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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-29) exists of draft-ietf-lsvr-bgp-spf-06 == Outdated reference: A later version (-17) exists of draft-acee-idr-lldp-peer-discovery-05 == Outdated reference: A later version (-18) exists of draft-ietf-lsr-dynamic-flooding-03 == Outdated reference: A later version (-12) exists of draft-ietf-lsvr-l3dl-02 == Outdated reference: A later version (-12) exists of draft-xu-idr-neighbor-autodiscovery-11 -- Obsolete informational reference (is this intentional?): RFC 7752 (Obsoleted by RFC 9552) Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSVR K. Patel 3 Internet-Draft Arrcus, Inc. 4 Intended status: Informational A. Lindem 5 Expires: May 5, 2020 Cisco Systems 6 S. Zandi 7 G. Dawra 8 Linkedin 9 November 2, 2019 11 Usage and Applicability of Link State Vector Routing in Data Centers 12 draft-ietf-lsvr-applicability-04 14 Abstract 16 This document discusses the usage and applicability of Link State 17 Vector Routing (LSVR) extensions in data center networks utilizing 18 CLOS or Fat-Tree topologies. The document is intended to provide a 19 simplified guide for the deployment of LSVR extensions. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on May 5, 2020. 38 Copyright Notice 40 Copyright (c) 2019 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 57 3. Recommended Reading . . . . . . . . . . . . . . . . . . . . . 3 58 4. Common Deployment Scenario . . . . . . . . . . . . . . . . . 3 59 5. Justification for BGP SPF Extension . . . . . . . . . . . . . 4 60 6. LSVR Applicability to CLOS Networks . . . . . . . . . . . . . 5 61 6.1. Usage of BGP-LS SPF SAFI . . . . . . . . . . . . . . . . 5 62 6.1.1. Relationship to Other BGP AFI/SAFI Tuples . . . . . . 6 63 6.2. Peering Models . . . . . . . . . . . . . . . . . . . . . 6 64 6.2.1. Sparse Peering Model . . . . . . . . . . . . . . . . 6 65 6.2.2. Bi-Connected Graph Heuristic . . . . . . . . . . . . 7 66 6.3. BGP Spine/Leaf Topology Policy . . . . . . . . . . . . . 7 67 6.4. BGP Peer Discovery Requirements . . . . . . . . . . . . . 8 68 6.5. BGP Peer Discovery . . . . . . . . . . . . . . . . . . . 9 69 6.5.1. BGP Peer Discovery Alternatives . . . . . . . . . . . 9 70 6.5.2. Data Center Interconnect (DCI) Applicability . . . . 9 71 7. Non-CLOS/FAT Tree Topology Applicability . . . . . . . . . . 10 72 8. Non-Transit Node Capability . . . . . . . . . . . . . . . . . 10 73 9. BGP Policy Applicability . . . . . . . . . . . . . . . . . . 10 74 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 75 11. Security Considerations . . . . . . . . . . . . . . . . . . . 11 76 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 77 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 13.1. Normative References . . . . . . . . . . . . . . . . . . 11 79 13.2. Informative References . . . . . . . . . . . . . . . . . 11 80 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 82 1. Introduction 84 This document complements [I-D.ietf-lsvr-bgp-spf] by discussing the 85 applicability of the technology in a simple and fairly common 86 deployment scenario, which is described in Section 4. 88 After describing the deployment scenario, Section 5 will describe the 89 reasons for BGP modifications for such deployments. 91 Once the control plane routing protocol requirements are described, 92 Section 6 will cover the LSVR protocol enhancements to BGP to meet 93 these requirements and their applicability to Data Center CLOS 94 networks. 96 2. Requirements Language 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 100 "OPTIONAL" in this document are to be interpreted as described in BCP 101 14 [RFC2119] [RFC8174] when, and only when, they appear in all 102 capitals, as shown here. 104 3. Recommended Reading 106 This document assumes knowledge of existing data center networks and 107 data center network topologies [CLOS]. This document also assumes 108 knowledge of data center routing protocols like BGP [RFC4271], BGP- 109 SPF [I-D.ietf-lsvr-bgp-spf], OSPF [RFC2328], as well as, data center 110 OAM protocols like LLDP [RFC4957] and BFD [RFC5580]. 