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Wijnands 5 Expires: June 7, 2018 Cisco 6 A. Dolganow 7 Nokia 8 T. Przygienda 9 J. Zhang 10 Juniper Networks, Inc. 11 S. Aldrin 12 Google, Inc. 13 December 4, 2017 15 OSPF Extensions for BIER 16 draft-ietf-bier-ospf-bier-extensions-10.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 protocol extension required for BIER 34 with MPLS encapsulation. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at https://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on June 7, 2018. 53 Copyright Notice 55 Copyright (c) 2017 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (https://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 71 2. Flooding of the BIER Information in OSPF . . . . . . . . . . 3 72 2.1. BIER Sub-TLV . . . . . . . . . . . . . . . . . . . . . . 3 73 2.2. BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . . . 4 74 2.3. Flooding scope of BIER Information . . . . . . . . . . . 6 75 3. Security Considerations . . . . . . . . . . . . . . . . . . . 7 76 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 77 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 78 6. Normative References . . . . . . . . . . . . . . . . . . . . 7 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 81 1. Introduction 83 Bit Index Explicit Replication (BIER) is an architecture that 84 provides optimal multicast forwarding through a "BIER domain" without 85 requiring intermediate routers to maintain any multicast related per- 86 flow state. Neither does BIER explicitly require a tree-building 87 protocol for its operation. A multicast data packet enters a BIER 88 domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the 89 BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). 90 The BFIR router adds a BIER header to the packet. The BIER header 91 contains a bit-string in which each bit represents exactly one BFER 92 to forward the packet to. The set of BFERs to which the multicast 93 packet needs to be forwarded is expressed by setting the bits that 94 correspond to those routers in the BIER header. 96 BIER architecture requires routers participating in BIER to exchange 97 BIER related information within a given domain. BIER architecture 98 permits link-state routing protocols to perform distribution of such 99 information. This document describes extensions to OSPF necessary to 100 advertise BIER specific information in the case where BIER uses MPLS 101 encapsulation as described in [I-D.ietf-bier-mpls-encapsulation]. 103 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 104 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 105 document are to be interpreted as described in [RFC2119]. 107 2. Flooding of the BIER Information in OSPF 109 All BIER specific information that a Bit-Forwarding Router (BFR) 110 needs to advertise to other BFRs is associated with a BFR-Prefix. A 111 BFR prefix is a unique (within a given BIER domain) routable IP 112 address that is assigned to each BFR as described in more detail in 113 section 2 of [I-D.ietf-bier-architecture]. 115 Given that BIER information must be associated with a BFR prefix, the 116 OSPF Extended Prefix Opaque LSA [RFC7684] has been chosen for 117 advertisement. 119 2.1. BIER Sub-TLV 121 A Sub-TLV of the Extended Prefix TLV (defined in [RFC7684]) is 122 defined for distributing BIER information. The Sub-TLV is called the 123 BIER Sub-TLV. Multiple BIER Sub-TLVs may be included in the Extended 124 Prefix TLV. 126 The BIER Sub-TLV has the following format: 128 0 1 2 3 129 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 1 130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 | Type | Length | 132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 | Sub-domain-ID | MT-ID | BFR-id | 134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 | BAR | Reserved | 136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 | Sub-TLVs (variable) | 138 +- -+ 139 | | 141 Type: 9 142 Length: Variable, dependent on sub-TLVs. 144 Sub-domain-ID: Unique value identifying the BIER sub-domain within 145 the BIER domain, as described in section 1 of 146 [I-D.ietf-bier-architecture]. 148 MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies 149 the topology that is associated with the BIER sub-domain. 151 BFR-id: A 2 octet field encoding the BFR-id, as documented in 152 section 2 of [I-D.ietf-bier-architecture]. If the BFR is not 153 locally configured with a valid BFR-id, the value of this field is 154 set to invalid BFR-id per [I-D.ietf-bier-architecture]. 