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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group X. Xu 3 Internet-Draft Huawei 4 Intended status: Standards Track C. Filsfils 5 Expires: February 11, 2018 A. Bashandy 6 Cisco 7 R. Raszuk 8 Bloomberg LP 9 U. Chunduri 10 Huawei 11 L. Contreras 12 Telefonica I+D 13 L. Jalil 14 Verizon 15 H. Assarpour 16 Broadcom 17 G. Van De Velde 18 Nokia 19 J. Tantsura 20 Individual 21 S. Ma 22 Juniper 23 T. Mizrahi 24 Marvell 25 August 10, 2017 27 Unified Source Routing Instructions using MPLS Label Stack 28 draft-xu-mpls-unified-source-routing-instruction-03 30 Abstract 32 MPLS Segment Routing (SR-MPLS in short) is an MPLS data plane-based 33 source routing paradigm in which a sender of a packet is allowed to 34 partially or completely specify the route the packet takes through 35 the network by imposing stacked MPLS labels to the packet. SR-MPLS 36 could be leveraged to realize a unified source routing mechanism 37 across MPLS, IPv4 and IPv6 data planes by using an MPLS label stack 38 as a unified source routing instruction set while preserving backward 39 compatibility with SR-MPLS. 41 Status of This Memo 43 This Internet-Draft is submitted in full conformance with the 44 provisions of BCP 78 and BCP 79. 46 Internet-Drafts are working documents of the Internet Engineering 47 Task Force (IETF). Note that other groups may also distribute 48 working documents as Internet-Drafts. The list of current Internet- 49 Drafts is at http://datatracker.ietf.org/drafts/current/. 51 Internet-Drafts are draft documents valid for a maximum of six months 52 and may be updated, replaced, or obsoleted by other documents at any 53 time. It is inappropriate to use Internet-Drafts as reference 54 material or to cite them other than as "work in progress." 56 This Internet-Draft will expire on February 11, 2018. 58 Copyright Notice 60 Copyright (c) 2017 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (http://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 76 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 77 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 78 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 79 4. Packet Forwarding Procedures . . . . . . . . . . . . . . . . 4 80 4.1. Forwarding Entry Construction . . . . . . . . . . . . . . 5 81 4.2. Packet Forwarding Procedures . . . . . . . . . . . . . . 6 82 5. Signalling Considerations . . . . . . . . . . . . . . . . . . 9 83 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 84 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 85 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 86 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 87 9.1. Normative References . . . . . . . . . . . . . . . . . . 10 88 9.2. Informative References . . . . . . . . . . . . . . . . . 10 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 91 1. Introduction 93 MPLS Segment Routing (SR-MPLS in short) 94 [I-D.ietf-spring-segment-routing-mpls] is an MPLS data plane-based 95 source routing paradigm in which a sender of a packet is allowed to 96 partially or completely specify the route the packet takes through 97 the network by imposing stacked MPLS labels to the packet. SR-MPLS 98 could be leveraged to realize a unified source routing mechanism 99 across MPLS, IPv4 and IPv6 data planes by using an MPLS label stack 100 as a unified source routing instruction set while preserving backward 101 compatibility with SR-MPLS. More specifically, the source routing 102 instruction set information contained in a source routed packet could 103 be uniformly encoded as an MPLS label stack no matter the underlay is 104 IPv4, IPv6 or MPLS. 106 Although the source routing instructions are encoded as MPLS labels, 107 this is a hardware convenience rather than an indication that the 108 whole MPLS protocol stack and in particular the MPLS control 109 protocols need to be deployed. Note that the complexity associated 110 with the whole MPLS protocol stack is largely due to the complex 111 control plane protocols. 