112 4. Common Deployment Scenario 114 Within a Data Center, servers are commonly interconnected the CLOS 115 topology [CLOS]. The CLOS topology is fully non-blocking and the 116 topology is realized using Equal Cost Multi-Path (ECMP). In a CLOS 117 topology, the minimum number of parallel paths between two servers is 118 determined by the width of a tier-1 stage as shown in the figure 1. 120 The following example illustrates multi-stage CLOS topology. 122 Tier-1 123 +-----+ 124 |NODE | 125 +->| 12 |--+ 126 | +-----+ | 127 Tier-2 | | Tier-2 128 +-----+ | +-----+ | +-----+ 129 +------------>|NODE |--+->|NODE |--+--|NODE |-------------+ 130 | +-----| 9 |--+ | 10 | +--| 11 |-----+ | 131 | | +-----+ +-----+ +-----+ | | 132 | | | | 133 | | +-----+ +-----+ +-----+ | | 134 | +-----+---->|NODE |--+ |NODE | +--|NODE |-----+-----+ | 135 | | | +---| 6 |--+->| 7 |--+--| 8 |---+ | | | 136 | | | | +-----+ | +-----+ | +-----+ | | | | 137 | | | | | | | | | | 138 +-----+ +-----+ | +-----+ | +-----+ +-----+ 139 |NODE | |NODE | Tier-3 +->|NODE |--+ Tier-3 |NODE | |NODE | 140 | 1 | | 2 | | 3 | | 4 | | 5 | 141 +-----+ +-----+ +-----+ +-----+ +-----+ 142 | | | | | | | | 143 A O B O <- Servers -> Z O O O 145 Figure 1: Illustration of the basic CLOS 147 5. Justification for BGP SPF Extension 149 In order to simplify layer-3 routing and operations [RFC7938], many 150 data centers use BGP as a routing protocol to create both an underlay 151 and overlay network for their CLOS Topologies. However, BGP is a 152 path-vector routing protocol. Since it does not create a fabric 153 topology, it uses hop-by-hop EBGP peering to facilitate hop-by-hop 154 routing to create the underlay network and to resolve any overlay 155 next hops. The hop-by-hop BGP peering paradigm imposes several 156 restrictions within a CLOS. It severely prohibits a deployment of 157 Route Reflectors/Route Controllers as the EBGP sessions are congruent 158 with the data path. The BGP best-path algorithm is prefix-based and 159 it prevents announcements of prefixes to other BGP speakers until the 160 best-path decision process has been performed for the prefix at each 161 intermediate hop. These restrictions significantly delay the overall 162 convergence of the underlay network within a CLOS network. 164 The LSVR SPF modifications allow BGP to overcome these limitations. 165 Furthermore, using the BGP-LS NLRI format [RFC7752] allows the LSVR 166 data to be advertised for nodes, links, and prefixes in the BGP 167 routing domain and used for SPF computations. 169 6. LSVR Applicability to CLOS Networks 171 With the BGP SPF extensions [I-D.ietf-lsvr-bgp-spf], the BGP best- 172 path computation and route computation are replaced with OSPF-like 173 algorithms [RFC2328] both to determine whether an BGP-LS SPF NLRI has 174 changed and needs to be re-advertised and to compute the BGP routes. 175 These modifications will significantly improve convergence of the 176 underlay while affording the operational benefits of a single routing 177 protocol [RFC7938]. 179 Data center controllers typically require visibility to the BGP 180 topology to compute traffic-engineered paths. These controllers 181 learn the topology and other relevant information via the BGP-LS 182 address family [RFC7752] which is totally independent of the underlay 183 address families (usually IPv4/IPv6 unicast). Furthermore, in 184 traditional BGP underlays, all the BGP routers will need to advertise 185 their BGP-LS information independently. With the BGP SPF extensions, 186 controllers can learn the topology using the same BGP advertisements 187 used to compute the underlay routes. Furthermore, these data center 188 controllers can avail the convergence advantages of the BGP SPF 189 extensions. The placement of controllers can be outside of the 190 forwarding path or within the forwarding path. 192 Alternatively, as each and every router in the BGP SPF domain will 193 have a complete view of the topology, the operator can also choose to 194 configure BGP sessions in hop-by-hop peering model described in 195 [RFC7938] along with BFD [RFC5580]. In doing so, while the hop-by- 196 hop peering model lacks the inherent benefits of the controller-based 197 model, BGP updates need not be serialized by BGP best-path algorithm 198 in either of these models. This helps overall network convergence. 