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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ALTO WG J. Zhang 3 Internet-Draft Tongji University 4 Intended status: Informational K. Gao 5 Expires: 14 January 2021 Sichuan University 6 LM. Contreras 7 Telefonica 8 A. Escribano 9 Alten 10 P. Cano 11 UST Global 12 F. Cano 13 Telefonica 14 13 July 2020 16 Considerations of Deploying ALTO using BGP - Link State (BGP-LS) 17 Advertisement 18 draft-zhang-alto-bgp-ls-01 20 Abstract 22 This document discusses the requirements and deployment 23 considerations of providing Application-Layer Traffic Optimization 24 (ALTO) information in the inter-domain scenario using Border Gateway 25 Protocol - Link State (BGP-LS) extension. 27 Requirements Language 29 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 30 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 31 document are to be interpreted as described in [RFC2119]. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on 14 January 2021. 50 Copyright Notice 52 Copyright (c) 2020 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 57 license-info) in effect on the date of publication of this document. 58 Please review these documents carefully, as they describe your rights 59 and restrictions with respect to this document. Code Components 60 extracted from this document must include Simplified BSD License text 61 as described in Section 4.e of the Trust Legal Provisions and are 62 provided without warranty as described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 67 2. New Problem Statement and Working Items . . . . . . . . . . . 3 68 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 3.1. ALTO Inter-domain Deployment Problem . . . . . . . . . . 4 70 3.2. BGP-LS Background and Benefits for ALTO . . . . . . . . . 4 71 3.3. ALTO Deployment Problem using BGP-LS . . . . . . . . . . 5 72 4. Requirements for Deploying ALTO in the Inter-domain Scenario 73 using BGP-LS . . . . . . . . . . . . . . . . . . . . . . 6 74 4.1. Basic Requirements . . . . . . . . . . . . . . . . . . . 6 75 4.2. BGP-LS specific Requirements . . . . . . . . . . . . . . 6 76 5. ALTO Deployment Considerations using BGP-LS . . . . . . . . . 7 77 5.1. Provisioning of Topology Information . . . . . . . . . . 7 78 5.2. Provisioning of Routing Information . . . . . . . . . . . 7 79 5.3. Provisioning of Performance Metric Information . . . . . 7 80 6. Configuration Interfaces of Map Calculation . . . . . . . . . 7 81 6.1. Configuration Interface of Network Map Calculation . . . 7 82 6.2. Configuration Interface of Cost Map Calculation . . . . . 8 83 6.3. Configuration Examples . . . . . . . . . . . . . . . . . 9 84 7. Test Scenarios . . . . . . . . . . . . . . . . . . . . . . . 14 85 7.1. Test Environment Setup . . . . . . . . . . . . . . . . . 14 86 7.2. Test Approach . . . . . . . . . . . . . . . . . . . . . . 14 87 7.3. Test Results . . . . . . . . . . . . . . . . . . . . . . 14 88 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 89 8.1. Normative References . . . . . . . . . . . . . . . . . . 14 90 8.2. Informative References . . . . . . . . . . . . . . . . . 14 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 93 1. Introduction 95 The major component of the Application-Layer Traffic Optimization 96 (ALTO) [RFC7285] deployment is the network information collection. 97 [RFC7971] discussed multiple options to collect the network 98 information from the inter-domain networks. 100 To collection the related network information for ALTO, the following 101 high-level questions should be considered: 103 * Can the ALTO service realistically discover that information? 105 * Is the distribution of that information allowed by the operators 106 of that service? 108 * Is it information that a client cannot find easily some other way? 110 The Border Gateway Protocol - Link State (BGP-LS) extension [RFC7752] 111 is one of the popular options and has been deployed in many 112 Autonomous Systems (ASes) in recent years [TODO: Need some 113 reference]. 115 BGP-LS enables ALTO server to provide underlay inter-domain topology 116 information using the link-state information in IGP domains. 