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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SPRING Working Group C. Li 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track W. Cheng 5 Expires: February 14, 2020 China Mobile 6 M. Chen 7 D. Dhody 8 Z. Li 9 J. Dong 10 Huawei Technologies 11 R. Gandhi 12 Cisco Systems, Inc. 13 August 13, 2019 15 Path Segment for SRv6 (Segment Routing in IPv6) 16 draft-li-spring-srv6-path-segment-03 18 Abstract 20 Segment Routing (SR) allows for a flexible definition of end-to-end 21 paths by encoding paths as sequences of sub-paths, called "segments". 22 Segment routing architecture can be implemented over an MPLS data 23 plane as well as an IPv6 data plane. 25 Further, Path Segment has been defined in order to identify an SR 26 path in SR-MPLS networks, and used for various use-cases such as end- 27 to-end SR Path Protection and Performance Measurement (PM) of an SR 28 path. Similar to SR-MPLS, this document defines the Path Segment in 29 SRv6 networks in order to identify an SRv6 path. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on February 14, 2020. 48 Copyright Notice 50 Copyright (c) 2019 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 67 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. Use Cases of SRv6 Path Segment . . . . . . . . . . . . . . . 4 69 3. SRv6 Path Segment . . . . . . . . . . . . . . . . . . . . . . 5 70 4. SRv6 Path Segment Allocation . . . . . . . . . . . . . . . . 6 71 5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 74 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 77 9.2. Informative References . . . . . . . . . . . . . . . . . 7 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 80 1. Introduction 82 Segment routing (SR) [RFC8402] is a source routing paradigm that 83 explicitly indicates the forwarding path for packets at the ingress 84 node by inserting an ordered list of instructions, called segments. 86 When segment routing is deployed on MPLS dataplane, called SR-MPLS 87 [I-D.ietf-spring-segment-routing-mpls], a segment is an MPLS label. 88 When segment routing is deployed on IPv6 dataplane, called SRv6 89 [I-D.ietf-6man-segment-routing-header], a segment is a 128 bit value, 90 and it can be an IPv6 address of a local interface but it does not 91 have to. For supporting SR, an extended header called Segment 92 Routing Header (SRH), which contains a list of SIDs and several 93 needed information such as Segments Left, has been defined in 94 [I-D.ietf-6man-segment-routing-header]. 96 In an SR-MPLS network, when a packet is transmitted along an SR path, 97 the labels in the MPLS label stack will be swapped or popped, so no 98 label or only the last label may be left in the MPLS label stack when 99 the packet reaches the egress node. Thus, the egress node can not 100 determine from which ingress node or SR path the packet came in. For 101 identifying an SR-MPLS path, Path Segment is defined in 102 [I-D.ietf-spring-mpls-path-segment]. 104 Likewise, a path needs to be identified in an SRv6 network for 105 several use cases such as binding bidirectional paths 106 [I-D.li-pce-sr-bidir-path] and end-to-end performance measurement 107 [I-D.gandhi-spring-udp-pm]. An SRv6 path can be identified by the 108 content of segment list (i.e., the several SRv6 segments that are in 109 the segment list). However, the segment list may not be a good key 110 to identify an SRv6 path, since the the length of segment list is too 111 long and flexible according to the number of SIDs. For instance, if 112 packet A uses the SRH with 3 SIDs while Packet B uses the SRH with 10 113 SIDs, the key to identify these two paths which the Packet A and B 114 belong to will be a 384-bits value and a 1280-bits value. 116 This document defines a new SRv6 segment called "SRv6 Path Segment", 117 which is a 128-bits value, to identify an SRv6 path. Using the Path 118 Segment as an SRv6 SID will improve performance and operations in 119 both SR-MPLS and SRv6. Also, when the SRv6 Path Segment is used in 120 reduced SRH [I-D.ietf-6man-segment-routing-header], the entire path 121 information is maintained in SRH and the performance will be better 122 than using SID list as the path identifier, while the overhead equals 123 to the normal SRH. The Path Segment is inserted as the last segment 124 in the segment list and will not affect the order of the original SID 125 list and has the solely scope to give a unique identifier to the 126 segment list. 128 1.1. Requirements Language 130 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 131 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 132 "OPTIONAL" in this document are to be interpreted as described in BCP 133 14 [RFC2119] [RFC8174] when, and only when, they appear in all 134 capitals, as shown here. 136 1.2. Terminology 138 MPLS: Multiprotocol Label Switching. 