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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Open Shortest Path First Z. Zhang 3 Internet-Draft L. Wang 4 Updates: 2328, 5340 (if approved) Juniper Networks, Inc. 5 Intended status: Standards Track A. Lindem 6 Expires: January 26, 2016 Cisco Systems 7 D. Dubois 8 General Dynamics C4S 9 V. Julka 10 T. McMillan 11 L3 Communications, Linkabit 12 July 25, 2015 14 OSPF Two-part Metric 15 draft-ietf-ospf-two-part-metric-01.txt 17 Abstract 19 This document specifies an optional extension to the OSPF protocol, 20 to represent the metric on a multi-access network as two parts: the 21 metric from a router to the network, and the metric from the network 22 to the router. The router to router metric would be the sum of the 23 two. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 29 document are to be interpreted as described in RFC2119. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on January 26, 2016. 48 Copyright Notice 50 Copyright (c) 2015 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. Proposed Enhancement . . . . . . . . . . . . . . . . . . . . 3 67 3. Speficications . . . . . . . . . . . . . . . . . . . . . . . 4 68 3.1. Router Interface Parameters . . . . . . . . . . . . . . . 4 69 3.2. Advertising Network-to-Router metric in OSPFv2 . . . . . 4 70 3.3. Advertising Network-to-Router metric in OSPFv3 . . . . . 5 71 3.4. SPF Calculation . . . . . . . . . . . . . . . . . . . . . 5 72 3.5. Backward Compatibility . . . . . . . . . . . . . . . . . 5 73 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 74 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 75 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 76 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 78 7.2. Informative References . . . . . . . . . . . . . . . . . 7 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 81 1. Introduction 83 For a broadcast network, a Network-LSA is advertised to list all 84 routers on the network, and each router on the network includes a 85 link in its Router-LSA to describe its connection to the network. 86 The link in the Router-LSA includes a metric but the listed routers 87 in the Network LSA do not include a metric. This is based on the 88 assumption that from a particular router, all others on the same 89 network can be reached with the same metric. 91 With some broadcast networks, different routers can be reached with 92 different metrics. RFC 6845 extends the OSPF protocol with a hybrid 93 interface type for that kind of broadcast network, where no Network 94 LSA is advertised and Router-LSAs simply include p2p links to all 95 routers on the same network with individual metrics. Broadcast 96 capability is still utilized to optimize database synchronization and 97 adjacency maintenance. 99 That works well for broadcast networks where the metric between 100 different pair of routers are really independent. For example, VPLS 101 networks. 103 With certain types of broadcast networks, further optimization can be 104 made to reduce the size of the Router-LSAs and number of updates. 106 Consider a satellite radio network with fixed and mobile ground 107 terminals. All communication goes through the satellite. When the 108 mobile terminals move about, their communication capability may 109 change. When OSPF runs over the radio network (routers being or in 110 tandem with the terminals), RFC 6845 hybrid interface can be used, 111 but with the following drawbacks. 113 Consider that one terminal/router moves into an area where its 114 communication capability degrades significantly. Through the radio 115 control protocol, all other routers determine that the metric to this 116 particular router changed and they all need to update their Router- 117 LSAs accordingly. The router in question also determines that its 118 metric to reach all others also changed and it also needs to update 119 its Router-LSA. Consider that there could be many terminals and many 120 of them can be moving fast and frequently, the number/frequency of 121 updates of those large Router-LSAs could inhibit network scaling. 123 2. Proposed Enhancement 125 Notice that in the above scenario, when one terminal's communication 126 capability changes, its metric to all other terminals and the metric 127 from all other terminals to it will all change in a similar fashion. 