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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-28) exists of draft-ietf-idr-bgp-optimal-route-reflection-16 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 OSPF K. Patel 3 Internet-Draft Arrcus 4 Intended status: Standards Track P. Pillay-Esnault 5 Expires: February 2, 2019 Huawei Technologies 6 M. Bhardwaj 7 S. Bayraktar 8 Cisco Systems 9 August 1, 2018 11 H-bit Support for OSPFv2 12 draft-ietf-ospf-ospfv2-hbit-05 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 used as a transit router. 19 In such cases, other routers in the OSPFv3 routing domain only 20 install routes to allow local traffic delivery. This draft defines 21 the H-bit functionality to prevent other OSPFv2 routers from using 22 the router for transit traffic in OSPFv2 routing domains as described 23 in 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 2, 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 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 61 3. H-bit Support . . . . . . . . . . . . . . . . . . . . . . . . 3 62 4. SPF Modifications . . . . . . . . . . . . . . . . . . . . . . 5 63 5. Auto Discovery and Backward Compatibility . . . . . . . . . . 5 64 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics . . . . . 6 65 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 66 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 67 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 68 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 69 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 70 10.2. Informative References . . . . . . . . . . . . . . . . . 7 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 73 1. Introduction 75 OSPFv3 [RFC5340] defines an option bit for router-LSAs known as the 76 R-bit. If the R-bit is clear, an OSPFv3 router can participate in 77 OSPFv3 topology flooding without acting as a transit router. In such 78 cases, other routers in the OSPFv3 routing domain only install routes 79 used for local traffic. 81 This functionality is particularly useful for BGP Route Reflectors, 82 known as virtual Route Reflectors (vRRs), that are not in the 83 forwarding path but are in central locations such as data centers. 84 Such Route Reflectors typically are used for route distribution and 85 are not capable of forwarding transit traffic. However, they need to 86 learn the OSPF topology for: 88 1. SPF computation for Optimal Route Reflection functionality as 89 defined in [I-D.ietf-idr-bgp-optimal-route-reflection] 91 2. Reachability resolution for its Route Reflector Clients. 93 This draft defines the R-bit functionality equivalent for OSPFv2 94 defined in [RFC2328] by introducing a new router-LSA bit known as the 95 "H-bit". 97 2. Requirements Language 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 3. H-bit Support 107 This document defines a new router-LSA bit known as the Host Bit or 108 the H-bit. An OSPFv2 router advertising a router-LSA with the H-bit 109 set indicates to other OSPFv2 routers in the area supporting the 110 functionality that it MUST NOT be used as a transit router. The bit 111 value usage of the H-bit is reversed from the R-bit defined in OSPFv3 112 [RFC5340] to support backward compatibility. The modified OSPFv2 113 router-LSA format is: 115 0 1 2 3 116 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 1 117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 | LS age | Options | 1 | 119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 | Link State ID | 121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 | Advertising Router | 123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 124 | LS sequence number | 125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 | LS checksum | length | 127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 128 |H|0|0|N|W|V|E|B| 0 | # links | 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 | Link ID | 131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 | Link Data | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | Type | # TOS | metric | 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | ... | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | TOS | 0 | TOS metric | 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 | Link ID | 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 | Link Data | 143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 | ... | 146 bit H 147 When set, an OSPFv2 router is a non-transit router and is 148 incapable of forwarding transit traffic. 150 When the H-bit is set, an OSPFv2 router is a non-transit router and 151 should not be used to forward transit traffic. In this mode, the 152 other OSPFv2 routers in the area SHOULD NOT use the originating 153 OSPFv2 router for transit traffic, but MAY use the OSPFv2 router for 154 local traffic destined to that OSPFv2 router. 156 An OSPFv2 router originating a router-LSA with the H-bit set SHOULD 157 advertise all its non-local router links with a link cost of 158 MaxLinkMetric as defined in Section 3 of [RFC6987]. This is to 159 increase the applicability of the H-bit to partial deployments where 160 it is the responsibility of the operator to ensure that OSPFv2 161 routers not supporting the H-bit do not install routes causing 162 routing loops. 164 When the H-bit is set, IPv4 prefixes associated with local interfaces 165 in other areas MAY be advertised in summary LSAs. Non-local IPv4 166 prefixes, e.g., those advertised by other routers and installed 167 during the SPF computation, MAY be advertised in summary-LSAs if 168 configured by policy. Likewise, when the H-bit is set, only IPv4 169 prefixes associated with local interfaces MAY be advertised in AS- 170 external LSAs. Non-local IPv4 prefixes, e.g., those exported from 171 other routing protocols, MUST NOT be advertised in AS-external-LSAs. 172 Finally, when the H-bit is set, an Area Border Router (ABR) MUST 173 advertise a consistent H-bit setting in its self-originated router- 174 LSAs for all attached areas. 