conformance with the 60 provisions of BCP 78 and BCP 79. 62 Internet-Drafts are working documents of the Internet Engineering 63 Task Force (IETF). Note that other groups may also distribute 64 working documents as Internet-Drafts. The list of current Internet- 65 Drafts is at https://datatracker.ietf.org/drafts/current/. 67 Internet-Drafts are draft documents valid for a maximum of six months 68 and may be updated, replaced, or obsoleted by other documents at any 69 time. It is inappropriate to use Internet-Drafts as reference 70 material or to cite them other than as "work in progress." 72 This Internet-Draft will expire on September 12, 2019. 74 Copyright Notice 76 Copyright (c) 2019 IETF Trust and the persons identified as the 77 document authors. All rights reserved. 79 This document is subject to BCP 78 and the IETF Trust's Legal 80 Provisions Relating to IETF Documents 81 (https://trustee.ietf.org/license-info) in effect on the date of 82 publication of this document. Please review these documents 83 carefully, as they describe your rights and restrictions with respect 84 to this document. Code Components extracted from this document must 85 include Simplified BSD License text as described in Section 4.e of 86 the Trust Legal Provisions and are provided without warranty as 87 described in the Simplified BSD License. 89 Table of Contents 91 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 92 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 93 3. Application Scenarios . . . . . . . . . . . . . . . . . . . . 4 94 3.1. Use Cases of PCECC for Label Management . . . . . . . . . 4 95 3.2. Using PCECC for SR . . . . . . . . . . . . . . . . . . . 6 96 3.2.1. PCECC SID Allocation . . . . . . . . . . . . . . . . 7 97 3.2.2. Use Cases of PCECC for SR Best Effort (BE) Path . . . 8 98 3.2.3. Use Cases of PCECC for SR Traffic Engineering (TE) 99 Path . . . . . . . . . . . . . . . . . . . . . . . . 8 100 3.3. Use Cases of PCECC for TE LSP . . . . . . . . . . . . . . 9 101 3.3.1. PCECC Load Balancing (LB) Use Case . . . . . . . . . 11 102 3.3.2. PCECC and Inter-AS TE . . . . . . . . . . . . . . . . 13 103 3.4. Use Cases of PCECC for Multicast LSPs . . . . . . . . . . 16 104 3.4.1. Using PCECC for P2MP/MP2MP LSPs' Setup . . . . . . . 16 105 3.4.2. Use Cases of PCECC for the Resiliency of P2MP/MP2MP 106 LSPs . . . . . . . . . . . . . . . . . . . . . . . . 17 107 3.5. Use Cases of PCECC for LSP in the Network Migration . . . 19 108 3.6. Use Cases of PCECC for L3VPN and PWE3 . . . . . . . . . . 21 109 3.7. Using PCECC for Traffic Classification Information . . . 22 110 3.8. Use Cases of PCECC for SRv6 . . . . . . . . . . . . . . . 22 111 3.9. Use Cases of PCECC for SFC . . . . . . . . . . . . . . . 24 112 3.10. Use Cases of PCECC for Native IP . . . . . . . . . . . . 24 113 3.11. Use Cases of PCECC for Local Protection (RSVP-TE) . . . . 25 114 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 115 5. Security Considerations . . . . . . . . . . . . . . . . . . . 25 116 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 117 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 118 7.1. Normative References . . . . . . . . . . . . . . . . . . 25 119 7.2. Informative References . . . . . . . . . . . . . . . . . 26 120 Appendix A. Using reliable P2MP TE based multicast delivery for 121 distributed computations (MapReduce-Hadoop) . . . . 29 122 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 124 1. Introduction 126 An Architecture for Use of PCE and PCEP [RFC5440] in a Network with 127 Central Control [RFC8283] describes SDN architecture where the Path 128 Computation Element (PCE) determines paths for variety of different 129 usecases, with PCEP as a general southbound communication protocol 130 with all the nodes along the path.. 132 [I-D.ietf-pce-pcep-extension-for-pce-controller] introduces the 133 procedures and extensions for PCEP to support the PCECC architecture 134 [RFC8283]. 136 This draft describes the various usecases for the PCECC architecture. 138 2. Terminology 140 The following terminology is used in this document. 142 IGP: Interior Gateway Protocol. Either of the two routing 143 protocols, Open Shortest Path First (OSPF) or Intermediate System 144 to Intermediate System (IS-IS). 146 PCC: Path Computation Client: any client application requesting a 147 path computation to be performed by a Path Computation Element. 149 PCE: Path Computation Element. An entity (component, application, 150 or network node) that is capable of computing a network path or 151 route based on a network graph and applying computational 152 constraints. 154 PCECC: PCE as a central controller. Extension of PCE to support SDN 155 functions as per [RFC8283]. 157 TE: Traffic Engineering. 159 3. Application Scenarios 161 In the following sections, several use cases are described, 162 showcasing scenarios that benefit from the deployment of PCECC. 164 3.1. Use Cases of PCECC for Label Management 166 As per [RFC8283], in some cases, the PCE-based controller can take 167 responsibility for managing some part of the MPLS label space for 168 each of the routers that it controls, and it may taker wider 169 responsibility for partitioning the label space for each router and 170 allocating different parts for different uses, communicating the 171 ranges to the router using PCEP. 173 [I-D.ietf-pce-pcep-extension-for-pce-controller] describe a mode 174 where LSPs are provisioned as explicit label instructions at each hop 175 on the end-to-end path. Each router along the path must be told what 176 label forwarding instructions to program and what resources to 177 reserve. The controller uses PCEP to communicate with each router 178 along the path of the end-to-end LSP. For this to work, the PCE- 179 based controller will take responsibility for managing some part of 180 the MPLS label space for each of the routers that it controls. An 181 extension to PCEP could be done to allow a PCC to inform the PCE of 182 such a label space to control. 184 [I-D.ietf-pce-segment-routing] specifies extensions to PCEP that 185 allow a stateful PCE to compute, update or initiate SR-TE paths. 186 [I-D.zhao-pce-pcep-extension-pce-controller-sr] describes the 187 mechanism for PCECC to allocate and provision the node/prefix/ 188 adjacency label (SID) via PCEP. To make such allocation PCE needs to 189 be aware of the label space from Segment Routing Global Block (SRGB) 190 or Segment Routing Local Block (SRLB) [RFC8402] of the node that it 191 controls. A mechanism for a PCC to inform the PCE of such a label 192 space to control is needed within PCEP. The full SRGB/SRLB of a node 193 could be learned via existing IGP or BGP-LS mechanism too. 195 [I-D.li-pce-controlled-id-space] defines a PCEP extension to support 196 advertisement of the MPLS label space to the PCE to control. 198 There have been various proposals for Global Labels, the PCECC 199 architecture could be used as means to learn the label space of 200 nodes, and could also be used to determine and provision the global 201 label range. 203 +------------------------------+ +------------------------------+ 204 | PCE DOMAIN 1 | | PCE DOMAIN 2 | 205 | +--------+ | | +--------+ | 206 | | | | | | | | 207 | | PCECC1 | ---------PCEP---------- | PCECC2 | | 208 | | | | | | | | 209 | | | | | | | | 210 | +--------+ | | +--------+ | 211 | ^ ^ | | ^ ^ | 212 | / \ PCEP | | PCEP / \ | 213 | V V | | V V | 214 | +--------+ +--------+ | | +--------+ +--------+ | 215 | |NODE 11 | | NODE 1n| | | |NODE 21 | | NODE 2n| | 216 | | | ...... | | | | | | ...... | | | 217 | | PCECC | | PCECC | | | | PCECC | |PCECC | | 218 | |Enabled | | Enabled| | |Enabled | |Enabled | | 219 | +--------+ +--------+ | | +--------+ +--------+ | 220 | | | | 221 +------------------------------+ +------------------------------+ 223 Figure 1: PCECC for Label Management 225 o PCC would advertise the PCECC capability to the PCE (central 226 controller-PCECC) 227 [I-D.ietf-pce-pcep-extension-for-pce-controller]. 