200 6.1. Usage of BGP-LS SPF SAFI 202 The BGP SPF extensions [I-D.ietf-lsvr-bgp-spf] define a new BGP-LS 203 SPF SAFI for announcement of BGP SPF link-state. The NLRI format and 204 its associated attributes follow the format of BGP-LS for node, link, 205 and prefix announcements. Whether the peering model within a CLOS 206 follows hop-by-hop peering described in [RFC7938] or any controller- 207 based or route-reflector peering, an operator can exchange BGP SPF 208 SAFI routes over the BGP peering by simply configuring BGP SPF SAFI 209 between the necessary BGP speakers. 211 The BGP-LS SPF SAFI can also co-exist with BGP IP Unicast SAFI which 212 could exchange overlapping IP routes. The routes received by these 213 SAFIs are evaluated, stored, and announced independently according to 214 the rules of [RFC4760]. The tie-breaking of route installation is a 215 matter of the local policies and preferences of the network operator. 217 Finally, as the BGP SPF peering is done following the procedures 218 described in [RFC4271], all the existing transport security 219 mechanisms including [RFC5925] are available for the BGP-LS SPF SAFI. 221 6.1.1. Relationship to Other BGP AFI/SAFI Tuples 223 Normally, the BGP-LS AFI/SAFI is used solely to compute the underlay 224 and is given preference over other AFI/SAFIs. Other BGP SAFIs, e.g., 225 IPv6/IPv6 Unicast VPN would use the BGP-SPF computed routes for next 226 hop resolution. However, if BGP-LS NLRI is also being advertised for 227 controller consumption, there is no need to replicate the Node, Link, 228 and Prefix NLRI in BGP-NLRI. Rather, additional NLRI attributes can 229 be advertised in the BGP-LS SPF AFI/SAFI as required. 231 6.2. Peering Models 233 As previously stated, BGP SPF can be deployed using the existing 234 peering model where there is a single-hop BGP session on each and 235 every link in the data center fabric [RFC7938]. This provides for 236 both the advertisement of routes and the determination of link and 237 neighboring switch availability. With BGP SPF, the underlay will 238 converge faster due to changes to the decision process that will 239 allow NLRI changes to be advertised faster after detecting a change. 241 6.2.1. Sparse Peering Model 243 Alternately, BFD [RFC5580] can be used to swiftly determine the 244 availability of links and the BGP peering model can be significantly 245 sparser than the data center fabric. BGP SPF sessions only need to 246 be established with enough peers to provide a bi-connected graph. If 247 IEBGP is used, then the BGP routers at tier N-1 will act as route- 248 reflectors for the routers at tier N. 250 The obvious usage of sparse peering is to avoid parallel sessions on 251 links between the same two BGP speakers in the data center fabric. 252 However, this use case is not very useful since parallel layer-3 253 links between the same two BGP routers are rare in CLOS or Fat-Tree 254 topologies. Two more interesting scenarios are described below. 256 In current data center topologies, there is often a very dense mesh 257 of links between levels, e.g., leaf and spine, providing 32-way, 258 64-way, or more Equal-Cost Multi-Path (ECMP) paths. In these 259 topologies, it is desirable not to have a BGP session on every link 260 and techniques such as the one described in Section 6.2.2 can be used 261 establish sessions on some subset of northbound links. 263 Alternately, controller-based data center topologies are envisioned 264 where BGP speakers within the data center only establish BGP sessions 265 with two or more controllers. In these topologies, fabric nodes 266 below the first tier (using [RFC7938] hierarchy) will establish BGP 267 multi-hop sessions with the controllers. For the multi-hop sessions, 268 determining the route to the controllers without depending on BGP 269 would need to be through some other means beyond the scope of this 270 document. However, the BGP discovery mechanisms described in 271 Section 6.5 would be one possibility. 