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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: November 18, 2021 V. Govindan 6 IJ. Wijnands 7 Cisco 8 May 17, 2021 10 BGP Link-State extensions for BIER 11 draft-ietf-bier-bgp-ls-bier-ext-10 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 information from the network, and the topology informations are used 30 by the controller to calculate the fowarding table and then program 31 them onto the BFRs(instead of having each node to calculate on its 32 own) and that can be for both inter-as and intra-as situations. 34 This document specifies extensions to the BGP Link-state address- 35 family in order to advertise BIER informations. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at https://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on November 18, 2021. 54 Copyright Notice 56 Copyright (c) 2021 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (https://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 72 2. Conventions used in this document . . . . . . . . . . . . . . 3 73 3. BGP-LS Extensions for BIER . . . . . . . . . . . . . . . . . 3 74 3.1. Prefix Attributes TLVs . . . . . . . . . . . . . . . . . 4 75 3.1.1. The BIER information TLV . . . . . . . . . . . . . . 4 76 3.1.2. The BIER MPLS Encapsulation TLV . . . . . . . . . . . 5 77 3.1.3. The BIER non-MPLS Encapsulation TLV . . . . . . . . . 6 78 4. Equivalent IS-IS BIER TLVs/Sub-TLVs . . . . . . . . . . . . . 7 79 5. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs . . . . . . . . . 8 80 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 81 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 82 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 83 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 84 9.1. Normative references . . . . . . . . . . . . . . . . . . 9 85 9.2. Informative references . . . . . . . . . . . . . . . . . 11 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 88 1. Introduction 90 Bit Index Explicit Replication (BIER) is an architecture that 91 provides optimal multicast forwarding through a "BIER domain" without 92 requiring intermediate routers to maintain any multicast related per- 93 flow state. BIER also does not require any explicit tree-building 94 protocol for its operation. A multicast data packet enters a BIER 95 domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the 96 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 is 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 information 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 Segment routing is IGP area-wide. by using the IGP 109 alone it is not enough to construct segments across multiple IGP 110 Area. 112 The BGP-LS address-family/sub-address-family have been defined to 113 allow BGP to carry Link-State information. This document specifies 114 extensions to the BGP Link-state address-family in order to advertise 115 BIER-specific informations, Similar to BGP-LS Advertisement of IGP 116 Traffic Engineering Performance Metric Extensions([RFC8571]). An 117 external component (e.g., a controller/a PCE(see [RFC4655] for PCE- 118 Based Architecture ,[RFC5440] for PCEP and [RFC5376] for Inter-AS 119 Requirements for the PCEP.))then can learns the BIER information in 120 the "northbound" direction and calculate BIRT/BIFT and then program 121 them onto BFRs (instead of having each BFR to calculate on its own), 122 and that can be for both inter-as and intra-as situations. 124 2. Conventions used in this document 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 128 document are to be interpreted as described in RFC2119. 130 3. BGP-LS Extensions for BIER 132 [RFC8279] defines the BFR - A router that supports BIER is known as a 133 "Bit-Forwarding Router"(BFR), and each BFR MUST be assigned a "BFR- 134 Prefix". A BFR's BFR-Prefix MUST be an IP address (either IPv4 or 135 IPv6) of the BFR, and MUST be unique and routable within the BIER 136 domain as described in section 2 of [RFC8279], and then external 137 component (e.g., a controller) need to collect BIER information of 138 BIER routers are associated with the BFR-Prefix in the "northbound" 139 direction within the BIER domain. 141 Given that the BIER information is associated with the prefix, the 142 Prefix Attribute TLV [RFC7752] can be used to carry the BIER 143 information. A new Prefix Attribute TLVs are defined for the 144 encoding of BIER information. 