idnits 2.17.1 draft-filsfils-spring-segment-routing-ldp-interop-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The document has examples using IPv4 documentation addresses according to RFC6890, but does not use any IPv6 documentation addresses. Maybe there should be IPv6 examples, too? Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 18, 2014) is 3653 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '100' on line 277 -- Looks like a reference, but probably isn't: '300' on line 277 == Outdated reference: A later version (-07) exists of draft-ietf-mpls-seamless-mpls-06 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). 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 A. Bashandy 5 Expires: October 20, 2014 Cisco Systems, Inc. 6 B. Decraene 7 S. Litkowski 8 Orange 9 M. Horneffer 10 Deutsche Telekom 11 I. Milojevic 12 Telekom Srbija 13 R. Shakir 14 British Telecom 15 S. Ytti 16 TDC Oy 17 W. Henderickx 18 Alcatel-Lucent 19 J. Tantsura 20 Ericsson 21 E. Crabbe 22 Google, Inc. 23 April 18, 2014 25 Segment Routing interoperability with LDP 26 draft-filsfils-spring-segment-routing-ldp-interop-01 28 Abstract 30 A Segment Routing (SR) node steers a packet through a controlled set 31 of instructions, called segments, by prepending the packet with an SR 32 header. A segment can represent any instruction, topological or 33 service-based. SR allows to enforce a flow through any topological 34 path and service chain while maintaining per-flow state only at the 35 ingress node to the SR domain. 37 The Segment Routing architecture can be directly applied to the MPLS 38 data plane with no change in the forwarding plane. This drafts 39 describes how Segment Routing operates in a network where LDP is 40 deployed and in the case where SR-capable and non-SR-capable nodes 41 coexist. 43 Requirements Language 45 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 46 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 47 document are to be interpreted as described in RFC 2119 [RFC2119]. 49 Status of This Memo 51 This Internet-Draft is submitted in full conformance with the 52 provisions of BCP 78 and BCP 79. 54 Internet-Drafts are working documents of the Internet Engineering 55 Task Force (IETF). Note that other groups may also distribute 56 working documents as Internet-Drafts. The list of current Internet- 57 Drafts is at http://datatracker.ietf.org/drafts/current/. 59 Internet-Drafts are draft documents valid for a maximum of six months 60 and may be updated, replaced, or obsoleted by other documents at any 61 time. It is inappropriate to use Internet-Drafts as reference 62 material or to cite them other than as "work in progress." 64 This Internet-Draft will expire on October 20, 2014. 66 Copyright Notice 68 Copyright (c) 2014 IETF Trust and the persons identified as the 69 document authors. All rights reserved. 71 This document is subject to BCP 78 and the IETF Trust's Legal 72 Provisions Relating to IETF Documents 73 (http://trustee.ietf.org/license-info) in effect on the date of 74 publication of this document. Please review these documents 75 carefully, as they describe your rights and restrictions with respect 76 to this document. Code Components extracted from this document must 77 include Simplified BSD License text as described in Section 4.e of 78 the Trust Legal Provisions and are provided without warranty as 79 described in the Simplified BSD License. 81 Table of Contents 83 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 84 2. SR/LDP Ship-in-the-night coexistence . . . . . . . . . . . . 3 85 2.1. MPLS2MPLS co-existence . . . . . . . . . . . . . . . . . 5 86 2.2. IP2MPLS co-existence . . . . . . . . . . . . . . . . . . 6 87 3. Migration from LDP to SR . . . . . . . . . . . . . . . . . . 6 88 4. SR and LDP Interworking . . . . . . . . . . . . . . . . . . . 