113 Section 3 describes various use cases for the unified source routing 114 instruction mechanism and Section 4 describes a typical application 115 scenario and how the packet forwarding happens. 117 1.1. Requirements Language 119 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 120 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 121 document are to be interpreted as described in RFC 2119 [RFC2119]. 123 2. Terminology 125 This memo makes use of the terms defined in [RFC3031] and 126 [I-D.ietf-spring-segment-routing-mpls]. 128 3. Use Cases 130 The unified source routing mechanism across IPv4, IPv6 and MPLS is 131 useful at least in the following use cases: 133 o Incremental deployment of the SR-MPLS technology 134 [I-D.xu-mpls-spring-islands-connection-over-ip]. Since there is 135 no need to run any other label distribution protocol (e.g., LDP, 136 see [I-D.ietf-spring-segment-routing-ldp-interop] for more 137 details.) on those non-SR-MPLS routers for incremental deployment 138 purposes, the network provisioning is greatly simplified, which is 139 one of the major claimed benefits of the SR-MPLS technology (i.e., 140 running a single protocol). 142 o Overcome the load-balancing dilemma encountered by SR-MPLS. In 143 fact, this unified source routing mechanism is even useful in a 144 fully upgraded SR-MPLS network since the load-balancing dilemma 145 encountered by SR-MPLS due to the maximum Readable Label-stack 146 Depth (RLD) hardware limitation 147 [I-D.ietf-mpls-spring-entropy-label] and the Maximum SID Depth 148 (MSD) hardware limitation [I-D.ietf-ospf-segment-routing-msd] by 149 using the MPLS-in-UDP encapsulation [RFC7510] where the source 150 port of the UDP tunnel header is used as an entropy field. 152 o A poor man's light-weight alternative to SRv6 153 [I-D.ietf-6man-segment-routing-header]. At least, it could be 154 deployed as an interim until full featured SRv6 is available on 155 more platforms. Since the Source Routing Header (SRH) 156 [I-D.ietf-6man-segment-routing-header] consisting of an ordered 157 list of 128-bit long IPv6 addresses is now replaced by an ordered 158 list of 32-bit long label entries (i.e., label stack), the 159 encapsulation overhead and forwarding performance issues 160 associated with SRv6 are eliminated. 162 o A new IPv4 source routing mechanism which has overcome the 163 security vulnerability issues associated with the traditional IPv4 164 source routing mechanism. 166 o Traffic Engineering scenarios where only a few routers (e.g., the 167 entry and exit nodes of each plane in the dual-plane network case 168 or the egress node in the Egress Peer Engineering (EPE) case) are 169 specified as segments of explicit paths. In this way, only a few 170 routers are required to support the SR-MPLS capability while all 171 the other routers just need to support IP forwarding capability, 172 which would significantly reduce the deployment cost of the SR- 173 MPLS technology. 175 o MPLS-based Service Function Chaining (SFC) 176 [I-D.xu-mpls-service-chaining]. Based on the unified source 177 routing mechanism as described in this document, only SFC-related 178 nodes including Service Function Forwarders (SFF), Service 179 Functions (SF) and classifiers are required to recognize the SFC 180 encapsulation header in the MPLS label stack form, while the 181 intermediate routers just need to support vanilla IP forwarding 182 (either IPv4 or IPv6). In other words, it undoubtedly complies 183 with the transport-independence requirement for the SFC 184 encapsulation header as listed in the SFC architecture document 185 [RFC7665]. 