146 3.1. Prefix Attributes TLVs 148 The following Prefix Attribute TLVs are defined: 150 +------+---------------------------+---------------+ 151 | Type | Description | Section | 152 +------+---------------------------+---------------+ 153 | TBD |BIER information | Section 3.1.1 | 154 | TBD |BIER MPLS Encapsulation | Section 3.1.2 | 155 | TBD |BIER non-MPLS Encapsulation| Section 3.1.2 | 156 +------+---------------------------+---------------+ 158 Table 1:The new Prefix Attribute TLVs 160 3.1.1. The BIER information TLV 162 A new Prefix Attribute TLV (defined in [RFC7752] is defined for 163 distributing BIER information. The new TLV is called the BIER TLV. 164 The BIER information TLVs may appear multiple times. 166 The following BIER information TLV is defined: 168 0 1 2 3 169 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 1 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | Type | Length | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 | BAR | IPA | subdomain-id | 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | BFR-id | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | Sub-TLVs (variable) | 178 +- -+ 179 | | 181 Figure 2: The BIER information TLV 183 Type: 2 octet field with value TBD, see IANA Considerations section. 185 Length: 2 octet. 187 Reserved: MUST be 0 on transmission, ignored on reception. May be 188 used in future versions. 190 BAR: A 1 octet field encoding the BIER Algorithm, used to calculate 191 underlay paths to reach BFERs. Values are allocated from the "BIER 192 Algorithms" registry which is defined in [RFC8401]. 194 IPA: A 1 octet field encoding the IGP Algorithm, used to either 195 modify,enhance, or replace the calculation of underlay paths to reach 196 BFERs as defined by the BAR value. Values are from the IGP Algorithm 197 registry. 199 Subdomain-id: Unique value identifying the BIER sub-domain, 1 octet. 201 MT-ID: Multi-Topology ID that identifies the topology that is 202 associated with the BIER sub-domain.1 octet. 204 BFR-id: A 2 octet field encoding the BFR-id, as documented in 205 [RFC8279]. If the BFR-id is zero, it means, the advertising router 206 is not advertising any BIER-id.In some environment, BFR-id can be 207 configured by NMS, The BFR-id should be sent to a controller. 209 BS Length: A 1 octet field encoding the Bitstring length as per 210 [RFC8296]. 212 If the MT-ID value is outside of the values specified in [RFC4915], 213 the BIER Sub-TLV MUST be ignored. 215 3.1.2. The BIER MPLS Encapsulation TLV 217 The BIER MPLS Encapsulation TLV is used in order to advertise MPLS 218 specific information used for BIER. It MAY appear multiple times. 220 In some environment, each router allocates its labels, and advertises 221 it to the controller.That solution is simpler as the controller does 222 not need to deal with label allocation. If the controller has to 223 deal with Label allocation , there needs to be a (global) range 224 carved out such there are no conflicts. We can avoid all that by 225 having the router allocate the BIER Label range and advertise it to 226 the controller. 228 The following the BIER MPLS Encapsulation Sub-TLV is defined: 230 0 1 2 3 231 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 1 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | Type | Length | 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 | Max SI | Label | 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 |BS Len | Reserved | 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 240 Figure 3: The BIER MPLS Encapsulation TLV 242 Type: 2 octet field with value TBD, see IANA Considerations section. 244 Length: 2 octet. 246 Max SI: A 1 octet field encoding the maximum Set Identifier(as 247 defined in [RFC8279]), used in the encapsulation for this BIER 248 subdomain for this BitString length. 250 Label: A 3 octet field, where the 20 rightmost bits represent the 251 first label in the label range. 253 BS Length: A 1 octet field encoding the Bitstring length as per 254 [RFC8296] 256 BS length in multiple BIER MPLS Encapsulation Sub-TLV inside the same 257 BIER Sub-TLV MUST NOT repeat, otherwise only the first BIER MPLS 258 Encapsulation Sub-TLV with such BS length MUST be used and any 259 subsequent BIER MPLS Encapsulation Sub-TLVs with the same BS length 260 MUST be ignored. 