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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 U. Chunduri 4 Intended status: Standards Track G. Mirsky 5 Expires: July 14, 2017 Individual 6 S. Sivabalan 7 Cisco 8 January 10, 2017 10 Signaling Maximum SID Depth using Border Gateway Protocol Link-State 11 draft-tantsura-idr-bgp-ls-segment-routing-msd-02 13 Abstract 15 This document discusses use of BGP-LS to expose node and/or link on a 16 node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN). 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on July 14, 2017. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 1.1. Conventions used in this document . . . . . . . . . . . . 2 54 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 2 55 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 56 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 57 3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3 58 4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4 59 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 60 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 61 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 62 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 63 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 64 8.2. Informative References . . . . . . . . . . . . . . . . . 5 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 67 1. Introduction 69 When Segment Routing tunnels are computed by a centralized 70 controller, it is crucial that the controller knows MSD "Maximum SID 71 Depth" of the node or link SR tunnel exits over, so it doesn't 72 download a path with SID (label stack) of a depth more than the node 73 or link configured is capable of imposing.This document describes how 74 to use BGP-LS to expose the MSD of the node or link configured to a 75 centralized controller. 77 1.1. Conventions used in this document 79 1.1.1. Terminology 81 BGP-LS: Distribution of Link-State and TE Information using Border 82 Gateway Protocol 84 MSD: Maximum SID Depth 86 PCC: Path Computation Client 88 PCE: Path Computation Element 90 PCEP: Path Computation Element Protocol 92 SID: Segment Identifier 94 SR: Segment routing 96 1.1.2. Requirements Language 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 100 "OPTIONAL" in this document are to be interpreted as described in 101 [RFC2119]. 103 2. Problem Statement 105 In existing technology only PCEP has extension to signal the MSD (SR 106 PCE Capability TLV/ METRIC Object as defined in 107 [I-D.ietf-pce-segment-routing],If PCEP is not supported by the node 108 (head-end of the SR tunnel) controller has no way to learn the MSD of 109 the node/link configured. OSPF and IS-IS extensions are defined in: 111 [I-D.ietf-ospf-segment-routing-msd] 113 [I-D.ietf-isis-segment-routing-msd] 115 3. MSD supported by a node 117 Node MSD is encoded in a new Node Attribute TLV, as defined in 118 [RFC7752] 120 0 1 2 3 121 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 1 122 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 123 | Type | Length | 124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 | MSD | 126 +-+-+-+-+-+-+-+-+ 128 Figure 1: Node attribute format 130 Type : A 2-octet field specifiying code-point of the new TLV type. 131 Code-point: TBA (suggested 1050) from BGP-LS Node Descriptor, Link 132 Descriptor, Prefix Descriptor, and Attribute TLVs registry 134 Length: A 2-octet field that indicates the length of the value 135 portion 137 MSD: Node MSD is a number in the range of 0-254. The vaule of 0 138 represents lack of ability to push MSD of any depth, any other value 139 represents that of the node. 141 4. MSD supported on a link 143 Link MSD is encoded in a New Link Attribute TLV, as defined in 144 [RFC7752] 146 0 1 2 3 147 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 1 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 149 | Type | Length | 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | MSD | 152 +-+-+-+-+-+-+-+-+ 154 Figure 2: Link attribute format 156 Type : A 2-octet field specifiying code-point of the new TLV type. 157 Code-point: TBA (suggested 1110) from BGP-LS Node Descriptor, Link 158 Descriptor, Prefix Descriptor, and Attribute TLVs registry 160 Length: A 2-octet field that indicates the length of the value 161 portion 163 MSD: Link MSD is a number in the range of 0-254. The vaule of 0 164 represents lack of ability to push MSD of any depth, any other value 165 represents that of the link. 167 5. IANA Considerations 169 This document requests assigning 2 new code-points from the BGP-LS 170 Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute 171 TLVs registry as specified in sections 3 and 4. 173 6. Security Considerations 175 This document does not introduce security issues beyond those 176 discussed in [RFC7752] 178 7. Acknowledgements 180 We like to thank Nikos Triantafillis for the valuable comments. 182 8. References 184 8.1. Normative References 186 [I-D.ietf-isis-segment-routing-msd] 187 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 188 Depth) using IS-IS", draft-ietf-isis-segment-routing- 189 msd-00 (work in progress), November 2016. 191 [I-D.ietf-ospf-segment-routing-msd] 192 Tantsura, J. and U. Chunduri, "Signaling MSD (Maximum SID 193 Depth) using OSPF", draft-ietf-ospf-segment-routing-msd-00 194 (work in progress), November 2016. 196 [I-D.ietf-pce-segment-routing] 197 Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., 198 Raszuk, R., Lopez, V., Tantsura, J., Henderickx, W., and 199 J. Hardwick, "PCEP Extensions for Segment Routing", draft- 200 ietf-pce-segment-routing-08 (work in progress), October 201 2016. 203 [I-D.ietf-spring-segment-routing-mpls] 204 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 205 Litkowski, S., Horneffer, M., Shakir, R., 206 jefftant@gmail.com, j., and E. Crabbe, "Segment Routing 207 with MPLS data plane", draft-ietf-spring-segment-routing- 208 mpls-05 (work in progress), July 2016. 210 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 211 Requirement Levels", BCP 14, RFC 2119, 212 DOI 10.17487/RFC2119, March 1997, 213 . 215 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 216 S. Ray, "North-Bound Distribution of Link-State and 217 Traffic Engineering (TE) Information Using BGP", RFC 7752, 218 DOI 10.17487/RFC7752, March 2016, 219 . 221 8.2. Informative References 223 [I-D.ietf-isis-segment-routing-extensions] 224 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 225 Litkowski, S., Decraene, B., and j. jefftant@gmail.com, 226 "IS-IS Extensions for Segment Routing", draft-ietf-isis- 227 segment-routing-extensions-09 (work in progress), October 228 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-10 (work in progress), October 2016. 236 Authors' Addresses 238 Jeff Tantsura 239 Individual 241 Email: jefftant.ietf@gmail.com 243 Uma Chunduri 244 Individual 246 Email: uma.chunduri@gmail.com 248 Greg Mirsky 249 Individual 251 Email: gregimirsky@gmail.com 253 Siva Sivabalan 254 Cisco 256 Email: msiva@cisco.com