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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-ietf-isis-prefix-attributes-02 == Outdated reference: A later version (-25) exists of draft-ietf-isis-segment-routing-extensions-05 == Outdated reference: A later version (-15) exists of draft-ietf-spring-segment-routing-06 Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Previdi, Ed. 3 Internet-Draft L. Ginsberg 4 Intended status: Standards Track C. Filsfils 5 Expires: June 16, 2016 Cisco Systems, Inc. 6 December 14, 2015 8 Segment Routing IPv6 Prefix-SID 9 draft-previdi-isis-ipv6-prefix-sid-01 11 Abstract 13 This document defines the Segment Routing IPv6 Prefix-SID sub-TLV. 14 This new sub-TLV allows to specify which of the prefixes advertised 15 by a node are to be used as Segment Routing Identifiers (SID) for the 16 IPv6 dataplane. 18 Requirements Language 20 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 21 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 22 document are to be interpreted as described in RFC 2119 [RFC2119]. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on June 16, 2016. 41 Copyright Notice 43 Copyright (c) 2015 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. SRv6 Prefix SID . . . . . . . . . . . . . . . . . . . . . . . 2 60 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 62 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 63 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 6.1. Normative References . . . . . . . . . . . . . . . . . . 5 65 6.2. Informative References . . . . . . . . . . . . . . . . . 5 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 With Segment Routing (SR)[I-D.ietf-spring-segment-routing], a node 71 steers a packet through an ordered list of instructions, called 72 segments. Segments are identified through Segment Identifiers (SIDs) 73 that are advertised by routing protocols. The IS-IS extensions for 74 SR information advertisement are defined in 75 [I-D.ietf-isis-segment-routing-extensions]. 77 Segment Routing can be directly applied to the IPv6 dataplane through 78 the use of the Segment Routing Header defined in 79 [I-D.previdi-6man-segment-routing-header]. 81 When applied to the IPv6 dataplane, the SID is represented by an IPv6 82 address. This document defines a new IS-IS Prefix sub-TLV where 83 information related to the IPv6 address used as SR-IPv6 SID is 84 conveyed. 86 2. SRv6 Prefix SID 88 When SR is applied to the IPv6 dataplane, Segment Identifiers (SIDs) 89 are regular IPv6 addresses that are advertised in routing protocols. 90 When SR is used over IPv6 dataplane, it is desirable to identify 91 which of the prefixes originated by a node can be used as SIDs 92 compared to any other prefix that the node advertises. Moreover, and 93 in order to provide the same functionalities defined in 94 [I-D.ietf-spring-segment-routing] and 95 [I-D.ietf-isis-segment-routing-extensions], a new sub-TLV is defined: 96 the SRv6-Prefix-SID sub-TLV 97 A SRv6-Prefix-SID sub-TLV is associated to a IPv6 prefix advertised 98 by a node and MAY be present in any of the following TLVs: 100 TLV-236 (IPv6) defined in [RFC5308]. 102 TLV-237 (MT-IPv6) defined in [RFC5120]. 104 The SRv6-Prefix-SID sub-TLV has the following format: 106 0 1 2 3 107 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 1 108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 109 | Type | Length | Flags | 110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 111 | Algorithm | 112 +-+-+-+-+-+-+-+-+ 114 where: 116 Type: To be assigned by IANA (suggested value 5). 118 Length: 3 octets. 120 Flags: 2 octet field of flags. None of them is defined at this 121 stage. 123 Algorithm: the router may use various algorithms when calculating 124 reachability to other nodes or to prefixes attached to these 125 nodes. Algorithms identifiers are defined in 126 [I-D.ietf-isis-segment-routing-extensions]. Examples of these 127 algorithms are metric based Shortest Path First (SPF), various 128 sorts of Constrained SPF, etc. The algorithm field of the SRv6- 129 Prefix-SID contains the identifier of the algorithm the router has 130 used in order to compute the reachability of the IPv6 prefix that 131 is used as a SID. At origination, the SRv6-Prefix-SID algorithm 132 field MUST be set to 0 on all SRv6-Prefix-SIDs of prefixes 133 computed using SPF algorithm (Shortest Path First). On reception 134 of the SRv6-Prefix-SID sub-TLV, any non-zero algorithm value MUST 135 match what advertised in the SR-Algorithm sub-TLV (as defined in 136 [I-D.ietf-isis-segment-routing-extensions]). 