262 3.1.3. The BIER non-MPLS Encapsulation TLV 264 The BIER non-MPLS Encapsulation TLV is used in order to advertise 265 non-MPLS encapsulation(e.g. ethernet encapsulation ) capability and 266 other associated parameters of the encapsulation.It MAY appear 267 multiple times. 269 The following the BIER non-MPLS Encapsulation Sub-TLV is defined: 271 0 1 2 3 272 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 1 273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 | Type | Length | 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | Max SI | BIFT-id | 277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 |BS Len | Reserved | 279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 281 Figure 4: The BIER non-MPLS Encapsulation TLV 283 Type:2 octet field with value TBD, see IANA Considerations section. 285 Length: 2 octet.. 287 Max SI:A 1 octet field encoding the maximum Set Identifier(as defined 288 in [RFC8279]), used in the encapsulation for this BIER subdomain for 289 this BitString length. 291 BIFT-id:A 3-octet field, where the 20 rightmost bits represent the 292 first BIFT-id in the BIFT-id range. The 4 leftmost bits MUST be 293 ignored. 295 The "BIFT-id range" is the set of 20-bit values beginning with the 296 BIFT-id and ending with (BIFT-id + (Max SI)). A unique BIFT-id range 297 is allocated for each BitString length and sub-domain-id. These 298 BIFT-id's are used for BIER forwarding as described in [RFC8279])and 299 [RFC8296]. 301 Local BitString Length (BS Len): A 4 bit field encoding the Bitstring 302 length as per [RFC8296]. 304 Reserved:SHOULD be set to 0 on transmission and MUST be ignored on 305 reception. 307 4. Equivalent IS-IS BIER TLVs/Sub-TLVs 309 This section illustrate the BIER TLVs mapped to the ones defined in 310 this document. 312 The following table, illustrates for each BGP-LS TLV, its equivalence 313 in IS-IS. 315 +--------------+----------------------------+------------------------------------------+ 316 | Descriptio | IS-IS TLV | Reference | 317 | n | /Sub-TLV | | 318 +--------------+----------------------------+------------------------------------------+ 319 | BIER | BIER Info Sub-TLV | [RFC8401] | 320 | information | | | 321 | | | | 322 | BIER MPLS |BIER MPLS Encapsulation | [RFC8401] | 323 | Encapsulation|Sub-Sub-TLV | | 324 | | | | 325 | BIER non-MPLS| BIER non-MPLS Encapsulation| [I-D.ietf-bier-lsr-ethernet-extensions] | 326 | Encapsulation| Sub-Sub-TLV | | 327 +--------------+----------------------------+------------------------------------------+ 329 Table 2:IS-IS BIER Sub-TLVs/Sub-Sub-TLVs 331 5. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs 333 This section illustrate the BIER TLVs mapped to the ones defined in 334 this document. 336 The following table, illustrates for each BGP-LS TLV, its equivalence 337 in OSPFv2/OSPFV3. 339 +--------------+-----------------------------+-----------------------------------------+ 340 | Descriptio | OSPFv2/OSPFV3 sub-TLV | Reference | 341 | n | /Sub-Sub-TLV | | 342 +--------------+-----------------------------+-----------------------------------------+ 343 | BIER | BIER Sub-TLV |[RFC8444] & | 344 | information | |[I-D. ietf-bier-ospfv3-extensions | 345 | | | | 346 | BIER MPLS |BIER MPLS Encapsulation |[RFC8444]& | 347 | Encapsulation|Sub-TLV |[I-D. ietf-bier-ospfv3-extensions | 348 | | | | 349 | BIER non-MPLS| BIER non-MPLS Encapsulation |[I-D.ietf-bier-lsr-ethernet-extensions] | 350 | Encapsulation| Sub-TLV | | 351 +--------------+-----------------------------+-----------------------------------------+ 353 Table 3: OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs 355 6. IANA Considerations 357 This document requests assigning code-points from the registry for 358 the new Prefix Attribute TLVs. 360 +-------------------+-----------------------------+-----------------+ 361 | TLV Code Point | Description | Value defined | 362 +-------------------+-----------------------------+-----------------+ 363 | TBD | BIER information | this document | 364 +-------------------+-----------------------------+-----------------+ 365 | TBD | BIER MPLS Encapsulation | this document | 366 +-------------------+-----------------------------+-----------------+ 367 | TBD | BIER non-MPLS Encapsulation | this document | 368 +-------------------+-----------------------------+-----------------+ 370 Table 4: The new Prefix Attribute TLV 372 7. Security Considerations 374 Procedures and protocol extensions defined in this document do not 375 affect the BGP security model. See the "Security 376 Considerations"section of [RFC4271] for a discussion of BGP 377 security.Security considerations for acquiring and distributing BGP- 378 LS information are discussed in [RFC7752]. 