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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-28) exists of draft-ietf-idr-bgp-optimal-route-reflection-16 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 OSPF K. Patel 3 Internet-Draft Arrcus 4 Updates: 2328 (if approved) P. Pillay-Esnault 5 Intended status: Standards Track Huawei Technologies 6 Expires: February 28, 2019 M. Bhardwaj 7 S. Bayraktar 8 Cisco Systems 9 August 27, 2018 11 H-bit Support for OSPFv2 12 draft-ietf-ospf-ospfv2-hbit-06 14 Abstract 16 OSPFv3 defines an option bit for router-LSAs known as the R-bit in 17 RFC5340. If the R-bit is clear, an OSPFv3 router can participate in 18 OSPF topology flooding, however it will not be used as a transit 19 router. In such cases, other routers in the OSPFv3 routing domain 20 only install routes to allow local traffic delivery. This document 21 defines the H-bit functionality to prevent other OSPFv2 routers from 22 using the router for transit traffic in OSPFv2 routing domains as 23 described in RFC 2328. This document updates RFC 2328. 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 https://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 February 28, 2019. 42 Copyright Notice 44 Copyright (c) 2018 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 (https://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 . . . . . . . . . . . . . . . . . . . . . . . . 2 72 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 73 3. H-bit Support . . . . . . . . . . . . . . . . . . . . . . . . 3 74 4. SPF Modifications . . . . . . . . . . . . . . . . . . . . . . 5 75 5. Auto Discovery and Backward Compatibility . . . . . . . . . . 5 76 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics . . . . . 6 77 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 78 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 79 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 80 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 81 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 82 10.2. Informative References . . . . . . . . . . . . . . . . . 7 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 85 1. Introduction 87 OSPFv3 [RFC5340] defines an option bit for router-LSAs known as the 88 R-bit. If the R-bit is clear, an OSPFv3 router can participate in 89 OSPFv3 topology flooding without acting as a transit router. In such 90 cases, other routers in the OSPFv3 routing domain only install routes 91 used for local traffic. 93 This functionality is particularly useful for BGP Route Reflectors, 94 known as virtual Route Reflectors (vRRs), that are not in the 95 forwarding path but are in central locations such as data centers. 96 Such Route Reflectors typically are used for route distribution and 97 are not capable of forwarding transit traffic. However, they need to 98 learn the OSPF topology for: 100 1. SPF computation for Optimal Route Reflection functionality as 101 defined in [I-D.ietf-idr-bgp-optimal-route-reflection] 103 2. Reachability resolution for its Route Reflector Clients. 105 This document defines the R-bit functionality equivalent for OSPFv2 106 defined in [RFC2328] by introducing a new router-LSA bit known as the 107 "H-bit". This document updates appendix A.4.2 of RFC 2328. 109 2. Requirements Language 111 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 112 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 113 "OPTIONAL" in this document are to be interpreted as described in BCP 114 14 [RFC2119] [RFC8174] when, and only when, they appear in all 115 capitals, as shown here. 117 3. H-bit Support 119 This document defines a new router-LSA bit known as the Host Bit or 120 the H-bit. An OSPFv2 router advertising a router-LSA with the H-bit 121 set indicates to other OSPFv2 routers in the area supporting the 122 functionality that it MUST NOT be used as a transit router. The bit 123 value usage of the H-bit is reversed from the R-bit defined in OSPFv3 124 [RFC5340] to support backward compatibility. The modified OSPFv2 125 router-LSA format is: 127 0 1 2 3 128 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 1 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 | LS age | Options | 1 | 131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 | Link State ID | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | Advertising Router | 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | LS sequence number | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | LS checksum | length | 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 |H|0|0|N|W|V|E|B| 0 | # links | 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 | Link ID | 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 | Link Data | 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 | Type | # TOS | metric | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | ... | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | TOS | 0 | TOS metric | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Link ID | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | Link Data | 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | ... | 158 bit H 159 When set, an OSPFv2 router is a non-transit router and is 160 incapable of forwarding transit traffic. 162 When the H-bit is set, an OSPFv2 router is a non-transit router and 163 should not be used to forward transit traffic. In this mode, the 164 other OSPFv2 routers in the area SHOULD NOT use the originating 165 OSPFv2 router for transit traffic, but MAY use the OSPFv2 router for 166 local traffic destined to that OSPFv2 router. 168 An OSPFv2 router originating a router-LSA with the H-bit set SHOULD 169 advertise all its non-local router links with a link cost of 170 MaxLinkMetric as defined in Section 3 of [RFC6987]. This is to 171 increase the applicability of the H-bit to partial deployments where 172 it is the responsibility of the operator to ensure that OSPFv2 173 routers not supporting the H-bit do not install routes causing 174 routing loops. 