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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PWE3 Working Group Luca Martini (Ed.) 3 Internet Draft Cisco Systems Inc. 4 Expires: December 2007 Matthew Bocci (Ed.) 5 Alcatel-Lucent 6 Florin Balus (Ed.) 7 Alcatel-Lucent 9 June 2007 11 Dynamic Placement of Multi Segment Pseudo Wires 13 draft-ietf-pwe3-dynamic-ms-pw-03.txt 15 Status of this Memo 17 By submitting this Internet-Draft, each author represents that any 18 applicable patent or other IPR claims of which he or she is aware 19 have been or will be disclosed, and any of which he or she becomes 20 aware will be disclosed, in accordance with Section 6 of BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that other 24 groups may also distribute working documents as Internet-Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/1id-abstracts.html 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 Abstract 39 There is a requirement for service providers to be able to extend the 40 reach of pseudo wires (PW) across multiple Packet Switched Network 41 domains. A Multi-Segment PW is defined as a set of two or more 42 contiguous PW segments that behave and function as a single point- 43 to-point PW. This document describes extensions to the PW control 44 protocol to dynamically place the segments of the multi segment 45 pseudo wire among a set of Provider Edge (PE) routers. 47 Table of Contents 49 1 Specification of Requirements ........................ 3 50 2 Major Co-authors ..................................... 3 51 3 Acknowledgements ..................................... 3 52 4 Introduction ......................................... 3 53 4.1 Scope ................................................ 3 54 4.2 Terminology .......................................... 4 55 4.3 Architecture Overview ................................ 4 56 5 Applicability ........................................ 6 57 5.1 Requirements Addressed ............................... 6 58 5.2 Changes to Existing PW Signaling ..................... 6 59 6 PW layer 2 addressing ................................ 6 60 6.1 Attachment Circuit Addressing ........................ 7 61 6.2 S-PE addressing ...................................... 7 62 7 Dynamic placement of MS-PWs .......................... 8 63 7.1 Pseudo wire routing procedures ....................... 8 64 7.1.1 AII PW routing table Lookup aggregation rules ........ 9 65 7.1.2 PW Static Route ...................................... 9 66 7.1.3 Dynamic advertisement with BGP ....................... 9 67 7.2 LDP Signaling ........................................ 10 68 7.2.1 MS-PW Bandwidth Signaling ............................ 11 69 7.2.2 Active/Passive T-PE Election Procedure ............... 12 70 7.2.3 Detailed Signaling Procedures ........................ 13 71 7.2.4 Support for Explicit PW Path ......................... 14 72 8 Failure Handling Procedures .......................... 14 73 8.1 PSN Failures ......................................... 14 74 8.2 S-PE Failures ........................................ 14 75 9 Operations and Maintenance (OAM) ..................... 14 76 10 Security Considerations .............................. 15 77 11 IANA Considerations .................................. 15 78 11.1 LDP Status Codes ..................................... 15 79 11.2 BGP SAFI ............................................. 15 80 12 Full Copyright Statement ............................. 15 81 13 Intellectual Property Statement ...................... 16 82 14 Normative References ................................. 16 83 15 Informative References ............................... 17 84 16 Author Information ................................... 17 86 1. Specification of Requirements 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 90 document are to be interpreted as described in RFC 2119. 92 2. Major Co-authors 94 The editors gratefully acknowledge the following additional co- 95 authors: Mustapha Aissaoui, Nabil Bitar, Mike Loomis, David McDysan, 96 Chris Metz, Andy Malis, Jason Rusmeisel, Himanshu Shah, Jeff 97 Sugimoto. 