138 A router advertising an IPv6 prefix with the SRv6-Prefix-SID sub-TLV 139 MUST support the Segment Routing Header (SRH, defined in 140 [I-D.previdi-6man-segment-routing-header] and its associated 141 procedures for packets destined to the advertised prefix. The 142 advertising router MUST also set the H-flag in the SR-Capability sub- 143 TLV as defined in [I-D.ietf-isis-segment-routing-extensions]. 145 Within an area (or within the level-2 subdomain), a router receiving 146 the advertisement of an IPv6 prefix with the SRv6-Prefix-SID sub-TLV 147 MUST check whether the originator has set the H-flag in its SR- 148 Capability Sub-TLV prior to validate the SRv6-Prefix-SID sub-TLV. 150 A router receiving a SRv6-Prefix-SID from a remote node and with an 151 algorithm value that such remote node has not advertised in the SR- 152 Capability sub-TLV (as defined in 153 [I-D.ietf-isis-segment-routing-extensions]) MUST ignore the SRv6- 154 Prefix-SID sub-TLV. 156 The SRv6-Prefix-SID sub-TLV defines the prefix (it is associated to) 157 as an SR-IPv6 Prefix SID. If the prefix is to be used as a Node-SID: 159 The IPv6 prefix MUST be advertised with the SRv6-Prefix-SID sub- 160 TLV attached. 162 The N-flag defined in [I-D.ietf-isis-prefix-attributes] MUST be 163 set. 165 3. IANA Considerations 167 This document makes the following registrations in the "sub-TLVs for 168 TLV 135,235,236 and 237" registry. 170 Type: TBD (suggested value 5) 172 Description: SRv6 Prefix Segment Identifier 174 TLV 135: no 176 TLV 235: no 178 TLV 236: yes 180 TLV 237: yes 182 Reference: This document (Section 2) 184 4. Security Considerations 186 This document doesn't introduce new security considerations. 188 5. Acknowledgements 190 The authors would like to thank Nagendra Kumar for his review of this 191 document. 193 6. References 195 6.1. Normative References 197 [I-D.ietf-isis-prefix-attributes] 198 Ginsberg, L., Decraene, B., Filsfils, C., Litkowski, S., 199 Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix 200 Attributes for Extended IP and IPv6 Reachability", draft- 201 ietf-isis-prefix-attributes-02 (work in progress), 202 December 2015. 204 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 205 Requirement Levels", BCP 14, RFC 2119, 206 DOI 10.17487/RFC2119, March 1997, 207 . 209 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 210 Topology (MT) Routing in Intermediate System to 211 Intermediate Systems (IS-ISs)", RFC 5120, 212 DOI 10.17487/RFC5120, February 2008, 213 . 215 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 216 DOI 10.17487/RFC5308, October 2008, 217 . 219 6.2. Informative References 221 [I-D.ietf-isis-segment-routing-extensions] 222 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 223 Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS 224 Extensions for Segment Routing", draft-ietf-isis-segment- 225 routing-extensions-05 (work in progress), June 2015. 227 [I-D.ietf-spring-segment-routing] 228 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 229 and r. rjs@rob.sh, "Segment Routing Architecture", draft- 230 ietf-spring-segment-routing-06 (work in progress), October 231 2015. 233 [I-D.previdi-6man-segment-routing-header] 234 Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, 235 J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment 236 Routing Header (SRH)", draft-previdi-6man-segment-routing- 237 header-08 (work in progress), October 2015. 239 Authors' Addresses 241 Stefano Previdi (editor) 242 Cisco Systems, Inc. 243 Via Del Serafico, 200 244 Rome 00142 245 Italy 247 Email: sprevidi@cisco.com 249 Les Ginsberg 250 Cisco Systems, Inc. 251 US 253 Email: ginsberg@cisco.com 255 Clarence Filsfils 256 Cisco Systems, Inc. 257 Brussels 258 BE 260 Email: cfilsfil@cisco.com