187 4. Packet Forwarding Procedures 189 The primary objective of this document is to describe how SR-MPLS 190 capable routers and IP-only routers can seamlessly co-exist and 191 interoperate. This section describes the forwarding information base 192 (FIB) entry and the forwarding behavior that allow the deployment of 193 SR-MPLS when some routers are IPv4 only or IPv6 only. 195 4.1. Forwarding Entry Construction 197 This sub-section describes the how to construct the forwarding 198 information base (FIB) entry on an SR-MPLS-capable router when some 199 or all of the next-hops along the shortest path towards a prefix-SID 200 are IPv4-only or IPv6-only routers. Consider the router "A" 201 receiving a labeled packet whose top label L(E) corresponds to the 202 prefix-SID is "SID(E)" of prefix "P(E)" advertised by the router "E". 203 Suppose the ith next-hop router "NHi" along the shortest path from 204 the router "A" towards the prefix-SID "SID(E)" is not SR-MPLS 205 capable. That is both routers "A" and "E" are SR-MPLS capable but 206 the next hop "NHi" along the shortest path from "A" to "E". The 207 following aplies: 209 o It is assumed that the router "E" advertises the SR-Capabilities 210 sub-TLV as described in and 211 [I-D.ietf-ospf-segment-routing-extensions], which includes the 212 SRGB because router "E" is SR-MPLS capabile. 214 o The owning router "E" MUST advertise the encapsulation endpoint 215 and the tunnel type using [I-D.ietf-isis-encapsulation-cap] and/or 216 [I-D.ietf-ospf-encapsulation-cap] . 218 o If "A" and "E" are in different areas/levels, then 220 o 222 * The OSPF Encapsulation Capability TLV 223 [I-D.ietf-ospf-encapsulation-cap] and/or the ISIS Tunnel 224 Encapsulation sub-TLV [I-D.ietf-isis-encapsulation-cap] are 225 flooded domain-wide. 227 * The OSPF SID/label range TLV 228 [I-D.ietf-ospf-segment-routing-extensions] and the ISIS SR- 229 Capabilities Sub-TLV [I-D.ietf-isis-segment-routing-extensions] 230 are advertised domain-wide. This way router "A" knows the 231 characteristics of the owning router "E". 233 * When the owning router "E" is running ISIS and advertises the 234 prefix "P(E) ", the router "E" uses the extended reachability 235 TLV (TLVs 135, 235, 236, 237) and associates the IPv4/IPv6 and/ 236 or IPv4/IPv6 source router ID sub-TLV(s) [RFC7794]. 238 * When the owning router "E" is running OSPF and advertises the 239 prefix "P(E)", the router "E" uses the OSPFv2 Extended Prefix 240 Opaque LSA [RFC7684] and sets the flooding scope to AS-wide. 242 * When the owning router "E" is running ISIS and advertises the 243 ISIS capabilities TLV (TLV 242) [RFC7981], it must set the 244 "router-ID" field to a valid value or include IPV6 TE router- 245 ID sub-TLV (TLV 12), or do both. The "S" bit (flooding scope) 246 of the ISIS capabilities TLV (TLV 242) MUST be set to "1" . 248 o Router "A" programs the FIB entry corresponding to the "SID(E)" as 249 follows: 251 o 253 * If NP (OSPF) or P (ISIS) flag is clear, 255 * 257 + pop the outer label. 259 * If NP (OSPF) or P (ISIS) is set, 261 * 263 + the outer label is SID(E) plus the lower bound of the SRGB 264 of "E". 266 * Encapsulate the packet according to the encapsulation 267 advertised in [I-D.ietf-isis-encapsulation-cap] or 268 [I-D.ietf-ospf-encapsulation-cap]. 270 * Send the packet towards the next hop "NHi". 