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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 G. Mirsky 4 Intended status: Standards Track Ericsson 5 Expires: September 10, 2016 S. Sivabalan 6 Cisco 7 U. Chunduri 8 Ericsson 9 March 9, 2016 11 Signaling Maximum SID Depth using Border Gateway Protocol Link-State 12 draft-tantsura-idr-bgp-ls-segment-routing-msd-00 14 Abstract 16 This document discusses use of BGP-LS to expose node and/or link on a 17 node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN). 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on September 10, 2016. 36 Copyright Notice 38 Copyright (c) 2016 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Conventions used in this document . . . . . . . . . . . . 2 55 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 2 56 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 57 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 58 3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3 59 4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 3 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 62 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 63 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 65 8.2. Informative References . . . . . . . . . . . . . . . . . 5 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 68 1. Introduction 70 When Segment Routing tunnels are computed by a centralized 71 controller, it is crucial that the controller knows MSD "Maximum SID 72 Depth" of the node or link SR tunnel exits over, so it doesn't 73 download a path with SID (label stack) of a depth more than the node 74 or link configured is capable of imposing.This document describes how 75 to use BGP-LS to expose the MSD of the node or link configured to a 76 centralized controller. 78 1.1. Conventions used in this document 80 1.1.1. Terminology 82 BGP-LS: Distribution of Link-State and TE Information using Border 83 Gateway Protocol 85 MSD: Maximum SID Depth 87 PCC: Path Computation Client 89 PCE: Path Computation Element 91 PCEP: Path Computation Element Protocol 93 SID: Segment Identifier 95 SR: Segment routing 97 1.1.2. Requirements Language 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in 102 [RFC2119]. 104 2. Problem Statement 106 In existing technology only PCEP has extension to signal the MSD (SR 107 PCE Capability TLV/ METRIC Object as defined in 108 [I-D.ietf-pce-segment-routing],If PCEP is not supported by the node 109 (head-end of the SR tunnel) controller has no way to learn the MSD of 110 the node/link configured. 112 3. MSD supported by a node 114 Node MSD is a number in the range of 0-254. The vaule of 0 115 represents lack of ability to push MSD of any depth, any other value 116 represents that of the node. 118 Node MSD is encoded in the Opaque Node Attribute TLV, as defined in 119 [I-D.ietf-idr-ls-distribution] 121 0 1 2 3 122 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 1 123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 124 | Type | Length | 125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 // Opaque node attributes (variable) // 127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 Figure 1: Opaque Node attribute format 131 4. MSD supported on a link 133 Link MSD is a number in the range of 0-254.The value of 0 represents 134 lack of ability to push MSD of any depth, any other value represents 135 that of the link. 137 Link MSD is encoded in the Opaque Link Attribute TLV, as defined in 138 [I-D.ietf-idr-ls-distribution] 139 0 1 2 3 140 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 1 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 | Type | Length | 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 // Opaque link attributes (variable) // 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 147 Figure 2: Opaque link attribute format 149 5. IANA Considerations 151 TBA 153 6. Security Considerations 155 This document does not introduce security issues beyond those 156 discussed in [I-D.ietf-idr-ls-distribution] 158 7. Acknowledgements 160 We like to thank Nikos Triantafillis for the valuable comments. 162 8. References 164 8.1. Normative References 166 [I-D.ietf-idr-ls-distribution] 167 Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. 168 Ray, "North-Bound Distribution of Link-State and TE 169 Information using BGP", draft-ietf-idr-ls-distribution-13 170 (work in progress), October 2015. 172 [I-D.ietf-pce-segment-routing] 173 Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., 174 Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick, 175 "PCEP Extensions for Segment Routing", draft-ietf-pce- 176 segment-routing-06 (work in progress), August 2015. 178 [I-D.ietf-spring-segment-routing-mpls] 179 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 180 Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J., 181 and E. Crabbe, "Segment Routing with MPLS data plane", 182 draft-ietf-spring-segment-routing-mpls-03 (work in 183 progress), February 2016. 185 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 186 Requirement Levels", BCP 14, RFC 2119, 187 DOI 10.17487/RFC2119, March 1997, 188 . 190 8.2. Informative References 192 [I-D.ietf-isis-segment-routing-extensions] 193 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 194 Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS 195 Extensions for Segment Routing", draft-ietf-isis-segment- 196 routing-extensions-06 (work in progress), December 2015. 198 [I-D.ietf-ospf-segment-routing-extensions] 199 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 200 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 201 Extensions for Segment Routing", draft-ietf-ospf-segment- 202 routing-extensions-06 (work in progress), December 2015. 204 Authors' Addresses 206 Jeff Tantsura 207 Ericsson 209 Email: jeff.tantsura@ericsson.com 211 Greg Mirsky 212 Ericsson 214 Email: gregory.mirsky@ericsson.com 216 Siva Sivabalan 217 Cisco 219 Email: msiva@cisco.com 221 Uma Chunduri 222 Ericsson 224 Email: uma.chunduri@ericsson.com