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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-08 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: May 2, 2021 K. Talaulikar 6 Cisco Systems 7 S. Aldrin 8 Google, Inc 9 J. Tantsura 10 Apstra 11 G. Mirsky 12 ZTE Corp. 13 October 29, 2020 15 BGP Link-State Extensions for Seamless BFD 16 draft-ietf-idr-bgp-ls-sbfd-extensions-03 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 May 2, 2021. 48 Copyright Notice 50 Copyright (c) 2020 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 . . . . . . . . . . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . . . . 8 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 initiator node needs to know the S-BFD Discriminator of the 92 destination/tail-end node of that service. The link-state routing 93 protocols (IS-IS, OSPF and OSPFv3) have been extended to advertise 94 the S-BFD Discriminators. With this a initiator node can learn the 95 S-BFD discriminator for all nodes within its IGP area/level or 96 optionally within the domain. With networks being divided into 97 multiple IGP domains for scaling and operational considerations, the 98 service endpoints that require end to end S-BFD monitoring often span 99 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 E2E LSP can be created 130 using hierarchical BGP signaled LSPs based on iBGP labeled unicast 131 within each AS, and eBGP labeled unicast to extend the LSP across AS 132 boundaries. This provides a seamless MPLS transport connectivity for 133 any two service end-points across the entire domain. In order to 134 detect failures for such end to end services and trigger faster 135 protection and/or re-routing, S-BFD MAY be used for the Service Layer 136 (e.g. for MPLS VPNs, PW, etc. ) or the Transport Layer monitoring. 137 This brings up the need for setting up S-BFD session spanning across 138 AS domains. 140 In a similar Segment Routing (SR) [RFC8402] multi-domain network, an 141 end to end SR Policy [I-D.ietf-spring-segment-routing-policy] path 142 may be provisioned between service end-points across domains either 143 via local provisioning or by a controller or signalled from a Path 144 Computation Engine (PCE). Monitoring using S-BFD can similarly be 145 setup for such a SR Policy. 147 Extending the automatic discovery of S-BFD discriminators of nodes 148 from within the IGP domain to across the administrative domain using 149 BGP-LS enables setting up of S-BFD sessions on demand across IGP 150 domains. The S-BFD discriminators for service end point nodes MAY be 151 learnt by the PCE or a controller via the BGP-LS feed that it gets 152 from across IGP domains and it can signal or provision the remote 153 S-BFD discriminator on the initiator node on demand when S-BFD 154 monitoring is required. The mechanisms for the signaling of the 155 S-BFD discriminator from the PCE/controller to the initiator node and 156 setup of the S-BFD session is outside the scope of this document. 158 Additionally, the service end-points themselves MAY also learn the 159 S-BFD discriminator of the remote nodes themselves by receiving the 160 BGP-LS feed via a route reflector (RR) or a centralized BGP Speaker 161 that is consolidating the topology information across the domains. 162 The initiator node can then itself setup the S-BFD session to the 163 remote node without a controller/PCE assistance. 165 While this document takes examples of MPLS and SR paths, the S-BFD 166 discriminator advertisement mechanism is applicable for any S-BFD 167 use-case in general. 169 4. BGP-LS Extensions for S-BFD Discriminator 171 The BGP-LS [RFC7752] specifies the Node NLRI for advertisement of 172 nodes and their attributes using the BGP-LS Attribute. The S-BFD 173 discriminators of a node are considered as its node level attribute 174 and advertised as such. 176 This document defines a new BGP-LS Attribute TLV called the S-BFD 177 Discriminators TLV and its format is as follows: 179 0 1 2 3 180 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 1 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 | Type | Length | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 | Discriminator 1 | 185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 186 | Discriminator 2 (Optional) | 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 | ... | 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 | Discriminator n (Optional) | 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 193 Figure 1: S-BFD Discriminators TLV 195 where: 197 o Type: 1032 199 o Length: variable. Minimum of 4 octets and increments of 4 octets 200 there on for each additional discriminator 202 o Discriminators : multiples of 4 octets, each carrying a S-BFD 203 local discriminator value of the node. At least one discriminator 204 MUST be included in the TLV. 206 The S-BFD Discriminators TLV can only be added to the BGP-LS 207 Attribute associated with the Node NLRI that originates the 208 corresponding underlying IGP TLV/sub-TLV as described below. This 209 information is derived from the protocol specific advertisements as 210 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-08 (work in progress), 325 July 2020. 327 [RFC5706] Harrington, D., "Guidelines for Considering Operations and 328 Management of New Protocols and Protocol Extensions", 329 RFC 5706, DOI 10.17487/RFC5706, November 2009, 330 . 332 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 333 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 334 . 336 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 337 Decraene, B., Litkowski, S., and R. Shakir, "Segment 338 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 339 July 2018, . 341 Authors' Addresses 343 Zhenbin Li 344 Huawei 345 Huawei Bld., No.156 Beiqing Rd. 346 Beijing 100095 347 China 349 Email: lizhenbin@huawei.com 351 Shunwan Zhuang 352 Huawei 353 Huawei Bld., No.156 Beiqing Rd. 354 Beijing 100095 355 China 357 Email: zhuangshunwan@huawei.com 358 Ketan Talaulikar 359 Cisco Systems 360 India 362 Email: ketant@cisco.com 364 Sam Aldrin 365 Google, Inc 367 Email: aldrin.ietf@gmail.com 369 Jeff Tantsura 370 Apstra 372 Email: jefftant.ietf@gmail.com 374 Greg Mirsky 375 ZTE Corp. 377 Email: gregimirsky@gmail.com