118 To leverage BGP-LS to generate ALTO information effectively, some 119 requirements for deployment should be considered. 121 This document discusses these requirements and the corresponding 122 deployment considerations. 124 Additionally, this document describes some inter-domain scenarios to 125 test the deployment. 127 2. New Problem Statement and Working Items 129 This document was initially written to summarize ALTO deployment 130 consideration using BGP-LS. However, authors are finding new 131 interesting practical problems when pushing the deployment to large- 132 scale ISP networks. 134 Authors identify two problems: 136 Problem 1: how to efficiently obtain fine-grained global ALTO 137 information from multiple networks? 139 Problem 2: how to efficiently reconstruct and disseminate the ALTO 140 information upon dynamics? 141 Considering the scale of the ISP carrier networks and the frequency 142 of network dynamicity, the previous design cannot survive. We have 143 to target a systemtic design to support (1) distributed information 144 collection, and (2) calculation and incremental information 145 recomputation. 147 Thus, authors propose a hierarchical architecture to deploy ALTO 148 servers. To make the deployment in different small networks 149 compatible with each other, the interfaces to allow interoperations 150 between different ALTO servers are required. Although we can design 151 and implement those interfaces outside the scope of ALTO, we believe 152 making ALTO provide this capability by itself can be a more coherent 153 approach and also have more potential benefits. 155 We are still heavily working on the initial specification. No more 156 details are added in the current document. But we have already done 157 a paper submission to talk about the initial design. For people 158 interested in this work, please feel free to contact us. 160 3. Background 162 3.1. ALTO Inter-domain Deployment Problem 164 [RFC7971] discusses considerations of ALTO deployment in different 165 network scenarios. The inter-domain network is the most common 166 scenario to deploy ALTO. 168 In practice, the following approaches are used to collect information 169 from the network: 171 * Interior Gateway Protocols (IGPs, e.g., OSPF, IS-IS): intra-domain 172 topology, link weights 174 * Border Gateway Protocol (BGP): inter-domain topology, prefixes, AS 175 numbers, AS distances, or other BGP metrics 177 * Network Management Protocols (NMPs, e.g., SNMP, Netconf): latency, 178 utilization, bandwidth 180 3.2. BGP-LS Background and Benefits for ALTO 182 BGP-LS [RFC7752] is designed to allow a BGP speaker to advertise the 183 link state database (LSDB) or traffic engineering database (TED) of 184 its connected IGP area. 186 BGP-LS defines a new address family, link state, in the BGPv4 187 framework [RFC4271]. 189 Using BGP-LS, the ALTO server can communicate to only BGP speakers to 190 collect all those information. 192 3.3. ALTO Deployment Problem using BGP-LS 194 A simple deployment solution is to connect the ALTO server as a BGP 195 reflector client of every BGP speakers in the network. However, this 196 solution is expensive and redundant. And because of the BGP updates, 197 the ALTO server could receive a lot of inconsistent redundant 198 informaiton. To avoid the redundancy and inconsistency of the 199 collected information, a deployment solution should be minimal. 201 To understand what is a minimal solution to deploy ALTO using BGP-LS, 202 the following questions are raised: 204 * Is it necessary to connect the ALTO server to every AS within a 205 BGP session? 207 * Does the session between the ALTO server and each AS have to 208 enable BGP-LS? 210 * If using BGP-LS, can the number of necessary BGP sessions be 211 reduced? 213 The following example shows a minimal deployment in a simple example 214 topology. 