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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Networking Working Group R. Chen 3 Internet-Draft Zh. Zhang 4 Intended status: Standards Track ZTE Corporation 5 Expires: February 5, 2022 V. Govindan 6 IJ. Wijnands 7 Cisco 8 August 4, 2021 10 BGP Link-State extensions for BIER 11 draft-ietf-bier-bgp-ls-bier-ext-11 13 Abstract 15 Bit Index Explicit Replication (BIER) is an architecture that 16 provides optimal multicast forwarding through a "BIER domain" without 17 requiring intermediate routers to maintain any multicast related per- 18 flow state. BIER also does not require any explicit tree-building 19 protocol for its operation. A multicast data packet enters a BIER 20 domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the 21 BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). 22 The BFIR router adds a BIER header to the packet. The BIER header 23 contains a bitstring in which each bit represents exactly one BFER to 24 forward the packet to. The set of BFERs to which the multicast 25 packet needs to be forwarded is expressed by setting the bits that 26 correspond to those routers in the BIER header. 28 BGP Link-State (BGP-LS) enables the collection of various topology 29 informations from the network, and the topology informations are used 30 by the controller to calculate the fowarding tables and then 31 propagate them onto the BFRs(instead of having each node to calculate 32 on its own) and that can be for both inter-as and intra-as 33 situations. 35 This document specifies extensions to the BGP Link-state address- 36 family in order to advertise the BIER informations. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at https://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on February 5, 2022. 55 Copyright Notice 57 Copyright (c) 2021 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (https://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 73 2. Conventions used in this document . . . . . . . . . . . . . . 3 74 3. BGP-LS Extensions for BIER . . . . . . . . . . . . . . . . . 3 75 3.1. Prefix Attributes TLVs . . . . . . . . . . . . . . . . . 4 76 3.1.1. The BIER information TLV . . . . . . . . . . . . . . 4 77 3.1.2. The BIER MPLS Encapsulation TLV . . . . . . . . . . . 5 78 3.1.3. The BIER non-MPLS Encapsulation TLV . . . . . . . . . 6 79 4. Equivalent IS-IS BIER TLVs/Sub-TLVs . . . . . . . . . . . . . 7 80 5. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs . . . . . . . . . 7 81 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 82 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 83 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 84 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 85 9.1. Normative references . . . . . . . . . . . . . . . . . . 9 86 9.2. Informative references . . . . . . . . . . . . . . . . . 10 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 89 1. Introduction 91 Bit Index Explicit Replication (BIER) is an architecture that 92 provides optimal multicast forwarding through a "BIER domain" without 93 requiring intermediate routers to maintain any multicast related per- 94 flow state. BIER also does not require any explicit tree-building 95 protocol for its operation. A multicast data packet enters a BIER 96 domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the 97 BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). 98 The BFIR router adds a BIER header to the packet. The BIER header 99 contains a bitstring in which each bit represents exactly one BFER to 100 forward the packet to. The set of BFERs to which the multicast 101 packet needs to be forwarded are expressed by setting the bits that 102 correspond to those routers in the BIER header. 104 When BIER is enabled in an IGP domain, BIER-related informations will 105 be advertised via IGP link-state routing protocols. IGP extensions 106 are described in ISIS[[RFC8401]],OSPFv2[[RFC8444]] and 107 OSPFv3[[I-D.ietf-bier-ospfv3-extensions]].The flooding scope for the 108 IGP extensions for BIER is IGP area-wide. by using the IGP alone it 109 is not enough to construct fowarding tables across multiple IGP Area. 111 The BGP-LS address-family/sub-address-family have been defined to 112 allow BGP to carry Link-State informations. This document specifies 113 extensions to the BGP Link-state address-family in order to advertise 114 BIER-specific informations, Similar to BGP-LS Advertisement of IGP 115 Traffic Engineering Performance Metric Extensions([RFC8571]). An 116 external component (e.g., a controller/a PCE(see [RFC4655] for PCE- 117 Based Architecture ,[RFC5440] for PCEP and [RFC5376] for Inter-AS 118 Requirements for the PCEP.))then can learn the BIER informations in 119 the "northbound" direction and calculate BIRT/BIFT and then propagate 120 them onto BFRs (instead of having each BFR to calculate on its own), 121 and that can be for both inter-as and intra-as situations. 