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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-09 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Inter-Domain Routing Z. Li 3 Internet-Draft S. Zhuang 4 Intended status: Standards Track Huawei 5 Expires: September 9, 2021 K. Talaulikar, Ed. 6 Cisco Systems, Inc. 7 S. Aldrin 8 Google, Inc 9 J. Tantsura 10 Apstra 11 G. Mirsky 12 ZTE Corp. 13 March 8, 2021 15 BGP Link-State Extensions for Seamless BFD 16 draft-ietf-idr-bgp-ls-sbfd-extensions-05 18 Abstract 20 Seamless Bidirectional Forwarding Detection (S-BFD) defines a 21 simplified mechanism to use Bidirectional Forwarding Detection (BFD) 22 with large portions of negotiation aspects eliminated, thus providing 23 benefits such as quick provisioning as well as improved control and 24 flexibility to network nodes initiating the path monitoring. The 25 link-state routing protocols (IS-IS and OSPF) have been extended to 26 advertise the Seamless BFD (S-BFD) Discriminators. 28 This draft defines extensions to the BGP Link-state address-family to 29 carry the S-BFD Discriminators information via BGP. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on September 9, 2021. 48 Copyright Notice 50 Copyright (c) 2021 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Problem and Requirement . . . . . . . . . . . . . . . . . . . 3 69 4. BGP-LS Extensions for S-BFD Discriminator . . . . . . . . . . 4 70 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 71 6. Manageability Considerations . . . . . . . . . . . . . . . . 6 72 6.1. Operational Considerations . . . . . . . . . . . . . . . 6 73 6.2. Management Considerations . . . . . . . . . . . . . . . . 6 74 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 75 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 76 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 77 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 78 9.2. Informative References . . . . . . . . . . . . . . . . . 7 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 81 1. Introduction 83 Seamless Bidirectional Forwarding Detection (S-BFD) [RFC7880] defines 84 a simplified mechanism to use Bidirectional Forwarding Detection 85 (BFD) [RFC5880] with large portions of negotiation aspects 86 eliminated, thus providing benefits such as quick provisioning as 87 well as improved control and flexibility to network nodes initiating 88 the path monitoring. 90 For monitoring of a service path end-to-end via S-BFD, the headend 91 node (i.e. Initiator) needs to know the S-BFD Discriminator of the 92 destination/tail-end node (i.e. Responder) of that service. The 93 link-state routing protocols (IS-IS, OSPF and OSPFv3) have been 94 extended to advertise the S-BFD Discriminators. With this a 95 Initiator can learn the S-BFD discriminator for all Responders within 96 its IGP area/level, or optionally within the domain. With networks 97 being divided into multiple IGP domains for scaling and operational 98 considerations, the service endpoints that require end to end S-BFD 99 monitoring often span across IGP domains. 101 BGP Link-State (BGP-LS) [RFC7752] enables the collection and 102 distribution of IGP link-state topology information via BGP sessions 103 across IGP areas/levels and domains. The S-BFD discriminator(s) of a 104 node can thus be distributed along with the topology information via 105 BGP-LS across IGP domains and even across multiple Autonomous Systems 106 (AS) within an administrative domain. 108 This draft defines extensions to BGP-LS for carrying the S-BFD 109 Discriminators information. 111 1.1. Requirements Language 113 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 114 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 115 "OPTIONAL" in this document are to be interpreted as described in BCP 116 14 [RFC2119] [RFC8174] when, and only when, they appear in all 117 capitals, as shown here. 119 2. Terminology 121 This memo makes use of the terms defined in [RFC7880]. 123 3. Problem and Requirement 125 Seamless MPLS [I-D.ietf-mpls-seamless-mpls] extends the core domain 126 and integrates aggregation and access domains into a single MPLS 127 domain. In a large network, the core and aggregation networks can be 128 organized as different ASes. Although the core and aggregation 129 networks are segmented into different ASes, an end-to-end label 130 switched path (LSP) can be created using hierarchical BGP signaled 131 LSPs based on internal-BGP (IBGP) labeled unicast within each AS, and 132 external-BGP (EBGP) labeled unicast to extend the LSP across AS 133 boundaries. This provides a seamless MPLS transport connectivity for 134 any two service end-points across the entire domain. In order to 135 detect failures for such end to end services and trigger faster 136 protection and/or re-routing, S-BFD MAY be used for the Service Layer 137 (e.g. for MPLS VPNs, pseudowires, etc. ) or the Transport Layer 138 monitoring. This creates the need for setting up S-BFD session 139 spanning across AS domains. 