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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Filsfils, Ed. 3 Internet-Draft S. Previdi, Ed. 4 Intended status: Standards Track Cisco Systems, Inc. 5 Expires: January 5, 2017 B. Decraene 6 S. Litkowski 7 Orange 8 R. Shakir 9 Jive Communications 10 July 4, 2016 12 Segment Routing Architecture 13 draft-ietf-spring-segment-routing-09 15 Abstract 17 Segment Routing (SR) leverages the source routing paradigm. A node 18 steers a packet through an ordered list of instructions, called 19 segments. A segment can represent any instruction, topological or 20 service-based. A segment can have a local semantic to an SR node or 21 global within an SR domain. SR allows to enforce a flow through any 22 topological path and service chain while maintaining per-flow state 23 only at the ingress node to the SR domain. 25 Segment Routing can be directly applied to the MPLS architecture with 26 no change on the forwarding plane. A segment is encoded as an MPLS 27 label. An ordered list of segments is encoded as a stack of labels. 28 The segment to process is on the top of the stack. Upon completion 29 of a segment, the related label is popped from the stack. 31 Segment Routing can be applied to the IPv6 architecture, with a new 32 type of routing header. A segment is encoded as an IPv6 address. An 33 ordered list of segments is encoded as an ordered list of IPv6 34 addresses in the routing header. The active segment is indicated by 35 the Destination Address of the packet. The next active segment is 36 indicated by a pointer in the new routing header. 38 Requirements Language 40 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 41 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 42 document are to be interpreted as described in RFC 2119 [RFC2119]. 44 Status of This Memo 46 This Internet-Draft is submitted in full conformance with the 47 provisions of BCP 78 and BCP 79. 49 Internet-Drafts are working documents of the Internet Engineering 50 Task Force (IETF). Note that other groups may also distribute 51 working documents as Internet-Drafts. The list of current Internet- 52 Drafts is at http://datatracker.ietf.org/drafts/current/. 54 Internet-Drafts are draft documents valid for a maximum of six months 55 and may be updated, replaced, or obsoleted by other documents at any 56 time. It is inappropriate to use Internet-Drafts as reference 57 material or to cite them other than as "work in progress." 59 This Internet-Draft will expire on January 5, 2017. 61 Copyright Notice 63 Copyright (c) 2016 IETF Trust and the persons identified as the 64 document authors. All rights reserved. 66 This document is subject to BCP 78 and the IETF Trust's Legal 67 Provisions Relating to IETF Documents 68 (http://trustee.ietf.org/license-info) in effect on the date of 69 publication of this document. Please review these documents 70 carefully, as they describe your rights and restrictions with respect 71 to this document. Code Components extracted from this document must 72 include Simplified BSD License text as described in Section 4.e of 73 the Trust Legal Provisions and are provided without warranty as 74 described in the Simplified BSD License. 76 Table of Contents 78 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 79 1.1. Companion Documents . . . . . . . . . . . . . . . . . . . 4 80 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 81 3. Link-State IGP Segments . . . . . . . . . . . . . . . . . . . 7 82 3.1. IGP Segment, IGP SID . . . . . . . . . . . . . . . . . . 7 83 3.2. IGP-Prefix Segment, Prefix-SID . . . . . . . . . . . . . 7 84 3.2.1. Prefix-SID Algorithm . . . . . . . . . . . . . . . . 7 85 3.2.2. MPLS Dataplane . . . . . . . . . . . . . . . . . . . 8 86 3.2.3. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . 10 87 3.3. IGP-Node Segment, Node-SID . . . . . . . . . . . . . . . 10 88 3.4. IGP-Anycast Segment, Anycast SID . . . . . . . . . . . . 11 89 3.5. IGP-Adjacency Segment, Adj-SID . . . . . . . . . . . . . 14 90 3.5.1. Parallel Adjacencies . . . . . . . . . . . . . . . . 15 91 3.5.2. LAN Adjacency Segments . . . . . . . . . . . . . . . 16 92 3.6. Binding Segment . . . . . . . . . . . . . . . . . . . . . 16 93 3.6.1. Mapping Server . . . . . . . . . . . . . . . . . . . 16 94 3.6.2. Tunnel Headend . . . . . . . . . . . . . . . . . . . 17 95 3.7. Inter-Area Considerations . . . . . . . . . . . . . . . . 17 96 4. BGP Peering Segments . . . . . . . . . . . . . . . . . . . . 18 97 5. IGP Mirroring Context Segment . . . . . . . . . . . . . . . 19 98 6. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 19 99 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 100 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 101 8.1. MPLS Data Plane . . . . . . . . . . . . . . . . . . . . . 20 102 8.2. IPv6 Data Plane . . . . . . . . . . . . . . . . . . . . . 21 103 9. Manageability Considerations . . . . . . . . . . . . . . . . 22 104 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 105 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24 106 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 107 12.1. Normative References . . . . . . . . . . . . . . . . . . 25 108 12.2. Informative References . . . . . . . . . . . . . . . . . 25 109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 111 1. Introduction 113 With Segment Routing (SR), a node steers a packet through an ordered 114 list of instructions, called segments. A segment can represent any 115 instruction, topological or service-based. A segment can have a 116 local semantic to an SR node or global within an SR domain. SR 117 allows to enforce a flow through any path and service chain while 118 maintaining per-flow state only at the ingress node of the SR domain. 120 Segment Routing can be directly applied to the MPLS architecture 121 ([RFC3031]) with no change on the forwarding plane. A segment is 122 encoded as an MPLS label. An ordered list of segments is encoded as 123 a stack of labels. The active segment is on the top of the stack. A 124 completed segment is popped off the stack. The addition of a segment 125 is performed with a push. 127 In the Segment Routing MPLS instantiation, a segment could be of 128 several types: 130 o an IGP segment, 132 o a BGP Peering segments, 134 o an LDP LSP segment, 136 o an RSVP-TE LSP segment, 138 o a BGP LSP segment. 140 The first two (IGP and BGP Peering segments) types of segments are 141 defined in this document. The use of the last three types of 142 segments is illustrated in [I-D.ietf-spring-segment-routing-mpls]. 144 Segment Routing can be applied to the IPv6 architecture ([RFC2460]), 145 with a new type of routing header. A segment is encoded as an IPv6 146 address. An ordered list of segments is encoded as an ordered list 147 of IPv6 addresses in the routing header. The active segment is 148 indicated by the Destination Address of the packet. Upon completion 149 of a segment, a pointer in the new routing header is incremented and 150 indicates the next segment. 152 Numerous use-cases illustrate the benefits of source routing either 153 for FRR, OAM or Traffic Engineering reasons. 