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Kumar 4 Intended status: Standards Track IJ. Wijnands 5 Expires: August 26, 2018 Cisco 6 A. Dolganow 7 Nokia 8 T. Przygienda 9 J. Zhang 10 Juniper Networks, Inc. 11 S. Aldrin 12 Google, Inc. 13 February 22, 2018 15 OSPF Extensions for BIER 16 draft-ietf-bier-ospf-bier-extensions-14.txt 18 Abstract 20 Bit Index Explicit Replication (BIER) is an architecture that 21 provides multicast forwarding through a "BIER domain" without 22 requiring intermediate routers to maintain multicast related per-flow 23 state. Neither does BIER require an explicit tree-building protocol 24 for its operation. A multicast data packet enters a BIER domain at a 25 "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at 26 one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router 27 adds a BIER header to the packet. Such header contains a bit-string 28 in which each bit represents exactly one BFER to forward the packet 29 to. The set of BFERs to which the multicast packet needs to be 30 forwarded is expressed by the according set of bits set in BIER 31 packet header. 33 This document describes the OSPF [RFC2328] protocol extension 34 required for BIER with MPLS encapsulation [RFC8296]. Support for 35 other encapsulation types is outside thescope of this document. The 36 use of multiple encapsulation types is outside the scope of this 37 document. 39 Status of This Memo 41 This Internet-Draft is submitted in full conformance with the 42 provisions of BCP 78 and BCP 79. 44 Internet-Drafts are working documents of the Internet Engineering 45 Task Force (IETF). Note that other groups may also distribute 46 working documents as Internet-Drafts. The list of current Internet- 47 Drafts is at https://datatracker.ietf.org/drafts/current/. 49 Internet-Drafts are draft documents valid for a maximum of six months 50 and may be updated, replaced, or obsoleted by other documents at any 51 time. It is inappropriate to use Internet-Drafts as reference 52 material or to cite them other than as "work in progress." 54 This Internet-Draft will expire on August 26, 2018. 56 Copyright Notice 58 Copyright (c) 2018 IETF Trust and the persons identified as the 59 document authors. All rights reserved. 61 This document is subject to BCP 78 and the IETF Trust's Legal 62 Provisions Relating to IETF Documents 63 (https://trustee.ietf.org/license-info) in effect on the date of 64 publication of this document. Please review these documents 65 carefully, as they describe your rights and restrictions with respect 66 to this document. Code Components extracted from this document must 67 include Simplified BSD License text as described in Section 4.e of 68 the Trust Legal Provisions and are provided without warranty as 69 described in the Simplified BSD License. 71 Table of Contents 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 74 2. Flooding of the BIER Information in OSPF . . . . . . . . . . 3 75 2.1. BIER Sub-TLV . . . . . . . . . . . . . . . . . . . . . . 3 76 2.2. BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . . . 5 77 2.3. Flooding scope of BIER Information . . . . . . . . . . . 6 78 3. Security Considerations . . . . . . . . . . . . . . . . . . . 7 79 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 80 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 81 6. Normative References . . . . . . . . . . . . . . . . . . . . 8 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 84 1. Introduction 86 Bit Index Explicit Replication (BIER) is an architecture that 87 provides optimal multicast forwarding through a "BIER domain" without 88 requiring intermediate routers to maintain any multicast related per- 89 flow state. Neither does BIER explicitly require a tree-building 90 protocol for its operation. A multicast data packet enters a BIER 91 domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the 92 BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). 93 The BFIR router adds a BIER header to the packet. The BIER header 94 contains a bit-string in which each bit represents exactly one BFER 95 to forward the packet to. The set of BFERs to which the multicast 96 packet needs to be forwarded is expressed by setting the bits that 97 correspond to those routers in the BIER header. 99 BIER architecture requires routers participating in BIER to exchange 100 BIER related information within a given domain. BIER architecture 101 permits link-state routing protocols to perform distribution of such 102 information. This document describes extensions to OSPF necessary to 103 advertise BIER specific information in the case where BIER uses MPLS 104 encapsulation as described in [RFC8296]. 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 108 document are to be interpreted as described in [RFC2119]. 110 2. Flooding of the BIER Information in OSPF 112 All BIER specific information that a Bit-Forwarding Router (BFR) 113 needs to advertise to other BFRs is associated with a BFR-Prefix. A 114 BFR prefix is a unique (within a given BIER domain) routable IP 115 address that is assigned to each BFR as described in more detail in 116 section 2 of [RFC8279]. 118 Given that BIER information must be associated with a BFR prefix, the 119 OSPF Extended Prefix Opaque LSA [RFC7684] has been chosen for 120 advertisement. 