123 2. Conventions used in this document 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 127 document are to be interpreted as described in RFC2119. 129 3. BGP-LS Extensions for BIER 131 [RFC8279] defines the BFR - A router that supports BIER is known as a 132 "Bit-Forwarding Router"(BFR), and each BFR MUST be assigned a "BFR- 133 Prefix". A BFR's Prefix MUST be an IP address (either IPv4 or IPv6) 134 of the BFR, and MUST be unique and routable within the BIER domain as 135 described in section 2 of [RFC8279], and then external component 136 (e.g., a controller) need to collect BIER informations of BIER 137 routers are associated with the BFR-Prefix in the "northbound" 138 direction within the BIER domain. 140 Given that the BIER informations are associated with the prefix, the 141 Prefix Attribute TLV [RFC7752] can be used to carry the BIER 142 informations. A new Prefix Attribute TLVs are defined for the 143 encoding of BIER informations. 145 3.1. Prefix Attributes TLVs 147 The following Prefix Attribute TLVs are defined: 149 +------+---------------------------+---------------+ 150 | Type | Description | Section | 151 +------+---------------------------+---------------+ 152 | TBD1 |BIER information | Section 3.1.1 | 153 | TBD2 |BIER MPLS Encapsulation | Section 3.1.2 | 154 | TBD3 |BIER non-MPLS Encapsulation| Section 3.1.3 | 155 +------+---------------------------+---------------+ 157 Table 1:The new Prefix Attribute TLVs 159 3.1.1. The BIER information TLV 161 A new Prefix Attribute TLV (defined in [RFC7752] is defined for 162 distributing BIER informations. The new TLV is called the BIER 163 information TLV. The BIER information TLV may appear multiple times. 165 The following BIER information TLV is defined: 167 0 1 2 3 168 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 1 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | Type | Length | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | sub-domain-id | MT-ID | BFR-id | 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | BAR | IPA | Reserved | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 Figure 2: The BIER information TLV 179 Type: A 2-octet field with value TBD, see IANA Considerations 180 section. 182 Length: 2 octets. 184 Subdomain-id: Unique value identifying the BIER sub-domain, 1 octet. 186 MT-ID: Multi-Topology ID that identifies the topology that is 187 associated with the BIER sub-domain.1 octet. 189 BFR-id: A 2-octet field encoding the BFR-id, as documented in 190 [RFC8279]. If the BFR-id is zero, it means, the advertising router 191 is not advertising any BIER-id.In some environment, BFR-id can be 192 configured by NMS, The BFR-id should be sent to a controller. 194 BAR: A 1-octet field encoding the BIER Algorithm, used to calculate 195 underlay paths to reach BFERs. Values are allocated from the "BIER 196 Algorithms" registry which is defined in [RFC8401]. 198 IPA: A 1-octet field encoding the IGP Algorithm, used to either 199 modify,enhance, or replace the calculation of underlay paths to reach 200 BFERs as defined by the BAR value. Values are from the IGP Algorithm 201 registry. 203 Reserved: MUST be 0 on transmission, ignored on reception. May be 204 used in future versions. 206 If the MT-ID value is outside of the values specified in [RFC4915], 207 the BIER Sub-TLV MUST be ignored. 209 3.1.2. The BIER MPLS Encapsulation TLV 211 The BIER MPLS Encapsulation TLV is used in order to advertise MPLS 212 specific informations used for BIER. It MAY appear multiple times. 214 In some environment, each router allocates its labels, and advertises 215 it to the controller.That solution is simpler as the controller does 216 not need to deal with label allocation. If the controller has to 217 deal with Label allocation , there needs to be a (global) range 218 carved out such there are no conflicts. We can avoid all that by 219 having the router allocate the BIER Label range and advertise it to 220 the controller. 222 The following the BIER MPLS Encapsulation Sub-TLV is defined: 224 0 1 2 3 225 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 1 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 | Type | Length | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | Max SI | Label | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 |BS Len | Reserved | 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 Figure 3: The BIER MPLS Encapsulation TLV 236 Type: A 2-octet field with value TBD, see IANA Considerations 237 section. 239 Length: 2 octets. 241 Max SI: A 1-octet field encoding the maximum Set Identifier(as 242 defined in [RFC8279]), used in the encapsulation for this BIER 243 subdomain for this BitString length. 