155 This document defines a set of instructions (called segments) that 156 are required to fulfill the described use-cases. These segments can 157 either be used in isolation (one single segment defines the source 158 route of the packet) or in combination (these segments are part of an 159 ordered list of segments that define the source route of the packet). 161 1.1. Companion Documents 163 This document defines the SR architecture, its routing model, the 164 IGP-based segments, the BGP-based segments and the service segments. 166 Use cases are described in [RFC7855], 167 [I-D.ietf-spring-segment-routing-central-epe], 168 [I-D.ietf-spring-segment-routing-msdc], 169 [I-D.filsfils-spring-large-scale-interconnect], 170 [I-D.ietf-spring-ipv6-use-cases], 171 [I-D.ietf-spring-resiliency-use-cases], [I-D.ietf-spring-oam-usecase] 172 and [I-D.ietf-spring-sr-oam-requirement]. 174 Segment Routing for MPLS dataplane is documented in 175 [I-D.ietf-spring-segment-routing-mpls]. 177 Segment Routing for IPv6 dataplane is documented in 178 [I-D.ietf-6man-segment-routing-header]. 180 IGP protocol extensions for Segment Routing are described in 181 [I-D.ietf-isis-segment-routing-extensions], 182 [I-D.ietf-ospf-segment-routing-extensions] and 183 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] referred in this 184 document as "IGP SR extensions documents". 186 The FRR solution for SR is documented in 187 [I-D.francois-rtgwg-segment-routing-ti-lfa]. 189 The PCEP protocol extensions for Segment Routing are defined in 190 [I-D.ietf-pce-segment-routing]. 192 The interaction between SR/MPLS with other MPLS Signaling planes is 193 documented in [I-D.ietf-spring-segment-routing-ldp-interop]. 195 2. Terminology 197 Segment: an instruction a node executes on the incoming packet (e.g.: 198 forward packet according to shortest path to destination, or, forward 199 packet through a specific interface, or, deliver the packet to a 200 given application/service instance). 202 SID: a Segment Identifier. Examples of SIDs are: a MPLS label, an 203 index value in a MPLS label space, an IPv6 address. Other types of 204 SIDs can be defined in the future. 206 Segment List: ordered list of SID's encoding the topological and 207 service source route of the packet. It is a stack of labels in the 208 MPLS architecture. It is an ordered list of IPv6 addresses in the 209 IPv6 architecture. 211 Segment Routing Domain (SR Domain): the set of nodes participating 212 into the source based routing model. These nodes may be connected to 213 the same physical infrastructure (e.g.: a Service Provider's network) 214 as well as nodes remotely connected to each other (e.g.: an 215 enterprise VPN or an overlay). Note that a SR domain may also be 216 confined within an IGP instance, in which case it is named SR-IGP 217 Domain. 219 Active segment: the segment that MUST be used by the receiving router 220 to process the packet. In the MPLS dataplane is the top label. In 221 the IPv6 dataplane is the destination address of a packet having the 222 Segment Routing Header as defined in 223 [I-D.ietf-6man-segment-routing-header]. 225 PUSH: the insertion of a segment at the head of the Segment list. 227 NEXT: the active segment is completed, the next segment becomes 228 active. 230 CONTINUE: the active segment is not completed and hence remains 231 active. The CONTINUE instruction is implemented as the SWAP 232 instruction in the MPLS dataplane. In IPv6, this is the plain IPv6 233 forwarding action of a regular IPv6 packet according to its 234 Destination Address. 236 SR Global Block (SRGB): local property of an SR node. In the MPLS 237 architecture, SRGB is the set of local labels reserved for global 238 segments. Using the same SRGB on all nodes within the SR domain ease 239 operations and troubleshooting and is expected to be a deployment 240 guideline. In the IPv6 architecture, the equivalent of the SRGB is 241 in fact the set of addresses used as global segments. Since there 242 are no restrictions on which IPv6 address can be used, the concept of 243 the SRGB includes all IPv6 global address space used within the SR 244 domain. 246 Global Segment: the related instruction is supported by all the SR- 247 capable nodes in the domain. In the MPLS architecture, a Global 248 Segment has a globally-unique index. The related local label at a 249 given node N is found by adding the globally-unique index to the SRGB 250 of node N. In the IPv6 architecture, a global segment is a globally- 251 unique IPv6 address. 253 Local Segment: the related instruction is supported only by the node 254 originating it. In the MPLS architecture, this is a local label 255 outside the SRGB. In the IPv6 architecture, this can be any IPv6 256 address whose reachability is not advertised in any routing protocol 257 (hence, the segment is known only by the local node). 259 IGP Segment: the generic name for a segment attached to a piece of 260 information advertised by a link-state IGP, e.g. an IGP prefix or an 261 IGP adjacency. 263 IGP-prefix Segment, Prefix-SID: an IGP-Prefix Segment is an IGP 264 segment attached to an IGP prefix. An IGP-Prefix Segment is global 265 (unless explicitly advertised otherwise) within the SR IGP instance/ 266 topology and identifies an instruction to forward the packet along 267 the path computed using the algorithm field, in the topology and the 268 IGP instance where it is advertised. The Prefix-SID is the SID of 269 the IGP-Prefix Segment. 271 IGP-Anycast: an IGP-Anycast Segment is an IGP-prefix segment which 272 does not identify a specific router, but a set of routers. The terms 273 "Anycast Segment" or "Anycast-SID" are often used as an abbreviation. 275 IGP-Adjacency: an IGP-Adjacency Segment is an IGP segment attached to 276 an unidirectional adjacency or a set of unidirectional adjacencies. 277 By default, an IGP-Adjacency Segment is local (unless explicitly 278 advertised otherwise) to the node that advertises it. 280 IGP-Node: an IGP-Node Segment is an IGP-Prefix Segment which 281 identifies a specific router (e.g. a loopback). The terms "Node 282 Segment" or Node-SID" are often used as an abbreviation. 284 SR Tunnel: a list of segments to be pushed on the packets directed on 285 the tunnel. The list of segments can be specified explicitly or 286 implicitly via a set of abstract constraints (latency, affinity, 287 SRLG, ...). In the latter case, a constraint-based path computation 288 is used to determine the list of segments associated with the tunnel. 289 The computation can be local or delegated to a PCE server. An SR 290 tunnel can be configured by the operator, provisioned via netconf or 291 provisioned via PCEP. An SR tunnel can be used for traffic- 292 engineering, OAM or FRR reasons. 294 Segment List Depth: the number of segments of an SR tunnel. The 295 entity instantiating an SR Tunnel at a node N should be able to 296 discover the depth insertion capability of the node N. The PCEP 297 discovery capability is described in [I-D.ietf-pce-segment-routing]. 