229 o The PCECC could also learn the label range set aside by the PCC 230 ([I-D.li-pce-controlled-id-space]). 232 o Optionally, the PCECC could determine the shared MPLS global label 233 range for the network. 235 o In the case that the shared global label range need to be 236 negotiated across multiple domains, the central controllers of 237 these domains would also need to negotiate a common global 238 label range across domains. 240 o The PCECC would need to set the shared global label range to 241 all PCC nodes in the network. 243 3.2. Using PCECC for SR 245 Segment Routing (SR) leverages the source routing paradigm. Using 246 SR, a source node steers a packet through a path without relying on 247 hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is 248 specified as an ordered list of instructions called "segments". Each 249 segment is an instruction to route the packet to a specific place in 250 the network, or to perform a specific service on the packet. A 251 database of segments can be distributed through the network using a 252 routing protocol (such as IS-IS or OSPF) or by any other means. PCEP 253 (and PCECC) could be one such means. 255 [I-D.ietf-pce-segment-routing] specify the SR specific PCEP 256 extensions. PCECC may further use PCEP protocol for SR SID (Segment 257 Identifier) distribution to the SR nodes (PCC) with some benefits. 258 If the PCECC allocates and maintains the SID in the network for the 259 nodes and adjacencies; and further distributes them to the SR nodes 260 directly via the PCEP session has some advantage over the 261 configurations on each SR node and flooding via IGP, especially in a 262 SDN environment. 264 When the PCECC is used for the distribution of the node segment ID 265 and adjacency segment ID, the node segment ID is allocated from the 266 SRGB of the node. For the allocation of adjacency segment ID, the 267 allocation is from the SRLB of the node as described in 268 [I-D.zhao-pce-pcep-extension-pce-controller-sr]. 270 [RFC8355] identifies various protection and resiliency usecases for 271 SR. Path protection lets the ingress node be in charge of the 272 failure recovery (used for SR-TE). Also protection can be performed 273 by the node adjacent to the failed component, commonly referred to as 274 local protection techniques or fast-reroute (FRR) techniques. In 275 case of PCECC, the protection paths can be pre-computed and setup by 276 the PCE. 278 The following example illustrate the use case where the node SID and 279 adjacency SID are allocated by the PCECC. 281 192.0.2.1/32 282 +----------+ 283 | R1(1001) | 284 +----------+ 285 | 286 +----------+ 287 | R2(1002) | 192.0.2.2/32 288 +----------+ 289 * | * * 290 * | * * 291 *link1| * * 292 192.0.2.4/32 * | *link2 * 192.0.2.5/32 293 +-----------+ 9001| * +-----------+ 294 | R4(1004) | | * | R5(1005) | 295 +-----------+ | * +-----------+ 296 * | *9003 * + 297 * | * * + 298 * | * * + 299 +-----------+ +-----------+ 300 192.0.2.3/32 | R3(1003) | |R6(1006) |192.0.2.6/32 301 +-----------+ +-----------+ 302 | 303 +-----------+ 304 | R8(1008) | 192.0.2.8/32 305 +-----------+ 307 3.2.1. PCECC SID Allocation 309 Each node (PCC) is allocated a node-SID by the PCECC. The PCECC 310 needs to update the label map of each node to all the nodes in the 311 domain. On receiving the label map, each node (PCC) uses the local 312 routing information to determine the next-hop and download the label 313 forwarding instructions accordingly. The forwarding behavior and the 314 end result is same as IGP based Node-SID in SR. Thus, from anywhere 315 in the domain, it enforces the ECMP-aware shortest-path forwarding of 316 the packet towards the related node. 318 For each adjacency in the network, PCECC can allocate an Adj-SID. 319 The PCECC sends PCInitiate message to update the label map of each 320 Adj to the corresponding nodes in the domain. Each node (PCC) 321 download the label forwarding instructions accordingly. The 322 forwarding behavior and the end result is similar to IGP based "Adj- 323 SID" in SR. 325 The various mechanism are described in 326 [I-D.zhao-pce-pcep-extension-pce-controller-sr]. 328 3.2.2. Use Cases of PCECC for SR Best Effort (BE) Path 330 In this mode of the solution, the PCECC just need to allocate the 331 node segment ID and adjacency ID (without calculating the explicit 332 path for the SR path). The ingress of the forwarding path just need 333 to encapsulate the destination node segment ID on top of the packet. 334 All the intermediate nodes will forward the packet based on the 335 destination node SID. It is similar to the LDP LSP. 337 R1 may send a packet to R8 simply by pushing an SR header with 338 segment list {1008} (Node SID for R8). The path would be the based 339 on the routing/nexthop calculation on the routers. 341 3.2.3. Use Cases of PCECC for SR Traffic Engineering (TE) Path 343 SR-TE paths may not follow an IGP SPT. Such paths may be chosen by a 344 PCECC and provisioned on the ingress node of the SR-TE path. The SR 345 header consists of a list of SIDs (or MPLS labels). The header has 346 all necessary information so that, the packets can be guided from the 347 ingress node to the egress node of the path; hence, there is no need 348 for any signaling protocol. For the case where strict traffic 349 engineering path is needed, all the adjacency SID are stacked, 350 otherwise a combination of node-SID or adj-SID can be used for the 351 SR-TE paths. 353 Note that the bandwidth reservations is only guaranteed at controller 354 and through the enforce of the bandwidth admission control. As for 355 the RSVP-TE LSP case, the control plane signaling also does the link 356 bandwidth reservation in each hop of the path. 358 The SR traffic engineering path examples are explained as bellow: 360 Note that the node SID for each node is allocated from the SRGB and 361 adjacency SID for each link are allocated from the SRLB for each 362 node. 364 Example 1: 366 R1 may send a packet P1 to R8 simply by pushing an SR header with 367 segment list {1008}. Based on the best path, it could be: 368 R1-R2-R3-R8. 370 Example 2: 372 R1 may send a packet P2 to R8 by pushing an SR header with segment 373 list {1002, 9001, 1008}. The path should be: R1-R2-link1-R3-R8. 375 Example 3: 377 R1 may send a packet P3 to R8 via R4 by pushing an SR header with 378 segment list {1004, 1008}. The path could be : R1-R2-R4-R3-R8 380 The local protection examples for SR TE path are explained below: 382 Example 4: local link protection: 384 o R1 may send a packet P4 to R8 by pushing an SR header with segment 385 list {1002, 9001, 1008}. The path should be: R1-R2-link1-R3-R8. 387 o When node R2 receives the packet from R1 which has the header of 388 link1-R3-R8, and also find out there is a link failure of link1, 389 then the R2 can enforce the traffic over the bypass to send out 390 the packet with header of R3-R8 through link2. 392 Example 5: local node protection: 394 o R1 may send a packet P5 to R8 by pushing an SR header with segment 395 list {1004, 1008}. The path could be : R1-R2-R4-R3-R8. 397 o When node R2 receives the packet from R1 which has the header of 398 {1004, 1008}, and also finds out there is a node failure for 399 node4, then it can enforce the traffic over the bypass and send 400 out the packet with header of {1005, 1008} to node5 instead of 401 node4. 