7 89 4.1. LDP to SR . . . . . . . . . . . . . . . . . . . . . . . . 7 90 4.2. SR to LDP . . . . . . . . . . . . . . . . . . . . . . . . 8 91 5. Leveraging SR benefits for LDP-based traffic . . . . . . . . 9 92 5.1. Eliminating Directed LDP Session . . . . . . . . . . . . 11 93 5.2. Guaranteed FRR coverage . . . . . . . . . . . . . . . . . 12 94 6. Inter-AS Option C, Carrier's Carrier and Seamless MPLS . . . 13 95 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 96 8. Manageability Considerations . . . . . . . . . . . . . . . . 13 97 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 98 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 99 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 100 11.1. Normative References . . . . . . . . . . . . . . . . . . 14 101 11.2. Informative References . . . . . . . . . . . . . . . . . 14 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 104 1. Introduction 106 Segment Routing, as described in 107 [I-D.filsfils-rtgwg-segment-routing], can be used on top of the MPLS 108 data plane without any modification as described in 109 [draft-filsfils-rtgwg-segment-routing-mpls-00]. 111 Segment Routing control plane can co-exist with current label 112 distribution protocols such as LDP. 114 This draft outlines the mechanisms through which SR provides 115 interoperability with LDP in cases where a mix of SR-capable and non- 116 SR-capable routers co-exist within the same network. 118 The first section describes the co-existence of SR with other MPLS 119 Control Plane. The second section documents a method to migrate from 120 LDP to SR-based MPLS tunneling. The third section documents the 121 interworking of LDP and SR in the case of non-homogenous deployment. 122 The fourth section describes how a partial SR deployment can be used 123 to provide SR benefits to LDP-based traffic. The fifth section 124 describes a possible application of SR in the context of inter-domain 125 MPLS use-cases. 127 2. SR/LDP Ship-in-the-night coexistence 129 We call "MPLS Control Plane Client (MCC)" any control plane protocol 130 installing forwarding entries in the MPLS data plane. SR, LDP, RSVP- 131 TE, BGP 3107, VPNv4, etc. are examples of MCCs. 133 An MCC, operating at node N, must ensure that the incoming label it 134 installs in the MPLS data plane of Node N has been uniquely allocated 135 to himself. 137 Thanks to the defined segment allocation rule and specifically the 138 notion of the SRGB, SR can co-exist with any other MCC. 140 This is clearly the case for the adjacency segment: it is a local 141 label allocated by the label manager, as for any MCC. 143 This is clearly the case for the prefix segment: the label manager 144 allocates the SRGB set of labels to the SR MCC client and the 145 operator ensures the unique allocation of each global prefix segment/ 146 label within the allocated SRGB set. 148 Note that this static label allocation capability of the label 149 manager has been existing for many years across several vendors and 150 hence is not new. Furthermore, note that the label-manager ability 151 to statically allocate a range of labels to a specific application is 152 not new either. This is required for MPLS-TP operation. In this 153 case, the range is reserved by the label manager and it is the MPLS- 154 TP NMS (acting as an MCC) that ensures the unique allocation of any 155 label within the allocated range and the creation of the related MPLS 156 forwarding entry. 158 Let us illustrate an example of ship-in-the-night (SIN) coexistence. 