299 3. Link-State IGP Segments 301 Within a link-state IGP domain, an SR-capable IGP node advertises 302 segments for its attached prefixes and adjacencies. These segments 303 are called IGP segments or IGP SIDs. They play a key role in Segment 304 Routing and use-cases as they enable the expression of any 305 topological path throughout the IGP domain. Such a topological path 306 is either expressed as a single IGP segment or a list of multiple IGP 307 segments. 309 3.1. IGP Segment, IGP SID 311 The terms "IGP Segment" and "IGP SID" are the generic names for a 312 segment attached to a piece of information advertised by a link-state 313 IGP, e.g. an IGP prefix or an IGP adjacency. 315 3.2. IGP-Prefix Segment, Prefix-SID 317 An IGP-Prefix Segment is an IGP segment attached to an IGP prefix. 318 An IGP-Prefix Segment is global (unless explicitly advertised 319 otherwise) within the SR/IGP domain. 321 The required IGP protocol extensions are defined in IGP SR extensions 322 documents. 324 3.2.1. Prefix-SID Algorithm 326 The IGP protocol extensions for Segment Routing define the Prefix-SID 327 advertisement which includes a set of flags and the algorithm field. 328 The algorithm field has the purpose of associating a given Prefix-SID 329 to a routing algorithm. 331 In the context of an instance and a topology, multiple Prefix-SID's 332 MAY be allocated to the same IGP Prefix as long as the algorithm 333 value is different in each one. 335 Multiple instances and topologies are defined in IS-IS and OSPF in: 336 [RFC5120], [RFC6822], [RFC6549] and [RFC4915]. 338 Initially, two "algorithms" have been defined: 340 o "Shortest Path": this algorithm is the default behavior. The 341 packet is forwarded along the well known ECMP-aware SPF algorithm 342 however it is explicitly allowed for a midpoint to implement 343 another forwarding based on local policy.. The "Shortest Path" 344 algorithm is in fact the default and current behavior of most of 345 the networks where local policies may override the SPF decision. 347 o "Strict Shortest Path": This algorithm mandates that the packet is 348 forwarded according to ECMP-aware SPF algorithm and instruct any 349 router in the path to ignore any possible local policy overriding 350 SPF decision. The SID advertised with "Strict Shortest Path" 351 algorithm ensures that the path the packet is going to take is the 352 expected, and not altered, SPF path. 354 An IGP-Prefix Segment identifies the path, to the related prefix, 355 along the path computed as per the algorithm field. 357 A packet injected anywhere within the SR/IGP domain with an active 358 Prefix-SID will be forwarded along path computed by the algorithm 359 expressed in the algorithm field. 361 The ingress node of an SR domain validates that the path to a prefix, 362 advertised with a given algorithm, includes nodes all supporting the 363 advertised algorithm. In other words, when computing paths for a 364 given algorithm, the transit nodes MUST compute the algorithm X on 365 the IGP topology, regardless of the support of the algorithm X by the 366 nodes in that topology. As a consequence, if a node on the path does 367 not support algorithm X, the IGP-Prefix segment will be interrupted 368 and will drop packet on that node. It's the responsibility of the 369 ingress node using a segment to check that all downstream nodes 370 support the algorithm of the segment. 372 Details of the two defined algorithms are defined in 373 [I-D.ietf-isis-segment-routing-extensions], 374 [I-D.ietf-ospf-segment-routing-extensions] and 375 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 377 3.2.2. MPLS Dataplane 379 When SR is used over the MPLS dataplane: 381 o the IGP signaling extension for IGP-Prefix segment includes the 382 P-Flag ([I-D.ietf-isis-segment-routing-extensions]) or the NP-Flag 383 ([I-D.ietf-ospf-segment-routing-extensions]). A Node N 384 advertising a Prefix-SID SID-R for its attached prefix R unset the 385 P-Flag (or NP-Flag) in order to instruct its connected neighbors 386 to perform the NEXT operation while processing SID-R. This 387 behavior is equivalent to Penultimate Hop Popping in MPLS. When 388 the flag is unset, the neighbors of N MUST perform the NEXT 389 operation while processing SID-R. When the flag is set, the 390 neighbors of N MUST perform the CONTINUE operation while 391 processing SID-R. 393 o A Prefix-SID is allocated in the form of an index in the SRGB (or 394 as a local MPLS label) according to a process similar to IP 395 address allocation. Typically the Prefix-SID is allocated by 396 policy by the operator (or NMS) and the SID very rarely changes. 398 o While SR allows to attach a local segment to an IGP prefix (using 399 the L-Flag), we specifically assume that when the terms "IGP- 400 Prefix Segment" and "Prefix-SID" are used, the segment is global 401 (the SID is allocated from the SRGB or as an index). This is 402 consistent with all the described use-cases that require global 403 segments attached to IGP prefixes. 405 o The allocation process MUST NOT allocate the same Prefix-SID to 406 different IP prefixes. 408 o If a node learns a Prefix-SID having a value that falls outside 409 the locally configured SRGB range, then the node MUST NOT use the 410 Prefix-SID and SHOULD issue an error log warning for 411 misconfiguration. 413 o If a node N advertises Prefix-SID SID-R for a prefix R that is 414 attached to N, N MUST either clear the P-Flag in the advertisement 415 of SID-R, or else maintain the following FIB entry: 417 Incoming Active Segment: SID-R 418 Ingress Operation: NEXT 419 Egress interface: NULL 421 o A remote node M MUST maintain the following FIB entry for any 422 learned Prefix-SID SID-R attached to IP prefix R: 424 Incoming Active Segment: SID-R 425 Ingress Operation: 426 If the next-hop of R is the originator of R 427 and instructed to remove the active segment: NEXT 428 Else: CONTINUE 429 Egress interface: the interface towards the next-hop along the 430 path computed using the algorithm advertised with 431 the SID toward prefix R. 433 3.2.3. IPv6 Dataplane 435 When SR is used over the IPv6 dataplane: 437 o The Prefix-SID is the prefix itself. No additional identifier is 438 needed for Segment Routing over IPv6. 440 o Any address belonging to any of the node's prefixes can be used as 441 Prefix-SIDs. 443 o An operator may want to explicitly indicate which of the node's 444 prefixes can be used as Prefix-SIDs through the setting of a flag 445 (e.g.: using the IGP prefix attribute defined in [RFC7794]) in the 446 routing protocol used for advertising the prefix. 448 o A global SID is instantiated through any globally advertised IPv6 449 address. 451 o A local SID is instantiated through a local IPv6 prefix not being 452 advertised and therefore known only by the local node. 454 A node N advertising an IPv6 address R usable as a segment identifier 455 MUST maintain the following FIB entry: 457 Incoming Active Segment: R 458 Ingress Operation: NEXT 459 Egress interface: NULL 461 Regardless Segment Routing, any remote IPv6 node will maintain a 462 plain IPv6 FIB entry for any prefix, no matter if they represent a 463 segment or not. 465 3.3. IGP-Node Segment, Node-SID 467 An IGP Node Segment is a an IGP Prefix Segment which identifies a 468 specific router (e.g. a loopback). The terms "Node Segment" or 469 "Node-SID" are often used as an abbreviation. The IGP SR extensions 470 define a flag that identifies Node-SIDs. 472 A "Node Segment" or "Node-SID" is fundamental to SR. From anywhere 473 in the network, it enforces the ECMP-aware shortest-path forwarding 474 of the packet towards the related node. 476 An IGP Node-SID MUST NOT be associated with a prefix that is owned by 477 more than one router within the same routing domain. 