140 PM: Performance Measurement. 142 SID: Segment ID. 144 SR: Segment Routing. 146 SR-MPLS: Segment Routing with MPLS data plane. 148 SRH: Segment Routing Header. 150 PSID: Path Segment Identifier. 152 PSP: Penultimate Segment Popping. 154 Further, this document makes use of the terms defined in [RFC8402] 155 and [I-D.ietf-spring-srv6-network-programming]. 157 2. Use Cases of SRv6 Path Segment 159 Similar to SR-MPLS Path Segment [I-D.ietf-spring-mpls-path-segment], 160 SRv6 Path Segment also can be used for identifying an SRv6 Path in 161 some use cases: 163 o Performance Measurement: For Passive measurement [RFC7799], path 164 identification at the measuring points is the pre-requisite 165 [I-D.ietf-spring-mpls-path-segment]. SRv6 Path segment can be 166 used by the measuring points (e.g., the ingress/egress nodes of an 167 SRv6 path) or a centralized controller to correlate the packets 168 counts/timestamps, then packet loss/delay can be calculated. 170 o Bi-directioinal SRv6 Path Association: In some scenarios, such as 171 mobile backhaul transport network, there are requirements to 172 support bidirectional path. Similar to SR-MPLS 173 [I-D.ietf-spring-mpls-path-segment], to support bidirectional SRv6 174 path, a straightforward way is to bind two unidirectional SRv6 175 paths to a single bidirectional path. SRv6 Path segments can be 176 used to correlate the two unidirectional SRv6 paths at both ends 177 of the paths. [I-D.li-pce-sr-bidir-path] defines how to use PCEP 178 and Path segment to initiate a bidirectional SR path. 180 o End-to-end Path Protection: For end-to-end 1+1 path protection 181 (i.e., Live-Live case), the egress node of an SRv6 path needs to 182 know the set of paths that constitute the primary and the 183 secondary(s), in order to select the primary packet for onward 184 transmission, and to discard the packets from the secondary(s), so 185 each SRv6 path needs a unique path identifier at the egress node, 186 which can be an SRv6 Path Segment. 188 3. SRv6 Path Segment 190 As defined in [I-D.ietf-spring-srv6-network-programming], an SRv6 191 segment is a 128-bit value, which can be represented as LOC:FUNCT. 193 In order to identify an SRv6 path, this document defines a new 194 segment called SRv6 Path Segment. A Path Segment is solely used in 195 order to identify an SRv6 path. 197 The Path Segment MUST appear only once in a SID list, and it MUST 198 appear at the last entry. 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 | | 202 | Segment List[0] (128 bits IPv6 address) | 203 | | 204 | | 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 | | 207 | | 208 | ... | 209 | | 210 | | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | | 213 | Segment List[n-1] (128 bits IPv6 address) | 214 | | 215 | | 216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 217 | | 218 | Path Segment(Segment List[n], 128 bits value) | 219 | | 220 | | 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 Figure 1. SRv6 Path Segment in SID List 225 The detailed encoding of SRv6 Path Segment is out of scope of this 226 document, and it is defined in [I-D.li-6man-srv6-path-segment-encap]. 228 Depending on the use case, a Path Segment identifies: 230 o an SRv6 path within an SRv6 domain 232 o an SRv6 Policy 234 o a Candidate-paths or a SID-List in a SRv6 Policy 235 [I-D.ietf-spring-segment-routing-policy] 237 Note that, based on the use-case, the different SID-Lists of SR 238 Policies may use the same SRv6 Path Segment. 240 4. SRv6 Path Segment Allocation 242 A Path Segment is a local segment allocated by an egress node. A 243 Path Segment can be allocated through several ways, such as CLI, BGP 244 [I-D.li-idr-sr-policy-path-segment-distribution], PCEP 245 [I-D.li-pce-sr-path-segment] or other ways. The mechanisms through 246 which a Path Segment is allocated is out of scope of this document. 248 When the Path Segment is allocated by the egress, it MUST be 249 distributed to the ingress node. In this case, only the egress will 250 process the Path Segment, and other nodes specified by SIDs in the 251 SID list do not know how to process the Path Segment. 253 Depending on the use case, a Path Segment may be distributed to the 254 SRv6 nodes along the SRv6 path. In this case, the SRv6 nodes that 255 learned Path Segment may process the Path Segment depending on the 256 use case. 258 5. Operations 260 An egress node or other SRv6 nodes along the SRv6 path supporting the 261 Path Segment processing will inspect the last entry of the segment 262 list (giving the the node will inspect the last entry in the SID list 263 and obtain the Path Segment. The processing of the Path Segment is 264 described in [I-D.li-6man-srv6-path-segment-encap]. 