216 Consider the following AS-level topology as an example. Assuming all 217 the BGP sessions between ASes have enabled BGP-LS, the BGP speaker on 218 AS B can received the IGP topologies from all the three ASes. Thus, 219 to make sure the ALTO server collect all the inter-domain and intra- 220 domain topology information, the minimal deployment could be to set 221 up the the ALTO server as a BGP reflector of the BGP speaker on AS B. 223 +--------+ +--------+ +---------+ 224 | AS A |---| AS B |---| AS C | 225 +--------+ +--------+ +---------+ 226 | BGP / BGP-LS 227 | / 228 | / 229 +-------------+ 230 | ALTO Server | 231 +-------------+ 233 Figure 1: Example AS-level Topology 235 However, it is not enough for collecting the routing information. As 236 the BGP is a destination-based routing protocol, AS B could not 237 receive the routing information between endpoints from AS A and AS C. 238 To get the missing routing information, the ALTO server should also 239 connect read the BGP RIB of AS A or AS C at least. 241 As the result, the minimal solution is to establish a BGP session to 242 AS B with BGP-LS and another BGP session to AS A (or AS C) without 243 BGP-LS. 245 The following part of this document will discuss how to achieve the 246 minimal ALTO deployment using BPG-LS in detail. Specifically, two 247 questions are required to be answered: 249 * Which BGP speakers are required to be connected to the ALTO 250 server? 252 * Which BGP sessions are required to enable BGP-LS? 254 4. Requirements for Deploying ALTO in the Inter-domain Scenario using 255 BGP-LS 257 4.1. Basic Requirements 259 The following basic requirements are required by ALTO inter-domain 260 deployment in any case. 262 Req 1: The ALTO server MUST be able to collect topology information 263 from multiple IGP areas. 265 Req 2: The ALTO server MUST be able to collect routing information 266 for any pairs of endpoints. 268 Req 3: The ALTO server MUST be able to collect performance metrics 269 across routes. 271 4.2. BGP-LS specific Requirements 273 The following additional requirements are required by ALTO deployment 274 when using BGP-LS. 276 Req 4: The ALTO server SHOULD only communicate with necessary BGP 277 speakers. 279 Req 5: The ALTO server SHOULD only enable BGP-LS advertisement in 280 necessary BGP sessions between BGP speakers. 282 5. ALTO Deployment Considerations using BGP-LS 284 This section discusses some deployment considerations about how to 285 address the basic requirements (Req 1-3) when satisfying the BGP-LS 286 specific requirements (Req 4-5). 288 5.1. Provisioning of Topology Information 290 As BGP-LS advertisement cannot be propagated to remote the remote 291 ASes, each BGP speaker can only discover directly peered IGP 292 topologies using BGP-LS. 294 To satisfy Req 4, the ALTO server should only communicate to transit 295 networks or IXPs using BGP-LS. As the IGP topology of a stub network 296 can always be discovered by its peered transit networks or IXPs, so 297 it is not necessary to communicate with the stub network. 299 Specifically, the ALTO server should find a minimal BGP speaker set 300 whose peered networks can cover all IGP domains. 302 5.2. Provisioning of Routing Information 304 As BGP is a destination-based routing protocol, a stub network can 305 receive all the inter-domain routing information from all the 306 reachable destinations via BGP. 308 Thus, to satisfy Req 4, the ALTO server should only communicate to 309 stub networks using BGP, as the inter-domain routing information from 310 the transit networks is not necessary. 312 Assuming the ALTO server has already collected the complete topology 313 information using BGP-LS, the ALTO server will have the LSDB of every 314 IGP domain. 316 To satisfy Req 5, all the BGP sessions connected to the stub networks 317 do not have to enable BGP-LS. 319 5.3. Provisioning of Performance Metric Information 321 TBD. 323 6. Configuration Interfaces of Map Calculation 325 6.1. Configuration Interface of Network Map Calculation 326 rw network-map-config* [resource-id] 327 +--rw resource-id alto-types:resource-id 328 +--rw description? string 329 +--rw (params) 330 | +--:(bgp) 331 | +--rw bgp-params 332 | +--rw bgp-rib* [rib-id] 333 | +--rw rib-id rib:rib-id 334 | +--rw topology-id? topology:topology-id 335 | +--rw bgp-ls? boolean 336 +--rw (algorithm) 337 +--:(first-hop-cluster) 338 +--rw first-hop-cluster-algorithm 339 +--rw inspect-igp boolean 341 To generate a network map, one or more BGP RIBs that could provide 342 the topology information MUST specified. Each BGP RIB MAY include a 343 pre-computed topology from the RIB, and an option indicating if the 344 BPG-LS is enabled. 