99 3. Acknowledgements 101 The editors also gratefully acknowledge the input of the following 102 people: Mike Ducket, Paul Doolan, Prayson Pate, Ping Pan, Vasile 103 Radoaca, Yeongil Seo, Yetik Serbest, Yuichiro Wada. 105 4. Introduction 107 4.1. Scope 109 [MS-REQ] describes the service provider requirements for extending 110 the reach of pseudo-wires across multiple PSN domains. This is 111 achieved using a Multi-segment Pseudo-Wire (MS-PW). A MS-PW is 112 defined as a set of two or more contiguous PW segments that behave 113 and function as a single point-to-point PW. This architecture is 114 described in [MS-ARCH]. 116 The procedures for establishing PWs that extend across a single PWE3 117 domain are described in [RFC4447], while procedures for setting up 118 PWs across multiple domains, or control planes are described in [PW- 119 SEG]. 121 The purpose of this draft is to specify extensions to the PWE3 122 control protocol [RFC4447], and [PW-SEG] procedures, to enable 123 multi-segment PWs to be automatically placed. The proposed procedures 124 follow the guidelines defined in [RFC3036bis] and enable the reuse of 125 existing TLVs, and procedures defined for SS-PWs in [RFC4447]. 127 4.2. Terminology 129 [MS-ARCH] provides terminology for multi-segment pseudo wires. 131 This document defines the following additional terms: 133 - Source Terminating PE (ST-PE). A Terminating PE (T-PE), which 134 assumes the active signaling role and initiates the signaling for 135 multi-segment PW. 136 - Target Terminating PE (TT-PE). A Terminating PE (T-PE) that 137 assumes the passive signaling role. It waits and responds to the 138 multi-segment PW signaling message in the reverse direction. 139 - Forward Direction: ST-PE to TT-PE. 140 - Reverse Direction: TT-PE to ST-PE 141 - Forwarding Direction: Direction of control plane, signaling flow 142 - Pseudo wire Routing (PW routing). The dynamic placement of SS-PWs 143 that compose an MS-PW, as well as the automatic selection of S- 144 PEs. 146 4.3. Architecture Overview 148 The following figure describes the reference models which are derived 149 from [MS-ARCH] to support PW emulated services across multi-segment 150 PWs. 152 Native |<-------------Pseudo Wire----------->| Native 153 Service | | Service 154 (AC) | |<-PSN1-->| |<-PSN2-->| | (AC) 155 | V V V V V V | 156 | +-----+ +-----+ +-----+ 157 +----+ | |T-PE1|=========|S-PE1|=========|T-PE2| | +----+ 158 | |-------|.....PW.Seg't1........PW Seg't3......|----------| | 159 | CE1| | | | | | | | | |CE2 | 160 | |-------|.....PW.Seg't2.......|PW Seg't4......|----------| | 161 +----+ | | |=========| |=========| | | +----+ 162 ^ +-----+ +-----+ +-----+ ^ 163 | Provider Edge 1 ^ Provider Edge 2 | 164 | | | 165 | | | 166 | PW switching point | 167 | | 168 |<------------------- Emulated Service -------------------->| 170 Figure 1: PW switching Reference Model 172 Figure 1 shows the architecture for a simple multi-segment case. T- 173 PE1 and T-PE2 provide PWE3 to CE1 and CE2. These PEs reside in 174 different PSNs. A PSN tunnel extends from T-PE1 to S-PE1 across PSN1, 175 and a second PSN tunnel extends from S-PE1 to T-PE2 across PSN2. PWs 176 are used to connect the attachment circuits (ACs) attached to T-PE1 177 to the corresponding AC attached to T-PE2. A PW on the tunnel across 178 PSN1 is connected to a PW in the tunnel across PSN2 at S-PE1 to 179 complete the multi-segment PW (MS-PW) between T-PE1 and T-PE2. S-PE1 180 is therefore the PW switching point and will be referred to as the PW 181 switching provider edge (S-PE). PW Segment 1 and PW Segment 3 are 182 segments of the same MS-PW while PW Segment 2 and PW Segment 4 are 183 segments of another pseudo-wire. PW segments of the same MS-PW (e.g., 184 PW1 and PW3) MUST be of the same PW type, and PSN tunnels (e.g., PSN1 185 and PSN2) can be the same or different technology. An S-PE switches 186 an MS-PW from one segment to another based on the PW identifiers. ( 187 PWid , or AII ) How the Pw PDUs are switched at the S-PE depends on 188 the PSN tunnel technology: in case of an MPLS PSN to another MPLS PSN 189 PW switching the operation is a standard MPLs label switch operation. 