403 3.3. Use Cases of PCECC for TE LSP 405 In the Section 3.2 the case of SR path via PCECC is discussed. 406 Although those cases give the simplicity and scalability, but there 407 are existing functionalities for the traffic engineering path such as 408 the bandwidth guarantee, monitoring where SR based solution are 409 complex. Also there are cases where the depth of the label stack is 410 an issue for existing deployment and certain vendors. 412 So to address these issues, PCECC architecture also support the TE 413 LSP functionalities. To achieve this, the existing PCEP can be used 414 to communicate between the PCECC and nodes along the path. This is 415 similar to static LSPs, where LSPs can be provisioned as explicit 416 label instructions at each hop on the end-to-end path. Each router 417 along the path must be told what label- forwarding instructions to 418 program and what resources to reserve. The PCE-based controller 419 keeps a view of the network and determines the paths of the end-to- 420 end LSPs, and the controller uses PCEP to communicate with each 421 router along the path of the end-to-end LSP. 423 192.0.2.1/32 424 +----------+ 425 | R1 | 426 +----------+ 427 | | 428 |link1 | 429 | |link2 430 +----------+ 431 | R2 | 192.0.2.2/32 432 +----------+ 433 link3 * | * * link4 434 * | * * 435 *link5| * * 436 192.0.2.4/32 * | *link6 * 192.0.2.5/32 437 +-----------+ | * +-----------+ 438 | R4 | | * | R5 | 439 +-----------+ | * +-----------+ 440 * | * * + 441 link10 * | * *link7 + 442 * | * * + 443 +-----------+ +-----------+ 444 192.0.2.3/32 | R3 | |R6 |192.0.2.6/32 445 +-----------+ +-----------+ 446 | | 447 |link8 | 448 | |link9 449 +-----------+ 450 | R8 | 192.0.2.8/32 451 +-----------+ 453 Figure 2: PCECC TE LSP Setup Example 455 o Based on path computation request / delegation or PCE initiation, 456 the PCECC receives the PCECC request with constraints and 457 optimization criteria. 459 o PCECC would calculate the optimal path according to given 460 constrains (e.g. bandwidth). 462 o PCECC would provision each node along the path and assign incoming 463 and outgoing labels from R1 to R8 with the path: {R1, link1, 464 1001}, {1001, R2, link3, 2003], {2003, R4, link10, 4010}, {4010, 465 R3, link8, 3008}, {3008, R8}. 467 o For the end to end protection, PCECC program each node along the 468 path from R1 to R8 with the secondary path: {R1, link2, 1002}, 469 {1002, R2, link4, 2004], {2004, R5, link7, 5007}, {5007, R3, 470 link9, 3009}, {3009, R8}. 472 o It is also possible to have a bypass path for the local protection 473 setup by the PCECC. For example, the primary path as above, then 474 to protect the node R4 locally, PCECC can program the bypass path 475 like this: {R2, link5, 2005}, {2005, R3}. By doing this, the node 476 R4 is locally protected at R2. 478 3.3.1. PCECC Load Balancing (LB) Use Case 480 Very often many service providers use TE tunnels for solving issues 481 with non-deterministic paths in their networks. One example of such 482 applications is usage of TEs in the mobile backhaul (MBH). Consider 483 the following topology - 485 TE1 --------------> 486 +---------+ +--------+ +--------+ +--------+ +------+ +---+ 487 | Access |----| Access |----| AGG 1 |----| AGG N-1|----|Core 1|--|SR1| 488 | SubNode1| | Node 1 | +--------+ +--------+ +------+ +---+ 489 +---------+ +--------+ | | | ^ | 490 | Access | Access | AGG Ring 1 | | | 491 | SubRing 1 | Ring 1 | | | | | 492 +---------+ +--------+ +--------+ | | | 493 | Access | | Access | | AGG 2 | | | | 494 | SubNode2| | Node 2 | +--------+ | | | 495 +---------+ +--------+ | | | | | 496 | | | | | | | 497 | | | +----TE2----|-+ | 498 +---------+ +--------+ +--------+ +--------+ +------+ +---+ 499 | Access | | Access |----| AGG 3 |----| AGG N |----|Core N|--|SRn| 500 | SubNodeN|----| Node N | +--------+ +--------+ +------+ +---+ 501 +---------+ +--------+ 503 This MBH architecture uses L2 access rings and sub-rings. L3 starts 504 at the aggregation layer. For the sake of simplicity, the figure 505 shows only one access sub-ring, access ring and aggregation ring 506 (AGG1...AGGN), connected by Nx10GE interfaces. Aggregation domain 507 runs its own IGP. There are two Egress routers (AGG N-1,AGG N) that 508 are connected to the Core domain via L2 interfaces. Core also have 509 connections to service routers, RSVP-TEs are used for MPLS transport 510 inside the ring. There could be at least 2 tunnels (one way) from 511 each AGG router to egress AGG routers. There are also many L2 access 512 rings connected to AGG routers. 514 Service deployment made by means of either L2VPNs (VPLS) or L3VPNs. 515 Those services use MPLS TE as transport towards egress AGG routers. 517 TE tunnels could be also used as transport towards service routers in 518 case of seamless MPLS based architecture in the future. 520 There is a need to solve the following tasks: 522 o Perform automatic load-balance amongst TE tunnels according to 523 current traffic load. 525 o TE bandwidth (BW) management: Provide guaranteed BW for specific 526 service: HSI, IPTV, etc., provide time-based BW reservation (BoD) 527 for other services. 529 o Simplify development of TE tunnels by automation without any 530 manual intervention. 532 o Provide flexibility for Service Router placement (anywhere in the 533 network by creation of transport LSPs to them). 535 Since other tasks are already considered by other PCECC use cases, in 536 this section, the focus is on load balancing (LB) task. LB task 537 could be solved by means of PCECC in the following way: 539 o After application or network service or operator can ask SDN 540 controller (PCECC) for LSP based LB between AGG X and AGG N/AGG 541 N-1 (egress AGG routers which have connections to core) via North 542 Bound Interface (NBI). Each of these would have associated 543 constrains (i.e. Path Setup Type (PST), bandwidth, inclusion or 544 exclusion specific links or nodes, number of paths, objective 545 function (OF), need for disjoint LSP paths etc.). 547 o PCECC could calculate multiple (Say N) LSPs according to given 548 constrains, calculation is based on results of Objective Function 549 (OF) [RFC5541], constraints, endpoints, same or different 550 bandwidth (BW) , different links (in case of disjoint paths) and 551 other constrains. 553 o Depending on given LSP Path setup type (PST), PCECC would use 554 download instructions to the PCC. At this stage it is assumed the 555 PCECC is aware of the label space it controls and in case of SR 556 the SID allocation and distribution is already done. 558 o PCECC would send PCInitiate PCEP message [RFC8281] towards ingress 559 AGG X router(PCC) for each of N LSPs and receives PCRpt PCEP 560 message [RFC8231] back from PCCs. If the PST is PCECC-SR, the 561 PCECC would include the SID stack as per 562 [I-D.ietf-pce-segment-routing]. If the PST is PCECC (basic), then 563 the PCECC would assigns labels along the calculated path; and set 564 up the path by sending central controller instructions in PCEP 565 message to each node along the path of the LSP as per 566 [I-D.ietf-pce-pcep-extension-for-pce-controller] and then send 567 PCUpd message to the ingress AGG X router with information about 568 new LSP and AGG X(PCC) would respond with PCRpt with LSP status. 570 o AGG X as ingress router now have N LSPs towards AGG N and AGG N-1 571 which are available for installing to router's forwarding and LB 572 of traffic between them. Traffic distribution between those LSPs 573 depends on particular realization of hash-function on that router. 575 o Since PCECC is aware of TEDB (TE state) and LSP-DB, it can manage 576 and prevent possible over-subscriptions and limit number of 577 available LB states. Via PCECC mechanism the control can take 578 quick actions into the network by directly provisioning the 579 central control instructions. 