160 PE2 PE4 161 \ / 162 PE1----A----B---C---PE3 164 Figure 1: SIN coexistence 166 The EVEN VPN service is supported by PE2 and PE4 while the ODD VPN 167 service is supported by PE1 and PE3. The operator wants to tunnel 168 the ODD service via LDP and the EVEN service via SR. 170 This can be achieved in the following manner: 172 The operator configures PE1, PE2, PE3, PE4 with respective 173 loopbacks 192.0.2.201/32, 192.0.2.202/32, 192.0.2.203/32, 174 192.0.2.204/32. These PE's advertised their VPN routes with next- 175 hop set on their respective loopback address. 177 The operator configures A, B, C with respective loopbacks 178 192.0.2.1/32, 192.0.2.2/32, 192.0.2.3/32. 180 The operator configures PE2, A, B, C and PE4 with SRGB [100, 300]. 182 The operator attaches the respective Node-SIDs 202, 101, 102, 103 183 and 204 to the loopbacks of nodes PE2, A, B, C and PE4. The Node- 184 SID's are configured to request penultimate-hop-popping. 186 PE1, A, B, C and PE3 are LDP capable. 188 PE1 and PE3 are not SR capable. 190 PE3 sends an ODD VPN route to PE1 with next-hop 192.0.2.203 and VPN 191 label 10001. 193 From an LDP viewpoint: PE1 received an LDP label binding (1037) for 194 FEC 192.0.2.203/32 from its nhop A. A received an LDP label binding 195 (2048) for that FEC from its nhop B. B received an LDP label binding 196 (3059) for that FEC from its nhop C. C received implicit-null LDP 197 binding from its next-hop PE3. 199 As a result, PE1 sends its traffic to the ODD service route 200 advertised by PE3 to next-hop A with two labels: the top label is 201 1037 and the bottom label is 10001. A swaps 1037 with 2048 and 202 forwards to B. B swaps 2048 with 3059 and forwards to C. C pops 3059 203 and forwards to PE3. 205 PE4 sends an EVEN VPN route to PE2 with next-hop 192.0.2.204 and VPN 206 label 10002. 208 From an SR viewpoint: PE1 maps the IGP route 192.0.2.204/32 onto 209 Node-SID 204; A swaps 204 with 204 and forwards to B; B swaps 204 210 with 204 and forwards to C; C pops 204 and forwards to PE4. 212 As a result, PE2 sends its traffic to the VPN service route 213 advertised by PE4 to next-hop A with two labels: the top label is 204 214 and the bottom label is 10002. A swaps 204 with 204 and forwards to 215 B. B swaps 204 with 204 and forwards to C. C pops 204 and forwards to 216 PE4. 218 The two modes of MPLS tunneling co-exist. 220 The ODD service is tunneled from PE1 to PE3 through a continuous 221 LDP LSP traversing A, B and C. 223 The EVEN service is tunneled from PE2 to PE4 through a continuous 224 SR node segment traversing A, B and C. 226 2.1. MPLS2MPLS co-existence 228 We want to highlight that several MPLS2MPLS entries can be installed 229 in the data plane for the same prefix. 231 Let us examine A's MPLS forwarding table as an example: 233 Incoming label: 1037 235 - outgoing label: 2048 236 - outgoing nhop: B 237 - Note: this entry is programmed by LDP for 192.0.2.203/32 239 Incoming label: 203 240 - outgoing label: 203 241 - outgoing nhop: B 242 - Note: this entry is programmed by SR for 192.0.2.203/32 244 These two entries can co-exist because their incoming label is 245 unique. The uniqueness is guaranteed by the label manager allocation 246 rules. 248 The same applies for the MPLS2IP forwarding entries. 250 2.2. IP2MPLS co-existence 252 By default, we propose that if both LDP and SR propose an IP2MPLS 253 entry for the same IP prefix, then the LDP route is selected. 255 A local policy on a router MUST allow to prefer the SR-provided 256 IP2MPLS entry. 258 Note that this policy may be locally defined. There is no 259 requirement that all routers use the same policy. 261 3. Migration from LDP to SR 263 PE2 PE4 264 \ / 265 PE1----P5--P6--P7---PE3 267 Figure 2: Migration 269 Several migration techniques are possible. We describe one technique 270 inspired by the commonly used method to migrate from one IGP to 271 another. 