272 4.2. Packet Forwarding Procedures 273 +-----+ +-----+ +-----+ +-----+ +-----+ 274 | A +-------+ B +-------+ C +--------+ D +--------+ H | 275 +-----+ +--+--+ +--+--+ +--+--+ +-----+ 276 | | | 277 | | | 278 +--+--+ +--+--+ +--+--+ 279 | E +-------+ F +--------+ G | 280 +-----+ +-----+ +-----+ 282 +--------+ 283 |IP(A->E)| 284 +--------+ +--------+ 285 | L(G) | |IP(E->G)| 286 +--------+ +--------+ +--------+ 287 | L(H) | | L(H) | |IP(G->H)| 288 +--------+ +--------+ +--------+ 289 | Packet | ---> | Packet | ---> | Packet | 290 +--------+ +--------+ +--------+ 291 Figure 1 293 As shown in Figure 1, Assume Router A, E, G and H are SR-MPLS-capable 294 routers while the remaining are only capable of forwarding IP 295 packets. Router A, E, G and H advertise their Segment Routing 296 related information via IS-IS or OSPF. Now assume router A wants to 297 send a given IP or MPLS packet via an explicit path of {E->G->H}, 298 router A would impose an MPLS label stack corresponding to that 299 explicit path on the received IP packet. Since there is no Label 300 Switching Path (LSP) towards router E, router A would replace the top 301 label indicating router E with an IP-based tunnel for MPLS (e.g., 302 MPLS-over-UDP [RFC7510]) towards router E and then send it out. In 303 other words, router A would pop the top label and then encapsulate 304 the MPLS packet with an IP-based tunnel towards router E. When the 305 IP-encapsulated MPLS packet arrives at router E, router E would strip 306 the IP-based tunnel header and then process the decapsulated MPLS 307 packet accordingly. Since there is no LSP towards router G which is 308 indicated by the current top label of the decapsulated MPLS packet, 309 router E would replace the current top label with an IP-based tunnel 310 towards router G and send it out. When the packet arrives at router 311 G, router G would strip the IP-based tunnel header and then process 312 the decapsulated MPLS packet. Since there is no LSP towards router 313 H, router G would replace the current top label with an IP-based 314 tunnel towards router H. Now the packet encapsulated with the IP- 315 based tunnel towards router H is exactly the original packet that 316 router A had intended to send towards router H. If the packet is an 317 MPLS packet, router G could use any IP-based tunnel for MPLS (e.g., 318 MPLS-over-UDP [RFC7510]). If the packet is an IP packet, router G 319 could use any IP tunnel for IP (e.g., IP-in-UDP 320 [I-D.xu-intarea-ip-in-udp]). That original IP or MPLS packet would 321 be forwarded towards router H via an IP-based tunnel. When the 322 encapsulated packet arrives at router H, router H would decapsulate 323 it into the original packet and then process it accordingly. 325 Note that in the above description, it's assumed that the label 326 associated with each prefix-SID advertised by the owner of the 327 prefix-SID is a Penultimate Hop Popping (PHP) label (e.g., the NP- 328 flag [I-D.ietf-ospf-segment-routing-extensions] associated with the 329 corresponding prefix SID is not set). 331 Figure 2 demostrates the packet walk in the case where the label 332 associated with each prefix-SID advertised by the owner of the 333 prefix-SID is not a Penultimate Hop Popping (PHP) label (e.g., the 334 NP-flag [I-D.ietf-ospf-segment-routing-extensions] associated with 335 the corresponding prefix SID is set). 337 +-----+ +-----+ +-----+ +-----+ +-----+ 338 | A +-------+ B +-------+ C +--------+ D +--------+ H | 339 +-----+ +--+--+ +--+--+ +--+--+ +-----+ 340 | | | 341 | | | 342 +--+--+ +--+--+ +--+--+ 343 | E +-------+ F +--------+ G | 344 +-----+ +-----+ +-----+ 346 +--------+ 347 |IP(A->E)| 348 +--------+ +--------+ 349 | L(E) | |IP(E->G)| 350 +--------+ +--------+ +--------+ 351 | L(G) | | L(G) | |IP(G->H)| 352 +--------+ +--------+ +--------+ 353 | L(H) | | L(H) | | L(H) | 354 +--------+ +--------+ +--------+ 355 | Packet | ---> | Packet | ---> | Packet | 356 +--------+ +--------+ +--------+ 357 Figure 2 359 Although the above description is based on the use of prefix-SIDs, 360 the unified source routing instruction approach is actually 361 applicable to the use of adj-SIDs as well. For instance, when the 362 top label of a received MPLS packet indicates an given adj-SID and 363 the corresponding adjacent node to that adj-SID is not MPLS-capable, 364 the top label would be replaced by an IP-based tunnel towards that 365 adjacent node and then forwarded over the correponding link indicated 366 by that adj-SID. 368 As for which tunnel encapsulation type should be used, it could be 369 manually specified on tunnel ingress routers or be learnt from the 370 tunnel egress routers' advertisements of its tunnel encapsulation 371 capability (See Section 5). 