141 In a similar Segment Routing (SR) [RFC8402] multi-domain network, an 142 end to end SR Policy [I-D.ietf-spring-segment-routing-policy] path 143 may be provisioned between service end-points across domains either 144 via local provisioning, or by a controller or signalled from a Path 145 Computation Engine (PCE) [RFC4655] . Monitoring using S-BFD can 146 similarly be setup for such a SR Policy. 148 Extending the automatic discovery of S-BFD discriminators of nodes 149 from within the IGP domain to cross an administrative domain using 150 BGP-LS enables creating S-BFD sessions on demand across IGP domains. 151 The S-BFD discriminators for service end point nodes MAY be learnt by 152 the PCE or a controller via the BGP-LS feed that it gets from across 153 IGP domains, and it can signal or provision the remote S-BFD 154 discriminator on the Initiator on demand when S-BFD monitoring is 155 required. The mechanisms for the signaling of the S-BFD 156 discriminator from the PCE/controller to the Initiator and setup of 157 the S-BFD session are outside the scope of this document. 159 Additionally, the service end-points themselves MAY also learn the 160 S-BFD discriminator of the remote nodes themselves by receiving the 161 BGP-LS feed via a route reflector (RR) [RFC4456] or a centralized BGP 162 Speaker that is consolidating the topology information across the 163 domains. The Initiator can then itself setup the S-BFD session to 164 the remote node without a controller/PCE assistance. 166 While this document takes examples of MPLS and SR paths, the S-BFD 167 discriminator advertisement mechanism is applicable for any S-BFD 168 use-case in general. 170 4. BGP-LS Extensions for S-BFD Discriminator 172 The BGP-LS [RFC7752] specifies the Node NLRI for advertisement of 173 nodes and their attributes using the BGP-LS Attribute. The S-BFD 174 discriminators of a node are considered as its node level attribute 175 and advertised as such. 177 This document defines a new BGP-LS Attribute TLV called the S-BFD 178 Discriminators TLV, and its format is as follows: 180 0 1 2 3 181 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 1 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | Type | Length | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Discriminator 1 | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | Discriminator 2 (Optional) | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 189 | ... | 190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 191 | Discriminator n (Optional) | 192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 Figure 1: S-BFD Discriminators TLV 196 where: 198 o Type: 1032 (early allocation by IANA) 200 o Length: variable. Minimum of 4 octets and increments of 4 octets 201 there on for each additional discriminator 203 o Discriminators : multiples of 4 octets, each carrying a S-BFD 204 local discriminator value of the node. At least one discriminator 205 MUST be included in the TLV. 207 The S-BFD Discriminators TLV can be added to the BGP-LS Attribute 208 associated with the Node NLRI that originates the corresponding 209 underlying IGP TLV/sub-TLV as described below. This information is 210 derived from the protocol specific advertisements as below.. 212 o IS-IS, as defined by the S-BFD Discriminators sub-TLV in 213 [RFC7883]. 215 o OSPFv2/OSPFv3, as defined by the S-BFD Discriminators TLV in 216 [RFC7884]. 218 When the node is not running any of the IGPs but running a protocol 219 like BGP, then the locally provisioned S-BFD discriminators of the 220 node MAY be originated as part of the BGP-LS attribute within the 221 Node NLRI corresponding to the local node. 223 5. IANA Considerations 225 This document requests assigning code-points from the registry "BGP- 226 LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute 227 TLVs" based on table below which reflects the values assigned via the 228 early allocation process. The column "IS-IS TLV/Sub-TLV" defined in 229 the registry does not require any value and should be left empty. 231 +---------------+--------------------------+----------+ 232 | Code Point | Description | Length | 233 +---------------+--------------------------+----------+ 234 | 1032 | S-BFD Discriminators TLV | variable | 235 +---------------+--------------------------+----------+ 237 6. Manageability Considerations 239 This section is structured as recommended in [RFC5706]. 