273 T0: all the routers run LDP. Any service is tunneled from an ingress 274 PE to an egress PE over a continuous LDP LSP. 276 T1: all the routers are upgraded to SR. They are configured with the 277 SRGB range [100, 300]. PE1, PE2, PE3, PE4, P5, P6 and P7 are 278 respectively configured with the node segments 101, 102, 103, 104, 279 105, 106 and 107 (attached to their service-recursing loopback). 281 At this time, the service traffic is still tunneled over LDP LSP. 282 For example, PE1 has an SR node segment to PE3 and an LDP LSP to 283 PE3 but by default, as seen earlier, the LDP IP2MPLS encapsulation 284 is preferred. 286 T2: the operator enables the local policy at PE1 to prefer SR IP2MPLS 287 encapsulation over LDP IP2MPLS. 289 The service from PE1 to any other PE is now riding over SR. All 290 other service traffic is still transported over LDP LSP. 292 T3: gradually, the operator enables the preference for SR IP2MPLS 293 encapsulation across all the edge routers. 295 All the service traffic is now transported over SR. LDP is still 296 operational and services could be reverted to LDP. 298 However, any traffic switched through LDP entries will still 299 suffer from LDP-IGP synchronization. 301 T4: LDP is unconfigured from all routers. 303 4. SR and LDP Interworking 305 In this section, we analyze a use-case where SR is available in one 306 part of the network and LDP is available in another part. We 307 describe how a continuous MPLS tunnel can be built throughout the 308 network. 310 PE2 PE4 311 \ / 312 PE1----P5--P6--P7--P8---PE3 314 Figure 3: SR and LDP Interworking 316 Let us analyze the following example: 318 P6, P7, P8, PE4 and PE3 are LDP capable. 320 PE1, PE2, P5 and P6 are SR capable. PE1, PE2, P5 and P6 are 321 configured with SRGB (100, 200) and respectively with node 322 segments 101, 102, 105 and 106. 324 A service flow must be tunneled from PE1 to PE3 over a continuous 325 MPLS tunnel encapsulation. We need SR and LDP to interwork. 327 4.1. LDP to SR 329 In this section, we analyze a right-to-left traffic flow. 331 PE3 has learned a service route whose nhop is PE1. PE3 has an LDP 332 label binding from the nhop P8 for the FEC "PE1". Hence PE3 sends 333 its service packet to P8 as per classic LDP behavior. 335 P8 has an LDP label binding from its nhop P7 for the FEC "PE1" and 336 hence P8 forwards to P7 as per classic LDP behavior. 338 P7 has an LDP label binding from its nhop P6 for the FEC "PE1" and 339 hence P7 forwards to P6 as per classic LDP behavior. 341 P6 does not have an LDP binding from its nhop P5 for the FEC "PE1". 342 However P6 has an SR node segment to the IGP route "PE1". Hence, P6 343 forwards the packet to P5 and swaps its local LDP-label for FEC "PE1" 344 by the equivalent node segment (i.e. 101). 346 P5 pops 101 (assuming PE1 advertised its node segment 101 with the 347 penultimate-pop flag set) and forwards to PE1. 349 PE1 receives the tunneled packet and processes the service label. 351 The end-to-end MPLS tunnel is built from an LDP LSP from PE3 to P6 352 and the related node segment from P6 to PE1. 354 4.2. SR to LDP 356 In this section, we analyze the left-to-right traffic flow. 358 We assume that the operator configures P5 to act as a Segment Routing 359 Mapping Server (SRMS) and advertise the following mappings: (P7, 360 107), (P8, 108), (PE3, 103) and (PE4, 104). 362 These mappings are advertised as Remote-Bundle SID with Flag TBD. 364 The mappings advertised by an SR mapping server result from local 365 policy information configured by the operator. IF PE3 had been SR 366 capable, the operator would have configured PE3 with node segment 367 103. Instead, as PE3 is not SR capable, the operator configures that 368 policy at the SRMS and it is the latter which advertises the mapping. 369 Multiple SRMS servers can be provisioned in a network for redundancy. 371 The mapping server advertisements are only understood by the SR 372 capable routers. The SR capable routers install the related node 373 segments in the MPLS data plane exactly like if the node segments had 374 been advertised by the nodes themselves. 