581 3.3.2. PCECC and Inter-AS TE 583 There are various signaling options for establishing Inter-AS TE LSP: 584 contiguous TE LSP [RFC5151], stitched TE LSP [RFC5150], nested TE LSP 585 [RFC4206]. 587 Requirements for PCE-based Inter-AS setup [RFC5376] describe the 588 approach and PCEP functionality that are needed for establishing 589 Inter-AS TE LSPs. 591 [RFC5376] also gives Inter- and Intra-AS PCE Reference Model that is 592 provided below in shorten form for the sake of simplicity. 594 Inter-AS Inter-AS 595 PCC <-->PCE1<--------->PCE2 596 :: :: :: 597 :: :: :: 598 R1----ASBR1====ASBR3---R3---ASBR5 599 | AS1 | | PCC | 600 | | | AS2 | 601 R2----ASBR2====ASBR4---R4---ASBR6 602 :: :: 603 :: :: 604 Intra-AS Intra-AS 605 PCE3 PCE4 607 Figure 3: Shorten form of Inter- and Intra-AS PCE Reference Model 608 [RFC5376] 610 The PCECC belonging to different domain can co-operate to setup 611 inter-AS TE LSP. The stateful H-PCE [I-D.ietf-pce-stateful-hpce] 612 mechanism could also be used to first establish a per-domain PCECC 613 LSP. These could be stitched together to form inter-AS TE LSP as 614 described in [I-D.dugeon-pce-stateful-interdomain]. 616 For the sake of simplicity, here after the focus is on a simplified 617 Inter-AS case when both AS1 and AS2 belong to the same service 618 provider administration. In that case Inter and Intra-AS PCEs could 619 be combined in one single PCE if such combined PCE performance is 620 enough for handling all path computation request and setup. There is 621 a potential to use a single PCE for both ASes if the scalability and 622 performance are enough. The PCE would require interfaces (PCEP and 623 BGP-LS) to both domains. PCECC redundancy mechanisms are described 624 in [RFC8283]. Thus routers in AS1 and AS2 (PCCs) can send PCEP 625 messages towards same PCECC. 627 +----BGP-LS------+ +------BGP-LS-----+ 628 | | | | 629 +-PCEP-|----++-+-------PCECC-----PCEP--++-+-|-------+ 630 +-:------|----::-:-+ +--::-:-|-------:---+ 631 | : | :: : | | :: : | : | 632 | : RR1 :: : | | :: : RR2 : | 633 | v v: : | LSP1 | :: v v | 634 | R1---------ASBR1=======================ASBR3--------R3 | 635 | | v : | | :v | | 636 | +----------ASBR2=======================ASBR4---------+ | 637 | | Region 1 : | | : Region 1 | | 638 |----------------:-| |--:-------------|--| 639 | | v | LSP2 | v | | 640 | +----------ASBR5=======================ASBR6---------+ | 641 | Region 2 | | Region 2 | 642 +------------------+ <--------------> +-------------------+ 643 MPLS Domain 1 Inter-AS MPLS Domain 2 644 <=======AS1=======> <========AS2=======> 646 Figure 4: Particular case of Inter-AS PCE 648 In a case of PCECC Inter-AS TE scenario where service provider 649 controls both domains (AS1 and AS2), each of them have own IGP and 650 MPLS transport. There is a need is to setup Inter-AS LSPs for 651 transporting different services on top of them (Voice, L3VPN etc.). 652 Inter-AS links with different capacity exist in several regions. The 653 task is not only to provision those Inter-AS LSPs with given 654 constrains but also calculate the path and pre-setup the backup 655 Inter-AS LSPs that will be used if primary LSP fails. 657 As per the Figure 4, LSP1 from R1 to R3 goes via ASBR1 and ASBR3, and 658 it is the primary Inter-AS LSP. R1-R3 LSP2 that go via ASBR5 and 659 ASBR6 is the backup one. In addition there could also be a bypass 660 LSP setup to protect against ASBR or inter-AS link failure. 662 After the addition of PCECC functionality to PCE (SDN controller), 663 PCECC based Inter-AS TE model SHOULD follow as PCECC usecase for TE 664 LSP as requirements of [RFC5376] with the following details: 666 o Since PCECC needs to know the topology of both domains AS1 and 667 AS2, PCECC could use BGP-LS peering with routers (or RRs) in both 668 domains. 670 o PCECC needs to PCEP connectivity towards all routers in both 671 domains (see also section 4 in [RFC5376]) in a similar manner as a 672 SDN controller. 674 o After operator's application or service orchestrator will create 675 request for tunnel creation of specific service, PCECC should 676 receive that request via NBI (NBI type is implementation 677 dependent, could be NETCONF/Yang, REST etc.). Then PCECC would 678 calculate the optimal path based on Objective Function (OF) and 679 given constraints (i.e. path setup type, bandwidth etc.), 680 including those from [RFC5376]: priority, AS sequence, preferred 681 ASBR, disjoint paths, protection. On this step we would have two 682 paths: R1-ASBR1-ASBR3-R3, R1-ASBR5-ASBR6-R3 684 o Depending on given LSP PST (PCECC or PCECC-SR), PCECC would use 685 central control download instructions to the PCC. At this stage 686 it is assumed the PCECC is aware of the label space it controls 687 and in case of SR the SID allocation and distribution is already 688 done. 690 o PCECC would send PCInitiate PCEP message [RFC8281] towards ingress 691 router R1 (PCC) in AS1 and receives PCRpt PCEP message [RFC8231] 692 back from PCC. If the PST is PCECC-SR, the PCECC would include 693 the SID stack as per [I-D.ietf-pce-segment-routing]. It may also 694 include binding SID based on AS boundary. The backup SID stack 695 could also be installed at ingress but more importantly each node 696 along the SR path could also do local protection just based on the 697 top segment. If the PST is PCECC (basic), then the PCECC would 698 assigns labels along the calculated paths (R1-ASBR1-ASBR3-R3, 699 R1-ASBR5-ASBR6-R3); and set up the path by sending central 700 controller instructions in PCEP message to each node along the 701 path of the LSPs as per 702 [I-D.ietf-pce-pcep-extension-for-pce-controller] and then send 703 PCUpd message to the ingress R1 router with information about new 704 LSPs and R1 would respond with PCRpt with LSP(s) status. 706 o After that step R1 now have primary and backup TEs (LSP1 and LSP2) 707 towards R3. It is up to router implementation how to make 708 switchover to backup LSP2 if LSP1 fails. 710 3.4. Use Cases of PCECC for Multicast LSPs 712 The current multicast LSPs are setup either using the RSVP-TE P2MP or 713 mLDP protocols. The setup of these LSPs may require manual 714 configurations and complex signaling when the protection is 715 considered. By using the PCECC solution, the multicast LSP can be 716 computed and setup through centralized controller which has the full 717 picture of the topology and bandwidth usage for each link. It not 718 only reduces the complex configurations comparing the distributed 719 RSVP-TE P2MP or mLDP signaling, but also it can compute the disjoint 720 primary path and secondary P2MP path efficiently. 722 3.4.1. Using PCECC for P2MP/MP2MP LSPs' Setup 724 It is assumed the PCECC is aware of the label space it controls for 725 all nodes and make allocations accordingly. 727 +----------+ 728 | R1 | Root node of the multicast LSP 729 +----------+ 730 |6000 731 +----------+ 732 Transit Node | R2 | 733 branch +----------+ 734 * | * * 735 9001* | * *9002 736 * | * * 737 +-----------+ | * +-----------+ 738 | R4 | | * | R5 | Transit Nodes 739 +-----------+ | * +-----------+ 740 * | * * + 741 9003* | * * +9004 742 * | * * + 743 +-----------+ +-----------+ 744 | R3 | | R6 | Leaf Node 745 +-----------+ +-----------+ 746 9005| 747 +-----------+ 748 | R8 | Leaf Node 749 +-----------+ 751 The P2MP examples are explained here, where R1 is root and R8 and R6 752 are the leaves. 754 o Based on the P2MP path computation request / delegation or PCE 755 initiation, the PCECC receives the PCECC request with constraints 756 and optimization criteria. 