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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 14, 2018) is 2260 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 OSPF P. Psenak, Ed. 3 Internet-Draft N. Kumar 4 Intended status: Standards Track IJ. Wijnands 5 Expires: August 18, 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 14, 2018 15 OSPF Extensions for BIER 16 draft-ietf-bier-ospf-bier-extensions-12.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. 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 August 18, 2018. 53 Copyright Notice 55 Copyright (c) 2018 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 [RFC8296]. 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 [RFC8279]. 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 [RFC8279]. 147 MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies 148 the topology that is associated with the BIER sub-domain. 150 BFR-id: A 2 octet field encoding the BFR-id, as documented in 151 section 2 of [RFC8279]. If the BFR is not locally configured with 152 a valid BFR-id, the value of this field is set to invalid BFR-id 153 per [RFC8279]. 155 BAR: Single octet BIER Algorithm. 0 is the only supported value 156 defined in this document and represents Shortest Path First (SPF) 157 algorithm based on IGP link metric. This is the standard shortest 158 path algorithm as computed by the OSPF protocol. Other values may 159 be defined in the future. 161 Each BFR sub-domain MUST be associated with one and only one OSPF 162 topology that is identified by the MT-ID. If the association between 163 BIER sub-domain and OSPF topology advertised in the BIER sub-TLV by 164 other BFRs is in conflict with the association locally configured on 165 the receiving router, the BIER Sub-TLV MUST be ignored. 167 If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs, 168 the BRF MUST be treated as if it did not advertise a BIER sub-TLV for 169 such sub-domain. 171 All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a 172 given MT-ID and Sub-domain-ID. When such duplication is detected all 173 BFRs advertising duplicates MUST be treated as if they did not 174 advertise a valid BFR-id. 176 The supported algorithm MUST be consistent for all routers supporting 177 a given BFR sub-domain. A router receiving BIER Sub-TLV 178 advertisement with a BAR which does not match the locally configured 179 value MUST report a misconfiguration for the given BIER sub-domain 180 and MUST ignore such BIER sub-TLV. 182 2.2. BIER MPLS Encapsulation Sub-TLV 184 The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV. 185 The BIER MPLS Encapsulation Sub-TLV is used in order to advertise 186 MPLS specific information used for BIER. It MAY appear multiple 187 times in the BIER Sub-TLV. 189 The BIER MPLS Encapsulation Sub-TLV has the following format: 191 0 1 2 3 192 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 1 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 | Type | Length | 195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 196 | Max SI | Label | 197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 198 |BS Len | Reserved | 199 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 Type: 10 203 Length: 4 octets 205 Max SI : A 1 octet field encoding the Maximum Set Identifier 206 (section 1 of [RFC8296]), used in the encapsulation for this BIER 207 sub-domain for this bitstring length. 209 Label: A 3 octet field, where the 20 rightmost bits represent the 210 first label in the label range. The 4 leftmost bits MUST be 211 ignored. 213 Bit String Length: A 4 bits field encoding the supported BitString 214 length associated with this BFR-prefix. The values allowed in 215 this field are specified in section 2 of [RFC8296]. 217 The "label range" is the set of labels beginning with the Label 218 and ending with (Label + (Max SI)). A unique label range is 219 allocated for each BitStream length and Sub-domain-ID. These 220 labels are used for BIER forwarding as described in [RFC8279] and 221 [RFC8296]. 223 The size of the label range is determined by the number of Set 224 Identifiers (SI) (section 1 of [RFC8279]) that are used in the 225 network. Each SI maps to a single label in the label range. The 226 first label is for SI=0, the second label is for SI=1, etc. 228 If same BS length is repeated in multiple BIER MPLS Encapsulation 229 Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be 230 ignored. 232 Label ranges within all BIER MPLS Encapsulation Sub-TLVs advertised 233 by the same BFR MUST NOT overlap. If the overlap is detected, the 234 advertising router MUST be treated as if it did not advertise any 235 BIER sub-TLVs. 237 All advertised labels MUST be valid, otherwise the BIER sub-TLV MUST 238 be ignored. 