373 To avoid re-performing hash on the whole packet when re-encapsulating 374 the packet with an IP-based tunnel header, it's RECOMMENDED that the 375 entropy value contained in the packet (e.g., the UDP source port 376 value) is kept when stripping the IP-based tunnel header (e.g., the 377 UDP tunnel header). As such, the entropy value could be directly 378 copied to the entropy field (e.g., the source port of the UDP tunnel 379 header) when re-encapsulating the packet with an IP-based tunnel 380 header (e.g., UDP tunnel header). As such, the load-balancing 381 dilemma encountered by SR-MPLS due to the maximum Readable Label- 382 stack Depth (RLD) hardware limitation 383 [I-D.ietf-mpls-spring-entropy-label] and the Maximum SID Depth (MSD) 384 hardware limitation [I-D.ietf-ospf-segment-routing-msd] is gone. 385 That's the reason why this unified source routing mechanism is even 386 useful in a fully upgraded SR-MPLS network environment. 388 5. Signalling Considerations 390 The existing protocols for SR-MPLS (e.g., 391 [I-D.ietf-isis-segment-routing-extensions] and 392 [I-D.ietf-ospf-segment-routing-extensions]) is reused without any 393 change. In order to dynamically establish IP-based tunnels between 394 SR-MPLS-enabled routers, extensions to IS-IS or OSPF are specified in 395 [I-D.ietf-isis-encapsulation-cap] and 396 [I-D.ietf-ospf-encapsulation-cap] respectively to discover the tunnel 397 encapsulation capability of tunnel egress routers. 399 6. Acknowledgements 401 Thanks Joel Halpern, Bruno Decraene, Loa Andersson and Stewart Bryant 402 for their insightful comments on this document. 404 7. IANA Considerations 406 No IANA action is required. 408 8. Security Considerations 410 TBD. 412 9. References 414 9.1. Normative References 416 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 417 Requirement Levels", BCP 14, RFC 2119, 418 DOI 10.17487/RFC2119, March 1997, 419 . 421 9.2. Informative References 423 [I-D.ietf-6man-segment-routing-header] 424 Previdi, S., Filsfils, C., Raza, K., Leddy, J., Field, B., 425 daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d., 426 Matsushima, S., Leung, I., Linkova, J., Aries, E., Kosugi, 427 T., Vyncke, E., Lebrun, D., Steinberg, D., and R. Raszuk, 428 "IPv6 Segment Routing Header (SRH)", draft-ietf-6man- 429 segment-routing-header-07 (work in progress), July 2017. 431 [I-D.ietf-isis-encapsulation-cap] 432 Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras, 433 L., and L. Jalil, "Advertising Tunnelling Capability in 434 IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in 435 progress), April 2017. 437 [I-D.ietf-isis-segment-routing-extensions] 438 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 439 Litkowski, S., Decraene, B., and j. jefftant@gmail.com, 440 "IS-IS Extensions for Segment Routing", draft-ietf-isis- 441 segment-routing-extensions-13 (work in progress), June 442 2017. 444 [I-D.ietf-mpls-spring-entropy-label] 445 Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., 446 Shakir, R., and j. jefftant@gmail.com, "Entropy label for 447 SPRING tunnels", draft-ietf-mpls-spring-entropy-label-06 448 (work in progress), May 2017. 450 [I-D.ietf-ospf-encapsulation-cap] 451 Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L. 452 Jalil, "Advertising Tunneling Capability in OSPF", draft- 453 ietf-ospf-encapsulation-cap-06 (work in progress), July 454 2017. 