479 3.4. IGP-Anycast Segment, Anycast SID 481 An IGP-Anycast Segment is an IGP-prefix segment which does not 482 identify a specific router, but a set of routers. The terms "Anycast 483 Segment" or "Anycast-SID" are often used as an abbreviation. 485 An "Anycast Segment" or "Anycast SID" enforces the ECMP-aware 486 shortest-path forwarding towards the closest node of the anycast set. 487 This is useful to express macro-engineering policies or protection 488 mechanisms. 490 An IGP-Anycast Segment MUST NOT reference a particular node. 492 Within an anycast group, all routers MUST advertise the same prefix 493 with the same SID value. 495 +--------------+ 496 | Group A | 497 |192.0.2.10/32 | 498 | SID:100 | 499 | | 500 +-----------A1---A3----------+ 501 | | | \ / | | | 502 SID:10 | | | / | | | SID:30 503 203.0.113.1/32 | | | / \ | | | 203.0.113.3/32 504 PE1------R1----------A2---A4---------R3------PE3 505 \ /| | | |\ / 506 \ / | +--------------+ | \ / 507 \ / | | \ / 508 / | | / 509 / \ | | / \ 510 / \ | +--------------+ | / \ 511 / \| | | |/ \ 512 PE2------R2----------B1---B3----+----R4------PE4 513 203.0.113.2/32 | | | \ / | | | 203.0.113.4/32 514 SID:20 | | | / | | | SID:40 515 | | | / \ | | | 516 +-----+-----B2---B4----+-----+ 517 | | 518 | Group B | 519 | 192.0.2.1/32 | 520 | SID:200 | 521 +--------------+ 523 Transit device groups 525 The figure above describes a network example with two groups of 526 transit devices. Group A consists of devices {A1, A2, A3 and A4}. 527 They are all provisioned with the anycast address 192.0.2.10/32 and 528 the anycast SID 100. 530 Similarly, group B consists of devices {B1, B2, B3 and B4} and are 531 all provisioned with the anycast address 192.0.2.1/32, anycast SID 532 200. In the above network topology, each PE device is connected to 533 two routers in each of the groups A and B. 535 PE1 can choose a particular transit device group when sending traffic 536 to PE3 or PE4. This will be done by pushing the anycast SID of the 537 group in the stack. 539 Processing the anycast, and subsequent segments, requires special 540 care. 542 Obviously, the value of the SID following the anycast SID MUST be 543 understood by all nodes advertising the same anycast segment. 545 +-------------------------+ 546 | Group A | 547 | 192.0.2.10/32 | 548 | SID:100 | 549 |-------------------------| 550 | | 551 | SRGB: SRGB: | 552 SID:10 |(1000-2000) (3000-4000)| SID:30 553 PE1---+ +-------A1-------------A3-------+ +---PE3 554 \ / | | \ / | | \ / 555 \ / | | +-----+ / | | \ / 556 SRGB: \ / | | \ / | | \ / SRGB: 557 (7000-8000) R1 | | \ | | R3 (6000-7000) 558 / \ | | / \ | | / \ 559 / \ | | +-----+ \ | | / \ 560 / \ | | / \ | | / \ 561 PE2---+ +-------A2-------------A4-------+ +---PE4 562 SID:20 | SRGB: SRGB: | SID:40 563 |(2000-3000) (4000-5000)| 564 | | 565 +-------------------------+ 567 Transit paths via anycast group A 569 Considering a MPLS deployment, in the above topology, if device PE1 570 (or PE2) requires to send a packet to the device PE3 (or PE4) it 571 needs to encapsulate the packet in a MPLS payload with the following 572 stack of labels. 574 o Label allocated by R1 for anycast SID 100 (outer label). 576 o Label allocated by the nearest router in group A for SID 30 (for 577 destination PE3). 579 While the first label is easy to compute, in this case since there 580 are more than one topologically nearest devices (A1 and A2), unless 581 A1 and A2 allocated the same label value to the same prefix, 582 determining the second label is impossible. Devices A1 and A2 may be 583 devices from different hardware vendors. If both don't allocate the 584 same label value for SID 30, it is impossible to use the anycast 585 group "A" as a transit anycast group towards PE3. Hence, PE1 (or 586 PE2) cannot compute an appropriate label stack to steer the packet 587 exclusively through the group A devices. Same holds true for devices 588 PE3 and PE4 when trying to send a packet to PE1 or PE2. 590 To ease the use of anycast segment in a short term, it is recommended 591 to configure the same SRGB on all nodes of a particular anycast 592 group. Using this method, as mentioned above, computation of the 593 label following the anycast segment is straightforward. 595 Using anycast segment without configuring the same SRGB on nodes 596 belonging to the same device group may lead to misrouting (in a MPLS 597 VPN deployment, some traffic may leak between VPNs). 599 3.5. IGP-Adjacency Segment, Adj-SID 601 An IGP-Adjacency Segment is an IGP segment attached to a 602 unidirectional adjacency or a set of unidirectional adjacencies. By 603 default, an IGP-Adjacency Segment is local to the node which 604 advertises it. However, an Adjacency Segment can be global if 605 advertised by the IGP as such. The SID of the IGP-Adjacency Segment 606 is called the Adj-SID. 608 The adjacency is formed by the local node (i.e., the node advertising 609 the adjacency in the IGP) and the remote node (i.e., the other end of 610 the adjacency). The local node MUST be an IGP node. The remote node 611 MAY be an adjacent IGP neighbor or a non-adjacent neighbor (e.g.: a 612 Forwarding Adjacency, [RFC4206]). 614 A packet injected anywhere within the SR domain with a segment list 615 {SN, SNL}, where SN is the Node-SID of node N and SNL is an Adj-SID 616 attached by node N to its adjacency over link L, will be forwarded 617 along the shortest-path to N and then be switched by N, without any 618 IP shortest-path consideration, towards link L. If the Adj-SID 619 identifies a set of adjacencies, then the node N load- balances the 620 traffic among the various members of the set. 622 Similarly, when using a global Adj-SID, a packet injected anywhere 623 within the SR domain with a segment list {SNL}, where SNL is a global 624 Adj-SID attached by node N to its adjacency over link L, will be 625 forwarded along the shortest-path to N and then be switched by N, 626 without any IP shortest-path consideration, towards link L. If the 627 Adj-SID identifies a set of adjacencies, then the node N load- 628 balances the traffic among the various members of the set. The use 629 of global Adj-SID allows to reduce the size of the segment list when 630 expressing a path at the cost of additional state (i.e.: the global 631 Adj-SID will be inserted by all routers within the area in their 632 forwarding table). 634 An "IGP Adjacency Segment" or "Adj-SID" enforces the switching of the 635 packet from a node towards a defined interface or set of interfaces. 636 This is key to theoretically prove that any path can be expressed as 637 a list of segments. 639 The encodings of the Adj-SID include the B-flag. When set, the Adj- 640 SID refers to an adjacency that is eligible for protection (e.g.: 641 using IPFRR or MPLS-FRR). 