191 Note that although Figure 1 only shows a single S-PE, a PW may 192 transit more one S-PE along its path. For instance, in the multi- 193 provider case, there can be an S-PE at the border of one provider 194 domain and another S-PE at the border of the other provider domain. 196 5. Applicability 198 In this document we describe the case where the PSNs carrying the 199 SS-PW are only MPLS PSNs using the generalized FEC 129. Interactions 200 with an IP PSN using L2TPv3 as described in [PW-SEG] section 7.4 201 are left for further study. 203 5.1. Requirements Addressed 205 Specifically the following requirements are addressed - see [MS-REQ]: 206 - Dynamic End-to-end Signaling 207 - Scalability and Inter-domain Signaling and Routing 208 - Minimal number of provisioning touches (provisioning only at the 209 T-PEs) 210 - Same set of T-PEs/S-PEs for both directions of a MS-PWs 211 - QoS Signaling, Call Admission Control 212 - Resiliency 213 - End-to-end negotiation of OAM Capability 215 5.2. Changes to Existing PW Signaling 217 The procedures described in this document make use of existing LDP 218 TLVs and related PW signaling procedures described in [RFC4447] and 219 [PW-SEG]. Only an optional Bandwidth TLV is added to address the QoS 220 Signaling requirements (see "MS-PW Next Hop Bandwidth Signaling" 221 section for details). 223 6. PW layer 2 addressing 225 Single segment pseudo wires on an MPLS PSN use Attachment circuit 226 identifiers for a PW using FEC 129. In the case of an automatically 227 placed MS-PW, there is a requirement to have individual global 228 addresses assigned to PW attachment circuits, for reachability , and 229 manageability of the PW. Referencing figure 1 above, individual 230 globally unique addresses MUST be allocated to all the ACs , and S- 231 PEs composing an MS-PW. 233 6.1. Attachment Circuit Addressing 235 The attachment circuit addressing is derived from [AII] AII type 2 236 shown here: 238 0 1 2 3 239 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 | AII Type=02 | Length | Global ID | 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | Global ID (contd.) | Prefix | 244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 | Prefix (contd.) | AC ID | 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | AC ID | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 Implementations of the following procedure MUST interpret the AII 251 type to determine the meaning of the address format of the AII, 252 irrespective of the number of segments in the MS-PW. 254 A unique combination Global ID, Prefix, and AC ID parts of the AII 255 type 2 will be assigned to each AC. In general the same global ID and 256 prefix will be assigned for all ACs belonging to the same T-PE, 257 however this is not a strict requirement. A particular T-PE might 258 have more than one prefix assigned to it, and likewise a fully 259 qualified AII with the same Global ID/Prefix but different AC IDs 260 might belong to different T-PEs. 262 For the purpose of MS-PW the AII MUST be globally unique across all 263 interconnected PW domains. 265 6.2. S-PE addressing 267 The T-PE may elect to select a known specific path along a set of S- 268 PEs for a specific PW. This requires that each S-PE be uniquely 269 addressable in terms of pseudo wires. For this purpose at least one 270 AI address of the format similar to AII type 2 [AII] composed of the 271 Global ID, and Prefix part only MUST be assigned to each S-PE. 273 7. Dynamic placement of MS-PWs 275 [PW-SEG] describes a procedure for connecting multiple pseudo wires 276 together. This procedure requires each S-PE to be manually configured 277 with the information required to terminate and initiate the SS-PW 278 part of the MS-PW. The procedures in the following sections describe 279 an method to extend [PW-SEG] by allowing the automatic selection of 280 pre-defined S-PEs, and automatically setting up a MS-PW between two 281 T-PEs. 283 In this document we consider the case where the PSNs carrying the 284 SS-PW are only MPLS PSNs using the generalized FEC 129. Interactions 285 with an IP PSN using L2TPv3 as described in [PW-SEG] section 7.4 are 286 left for further study. 