273 6.2.2. Bi-Connected Graph Heuristic 275 With this heuristic, discovery of BGP peers is assumed, e.g., as 276 described in Section 6.5. Additionally, it assumed that the 277 direction of the peering can be ascertained. In the context of a 278 data center fabric, direction is either northbound (toward the 279 spine), southbound (toward the Top-Of-Rack (TOR) switches) or east- 280 west (same level in hierarchy. The determination of the direction is 281 beyond the scope of this document. However, it would be reasonable 282 to assume a technique where the TOR switches can be identified and 283 the number of hops to the TOR is used to determine the direction. 285 In this heuristic, BGP speakers allow passive session establishment 286 for southbound BGP sessions. For northbound sessions, BGP speakers 287 will attempt to maintain two northbound BGP sessions with different 288 switches (in data center fabrics there is normally a single layer-3 289 connection anyway). For east-west sessions, passive BGP session 290 establishment is allowed. However, BGP speaker will never actively 291 establish an east-west BGP session unless it can't establish two 292 northbound BGP sessions. 294 6.3. BGP Spine/Leaf Topology Policy 296 One of the advantages of using BGP SPF as the underlay protocol is 297 that BGP policy can be applied at any level. In Spine/Leaf 298 topologies, it is not necessary to advertise BGP-LS NLRI received by 299 leaves northbound to the spine nodes at the level above. If a common 300 AS is used for the spine nodes, this can easily be accomplished with 301 EBGP and a simple policy to filter advertisements from the leaves to 302 the spine if the first AS in the AS path is the spine AS. 304 In the figure below, the leaves would not advertise any NLRI with AS 305 64512 as the first AS in the AS path. 307 +--------+ +--------+ +--------+ 308 AS 64512 | | | | | | 309 for Spine | Spine 1+----+ Spine 2+- ......... -+ Spine N| 310 Nodes at | | | | | | 311 this Level +-+-+-+-++ ++-+-+-+-+ +-+-+-+-++ 312 +------+ | | | | | | | | | | | 313 | +-----|-|-|------+ | | | | | | | 314 | | +--|-|-|--------+-|-|-----------------+ | | | 315 | | | | | | +---+ | | | | | 316 | | | | | | | +--|-|-------------------+ | | 317 | | | | | | | | | | +------+ +----+ 318 | | | | | | | | | +--------------|----------+ | 319 | | | | | | | | +-------------+ | | | 320 | | | | | +----|--|----------------|--|--------+ | | 321 | | | | +------|--|--------------+ | | | | | 322 | | | +------+ | | | | | | | | 323 ++--+--++ +-+-+--++ ++-+--+-+ ++-+--+-+ 324 | Leaf 1|~~~~~~| Leaf 2| ........ | Leaf X| | Leaf Y| 325 +-------+ +-------+ +-------+ +-------+ 327 Figure 2: Spine/Leaf Topology Policy 329 6.4. BGP Peer Discovery Requirements 331 The most basic requirement is to be able to discover the address of a 332 single-hop peer without pre-configuration. This is being 333 accomplished today with using IPv6 Router Advertisements (RA) 334 [RFC4861] and assuming that a BGP sessions is desired with any 335 discovered peer. Beyond the basic requirement, it is useful to have 336 to following information relating to the BGP session: 338 o Autonomous System (AS) and BGP Identifier of a potential peer. 339 The latter can be used for debugging and to decrease the 340 likelihood of BGP session establishment collisions. 342 o Security capabilities supported and for cryptographic 343 authentication, the security capabilities and possibly a key-chain 344 [RFC8177] to be used. 346 o Session Policy Identifier - A group number or name used to 347 associate common session parameters with the peer. For example, 348 in a data center, BGP sessions with a Top of Rack (ToR) device 349 could have parameters than BGP sessions between leaf and spine. 351 In a data center fabric, it is often useful to know whether a peer is 352 southbound (towards the servers) or northbound (towards the spine or 353 super-spine), e.g., Section 6.2.2. A potential requirement would be 354 to determine this dynamically. One mechanism, without specifying all 355 the details, might be for the ToR switches to be identified when 356 installed and for the others switches in the fabric to determine 357 their level based on the distance from the closest ToR switch. 