380 The TLVs introduced in this document are used to propagate the Bit 381 Index Explicit Replication (BIER) defined in [[RFC8401]], [[RFC8444]] 382 , [[I-D.ietf-bier-ospfv3-extensions]] and 383 [[I-D.ietf-bier-lsr-ethernet-extensions]] . These TLVs represent the 384 bier information associated with the prefix. It is assumed that the 385 IGP instances originating these TLVs will support all the required 386 security and authentication mechanisms in [[RFC8401]], [[RFC8444]] 387 [[I-D.ietf-bier-ospfv3-extensions]] and 388 [[I-D.ietf-bier-lsr-ethernet-extensions]] in order to prevent any 389 security issues when propagating the TLVs into BGP-LS. The 390 advertisement of the link attribute information defined in this 391 document presents no additional risk beyond that associated with the 392 existing link attribute information already supported in [RFC7752]. 394 8. Acknowledgements 396 The authors thank Peter Psenak, Ketan Talaulikar, Zhaohui Zhang, Gyan 397 Mishra and Benchong Xu and many others for their suggestions and 398 comments. 400 9. References 402 9.1. Normative references 404 [I-D.ietf-bier-lsr-ethernet-extensions] 405 Dhanaraj, S., Yan, G., Wijnands, I., Psenak, P., Zhang, 406 Z., and J. Xie, "LSR Extensions for BIER over Ethernet", 407 draft-ietf-bier-lsr-ethernet-extensions-02 (work in 408 progress), December 2020. 410 [I-D.ietf-bier-ospfv3-extensions] 411 Psenak, P., Nainar, N. K., and I. Wijnands, "OSPFv3 412 Extensions for BIER", draft-ietf-bier-ospfv3-extensions-03 413 (work in progress), November 2020. 415 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 416 Element (PCE)-Based Architecture", RFC 4655, 417 DOI 10.17487/RFC4655, August 2006, 418 . 420 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 421 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 422 RFC 4915, DOI 10.17487/RFC4915, June 2007, 423 . 425 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 426 S. Ray, "North-Bound Distribution of Link-State and 427 Traffic Engineering (TE) Information Using BGP", RFC 7752, 428 DOI 10.17487/RFC7752, March 2016, 429 . 431 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 432 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 433 Explicit Replication (BIER)", RFC 8279, 434 DOI 10.17487/RFC8279, November 2017, 435 . 437 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 438 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 439 for Bit Index Explicit Replication (BIER) in MPLS and Non- 440 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 441 2018, . 443 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 444 Zhang, "Bit Index Explicit Replication (BIER) Support via 445 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 446 . 448 [RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., 449 Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 450 Extensions for Bit Index Explicit Replication (BIER)", 451 RFC 8444, DOI 10.17487/RFC8444, November 2018, 452 . 454 [RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and 455 C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of 456 IGP Traffic Engineering Performance Metric Extensions", 457 RFC 8571, DOI 10.17487/RFC8571, March 2019, 458 . 460 9.2. Informative references 462 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 463 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 464 DOI 10.17487/RFC4271, January 2006, 465 . 467 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 468 Requirements for the Path Computation Element 469 Communication Protocol (PCECP)", RFC 5376, 470 DOI 10.17487/RFC5376, November 2008, 471 . 473 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 474 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 475 DOI 10.17487/RFC5440, March 2009, 476 . 478 Authors' Addresses 480 Ran Chen 481 ZTE Corporation 482 No.50 Software Avenue,Yuhuatai District 483 Nanjing, Jiangsu Province 210012 484 China 486 Phone: +86 025 88014636 487 Email: chen.ran@zte.com.cn 488 Zheng Zhang 489 ZTE Corporation 490 No.50 Software Avenue,Yuhuatai District 491 Nanjing, Jiangsu Province 210012 492 China 494 Email: zhang.zheng@zte.com.cn 496 Vengada Prasad Govindan 497 Cisco 499 Email: venggovi@cisco.com 501 IJsbrand Wijnands 502 Cisco 503 De Kleetlaan 6a 504 Diegem 1831 505 Belgium 507 Email: ice@cisco.com