122 2.1. BIER Sub-TLV 124 A Sub-TLV of the Extended Prefix TLV (defined in [RFC7684]) is 125 defined for distributing BIER information. The Sub-TLV is called the 126 BIER Sub-TLV. Multiple BIER Sub-TLVs may be included in the Extended 127 Prefix TLV. 129 The BIER Sub-TLV has the following format: 131 0 1 2 3 132 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 1 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | Type | Length | 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | Sub-domain-ID | MT-ID | BFR-id | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | BAR | IPA | Reserved | 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 | Sub-TLVs (variable) | 141 +- -+ 142 | | 143 Type: 9 145 Length: Variable, dependent on sub-TLVs. 147 Sub-domain-ID: Unique value identifying the BIER sub-domain within 148 the BIER domain, as described in section 1 of [RFC8279]. 150 MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies 151 the topology that is associated with the BIER sub-domain. 153 BFR-id: A 2 octet field encoding the BFR-id, as documented in 154 section 2 of [RFC8279]. If the BFR is not locally configured with 155 a valid BFR-id, the value of this field is set to invalid BFR-id 156 per [RFC8279]. 158 BAR: Single octet BIER specific algorithm used to calculate 159 underlay paths to reach other BFRs. Values are allocated from the 160 "BIER Algorithm Registry" which is defined in 161 [I-D.ietf-bier-isis-extensions]. 163 IPA: Single octet IGP algorithm to either modify, enhance or 164 replace the calculation of underlay paths to reach other BFRs as 165 defined by the BAR value. Values are defined in the "IGP 166 Algorithm Types" registry. 168 Each BFR sub-domain MUST be associated with one and only one OSPF 169 topology that is identified by the MT-ID. If the association between 170 BIER sub-domain and OSPF topology advertised in the BIER sub-TLV by 171 other BFRs is in conflict with the association locally configured on 172 the receiving router, the BIER Sub-TLV MUST be ignored. 174 If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs, 175 the BRF MUST be treated as if it did not advertise a BIER sub-TLV for 176 such sub-domain. 178 All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a 179 given MT-ID and Sub-domain-ID. When such duplication is detected all 180 BFRs advertising duplicates MUST be treated as if they did not 181 advertise a valid BFR-id. 183 The supported BAR and IPA algorithms MUST be consistent for all 184 routers supporting a given BFR sub-domain. A router receiving BIER 185 Sub-TLV advertisement with a value in BAR or IPA fields which does 186 not match the locally configured value for a given BFR sub-domain, 187 MUST report a misconfiguration for such BIER sub-domain and MUST 188 ignore such BIER sub-TLV. 190 The use of non-zero values in either the BAR field or the IPA field 191 is outside the scope of this document. 193 2.2. BIER MPLS Encapsulation Sub-TLV 195 The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV. 196 The BIER MPLS Encapsulation Sub-TLV is used in order to advertise 197 MPLS specific information used for BIER. It MAY appear multiple 198 times in the BIER Sub-TLV. 200 The BIER MPLS Encapsulation Sub-TLV has the following format: 202 0 1 2 3 203 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 1 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | Type | Length | 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | Max SI | Label | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 |BS Len | Reserved | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 Type: 10 214 Length: 4 octets 216 Max SI : A 1 octet field encoding the Maximum Set Identifier 217 (section 1 of [RFC8296]), used in the encapsulation for this BIER 218 sub-domain for this bitstring length. 220 Label: A 3 octet field, where the 20 rightmost bits represent the 221 first label in the label range. The 4 leftmost bits MUST be 222 ignored. 224 Bit String Length: A 4 bits field encoding the supported BitString 225 length associated with this BFR-prefix. The values allowed in 226 this field are specified in section 2 of [RFC8296]. 228 The "label range" is the set of labels beginning with the Label 229 and ending with (Label + (Max SI)). A unique label range is 230 allocated for each BitStream length and Sub-domain-ID. These 231 labels are used for BIER forwarding as described in [RFC8279] and 232 [RFC8296]. 234 The size of the label range is determined by the number of Set 235 Identifiers (SI) (section 1 of [RFC8279]) that are used in the 236 network. Each SI maps to a single label in the label range. The 237 first label is for SI=0, the second label is for SI=1, etc. 239 If same BS length is repeated in multiple BIER MPLS Encapsulation 240 Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be 241 ignored. 243 Label ranges within all BIER MPLS Encapsulation Sub-TLVs advertised 244 by the same BFR MUST NOT overlap. If the overlap is detected, the 245 advertising router MUST be treated as if it did not advertise any 246 BIER sub-TLVs. 248 All advertised labels MUST be valid, otherwise the BIER sub-TLV MUST 249 be ignored. 251 2.3. Flooding scope of BIER Information 253 The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684] 254 that is used for advertising the BIER Sub-TLV is set to area-local. 255 To allow BIER deployment in a multi-area environment, OSPF must 256 propagate BIER information between areas. 