359 If there are multiple links between BGP speakers or the links between 360 BGP speakers are unnumbered, it is also useful to be able to 361 establish multi-hop sessions using the loopback addresses. This will 362 often require the discovery protocol to install route(s) toward the 363 potential peer loopback addresses prior to BGP session establishment. 365 Finally, a simple BGP discovery protocol could also be used to 366 establish a multi-hop session with one or more controllers by 367 advertising connectivity to one or more controllers. However, once 368 the multi-hop session actually traverses multiple nodes, it is 369 bordering a distance-vector routing protocol and possibly this is not 370 a good requirement for the discovery protocol. 372 6.5. BGP Peer Discovery 374 6.5.1. BGP Peer Discovery Alternatives 376 While BGP peer discovery is not part of [I-D.ietf-lsvr-bgp-spf], 377 there are, at least, three proposals for BGP peer discovery. At 378 least one of these mechanisms will be adopted and will be applicable 379 to deployments other than the data center. It is strongly 380 RECOMMENDED that the accepted mechanism be used in conjunction with 381 BGP SPF in data centers. The BGP discovery mechanism should 382 discovery both peer addresses and endpoints for BFD discovery. 383 Additionally, it would be great if there were a heuristic for 384 determining whether the peer is at a tier above or below the 385 discovering BGP speaker (refer to Section 6.2.2). 387 The BGP discovery mechanisms under consideration are 388 [I-D.acee-idr-lldp-peer-discovery], 389 [I-D.xu-idr-neighbor-autodiscovery], and [I-D.ietf-lsvr-l3dl]. 391 6.5.2. Data Center Interconnect (DCI) Applicability 393 Since BGP SPF is to be used for the routing underlay and DCI gateway 394 boxes typically have direct or very simple connectivity, BGP external 395 sessions would typically not include the BGP SPF SAFI. 397 7. Non-CLOS/FAT Tree Topology Applicability 399 The BGP SPF extensions [I-D.ietf-lsvr-bgp-spf] can be used in other 400 topologies and avail the inherent convergence improvements. 401 Additionally, sparse peering techniques may be utilized Section 6.2. 402 However, determining whether or to establish a BGP session is more 403 complex and the heuristic described in Section 6.2.2 cannot be used. 404 In such topologies, other techniques such as those described in 405 [I-D.ietf-lsr-dynamic-flooding] may be employed. One potential 406 deployment would be the underlay for a Service Provider (SP) backbone 407 where usage of a single protocol, i.e., BGP, is desired. 409 8. Non-Transit Node Capability 411 In certain scenarios, a BGP node wishes to participate in the BGP SPF 412 topology but never be used for transit traffic. These in include 413 situations where a server wants to make application services 414 available to clients homed at subnets throughout the BGP SPF domain 415 but doesn't ever want to be used as a router (i.e., carry transit 416 traffic). Another specific instance is where a controller is 417 resident on a server and direct connectivity to the controller is 418 required throughout the entire domain. This can readily be 419 accomplished using the BGP-LS Node NLRI Attribute SPF Status TLV as 420 described in [I-D.ietf-lsvr-bgp-spf]. 422 9. BGP Policy Applicability 424 Existing BGP policy including aggregation and prefix filtering may be 425 used in conjunction with the BGP-LS SPF SAFI. When aggregation 426 policy is used, BGP-LS SPF prefix NLRI will be originated for the 427 aggregate prefix and BGP-LS SPF prefix NLRI for components will be 428 filtered. Additionally, link and node NLRI may be filtered and the 429 abstracted by the prefix NLRI. 431 When BGP policy is used with the BGP-LS SPF SAFI, BGP speakers in the 432 BGP-LS SPF routing domain will not all have the same set of NLRI and 433 will compute a different BGP local routing table. Consequently, care 434 must be taken to assure routing is consistent and blackholes or 435 routing loops do not ensue. However, this is no different than if 436 tradition BGP routing using the IPv4 and IPv6 address families were 437 used. 439 10. IANA Considerations 441 No IANA updates are requested by this document. 