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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group U. Chunduri 3 Internet-Draft Y. Qu 4 Intended status: Standards Track Huawei USA 5 Expires: April 25, 2019 October 22, 2018 7 Multiple Algorithm support for IS-IS Prefixes 8 draft-chunduri-lsr-isis-prefix-multi-algo-01 10 Abstract 12 This document specifies an extension to Intermediate System to 13 Intermediate System (IS-IS) protocol by adding an Algorithm support 14 for prefixes advertised. This allows multiple independent algorithm 15 usage for computing the reachability of nodes and prefixes as opposed 16 to only one algorithm. 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 RFC2119 [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 https://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 April 25, 2019. 41 Copyright Notice 43 Copyright (c) 2018 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 (https://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 1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. IS-IS Route Computation Algorithm sub-TLV in prefixes . . . . 3 61 3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 4 62 3.1. Single Topology or Multi-Topology Mode . . . . . . . . . 4 63 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 64 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 66 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 68 7.2. Informative References . . . . . . . . . . . . . . . . . 6 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 71 1. Introduction 73 Reachability of various nodes or prefixes attached to these nodes is 74 done through Shortest Path First (SPF) algorithm as defined in 75 [ISO10589]. This is done today with in a single topology [RFC5305] 76 [RFC5308] or in multi-topology (MT) routing [RFC5120] and with out 77 any explicit advertisement of computation algorithm that is being 78 used. 80 IS-IS Segment Routing (SR) extensions 81 [I-D.ietf-isis-segment-routing-extensions], extended the support for 82 reachability computation for other algorithms other than SPF. This 83 is done by advertising the computation algorithms supported at node 84 level and also by advertising the algorithm being supported by Prefix 85 Segment Identifier (SID) sub-TLV advertised in reachability prefixes. 87 While the above would give the flexibility to use different 88 reachability computation algorithm than the SPF, it is restricted to 89 one particular data plane as opposed to the prefix itself. This 90 document removes that restriction and advertises the algorithm to be 91 used for reachability computation in the prefix itself, thus applying 92 the same to any underlying data plane (E.g. SR-MPLS, SRH, IPv6, 93 IPv4). 95 Section 2 details the details of the sub-TLV and Section 3 talks 96 about how to use te same and restrictions around it. 98 1.1. Acronyms 100 IGP - Interior Gateway Protocols 102 IS-IS - Intermediate System to Intermediate System 104 LSR - Link State Routing 106 MT - Multi Topology 108 OSPF - Open Shortest Path First 110 SID - Segment Identifier 112 SR - Segment Routing 114 2. IS-IS Route Computation Algorithm sub-TLV in prefixes 116 This section defines the encoding of Route Computation Algorithm 117 (RCA) value that MUST be used while calculating the reachability to 118 other nodes or to the prefixes attached to the other nodes. The RCA 119 sub-TLV has the following format: 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 | Flags | Algorithm | 125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 // sub-sub-TLVs // 127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 Figure 1: Route Computation Algorithm - sub-TLV Format 131 Type - TBD (IANA) from Sub-TLVs for TLVs 135, 235, 236, and 237 132 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT 133 IPv6 IP. Reach TLVs) registry. 135 Length - Total length of the value field in bytes (variable). 137 Flags - TBD 139 Algorithm - Route Computation Algorithm value as defined in "IGP 140 Algorithm Types" registry defined under "Interior Gateway Protocol 141 (IGP) Parameters" IANA registries. 143 sub-sub-TLVs - Optional and can be used to specify any information 144 w.r.t to the algorithm being advertised with this prefix (TBD). 146 If multiple algorithms have to be adevrtised for the prefix, multiple 147 instances of this sub-TLV with different algorithms can be used. If 148 Algorithm value is '0' is the only algorithm on the prefix, it is 149 optional to advertise it in this sub-TLV. Thus, not including such a 150 sub-TLV in the prefix implies Algorithm value '0' capability only. 152 3. Elements of Procedure 154 When provisioned an IS-IS node MUST compute reachability for more 155 than one algorithm as indicated in the reachability prefix through 156 this sub-TLV. 158 Default metrics used for computation of any algorithm MUST be as 159 defined in [RFC5120]. However, a particular algorithm can define 160 other than default metrics and can be used while doing the 161 computation. If non-default metrics are being used, those MUST be 162 configured on the links and MUST be advertised through IS-IS Area/ 163 domain. 