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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: July 24, 2015 Cisco Systems 7 D. Dubois 8 General Dynamics C4S 9 V. Julka 10 T. McMillan 11 L3 Communications, Linkabit 12 January 20, 2015 14 OSPF Two-part Metric 15 draft-ietf-ospf-two-part-metric-00.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 July 24, 2015. 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 80 1. Introduction 82 For a broadcast network, a Network-LSA is advertised to list all 83 routers on the network, and each router on the network includes a 84 link in its Router-LSA to describe its connection to the network. 85 The link in the Router-LSA includes a metric but the listed routers 86 in the Network LSA do not include a metric. This is based on the 87 assumption that from a particular router, all others on the same 88 network can be reached with the same metric. 90 With some broadcast networks, different routers can be reached with 91 different metrics. RFC 6845 extends the OSPF protocol with a hybrid 92 interface type for that kind of broadcast network, where no Network 93 LSA is advertised and Router-LSAs simply include p2p links to all 94 routers on the same network with individual metrics. Broadcast 95 capability is still utilized to optimize database synchronization and 96 adjacency maintenance. 98 That works well for broadcast networks where the metric between 99 different pair of routers are really independent. For example, VPLS 100 networks. 102 With certain types of broadcast networks, further optimization can be 103 made to reduce the size of the Router-LSAs and number of updates. 105 Consider a satellite radio network with fixed and mobile ground 106 terminals. All communication goes through the satellite. When the 107 mobile terminals move about, their communication capability may 108 change. When OSPF runs over the radio network (routers being or in 109 tandem with the terminals), RFC 6845 hybrid interface can be used, 110 but with the following drawbacks. 112 Consider that one terminal/router moves into an area where its 113 communication capability degrades significantly. Through the radio 114 control protocol, all other routers determine that the metric to this 115 particular router changed and they all need to update their Router- 116 LSAs accordingly. The router in question also determines that its 117 metric to reach all others also changed and it also needs to update 118 its Router-LSA. Consider that there could be many terminals and many 119 of them can be moving fast and frequently, the number/frequency of 120 updates of those large Router-LSAs could inhibit network scaling. 122 2. Proposed Enhancement 124 Notice that in the above scenario, when one terminal's communication 125 capability changes, its metric to all other terminals and the metric 126 from all other terminals to it will all change in a similar fashion. 127 Given this, the above problem can be easily addressed by breaking the 128 metric into two parts: the metric to the satellite and the metric 129 from the satellite. The metric from terminal R1 to R2 would be the 130 sum of the metric from R1 to the satellite and the metric from the 131 satellite to R2. 133 Now instead of using the RFC 6845 hybrid interface type, the network 134 is just treated as a regular broadcast network. A router on the 135 network no longer lists individual metrics to each neighbor in its 136 Router-LSA. Instead, each router advertises the metric from the 137 network to itself in addition to the normal metric for the network. 138 With the normal Router-to-Network and additional Network-to-Router 139 metrics advertised for each router, individual router-to-router 140 metric can be calculated. 142 With the proposed enhancement, the size of Router-LSA will be 143 significantly reduced. In addition, when a router's communication 144 capability changes, only that router needs to update its Router-LSA. 146 Note that while the example uses the satellite as the relay point at 147 the radio level (layer-2), at layer-3, the satellite does not 148 participate in packet forwarding. In fact, the satellite does not 149 need to be running any layer-3 protocol. Therefore for generality, 150 the metric is abstracted as to/from the "network" rather that 151 specifically to/from the "satellite". 153 3. Speficications 155 The following protocol specifications are added to or modified from 156 the base OSPF protocol. If an area contains one or more two-part 157 metric networks, then all routers in the area must support the 158 extensions specified herein. This is ensured by procedures described 159 in Section 3.5. 161 3.1. Router Interface Parameters 163 The "Router interface parameters" have the following additions: 165 o Two-part metric: TRUE if the interface connects to a multi-access 166 network that uses two-part metric. All routers connected to the 167 same network SHOULD have the same configuration for their 168 corresponding interfaces. 170 o Interface input cost: Link state metric from the two-part-metric 171 network to this router. Defaulted to "Interface output cost" but 172 not valid for normal networks using a single metric. May be 173 configured or dynamically adjusted to a value different from the 174 "Interface output cost". 176 3.2. Advertising Network-to-Router metric in OSPFv2 178 For OSPFv2, the Network-to-Router metric is encoded in an OSPF 179 Extended Link TLV Sub-TLV [ietf-ospf-lsa-extend], defined in this 180 document as the Network-to-Router Metric Sub-TLV. The type of the 181 Sub-TLV is TBD. The length of the Sub-TLV is 4 (for the value part 182 only). The value part of the Sub-TLV is defined as follows: 184 0 1 2 3 185 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 1 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | MT | 0 | MT metric | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 Multiple such Sub-TLVs can exist in a single OSPF Extended Link TLV, 191 one for each topology. The OSPF Extended Link TLV identifies the 192 transit link to the network, and is part of an OSPFv2 Extended-Link 193 Opaque LSA. The Sub-TLV MUST ONLY appear in Extended-Link TLVs for 194 Link Type 2 (link to transit network), and MUST be ignored if 195 received for other link types. 