376 For example, PE1 installs the node segment 103 with nhop P5 exactly 377 as if PE3 had advertised node segment 103. 379 PE1 has a service route whose nhop is PE3. PE1 has a node segment 380 for that IGP route: 103 with nhop P5. Hence PE1 sends its service 381 packet to P5 with two labels: the bottom label is the service label 382 and the top label is 103. 384 P5 swaps 103 for 103 and forwards to P6. 386 P6's next-hop for the IGP route "PE3" is not SR capable (P7 does not 387 advertise the SR capability). However, P6 has an LDP label binding 388 from that next-hop for the same FEC (e.g. LDP label 1037). Hence, P6 389 swaps 103 for 1037 and forwards to P7. 391 P7 swaps this label with the LDP-label received from P8 and forwards 392 to P8. 394 P8 pops the LDP label and forwards to PE3. 396 PE3 receives the tunneled packet and processes the service label. 398 The end-to-end MPLS tunnel is built from an SR node segment from PE1 399 to P6 and an LDP LSP from P6 to PE3. 401 Note: SR mappings advertisements cannot set Penultimate Hop Popping. 402 In the previous example, P6 requires the presence of the segment 103 403 such as to map it to the LDP label 1037. For that reason, the P flag 404 available in the Prefix-SID is not available in the Remote-Bundle 405 SID. 407 5. Leveraging SR benefits for LDP-based traffic 409 SR can be deployed such as to enhance LDP transport. The SR 410 deployment can be limited to the network region where the SR benefits 411 are most desired. 413 In Figure 4, let us assume: 415 All link costs are 10 except FG which is 30. 417 All routers are LDP capable. 419 X, Y and Z are PE's participating to an important service S. 421 The operator requires 50msec link-based FRR for service S. 423 A, B, C, D, E, F and G are SR capable. 425 X, Y, Z are not SR capable, e.g. as part of a staged migration 426 from LDP to SR, the operator deploys SR first in a sub-part of the 427 network and then everywhere. 429 X 430 | 431 Y--A---B---E--Z 432 | | \ 433 D---C--F--G 434 30 436 Figure 4: Leveraging SR benefits for LDP-based-traffic 438 The operator would like to resolve the following issues: 440 To protect the link BA along the shortest-path of the important 441 flow XY, B requires an RLFA repair tunnel to D and hence a 442 directed LDP session from B to D. The operator does not like these 443 dynamically established multi-hop LDP sessions and would seek to 444 eliminate them. 446 There is no LFA/RLFA solution to protect the link BE along the 447 shortest path of the important flow XZ. The operator wants a 448 guaranteed link-based FRR solution. 450 The operator can meet these objectives by deploying SR only on A, B, 451 C, D, E and F: 453 The operator configures A, B, C, D, E, F and G with SRGB (100, 454 200) and respective node segments 101, 102, 103, 104, 105, 106 and 455 107. 457 The operator configures D as an SR Mapping Server with the 458 following policy mapping: (X, 201), (Y, 202), (Z, 203). 460 Each SR node automatically advertises local adjacency segment for 461 its IGP adjacencies. Specifically, F advertises adjacency segment 462 9001 for its adjacency FG. 464 A, B, C, D, E, F and G keep their LDP capability and hence the flows 465 XY and XZ are transported over end-to-end LDP LSP's. 467 For example, LDP at B installs the following MPLS data plane entries: 469 Incoming label: local LDB label bound by B for FEC Y 470 Outgoing label: LDP label bound by A for FEC Y 471 Outgoing nhop: A 473 Incoming label: local LDB label bound by B for FEC Z 474 Outgoing label: LDP label bound by E for FEC Z 475 Outgoing nhop: E 477 The novelty comes from how the backup chains are computed for these 478 LDP-based entries. While LDP labels are used for the primary nhop 479 and outgoing labels, SR information is used for the FRR construction. 