758 o PCECC would calculate the optimal P2MP path according to given 759 constrains (i.e.bandwidth). 761 o PCECC would provision each node along the path and assign incoming 762 and outgoing labels from R1 to {R6, R8} with the path: {R1, 6000}, 763 {6000, R2, {9001,9002}}, {9001, R4, 9003}, {9002, R5, 9004} {9003, 764 R3, 9005}, {9004, R6}, {9005, R8}. The main difference is in the 765 branch node instruction at R2 where two copies of packet are sent 766 towards R4 and R5 with 9001 and 9002 labels respectively. 768 The packet forwarding involves - 770 Step1: R1 may send a packet P1 to R2 simply by pushing an label of 771 6000 to the packet. 773 Step2: After R2 receives the packet with label 6000, it will 774 forwarding to R4 by swapping label to 9001 and by swapping label 775 of 9002 towards R5. 777 Step3: After R4 receives the packet with label 9001, it will 778 forwarding to R3 by swapping to 9003. After R5 receives the 779 packet with label 9002, it will forwarding to R6 by swapping to 780 9004. 782 Step4: After R3 receives the packet with label 9003, it will 783 forwarding to R8 by swapping to 9005 and when R5 receives the 784 packet with label 9004, it will swap to 9004 and send to R6. 786 Step5: Packet received at R8 and 9005 is popped; packet receives 787 at R6 and 9004 is popped. 789 3.4.2. Use Cases of PCECC for the Resiliency of P2MP/MP2MP LSPs 791 3.4.2.1. PCECC for the End-to-End Protection of the P2MP/MP2MP LSPs 793 In this section we describe the end-to-end managed path protection 794 service as well as the local protection with the operation management 795 in the PCECC network for the P2MP/MP2MP LSP. 797 An end-to-end protection principle can be applied for computing 798 backup P2MP or MP2MP LSPs. During computation of the primary 799 multicast trees, PCECC server may also take the computation of a 800 secondary tree into consideration. A PCE may compute the primary and 801 backup P2MP (or MP2MP) LSP together or sequentially. 803 +----+ +----+ 804 Root node of LSP | R1 |--| R11| 805 +----+ +----+ 806 / + 807 10/ +20 808 / + 809 +----------+ +-----------+ 810 Transit Node | R2 | | R3 | 811 +----------+ +-----------+ 812 | \ + + 813 | \ + + 814 10| 10\ +20 20+ 815 | \ + + 816 | \ + 817 | + \ + 818 +-----------+ +-----------+ Leaf Nodes 819 | R4 | | R5 | (Downstream LSR) 820 +-----------+ +-----------+ 822 In the example above, when the PCECC setup the primary multicast tree 823 from the root node R1 to the leaves, which is R1->R2->{R4, R5}, at 824 same time, it can setup the backup tree, which is R1->R11->R3->{R4, 825 R5}. Both the these two primary forwarding tree and secondary 826 forwarding tree will be downloaded to each routers along the primary 827 path and the secondary path. The traffic will be forwarded through 828 the R1->R2->{R4, R5} path normally, and when there is a node in the 829 primary tree fails (say R2), then the root node R1 will switch the 830 flow to the backup tree, which is R1->R11->R3->{R4, R5}. By using 831 the PCECC, the path computation and forwarding path downloading can 832 all be done without the complex signaling used in the P2MP RSVP-TE or 833 mLDP. 835 3.4.2.2. PCECC for the Local Protection of the P2MP/MP2MP LSPs 837 In this section we describe the local protection service in the PCECC 838 network for the P2MP/MP2MP LSP. 840 While the PCECC sets up the primary multicast tree, it can also build 841 the back LSP among PLR, the protected node, and MPs (the downstream 842 nodes of the protected node). In the cases where the amount of 843 downstream nodes are huge, this mechanism can avoid unnecessary 844 packet duplication on PLR and protect the network from traffic 845 congestion risk. 847 +------------+ 848 | R1 | Root Node 849 +------------+ 850 . 851 . 852 . 853 +------------+ Point of Local Repair/ 854 | R10 | Switchover Point 855 +------------+ (Upstream LSR) 856 / + 857 10/ +20 858 / + 859 +----------+ +-----------+ 860 Protected Node | R20 | | R30 | 861 +----------+ +-----------+ 862 | \ + + 863 | \ + + 864 10| 10\ +20 20+ 865 | \ + + 866 | \ + 867 | + \ + 868 +-----------+ +-----------+ Merge Point 869 | R40 | | R50 | (Downstream LSR) 870 +-----------+ +-----------+ 871 . . 872 . . 874 In the example above, when the PCECC setup the primary multicast path 875 around the PLR node R10 to protect node R20, which is R10->R20->{R40, 876 R50}, at same time, it can setup the backup path R10->R30->{R40, 877 R50}. Both the these two primary forwarding path and secondary 878 bypass forwarding path will be downloaded to each routers along the 879 primary path and the secondary bypass path. The traffic will be 880 forwarded through the R10->R20->{R40, R50} path normally, and when 881 there is a node failure for node R20, then the PLR node R10 will 882 switch the flow to the backup path, which is R10->R30->{R40, R50}. 883 By using the PCECC, the path computation and forwarding path 884 downloading can all be done without the complex signaling used in the 885 P2MP RSVP-TE or mLDP. 887 3.5. Use Cases of PCECC for LSP in the Network Migration 889 One of the main advantages for PCECC solution is that it has backward 890 compatibility naturally since the PCE server itself can function as a 891 proxy node of MPLS network for all the new nodes which may no longer 892 support the signaling protocols. 894 As it is illustrated in the following example, the current network 895 could migrate to a total PCECC controlled network gradually by 896 replacing the legacy nodes. During the migration, the legacy nodes 897 still need to signal using the existing MPLS protocol such as LDP and 898 RSVP-TE, and the new nodes setup their portion of the forwarding path 899 through PCECC directly. With the PCECC function as the proxy of 900 these new nodes, MPLS signaling can populate through network as 901 normal. 903 Example described in this section is based on network configurations 904 illustrated using the following figure: 906 +------------------------------------------------------------------+ 907 | PCE DOMAIN | 908 | +-----------------------------------------------------+ | 909 | | PCECC | | 910 | +-----------------------------------------------------+ | 911 | ^ ^ ^ ^ | 912 | | PCEP | | PCEP | | 913 | V V V V | 914 | +--------+ +--------+ +--------+ +--------+ +--------+ | 915 | | NODE 1 | | NODE 2 | | NODE 3 | | NODE 4 | | NODE 5 | | 916 | | |...| |...| |...| |...| | | 917 | | Legacy |if1| Legacy |if2|Legacy |if3| PCECC |if4| PCECC | | 918 | | Node | | Node | |Enabled | |Enabled | | Enabled| | 919 | +--------+ +--------+ +--------+ +--------+ +--------+ | 920 | | 921 +------------------------------------------------------------------+ 923 Example: PCECC Initiated LSP Setup In the Network Migration 925 In this example, there are five nodes for the TE LSP from head end 926 (Node1) to the tail end (Node5). Where the Node4 and Node5 are 927 centrally controlled and other nodes are legacy nodes. 929 o Node1 sends a path request message for the setup of LSP 930 destinating to Node5. 932 o PCECC sends to node1 a reply message for LSP setup with the path: 933 (Node1, if1),(Node2, if2), (Node3, if3), (Node4, if4), Node5. 935 o Node1, Node2, Node3 will setup the LSP to Node5 using the local 936 labels as usual. Node 3 with help of PCECC could proxy the 937 signaling. 939 o Then the PCECC will program the out-segment of Node3, the in- 940 segment/ out-segment of Node4, and the in-segment for Node5. 942 3.6. Use Cases of PCECC for L3VPN and PWE3 944 As described in [RFC8283], various network services may be offered 945 over a network. These include protection services (including Virtual 946 Private Network (VPN) services (such as Layer 3 VPNs [RFC4364] or 947 Ethernet VPNs [RFC7432]); or Pseudowires [RFC3985]. Delivering 948 services over a network in an optimal way requires coordination in 949 the way that network resources are allocated to support the services. 