443 11. Security Considerations 445 This document introduces no new security considerations above and 446 beyond those already specified in the [RFC4271] and 447 [I-D.ietf-lsvr-bgp-spf]. 449 12. Acknowledgements 451 The authors would like to thank Alvaro Retana and Yan Filyurin for 452 the review and comments. 454 13. References 456 13.1. Normative References 458 [I-D.ietf-lsvr-bgp-spf] 459 Patel, K., Lindem, A., Zandi, S., and W. Henderickx, 460 "Shortest Path Routing Extensions for BGP Protocol", 461 draft-ietf-lsvr-bgp-spf-06 (work in progress), September 462 2019. 464 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 465 Requirement Levels", BCP 14, RFC 2119, 466 DOI 10.17487/RFC2119, March 1997, 467 . 469 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 470 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 471 May 2017, . 473 13.2. Informative References 475 [CLOS] "A Study of Non-Blocking Switching Networks", The Bell 476 System Technical Journal, Vol. 32(2), DOI 477 10.1002/j.1538-7305.1953.tb01433.x, March 1953. 479 [I-D.acee-idr-lldp-peer-discovery] 480 Lindem, A., Patel, K., Zandi, S., Haas, J., and X. Xu, 481 "BGP Logical Link Discovery Protocol (LLDP) Peer 482 Discovery", draft-acee-idr-lldp-peer-discovery-05 (work in 483 progress), July 2019. 485 [I-D.ietf-lsr-dynamic-flooding] 486 Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda, 487 T., Cooper, D., Jalil, L., and S. Dontula, "Dynamic 488 Flooding on Dense Graphs", draft-ietf-lsr-dynamic- 489 flooding-03 (work in progress), June 2019. 491 [I-D.ietf-lsvr-l3dl] 492 Bush, R., Austein, R., and K. Patel, "Layer 3 Discovery 493 and Liveness", draft-ietf-lsvr-l3dl-02 (work in progress), 494 July 2019. 496 [I-D.xu-idr-neighbor-autodiscovery] 497 Xu, X., Talaulikar, K., Bi, K., Tantsura, J., and N. 498 Triantafillis, "BGP Neighbor Discovery", draft-xu-idr- 499 neighbor-autodiscovery-11 (work in progress), April 2019. 501 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 502 DOI 10.17487/RFC2328, April 1998, 503 . 505 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 506 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 507 DOI 10.17487/RFC4271, January 2006, 508 . 510 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 511 "Multiprotocol Extensions for BGP-4", RFC 4760, 512 DOI 10.17487/RFC4760, January 2007, 513 . 515 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 516 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 517 DOI 10.17487/RFC4861, September 2007, 518 . 520 [RFC4957] Krishnan, S., Ed., Montavont, N., Njedjou, E., Veerepalli, 521 S., and A. Yegin, Ed., "Link-Layer Event Notifications for 522 Detecting Network Attachments", RFC 4957, 523 DOI 10.17487/RFC4957, August 2007, 524 . 526 [RFC5580] Tschofenig, H., Ed., Adrangi, F., Jones, M., Lior, A., and 527 B. Aboba, "Carrying Location Objects in RADIUS and 528 Diameter", RFC 5580, DOI 10.17487/RFC5580, August 2009, 529 . 531 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 532 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 533 June 2010, . 535 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 536 S. Ray, "North-Bound Distribution of Link-State and 537 Traffic Engineering (TE) Information Using BGP", RFC 7752, 538 DOI 10.17487/RFC7752, March 2016, 539 . 541 [RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of 542 BGP for Routing in Large-Scale Data Centers", RFC 7938, 543 DOI 10.17487/RFC7938, August 2016, 544 . 546 [RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J. 547 Zhang, "YANG Data Model for Key Chains", RFC 8177, 548 DOI 10.17487/RFC8177, June 2017, 549 . 551 Authors' Addresses 553 Keyur Patel 554 Arrcus, Inc. 555 2077 Gateway Pl 556 San Jose, CA 95110 557 USA 559 Email: keyur@arrcus.com 561 Acee Lindem 562 Cisco Systems 563 301 Midenhall Way 564 Cary, NC 95110 565 USA 567 Email: acee@cisco.com 569 Shawn Zandi 570 Linkedin 571 222 2nd Street 572 San Francisco, CA 94105 573 USA 575 Email: szandi@linkedin.com 576 Gaurav Dawra 577 Linkedin 578 222 2nd Street 579 San Francisco, CA 94105 580 USA 582 Email: gdawra@linkedin.com