176 When the H-bit is set, IPv4 prefixes associated with local interfaces 177 in other areas MAY be advertised in summary LSAs. Non-local IPv4 178 prefixes, e.g., those advertised by other routers and installed 179 during the SPF computation, MAY be advertised in summary-LSAs if 180 configured by policy. Likewise, when the H-bit is set, only IPv4 181 prefixes associated with local interfaces MAY be advertised in AS- 182 external LSAs. Non-local IPv4 prefixes, e.g., those exported from 183 other routing protocols, MUST NOT be advertised in AS-external-LSAs. 184 Finally, when the H-bit is set, an Area Border Router (ABR) MUST 185 advertise a consistent H-bit setting in its self-originated router- 186 LSAs for all attached areas. 188 4. SPF Modifications 190 The SPF calculation described in section 16.1 [RFC2328] will be 191 modified to ensure that the routers originating router-LSAs with the 192 H-bit set will not be used for transit traffic. Step 2 is modified 193 as follows: 195 2) Call the vertex just added to the 196 tree vertex V. Examine the LSA 197 associated with vertex V. This is 198 a lookup in the Area A's link state 199 database based on the Vertex ID. If 200 this is a router-LSA, and the H-bit 201 of the router-LSA is set, and 202 vertex V is not the root, then the 203 router should not be used for transit 204 and step (3) should be executed 205 immediately. If this is a router-LSA, 206 and bit V of the router-LSA (see 207 Section A.4.2) is set, set Area A's 208 TransitCapability to TRUE. In any case, 209 each link described by the LSA gives 210 the cost to an adjacent vertex. For 211 each described link, (say it joins 212 vertex V to vertex W): 214 5. Auto Discovery and Backward Compatibility 216 To avoid the possibility of any routing loops due to partial 217 deployment, this document defines a OSPF Router-Information LSA 218 functional capability bit known as the Host Support capability. 220 Auto Discovery via announcement of the Host Support Functional 221 Capability ensures that the H-bit functionality and its associated 222 SPF changes SHOULD only take effect if all the routers in a given 223 OSPF area support this functionality. 225 Implementations are encouraged to provide a configuration parameter 226 to manually override enforcement of the H-bit functionality in 227 partial deployments where the topology guarantees that OSPFv2 routers 228 not supporting the H-bit do not compute routes resulting in routing 229 loops. More precisely, the advertisement of MaxLinkMetric for the 230 router's non-local links will prevent OSPFv2 routers not supporting 231 the H-bit from attempting to use it for transit traffic. 233 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics 235 When calculating the path to an OSPF AS-External-LSA or NSSA-LSA with 236 a Type-2 metric, the advertised Type-2 metric is taken as more 237 significant than the OSPF intra-area or inter-area path. Hence, 238 advertising the links with MaxLinkMetric as specified in [RFC6987] 239 does not discourage transit traffic when calculating AS external or 240 NSSA routes. Consequently, OSPF routers implementing [RFC6987] or 241 this specification should advertise a Type-2 metric of LSInfinity for 242 any self-originated AS-External-LSAs or NSSA-LSAs in situations when 243 the OSPF router is acting as a stub router [RFC6987] or implementing 244 this specification. 246 7. IANA Considerations 248 IANA is requested to create the OSPF Router-LSA bit registry with the 249 following assignments: 251 Value Description Reference 252 0x01 Area Border Router (B-bit) [RFC2328] 253 0x02 AS Boundary Router (E-bit) [RFC2328] 254 0x04 Virtual Link Endpoint (V-bit) [RFC2328] 255 0x08 Historic (W-bit) [RFC1584] 256 0x10 Unconditional NSSA Translator (Nt-bit) [RFC3101] 257 0x20 Unassigned 258 0x40 Unassigned 259 0x80 Host (H-bit) This Document 261 This document also defines a new Router Functional Capability 262 [RFC7770] known as the Host Support Functional Capability. This 263 document requests IANA to allocate the value of this capability from 264 the Router Functional Capability Bits TLV. 266 8. Security Considerations 268 This document introduces no new security considerations beyond those 269 already specified in [RFC6987], [RFC2328], and [RFC5340]. 271 9. Acknowledgements 273 The authors would like to acknowledge Hasmit Grover for discovery of 274 the limitation in [RFC6987], Acee Lindem, Abhay Roy, David Ward, 275 Burjiz Pithawala and Michael Barnes for their comments. 277 10. References 279 10.1. Normative References 281 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 282 Requirement Levels", BCP 14, RFC 2119, 283 DOI 10.17487/RFC2119, March 1997, 284 . 286 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 287 DOI 10.17487/RFC2328, April 1998, 288 . 290 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 291 RFC 3101, DOI 10.17487/RFC3101, January 2003, 292 . 294 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 295 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 296 . 298 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 299 S. Shaffer, "Extensions to OSPF for Advertising Optional 300 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 301 February 2016, . 303 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 304 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 305 May 2017, . 307 10.2. Informative References 309 [I-D.ietf-idr-bgp-optimal-route-reflection] 310 Raszuk, R., Cassar, C., Aman, E., Decraene, B., and K. 311 Wang, "BGP Optimal Route Reflection (BGP-ORR)", draft- 312 ietf-idr-bgp-optimal-route-reflection-16 (work in 313 progress), April 2018. 315 [RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584, 316 DOI 10.17487/RFC1584, March 1994, 317 . 319 [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. 320 McPherson, "OSPF Stub Router Advertisement", RFC 6987, 321 DOI 10.17487/RFC6987, September 2013, 322 . 324 Authors' Addresses 326 Keyur Patel 327 Arrcus 329 Email: keyur@arrcus.com 331 Padma Pillay-Esnault 332 Huawei Technologies 333 2330 Central Expressway 334 Santa Clara, CA 95050 335 USA 337 Email: padma@huawei.com 339 Manish Bhardwaj 340 Cisco Systems 341 170 W. Tasman Drive 342 San Jose, CA 95134 343 USA 345 Email: manbhard@cisco.com 347 Serpil Bayraktar 348 Cisco Systems 349 170 W. Tasman Drive 350 San Jose, CA 95134 351 USA 353 Email: serpil@cisco.com