346 The "inspect-igp" option in the "first-hop-cluster-algorithm" field 347 indicates if the ALTO server exposes information about the IGP 348 topologies. If it is true, the ALTO server will inspect all the IGP 349 topolgies from the BGP RIBs that enalbe BGP-LS (whose "bgp-ls" option 350 is true). 352 6.2. Configuration Interface of Cost Map Calculation 354 rw cost-map-config* [resource-id] 355 +--rw resource-id alto-types:resource-id 356 +--rw description? string 357 +--rw dependent-network-map alto-types:resource-id 358 +--rw (general-params) 359 | +--:(bgp) 360 | +--rw bgp-params 361 | +--rw alternative-bgp-rib* [rib-id] 362 | +--rw rib-id rib:rib-id 363 | +--rw topology-id? topology:topology-id 364 | +--rw bgp-ls? boolean 365 +--rw cost-type* [cost-mode,cost-metric] 366 +rw cost-mode alto-types:cost-mode 367 +rw cost-metric alto-types:cost-metric 368 +rw (params)? 370 To generate a cost map, besides the dependent network map, one or 371 more alternative BGP RIBs could be specified to provide necessary 372 routing information to the ALTO server. 374 6.3. Configuration Examples 376 Example Network 378 .----------------------------. .------------. 379 | 1.1.1.0/24 6.6.6.0/24 | | 8.8.8.0/24 | 380 | | | | | | | 381 | +-+--+ +-+--+ | | +-+--+ | 382 | | R1 +--------+ R6 | | .------------. | | R8 | | 383 | +-+--+ +-+--+ | | 3.3.3.0/24 | | +-+--+ | 384 | | | | | | | | | | 385 | | +-+--+ | | +-+--+ | | +-+--+ | 386 | +-----------+ R2 +- - -|- - | -+ R3 +- - | -|- -+ R7 | | 387 | +----+ | | +++--+ | | +----+ | 388 | | | | .. | | | 389 | +-+--+ | | ..AS 200 | | AS 300 | 390 | 5.5.5.0/24------+ R5 | | `------------' `------------' 391 | +-+--+ | .. 392 | | | .. 393 | AS 100 +-+--+ | .. 394 | | R4 +- - -|- - - - +. 395 | +-+--+ | . 396 `----------------------------' . 397 . . 398 . . 399 . +--------+----+ 400 +- - - - -+ ALTO Server | 401 +-------------+ 403 R2 - R3: BGP-LS 404 R4 - R3: BGP-LS 405 R7 - R3: BGP-LS 406 R3 - ALTO: BGP-LS 407 R4 - ALTO: BGP 409 Figure 2 411 Config a network map: 413 POST /restconf/config/alto-maps/network-map-config/bgp-networkmap 414 HOST: alto-config.example.com 415 Content-Type: application/json 416 Content-Length: TBD 418 { 419 "network-map-config": { 420 "resource-id": "bgp-networkmap", 421 "bgp-params": { 422 "bgp-rib": [ 423 { 424 "rib-id": "as200-r3", 425 "bgp-ls": true 426 } 427 ] 428 }, 429 "first-hop-cluster-algorithm": { 430 "inspect-igp": true 431 } 432 } 433 } 435 Test to fetch the network map: 437 GET /alto/networkmap/example 438 HOST: alto.example.com 440 HTTP/1.1 200 OK 441 Content-Length: TBD 442 Content-Type: application/alto-networkmap+json 444 { 445 "meta": { 446 "vtag": { 447 "resource-id": "bgp-networkmap", 448 "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785" 449 } 450 }, 451 { 452 "network-map": { 453 "PID100.R1": { 454 "ipv4": [ "1.1.1.0/24" ] 455 }, 456 "PID100.R5": { 457 "ipv4": [ "5.5.5.0/24" ] 458 }, 459 "PID100.R6": { 460 "ipv4": [ "6.6.6.0/24" ] 461 }, 462 "PID200.R3": { 463 "ipv4": [ "3.3.3.0/24" ] 464 }, 465 "PID300.R8": { 466 "ipv4": [ "8.8.8.0/24" ] 467 } 468 } 469 } 470 } 472 Config a cost map: 474 POST /restconf/config/alto-maps/cost-map-config/bgp-costmap 475 HOST: alto-config.example.com 476 Content-Type: application/json 477 Content-Length: TBD 479 { 480 "cost-map-config": { 481 "resource-id": "bgp-costmap", 482 "dependent-network-map": "bgp-networkmap", 483 "bgp-params": { 484 "alternative-bgp-rib": [ 485 { 486 "rib-id": "as100-r4", 487 "bgp-ls": false 488 } 489 ] 490 }, 491 "cost-type": [ 492 { 493 "cost-mode": "numerical", 494 "cost-metric": "hopcount" 495 } 496 ] 497 } 498 } 500 Test to fetch the cost map: 502 GET /alto/costmap/bgp-costmap 503 HOST: alto.example.com 505 HTTP/1.1 200 OK 506 Content-Length: TBD 507 Content-Type: application/alto-costmap+json 509 { 510 "meta": { 511 "vtag": { 512 "resource-id": "bgp-costmap", 513 "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d" 514 }, 515 "dependent-vtags": [ 516 { 517 "resource-id": "bgp-networkmap", 518 "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785" 519 } 520 ], 521 "cost-type": { 522 "cost-mode": "numerical", 