258 ( ) ( ) ( ) 259 ( ) ( ) ( ) 260 R1 Area 1 R2 Area 0 R3 Area 2 R4 261 ( ) ( ) ( ) 262 ( ) ( ) ( ) 264 Figure 1: BIER propagation between areas 266 The following procedure is used in order to propagate BIER related 267 information between areas: 269 When an OSPF Area Border Router (ABR) advertises a Type-3 Summary 270 LSA from an intra-area or inter-area prefix to all its attached 271 areas, it will also originate an Extended Prefix Opaque LSA, as 272 described in [RFC7684]. The flooding scope of the Extended Prefix 273 Opaque LSA type will be set to area-local. The route-type in the 274 OSPF Extended Prefix TLV is set to inter-area. When determining 275 whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR 276 will: 278 - Examine its best path to the prefix in the source area and 279 find the advertising router associated with the best path to 280 that prefix. 282 - Determine if such advertising router advertised a BIER Sub- 283 TLV for the prefix. If yes, the ABR will copy the information 284 from such BIER Sub-TLV when advertising BIER Sub-TLV to each 285 attached area. 287 In the Figure 1, R1 advertises a prefix 192.0.2.1/32 in Area 1. 288 It also advertises Extended Prefix Opaque LSA for prefix 289 192.0.2.1/32 and includes BIER Sub-TLV in it. Area Border Router 290 (ABR) R2 calculates the reachability for prefix 192.0.2.1/32 291 inside Area 1 and propagates it to Area 0. When doing so, it 292 copies the entire BIER Sub-TLV (including all its Sub-TLVs) it 293 received from R1 in Area 1 and includes it in the Extended Prefix 294 Opaque LSA it generates for 192.0.2.1/32 in Area 0. ABR R3 295 calculates the reachability for prefix 192.0.2.1/32 inside Area 0 296 and propagates it to Area 2. When doing so, it copies the entire 297 BIER Sub-TLV (including all its Sub-TLVs) it received from R2 in 298 Area 0 and includes it in the Extended Prefix Opaque LSA it 299 generates for 192.0.2.1/32 in Area 2. 301 3. Security Considerations 303 This document introduces new sub-TLVs for existing OSPF Extended 304 Prefix TLV. It does not introduce any new security risks to OSPF. 305 Existing security extensions as described in [RFC2328] and [RFC7684] 306 apply. 308 It is assumed that both BIER and OSPF layer is under a single 309 administrative domain. There can be deployments where potential 310 attackers have access to one or more networks in the OSPF routing 311 domain. In these deployments, stronger authentication mechanisms 312 such as those specified in [RFC7474] SHOULD be used. 314 Implementations MUST assure that malformed TLV and Sub-TLV defined in 315 this document are detected and do not provide a vulnerability for 316 attackers to crash the OSPF router or routing process. Reception of 317 malformed TLV or Sub-TLV SHOULD be counted and/or logged for further 318 analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be rate- 319 limited to prevent a Denial of Service (DoS) attack (distributed or 320 otherwise) from overloading the OSPF control plane. 322 4. IANA Considerations 324 The document requests three new allocations from the OSPF Extended 325 Prefix sub-TLV registry as defined in [RFC7684]. 327 BIER Sub-TLV: 9 329 BIER MPLS Encapsulation Sub-TLV: 10 331 5. Acknowledgments 333 The authors would like to thank Rajiv Asati, Christian Martin, Greg 334 Shepherd and Eric Rosen for their contribution. 336 6. Normative References 338 [I-D.ietf-bier-isis-extensions] 339 Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang, 340 "BIER support via ISIS", draft-ietf-bier-isis- 341 extensions-07 (work in progress), February 2018. 343 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 344 Requirement Levels", BCP 14, RFC 2119, 345 DOI 10.17487/RFC2119, March 1997, 346 . 348 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 349 DOI 10.17487/RFC2328, April 1998, 350 . 352 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 353 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 354 RFC 4915, DOI 10.17487/RFC4915, June 2007, 355 . 357 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 358 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 359 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 360 2015, . 362 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 363 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 364 Explicit Replication (BIER)", RFC 8279, 365 DOI 10.17487/RFC8279, November 2017, 366 . 368 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 369 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 370 for Bit Index Explicit Replication (BIER) in MPLS and Non- 371 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 372 2018, . 374 Authors' Addresses 375 Peter Psenak (editor) 376 Cisco 377 Apollo Business Center 378 Mlynske nivy 43 379 Bratislava 821 09 380 Slovakia 382 Email: ppsenak@cisco.com 384 Nagendra Kumar 385 Cisco 386 7200 Kit Creek Road 387 Research Triangle Park, NC 27709 388 US 390 Email: naikumar@cisco.com 392 IJsbrand Wijnands 393 Cisco 394 De Kleetlaan 6a 395 Diegem 1831 396 Belgium 398 Email: ice@cisco.com 400 Andrew Dolganow 401 Nokia 402 750 Chai Chee Rd 403 06-06 Viva Business Park 404 Singapore 469004 406 Email: andrew.dolganow@nokia.com 408 Tony Przygienda 409 Juniper Networks, Inc. 410 10 Technology Park Drive 411 Westford, MA 01886 412 USA 414 Email: prz@juniper.net 415 Jeffrey Zhang 416 Juniper Networks, Inc. 417 10 Technology Park Drive 418 Westford, MA 01886 419 USA 421 Email: zzhang@juniper.net 423 Sam Aldrin 424 Google, Inc. 425 1600 Amphitheatre Parkway 426 Mountain View, CA 427 USA 429 Email: aldrin.ietf@gmail.com