176 4. SPF Modifications 178 The SPF calculation described in section 16.1 [RFC2328] will be 179 modified to ensure that the routers originating router-LSAs with the 180 H-bit set will not be used for transit traffic. Step 2 is modified 181 as follows: 183 2) Call the vertex just added to the 184 tree vertex V. Examine the LSA 185 associated with vertex V. This is 186 a lookup in the Area A's link state 187 database based on the Vertex ID. If 188 this is a router-LSA, and the H-bit 189 of the router-LSA is set, and 190 vertex V is not the root, then the 191 router should not be used for transit 192 and step (3) should be executed 193 immediately. If this is a router-LSA, 194 and bit V of the router-LSA (see 195 Section A.4.2) is set, set Area A's 196 TransitCapability to TRUE. In any case, 197 each link described by the LSA gives 198 the cost to an adjacent vertex. For 199 each described link, (say it joins 200 vertex V to vertex W): 202 5. Auto Discovery and Backward Compatibility 204 To avoid the possibility of any routing loops due to partial 205 deployment, this document defines a OSPF Router-Information LSA 206 functional capability bit known as the Host Support capability. 208 Auto Discovery via announcement of the Host Support Functional 209 Capability ensures that the H-bit functionality and its associated 210 SPF changes SHOULD only take effect if all the routers in a given 211 OSPF area support this functionality. 213 Implementations are encouraged to provide a configuration parameter 214 to manually override enforcement of the H-bit functionality in 215 partial deployments where the topology guarantees that OSPFv2 routers 216 not supporting the H-bit do not compute routes resulting in routing 217 loops. More precisely, the advertisement of MaxLinkMetric for the 218 router's non-local links will prevent OSPFv2 routers not supporting 219 the H-bit from attempting to use it for transit traffic. 221 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics 223 When calculating the path to an OSPF AS-External-LSA or NSSA-LSA with 224 a Type-2 metric, the advertised Type-2 metric is taken as more 225 significant than the OSPF intra-area or inter-area path. Hence, 226 advertising the links with MaxLinkMetric as specified in [RFC6987] 227 does not discourage transit traffic when calculating AS external or 228 NSSA routes. Consequently, OSPF routers implementing [RFC6987] or 229 this specification should advertise a Type-2 metric of LSInfinity for 230 any self-originated AS-External-LSAs or NSSA-LSAs in situations when 231 the OSPF router is acting as a stub router [RFC6987] or implementing 232 this specification. 234 7. IANA Considerations 236 IANA is requested to create the OSPF Router-LSA bit registry with the 237 following assignments: 239 Value Description Reference 240 0x01 Area Border Router (B-bit) [RFC2328] 241 0x02 AS Boundary Router (E-bit) [RFC2328] 242 0x04 Virtual Link Endpoint (V-bit) [RFC2328] 243 0x08 Historic (W-bit) [RFC1584] 244 0x10 Unconditional NSSA Translator (Nt-bit) [RFC3101] 245 0x20 Unassigned 246 0x40 Unassigned 247 0x80 Host (H-bit) This Document 249 This document also defines a new Router Functional Capability 250 [RFC7770] known as the Host Support Functional Capability. This 251 document requests IANA to allocate the value of this capability from 252 the Router Functional Capability Bits TLV. 254 8. Security Considerations 256 This document introduces no new security considerations beyond those 257 already specified in [RFC6987], [RFC2328], and [RFC5340]. 259 9. Acknowledgements 261 The authors would like to acknowledge Hasmit Grover for discovery of 262 the limitation in [RFC6987], Acee Lindem, Abhay Roy, David Ward, 263 Burjiz Pithawala and Michael Barnes for their comments. 265 10. References 267 10.1. Normative References 269 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 270 Requirement Levels", BCP 14, RFC 2119, 271 DOI 10.17487/RFC2119, March 1997, 272 . 274 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 275 DOI 10.17487/RFC2328, April 1998, 276 . 278 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 279 RFC 3101, DOI 10.17487/RFC3101, January 2003, 280 . 282 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 283 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 284 . 286 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 287 S. Shaffer, "Extensions to OSPF for Advertising Optional 288 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 289 February 2016, . 291 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 292 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 293 May 2017, . 295 10.2. Informative References 297 [I-D.ietf-idr-bgp-optimal-route-reflection] 298 Raszuk, R., Cassar, C., Aman, E., Decraene, B., and K. 299 Wang, "BGP Optimal Route Reflection (BGP-ORR)", draft- 300 ietf-idr-bgp-optimal-route-reflection-16 (work in 301 progress), April 2018. 303 [RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584, 304 DOI 10.17487/RFC1584, March 1994, 305 . 307 [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. 308 McPherson, "OSPF Stub Router Advertisement", RFC 6987, 309 DOI 10.17487/RFC6987, September 2013, 310 . 312 Authors' Addresses 314 Keyur Patel 315 Arrcus 317 Email: keyur@arrcus.com 319 Padma Pillay-Esnault 320 Huawei Technologies 321 2330 Central Expressway 322 Santa Clara, CA 95050 323 USA 325 Email: padma@huawei.com 327 Manish Bhardwaj 328 Cisco Systems 329 170 W. Tasman Drive 330 San Jose, CA 95134 331 USA 333 Email: manbhard@cisco.com 335 Serpil Bayraktar 336 Cisco Systems 337 170 W. Tasman Drive 338 San Jose, CA 95134 339 USA 341 Email: serpil@cisco.com