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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSVR Working Group J. Dong 3 Internet-Draft Z. Li 4 Intended status: Standards Track H. Wang 5 Expires: August 26, 2021 Huawei Technologies 6 February 22, 2021 8 BGP SPF for Virtual Transport Network (VTN) 9 draft-dong-lsvr-bgp-spf-vtn-00 11 Abstract 13 A Virtual Transport Network (VTN) is a virtual underlay network which 14 consists of a customized network topology and a set of network 15 resource allocated from the physical network. In a network, multiple 16 VTNs can be created to meet different service requirements, and 17 services may be mapped to the same or different VTNs. 19 In networks where BGP Shortest Path First (SPF) is used to distribute 20 the link-state information among network nodes, the information of 21 VTNs needs to be distributed along with the basic network 22 information. This document specifies the BGP SPF mechanisms with 23 necessary extensions to distribute the VTN information and perform 24 VTN-specific path computaton. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on August 26, 2021. 43 Copyright Notice 45 Copyright (c) 2021 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 62 2. Applicability of VTN related BGP-LS Extensions to BGP SPF . . 3 63 2.1. Reuse of BGP-LS TLVs for BGP SPF VTN . . . . . . . . . . 3 64 2.2. VTN Topology and Resource Distribution . . . . . . . . . 5 65 3. SPF Calculation for VTNs . . . . . . . . . . . . . . . . . . 5 66 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 68 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 69 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 71 7.2. Informative References . . . . . . . . . . . . . . . . . 7 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 74 1. Introduction 76 The concept of Virtual Transport Network (VTN) is introduced in 77 [I-D.ietf-teas-enhanced-vpn]. A VTN is a virtual underlay network 78 which has customized network topology and a set of dedicated or 79 shared network resources. In a network, different VTNs may be 80 created to meet different service requirements, and services can be 81 mapped to the same or different VTNs. 83 [I-D.ietf-spring-sr-for-enhanced-vpn] describes the use of resource- 84 aware segments [I-D.ietf-spring-resource-aware-segments] to build SR 85 based VTNs. The SIDs of each VTN and the associated topology and 86 resource attributes need to be distributed using the control plane. 87 [I-D.dong-lsr-sr-enhanced-vpn] specifies the IGP mechanism and 88 extensions to build a set of SR based VTNs. 89 [I-D.dong-idr-bgpls-sr-enhanced-vpn] further specifies the BGP-LS 90 mechanisms and extensions to advertise the VTN information in each 91 domain and the VTN information on the inter-domain links to the 92 network controller, so that the controller could use the collected 93 information to build the inter-domain SR VTNs. 95 In networks where BGP SPF is used to distribute the link-state 96 information among network nodes, the VTN information needs to be 97 distributed along with the basic network link state and TE 98 information. And comparing with the Internal Gateway Protocols 99 (IGPs), BGP SPF may have some advantage in supporting a relatively 100 large number of VTNs. This document specifies the BGP SPF mechanisms 101 with necessary extensions to advertise the information of VTNs. The 102 proposed mechanism is applicable to segment routing with MPLS data 103 plane (SR-MPLS), segment routing with IPv6 data plane (SRv6), and 104 native IPv6 data plane. 106 1.1. Requirements Language 108 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 109 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 110 "OPTIONAL" in this document are to be interpreted as described in 111 BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they 112 appear in all capitals, as shown here. 114 2. Applicability of VTN related BGP-LS Extensions to BGP SPF 116 2.1. Reuse of BGP-LS TLVs for BGP SPF VTN 118 As described in [I-D.ietf-lsvr-bgp-spf], the NLRI and TLVs of BGP-LS 119 can be reused by BGP SPF, this section describes the TLVs which are 120 defined in BGP-LS and can be reused in BGP SPF for the distribution 121 of VTN related information. 123 According to [I-D.ietf-teas-enhanced-vpn], a virtual transport 124 network (VTN) has a customized network topology and a set of 125 dedicated or shared network resources. Thus a VTN can be defined as 126 the combination of a set of network attributes, including the 127 topology attribute and the network resource attribute. A VTN is 128 associated with a Multi-Topology ID (MT-ID) and/or an Algorithm ID 129 which are used to define the VTN topology and path computation 130 constraints. In some cases, each VTN may be associated with a 131 separate MT-ID or a Flex-Algo ID. When the amount of VTNs in a 132 network is large, as described in 133 [I-D.dong-teas-enhanced-vpn-vtn-scalability], multiple VTNs may be 134 associated with the same topology and/or algorithm, so that the 135 amount of topology-specific path computation can be shared by a group 136 of VTNs, this could help to reduce the computation overhead in the 137 control plane. 