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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-mirsky-6man-unified-id-sr-03 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network C. Weiqiang 3 Internet-Draft China Mobile 4 Intended status: Informational P. Shaofu 5 Expires: May 6, 2020 L. Aihua 6 ZTE Corporation 7 G. Mirsky 8 ZTE Corp. 9 W. Xiaolan 10 New H3C Technologies Co. Ltd 11 C. Wei 12 Centec 13 S. Zadok 14 Broadcom 15 November 3, 2019 17 Unified Identifier in IPv6 Segment Routing Networks 18 draft-wmsaxw-6man-usid-id-use-00 20 Abstract 22 Segment Routing architecture leverages the paradigm of source 23 routing. It can be realized in a network data plane by prepending 24 the packet with a list of instructions, a.k.a. segments. A segment 25 can be encoded as a Multi-Protocol Label Switching (MPLS) label, IPv4 26 address, or IPv6 address. Segment Routing can be applied in the MPLS 27 data plane by encoding segments in an MPLS label stack. It also can 28 be applied to the IPv6 data plane by encoding a list of segment 29 identifiers in IPv6 Segment Routing Extension Header (SRH). In this 30 document is described the use of unified segment identifiers in use 31 cases where interworking between SR-MPLS and SRv6 is required. 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 May 6, 2020. 50 Copyright Notice 52 Copyright (c) 2019 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 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 1.1. Conventions used in this document . . . . . . . . . . . . 3 69 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 70 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 71 2. Requirements for Using SRv6 in Backhaul . . . . . . . . . . . 4 72 3. Using SRv6 U-SID in Backhaul . . . . . . . . . . . . . . . . 4 73 3.1. Smoothly Upgrading to SRv6 from SR-MPLS . . . . . . . . . 4 74 3.2. Interworking Between SRv6 and SR-MPLS . . . . . . . . . . 5 75 3.3. Compressing SRv6 Header Effectively . . . . . . . . . . . 6 76 3.4. Support a Super-large-scale Networking and Flexibility in 77 Assigning Addresses . . . . . . . . . . . . . . . . . . . 6 78 4. Operations with Unified Segment Identifier . . . . . . . . . 6 79 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 80 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 81 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 82 8. Normative References . . . . . . . . . . . . . . . . . . . . 7 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 85 1. Introduction 87 Many functions related to Operation, Administration and Maintenance 88 (OAM) require identification of the SR tunnel ingress and the path, 89 constructed by segments, between the ingress and the egress SR nodes. 90 Combination of IPv6 encapsulation [RFC8200] and the Source Routing 91 Extension Header (SRH) [I-D.ietf-6man-segment-routing-header], 92 referred to as SRv6, comply with these requirements while it is 93 challenging when applying SR in MPLS networks 94 [I-D.ietf-spring-segment-routing-mpls], also referred to as SR-MPLS. 96 On the other hand, the size of the IPv6 segment identifier (SID) 97 presents a scaling challenge to use topological instructions that 98 define a strict explicitly routed path in combination with service- 99 based instructions. At the same time, that is where the SR-MPLS 100 approach provides better results due to smaller SID length. 102 SR-MPLS currently, more often than SRv6, is used in metro networks. 103 With the gradual deployment of SRv6 in the core networks, it becomes 104 necessary to support interworking between SR-MPLS and SRv6. 105 Operationally it would be more efficient and straightforward if SRv6 106 can use the same size SIDs as in SR-MPLS. The SRH can be extended to 107 use the same as in SR-MPLS SID length to support the unified segment 108 identifier (U-SID) [I-D.mirsky-6man-unified-id-sr]. As a result of 109 using this approach, U-SIDs can be used end-to-end across a tunnel 110 that spans over SR-MPLS and SRv6 domains. 112 In this document is described the use of unified segment identifiers, 113 encoded as MPLS label and/or 32 bits-long address, in use cases when 114 interworking between SR-MPLS and SRv6 networks is required. 