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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group J. Tantsura 3 Internet-Draft Nuage Networks 4 Intended status: Standards Track U. Chunduri 5 Expires: February 14, 2019 Huawei USA 6 G. Mirsky 7 ZTE Corp. 8 S. Sivabalan 9 Cisco 10 August 13, 2018 12 Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link- 13 State 14 draft-ietf-idr-bgp-ls-segment-routing-msd-02 16 Abstract 18 This document defines a way for a Border Gateway Protocol Link-State 19 (BGP-LS) speaker to advertise multiple types of supported Maximum SID 20 Depths (MSDs) at node and/or link granularity. 22 Such advertisements allow logically centralized entities (e.g., 23 centralized controllers) to determine whether a particular SID stack 24 can be supported in a given network. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on February 14, 2019. 43 Copyright Notice 45 Copyright (c) 2018 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Conventions used in this document . . . . . . . . . . . . 3 64 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 65 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 66 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 67 3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3 68 4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4 69 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 70 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 71 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 72 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 73 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 74 8.2. Informative References . . . . . . . . . . . . . . . . . 6 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 77 1. Introduction 79 When Segment Routing tunnels are computed by a centralized 80 controller, it is critical that the controller learns the MSD 81 "Maximum SID Depth" of the node or link SR tunnel exits over, so the 82 SID stack depth of a path computed doesn't exceed the number of SIDs 83 the node is capable of imposing. This document describes how to use 84 BGP-LS to signal the MSD of a node or link to a centralized 85 controller. 87 PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD 88 in SR PCE Capability TLV and METRIC Object. However, if PCEP is not 89 supported/configured on the head-end of a SR tunnel or a Binding-SID 90 anchor node and controller does not participate in IGP routing, it 91 has no way to learn the MSD of nodes and links which has been 92 configured. BGP-LS [RFC7752] defines a way to expose topology and 93 associated attributes and capabilities of the nodes in that topology 94 to a centralized controller. 96 Other types of MSD are known to be useful. For example, 97 [I-D.ietf-ospf-mpls-elc] and [I-D.ietf-isis-mpls-elc] define Readable 99 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 101 Label Depth Capability (RLDC) that is used by a head-end to insert an 102 Entropy Label (EL) at a depth that can be read by transit nodes. 104 1.1. Conventions used in this document 106 1.1.1. Terminology 108 BGP-LS: Distribution of Link-State and TE Information using Border 109 Gateway Protocol 111 MSD: Maximum SID Depth 113 PCC: Path Computation Client 115 PCE: Path Computation Element 117 PCEP: Path Computation Element Protocol 119 SID: Segment Identifier 121 SR: Segment routing 123 1.1.2. Requirements Language 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 127 "OPTIONAL" in this document are to be interpreted as described in BCP 128 14 [RFC2119] [RFC8174] when, and only when, they appear in all 129 capitals, as shown here . 131 2. Problem Statement 133 In existing technology only PCEP has extension to signal the MSD (SR 134 PCE Capability TLV/ METRIC Object as defined in 135 [I-D.ietf-pce-segment-routing],If PCEP is not supported by the node 136 (head-end of the SR tunnel) controller has no way to learn the MSD of 137 the node/link configured. OSPF and IS-IS extensions are defined in: 139 [I-D.ietf-ospf-segment-routing-msd] 141 [I-D.ietf-isis-segment-routing-msd] 143 3. MSD supported by a node 145 Node MSD is encoded in a new Node Attribute TLV, as defined in 146 [RFC7752] 148 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 150 0 1 2 3 151 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 1 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | Type | Length | 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 | Sub-Type and Value ... 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 158 Figure 1: Node attribute format 160 Type : A 2-octet field specifying code-point of the new TLV type. 161 Code-point:(TBD1) from BGP-LS Node Descriptor, Link Descriptor, 162 Prefix Descriptor, and Attribute TLVs registry 164 Length: A 2-octet field that indicates the length of the value 165 portion 167 Sub-Type and value fields are as defined in corresponding OSPF 168 [I-D.ietf-ospf-segment-routing-msd] and IS-IS 169 [I-D.ietf-isis-segment-routing-msd] extensions. 