139 [I-D.ietf-lsvr-bgp-spf] does not cover the usage of Multi-Topology or 140 Flex-Algo with BGP SPF. While the mechanism in this document is 141 based on Multi-Topology [RFC4915][RFC5120] or Flex-Algo 142 [I-D.ietf-lsr-flex-algo] with BGP SPF for topology and/or algorithm 143 -specific link-state information distribution and path computation. 144 For this purpose, the Multi-topology TLV as defined in 145 [I-D.ietf-idr-rfc7752bis], the SR Algorithm TLV as defined 146 [I-D.ietf-idr-bgp-ls-segment-routing-ext], and the Flex-Algo 147 Definition TLV as defined in [I-D.ietf-idr-bgp-ls-flex-algo] are 148 reused for BGP SPF. 150 [I-D.ietf-lsvr-bgp-spf] does not explicitly describes the usage with 151 Segment Routing data plane. To build SR based VTN, the SR-MPLS and 152 SRv6 TLVs as defined in [I-D.ietf-idr-bgp-ls-segment-routing-ext] and 153 [I-D.ietf-idr-bgpls-srv6-ext] are reused for BGP SPF. 155 The VTN extensions to BGP-LS as defined in 156 [I-D.dong-idr-bgpls-sr-enhanced-vpn] applies to BGP SPF as well. 157 This section lists the TLVs which are reused by BGP SPF, the detailed 158 format of the TLVs are described in 159 [I-D.dong-idr-bgpls-sr-enhanced-vpn]. 161 The BGP-LS Attribute TLVs which are defined in 162 [I-D.dong-idr-bgpls-sr-enhanced-vpn] and reused with BGP-LS-SPF SAFI 163 are listed as below: 165 o Virtual Transport Network Definition (VTND) TLV: This is used to 166 advertise the association between the VTN and the topology ID and/ 167 or algorithm ID. It can be carried in BGP-LS attribute associated 168 with a Node NLRI. 170 o VTN ID TLV: This is used to describe the identifiers of one or 171 more VTNs a link belongs to. It can be carried in BGP-LS 172 attribute which is associated with a Link NLRI, or it could be 173 carried as a sub-TLV in the L2 Bundle Member Attribute TLV. 175 o Link Attribute Flags TLV: This is used to specify the 176 characteristics of a link, its functionality is similar to the IS- 177 IS Link Attribute sub-TLV defined in [RFC5029]. It can be carried 178 in BGP-LS attribute which is associated with a Link NLRI, or it 179 could be carried as a sub-TLV in the L2 Bundle Member Attribute 180 TLV. 182 o VTN-specific prefix-SID TLV: This is used to advertise the prefix- 183 SID and its associated VTN. It can be carried in BGP-LS attribute 184 which is associated with a Prefix NLRI. 186 o VTN-specific Adj-SID TLV: This is used to advertise the adj-SID 187 and its associated VTN. It can be carried in BGP-LS attribute of 188 the associated Link NLRI. 190 Further BGP-LS TLVs may be defined in 191 [I-D.dong-idr-bgpls-sr-enhanced-vpn], their usage with BGP SPF will 192 be specified in a future version of this document. 194 2.2. VTN Topology and Resource Distribution 196 In network scenarios where each VTN is associated with a unique MT- 197 ID, The BGP-LS mechanisms used to distribute the VTN topology and 198 resource information to the network controller are described in 199 [I-D.xie-idr-bgpls-sr-vtn-mt]. Such mechanism can be reused for the 200 distribution of VTN information with BGP SPF. 202 In network scenarios where each VTN is associated with a unique Flex- 203 Algo ID, The BGP-LS mechanisms used to distribute the VTN topology 204 and resource information to the network controller are described in 205 [I-D.zhu-idr-bgpls-sr-vtn-flexalgo]. Such mechanism can be reused 206 for the distribution of VTN information with BGP SPF. 208 In network scenarios where multiple VTNs are associated with the same 209 tuple, while each VTN has different resource 210 attributes, the BGP-LS mechanisms which can be used to distribute the 211 VTN topology and resource information to the network controller are 212 described in [I-D.dong-idr-bgpls-sr-enhanced-vpn]. Such mechanism 213 can be reused for the distribution of VTN information with BGP SPF. 215 The Sequence Number TLV as defined in [I-D.ietf-lsvr-bgp-spf] MUST be 216 carried in the BGP-LS attribute associated with the BGP-LS-SPF NLRI. 217 If the Sequence-Number TLV is not received then the corresponding 218 Link NLRI is considered as malformed and MUST be handled as 'Treat- 219 as- withdraw'. An implementation MAY log an error for further 220 analysis. 222 3. SPF Calculation for VTNs 224 [I-D.ietf-lsvr-bgp-spf] describes the mechanisms of using the BGP-LS- 225 SPF Node, Link, and Prefix NLRI for shortest path computation. With 226 the introduction of VTN, the same mechanism is used for the shortest 227 path computation of each VTN. The path computation for a VTN is 228 based on the topology attributes and the constraints specified with 229 the MT-ID and/or Algorithm ID associated with the VTN. When multiple 230 VTNs are associated with the same topology, the result of the 231 shortest path computation based on that topology could be shared by 232 these VTNs. 234 4. Security Considerations 236 This document introduces no additional security vulnerabilities to 237 BGP SPF. 239 The mechanism proposed in this document is subject to the same 240 vulnerabilities as any other protocol that relies on BGP SPF. 242 5. IANA Considerations 244 This document request no IANA actions. 