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Mirtorabi 6 Cisco Systems 7 April 18, 2010 9 OSPF Transport Instance Extensions 10 draft-ietf-ospf-transport-instance-04.txt 12 Abstract 14 OSPFv2 and OSPFv3 include a reliable flooding mechanism to 15 disseminate routing topology and Traffic Engineering (TE) information 16 within a routing domain. Given the effectiveness of these 17 mechanisms, it is convenient to envision using the same mechanism for 18 dissemination of other types of information within the domain. 19 However, burdening OSPF with this additional information will impact 20 intra-domain routing convergence and possibly jeopardize the 21 stability of the OSPF routing domain. This document presents 22 mechanism to relegate this ancillary information to a separate OSPF 23 instance and minimize the impact. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on October 20, 2010. 42 Copyright Notice 44 Copyright (c) 2010 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 This document may contain material from IETF Documents or IETF 58 Contributions published or made publicly available before November 59 10, 2008. The person(s) controlling the copyright in some of this 60 material may not have granted the IETF Trust the right to allow 61 modifications of such material outside the IETF Standards Process. 62 Without obtaining an adequate license from the person(s) controlling 63 the copyright in such materials, this document may not be modified 64 outside the IETF Standards Process, and derivative works of it may 65 not be created outside the IETF Standards Process, except to format 66 it for publication as an RFC or to translate it into languages other 67 than English. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 73 2. OSPF Transport Instance . . . . . . . . . . . . . . . . . . . 5 74 2.1. OSPFv2 Transport Instance Packets Differentiation . . . . 5 75 2.2. OSPFv3 Transport Instance Packets Differentiation . . . . 5 76 2.3. Instance Relationship to Normal OSPF Instances . . . . . . 5 77 2.3.1. Ships in the Night Relationship to Normal OSPF 78 Instances . . . . . . . . . . . . . . . . . . . . . . 6 79 2.3.2. Tighter Coupling with Normal OSPF Instances . . . . . 6 80 2.4. Network Prioritization . . . . . . . . . . . . . . . . . . 6 81 2.5. OSPF Transport Instance Omission of Routing Calculation . 6 82 2.6. Non-routing Instance Separation . . . . . . . . . . . . . 7 83 2.7. Non-Routing Sparse Topologies . . . . . . . . . . . . . . 7 84 2.7.1. Remote OSPF Neighbor . . . . . . . . . . . . . . . . . 8 85 3. OSPF Transport Instance Information Encoding . . . . . . . . . 9 86 3.1. OSPFv2 Transport Instance Information Encoding . . . . . . 9 87 3.2. OSPFv3 Transport Instance Information Encoding . . . . . . 9 88 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 89 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 90 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 91 6.1. Normative References . . . . . . . . . . . . . . . . . . . 12 92 6.2. Informative References . . . . . . . . . . . . . . . . . . 12 93 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 96 1. Introduction 98 OSPFv2 [OSPFV2] and OSPFv3 [OSPFV3] include a reliable flooding 99 mechanism to disseminate routing topology and Traffic Engineering 100 (TE) information within a routing domain. Given the effectiveness of 101 these mechanisms, it is convenient to envision using the same 102 mechanism for dissemination of other types of information within the 103 domain. However, burdening OSPF with this additional information 104 will impact intra-domain routing convergence and possibly jeopardize 105 the stability of the OSPF routing domain. This document presents 106 mechanism to relegate this ancillary information to a separate OSPF 107 instance and minimize the impact. 109 1.1. Requirements notation 111 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 112 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 113 document are to be interpreted as described in [RFC-KEYWORDS]. 115 2. OSPF Transport Instance 117 In order to isolate the overhead of flooding non-routing information, 118 its flooding will be relegated to a separate protocol instance. This 119 instance should be given lower priority when contending for router 120 resources including processing, backplane bandwidth, and line card 121 bandwidth. How that is realized is an implementation issue and is 122 beyond the scope of this document. 124 Throughout the document, non-routing refers to routing information 125 that is not used for IP or IPv6 routing calculations. The OSPF 126 transport instance is ideally suited for dissemination of routing 127 information for other protocols and layers. 129 2.1. OSPFv2 Transport Instance Packets Differentiation 131 OSPFv2 currently doesn't offer a mechanism to differentiate Transport 132 instance packets from normal instance packets sent and received on 133 the same interface. However, the [MULTI-INST] provides the necessary 134 packet encoding to support multiple OSPF protocol instances. 