171 4. MSD supported on a link 173 Link MSD is encoded in a New Link Attribute TLV, as defined in 174 [RFC7752] 176 0 1 2 3 177 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 1 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 | Type | Length | 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | Sub-Type and Value ... 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 184 Figure 2: Link attribute format 186 Type : A 2-octet field specifying code-point of the new TLV type. 187 Code-point:(TBD2) from BGP-LS Node Descriptor, Link Descriptor, 188 Prefix Descriptor, and Attribute TLVs registry 190 Length: A 2-octet field that indicates the length of the value 191 portion 193 Sub-Type and value fields are as defined in corresponding OSPF 194 [I-D.ietf-ospf-segment-routing-msd] and IS-IS 195 [I-D.ietf-isis-segment-routing-msd] extensions. 197 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 199 5. IANA Considerations 201 We request IANA assign code points from the registry BGP-LS Node 202 Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs, 203 as follows: TLV Code Point Description IS-IS TLV/Sub-TLV Reference 204 TBD1 Node MSD 242/23 (this document) TBD2 Link MSD 205 (22,23,25,141,222,223)/15 (this document) 207 6. Security Considerations 209 Advertisement of the additional information defined in this document 210 that is false, e.g., an MSD that is incorrect, may result in a path 211 computation failing, having a service unavailable, or instantiation 212 of a path that can't be supported by the head-end (the node 213 performing the imposition). 215 This document does not introduce security issues beyond those 216 discussed in [RFC7752], [I-D.ietf-ospf-segment-routing-msd] and 217 [I-D.ietf-isis-segment-routing-msd] 219 7. Acknowledgements 221 We like to thank Nikos Triantafillis, Acee Lindem, Ketan Talaulikar, 222 Stephane Litkowski and Bruno Decraene for their reviews and valuable 223 comments. 225 8. References 227 8.1. Normative References 229 [I-D.ietf-isis-segment-routing-msd] 230 Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 231 "Signaling MSD (Maximum SID Depth) using IS-IS", draft- 232 ietf-isis-segment-routing-msd-13 (work in progress), July 233 2018. 235 [I-D.ietf-ospf-segment-routing-msd] 236 Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, 237 "Signaling MSD (Maximum SID Depth) using OSPF", draft- 238 ietf-ospf-segment-routing-msd-15 (work in progress), July 239 2018. 241 [I-D.ietf-pce-segment-routing] 242 Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 243 and J. Hardwick, "PCEP Extensions for Segment Routing", 244 draft-ietf-pce-segment-routing-12 (work in progress), June 245 2018. 247 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 249 [I-D.ietf-spring-segment-routing-mpls] 250 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., 251 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 252 data plane", draft-ietf-spring-segment-routing-mpls-14 253 (work in progress), June 2018. 255 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 256 Requirement Levels", BCP 14, RFC 2119, 257 DOI 10.17487/RFC2119, March 1997, 258 . 260 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 261 S. Ray, "North-Bound Distribution of Link-State and 262 Traffic Engineering (TE) Information Using BGP", RFC 7752, 263 DOI 10.17487/RFC7752, March 2016, 264 . 266 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 267 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 268 May 2017, . 270 8.2. Informative References 272 [I-D.ietf-isis-mpls-elc] 273 Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 274 Litkowski, "Signaling Entropy Label Capability and Entropy 275 Readable Label Depth Using IS-IS", draft-ietf-isis-mpls- 276 elc-05 (work in progress), July 2018. 278 [I-D.ietf-isis-segment-routing-extensions] 279 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 280 Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura, 281 "IS-IS Extensions for Segment Routing", draft-ietf-isis- 282 segment-routing-extensions-19 (work in progress), July 283 2018. 285 [I-D.ietf-ospf-mpls-elc] 286 Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 287 Litkowski, "Signaling Entropy Label Capability and Entropy 288 Readable Label-stack Depth Using OSPF", draft-ietf-ospf- 289 mpls-elc-06 (work in progress), August 2018. 291 [I-D.ietf-ospf-segment-routing-extensions] 292 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 293 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 294 Extensions for Segment Routing", draft-ietf-ospf-segment- 295 routing-extensions-25 (work in progress), April 2018. 297 Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018 299 Authors' Addresses 301 Jeff Tantsura 302 Nuage Networks 304 Email: jefftant.ietf@gmail.com 306 Uma Chunduri 307 Huawei USA 309 Email: uma.chunduri@huawei.com 311 Greg Mirsky 312 ZTE Corp. 314 Email: gregimirsky@gmail.com 316 Siva Sivabalan 317 Cisco 319 Email: msiva@cisco.com