643 The encodings of the Adj-SID include the L-flag. When set, the Adj- 644 SID has local significance. By default the L-flag is set. 646 A node SHOULD allocate one Adj-SIDs for each of its adjacencies. 648 A node MAY allocate multiple Adj-SIDs to the same adjacency. An 649 example is where the adjacency is established over a bundle 650 interface. Each bundle member MAY have its own Adj-SID. 652 A node MAY allocate the same Adj-SID to multiple adjacencies. 654 Adjacency suppression MUST NOT be performed by the IGP. 656 A node MUST install a FIB entry for any Adj-SID of value V attached 657 to data-link L: 659 Incoming Active Segment: V 660 Operation: NEXT 661 Egress Interface: L 663 The Adj-SID implies, from the router advertising it, the forwarding 664 of the packet through the adjacency identified by the Adj-SID, 665 regardless its IGP/SPF cost. In other words, the use of Adjacency 666 Segments overrides the routing decision made by SPF algorithm. 668 3.5.1. Parallel Adjacencies 670 Adj-SIDs can be used in order to represent a set of parallel 671 interfaces between two adjacent routers. 673 A node MUST install a FIB entry for any locally originated Adjacency 674 Segment (Adj-SID) of value W attached to a set of link B with: 676 Incoming Active Segment: W 677 Ingress Operation: NEXT 678 Egress interface: loadbalance between any data-link within set B 680 When parallel adjacencies are used and associated to the same Adj- 681 SID, and in order to optimize the load balancing function, a "weight" 682 factor can be associated to the Adj-SID advertised with each 683 adjacency. The weight tells the ingress (or a SDN/orchestration 684 system) about the loadbalancing factor over the parallel adjacencies. 685 As shown in Figure 1, A and B are connected through two parallel 686 adjacencies 687 link-1 688 +--------+ 689 | | 690 S---A B---C 691 | | 692 +--------+ 693 link-2 695 Figure 1: Parallel Links and Adj-SIDs 697 Node A advertises following Adj-SIDs and weights: 699 o Link-1: Adj-SID 1000, weight: 1 701 o Link-2: Adj-SID 1000, weight: 2 703 Node S receives the advertisements of the parallel adjacencies and 704 understands that by using Adj-SID 1000 node A will loadbalance the 705 traffic across the parallel links (link-1 and link-2) according to a 706 1:2 ratio. 708 The weight value is advertised with the Adj-SID as defined in IGP SR 709 extensions documents. 711 3.5.2. LAN Adjacency Segments 713 In LAN subnetworks, link-state protocols define the concept of 714 Designated Router (DR, in OSPF) or Designated Intermediate System 715 (DIS, in IS-IS) that conduct flooding in broadcast subnetworks and 716 that describe the LAN topology in a special routing update (OSPF 717 Type2 LSA or IS-IS Pseudonode LSP). 719 The difficulty with LANs is that each router only advertises its 720 connectivity to the DR/DIS and not to each other individual nodes in 721 the LAN. Therefore, additional protocol mechanisms (IS-IS and OSPF) 722 are necessary in order for each router in the LAN to advertise an 723 Adj-SID associated to each neighbor in the LAN. These extensions are 724 defined in IGP SR extensions documents. 726 3.6. Binding Segment 728 3.6.1. Mapping Server 730 A Remote-Binding SID S advertised by the mapping server M for remote 731 prefix R attached to non-SR-capable node N signals the same 732 information as if N had advertised S as a Prefix-SID. Further 733 details are described in the SR/LDP interworking procedures 734 ([I-D.ietf-spring-segment-routing-ldp-interop]. 736 The segment allocation and SRGB Maintenance rules are the same as 737 those defined for Prefix-SID. 739 3.6.2. Tunnel Headend 741 The segment allocation and SRGB Maintenance rules are the same as 742 those defined for Adj-SID. A tunnel attached to a head-end H acts as 743 an adjacency attached to H. 745 Note: an alternative consists of representing tunnels as forwarding- 746 adjacencies ( [RFC4206]). In such case, the tunnel is presented to 747 the routing area as a routing adjacency and is considered as such by 748 all area routers. The Remote-Binding SID is preferred as it allows 749 to advertise the presence of a tunnel without influencing the LSDB 750 and the SPF computation. 752 3.7. Inter-Area Considerations 754 In the following example diagram we assume an IGP deployed using 755 areas and where SR has been deployed. 757 ! ! 758 ! ! 759 B------C-----F----G-----K 760 / | | | 761 S---A/ | | | 762 \ | | | 763 \D------I----------J-----L----Z (192.0.2.1/32, Node-SID: 150) 764 ! ! 765 Area-1 ! Backbone ! Area 2 766 ! area ! 768 Figure 2: Inter-Area Topology Example 770 In area 2, node Z allocates Node-SID 150 to his local prefix 771 192.0.2.1/32. ABRs G and J will propagate the prefix into the 772 backbone area by creating a new instance of the prefix according to 773 normal inter-area/level IGP propagation rules. 775 Nodes C and I will apply the same behavior when leaking prefixes from 776 the backbone area down to area 1. Therefore, node S will see prefix 777 192.0.2.1/32 with Prefix-SID 150 and advertised by nodes C and I. 779 It therefore results that a Prefix-SID remains attached to its 780 related IGP Prefix through the inter-area process. 782 When node S sends traffic to 192.0.2.1/32, it pushes Node-SID(150) as 783 active segment and forward it to A. 785 When packet arrives at ABR I (or C), the ABR forwards the packet 786 according to the active segment (Node-SID(150)). Forwarding 787 continues across area borders, using the same Node-SID(150), until 788 the packet reaches its destination. 790 When an ABR propagates a prefix from one area to another it MUST set 791 the R-Flag. 793 4. BGP Peering Segments 795 In the context of BGP Egress Peer Engineering (EPE), as described in 796 [I-D.ietf-spring-segment-routing-central-epe], an EPE enabled Egress 797 PE node MAY advertise segments corresponding to its attached peers. 798 These segments are called BGP peering segments or BGP Peering SIDs. 799 They enable the expression of source-routed inter-domain paths. 801 An ingress border router of an AS may compose a list of segments to 802 steer a flow along a selected path within the AS, towards a selected 803 egress border router C of the AS and through a specific peer. At 804 minimum, a BGP Peering Engineering policy applied at an ingress PE 805 involves two segments: the Node SID of the chosen egress PE and then 806 the BGP Peering Segment for the chosen egress PE peer or peering 807 interface. 809 Hereafter, we will define three types of BGP peering segments/SID's: 810 PeerNodeSID, PeerAdjSID and PeerSetSID. 812 o PeerNode SID. A BGP PeerNode segment/SID is a local segment. At 813 the BGP node advertising it, its semantics is: 815 * SR header operation: NEXT. 817 * Next-Hop: the connected peering node to which the segment is 818 related. 820 o PeerAdj SID: A BGP PeerAdj segment/SID is a local segment. At the 821 BGP node advertising it, its semantics is: 823 * SR header operation: NEXT. 825 * Next-Hop: the peer connected through the interface to which the 826 segment is related. 828 o PeerSet SID. A BGP PeerSet segment/SID is a local segment. At 829 the BGP node advertising it, its semantics is: 831 * SR header operation: NEXT. 833 * Next-Hop: loadbalance across any connected interface to any 834 peer in the related group. 