156 BAR: Single octet BIER Algorithm. 0 is the only supported value 157 defined in this document and represents Shortest Path First (SPF) 158 algorithm based on IGP link metric. This is the standard shortest 159 path algorithm as computed by the OSPF protocol. Other values may 160 be defined in the future. 162 Each BFR sub-domain MUST be associated with one and only one OSPF 163 topology that is identified by the MT-ID. If the association between 164 BIER sub-domain and OSPF topology advertised in the BIER sub-TLV by 165 other BFRs is in conflict with the association locally configured on 166 the receiving router, the BIER Sub-TLV MUST be ignored. 168 If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs, 169 the BRF MUST be treated as if it did not advertise a BIER sub-TLV for 170 such sub-domain. 172 All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a 173 given MT-ID and Sub-domain-ID. When such duplication is detected all 174 BFRs advertising duplicates MUST be treated as if they did not 175 advertise a valid BFR-id. 177 The supported algorithm MUST be consistent for all routers supporting 178 a given BFR sub-domain. A router receiving BIER Sub-TLV 179 advertisement with a BAR which does not match the locally configured 180 value MUST report a misconfiguration for the given BIER sub-domain 181 and MUST ignore such BIER sub-TLV. 183 2.2. BIER MPLS Encapsulation Sub-TLV 185 The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV. 186 The BIER MPLS Encapsulation Sub-TLV is used in order to advertise 187 MPLS specific information used for BIER. It MAY appear multiple 188 times in the BIER Sub-TLV. 190 The BIER MPLS Encapsulation Sub-TLV has the following format: 192 0 1 2 3 193 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 1 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 | Type | Length | 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 |Lbl Range Size | Label Range Base | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 |BS Len | Reserved | 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 Type: 10 204 Length: 4 octets 206 Label Range Size: A 1 octet field encoding the label range size of 207 the label range. It MUST be greater then 0, otherwise the 208 advertising router MUST be treated as if it did not advertise a 209 BIER sub-TLV. 211 Label Range Base: A 3 octet field, where the 20 rightmost bits 212 represent the first label in the label range. The 4 leftmost bits 213 MUST be ignored. 215 Bit String Length: A 4 bits field encoding the supported BitString 216 length associated with this BFR-prefix. The values allowed in 217 this field are specified in section 2 of 218 [I-D.ietf-bier-mpls-encapsulation]. 220 The "label range" is the set of labels beginning with the label 221 range base and ending with ((label range base)+(label range size)- 222 1). A unique label range is allocated for each BitStream length 223 and Sub-domain-ID. These labels are used for BIER forwarding as 224 described in [I-D.ietf-bier-architecture] and 225 [I-D.ietf-bier-mpls-encapsulation]. 227 The size of the label range is determined by the number of Set 228 Identifiers (SI) (section 1 of [I-D.ietf-bier-architecture]) that 229 are used in the network. Each SI maps to a single label in the 230 label range. The first label is for SI=0, the second label is for 231 SI=1, etc. 233 If same BS length is repeated in multiple BIER MPLS Encapsulation 234 Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be 235 ignored. 237 Label ranges within all BIER MPLS Encapsulation Sub-TLV inside the 238 same BIER Sub-TLV MUST NOT overlap. If the overlap is detected, the 239 advertising router MUST be treated as if it did not advertise a BIER 240 sub-TLV. 242 All advertised labels MUST be valid, otherwise the BIER sub-TLV MUST 243 be ignored. 245 2.3. Flooding scope of BIER Information 247 The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684] 248 that is used for advertising the BIER Sub-TLV is set to area-local. 249 To allow BIER deployment in a multi-area environment, OSPF must 250 propagate BIER information between areas. 