240 2.3. Flooding scope of BIER Information 242 The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684] 243 that is used for advertising the BIER Sub-TLV is set to area-local. 244 To allow BIER deployment in a multi-area environment, OSPF must 245 propagate BIER information between areas. 247 ( ) ( ) ( ) 248 ( ) ( ) ( ) 249 R1 Area 1 R2 Area 0 R3 Area 2 R4 250 ( ) ( ) ( ) 251 ( ) ( ) ( ) 253 Figure 1: BIER propagation between areas 255 The following procedure is used in order to propagate BIER related 256 information between areas: 258 When an OSPF Area Border Router (ABR) advertises a Type-3 Summary 259 LSA from an intra-area or inter-area prefix to all its attached 260 areas, it will also originate an Extended Prefix Opaque LSA, as 261 described in [RFC7684]. The flooding scope of the Extended Prefix 262 Opaque LSA type will be set to area-local. The route-type in the 263 OSPF Extended Prefix TLV is set to inter-area. When determining 264 whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR 265 will: 267 - Examine its best path to the prefix in the source area and 268 find the advertising router associated with the best path to 269 that prefix. 271 - Determine if such advertising router advertised a BIER Sub- 272 TLV for the prefix. If yes, the ABR will copy the information 273 from such BIER Sub-TLV when advertising BIER Sub-TLV to each 274 attached area. 276 In the Figure 1, R1 advertises a prefix 192.0.2.1/32 in Area 1. 277 It also advertises Extended Prefix Opaque LSA for prefix 278 192.0.2.1/32 and includes BIER Sub-TLV in it. Area Border Router 279 (ABR) R2 calculates the reachability for prefix 192.0.2.1/32 280 inside Area 1 and propagates it to Area 0. When doing so, it 281 copies the entire BIER Sub-TLV (including all its Sub-TLVs) it 282 received from R1 in Area 1 and includes it in the Extended Prefix 283 Opaque LSA it generates for 192.0.2.1/32 in Area 0. ABR R3 284 calculates the reachability for prefix 192.0.2.1/32 inside Area 0 285 and propagates it to Area 2. When doing so, it copies the entire 286 BIER Sub-TLV (including all its Sub-TLVs) it received from R2 in 287 Area 0 and includes it in the Extended Prefix Opaque LSA it 288 generates for 192.0.2.1/32 in Area 2. 290 3. Security Considerations 292 Implementations must assure that malformed TLV and Sub-TLV 293 permutations do not result in errors which cause hard OSPF failures. 295 4. IANA Considerations 297 The document requests three new allocations from the OSPF Extended 298 Prefix sub-TLV registry as defined in [RFC7684]. 300 BIER Sub-TLV: 9 302 BIER MPLS Encapsulation Sub-TLV: 10 304 5. Acknowledgments 306 The authors would like to thank Rajiv Asati, Christian Martin, Greg 307 Shepherd and Eric Rosen for their contribution. 309 6. Normative References 311 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 312 Requirement Levels", BCP 14, RFC 2119, 313 DOI 10.17487/RFC2119, March 1997, 314 . 316 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 317 DOI 10.17487/RFC2328, April 1998, 318 . 320 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 321 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 322 RFC 4915, DOI 10.17487/RFC4915, June 2007, 323 . 325 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 326 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 327 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 328 2015, . 330 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 331 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 332 Explicit Replication (BIER)", RFC 8279, 333 DOI 10.17487/RFC8279, November 2017, 334 . 336 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 337 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 338 for Bit Index Explicit Replication (BIER) in MPLS and Non- 339 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 340 2018, . 342 Authors' Addresses 344 Peter Psenak (editor) 345 Cisco 346 Apollo Business Center 347 Mlynske nivy 43 348 Bratislava 821 09 349 Slovakia 351 Email: ppsenak@cisco.com 353 Nagendra Kumar 354 Cisco 355 7200 Kit Creek Road 356 Research Triangle Park, NC 27709 357 US 359 Email: naikumar@cisco.com 361 IJsbrand Wijnands 362 Cisco 363 De Kleetlaan 6a 364 Diegem 1831 365 Belgium 367 Email: ice@cisco.com 368 Andrew Dolganow 369 Nokia 370 750 Chai Chee Rd 371 06-06 Viva Business Park 372 Singapore 469004 374 Email: andrew.dolganow@nokia.com 376 Tony Przygienda 377 Juniper Networks, Inc. 378 10 Technology Park Drive 379 Westford, MA 01886 380 USA 382 Email: prz@juniper.net 384 Jeffrey Zhang 385 Juniper Networks, Inc. 386 10 Technology Park Drive 387 Westford, MA 01886 388 USA 390 Email: zzhang@juniper.net 392 Sam Aldrin 393 Google, Inc. 394 1600 Amphitheatre Parkway 395 Mountain View, CA 396 USA 398 Email: aldrin.ietf@gmail.com