165 If a prefix is provisioned with multiple algorithms and after the 166 reachability computation, nexthop is different for each algorithm it 167 MUST use the lowest algorithm number to resolve the conflict. 169 Once computation is done with the specified algorithm, this is 170 applicable to all the data planes that are being supported for the 171 prefix. If a particular data plane specific 'algorithms' as defined 172 is in [I-D.ietf-isis-segment-routing-extensions] conflict (for e.g. 173 preference) with data plane independent prefix algorithm (as defined 174 in this draft); preference defined in a particular data plane MUST be 175 used. 177 3.1. Single Topology or Multi-Topology Mode 179 An SPF trigger can be common to multiple IS-IS Levels or for multiple 180 address families with multi-topologies. Currently there is no 181 specified order for reachability computation today and it is 182 implementation dependent. This document specifies the order of 183 reachability computation MUST be IS-IS area/level, topology [RFC5120] 184 and algorithm specified in the reachability prefix. Doing 185 computation in a particular order is also important for avoiding 186 micro-loops as described in [I-D.ietf-rtgwg-spf-uloop-pb-statement]. 188 If network uses single topology mode with only IPv4 adress family 189 [RFC 5305] or in Single topology mode with IPv6 address family [RFC 190 5308] - a node configured with multiple algorithms MUST do route 191 computation with all the algorithms as advertised in the prefixes. 192 If network uses MT [RFC 5120], for each MT ID, per algorithm route 193 computation MUST be done. 195 4. Acknowledgements 197 TBD. 199 5. IANA Considerations 201 This document requests IANA to assign a sub-TLV code point from the 202 "Sub-TLVs for TLVs 135, 235, 236, and 237 (Extended IP reachability, 203 MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)" 204 registry as follows: Route Computation Algorithm - Route Computation 205 Algorithm sub-TLV as described in Section 2. 207 TLV # Name 208 ----- -------------------------------------------------------- 209 TBD Route Computation Algorithm sub-TLV in IS-IS Prefix TLVs 211 6. Security Considerations 213 Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310]. 214 Further security analysis for IS-IS protocol is done in [RFC7645] 215 including analysis of both the above documents. Advertisement of the 216 additional information defined in this document introduces no new 217 security concerns in IS-IS protocol. 219 7. References 221 7.1. Normative References 223 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 224 dual environments", RFC 1195, DOI 10.17487/RFC1195, 225 December 1990, . 227 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 228 Requirement Levels", BCP 14, RFC 2119, 229 DOI 10.17487/RFC2119, March 1997, 230 . 232 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 233 Topology (MT) Routing in Intermediate System to 234 Intermediate Systems (IS-ISs)", RFC 5120, 235 DOI 10.17487/RFC5120, February 2008, 236 . 238 7.2. Informative References 240 [I-D.ietf-isis-segment-routing-extensions] 241 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 242 Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura, 243 "IS-IS Extensions for Segment Routing", draft-ietf-isis- 244 segment-routing-extensions-19 (work in progress), July 245 2018. 247 [I-D.ietf-rtgwg-spf-uloop-pb-statement] 248 Litkowski, S., Decraene, B., and M. Horneffer, "Link State 249 protocols SPF trigger and delay algorithm impact on IGP 250 micro-loops", draft-ietf-rtgwg-spf-uloop-pb-statement-07 251 (work in progress), May 2018. 253 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 254 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 255 2008, . 257 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 258 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 259 2008, . 261 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 262 DOI 10.17487/RFC5308, October 2008, 263 . 265 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 266 and M. Fanto, "IS-IS Generic Cryptographic 267 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 268 2009, . 270 [RFC7645] Chunduri, U., Tian, A., and W. Lu, "The Keying and 271 Authentication for Routing Protocol (KARP) IS-IS Security 272 Analysis", RFC 7645, DOI 10.17487/RFC7645, September 2015, 273 . 275 Authors' Addresses 277 Uma Chunduri 278 Huawei USA 279 2330 Central Expressway 280 Santa Clara, CA 95050 281 USA 283 Email: uma.chunduri@huawei.com 284 Yingzhen Qu 285 Huawei USA 286 2330 Central Expressway 287 Santa Clara, CA 95050 288 USA 290 Email: yingzhen.qu@huawei.com