246 6. Acknowledgments 248 TBD 250 7. References 252 7.1. Normative References 254 [I-D.dong-idr-bgpls-sr-enhanced-vpn] 255 Dong, J., Hu, Z., Li, Z., Tang, X., and R. Pang, "BGP-LS 256 Extensions for Segment Routing based Enhanced VPN", draft- 257 dong-idr-bgpls-sr-enhanced-vpn-02 (work in progress), June 258 2020. 260 [I-D.ietf-idr-bgp-ls-flex-algo] 261 Talaulikar, K., Psenak, P., Zandi, S., and G. Dawra, 262 "Flexible Algorithm Definition Advertisement with BGP 263 Link-State", draft-ietf-idr-bgp-ls-flex-algo-05 (work in 264 progress), November 2020. 266 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 267 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 268 and M. Chen, "BGP Link-State extensions for Segment 269 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 270 (work in progress), June 2019. 272 [I-D.ietf-idr-bgpls-srv6-ext] 273 Dawra, G., Filsfils, C., Talaulikar, K., Chen, M., 274 daniel.bernier@bell.ca, d., and B. Decraene, "BGP Link 275 State Extensions for SRv6", draft-ietf-idr-bgpls- 276 srv6-ext-05 (work in progress), November 2020. 278 [I-D.ietf-idr-rfc7752bis] 279 Talaulikar, K., "Distribution of Link-State and Traffic 280 Engineering Information Using BGP", draft-ietf-idr- 281 rfc7752bis-05 (work in progress), November 2020. 283 [I-D.ietf-lsvr-bgp-spf] 284 Patel, K., Lindem, A., Zandi, S., and W. Henderickx, "BGP 285 Link-State Shortest Path First (SPF) Routing", draft-ietf- 286 lsvr-bgp-spf-12 (work in progress), January 2021. 288 [I-D.ietf-spring-resource-aware-segments] 289 Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, 290 Z., and F. Clad, "Introducing Resource Awareness to SR 291 Segments", draft-ietf-spring-resource-aware-segments-01 292 (work in progress), January 2021. 294 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 295 Requirement Levels", BCP 14, RFC 2119, 296 DOI 10.17487/RFC2119, March 1997, 297 . 299 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 300 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 301 May 2017, . 303 7.2. Informative References 305 [I-D.dong-lsr-sr-enhanced-vpn] 306 Dong, J., Hu, Z., Li, Z., Tang, X., Pang, R., JooHeon, L., 307 and S. Bryant, "IGP Extensions for Segment Routing based 308 Enhanced VPN", draft-dong-lsr-sr-enhanced-vpn-04 (work in 309 progress), June 2020. 311 [I-D.dong-teas-enhanced-vpn-vtn-scalability] 312 Dong, J., Li, Z., Qin, F., and G. Yang, "Scalability 313 Considerations for Enhanced VPN (VPN+)", draft-dong-teas- 314 enhanced-vpn-vtn-scalability-01 (work in progress), 315 November 2020. 317 [I-D.ietf-lsr-flex-algo] 318 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 319 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 320 algo-13 (work in progress), October 2020. 322 [I-D.ietf-spring-sr-for-enhanced-vpn] 323 Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, 324 Z., and F. Clad, "Segment Routing based Virtual Transport 325 Network (VTN) for Enhanced VPN", February 2021, 326 . 329 [I-D.ietf-teas-enhanced-vpn] 330 Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A 331 Framework for Enhanced Virtual Private Networks (VPN+) 332 Service", draft-ietf-teas-enhanced-vpn-06 (work in 333 progress), July 2020. 335 [I-D.xie-idr-bgpls-sr-vtn-mt] 336 Xie, C., Li, C., Dong, J., and Z. Li, "BGP-LS with Multi- 337 topology for Segment Routing based Virtual Transport 338 Networks", draft-xie-idr-bgpls-sr-vtn-mt-02 (work in 339 progress), January 2021. 341 [I-D.zhu-idr-bgpls-sr-vtn-flexalgo] 342 Zhu, Y., Dong, J., and Z. Hu, "BGP-LS with Flex-Algo for 343 Segment Routing based Virtual Transport Networks", draft- 344 zhu-idr-bgpls-sr-vtn-flexalgo-00 (work in progress), March 345 2020. 347 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 348 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 349 RFC 4915, DOI 10.17487/RFC4915, June 2007, 350 . 352 [RFC5029] Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link 353 Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029, 354 September 2007, . 356 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 357 Topology (MT) Routing in Intermediate System to 358 Intermediate Systems (IS-ISs)", RFC 5120, 359 DOI 10.17487/RFC5120, February 2008, 360 . 362 Authors' Addresses 364 Jie Dong 365 Huawei Technologies 366 Huawei Campus, No. 156 Beiqing Road 367 Beijing 100095 368 China 370 Email: jie.dong@huawei.com 371 Zhenbin Li 372 Huawei Technologies 373 Huawei Campus, No. 156 Beiqing Road 374 Beijing 100095 375 China 377 Email: lizhenbin@huawei.com 379 Haibo Wang 380 Huawei Technologies 381 Huawei Campus, No. 156 Beiqing Road 382 Beijing 100095 383 China 385 Email: rainsword.wang@huawei.com