245 Label: A 3-octet field, where the 20 rightmost bits represent the 246 first label in the label range. 248 BS Len: A 4-bit field field encoding the Bitstring length as per 249 [RFC8296]. 251 BS length in multiple BIER MPLS Encapsulation Sub-TLV inside the same 252 BIER Sub-TLV MUST NOT repeat, otherwise only the first BIER MPLS 253 Encapsulation Sub-TLV with such BS length MUST be used and any 254 subsequent BIER MPLS Encapsulation Sub-TLVs with the same BS length 255 MUST be ignored. 257 3.1.3. The BIER non-MPLS Encapsulation TLV 259 The BIER non-MPLS Encapsulation TLV is used in order to advertise 260 non-MPLS encapsulation(e.g. ethernet encapsulation ) capability and 261 other associated parameters of the encapsulation.It MAY appear 262 multiple times. 264 The following the BIER non-MPLS Encapsulation Sub-TLV is defined: 266 0 1 2 3 267 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 1 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 | Type | Length | 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | Max SI | BIFT-id | 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 273 |BS Len | Reserved | 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 Figure 4: The BIER non-MPLS Encapsulation TLV 278 Type:A 2-octet field with value TBD, see IANA Considerations section. 280 Length: 2 octets. 282 Max SI:A 1-octet field encoding the maximum Set Identifier(as defined 283 in [RFC8279]), used in the encapsulation for this BIER subdomain for 284 this BitString length. 286 BIFT-id:A 3-octet field, where the 20 rightmost bits represent the 287 first BIFT-id in the BIFT-id range. The 4 leftmost bits MUST be 288 ignored. 290 The "BIFT-id range" is the set of 20-bit values beginning with the 291 BIFT-id and ending with (BIFT-id + (Max SI)). A unique BIFT-id range 292 is allocated for each BitString length and sub-domain-id. These 293 BIFT-id's are used for BIER forwarding as described in [RFC8279])and 294 [RFC8296]. 296 Local BitString Length (BS Len): A 4-bit field encoding the Bitstring 297 length as per [RFC8296]. 299 Reserved:SHOULD be set to 0 on transmission and MUST be ignored on 300 reception. 302 4. Equivalent IS-IS BIER TLVs/Sub-TLVs 304 This section illustrates the IS-IS BIER Extensions Sub-TLVs/Sub-Sub- 305 TLVs mapped to the ones defined in this document. 307 The following table illustrates for each BGP-LS TLV, and its 308 equivalence in IS-IS. 310 +--------------+----------------------------+------------------------------------------+ 311 | Descriptio | IS-IS TLV | Reference | 312 | n | /Sub-TLV | | 313 +--------------+----------------------------+------------------------------------------+ 314 | BIER | BIER Info Sub-TLV | [RFC8401] | 315 | information | | | 316 | | | | 317 | BIER MPLS |BIER MPLS Encapsulation | [RFC8401] | 318 | Encapsulation|Sub-Sub-TLV | | 319 | | | | 320 | BIER non-MPLS| BIER non-MPLS Encapsulation| [I-D.ietf-bier-lsr-ethernet-extensions] | 321 | Encapsulation| Sub-Sub-TLV | | 322 +--------------+----------------------------+------------------------------------------+ 324 Table 2:IS-IS BIER Extensions Sub-TLVs/Sub-Sub-TLVs 326 5. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs 328 This section illustrates the BIER Extensions TLVs/Sub-TLVs mapped to 329 the ones defined in this document. 331 The following table illustrates for each BGP-LS TLV, and its 332 equivalence in OSPFv2/OSPFV3. 334 +--------------+-----------------------------+-----------------------------------------+ 335 | Descriptio | OSPFv2/OSPFV3 sub-TLV | Reference | 336 | n | /Sub-Sub-TLV | | 337 +--------------+-----------------------------+-----------------------------------------+ 338 | BIER | BIER Sub-TLV |[RFC8444] & | 339 | information | |[I-D. ietf-bier-ospfv3-extensions | 340 | | | | 341 | BIER MPLS |BIER MPLS Encapsulation |[RFC8444]& | 342 | Encapsulation|Sub-TLV |[I-D. ietf-bier-ospfv3-extensions | 343 | | | | 344 | BIER non-MPLS| BIER non-MPLS Encapsulation |[I-D.ietf-bier-lsr-ethernet-extensions] | 345 | Encapsulation| Sub-TLV | | 346 +--------------+-----------------------------+-----------------------------------------+ 348 Table 3: OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs 350 6. IANA Considerations 352 This document requests assigning code-points from the registry for 353 the new Prefix Attribute TLVs. 355 +-------------------+-----------------------------+-----------------+ 356 | TLV Code Point | Description | Value defined | 357 +-------------------+-----------------------------+-----------------+ 358 | TBD1 | BIER information | this document | 359 +-------------------+-----------------------------+-----------------+ 360 | TBD2 | BIER MPLS Encapsulation | this document | 361 +-------------------+-----------------------------+-----------------+ 362 | TBD3 | BIER non-MPLS Encapsulation | this document | 363 +-------------------+-----------------------------+-----------------+ 365 Table 4: The new Prefix Attribute TLVs 367 7. Security Considerations 369 Procedures and protocol extensions defined in this document do not 370 affect the BGP security model. See the "Security 371 Considerations"section of [RFC4271] for a discussion of BGP 372 security.Security considerations for acquiring and distributing BGP- 373 LS informations are discussed in [RFC7752]. 