950 A PCE-based central controller can consider the whole network and all 951 components of a service at once when planning how to deliver the 952 service. It can then use PCEP to manage the network resources and to 953 install the necessary associations between those resources. 955 In the case of L3VPN, VPN labels can be assigned and distributed 956 through the PCECC PCEP among the PE router instead of using the BGP 957 protocols. 959 Example described in this section is based on network configurations 960 illustrated using the following figure: 962 +-------------------------------------------+ 963 | PCE DOMAIN | 964 | +-----------------------------------+ | 965 | | PCECC | | 966 | +-----------------------------------+ | 967 | ^ ^ ^ | 968 |PWE3/L3VPN | PCEP PCEP|LSP PWE3/L3VPN|PCEP | 969 | V V V | 970 +--------+ | +--------+ +--------+ +--------+ | +--------+ 971 | CE | | | PE1 | | NODE x | | PE2 | | | CE | 972 | |...... | |...| |...| |.....| | 973 | Legacy | |if1 | PCECC |if2|PCCEC |if3| PCECC |if4 | Legacy | 974 | Node | | | Enabled| |Enabled | |Enabled | | | Node | 975 +--------+ | +--------+ +--------+ +--------+ | +--------+ 976 | | 977 +-------------------------------------------+ 979 Example: Using PCECC for L3VPN and PWE3 981 In the case PWE3, instead of using the LDP signaling protocols, the 982 label and port pairs assigned to each pseudowire can be assigned 983 through PCECC among the PE routers and the corresponding forwarding 984 entries will be distributed into each PE routers through the extended 985 PCEP protocols and PCECC mechanism. 987 3.7. Using PCECC for Traffic Classification Information 989 As described in [RFC8283], traffic classification is an important 990 part of traffic engineering. It is the process of looking at a 991 packet to determine how it should be treated as it is forwarded 992 through the network. It applies in many scenarios including MPLS 993 traffic engineering (where it determines what traffic is forwarded 994 onto which LSPs); segment routing (where it is used to select which 995 set of forwarding instructions to add to a packet); and SFC (where it 996 indicates along which service function path a packet should be 997 forwarded). In conjunction with traffic engineering, traffic 998 classification is an important enabler for load balancing. Traffic 999 classification is closely linked to the computational elements of 1000 planning for the network functions just listed because it determines 1001 how traffic load is balanced and distributed through the network. 1002 Therefore, selecting what traffic classification should be performed 1003 by a router is an important part of the work done by a PCECC. 1005 Instructions can be passed from the controller to the routers using 1006 PCEP. These instructions tell the routers how to map traffic to 1007 paths or connections. Refer [I-D.ietf-pce-pcep-flowspec]. 1009 Along with traffic classification, there are few more question that 1010 needs to be considered once the path is setup - 1012 o how to use it 1014 o Whether it is a virtual link 1016 o Whether to advertise it in the IGP as a virtual link 1018 o What bits of this information to signal to the tail end 1020 These are out of scope of this document. 1022 3.8. Use Cases of PCECC for SRv6 1024 As per [RFC8402], with Segment Routing (SR), a node steers a packet 1025 through an ordered list of instructions, called segments. Segment 1026 Routing can be applied to the IPv6 architecture with the Segment 1027 Routing Header (SRH) [I-D.ietf-6man-segment-routing-header]. A 1028 segment is encoded as an IPv6 address. An ordered list of segments 1029 is encoded as an ordered list of IPv6 addresses in the routing 1030 header. The active segment is indicated by the Destination Address 1031 of the packet. Upon completion of a segment, a pointer in the new 1032 routing header is incremented and indicates the next segment. 1034 As per [I-D.ietf-6man-segment-routing-header], an SRv6 Segment is a 1035 128-bit value. "SRv6 SID" or simply "SID" are often used as a 1036 shorter reference for "SRv6 Segment". Further details are in An 1037 illustration is provided in 1038 [I-D.filsfils-spring-srv6-network-programming] where SRv6 SID is 1039 represented as LOC:FUNCT. 1041 [I-D.ietf-pce-segment-routing-ipv6] extends 1042 [I-D.ietf-pce-segment-routing] to support SR for IPv6 data plane. 1043 Further a PCECC could be extended to support SRv6 SID allocation and 1044 distribution. 1046 2001:db8::1 1047 +----------+ 1048 | R1 | 1049 +----------+ 1050 | 1051 +----------+ 1052 | R2 | 2001:db8::2 1053 +----------+ 1054 * | * * 1055 * | * * 1056 *link1| * * 1057 2001:db8::4 * | *link2 * 2001:db8::5 1058 +-----------+ | * +-----------+ 1059 | R4 | | * | R5 | 1060 +-----------+ | * +-----------+ 1061 * | * * + 1062 * | * * + 1063 * | * * + 1064 +-----------+ +-----------+ 1065 2001:db8::3 | R3 | |R6 |2001:db8::6 1066 +-----------+ +-----------+ 1067 | 1068 +-----------+ 1069 | R8 | 2001:db8::8 1070 +-----------+ 1072 In this case, PCECC could assign the SRv6 SID (in form of a IPv6 1073 address) to be used for node and adjacency. Later SRv6 path in form 1074 of list of SRv6 SID could be used at the ingress. Some examples - 1076 o SRv6 SID-List={2001:db8::8} - The best path towards R8 1078 o SRv6 SID-List={2001:db8::5, 2001:db8::8} - The path towards R8 via 1079 R5 1081 3.9. Use Cases of PCECC for SFC 1083 Service Function Chaining (SFC) is described in [RFC7665]. It is the 1084 process of directing traffic in a network such that it passes through 1085 specific hardware devices or virtual machines (known as service 1086 function nodes) that can perform particular desired functions on the 1087 traffic. The set of functions to be performed and the order in which 1088 they are to be performed is known as a service function chain. The 1089 chain is enhanced with the locations at which the service functions 1090 are to be performed to derive a Service Function Path (SFP). Each 1091 packet is marked as belonging to a specific SFP, and that marking 1092 lets each successive service function node know which functions to 1093 perform and to which service function node to send the packet next. 1094 To operate an SFC network, the service function nodes must be 1095 configured to understand the packet markings, and the edge nodes must 1096 be told how to mark packets entering the network. Additionally, it 1097 may be necessary to establish tunnels between service function nodes 1098 to carry the traffic. Planning an SFC network requires load 1099 balancing between service function nodes and traffic engineering 1100 across the network that connects them. As per [RFC8283], these are 1101 operations that can be performed by a PCE-based controller, and that 1102 controller can use PCEP to program the network and install the 1103 service function chains and any required tunnels. 1105 PCECC can play the role for setting the traffic classification rules 1106 at the classifier as well as downloading the forwarding instructions 1107 to the SFFs so that they could process the NSH and forward 1108 accordingly. 1110 [Editor's Note - more details to be added] 1112 3.10. Use Cases of PCECC for Native IP 1114 [I-D.ietf-teas-native-ip-scenarios] describes the scenarios, and 1115 suggestions for the "Centrally Control Dynamic Routing (CCDR)" 1116 architecture, which integrates the merit of traditional distributed 1117 protocols (IGP/BGP), and the power of centrally control technologies 1118 (PCE/SDN) to provide one feasible traffic engineering solution in 1119 various complex scenarios for the service provider. 