197 3.3. Advertising Network-to-Router metric in OSPFv3 199 For OSPFv3, the same Network-to-Router Metric Sub-TLV definition is 200 used, though it is part of the Router-Link TLV of E-Router-LSA [ietf- 201 ospf-ospfv3-lsa-extend]. Currently OSPFv3 Multi-Toplogy is not 202 defined so the only valid value for the MT field is 0 and only one 203 such Sub-TLV SHOULD be included in the Router-Link TLV. Received 204 Sub-TLVs with non-zero MT field MUST be ignored. 206 Similarly, the Sub-TLV MUST ONLY appear in Router-Link TLVs for Link 207 Type 2 (connection to a transit network) and MUST be ignored if 208 received for other link types. 210 3.4. SPF Calculation 212 During the first stage of shortest-path tree calculation for an area, 213 when a vertex V corresponding to a Network-LSA is added to the 214 shortest-path tree and its adjacent vertex W (joined by a link in V's 215 corresponding Network LSA), the cost from V to W, which is W's 216 network-to-router cost, is determined as follows: 218 o For OSPFv2, if vertex W has a corresponding Extended-Link Opaque 219 LSA with an Extended Link TLV for the link from W to V, and the 220 Extended Link TLV has a Network-to-Router Metric Sub-TLV for the 221 corresponding topology, then the cost from V to W is the metric in 222 the Sub-TLV. Otherwise, the cost is 0. 224 o For OSPFv3, if vertex W has a corresponding E-Router-LSA with a 225 Router-Link TLV for the link from W to V, and the Router-Link TLV 226 has a Network-to-Router Metric Sub-TLV, then the cost from V to W 227 is the metric in the Sub-TLV. If not, the cost is 0. 229 3.5. Backward Compatibility 231 Due to the change of procedures in the SPF calculation, all routers 232 in an area that includes one or more two-part metric networks must 233 support the changes specified in this document. To ensure that, if 234 an area is provisioned to support two-part metric networks, all 235 routers supporting this capability must advertise a Router 236 Information (RI) LSA with a Router Functional Capabilities TLV [acee- 237 ospf-rfc4970bis] that includes the following Router Functional 238 Capability Bit: 240 Bit Capabilities 242 0 OSPF Two-part Metric [TPM] 244 Upon detecting the presence of a reachable Router-LSA without a 245 companion RI LSA that has the bit set, all routers MUST disable the 246 two-part metric functionalities and take the following actions: 248 o If this router currently advertises network-to-router costs, 249 remove the Network-to-Router Metric Sub-TLVs. This may lead to 250 removal of parent TLVs and even withdrawal of the parent LSAs. 252 o Recalculate routes w/o considering any network-to-router costs. 254 4. IANA Considerations 256 This document requests IANA to assigna a new bit in the Router 257 Functional Capabilities TLV to indicate the capability of supporting 258 two-part metric, a new Sub-TLV in the OSPF Extended-Link TLV Sub-TLV 259 Registry, and a new Sub-TLV in the The OSPFv3 Extend-LSA Sub-TLV 260 registry. 262 5. Security Considerations 264 This document does not introduce new security risks. 266 6. Acknowledgements 268 The authors would like to thank Abhay Roy, Hannes Gredler, Peter 269 Psenak and Eric Wu for their comments and suggestions. 271 7. References 273 7.1. Normative References 275 [I-D.acee-ospf-rfc4970bis] 276 Lindem, A., Shen, N., Vasseur, J., Aggarwal, R., and S. 277 Shaffer, "Extensions to OSPF for Advertising Optional 278 Router Capabilities", draft-acee-ospf-rfc4970bis-00 (work 279 in progress), July 2014. 281 [I-D.ietf-ospf-lsa-extend] 282 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 283 Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, 284 "OSPFv2 LSA Extendibility", draft-ietf-ospf-lsa-extend-00 285 (work in progress), August 2014. 287 [I-D.ietf-ospf-ospfv3-lsa-extend] 288 Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 289 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-05 290 (work in progress), November 2014. 292 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 293 Requirement Levels", BCP 14, RFC 2119, March 1997. 295 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 297 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 298 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 299 4915, June 2007. 301 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 302 for IPv6", RFC 5340, July 2008. 304 [RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. 305 Yeung, "OSPF Link-Local Signaling", RFC 5613, August 2009. 307 7.2. Informative References 309 [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast 310 and Point-to-Multipoint Interface Type", RFC 6845, January 311 2013. 313 Authors' Addresses 315 Jeffrey Zhang 316 Juniper Networks, Inc. 317 10 Technology Park Drive 318 Westford, MA 01886 320 EMail: zzhang@juniper.net 322 Lili Wang 323 Juniper Networks, Inc. 324 10 Technology Park Drive 325 Westford, MA 01886 327 EMail: liliw@juniper.net 328 Acee Lindem 329 Cisco Systems 330 301 Midenhall Way 331 Cary, NC 27513 333 EMail: acee@cisco.com 335 David Dubois 336 General Dynamics C4S 337 400 John Quincy Adams Road 338 Taunton, MA 02780 340 EMail: dave.dubois@gdc4s.com 342 Vibhor Julka 343 L3 Communications, Linkabit 344 9890 Towne Centre Drive 345 San Diego, CA 92121 347 EMail: vibhor.julka@l-3Com.com 349 Tom McMillan 350 L3 Communications, Linkabit 351 9890 Towne Centre Drive 352 San Diego, CA 92121 354 EMail: tom.mcmillan@l-3com.com