375 The TLVs introduced in this document are used to propagate the Bit 376 Index Explicit Replication (BIER) defined in [[RFC8401]], [[RFC8444]] 377 , [[I-D.ietf-bier-ospfv3-extensions]] and 378 [[I-D.ietf-bier-lsr-ethernet-extensions]] . These TLVs represent the 379 bier informations associated with the prefix. It is assumed that the 380 IGP instances originating these TLVs will support all the required 381 security and authentication mechanisms in [[RFC8401]], [[RFC8444]] 382 [[I-D.ietf-bier-ospfv3-extensions]] and 383 [[I-D.ietf-bier-lsr-ethernet-extensions]] in order to prevent any 384 security issues when propagating the TLVs into BGP-LS. The 385 advertisement of the link attribute informations defined in this 386 document present no additional risk beyond that associated with the 387 existing link attribute informations already supported in [RFC7752]. 389 8. Acknowledgements 391 The authors thank Peter Psenak, Ketan Talaulikar, Zhaohui Zhang, Gyan 392 Mishra and Benchong Xu and many others for their suggestions and 393 comments. 395 9. References 397 9.1. Normative references 399 [I-D.ietf-bier-lsr-ethernet-extensions] 400 Dhanaraj, S., Yan, G., Wijnands, I., Psenak, P., Zhang, 401 Z., and J. Xie, "LSR Extensions for BIER over Ethernet", 402 draft-ietf-bier-lsr-ethernet-extensions-02 (work in 403 progress), December 2020. 405 [I-D.ietf-bier-ospfv3-extensions] 406 Psenak, P., Nainar, N. K., and I. Wijnands, "OSPFv3 407 Extensions for BIER", draft-ietf-bier-ospfv3-extensions-04 408 (work in progress), May 2021. 410 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 411 Element (PCE)-Based Architecture", RFC 4655, 412 DOI 10.17487/RFC4655, August 2006, 413 . 415 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 416 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 417 RFC 4915, DOI 10.17487/RFC4915, June 2007, 418 . 420 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 421 S. Ray, "North-Bound Distribution of Link-State and 422 Traffic Engineering (TE) Information Using BGP", RFC 7752, 423 DOI 10.17487/RFC7752, March 2016, 424 . 426 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 427 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 428 Explicit Replication (BIER)", RFC 8279, 429 DOI 10.17487/RFC8279, November 2017, 430 . 432 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 433 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 434 for Bit Index Explicit Replication (BIER) in MPLS and Non- 435 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 436 2018, . 438 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 439 Zhang, "Bit Index Explicit Replication (BIER) Support via 440 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 441 . 443 [RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., 444 Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 445 Extensions for Bit Index Explicit Replication (BIER)", 446 RFC 8444, DOI 10.17487/RFC8444, November 2018, 447 . 449 [RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and 450 C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of 451 IGP Traffic Engineering Performance Metric Extensions", 452 RFC 8571, DOI 10.17487/RFC8571, March 2019, 453 . 455 9.2. Informative references 457 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 458 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 459 DOI 10.17487/RFC4271, January 2006, 460 . 462 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 463 Requirements for the Path Computation Element 464 Communication Protocol (PCECP)", RFC 5376, 465 DOI 10.17487/RFC5376, November 2008, 466 . 468 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 469 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 470 DOI 10.17487/RFC5440, March 2009, 471 . 473 Authors' Addresses 475 Ran Chen 476 ZTE Corporation 477 No.50 Software Avenue,Yuhuatai District 478 Nanjing, Jiangsu Province 210012 479 China 481 Phone: +86 025 88014636 482 Email: chen.ran@zte.com.cn 484 Zheng Zhang 485 ZTE Corporation 486 No.50 Software Avenue,Yuhuatai District 487 Nanjing, Jiangsu Province 210012 488 China 490 Email: zhang.zheng@zte.com.cn 492 Vengada Prasad Govindan 493 Cisco 495 Email: venggovi@cisco.com 497 IJsbrand Wijnands 498 Cisco 499 De Kleetlaan 6a 500 Diegem 1831 501 Belgium 503 Email: ice@cisco.com