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Kumar 4 Intended status: Standards Track IJ. Wijnands 5 Expires: August 27, 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 23, 2018 15 OSPF Extensions for BIER 16 draft-ietf-bier-ospf-bier-extensions-15.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 27, 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 0, which is 156 defined as illegal in [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 the MT-ID value is outside of the values specified in [RFC4915], 175 the BIER Sub-TLV MUST be ignored. 177 If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs, 178 the BRF MUST be treated as if it did not advertise a BIER sub-TLV for 179 such sub-domain. 181 All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a 182 given MT-ID and Sub-domain-ID. When such duplication is detected by 183 the BFR, it MUST behave as described in section 5 of [RFC8279]. 185 The supported BAR and IPA algorithms MUST be consistent for all 186 routers supporting a given BFR sub-domain. A router receiving BIER 187 Sub-TLV advertisement with a value in BAR or IPA fields which does 188 not match the locally configured value for a given BFR sub-domain, 189 MUST report a misconfiguration for such BIER sub-domain and MUST 190 ignore such BIER sub-TLV. 192 The use of non-zero values in either the BAR field or the IPA field 193 is outside the scope of this document. 195 2.2. BIER MPLS Encapsulation Sub-TLV 197 The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV. 198 The BIER MPLS Encapsulation Sub-TLV is used in order to advertise 199 MPLS specific information used for BIER. It MAY appear multiple 200 times in the BIER Sub-TLV. 202 The BIER MPLS Encapsulation Sub-TLV has the following format: 204 0 1 2 3 205 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 1 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | Type | Length | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Max SI | Label | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 |BS Len | Reserved | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 Type: 10 216 Length: 4 octets 218 Max SI : A 1 octet field encoding the Maximum Set Identifier 219 (section 1 of [RFC8296]), used in the encapsulation for this BIER 220 sub-domain for this bitstring length. 222 Label: A 3 octet field, where the 20 rightmost bits represent the 223 first label in the label range. The 4 leftmost bits MUST be 224 ignored. 226 Bit String Length: A 4 bits field encoding the supported BitString 227 length associated with this BFR-prefix. The values allowed in 228 this field are specified in section 2 of [RFC8296]. 230 The "label range" is the set of labels beginning with the Label 231 and ending with (Label + (Max SI)). A unique label range is 232 allocated for each BitStream length and Sub-domain-ID. These 233 labels are used for BIER forwarding as described in [RFC8279] and 234 [RFC8296]. 236 The size of the label range is determined by the number of Set 237 Identifiers (SI) (section 1 of [RFC8279]) that are used in the 238 network. Each SI maps to a single label in the label range. The 239 first label is for SI=0, the second label is for SI=1, etc. 241 If the BS length is set to a value that does not match any of the 242 allowed values specified in [RFC8296], the BIER MPLS Encapsulation 243 Sub-TLV MUST be ignored. 245 If same BS length is repeated in multiple BIER MPLS Encapsulation 246 Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be 247 ignored. 249 Label ranges within all BIER MPLS Encapsulation Sub-TLVs advertised 250 by the same BFR MUST NOT overlap. If the overlap is detected, the 251 advertising router MUST be treated as if it did not advertise any 252 BIER sub-TLVs. 254 2.3. Flooding scope of BIER Information 256 The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684] 257 that is used for advertising the BIER Sub-TLV is set to area-local. 258 To allow BIER deployment in a multi-area environment, OSPF must 259 propagate BIER information between areas. 261 ( ) ( ) ( ) 262 ( ) ( ) ( ) 263 R1 Area 1 R2 Area 0 R3 Area 2 R4 264 ( ) ( ) ( ) 265 ( ) ( ) ( ) 267 Figure 1: BIER propagation between areas 269 The following procedure is used in order to propagate BIER related 270 information between areas: 272 When an OSPF Area Border Router (ABR) advertises a Type-3 Summary 273 LSA from an intra-area or inter-area prefix to all its attached 274 areas, it will also originate an Extended Prefix Opaque LSA, as 275 described in [RFC7684]. The flooding scope of the Extended Prefix 276 Opaque LSA type will be set to area-local. The route-type in the 277 OSPF Extended Prefix TLV is set to inter-area. When determining 278 whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR 279 will: 281 - Examine its best path to the prefix in the source area and 282 find the advertising router associated with the best path to 283 that prefix. 