836 A peer set could be all the connected peers from the same AS or a 837 subset of these. A group could also span across AS. The group 838 definition is a policy set by the operator. 840 The BGP extensions necessary in order to signal these BGP peering 841 segments will be defined in a separate document. 843 5. IGP Mirroring Context Segment 845 It is beneficial for an IGP node to be able to advertise its ability 846 to process traffic originally destined to another IGP node, called 847 the Mirrored node and identified by an IP address or a Node-SID, 848 provided that a "Mirroring Context" segment be inserted in the 849 segment list prior to any service segment local to the mirrored node. 851 When a given node B wants to provide egress node A protection, it 852 advertises a segment identifying node's A context. Such segment is 853 called "Mirror Context Segment" and identified by the Mirror SID. 855 The Mirror SID is advertised using the Binding Segment defined in SR 856 IGP protocol extensions ( [I-D.ietf-isis-segment-routing-extensions], 857 [I-D.ietf-ospf-segment-routing-extensions] and 858 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). 860 In the event of a failure, a point of local repair (PLR) diverting 861 traffic from A to B does a PUSH of the Mirror SID on the protected 862 traffic. B, when receiving the traffic with the Mirror SID as the 863 active segment, uses that segment and process underlying segments in 864 the context of A. 866 6. Multicast 868 Segment Routing is defined for unicast. The application of the 869 source-route concept to Multicast is not in the scope of this 870 document. 872 7. IANA Considerations 874 This document does not require any action from IANA. 876 8. Security Considerations 878 Segment Routing is applicable to both MPLS and IPv6 data planes. 880 Segment Routing adds some meta-data on the packet, with the list of 881 forwarding path elements (e.g.: nodes, links, services, etc.) that 882 the packet must traverse. It has to be noted that the complete 883 source routed path may be represented by a single segment. This is 884 the case of the Binding SID. 886 8.1. MPLS Data Plane 888 When applied to the MPLS data plane, Segment Routing does not 889 introduce any new behavior or any change in the way MPLS data plane 890 works. Therefore, from a security standpoint, this document does not 891 define any additional mechanism in the MPLS data plane. 893 SR allows the expression of a source routed path using a single 894 segment (the Binding SID). Compared to RSVP-TE which also provides 895 explicit routing capability, there are no fundamental differences in 896 term of information provided. Both RSVP-TE and Segment Routing may 897 express a source routed path using a single segment. 899 When a path is expressed using a single label, the syntax of the 900 meta-data is equivalent between RSVP-TE and SR. 902 When a source routed path is expressed with a list of segments 903 additional meta-data is added to the packet consisting of the source 904 routed path the packet must follow expressed as a segment list. 906 When a path is expressed using a label stack, if one has access to 907 the meaning (i.e.: the Forwarding Equivalence Class) of the labels, 908 one has the knowledge of the explicit path. For the MPLS data plane, 909 as no data plane modification is required, there is no fundamental 910 change of capability. Yet, the occurrence of label stacking will 911 increase. 913 From a network protection standpoint, there is an assumed trust model 914 such that any node imposing a label stack on a packet is assumed to 915 be allowed to do so. This is a significant change compared to plain 916 IP offering shortest path routing but not fundamentally different 917 compared to existing techniques providing explicit routing capability 918 such as RSVP-TE. By default, the explicit routing information MUST 919 NOT be leaked through the boundaries of the administered domain. 920 Segment Routing extensions that have been defined in various 921 protocols, leverage the security mechanisms of these protocols such 922 as encryption, authentication, filtering, etc. 924 In the general case, a segment routing capable router accepts and 925 install labels, only if these labels have been previously advertised 926 by a trusted source. The received information is validated using 927 existing control plane protocols providing authentication and 928 security mechanisms. Segment routing does not define any additional 929 security mechanism in existing control plane protocols. 931 Segment Routing does not introduce signaling between the source and 932 the mid points of a source routed path. With SR, the source routed 933 path is computed using SIDs previously advertised in the IP control 934 plane. Therefore, in addition to filtering and controlled 935 advertisement of SIDs at the boundaries of the SR domain, filtering 936 in the data plane is also required. Filtering MUST be performed on 937 the forwarding plane at the boundaries of the SR domain and may 938 require looking at multiple labels/instruction. 940 For the MPLS data plane, there are no new requirement as the existing 941 MPLS architecture already allow such source routing by stacking 942 multiple labels. And for security protection, [RFC4381] section 2.4 943 and [RFC5920] section 8.2 already calls for the filtering of MPLS 944 packets on trust boundaries. 946 8.2. IPv6 Data Plane 948 When applied to the IPv6 data plane, Segment Routing does introduce 949 the Segment Routing Header (SRH, 950 [I-D.ietf-6man-segment-routing-header]) which is a type of Routing 951 Extension header as defined in [RFC2460]. 953 The SRH adds some meta-data on the IPv6 packet, with the list of 954 forwarding path elements (e.g.: nodes, links, services, etc.) that 955 the packet must traverse and that are represented by IPv6 addresses. 956 A complete source routed path may be encoded in the packet using a 957 single segment (single IPv6 address). 959 From a network protection standpoint, there is an assumed trust model 960 such that any node adding an SRH to the packet is assumed to be 961 allowed to do so. Therefore, by default, the explicit routing 962 information MUST NOT be leaked through the boundaries of the 963 administered domain. Segment Routing extensions that have been 964 defined in various protocols, leverage the security mechanisms of 965 these protocols such as encryption, authentication, filtering, etc. 967 In the general case, an SR IPv6 router accepts and install segments 968 identifiers (in the form of IPv6 addresses), only if these SIDs are 969 advertised by a trusted source. The received information is 970 validated using existing control plane protocols providing 971 authentication and security mechanisms. Segment routing does not 972 define any additional security mechanism in existing control plane 973 protocols. 