116 1.1. Conventions used in this document 118 1.1.1. Terminology 120 SR: Segment Routing 122 SRH: Segment Routing Extension Header 124 MPLS: Multiprotocol Label Switching 126 SR-MPLS: Segment Routing using MPLS data plane 128 SID: Segment Identifier 130 IGP: Interior Gateway Protocol 132 OAM: Operation, Administration and Maintenance 134 SRv6: Segment Routing in IPv6 136 U-SID: Unified Segment Identifier 138 1.1.2. Requirements Language 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 142 "OPTIONAL" in this document are to be interpreted as described in BCP 143 14 [RFC2119] [RFC8174] when, and only when, they appear in all 144 capitals, as shown here. 146 2. Requirements for Using SRv6 in Backhaul 148 2G/3G/4G backhaul networks widely deploy MPLS to connect wireless 149 services. Many operators are already deploying 5G networks. To 150 optimize the operation of the network, many operators intent to adopt 151 the segment routing. Currently, given maturity of SR-MPLS, it has 152 been deployed on a large scale. Meanwhile the requirements of 5G 153 super-large-scale number of connections accelerate the deployment of 154 IPv6 networks. Thus, logically, operators consider SRv6 solution to 155 fulfill the 5G backhaul requirement. But the backhaul network could 156 not deploy SRv6 in one day, especially if it has already been using 157 MPLS and SR-MPLS. It might be reasonable to upgrade from MPLS to SR- 158 MPLS and then to SRv6. There are several essential operational 159 requirements for the deployment of SRv6 in 5G backhaul network: 161 1. Ensure the ability to transform the existing SR-MPLS backhaul 162 network into an SRv6 5G backhaul network incrementally. 164 2. Support interworking between SRv6 and SR-MPLS domains in the 165 network. 167 3. Support SRv6 header compressing. 169 4. Support super-large-scale networking and address planning 171 3. Using SRv6 U-SID in Backhaul 173 U-SID provides a solution that complies to the 5G backhaul 174 requirements. 176 3.1. Smoothly Upgrading to SRv6 from SR-MPLS 178 SR-MPLS uses a segment encoded as a label in an MPLS label stack to 179 simplify the backhaul network. It leverages the advantages of both 180 source-routing and MPLS. Existing backhaul networks that use MPLS 181 can be first updated to use SR-MPLS. SRv6 uses the segment encoded 182 as an identifier in IPv6 SRH. The SR-MPLS and SRv6 protocol stacks 183 are illustrated in Figure 1. 185 +-----------------+ +-----------------+ 186 | Ethernet | | Ethernet | 187 +-----------------+ +-----------------+ 188 | | | | 189 | SR-MPLS | | SRv6 | 190 | | | | 191 +-----------------+ +-----------------+ 192 | Payload | | Payload | 193 +-----------------+ +-----------------+ 195 Figure 1: SR-MPLS and SRv6 Protocol Stacks 197 A segment identifier in SR-MPLS occupies 32 bits, and in SRv6 - 128 198 bits. As the backhaul infrastructure being upgraded to IPv6, 199 operators are looking for technology that would reuse SR-MPLS by re- 200 mapping the label table. But the namespace in SR-MPLS is limited and 201 couldn't build the new segment identifiers to the global network. 202 Using U-SID with SRv6 allows the reuse of the 32-bit SIDs, which are 203 the same as in SR-MPLS. Thus, U-SID with SRv6 can be reused in 204 backhaul to minimize the impact on existing SR-MPLS services and 205 support smooth rollout of SRv6. The only additional task is to 206 assign U-SIDs to the SRv6 domain. The controller could create an 207 end-to-end SR tunnel using 32bit-long segments identifiers to stitch 208 the SR-MPLS and SRv6 domains. 210 3.2. Interworking Between SRv6 and SR-MPLS 212 For a 5G backhaul network, the operators want to try their best to 213 reuse the existing transport network. Consequently, they must 214 consider the SRv6 interworking with SR-MPLS while deploying SRv6. 215 Using U-SID offers a practical approach to native interworking 216 between SR-MPLS and SRv6 domains because an operator in both domains 217 can use segment identifiers of the same format, U-SID. 219 Using U-SID interworking between SRv6 and SR-MPLS brings some 220 significant advantages: 222 1. An end-to-end LSP can be created across the access/aggregation 223 network with SR-MPLS and core network with SRv6. 225 2. An end-to-end OAM and protection mechanism can be supported 226 reusing SR-MPLS 228 The SR-MPLS and SRv6 interworking is illustrated in Figure 2. An 229 end-to-end SR tunnel from A to F crosses the SR-MPLS and SRv6 230 domains. Using U-SID end-to-end LSP can reuse SR-MPLS forwarding, 231 and support end-to-end OAM and protection. 