266 6. IANA Considerations 268 This document does not require any IANA actions. 270 7. Security Considerations 272 This document does not introduce additional security requirements and 273 mechanisms other than the ones described in [RFC8402]. 275 8. Acknowledgements 277 The authors would like to thank Stefano Previdi and Zafar Ali for 278 their valuable comments and suggestions. 280 9. References 281 9.1. Normative References 283 [I-D.ietf-6man-segment-routing-header] 284 Filsfils, C., Dukes, D., Previdi, S., Leddy, J., 285 Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment 286 Routing Header (SRH)", draft-ietf-6man-segment-routing- 287 header-22 (work in progress), August 2019. 289 [I-D.ietf-spring-srv6-network-programming] 290 Filsfils, C., Camarillo, P., Leddy, J., 291 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 292 Network Programming", draft-ietf-spring-srv6-network- 293 programming-01 (work in progress), July 2019. 295 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 296 Requirement Levels", BCP 14, RFC 2119, 297 DOI 10.17487/RFC2119, March 1997, 298 . 300 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 301 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 302 May 2017, . 304 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 305 Decraene, B., Litkowski, S., and R. Shakir, "Segment 306 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 307 July 2018, . 309 9.2. Informative References 311 [I-D.gandhi-spring-udp-pm] 312 Gandhi, R., Filsfils, C., daniel.voyer@bell.ca, d., 313 Salsano, S., Ventre, P., and M. Chen, "UDP Path for In- 314 band Performance Measurement for Segment Routing 315 Networks", draft-gandhi-spring-udp-pm-02 (work in 316 progress), September 2018. 318 [I-D.ietf-spring-mpls-path-segment] 319 Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler, 320 "Path Segment in MPLS Based Segment Routing Network", 321 draft-ietf-spring-mpls-path-segment-00 (work in progress), 322 March 2019. 324 [I-D.ietf-spring-segment-routing-mpls] 325 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., 326 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 327 data plane", draft-ietf-spring-segment-routing-mpls-22 328 (work in progress), May 2019. 330 [I-D.ietf-spring-segment-routing-policy] 331 Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., 332 bogdanov@google.com, b., and P. Mattes, "Segment Routing 333 Policy Architecture", draft-ietf-spring-segment-routing- 334 policy-03 (work in progress), May 2019. 336 [I-D.li-6man-srv6-path-segment-encap] 337 Li, C., Cheng, W., Li, Z., and D. Dhody, "Encapsulation of 338 Path Segment in SRv6", draft-li-6man-srv6-path-segment- 339 encap-00 (work in progress), July 2019. 341 [I-D.li-idr-sr-policy-path-segment-distribution] 342 Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing 343 Policies for Path Segment and Bidirectional Path", draft- 344 li-idr-sr-policy-path-segment-distribution-01 (work in 345 progress), October 2018. 347 [I-D.li-pce-sr-bidir-path] 348 Li, C., Chen, M., Cheng, W., Li, Z., Dong, J., Gandhi, R., 349 and Q. Xiong, "PCEP Extensions for Associated 350 Bidirectional Segment Routing (SR) Paths", draft-li-pce- 351 sr-bidir-path-05 (work in progress), March 2019. 353 [I-D.li-pce-sr-path-segment] 354 Li, C., Chen, M., Cheng, W., Dong, J., Li, Z., Gandhi, R., 355 and Q. Xiong, "Path Computation Element Communication 356 Protocol (PCEP) Extension for Path Segment in Segment 357 Routing (SR)", draft-li-pce-sr-path-segment-07 (work in 358 progress), July 2019. 360 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 361 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 362 May 2016, . 364 Authors' Addresses 366 Cheng Li 367 Huawei Technologies 369 Email: chengli13@huawei.com 371 Weiqiang Cheng 372 China Mobile 374 Email: chengweiqiang@chinamobile.com 375 Mach(Guoyi) Chen 376 Huawei Technologies 378 Email: mach.chen@huawei.com 380 Dhruv Dhody 381 Huawei Technologies 382 Divyashree Techno Park, Whitefield 383 Bangalore, Karnataka 560066 384 India 386 Email: dhruv.ietf@gmail.com 388 Zhenbin Li 389 Huawei Technologies 390 Huawei Campus, No. 156 Beiqing Rd. 391 Beijing 100095 392 China 394 Email: lizhenbin@huawei.com 396 Jie Dong 397 Huawei Technologies 398 Huawei Campus, No. 156 Beiqing Rd. 399 Beijing 100095 400 China 402 Email: jie.dong@huawei.com 404 Rakesh Gandhi 405 Cisco Systems, Inc. 406 Canada 408 Email: rgandhi@cisco.com