241 The new protocol extensions introduced in this document augment the 242 existing IGP topology information that was distributed via [RFC7752]. 243 Procedures and protocol extensions defined in this document do not 244 affect the BGP protocol operations and management other than as 245 discussed in the Manageability Considerations section of [RFC7752]. 246 Specifically, the malformed NLRIs attribute tests in the Fault 247 Management section of [RFC7752] now encompass the new TLVs for the 248 BGP-LS NLRI in this document. 250 6.1. Operational Considerations 252 No additional operation considerations are defined in this document. 254 6.2. Management Considerations 256 No additional management considerations are defined in this document. 258 7. Security Considerations 260 The new protocol extensions introduced in this document augment the 261 existing IGP topology information that was distributed via [RFC7752]. 262 Procedures and protocol extensions defined in this document do not 263 affect the BGP security model other than as discussed in the Security 264 Considerations section of [RFC7752]. More specifically the aspects 265 related to limiting the nodes and consumers with which the topology 266 information is shared via BGP-LS to trusted entities within an 267 administrative domain. 269 Advertising the S-BFD Discriminators via BGP-LS makes it possible for 270 attackers to initiate S-BFD sessions using the advertised 271 information. The vulnerabilities this poses and how to mitigate them 272 are discussed in [RFC7752]. 274 8. Acknowledgements 276 The authors would like to thank Nan Wu for his contributions to this 277 work and Gunter Van De Velde for his review. 279 9. References 281 9.1. Normative References 283 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 284 Requirement Levels", BCP 14, RFC 2119, 285 DOI 10.17487/RFC2119, March 1997, 286 . 288 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 289 S. Ray, "North-Bound Distribution of Link-State and 290 Traffic Engineering (TE) Information Using BGP", RFC 7752, 291 DOI 10.17487/RFC7752, March 2016, 292 . 294 [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. 295 Pallagatti, "Seamless Bidirectional Forwarding Detection 296 (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016, 297 . 299 [RFC7883] Ginsberg, L., Akiya, N., and M. Chen, "Advertising 300 Seamless Bidirectional Forwarding Detection (S-BFD) 301 Discriminators in IS-IS", RFC 7883, DOI 10.17487/RFC7883, 302 July 2016, . 304 [RFC7884] Pignataro, C., Bhatia, M., Aldrin, S., and T. Ranganath, 305 "OSPF Extensions to Advertise Seamless Bidirectional 306 Forwarding Detection (S-BFD) Target Discriminators", 307 RFC 7884, DOI 10.17487/RFC7884, July 2016, 308 . 310 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 311 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 312 May 2017, . 314 9.2. Informative References 316 [I-D.ietf-mpls-seamless-mpls] 317 Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz, 318 M., and D. Steinberg, "Seamless MPLS Architecture", draft- 319 ietf-mpls-seamless-mpls-07 (work in progress), June 2014. 321 [I-D.ietf-spring-segment-routing-policy] 322 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 323 P. Mattes, "Segment Routing Policy Architecture", draft- 324 ietf-spring-segment-routing-policy-09 (work in progress), 325 November 2020. 327 [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route 328 Reflection: An Alternative to Full Mesh Internal BGP 329 (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006, 330 . 332 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 333 Element (PCE)-Based Architecture", RFC 4655, 334 DOI 10.17487/RFC4655, August 2006, 335 . 337 [RFC5706] Harrington, D., "Guidelines for Considering Operations and 338 Management of New Protocols and Protocol Extensions", 339 RFC 5706, DOI 10.17487/RFC5706, November 2009, 340 . 342 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 343 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 344 . 346 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 347 Decraene, B., Litkowski, S., and R. Shakir, "Segment 348 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 349 July 2018, . 351 Authors' Addresses 353 Zhenbin Li 354 Huawei 355 Huawei Bld., No.156 Beiqing Rd. 356 Beijing 100095 357 China 359 Email: lizhenbin@huawei.com 361 Shunwan Zhuang 362 Huawei 363 Huawei Bld., No.156 Beiqing Rd. 364 Beijing 100095 365 China 367 Email: zhuangshunwan@huawei.com 368 Ketan Talaulikar (editor) 369 Cisco Systems, Inc. 370 India 372 Email: ketant@cisco.com 374 Sam Aldrin 375 Google, Inc 377 Email: aldrin.ietf@gmail.com 379 Jeff Tantsura 380 Apstra 382 Email: jefftant.ietf@gmail.com 384 Greg Mirsky 385 ZTE Corp. 387 Email: gregimirsky@gmail.com