975 In addition, SR domain boundary routers, by default, MUST apply data 976 plane filters so to only accept packets whose DA and SRH (if any) 977 contain addresses previously advertised as SIDs. 979 There are a number of security concerns with source routing at the 980 IPv6 data plane [RFC5095]. The new IPv6-based segment routing header 981 defined in [I-D.ietf-6man-segment-routing-header] and its associated 982 security measures address these concerns. The IPv6 Segment Routing 983 Header is defined in a way that blind attacks are never possible, 984 i.e., attackers will be unable to send source routed packets that get 985 successfully processed, without being part of the negations for 986 setting up the source routes or being able to eavesdrop legitimate 987 source routed packets. In some networks this base level security may 988 be complemented with other mechanisms, such as packet filtering, 989 cryptographic security, etc. 991 9. Manageability Considerations 993 In SR enabled networks, the path the packet takes is encoded in the 994 header. As the path is not signaled through a protocol, OAM 995 mechanisms are necessary in order for the network operator to 996 validate the effectiveness of a path as well as to check and monitor 997 its liveness and performance. However, it has to be noted that SR 998 allows to reduce substantially the number of states in transit nodes 999 and hence the number of elements that a transit node has to manage is 1000 smaller. 1002 SR OAM use cases and requirements for the MPLS data plane are defined 1003 in [I-D.ietf-spring-oam-usecase] and 1004 [I-D.ietf-spring-sr-oam-requirement]. OAM procedures for the MPLS 1005 data plane are defined in [I-D.ietf-mpls-spring-lsp-ping]. 1007 SR routers receive advertisement of SIDs (index, label or IPv6 1008 address) from the different routing protocols being extended for SR. 1009 Each of these protocols have monitoring and troubleshooting 1010 mechanisms so to provide operation and management functions for IP 1011 addresses that MUST be extended in order to include troubleshooting 1012 and monitoring functions of the SID. 1014 SR architecture introduces the usage of global segments. Each global 1015 segment must be bound to a globally-unique index or address. The 1016 management of the allocation of such index or address by the operator 1017 is critical for the network behavior to avoid situations like mis- 1018 routing. In addition to the allocation policy/tooling that the 1019 operator will have in place, an implementation SHOULD protect the 1020 network in case of conflict detection by providing a deterministic 1021 resolution approach. 1023 An operator may implement tools in order to audit the network and 1024 ensure the good allocation of indexes, SIDs or IP addresses. 1025 Conflict detection between SIDs, including Mapping Server binding 1026 SIDs, and their resolution are addressed in 1027 [I-D.ietf-spring-conflict-resolution]. 1029 SR with the MPLS data plane, can be gracefully introduced in an 1030 existing LDP [RFC5036] network. This is described in 1031 [I-D.ietf-spring-segment-routing-ldp-interop]. SR and LDP may also 1032 inter-work. In this case, the introduction of mapping-server may 1033 introduce some additional manageability considerations that are 1034 discussed in [I-D.ietf-spring-segment-routing-ldp-interop]. 1036 When a path is expressed using a a label stack, the occurrence of 1037 label stacking will increase. A node may want to signal in the 1038 control plane it's ability in terms of size of the label stack it can 1039 support. 1041 A YANG data model [RFC6020] for segment routing configuration and 1042 operations has been defined in [I-D.ietf-spring-sr-yang]. 1044 When Segment Routing is applied to the IPv6 data plane, segments are 1045 identified through IPv6 addresses. The allocation, management and 1046 troubleshooting of segment identifiers is no different than the 1047 existing mechanisms applied to the allocation and management of IPv6 1048 addresses. 1050 In the SR over IPv6 data plane context, the allocation of SIDs 1051 results into the allocation of IPv6 addresses. Therefore, 1052 management, troubleshooting, monitoring functions are the same as the 1053 one used for IPv6 addresses. 1055 The control of a source routed path of an IPv6 packet having an SRH 1056 SHOULD be implemented through the inspection of the packet header and 1057 more precisely its DA and segment list (in the SRH). The DA of the 1058 packet gives the active segment address. The segment list in the SRH 1059 gives the entire path of the packet. The validation of the source 1060 routed path is done through inspection of DA and SRH present in the 1061 packet header matched to the equivalent routing table entries. 1063 In the context of SR over the IPv6 data plane, the source routed path 1064 is encoded in the SRH as described in 1065 [I-D.ietf-6man-segment-routing-header]. The SR IPv6 source routed 1066 path is instantiated into the SRH as a list of IPv6 address where the 1067 active segment is in the Destination Address (DA) field of the IPv6 1068 packet header. Typically, by inspecting in any node the packet 1069 header, it is possible to derive the source routed path it belongs 1070 to. Similar to the context of SR over MPLS data plane, an 1071 implementation may originate path control and monitoring packets 1072 where the source routed path is inserted in the SRH and where each 1073 segment of the path inserts in the packet the relevant data in order 1074 to measure the end to end path and performance. 1076 10. Contributors 1078 The following people have substantially contributed to the definition 1079 of the Segment Routing architecture and to the editing of this 1080 document: 1082 Ahmed Bashandy 1083 Cisco Systems, Inc. 1084 Email: bashandy@cisco.com 1086 Martin Horneffer 1087 Deutsche Telekom 1088 Email: Martin.Horneffer@telekom.de 1090 Wim Henderickx 1091 Alcatel-Lucent 1092 Email: wim.henderickx@alcatel-lucent.com 1094 Jeff Tantsura 1095 Ericsson 1096 Email: Jeff.Tantsura@ericsson.com 1098 Edward Crabbe 1099 Individual 1100 Email: edward.crabbe@gmail.com 1102 Igor Milojevic 1103 Email: milojevicigor@gmail.com 1105 Saku Ytti 1106 TDC 1107 Email: saku@ytti.fi 1109 11. Acknowledgements 1111 We would like to thank Dave Ward, Dan Frost, Stewart Bryant, Pierre 1112 Francois, Thomas Telkamp, Les Ginsberg, Ruediger Geib, Hannes 1113 Gredler, Pushpasis Sarkar, Eric Rosen and Chris Bowers for their 1114 comments and review of this document. 1116 12. References 1118 12.1. Normative References 1120 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1121 Requirement Levels", BCP 14, RFC 2119, 1122 DOI 10.17487/RFC2119, March 1997, 1123 . 1125 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1126 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 1127 December 1998, . 1129 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 1130 Label Switching Architecture", RFC 3031, 1131 DOI 10.17487/RFC3031, January 2001, 1132 . 1134 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 1135 Hierarchy with Generalized Multi-Protocol Label Switching 1136 (GMPLS) Traffic Engineering (TE)", RFC 4206, 1137 DOI 10.17487/RFC4206, October 2005, 1138 . 