288 7.1. Pseudo wire routing procedures 290 The AII type 2 described above contains a Global ID, Prefix, and AC 291 ID. The TAII is used by S-PEs to determine the next SS-PW destination 292 for LDP signaling. 294 Once an S-PE receives a PW Setup message containing a TAII with an 295 AII that is not locally present, the S-PE performs a lookup in a 296 local Layer 2 AII PW routing table. If this lookup results in an IP 297 address of the next PE that advertised reachability information for 298 the AII in question, then the S-PE will initiate the necessary LDP 299 messaging procedure for setting up the next PW segment. If the AII PW 300 routing table lookup does not result in a IP address of the next PE, 301 the destination AII has become unreachable, and the PW MUST fail to 302 setup. In this case a label release MUST be returned to the T-PE with 303 a status message of "AII Unreachable". 305 T-PEs that receive a status message of "AII Unreachable" MAY attempt 306 to establish the MS-PW at a later time or via an alternative next 307 hop. Such alternate routing procedures are beyind the scope of this 308 document. 310 To allow for dynamic end-to-end signaling of MS-PWs, information must 311 be present in S-PEs to support the determination of the next PW 312 signaling hop. Such information can be provisioned (static route 313 equivalent) on each S-PE system or disseminated via regular routing 314 protocols (e.g. BGP). 316 7.1.1. AII PW routing table Lookup aggregation rules 318 All PEs capable of dynamic multi segment pseudowire path selection, 319 must build a PW routing table to be used for PW next hop selection. 321 The PW addressing scheme (AII type 2 in [AII]) consists of a Global 322 Id, a 32 bit prefix and a 32 bit Attachment Circuit ID. 324 An aggregation scheme similar with the one used for classless IPv4 325 addresses can be employed. An (8 bits) length mask is specified as a 326 number ranging from 0 to 96 that indicates which Least Significant 327 Bits (LSB) are ignored in the address field when performing the PW 328 address matching algorithm. 330 0 31 32 63 64 95 (bits) 331 +-----------+--------+--------+ 332 | Global ID | Prefix | AC ID | 333 +-----------+--------+--------+ 335 During the signaling phase, the content of the (fully qualified) TAII 336 type 2 field from the FEC129 TLV is compared against routes from the 337 PW Routing table. Similar with the IPv4 case, the route with the 338 longest match is selected, determining the next signaling hop and 339 implicitly the next PW Segment to be signaled. 341 7.1.2. PW Static Route 343 For the purpose of determining the next signaling hop for a segment 344 of the pseudo wire, the PEs MAY be provisioned with fixed route 345 entries in the PW next hop routing table. The static PW entries will 346 follow all the addressing rules and aggregation rules described in 347 the previous sections. The most common use of PW static provisioned 348 routes is this example of the "default" route entry as follows: 350 Global ID = 0 Prefix = 0 AC ID = 0 , Prefix Length = 0 Next Signaling 351 Hop = S-PE1 353 7.1.3. Dynamic advertisement with BGP 355 Any suitable routing protocol capable of carrying external routing 356 information may be used to propagate MS-PW path information among S- 357 PE, and T-PE. However, T-PE, and S-PEs, MAY choose to use [RFC2858] 358 to propagate PW address information throughout the PSN. 360 In the case of the MS-PW if the Source T-PE knows a priori the 361 address of the Terminating T-PE, there is no need to advertise a 362 "fully qualified" address on a per PW Attachment Circuit. Only the 363 T-PE Global ID, Prefix, and prefix length needs to be advertised as 364 part of well known BGP procedures - see [RFC2858] and, [L2VPN-SIG]. 