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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6man Working Group C. Li 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track W. Cheng 5 Expires: November 9, 2021 China Mobile 6 Y. Zhu 7 China Telecom 8 Z. Li 9 D. Dhody 10 Huawei Technologies 11 May 8, 2021 13 Encapsulation of Path Segment in SRv6 14 draft-li-6man-srv6-path-segment-encap-06 16 Abstract 18 Segment Routing (SR) allows for a flexible definition of end-to-end 19 paths by encoding an ordered list of instructions, called "segments". 20 The SR architecture can be implemented over an IPv6 data plane, 21 called SRv6. In some use-cases such as end-to-end SR Path Protection 22 and Performance Measurement (PM), an SRv6 path needs to be 23 identified. An SRv6 Path Segment can be used for identifying an SRv6 24 path. This document defines a P-flag in the Segment Routing Header 25 to indicate the appearence of SRv6 Path Segment. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on November 9, 2021. 44 Copyright Notice 46 Copyright (c) 2021 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 63 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Encoding of an SRv6 Path Segment . . . . . . . . . . . . . . 3 65 2.1. SRH.P-flag . . . . . . . . . . . . . . . . . . . . . . . 4 66 3. Processing of SRv6 Path Segment . . . . . . . . . . . . . . . 5 67 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 69 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 70 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 71 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 72 7.2. Informative References . . . . . . . . . . . . . . . . . 7 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 75 1. Introduction 77 Segment routing (SR) [RFC8402] is a source routing paradigm that 78 explicitly indicates the forwarding path for packets at the ingress 79 node by inserting an ordered list of instructions, called segments. 81 When segment routing is deployed on an IPv6 data plane, it is called 82 SRv6, and it uses a new IPv6 [RFC8200] Routing Header (EH) called the 83 IPv6 Segment Routing Header (SRH) [RFC8754] to construct an SRv6 84 path. As per [RFC8986], an SRv6 segment identifier is a 128-bit 85 value. 87 In several use cases, such as binding bidirectional path 88 [I-D.ietf-pce-sr-bidir-path] and end-to-end performance measurement 89 [I-D.gandhi-spring-twamp-srpm], the ability to implement path 90 identification is a pre-requisite. 92 An SRv6 path MAY be identified by the content of a segment list in 93 the SRH. However, the segment list may not be a good key, since the 94 length of a segment list is flexible according to the number of 95 required SIDs. Also, the length of a segment list may be too long to 96 be a key when it contains many SIDs. For instance, if packet A uses 97 an SRH with 3 SIDs while Packet B uses an SRH with 10 SIDs, the key 98 to identify these two paths will be a 384-bits value and a 1280-bits 99 value, respectively. Furthermore, an SRv6 path cannot be identified 100 by the information carried by the SRH in reduced mode [RFC8754] as 101 the first SID is not present. Also, different SRv6 policies may use 102 the same segment list for different candidate paths, so the traffic 103 of different SRv6 policies are merged, resulting in the inability to 104 measure the performance of the specific path. Therefore, 105 [I-D.ietf-spring-srv6-path-segment] defines an SRv6 Path Segment to 106 identify an SRv6 path. 108 This document defines a P-bit in SRH to indicate the appearence of 109 SRv6 Path Segment in SRH. 111 1.1. Requirements Language 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 115 "OPTIONAL" in this document are to be interpreted as described in BCP 116 14 [RFC2119] [RFC8174] when, and only when, they appear in all 117 capitals, as shown here. 119 1.2. Terminology 121 PM: Performance Measurement. 123 SID: Segment ID. 125 SL: Segment List. 127 SR: Segment Routing. 129 SRH: Segment Routing Header. 131 PSID: Path Segment Identifier. 133 PSP: Penultimate Segment Popping. 135 Further, this document makes use of the terms defined in [RFC8402] 136 and [RFC8986]. 138 2. Encoding of an SRv6 Path Segment 140 This section describes the SRH encoding of an SRv6 Path Segment 141 [I-D.ietf-spring-srv6-path-segment]. 143 2.1. SRH.P-flag 145 As per [I-D.ietf-spring-srv6-path-segment], an SRv6 Path Segment is a 146 128-bits value, and it MUST appear only once in a SID list, and it 147 MUST appear as the last entry. 149 To indicate the existence of a Path Segment in the SRH, this document 150 defines a P-flag in the SRH flag field. The encapsulation of SRv6 151 Path Segment is shown below. 153 0 1 2 3 154 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | Next Header | Hdr Ext Len | Routing Type | Segments Left | 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 158 | Last Entry | Flags |P| Tag | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | | 161 | Segment List[0] (128 bits IPv6 address) | 162 | | 163 | | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | | 166 | | 167 ... 