1140 12.2. Informative References 1142 [I-D.filsfils-spring-large-scale-interconnect] 1143 Filsfils, C., Cai, D., Previdi, S., Henderickx, W., 1144 Shakir, R., Cooper, D., Ferguson, F., Lin, S., Laberge, 1145 T., Decraene, B., Jalil, L., and J. Tantsura, 1146 "Interconnecting Millions Of Endpoints With Segment 1147 Routing", draft-filsfils-spring-large-scale- 1148 interconnect-02 (work in progress), April 2016. 1150 [I-D.francois-rtgwg-segment-routing-ti-lfa] 1151 Francois, P., Filsfils, C., Bashandy, A., and B. Decraene, 1152 "Topology Independent Fast Reroute using Segment Routing", 1153 draft-francois-rtgwg-segment-routing-ti-lfa-01 (work in 1154 progress), May 2016. 1156 [I-D.ietf-6man-segment-routing-header] 1157 Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, 1158 J., Aries, E., Kosugi, T., Vyncke, E., and D. Lebrun, 1159 "IPv6 Segment Routing Header (SRH)", draft-ietf-6man- 1160 segment-routing-header-01 (work in progress), March 2016. 1162 [I-D.ietf-isis-segment-routing-extensions] 1163 Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., 1164 Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS 1165 Extensions for Segment Routing", draft-ietf-isis-segment- 1166 routing-extensions-07 (work in progress), June 2016. 1168 [I-D.ietf-mpls-spring-lsp-ping] 1169 Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini, 1170 S., Gredler, H., and M. Chen, "Label Switched Path (LSP) 1171 Ping/Trace for Segment Routing Networks Using MPLS 1172 Dataplane", draft-ietf-mpls-spring-lsp-ping-00 (work in 1173 progress), May 2016. 1175 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] 1176 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 1177 Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3 1178 Extensions for Segment Routing", draft-ietf-ospf-ospfv3- 1179 segment-routing-extensions-05 (work in progress), March 1180 2016. 1182 [I-D.ietf-ospf-segment-routing-extensions] 1183 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 1184 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1185 Extensions for Segment Routing", draft-ietf-ospf-segment- 1186 routing-extensions-08 (work in progress), April 2016. 1188 [I-D.ietf-pce-segment-routing] 1189 Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., 1190 Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick, 1191 "PCEP Extensions for Segment Routing", draft-ietf-pce- 1192 segment-routing-07 (work in progress), March 2016. 1194 [I-D.ietf-spring-conflict-resolution] 1195 Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka, 1196 "Segment Routing Conflict Resolution", draft-ietf-spring- 1197 conflict-resolution-01 (work in progress), June 2016. 1199 [I-D.ietf-spring-ipv6-use-cases] 1200 Brzozowski, J., Leddy, J., Leung, I., Previdi, S., 1201 Townsley, W., Martin, C., Filsfils, C., and R. Maglione, 1202 "IPv6 SPRING Use Cases", draft-ietf-spring-ipv6-use- 1203 cases-06 (work in progress), March 2016. 1205 [I-D.ietf-spring-oam-usecase] 1206 Geib, R., Filsfils, C., Pignataro, C., and N. Kumar, "A 1207 Scalable and Topology-Aware MPLS Dataplane Monitoring 1208 System", draft-ietf-spring-oam-usecase-03 (work in 1209 progress), April 2016. 1211 [I-D.ietf-spring-resiliency-use-cases] 1212 Francois, P., Filsfils, C., Decraene, B., and R. Shakir, 1213 "Use-cases for Resiliency in SPRING", draft-ietf-spring- 1214 resiliency-use-cases-03 (work in progress), April 2016. 1216 [I-D.ietf-spring-segment-routing-central-epe] 1217 Filsfils, C., Previdi, S., Aries, E., Ginsburg, D., and D. 1218 Afanasiev, "Segment Routing Centralized BGP Peer 1219 Engineering", draft-ietf-spring-segment-routing-central- 1220 epe-01 (work in progress), March 2016. 1222 [I-D.ietf-spring-segment-routing-ldp-interop] 1223 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and 1224 S. Litkowski, "Segment Routing interworking with LDP", 1225 draft-ietf-spring-segment-routing-ldp-interop-04 (work in 1226 progress), July 2016. 1228 [I-D.ietf-spring-segment-routing-mpls] 1229 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 1230 Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J., 1231 and E. Crabbe, "Segment Routing with MPLS data plane", 1232 draft-ietf-spring-segment-routing-mpls-04 (work in 1233 progress), March 2016. 1235 [I-D.ietf-spring-segment-routing-msdc] 1236 Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. 1237 Lapukhov, "BGP-Prefix Segment in large-scale data 1238 centers", draft-ietf-spring-segment-routing-msdc-01 (work 1239 in progress), April 2016. 1241 [I-D.ietf-spring-sr-oam-requirement] 1242 Kumar, N., Pignataro, C., Akiya, N., Geib, R., Mirsky, G., 1243 and S. Litkowski, "OAM Requirements for Segment Routing 1244 Network", draft-ietf-spring-sr-oam-requirement-02 (work in 1245 progress), July 2016. 1247 [I-D.ietf-spring-sr-yang] 1248 Litkowski, S., Qu, Y., and J. Tantsura, "YANG Data Model 1249 for Segment Routing", draft-ietf-spring-sr-yang-02 (work 1250 in progress), March 2016. 1252 [RFC4381] Behringer, M., "Analysis of the Security of BGP/MPLS IP 1253 Virtual Private Networks (VPNs)", RFC 4381, 1254 DOI 10.17487/RFC4381, February 2006, 1255 . 1257 [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. 1258 Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", 1259 RFC 4915, DOI 10.17487/RFC4915, June 2007, 1260 . 1262 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 1263 "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, 1264 October 2007, . 1266 [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation 1267 of Type 0 Routing Headers in IPv6", RFC 5095, 1268 DOI 10.17487/RFC5095, December 2007, 1269 . 1271 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1272 Topology (MT) Routing in Intermediate System to 1273 Intermediate Systems (IS-ISs)", RFC 5120, 1274 DOI 10.17487/RFC5120, February 2008, 1275 . 1277 [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS 1278 Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, 1279 . 1281 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 1282 the Network Configuration Protocol (NETCONF)", RFC 6020, 1283 DOI 10.17487/RFC6020, October 2010, 1284 . 1286 [RFC6549] Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi- 1287 Instance Extensions", RFC 6549, DOI 10.17487/RFC6549, 1288 March 2012, . 1290 [RFC6822] Previdi, S., Ed., Ginsberg, L., Shand, M., Roy, A., and D. 1291 Ward, "IS-IS Multi-Instance", RFC 6822, 1292 DOI 10.17487/RFC6822, December 2012, 1293 . 1295 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1296 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1297 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1298 March 2016, . 1300 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1301 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1302 Packet Routing in Networking (SPRING) Problem Statement 1303 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1304 2016, . 1306 Authors' Addresses 1308 Clarence Filsfils (editor) 1309 Cisco Systems, Inc. 1310 Brussels 1311 BE 1313 Email: cfilsfil@cisco.com 1315 Stefano Previdi (editor) 1316 Cisco Systems, Inc. 1317 Via Del Serafico, 200 1318 Rome 00142 1319 Italy 1321 Email: sprevidi@cisco.com 1323 Bruno Decraene 1324 Orange 1325 FR 1327 Email: bruno.decraene@orange.com 1329 Stephane Litkowski 1330 Orange 1331 FR 1333 Email: stephane.litkowski@orange.com 1335 Rob Shakir 1336 Jive Communications, Inc. 1337 1275 West 1600 North, Suite 100 1338 Orem, UT 84057 1340 Email: rjs@rob.sh