366 As PW Endpoints are provisioned in the T-PEs, the ST-PE will use this 367 information to obtain the first S-PE hop (i.e., first BGP next hop) 368 where the first PW segment will be established and subsequent S-PEs 369 will use the same information (i.e. the next BGP next-hop(s)) to 370 obtain the next-signaling-hop(s) on the path to the TT-PE. 372 The PW dynamic path NLRI is advertised in BGP UPDATE messages using 373 the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC2858]. The [AFI, 374 SAFI] value pair used to identify this NLRI is (AFI=25, SAFI=TBD). 376 The Next Hop field of MP_REACH_NLRI attribute shall be interpreted as 377 an IPv4 address, whenever the length of NextHop address is 4 octets, 378 and as a IPv6 address, whenever the length of the NextHop address is 379 16 octets. 381 The NLRI field in the MP_REACH_NLRI and MP_UNREACH_NLRI is a prefix 382 of 0 to 96 bits encoded as defined in section 4 of [RFC2858]. 384 This prefix is structured as follows: 386 0 31 32 63 64 95 (bits) 387 +-----------+--------+--------+ 388 | Global ID | Prefix | AC ID | 389 +-----------+--------+--------+ 391 Except for the default PW route, which is encoded as a 0 length 392 prefix, the minimum prefix length is 32 bits. 394 7.2. LDP Signaling 396 The LDP signaling procedures are described in [RFC4447] and expanded 397 in [PW-SEG]. No new LDP Signaling components are required for setting 398 up a basic automatically placed MS-PW. However some optional 399 signaling extensions are described below. In additional, optional 400 signalling extentions described in [PW-SEG] MAY be used, including 401 the PW Switching Point TLV for recording the switching points through 402 which a MS PW passes. 404 7.2.1. MS-PW Bandwidth Signaling 406 In the SS-PW case the PW QoS requirements may easily be met by 407 selecting a MPLS PSN tunnel at the S-PE that meets the PW QoS 408 requirements. However in the case of an automatically placed MS-PW 409 the QoS requirements for a SS-PW not initiating on a T-PE MAY need to 410 be indicated along with the MS-PW addressing. This is accomplished by 411 including an OPTIONAL PW Bandwidth TLV. The PW Bandwidth TLV is 412 specified as follows: 414 0 1 2 3 415 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 |1|0| PW BW TLV (0x096E) | TLV Length | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 | Forward SENDER_TSPEC | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 | Reverse SENDER_TSPEC | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 424 The complete definitions of the content of the SENDER_TSPEC objects 425 are found in [TSPEC] section 3.1. The forward SENDER_TSPEC refers to 426 the datapath in the direction of ST-PE to TT-PE. The reverse 427 SENDER_TSPEC refers to the data path in the direction TT-PE to ST-PE. 429 In the forward direction, after a next hop selection is determined, a 430 T/S-PE SHOULD reference the forward SENDER_TSPEC object to determine 431 an appropriate PSN tunnel towards the next signaling hop. If such a 432 tunnel exists, the MS-PW signaling procedures are invoked with the 433 inclusion of the PW Bandwidth TLV. 435 When an S/T-PE receives a PW Bandwidth TLV, once the PW next hop is 436 selected, the S/T-PE MUST request the appropriate resources from the 437 PSN. The resources described in the reverse SENDER_TSPEC are 438 allocated from the PSN toward the originator of the message or 439 previous hop. When resources are allocated from the PSN for a 440 specific PW, then the PSN SHOULD account for the PW usage of the 441 resources. 443 In the case where PSN resources towards the previous hop are not 444 available the following procedure MUST be followed: 445 -i. The PSN MAY allocate more QoS resources, e.g. Bandwidth, to 446 the PSN tunnel. 447 -ii. The S-PE MAY attempt to setup another PSN tunnel to 448 accommodate the new PW QoS requirements. 