168 | | 169 | | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | | 172 | Segment List[n-1] (128 bits IPv6 address) | 173 | | 174 | | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 | | 177 | SRv6 Path Segment (Segment List[n],128 bits IPv6 value) | 178 | | 179 | | 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 // // 182 // Optional Type Length Value objects (variable) // 183 // // 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 186 Figure 1. SRv6 Path Segment in SID List 188 o P-bit: set when SRv6 Path Segment is inserted. It MUST be ignored 189 when a node does not support SRv6 Path Segment processing. 191 SRH.P-bit processing can be enabled or disabled by configuration on 192 devices, it can be done by CLI, NETCONF YANG or other ways, and this 193 is out of the scope of this document. 195 The pseudo code of SRH.P-bit processing is described as below. 197 S01. if SRH.P-flag processing is enabled: 198 S02. if SRH.P-flag is set: 199 S03. SRv6 Path Segment processing ;;ref1 201 Ref1: The SRv6 Path Segment processing is accosiated with the 202 specific application, such as SRv6 Path Segment based Performance 203 measurement, and this is out of the scope of this document. 205 In some use cases, only the egress need to process the SRv6 Path 206 Segment, therefore, the P-bit processing can be done at the egress 207 node only while the intermediate nodes do not need to process it. 208 This feature can be enabled by configuration like CLI , NETCONF YANG 209 or other ways. In this case, the pseudo code is described as below. 211 S01. if SRH.P-flag processing is enabled: 212 S02. if intermediate node processing is disabled: 213 S03. if SRH.P-flag is set and SRH.SL == 0: 214 S03. SRv6 Path Segment processing 215 S04 else: 216 S05. if SRH.P-flag is set: 217 S06. SRv6 Path Segment processing 219 3. Processing of SRv6 Path Segment 221 The processing of SRv6 path segment is out of the scope of this 222 document and is defined in [I-D.ietf-spring-srv6-path-segment]. 224 4. IANA Considerations 226 This document requests IANA to allocate bit position TBA within the 227 "Segment Routing Header Flags" registry defined in [RFC8402]. 229 5. Security Considerations 231 TBA 233 6. Acknowledgements 235 TBA 237 7. References 239 7.1. Normative References 241 [I-D.ietf-spring-srv6-path-segment] 242 Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi, 243 "Path Segment for SRv6 (Segment Routing in IPv6)", draft- 244 ietf-spring-srv6-path-segment-00 (work in progress), 245 November 2020. 247 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 248 Requirement Levels", BCP 14, RFC 2119, 249 DOI 10.17487/RFC2119, March 1997, 250 . 252 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 253 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 254 May 2017, . 256 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 257 (IPv6) Specification", STD 86, RFC 8200, 258 DOI 10.17487/RFC8200, July 2017, 259 . 261 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 262 Decraene, B., Litkowski, S., and R. Shakir, "Segment 263 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 264 July 2018, . 266 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 267 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 268 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 269 . 271 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 272 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 273 (SRv6) Network Programming", RFC 8986, 274 DOI 10.17487/RFC8986, February 2021, 275 . 277 7.2. Informative References 279 [I-D.gandhi-spring-twamp-srpm] 280 Gandhi, R., Filsfils, C., Voyer, D., Chen, M., and B. 281 Janssens, "Performance Measurement Using TWAMP Light for 282 Segment Routing Networks", draft-gandhi-spring-twamp- 283 srpm-11 (work in progress), October 2020. 285 [I-D.ietf-idr-sr-policy-path-segment] 286 Li, C., Li, Z., Chen, H., Cheng, W., and K. Talaulikar, 287 "SR Policy Extensions for Path Segment and Bidirectional 288 Path", draft-ietf-idr-sr-policy-path-segment-03 (work in 289 progress), March 2021. 291 [I-D.ietf-pce-sr-bidir-path] 292 Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong, 293 "Path Computation Element Communication Protocol (PCEP) 294 Extensions for Associated Bidirectional Segment Routing 295 (SR) Paths", draft-ietf-pce-sr-bidir-path-05 (work in 296 progress), January 2021. 298 [I-D.ietf-pce-sr-path-segment] 299 Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong, 300 "Path Computation Element Communication Protocol (PCEP) 301 Extension for Path Segment in Segment Routing (SR)", 302 draft-ietf-pce-sr-path-segment-03 (work in progress), 303 February 2021. 305 [I-D.ietf-spring-segment-routing-policy] 306 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 307 P. Mattes, "Segment Routing Policy Architecture", draft- 308 ietf-spring-segment-routing-policy-11 (work in progress), 309 April 2021. 311 Authors' Addresses 313 Cheng Li 314 Huawei Technologies 316 Email: c.l@huawei.com 318 Weiqiang Cheng 319 China Mobile 321 Email: chengweiqiang@chinamobile.com 322 Yongqing Zhu 323 China Telecom 324 Guangzhou 326 Email: zhuyq8@chinatelecom.cn 328 Zhenbin Li 329 Huawei Technologies 330 Huawei Campus, No. 156 Beiqing Rd. 331 Beijing 100095 332 China 334 Email: lizhenbin@huawei.com 336 Dhruv Dhody 337 Huawei Technologies 338 Divyashree Techno Park, Whitefield 339 Bangalore 560066 340 India 342 Email: dhruv.ietf@gmail.com