480 In steady state, the traffic is transported over LDP LSP. In 481 transient FRR state, the traffic is backup thanks to the SR enhanced 482 capabilities. 484 This helps meet the requirements of the operator: 486 Eliminate directed LDP session. 488 Guaranteed FRR coverage. 490 Keep the traffic over LDP LSP in steady state. 492 Partial SR deployment only where needed. 494 5.1. Eliminating Directed LDP Session 496 B's MPLS entry to Y becomes: 498 - Incoming label: local LDB label bound by B for FEC Y 499 Outgoing label: LDP label bound by A for FEC Y 500 Backup outgoing label: SR node segment for Y {202} 501 Outgoing nhop: A 502 Backup nhop: repair tunnel: node segment to D {104} 503 with outgoing nhop: C 505 In steady-state, X sends its Y-destined traffic to B with a top label 506 which is the LDP label bound by B for FEC Y. B swaps that top label 507 for the LDP label bound by A for FEC Y and forwards to A. A pops the 508 LDP label and forwards to Y. 510 Upon failure of the link BA, B swaps the incoming top-label with the 511 node segment for Y (202) and sends the packet onto a repair tunnel to 512 D (node segment 104). Thus, B sends the packet to C with the label 513 stack {104, 202}. C pops the node segment 104 and forwards to D. D 514 swaps 202 for 202 and forwards to A. A's nhop to Y is not SR capable 515 and hence A swaps the incoming node segment 202 to the LDP label 516 announced by its next-hop (in this case, implicit null). 518 After IGP convergence, B's MPLS entry to Y will become: 520 - Incoming label: local LDB label bound by B for FEC Y 521 Outgoing label: LDP label bound by C for FEC Y 522 Outgoing nhop: C 524 And the traffic XY travels again over the LDP LSP. 526 Conclusion: the operator has eliminated its first problem: directed 527 LDP sessions are no longer required and the steady-state traffic is 528 still transported over LDP. The SR deployment is confined to the 529 area where these benefits are required. 531 5.2. Guaranteed FRR coverage 533 B's MPLS entry to Z becomes: 535 - Incoming label: local LDB label bound by B for FEC Z 536 Outgoing label: LDP label bound by E for FEC Z 537 Backup outgoing label: SR node segment for Z {203} 538 Outgoing nhop: E 539 Backup nhop: repair tunnel to G: {106, 9001} 541 G is reachable from B via the combination of a 542 node segment to F {106} and an adjacency segment 543 FG {9001} 545 Note that {106, 107} would have equally work. 546 Indeed, in many case, P's shortest path to Q is 547 over the link PQ. The adjacency segment from P to 548 Q is required only in very rare topologies where 549 the shortest-path from P to Q is not via the link 550 PQ. 552 In steady-state, X sends its Z-destined traffic to B with a top label 553 which is the LDP label bound by B for FEC Z. B swaps that top label 554 for the LDP label bound by E for FEC Z and forwards to E. E pops the 555 LDP label and forwards to Z. 557 Upon failure of the link BE, B swaps the incoming top-label with the 558 node segment for Z (203) and sends the packet onto a repair tunnel to 559 G (node segment 106 followed by adjacency segment 9001). Thus, B 560 sends the packet to C with the label stack {106, 9001, 203}. C pops 561 the node segment 106 and forwards to F. F pops the adjacency segment 562 9001 and forwards to G. G swaps 203 for 203 and forwards to E. E's 563 nhop to Z is not SR capable and hence E swaps the incoming node 564 segment 203 for the LDP label announced by its next-hop (in this 565 case, implicit null). 567 After IGP convergence, B's MPLS entry to Z will become: 569 - Incoming label: local LDB label bound by B for FEC Z 570 Outgoing label: LDP label bound by C for FEC Z 571 Outgoing nhop: C 573 And the traffic XZ travels again over the LDP LSP. 575 Conclusion: the operator has eliminated its second problem: 576 guaranteed FRR coverage is provided. The steady-state traffic is 577 still transported over LDP. The SR deployment is confined to the 578 area where these benefits are required. 