252 ( ) ( ) ( ) 253 ( ) ( ) ( ) 254 R1 Area 1 R2 Area 0 R3 Area 2 R4 255 ( ) ( ) ( ) 256 ( ) ( ) ( ) 258 Figure 1: BIER propagation between areas 260 The following procedure is used in order to propagate BIER related 261 information between areas: 263 When an OSPF Area Border Router (ABR) advertises a Type-3 Summary 264 LSA from an intra-area or inter-area prefix to all its attached 265 areas, it will also originate an Extended Prefix Opaque LSA, as 266 described in [RFC7684]. The flooding scope of the Extended Prefix 267 Opaque LSA type will be set to area-local. The route-type in the 268 OSPF Extended Prefix TLV is set to inter-area. When determining 269 whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR 270 will: 272 - Examine its best path to the prefix in the source area and 273 find the advertising router associated with the best path to 274 that prefix. 276 - Determine if such advertising router advertised a BIER Sub- 277 TLV for the prefix. If yes, the ABR will copy the information 278 from such BIER Sub-TLV when advertising BIER Sub-TLV to each 279 attached area. 281 In the Figure 1, R1 advertises a prefix 192.0.0.1/32 in Area 1. 282 It also advertises Extended Prefix Opaque LSA for prefix 283 192.0.0.1/32 and includes BIER Sub-TLV in it. Area Border Router 284 (ABR) R2 calculates the reachability for prefix 192.0.0.1/32 285 inside Area 1 and propagates it to Area 0. When doing so, it 286 copies the entire BIER Sub-TLV (including all its Sub-TLVs) it 287 received from R1 in Area 1 and includes it in the Extended Prefix 288 Opaque LSA it generates for 192.0.0.1/32 in Area 0. ABR R3 289 calculates the reachability for prefix 192.0.0.1/32 inside Area 0 290 and propagates it to Area 2. When doing so, it copies the entire 291 BIER Sub-TLV (including all its Sub-TLVs) it received from R2 in 292 Area 0 and includes it in the Extended Prefix Opaque LSA it 293 generates for 192.0.0.1/32 in Area 2. 295 3. Security Considerations 297 Implementations must assure that malformed TLV and Sub-TLV 298 permutations do not result in errors which cause hard OSPF failures. 300 4. IANA Considerations 302 The document requests three new allocations from the OSPF Extended 303 Prefix sub-TLV registry as defined in [RFC7684]. 305 BIER Sub-TLV: 9 307 BIER MPLS Encapsulation Sub-TLV: 10 309 5. Acknowledgments 311 The authors would like to thank Rajiv Asati, Christian Martin, Greg 312 Shepherd and Eric Rosen for their contribution. 314 6. Normative References 316 [I-D.ietf-bier-architecture] 317 Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and 318 S. Aldrin, "Multicast using Bit Index Explicit 319 Replication", draft-ietf-bier-architecture-06 (work in 320 progress), April 2017. 322 [I-D.ietf-bier-mpls-encapsulation] 323 Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J., 324 Aldrin, S., and I. Meilik, "Encapsulation for Bit Index 325 Explicit Replication in MPLS and non-MPLS Networks", 326 draft-ietf-bier-mpls-encapsulation-07 (work in progress), 327 June 2017. 329 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 330 Requirement Levels", BCP 14, RFC 2119, 331 DOI 10.17487/RFC2119, March 1997, 332 . 334 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 335 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 336 RFC 4915, DOI 10.17487/RFC4915, June 2007, 337 . 339 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 340 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 341 2014, . 343 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 344 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 345 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 346 2015, . 348 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 349 Writing an IANA Considerations Section in RFCs", BCP 26, 350 RFC 8126, DOI 10.17487/RFC8126, June 2017, 351 . 353 Authors' Addresses 355 Peter Psenak (editor) 356 Cisco 357 Apollo Business Center 358 Mlynske nivy 43 359 Bratislava 821 09 360 Slovakia 362 Email: ppsenak@cisco.com 364 Nagendra Kumar 365 Cisco 366 7200 Kit Creek Road 367 Research Triangle Park, NC 27709 368 US 370 Email: naikumar@cisco.com 371 IJsbrand Wijnands 372 Cisco 373 De Kleetlaan 6a 374 Diegem 1831 375 Belgium 377 Email: ice@cisco.com 379 Andrew Dolganow 380 Nokia 381 750 Chai Chee Rd 382 06-06 Viva Business Park 383 Singapore 469004 385 Email: andrew.dolganow@nokia.com 387 Tony Przygienda 388 Juniper Networks, Inc. 389 10 Technology Park Drive 390 Westford, MA 01886 391 USA 393 Email: prz@juniper.net 395 Jeffrey Zhang 396 Juniper Networks, Inc. 397 10 Technology Park Drive 398 Westford, MA 01886 399 USA 401 Email: zzhang@juniper.net 403 Sam Aldrin 404 Google, Inc. 405 1600 Amphitheatre Parkway 406 Mountain View, CA 407 USA 409 Email: aldrin.ietf@gmail.com