1120 [I-D.ietf-teas-pce-native-ip] defines the framework for CCDR traffic 1121 engineering within Native IP network, using Dual/Multi-BGP session 1122 strategy and CCDR architecture. PCEP protocol can be used to 1123 transfer the key parameters between PCE and the underlying network 1124 devices (PCC) using PCECC technique. The central control 1125 instructions from PCECC to identify which prefix should be advertised 1126 on which BGP session. 1128 3.11. Use Cases of PCECC for Local Protection (RSVP-TE) 1130 [I-D.cbrt-pce-stateful-local-protection] describes the need for the 1131 PCE to maintain and associate the local protection paths for the 1132 RSVP-TE LSP. Local protection requires the setup of a bypass at the 1133 PLR. This bypass can be PCC-initiated and delegated, or PCE- 1134 initiated. In either case, the PLR MUST maintain a PCEP session to 1135 the PCE. The Bypass LSPs need to mapped to the primary LSP. This 1136 could be done locally at the PLR based on a local policy but there is 1137 a need for a PCE to do the mapping as well to exert greater control. 1139 This mapping can be done via PCECC procedures where the PCE could 1140 instruct the PLR to the mapping and identify the primary LSP for 1141 which bypass should be used. 1143 4. IANA Considerations 1145 This document does not require any action from IANA. 1147 5. Security Considerations 1149 TBD. 1151 6. Acknowledgments 1153 We would like to thank Adrain Farrel, Aijun Wang, Robert Tao, 1154 Changjiang Yan, Tieying Huang, Sergio Belotti, Dieter Beller, Andrey 1155 Elperin and Evgeniy Brodskiy for their useful comments and 1156 suggestions. 1158 7. References 1160 7.1. Normative References 1162 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1163 Requirement Levels", BCP 14, RFC 2119, 1164 DOI 10.17487/RFC2119, March 1997, 1165 . 1167 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1168 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1169 DOI 10.17487/RFC5440, March 2009, 1170 . 1172 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1173 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1174 May 2017, . 1176 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 1177 Architecture for Use of PCE and the PCE Communication 1178 Protocol (PCEP) in a Network with Central Control", 1179 RFC 8283, DOI 10.17487/RFC8283, December 2017, 1180 . 1182 7.2. Informative References 1184 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 1185 Edge-to-Edge (PWE3) Architecture", RFC 3985, 1186 DOI 10.17487/RFC3985, March 2005, 1187 . 1189 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 1190 Hierarchy with Generalized Multi-Protocol Label Switching 1191 (GMPLS) Traffic Engineering (TE)", RFC 4206, 1192 DOI 10.17487/RFC4206, October 2005, 1193 . 1195 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 1196 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 1197 2006, . 1199 [RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel, 1200 "Label Switched Path Stitching with Generalized 1201 Multiprotocol Label Switching Traffic Engineering (GMPLS 1202 TE)", RFC 5150, DOI 10.17487/RFC5150, February 2008, 1203 . 1205 [RFC5151] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur, "Inter- 1206 Domain MPLS and GMPLS Traffic Engineering -- Resource 1207 Reservation Protocol-Traffic Engineering (RSVP-TE) 1208 Extensions", RFC 5151, DOI 10.17487/RFC5151, February 1209 2008, . 1211 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 1212 Objective Functions in the Path Computation Element 1213 Communication Protocol (PCEP)", RFC 5541, 1214 DOI 10.17487/RFC5541, June 2009, 1215 . 1217 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 1218 Requirements for the Path Computation Element 1219 Communication Protocol (PCECP)", RFC 5376, 1220 DOI 10.17487/RFC5376, November 2008, 1221 . 1223 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 1224 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 1225 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 1226 2015, . 1228 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 1229 Chaining (SFC) Architecture", RFC 7665, 1230 DOI 10.17487/RFC7665, October 2015, 1231 . 1233 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 1234 Computation Element Communication Protocol (PCEP) 1235 Extensions for Stateful PCE", RFC 8231, 1236 DOI 10.17487/RFC8231, September 2017, 1237 . 1239 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 1240 Computation Element Communication Protocol (PCEP) 1241 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 1242 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 1243 . 1245 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1246 Shakir, "Resiliency Use Cases in Source Packet Routing in 1247 Networking (SPRING) Networks", RFC 8355, 1248 DOI 10.17487/RFC8355, March 2018, 1249 . 1251 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1252 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1253 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1254 July 2018, . 1256 [I-D.ietf-pce-segment-routing] 1257 Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 1258 and J. Hardwick, "PCEP Extensions for Segment Routing", 1259 draft-ietf-pce-segment-routing-16 (work in progress), 1260 March 2019. 1262 [I-D.ietf-pce-stateful-hpce] 1263 Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., 1264 and O. Dios, "Hierarchical Stateful Path Computation 1265 Element (PCE).", draft-ietf-pce-stateful-hpce-06 (work in 1266 progress), October 2018. 1268 [I-D.ietf-pce-pcep-flowspec] 1269 Dhody, D., Farrel, A., and Z. Li, "PCEP Extension for Flow 1270 Specification", draft-ietf-pce-pcep-flowspec-03 (work in 1271 progress), February 2019. 1273 [I-D.ietf-pce-pcep-extension-for-pce-controller] 1274 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 1275 and Protocol Extensions for Using PCE as a Central 1276 Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 1277 extension-for-pce-controller-01 (work in progress), 1278 February 2019. 1280 [I-D.zhao-pce-pcep-extension-pce-controller-sr] 1281 Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures 1282 and Protocol Extensions for Using PCE as a Central 1283 Controller (PCECC) of SR-LSPs", draft-zhao-pce-pcep- 1284 extension-pce-controller-sr-04 (work in progress), 1285 February 2019. 1287 [I-D.li-pce-controlled-id-space] 1288 Li, C., Chen, M., Dong, J., Li, Z., Wang, A., and C. Zhou, 1289 "PCE Controlled ID Space", draft-li-pce-controlled-id- 1290 space-02 (work in progress), March 2019. 1292 [I-D.dugeon-pce-stateful-interdomain] 1293 Dugeon, O., Meuric, J., Lee, Y., and D. Ceccarelli, "PCEP 1294 Extension for Stateful Inter-Domain Tunnels", draft- 1295 dugeon-pce-stateful-interdomain-02 (work in progress), 1296 March 2019. 1298 [I-D.cbrt-pce-stateful-local-protection] 1299 Barth, C. and R. Torvi, "PCEP Extensions for RSVP-TE 1300 Local-Protection with PCE-Stateful", draft-cbrt-pce- 1301 stateful-local-protection-01 (work in progress), June 1302 2018. 1304 [I-D.filsfils-spring-srv6-network-programming] 1305 Filsfils, C., Camarillo, P., Leddy, J., 1306 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 1307 Network Programming", draft-filsfils-spring-srv6-network- 1308 programming-07 (work in progress), February 2019. 1310 [I-D.ietf-pce-segment-routing-ipv6] 1311 Negi, M., Li, C., Sivabalan, S., and P. Kaladharan, "PCEP 1312 Extensions for Segment Routing leveraging the IPv6 data 1313 plane", draft-ietf-pce-segment-routing-ipv6-00 (work in 1314 progress), March 2019. 