136 2.2. OSPFv3 Transport Instance Packets Differentiation 138 Fortunately, OSPFv3 already supports separate instances within the 139 packet encodings. The existing OSPFv3 packet header instance ID 140 field will be used to differentiate packets received on the same link 141 (refer to section 2.4 in [OSPFV3]). 143 2.3. Instance Relationship to Normal OSPF Instances 145 There are basically two alternatives for the relationship between a 146 normal OSPF instance and a Transport Instance. In both cases, we 147 must guarantee that any information we've received is treated as 148 valid if and only if the router sending it is reachable. We'll refer 149 to this as the "condition of reachability" in this document. 151 1. Ships in the Night - The Transport Instance has no relationship 152 or dependency on any other OSPF instance. 154 2. Child Instance - The Transport Instance has a child-parent 155 relationship with a normal OSPF instance and is dependent on this 156 for topology information and assuring the "condition of 157 reachability". 159 2.3.1. Ships in the Night Relationship to Normal OSPF Instances 161 In this mode, the Transport Instance is not dependent on any other 162 OSPF instance. It does, however, have much of the overhead as 163 topology information must be advertised to satisfy the condition of 164 reachability. 166 Prefix information does this need to be advertised. This implies 167 that for OSPFv2, only router-LSAs, network-LSAs, and type 4 summary- 168 LSAs need to be advertised. In the router-LSAs, the stub (type 3) 169 links may be suppressed. For OSPFv3, this implies that router-LSAs, 170 Network-LSAs, and inter-area-router-LSAs must be advertised. 172 2.3.2. Tighter Coupling with Normal OSPF Instances 174 Further optimization and coupling between the transport instance and 175 a normal OSPF instance are beyond the scope of this document. This 176 is an area for future study. 178 2.4. Network Prioritization 180 While OSPFv2 (section 4.3 in [OSPFV2]) are normally sent with IP 181 precedence Internetwork Control, any packets sent by a transport 182 instance will be sent with IP precedence Flash (B'011'). This is 183 only appropriate given that this is a pretty flashy mechanism. 185 Similarly, OSPFv3 transport instance packets will be sent with the 186 traffic class mapped to flash (B'011') as specified in ([OSPFV3]. 188 By setting the IP/IPv6 precedence differently for OSPF transport 189 instance packets, normal OSPF routing instances can be given priority 190 during both packet transmission and reception. In fact, some router 191 implementations map the IP precedence directly to their internal 192 packet priority. However, implementation issues are beyond the scope 193 of this document. 195 2.5. OSPF Transport Instance Omission of Routing Calculation 197 Since the whole point of the transport instance is to separate the 198 routing and non-routing processing and fate sharing, a transport 199 instance SHOULD NOT install any routes. OSPF routers SHOULD NOT 200 advertise any transport instance LSAs containing IP or IPv6 prefixes 201 and OSPF routers receiving LSAs advertising prefixes SHOULD ignore 202 them. This implies that an OSPFv2 transport instance Link State 203 Database should not include any Summary-LSAs (type 3) , AS-External- 204 LSAs (type 5), or NSSA-LSAs (type 7) and the Router-LSAs should not 205 include any stub (type 3) links. An OSPFv3 transport instance Link 206 State database should not include any Inter-Area-Prefix-LSAs (type 207 0x2003), AS-External-LSAs (0x4005), NSSA-LSAs (type 0x2007), or 208 Intra-Area-Prefix-LSAs (type 0x2009). If they are erroneously 209 advertised, they MUST be ignored by OSPF routers supporting this 210 specification. 212 2.6. Non-routing Instance Separation 214 It has been suggested that an implementation could obtain the same 215 level of separation between IP routing information and non-routing 216 information in a single instance with slight modifications to the 217 OSPF protocol. The authors refute this contention for the following 218 reasons: 220 o Adding internal and external mechanisms to prioritize routing 221 information over non-routing information are much more complex 222 than simply relegating the non-routing information to a separate 223 instance as proposed in this specification. 225 o The instance boundary offers much better separation for allocation 226 of finite resources such as buffers, memory, processor cores, 227 sockets, and bandwidth. 229 o The instance boundary decreases the level of fate sharing for 230 failures. Each instance may be implemented as a separate process 231 or task. 233 o With non-routing information, many times not every router in the 234 OSPF routing domain requires knowledge of every piece of routing 235 information. In these cases, groups of routers which need to 236 share information can be segregated into sparse topologies greatly 237 reducing the amount of non-routing information any single router 238 needs to maintain. 