233 +-----+ +-----+ +-----+ +-----+ 234 LSP-->| A +-------+ B +-------+ E +-------+ F |--> 235 +-----+ +--+--+ +--+--+ +--+--+ 236 | SR-MPLS | | SRv6 | 237 | Access/Agg | | Core | 238 +-----+ +--+--+ +--+--+ +--+--+ 239 | C |-------| D +-------+ G +-------+ H | 240 +-----+ +-----+ +-----+ +-----+ 242 Figure 2: SR-MPLS and SRv6 Interworking 244 3.3. Compressing SRv6 Header Effectively 246 While deploying SRv6 in the backhaul network, the SRv6 header 247 overhead must be considered. Typically there a maximum of ten hops 248 for an end-to-end transport path. The header overhead is 1280 bits 249 (10*128 bit SRH) using SRH with the 128-bit SID without OAM and 250 protection. It will be reduced to 320 bits (3*128 bit SRH) using 251 U-SID SRv6 with 32-bit SID. So the compressing rate is more than 70% 252 (from at least 10*128 bit SRH to 3*128 bit SRH). 254 3.4. Support a Super-large-scale Networking and Flexibility in 255 Assigning Addresses 257 The scale of the backhaul network is up to 10K nodes. A network of 258 such size needs to support to address up to 10K nodes. U-SID SRv6 259 can support the 2^20 labels as the same with MPLS, and it's enough 260 for a super-large-scale backhaul networking. Since IPv6 solves the 261 problem of a shortage of IPv4 addresses, it should not be using a 262 shorter IPv6 address, i.e., a shorter prefix plus a shorter offset. 263 That will violate the original IPv6 design. On the other hand, using 264 SRv6 should not require the assignment of special addresses for the 265 operator's network. U-SID can preserve the full 128-bit addresses by 266 re-mapping the table. To use U-SID in SRv6 doesn't require the IPv6 267 address and SRv6 segments planning, such as the address prefix 268 allocation. The operator would reuse the current address assignment 269 and planning, thus minimizing the impact on the backhaul network. 271 4. Operations with Unified Segment Identifier 273 When the SRH is used to include 20-bits or 32-bits U-SIDs the ingress 274 and transit nodes of an SR tunnel act as described in Section 5.1 and 275 Section 5.2 of [I-D.ietf-6man-segment-routing-header] respectively. 277 5. IANA Considerations 279 This document has no requests to IANA. This section can be removed 280 before the publication. 282 6. Security Considerations 284 This specification inherits all security considerations of [RFC8402] 285 and [I-D.ietf-6man-segment-routing-header]. 287 7. Acknowledgements 289 TBD 291 8. Normative References 293 [I-D.ietf-6man-segment-routing-header] 294 Filsfils, C., Dukes, D., Previdi, S., Leddy, J., 295 Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment 296 Routing Header (SRH)", draft-ietf-6man-segment-routing- 297 header-26 (work in progress), October 2019. 299 [I-D.ietf-spring-segment-routing-mpls] 300 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., 301 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 302 data plane", draft-ietf-spring-segment-routing-mpls-22 303 (work in progress), May 2019. 305 [I-D.mirsky-6man-unified-id-sr] 306 Cheng, W., Mirsky, G., Peng, S., Aihua, L., Wan, X., and 307 C. Wei, "Unified Identifier in IPv6 Segment Routing 308 Networks", draft-mirsky-6man-unified-id-sr-03 (work in 309 progress), July 2019. 311 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 312 Requirement Levels", BCP 14, RFC 2119, 313 DOI 10.17487/RFC2119, March 1997, 314 . 316 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 317 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 318 May 2017, . 320 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 321 (IPv6) Specification", STD 86, RFC 8200, 322 DOI 10.17487/RFC8200, July 2017, 323 . 325 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 326 Decraene, B., Litkowski, S., and R. Shakir, "Segment 327 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 328 July 2018, . 330 Authors' Addresses 332 Cheng Weiqiang 333 China Mobile 334 Beijing 335 China 337 Email: chengweiqiang@chinamobile.com 339 Peng Shaofu 340 ZTE Corporation 341 No.50 Software Avenue, Yuhuatai District 342 Nanjing 343 China 345 Email: peng.shaofu@zte.com.cn 347 Liu Aihua 348 ZTE Corporation 349 Zhongxing Industrial Park, Nanshan District 350 Shenzhen 351 China 353 Email: liu.aihua@zte.com.cn 355 Greg Mirsky 356 ZTE Corp. 358 Email: gregimirsky@gmail.com 360 Wan Xiaolan 361 New H3C Technologies Co. Ltd 362 No.8, Yongjia Road, Haidian District 363 Beijing 364 China 366 Email: wxlan@h3c.com 367 Cheng Wei 368 Centec 369 Building B, No.5 Xing Han Street, Suzhou Industrial Park 370 Suzhou 371 China 373 Email: Chengw@centecnetworks.com 375 Shay 376 Broadcom 377 Israel 379 Email: shay.zadok@broadcom.com