1316 [I-D.ietf-6man-segment-routing-header] 1317 Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and 1318 d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header 1319 (SRH)", draft-ietf-6man-segment-routing-header-16 (work in 1320 progress), February 2019. 1322 [I-D.ietf-teas-pce-native-ip] 1323 Wang, A., Zhao, Q., Khasanov, B., Chen, H., and R. Mallya, 1324 "PCE in Native IP Network", draft-ietf-teas-pce-native- 1325 ip-02 (work in progress), October 2018. 1327 [I-D.ietf-teas-native-ip-scenarios] 1328 Wang, A., Huang, X., Qou, C., Li, Z., and P. Mi, 1329 "Scenario, Simulation and Suggestion of PCE in Native IP 1330 Network", draft-ietf-teas-native-ip-scenarios-02 (work in 1331 progress), October 2018. 1333 [MAP-REDUCE] 1334 Lee, K., Choi, T., Ganguly, A., Wolinsky, D., Boykin, P., 1335 and R. Figueiredo, "Parallel Processing Framework on a P2P 1336 System Using Map and Reduce Primitives", , may 2011, 1337 . 1339 [MPLS-DC] Afanasiev, D. and D. Ginsburg, "MPLS in DC and inter-DC 1340 networks: the unified forwarding mechanism for network 1341 programmability at scale", , march 2014, 1342 . 1345 7.3. URIs 1347 [1] https://hadoop.apache.org/ 1349 Appendix A. Using reliable P2MP TE based multicast delivery for 1350 distributed computations (MapReduce-Hadoop) 1352 MapReduce model of distributed computations in computing clusters is 1353 widely deployed. In Hadoop [1] 1.0 architecture MapReduce operations 1354 on big data performs by means of Master-Slave architecture in the 1355 Hadoop Distributed File System (HDFS), where NameNode has the 1356 knowledge about resources of the cluster and where actual data 1357 (chunks) for particular task are located (which DataNode). Each 1358 chunk of data (64MB or more) should have 3 saved copies in different 1359 DataNodes based on their proximity. 1361 Proximity level currently has semi-manual allocation and based on 1362 Rack IDs (Assumption is that closer data are better because of access 1363 speed/smaller latency). 1365 JobTracker node is responsible for computation tasks, scheduling 1366 across DataNodes and also have Rack-awareness. Currently transport 1367 protocols between NameNode/JobTracker and DataNodes are based on IP 1368 unicast. It has simplicity as pros but has numerous drawbacks 1369 related with its flat approach. 1371 It is clear that we should go beyond of one DC for Hadoop cluster 1372 creation and move towards distributed clusters. In that case we need 1373 to handle performance and latency issues. Latency depends on speed 1374 of light in fiber links and also latency introduced by intermediate 1375 devices in between. The last one is closely correlated with network 1376 device architecture and performance. Current performance of NPU 1377 based routers should be enough for creating distribute Hadoop 1378 clusters with predicted latency. Performance of SW based routers 1379 (mainly as VNF) together with additional HW features such as DPDK are 1380 promising but require additional research and testing. 1382 Main question is how can we create simple but effective architecture 1383 for distributed Hadoop cluster? 1385 There is research [MAP-REDUCE] which show how usage of multicast tree 1386 could improve speed of resource or cluster members discovery inside 1387 the cluster as well as increase redundancy in communications between 1388 cluster nodes. 1390 Is traditional IP based multicast enough for that? We doubt it 1391 because it requires additional control plane (IGMP, PIM) and a lot of 1392 signaling, that is not suitable for high performance computations, 1393 that are very sensitive to latency. 1395 P2MP TE tunnels looks much more suitable as potential solution for 1396 creation of multicast based communications between Master and Slave 1397 nodes inside cluster. Obviously these P2MP tunnels should be 1398 dynamically created and turned down (no manual intervention). Here, 1399 the PCECC comes to play with main objective to create optimal 1400 topology of each particular request for MapReduce computation and 1401 also create P2MP tunnels with needed parameters such as bandwidth and 1402 delay. 1404 This solution would require to use MPLS label based forwarding inside 1405 the cluster. Usage of label based forwarding inside DC was proposed 1406 by Yandex [MPLS-DC]. Technically it is already possible because MPLS 1407 on switches is already supported by some vendors, MPLS also exists on 1408 Linux and OVS. 1410 The following framework can make this task: 1412 +--------+ 1413 | APP | 1414 +--------+ 1415 | NBI (REST API,...) 1416 | 1417 PCEP +----------+ REST API 1418 +---------+ +---| PCECC |----------+ 1419 | Client |---|---| | | 1420 +---------+ | +----------+ | 1421 | | | | | | 1422 +-----|---+ |PCEP| | 1423 +--------+ | | | | | 1424 | | | | | | 1425 | REST API | | | | | 1426 | | | | | | 1427 +-------------+ | | | | +----------+ 1428 | Job Tracker | | | | | | NameNode | 1429 | | | | | | | | 1430 +-------------+ | | | | +----------+ 1431 +------------------+ | +-----------+ 1432 | | | | 1433 |---+-----P2MP TE--+-----|-----------| | 1434 +----------+ +----------+ +----------+ 1435 | DataNode1| | DataNode2| | DataNodeN| 1436 |TaskTraker| |TaskTraker| .... |TaskTraker| 1437 +----------+ +----------+ +----------+ 1439 Communication between Master nodes (JobTracker and NameNode) and 1440 PCECC via REST API MAY be either done directly or via cluster manager 1441 such as Mesos. 1443 Phase 1: Distributed cluster resources discovery During this phase 1444 Master Nodes SHOULD identify and find available Slave nodes according 1445 to computing request from application (APP). NameNode SHOULD query 1446 PCECC about available DataNodes, NameNode MAY provide additional 1447 constrains to PCECC such as topological proximity, redundancy level. 1449 PCECC SHOULD analyze the topology of distributed cluster and perform 1450 constrain based path calculation from client towards most suitable 1451 NameNodes. PCECC SHOULD reply to NameNode the list of most suitable 1452 DataNodes and their resource capabilities. Topology discovery 1453 mechanism for PCECC will be added later to that framework. 1455 Phase 2: PCECC SHOULD create P2MP LSP from client towards those 1456 DataNodes by means of PCEP messages following previously calculated 1457 path. 1459 Phase 3. NameNode SHOULD send this information to client, PCECC 1460 informs client about optimal P2MP path towards DataNodes via PCEP 1461 message. 1463 Phase 4. Client sends data blocks to those DataNodes for writing via 1464 created P2MP tunnel. 1466 When this task will be finished, P2MP tunnel could be turned down. 1468 Authors' Addresses 1470 Quintin Zhao 1471 Huawei Technologies 1472 125 Nagog Technology Park 1473 Acton, MA 01719 1474 US 1476 Email: quintin.zhao@huawei.com 1478 Zhenbin (Robin) Li 1479 Huawei Technologies 1480 Huawei Bld., No.156 Beiqing Rd. 1481 Beijing 100095 1482 China 1484 Email: lizhenbin@huawei.com 1486 Boris Khasanov 1487 Huawei Technologies 1488 Moskovskiy Prospekt 97A 1489 St.Petersburg 196084 1490 Russia 1492 Email: khasanov.boris@huawei.com 1494 Dhruv Dhody 1495 Huawei Technologies 1496 Divyashree Techno Park, Whitefield 1497 Bangalore, Karnataka 560066 1498 India 1500 Email: dhruv.ietf@gmail.com 1501 King Ke 1502 Tencent Holdings Ltd. 1503 Shenzhen 1504 China 1506 Email: kinghe@tencent.com 1508 Luyuan Fang 1509 Expedia, Inc. 1510 USA 1512 Email: luyuanf@gmail.com 1514 Chao Zhou 1515 Cisco Systems 1517 Email: chao.zhou@cisco.com 1519 Boris Zhang 1520 Telus Communications 1522 Email: Boris.zhang@telus.com 1524 Artem Rachitskiy 1525 Mobile TeleSystems JLLC 1526 Nezavisimosti ave., 95 1527 Minsk 220043 1528 Belarus 1530 Email: arachitskiy@mts.by 1532 Anton Gulida 1533 LLC "Lifetech" 1534 Krasnoarmeyskaya str., 24 1535 Minsk 220030 1536 Belarus 1538 Email: anton.gulida@life.com.by