128 Given this, the above problem can be easily addressed by breaking the 129 metric into two parts: the metric to the satellite and the metric 130 from the satellite. The metric from terminal R1 to R2 would be the 131 sum of the metric from R1 to the satellite and the metric from the 132 satellite to R2. 134 Now instead of using the RFC 6845 hybrid interface type, the network 135 is just treated as a regular broadcast network. A router on the 136 network no longer lists individual metrics to each neighbor in its 137 Router-LSA. Instead, each router advertises the metric from the 138 network to itself in addition to the normal metric for the network. 139 With the normal Router-to-Network and additional Network-to-Router 140 metrics advertised for each router, individual router-to-router 141 metric can be calculated. 143 With the proposed enhancement, the size of Router-LSA will be 144 significantly reduced. In addition, when a router's communication 145 capability changes, only that router needs to update its Router-LSA. 147 Note that while the example uses the satellite as the relay point at 148 the radio level (layer-2), at layer-3, the satellite does not 149 participate in packet forwarding. In fact, the satellite does not 150 need to be running any layer-3 protocol. Therefore for generality, 151 the metric is abstracted as to/from the "network" rather that 152 specifically to/from the "satellite". 154 3. Speficications 156 The following protocol specifications are added to or modified from 157 the base OSPF protocol. If an area contains one or more two-part 158 metric networks, then all routers in the area must support the 159 extensions specified herein. This is ensured by procedures described 160 in Section 3.5. 162 3.1. Router Interface Parameters 164 The "Router interface parameters" have the following additions: 166 o Two-part metric: TRUE if the interface connects to a multi-access 167 network that uses two-part metric. All routers connected to the 168 same network SHOULD have the same configuration for their 169 corresponding interfaces. 171 o Interface input cost: Link state metric from the two-part-metric 172 network to this router. Defaulted to "Interface output cost" but 173 not valid for normal networks using a single metric. May be 174 configured or dynamically adjusted to a value different from the 175 "Interface output cost". 177 3.2. Advertising Network-to-Router metric in OSPFv2 179 For OSPFv2, the Network-to-Router metric is encoded in an OSPF 180 Extended Link TLV Sub-TLV [ietf-ospf-lsa-extend], defined in this 181 document as the Network-to-Router Metric Sub-TLV. The type of the 182 Sub-TLV is TBD. The length of the Sub-TLV is 4 (for the value part 183 only). The value part of the Sub-TLV is defined as follows: 185 0 1 2 3 186 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 1 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 | MT | 0 | MT metric | 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 191 Multiple such Sub-TLVs can exist in a single OSPF Extended Link TLV, 192 one for each topology. The OSPF Extended Link TLV identifies the 193 transit link to the network, and is part of an OSPFv2 Extended-Link 194 Opaque LSA. The Sub-TLV MUST ONLY appear in Extended-Link TLVs for 195 Link Type 2 (link to transit network), and MUST be ignored if 196 received for other link types. 198 3.3. Advertising Network-to-Router metric in OSPFv3 200 For OSPFv3, the same Network-to-Router Metric Sub-TLV definition is 201 used, though it is part of the Router-Link TLV of E-Router-LSA [ietf- 202 ospf-ospfv3-lsa-extend]. Currently OSPFv3 Multi-Toplogy is not 203 defined so the only valid value for the MT field is 0 and only one 204 such Sub-TLV SHOULD be included in the Router-Link TLV. Received 205 Sub-TLVs with non-zero MT field MUST be ignored. 207 Similarly, the Sub-TLV MUST ONLY appear in Router-Link TLVs for Link 208 Type 2 (connection to a transit network) and MUST be ignored if 209 received for other link types. 211 3.4. SPF Calculation 213 During the first stage of shortest-path tree calculation for an area, 214 when a vertex V corresponding to a Network-LSA is added to the 215 shortest-path tree and its adjacent vertex W (joined by a link in V's 216 corresponding Network LSA), the cost from V to W, which is W's 217 network-to-router cost, is determined as follows: 219 o For OSPFv2, if vertex W has a corresponding Extended-Link Opaque 220 LSA with an Extended Link TLV for the link from W to V, and the 221 Extended Link TLV has a Network-to-Router Metric Sub-TLV for the 222 corresponding topology, then the cost from V to W is the metric in 223 the Sub-TLV. Otherwise, the cost is 0. 