285 - Determine if such advertising router advertised a BIER Sub- 286 TLV for the prefix. If yes, the ABR will copy the information 287 from such BIER Sub-TLV when advertising BIER Sub-TLV to each 288 attached area. 290 In the Figure 1, R1 advertises a prefix 192.0.2.1/32 in Area 1. 291 It also advertises Extended Prefix Opaque LSA for prefix 292 192.0.2.1/32 and includes BIER Sub-TLV in it. Area Border Router 293 (ABR) R2 calculates the reachability for prefix 192.0.2.1/32 294 inside Area 1 and propagates it to Area 0. When doing so, it 295 copies the entire BIER Sub-TLV (including all its Sub-TLVs) it 296 received from R1 in Area 1 and includes it in the Extended Prefix 297 Opaque LSA it generates for 192.0.2.1/32 in Area 0. ABR R3 298 calculates the reachability for prefix 192.0.2.1/32 inside Area 0 299 and propagates it to Area 2. When doing so, it copies the entire 300 BIER Sub-TLV (including all its Sub-TLVs) it received from R2 in 301 Area 0 and includes it in the Extended Prefix Opaque LSA it 302 generates for 192.0.2.1/32 in Area 2. 304 3. Security Considerations 306 This document introduces new sub-TLVs for existing OSPF Extended 307 Prefix TLV. It does not introduce any new security risks to OSPF. 308 Existing security extensions as described in [RFC2328] and [RFC7684] 309 apply. 311 It is assumed that both BIER and OSPF layer is under a single 312 administrative domain. There can be deployments where potential 313 attackers have access to one or more networks in the OSPF routing 314 domain. In these deployments, stronger authentication mechanisms 315 such as those specified in [RFC7474] SHOULD be used. 317 Implementations MUST assure that malformed TLV and Sub-TLV defined in 318 this document are detected and do not provide a vulnerability for 319 attackers to crash the OSPF router or routing process. Reception of 320 malformed TLV or Sub-TLV SHOULD be counted and/or logged for further 321 analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be rate- 322 limited to prevent a Denial of Service (DoS) attack (distributed or 323 otherwise) from overloading the OSPF control plane. 325 4. IANA Considerations 327 The document requests three new allocations from the OSPF Extended 328 Prefix sub-TLV registry as defined in [RFC7684]. 330 BIER Sub-TLV: 9 332 BIER MPLS Encapsulation Sub-TLV: 10 334 5. Acknowledgments 336 The authors would like to thank Rajiv Asati, Christian Martin, Greg 337 Shepherd and Eric Rosen for their contribution. 339 6. Normative References 341 [I-D.ietf-bier-isis-extensions] 342 Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang, 343 "BIER support via ISIS", draft-ietf-bier-isis- 344 extensions-08 (work in progress), February 2018. 346 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 347 Requirement Levels", BCP 14, RFC 2119, 348 DOI 10.17487/RFC2119, March 1997, 349 . 351 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 352 DOI 10.17487/RFC2328, April 1998, 353 . 355 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 356 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 357 RFC 4915, DOI 10.17487/RFC4915, June 2007, 358 . 360 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 361 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 362 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 363 2015, . 365 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 366 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 367 Explicit Replication (BIER)", RFC 8279, 368 DOI 10.17487/RFC8279, November 2017, 369 . 371 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 372 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 373 for Bit Index Explicit Replication (BIER) in MPLS and Non- 374 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 375 2018, . 377 Authors' Addresses 378 Peter Psenak (editor) 379 Cisco 380 Apollo Business Center 381 Mlynske nivy 43 382 Bratislava 821 09 383 Slovakia 385 Email: ppsenak@cisco.com 387 Nagendra Kumar 388 Cisco 389 7200 Kit Creek Road 390 Research Triangle Park, NC 27709 391 US 393 Email: naikumar@cisco.com 395 IJsbrand Wijnands 396 Cisco 397 De Kleetlaan 6a 398 Diegem 1831 399 Belgium 401 Email: ice@cisco.com 403 Andrew Dolganow 404 Nokia 405 750 Chai Chee Rd 406 06-06 Viva Business Park 407 Singapore 469004 409 Email: andrew.dolganow@nokia.com 411 Tony Przygienda 412 Juniper Networks, Inc. 413 10 Technology Park Drive 414 Westford, MA 01886 415 USA 417 Email: prz@juniper.net 418 Jeffrey Zhang 419 Juniper Networks, Inc. 420 10 Technology Park Drive 421 Westford, MA 01886 422 USA 424 Email: zzhang@juniper.net 426 Sam Aldrin 427 Google, Inc. 428 1600 Amphitheatre Parkway 429 Mountain View, CA 430 USA 432 Email: aldrin.ietf@gmail.com