240 2.7. Non-Routing Sparse Topologies 242 With non-routing information, many times not every router in the OSPF 243 routing domain requires knowledge of every piece of routing 244 information. In these cases, groups of routers which need to share 245 information can be segregated into sparse topologies. This will 246 greatly reduce the amount of information any single router needs to 247 maintain with the core routers possibly not requiring any non-routing 248 information at all. 250 With normal OSPF, every router in an OSPF area must have every piece 251 of topological and IP or IPv6 prefix routing information. With non- 252 routing information, only the routers needing to share a set of 253 information need be part of the corresponding sparse topology. For 254 directly attached routers, one only needs to configure the desired 255 topologies on the interfaces with routers requiring the non-routing 256 information. When the routers making up the sparse topology are not 257 part of a uniconnected graph, two alternatives exist. The first 258 alternative is configure tunnels to form a fully connected graph 259 including only those routers in the sparse topology. The second 260 alternative is use remote neighbors as described in Section 2.7.1. 262 2.7.1. Remote OSPF Neighbor 264 With sparse topologies, OSPF routers sharing non-routing information 265 may not be directly connected. OSPF adjacencies with remote 266 neighbors are formed exactly as they are with regular OSPF neighbors. 267 The main difference is that a remote OSPF neighbor's address is 268 configured and IP routing is used to deliver packet to the remote 269 neighbor. Other salient feature of remote neighbor include: 271 o All OSPF packets are addressed to the remote neighbor's configured 272 IP address. 274 o The adjacency is represented in the router Router-LSA as a router 275 (type-1) link with the link data set to the remote neighbor 276 address. 278 o Similar to NBMA networks, a poll-interval is configured to 279 determine if the remote neighbor is reachable. This value is 280 normally much higher than the hello interval. 282 3. OSPF Transport Instance Information Encoding 284 The format of the TLVs within the body of an LSA containing non- 285 routing information is the same as the format used by the Traffic 286 Engineering Extensions to OSPF [TE]. The LSA payload consists of one 287 or more nested Type/Length/Value (TLV) triplets. The format of each 288 TLV is: 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Type | Length | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | Value... | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 TLV Format 300 However, each unique application using the mechanisms defined in this 301 document will have it's own unique ID. Whether to encode this ID as 302 the top-level TLV or make it part of the OSPF LSA ID is open for 303 debate. 305 The specific TLVs and sub-TLVs relating to a given application and 306 the corresponding IANA considerations MUST for standard applications 307 MUST be specified in the document corresponding to that application. 309 3.1. OSPFv2 Transport Instance Information Encoding 311 Application specific information will be flooded in opaque LSAs as 312 specified in [OPAQUE]. 314 3.2. OSPFv3 Transport Instance Information Encoding 316 Application specific information will be flooded in separate LSAs 317 with separate function codes. Refer to section A.4.2.1 of [OSPFV3] 318 for information on the LS Type encoding in OSPFv3. 320 4. Security Considerations 322 The security considerations for the Transport Instance will not be 323 different for those for OSPFv2 [OSPFV2] and OSPFv3 [OSPFV3]. 325 5. IANA Considerations 327 No new IANA assignments are required for this draft. 329 6. References 331 6.1. Normative References 333 [MULTI-INST] 334 Lindem, A., Mirtorabi, S., and A. Roy, "OSPF Multi- 335 Instance Extensions", 336 draft-ietf-ospf-multi-instance-02.txt (work in progress). 338 [OPAQUE] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The 339 OSPF Opaque LSA Option", RFC 5250, July 2008. 341 [OSPFV2] Moy, J., "OSPF Version 2", RFC 2328, April 1998. 343 [OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 344 for IPv6", RFC 5340, July 2008. 346 [RFC-KEYWORDS] 347 Bradner, S., "Key words for use in RFC's to Indicate 348 Requirement Levels", RFC 2119, March 1997. 350 [TE] Katz, D., Yeung, D., and K. Kompella, "Traffic Engineering 351 Extensions to OSPF", RFC 3630, September 2003. 353 6.2. Informative References 355 [ISIS-GEN-APP] 356 Ginsberg, L., Previdi, S., and M. Shand, "Advertising 357 Generic Information in IS-IS", 358 draft-ietf-isis-genapp-02,txt (work in progress). 360 Appendix A. Acknowledgments 362 The RFC text was produced using Marshall Rose's xml2rfc tool. 364 Although very different mechanisms are utilized, the concept of using 365 a separate instance to advertise non-routing information in an IGP 366 was first introduced in "Advertising Generic Information in IS-IS" 367 [ISIS-GEN-APP]. 369 Thanks to Jonathan Sadler for comments on the document. 371 Authors' Addresses 373 Acee Lindem 374 Ericsson 375 102 Carric Bend Court 376 Cary, NC 27519 377 USA 379 Email: acee.lindem@ericsson.com 381 Abhay Roy 382 Cisco Systems 383 225 West Tasman Drive 384 San Jose, CA 95134 385 USA 387 Email: akr@cisco.com 389 Sina Mirtorabi 390 Cisco Systems 391 3 West Plumeria Drive 392 San Jose, CA 95134 393 USA 395 Email: sina@cisco.com