225 o For OSPFv3, if vertex W has a corresponding E-Router-LSA with a 226 Router-Link TLV for the link from W to V, and the Router-Link TLV 227 has a Network-to-Router Metric Sub-TLV, then the cost from V to W 228 is the metric in the Sub-TLV. If not, the cost is 0. 230 3.5. Backward Compatibility 232 Due to the change of procedures in the SPF calculation, all routers 233 in an area that includes one or more two-part metric networks must 234 support the changes specified in this document. To ensure that, if 235 an area is provisioned to support two-part metric networks, all 236 routers supporting this capability must advertise a Router 237 Information (RI) LSA with a Router Functional Capabilities TLV [acee- 238 ospf-rfc4970bis] that includes the following Router Functional 239 Capability Bit: 241 Bit Capabilities 243 0 OSPF Two-part Metric [TPM] 245 Upon detecting the presence of a reachable Router-LSA without a 246 companion RI LSA that has the bit set, all routers MUST disable the 247 two-part metric functionalities and take the following actions: 249 o If this router currently advertises network-to-router costs, 250 remove the Network-to-Router Metric Sub-TLVs. This may lead to 251 removal of parent TLVs and even withdrawal of the parent LSAs. 253 o Recalculate routes w/o considering any network-to-router costs. 255 4. IANA Considerations 257 This document requests IANA to assigna a new bit in the Router 258 Functional Capabilities TLV to indicate the capability of supporting 259 two-part metric, a new Sub-TLV in the OSPF Extended-Link TLV Sub-TLV 260 Registry, and a new Sub-TLV in the The OSPFv3 Extend-LSA Sub-TLV 261 registry. 263 5. Security Considerations 265 This document does not introduce new security risks. 267 6. Acknowledgements 269 The authors would like to thank Abhay Roy, Hannes Gredler, Peter 270 Psenak and Eric Wu for their comments and suggestions. 272 7. References 274 7.1. Normative References 276 [I-D.acee-ospf-rfc4970bis] 277 Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S. 278 Shaffer, "Extensions to OSPF for Advertising Optional 279 Router Capabilities", draft-acee-ospf-rfc4970bis-00 (work 280 in progress), July 2014. 282 [I-D.ietf-ospf-lsa-extend] 283 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 284 Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, 285 "OSPFv2 LSA Extendibility", draft-ietf-ospf-lsa-extend-00 286 (work in progress), August 2014. 288 [I-D.ietf-ospf-ospfv3-lsa-extend] 289 Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 290 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06 291 (work in progress), February 2015. 293 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 294 Requirement Levels", BCP 14, RFC 2119, 295 DOI 10.17487/RFC2119, March 1997, 296 . 298 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 299 DOI 10.17487/RFC2328, April 1998, 300 . 302 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 303 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 304 RFC 4915, DOI 10.17487/RFC4915, June 2007, 305 . 307 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 308 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 309 . 311 [RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. 312 Yeung, "OSPF Link-Local Signaling", RFC 5613, 313 DOI 10.17487/RFC5613, August 2009, 314 . 316 7.2. Informative References 318 [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast 319 and Point-to-Multipoint Interface Type", RFC 6845, 320 DOI 10.17487/RFC6845, January 2013, 321 . 323 Authors' Addresses 324 Jeffrey Zhang 325 Juniper Networks, Inc. 326 10 Technology Park Drive 327 Westford, MA 01886 329 EMail: zzhang@juniper.net 331 Lili Wang 332 Juniper Networks, Inc. 333 10 Technology Park Drive 334 Westford, MA 01886 336 EMail: liliw@juniper.net 338 Acee Lindem 339 Cisco Systems 340 301 Midenhall Way 341 Cary, NC 27513 343 EMail: acee@cisco.com 345 David Dubois 346 General Dynamics C4S 347 400 John Quincy Adams Road 348 Taunton, MA 02780 350 EMail: dave.dubois@gdc4s.com 352 Vibhor Julka 353 L3 Communications, Linkabit 354 9890 Towne Centre Drive 355 San Diego, CA 92121 357 EMail: vibhor.julka@l-3Com.com 359 Tom McMillan 360 L3 Communications, Linkabit 361 9890 Towne Centre Drive 362 San Diego, CA 92121 364 EMail: tom.mcmillan@l-3com.com