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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 Individual 4 Intended status: Standards Track G. Mirsky 5 Expires: January 9, 2017 Ericsson 6 S. Sivabalan 7 Cisco 8 U. Chunduri 9 Ericsson 10 July 8, 2016 12 Signaling Maximum SID Depth using Border Gateway Protocol Link-State 13 draft-tantsura-idr-bgp-ls-segment-routing-msd-01 15 Abstract 17 This document discusses use of BGP-LS to expose node and/or link on a 18 node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN). 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on January 9, 2017. 37 Copyright Notice 39 Copyright (c) 2016 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Conventions used in this document . . . . . . . . . . . . 2 56 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 2 57 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 58 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 59 3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3 60 4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4 61 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 63 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 64 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 66 8.2. Informative References . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 69 1. Introduction 71 When Segment Routing tunnels are computed by a centralized 72 controller, it is crucial that the controller knows MSD "Maximum SID 73 Depth" of the node or link SR tunnel exits over, so it doesn't 74 download a path with SID (label stack) of a depth more than the node 75 or link configured is capable of imposing.This document describes how 76 to use BGP-LS to expose the MSD of the node or link configured to a 77 centralized controller. 79 1.1. Conventions used in this document 81 1.1.1. Terminology 83 BGP-LS: Distribution of Link-State and TE Information using Border 84 Gateway Protocol 86 MSD: Maximum SID Depth 88 PCC: Path Computation Client 90 PCE: Path Computation Element 92 PCEP: Path Computation Element Protocol 94 SID: Segment Identifier 96 SR: Segment routing 98 1.1.2. Requirements Language 100 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 101 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 102 "OPTIONAL" in this document are to be interpreted as described in 103 [RFC2119]. 105 2. Problem Statement 107 In existing technology only PCEP has extension to signal the MSD (SR 108 PCE Capability TLV/ METRIC Object as defined in 109 [I-D.ietf-pce-segment-routing],If PCEP is not supported by the node 110 (head-end of the SR tunnel) controller has no way to learn the MSD of 111 the node/link configured. OSPF and IS-IS extensions are defined in: 113 [I-D.tantsura-ospf-segment-routing-msd] 115 [I-D.tantsura-isis-segment-routing-msd] 117 3. MSD supported by a node 119 Node MSD is encoded in a new Node Attribute TLV, as defined in 120 [RFC7752] 122 0 1 2 3 123 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 1 124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 | Type | Length | 126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 | MSD | 128 +-+-+-+-+-+-+-+-+ 130 Figure 1: Node attribute format 132 Type : A 2-octet field specifiying code-point of the new TLV type. 133 Code-point: TBA (suggested 1050) from BGP-LS Node Descriptor, Link 134 Descriptor, Prefix Descriptor, and Attribute TLVs registry 136 Length: A 2-octet field that indicates the length of the value 137 portion 139 MSD: Node MSD is a number in the range of 0-254. The vaule of 0 140 represents lack of ability to push MSD of any depth, any other value 141 represents that of the node. 143 4. MSD supported on a link 145 Link MSD is encoded in a New Link Attribute TLV, as defined in 146 [RFC7752] 148 0 1 2 3 149 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 1 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | Type | Length | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | MSD | 154 +-+-+-+-+-+-+-+-+ 156 Figure 2: Link attribute format 158 Type : A 2-octet field specifiying code-point of the new TLV type. 159 Code-point: TBA (suggested 1110) from BGP-LS Node Descriptor, Link 160 Descriptor, Prefix Descriptor, and Attribute TLVs registry 162 Length: A 2-octet field that indicates the length of the value 163 portion 165 MSD: Link MSD is a number in the range of 0-254. The vaule of 0 166 represents lack of ability to push MSD of any depth, any other value 167 represents that of the link. 169 5. IANA Considerations 171 This document requests assigning 2 new code-points from the BGP-LS 172 Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute 173 TLVs registry as specified in sections 3 and 4. 175 6. Security Considerations 177 This document does not introduce security issues beyond those 178 discussed in [RFC7752] 180 7. Acknowledgements 182 We like to thank Nikos Triantafillis for the valuable comments. 184 8. References 186 8.1. Normative References 188 [I-D.ietf-pce-segment-routing] 189 Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., 190 Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick, 191 "PCEP Extensions for Segment Routing", draft-ietf-pce- 192 segment-routing-07 (work in progress), March 2016. 194 [I-D.ietf-spring-segment-routing-mpls] 195 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 196 Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J., 197 and E. Crabbe, "Segment Routing with MPLS data plane", 198 draft-ietf-spring-segment-routing-mpls-04 (work in 199 progress), March 2016. 201 [I-D.tantsura-isis-segment-routing-msd] 202 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 203 Depth) using IS-IS", draft-tantsura-isis-segment-routing- 204 msd-01 (work in progress), July 2016. 206 [I-D.tantsura-ospf-segment-routing-msd] 207 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 208 Depth) using OSPF", draft-tantsura-ospf-segment-routing- 209 msd-00 (work in progress), March 2016. 211 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 212 Requirement Levels", BCP 14, RFC 2119, 213 DOI 10.17487/RFC2119, March 1997, 214 . 216 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 217 S. Ray, "North-Bound Distribution of Link-State and 218 Traffic Engineering (TE) Information Using BGP", RFC 7752, 219 DOI 10.17487/RFC7752, March 2016, 220 . 222 8.2. Informative References 224 [I-D.ietf-isis-segment-routing-extensions] 225 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 226 Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS 227 Extensions for Segment Routing", draft-ietf-isis-segment- 228 routing-extensions-07 (work in progress), June 2016. 230 [I-D.ietf-ospf-segment-routing-extensions] 231 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 232 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 233 Extensions for Segment Routing", draft-ietf-ospf-segment- 234 routing-extensions-09 (work in progress), July 2016. 236 Authors' Addresses 238 Jeff Tantsura 239 Individual 241 Email: jefftant.ietf@gmail.com 243 Greg Mirsky 244 Ericsson 246 Email: gregory.mirsky@ericsson.com 248 Siva Sivabalan 249 Cisco 251 Email: msiva@cisco.com 253 Uma Chunduri 254 Ericsson 256 Email: uma.chunduri@ericsson.com