456 [I-D.ietf-ospf-segment-routing-extensions] 457 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 458 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 459 Extensions for Segment Routing", draft-ietf-ospf-segment- 460 routing-extensions-18 (work in progress), July 2017. 462 [I-D.ietf-ospf-segment-routing-msd] 463 Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, 464 "Signaling MSD (Maximum SID Depth) using OSPF", draft- 465 ietf-ospf-segment-routing-msd-05 (work in progress), June 466 2017. 468 [I-D.ietf-spring-segment-routing-ldp-interop] 469 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and 470 S. Litkowski, "Segment Routing interworking with LDP", 471 draft-ietf-spring-segment-routing-ldp-interop-08 (work in 472 progress), June 2017. 474 [I-D.ietf-spring-segment-routing-mpls] 475 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 476 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 477 data plane", draft-ietf-spring-segment-routing-mpls-10 478 (work in progress), June 2017. 480 [I-D.xu-intarea-ip-in-udp] 481 Xu, X., Lee, Y., and F. Yongbing, "Encapsulating IP in 482 UDP", draft-xu-intarea-ip-in-udp-04 (work in progress), 483 December 2016. 485 [I-D.xu-mpls-service-chaining] 486 Xu, X., Bryant, S., Assarpour, H., Shah, H., Contreras, 487 L., daniel.bernier@bell.ca, d., jefftant@gmail.com, j., 488 Ma, S., and M. Vigoureux, "Service Chaining using Unified 489 Source Routing Instructions", draft-xu-mpls-service- 490 chaining-03 (work in progress), June 2017. 492 [I-D.xu-mpls-spring-islands-connection-over-ip] 493 Xu, X., Raszuk, R., Chunduri, U., Contreras, L., and L. 494 Jalil, "Connecting MPLS-SPRING Islands over IP Networks", 495 draft-xu-mpls-spring-islands-connection-over-ip-00 (work 496 in progress), October 2016. 498 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 499 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 500 DOI 10.17487/RFC2784, March 2000, 501 . 503 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 504 Label Switching Architecture", RFC 3031, 505 DOI 10.17487/RFC3031, January 2001, 506 . 508 [RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and 509 J. Young, "Encapsulation of MPLS over Layer 2 Tunneling 510 Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March 511 2007, . 513 [RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black, 514 "Encapsulating MPLS in UDP", RFC 7510, 515 DOI 10.17487/RFC7510, April 2015, 516 . 518 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 519 Chaining (SFC) Architecture", RFC 7665, 520 DOI 10.17487/RFC7665, October 2015, 521 . 523 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 524 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 525 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 526 2015, . 528 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 529 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 530 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 531 March 2016, . 533 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 534 for Advertising Router Information", RFC 7981, 535 DOI 10.17487/RFC7981, October 2016, 536 . 538 Authors' Addresses 540 Xiaohu Xu 541 Huawei 543 Email: xuxiaohu@huawei.com 545 Clarence Filsfils 546 Cisco 548 Email: cfilsfil@cisco.com 549 Ahmed Bashandy 550 Cisco 552 Email: bashandy@cisco.com 554 Robert Raszuk 555 Bloomberg LP 557 Email: robert@raszuk.net 559 Uma Chunduri 560 Huawei 562 Email: uma.chunduri@gmail.com 564 Luis M. Contreras 565 Telefonica I+D 567 Email: luismiguel.contrerasmurillo@telefonica.com 569 Luay Jalil 570 Verizon 572 Email: luay.jalil@verizon.com 574 Hamid Assarpour 575 Broadcom 577 Email: hamid.assarpour@broadcom.com 579 Gunter Van De Velde 580 Nokia 581 Antwerp 582 Belgium 584 Email: gunter.van_de_velde@nokia.com 586 Jeff Tantsura 587 Individual 589 Email: jefftant.ietf@gmail.com 590 Shaowen Ma 591 Juniper 593 Email: mashao@juniper.net 595 Tal Mizrahi 596 Marvell 598 Email: talmi@marvell.com