523 "cost-metric": "hopcount" 524 } 525 }, 526 "cost-map": { 527 "PID100.R1": { 528 "PID100.R1": 1, "PID100.R5": 3, "PID100.R6": 2, 529 "PID200.R3": 3, "PID300.R8": 5 530 }, 531 "PID100.R5": { 532 "PID100.R1": 3, "PID100.R5": 1, "PID100.R6": 3, 533 "PID200.R3": 3, "PID300.R8": 5 534 }, 535 "PID100.R6": { 536 "PID100.R1": 2, "PID100.R5": 3, "PID100.R6": 1, 537 "PID200.R3": 3, "PID300.R8": 5 538 }, 539 "PID200.R3": { 540 "PID100.R1": 3, "PID100.R5": 3, "PID100.R6": 3, 541 "PID200.R3": 1, "PID300.R8": 3 542 }, 543 "PID300.R8": { 544 "PID100.R1": 5, "PID100.R5": 5, "PID100.R6": 5, 545 "PID200.R3": 3, "PID300.R8": 1 546 } 547 } 548 } 550 7. Test Scenarios 552 7.1. Test Environment Setup 554 7.2. Test Approach 556 7.3. Test Results 558 8. References 560 8.1. Normative References 562 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 563 Requirement Levels", BCP 14, RFC 2119, 564 DOI 10.17487/RFC2119, March 1997, 565 . 567 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 568 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 569 DOI 10.17487/RFC4271, January 2006, 570 . 572 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 573 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 574 "Application-Layer Traffic Optimization (ALTO) Protocol", 575 RFC 7285, DOI 10.17487/RFC7285, September 2014, 576 . 578 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 579 S. Ray, "North-Bound Distribution of Link-State and 580 Traffic Engineering (TE) Information Using BGP", RFC 7752, 581 DOI 10.17487/RFC7752, March 2016, 582 . 584 [RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and 585 S. Previdi, "Application-Layer Traffic Optimization (ALTO) 586 Deployment Considerations", RFC 7971, 587 DOI 10.17487/RFC7971, October 2016, 588 . 590 [RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and 591 C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of 592 IGP Traffic Engineering Performance Metric Extensions", 593 RFC 8571, DOI 10.17487/RFC8571, March 2019, 594 . 596 8.2. Informative References 598 [I-D.ietf-alto-cost-calendar] 599 Randriamasy, S., Yang, Y., WU, Q., Lingli, D., and N. 600 Schwan, "Application-Layer Traffic Optimization (ALTO) 601 Cost Calendar", Work in Progress, Internet-Draft, draft- 602 ietf-alto-cost-calendar-21, 17 March 2020, 603 . 606 [I-D.ietf-alto-incr-update-sse] 607 Roome, W. and Y. Yang, "ALTO Incremental Updates Using 608 Server-Sent Events (SSE)", Work in Progress, Internet- 609 Draft, draft-ietf-alto-incr-update-sse-22, 20 March 2020, 610 . 613 [I-D.ietf-alto-path-vector] 614 Gao, K., Randriamasy, S., Yang, Y., and J. Zhang, "ALTO 615 Extension: Path Vector", Work in Progress, Internet-Draft, 616 draft-ietf-alto-path-vector-10, 9 March 2020, 617 . 620 [I-D.ietf-alto-unified-props-new] 621 Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K. 622 Gao, "Unified Properties for the ALTO Protocol", Work in 623 Progress, Internet-Draft, draft-ietf-alto-unified-props- 624 new-11, 9 March 2020, . 627 [I-D.wang-idr-bgpls-inter-as-topology-ext] 628 Wang, A. and H. Chen, "BGP-LS Extension for Inter-AS 629 Topology Retrieval", Work in Progress, Internet-Draft, 630 draft-wang-idr-bgpls-inter-as-topology-ext-02, 13 August 631 2018, . 634 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 635 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 636 DOI 10.17487/RFC8189, October 2017, 637 . 639 Authors' Addresses 640 Jingxuan Jensen Zhang 641 Tongji University 642 4800 Cao'An Hwy 643 Shanghai 644 201804 645 China 647 Email: jingxuan.zhang@tongji.edu.cn 649 Kai Gao 650 Sichuan University 651 No.24 South Section 1, Yihuan Road 652 Chengdu 653 610000 654 China 656 Email: kaigao@scu.edu.cn 658 Luis M. Contreras 659 Telefonica 660 Ronda de la Comunicacion, s/n 661 28050 Madrid 662 Spain 664 Email: luismiguel.contrerasmurillo@telefonica.com 666 Anais Escribano 667 Alten 668 Carrer de Josep Pla, 2 669 08019 Barcelona 670 Spain 672 Email: anais.escribano@alten.es 674 Patricia Cano 675 UST Global 676 Ramirez de Arellano 29 677 28043 Madrid 678 Spain 680 Email: Patricia.Diez@ust-global.com 681 Francisco Cano 682 Telefonica 683 Avenida del Conocimiento, 12 684 18016 Granada 685 Spain 687 Email: franciscojose.canohila@telefonica.com