580 6. Inter-AS Option C, Carrier's Carrier and Seamless MPLS 582 PE1---R1---B1---B2---R2---PE2 583 <-----------> <-----------> 584 AS1 AS2 586 Figure 5: Inter-AS Option C 588 In Inter-AS Option C [RFC4364], B2 advertises to B1 a BGP3107 route 589 for PE2 and B1 reflects it to its internal peers, such as PE1. PE1 590 learns from a service route reflector a service route whose nhop is 591 PE2. PE1 resolves that service route on the BGP3107 route to PE2. 592 That BGP3107 route to PE2 is itself resolved on the AS1 IGP route to 593 B1. 595 If AS1 operates SR, then the tunnel from PE1 to B1 is provided by the 596 node segment from PE1 to B1. 598 PE1 sends a service packet with three labels: the top one is the node 599 segment to B1, the next-one is the BGP3107 label provided by B1 for 600 the route "PE2" and the bottom one is the service label allocated by 601 PE2. 603 The same straightforward SR applicability is derived for CsC and 604 Seamless MPLS ([I-D.ietf-mpls-seamless-mpls]). 606 7. IANA Considerations 608 TBD 610 8. Manageability Considerations 612 TBD 614 9. Security Considerations 616 TBD 618 10. Acknowledgements 620 We would like to thank Pierre Francois and Ruediger Geib for their 621 contribution to the content of this document. 623 11. References 625 11.1. Normative References 627 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 628 Requirement Levels", BCP 14, RFC 2119, March 1997. 630 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 631 Networks (VPNs)", RFC 4364, February 2006. 633 11.2. Informative References 635 [I-D.filsfils-rtgwg-segment-routing] 636 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 637 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 638 Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, 639 "Segment Routing Architecture", draft-filsfils-rtgwg- 640 segment-routing-01 (work in progress), October 2013. 642 [I-D.ietf-mpls-seamless-mpls] 643 Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz, 644 M., and D. Steinberg, "Seamless MPLS Architecture", draft- 645 ietf-mpls-seamless-mpls-06 (work in progress), February 646 2014. 648 [draft-filsfils-rtgwg-segment-routing-mpls-00] 649 Filsfils, C. and S. Previdi, "Segment Routing with MPLS 650 data plane", October 2013. 652 Authors' Addresses 654 Clarence Filsfils (editor) 655 Cisco Systems, Inc. 656 Brussels 657 BE 659 Email: cfilsfil@cisco.com 661 Stefano Previdi (editor) 662 Cisco Systems, Inc. 663 Via Del Serafico, 200 664 Rome 00142 665 Italy 667 Email: sprevidi@cisco.com 668 Ahmed Bashandy 669 Cisco Systems, Inc. 670 170, West Tasman Drive 671 San Jose, CA 95134 672 US 674 Email: bashandy@cisco.com 676 Bruno Decraene 677 Orange 678 FR 680 Email: bruno.decraene@orange.com 682 Stephane Litkowski 683 Orange 684 FR 686 Email: stephane.litkowski@orange.com 688 Martin Horneffer 689 Deutsche Telekom 690 Hammer Str. 216-226 691 Muenster 48153 692 DE 694 Email: Martin.Horneffer@telekom.de 696 Igor Milojevic 697 Telekom Srbija 698 Takovska 2 699 Belgrade 700 RS 702 Email: igormilojevic@telekom.rs 704 Rob Shakir 705 British Telecom 706 London 707 UK 709 Email: rob.shakir@bt.com 710 Saku Ytti 711 TDC Oy 712 Mechelininkatu 1a 713 TDC 00094 714 FI 716 Email: saku@ytti.fi 718 Wim Henderickx 719 Alcatel-Lucent 720 Copernicuslaan 50 721 Antwerp 2018 722 BE 724 Email: wim.henderickx@alcatel-lucent.com 726 Jeff Tantsura 727 Ericsson 728 300 Holger Way 729 San Jose, CA 95134 730 US 732 Email: Jeff.Tantsura@ericsson.com 734 Edward Crabbe 735 Google, Inc. 736 1600 Amphitheatre Parkway 737 Mountain View, CA 94043 738 US 740 Email: edc@google.com