450 -iii. If the S-PE cannot get enough resources to setup the segment 451 in the MS-PW a label release MUST be returned to the 452 previous hop with a status message of "Bandwidth resources 453 unavailable" 455 In the latter case, the T-PE receiving the status message MUST also 456 withdraw the corresponding PW label mapping for the opposite 457 direction if it has already been successfully setup. 459 If an ST-PE receives a label mapping message the following procedure 460 MUST be followed: 462 If the ST-PE has already sent a label mapping message for this PW 463 then the ST-PE must check that this label mapping message originated 464 from the same LDP peer to which the corresponding label mapping 465 message for this particular PW was sent. If it is the same peer, the 466 the PW is established. If it is a different peer, then ST-PE MUST 467 send a label release message, with a status code of "Duplicate AII" 468 to the PE that originate the LDP label mapping message. 470 If the PE has not yet sent a label mapping message for this 471 particular PW , then it MUST send the label mapping message to this 472 same LDP peer, regardless of what the PW TAII routing lookup result 473 is. 475 7.2.2. Active/Passive T-PE Election Procedure 477 When a MS-PW is signaled, Each T-PE might independently start 478 signaling the MS-PW, this could result in a different path selected 479 for each T-PE PW. To avoid this situation one of the T-PE MUST start 480 the PW signaling ( active role ), while the other waits to receive 481 the LDP label mapping before sending the respective PW LDP label 482 mapping message. ( passive role ). The Active T-PE (the ST-PE) and 483 the passive T-PE (the TT-PE) MUST be identified before signaling is 484 initiated for a given MS-PW. 486 The determination of which T-PE assume the active role SHOULD be done 487 as follows: the SAII and TAII are compared as unsigned integers, if 488 the SAII is bigger then the T-PE assumes the active role. 490 The selection process to determine which T-PE assumes the active role 491 MAY be superseded by manual provisioning. 493 7.2.3. Detailed Signaling Procedures 495 On receiving a label mapping message, the S-PE MUST inspect the FEC 496 TLV. If the receiving node has no local AII matching the TAII for 497 that label mapping then the S-PE will check if the FEC is already 498 installed for the forward direction: 499 - If it is already installed, and the received mapping was received 500 from the same LDP peer where the forward LDP label mapping was 501 sent, then this label mapping represents signaling in the reverse 502 direction for this MS-PW segment. 503 - Otherwise this represents signaling in the forward direction. 505 For the forward direction: 506 -i. Determine the next hop S-PE or T-PE according to the 507 procedures above. 508 -ii. Check that a PSN tunnel exists to the next hop S-PE or T-PE. 509 If no tunnel exists to the next hop S-PE or T-PE the S-PE 510 MAY attempt to setup a PSN tunnel. 511 -iii. Check that a PSN tunnel exists to the previous hop. If no 512 tunnel exists to the previous hop S-PE or T-PE the S-PE MAY 513 attempt to setup a PSN tunnel. 514 -iv. If the S-PE cannot get enough PSN resources to setup the 515 segment to the next or previous S-PE or T-PE, a label 516 release MUST be returned to the T-PE with a status message 517 of "Resources Unavailable". 518 -v. If the label mapping message contains a Bandwidth TLV, 519 allocate the required resources on the PSN tunnels in the 520 forward and reverse directions according to the procedures 521 above. 522 -vi. Allocate a new PW label for the forward direction. 523 -vii. Install the FEC for the forward direction. 524 -viii. Send the label mapping message with the new forward label 525 and the FEC to the next hop S-PE/T-PE. 527 For the reverse direction: 528 -i. Install the received FEC for the reverse direction. 529 -ii. Determine the next signaling hop by referencing the LDP 530 sessions used to setup the LSP in the Forward direction. 531 -iii. Allocate a new PW label for the reverse direction. 532 -iv. Install the FEC for the reverse direction. 533 -v. Send the label mapping message with a new label and the FEC 534 to the next hop S-PE/ST-PE. 536 7.2.4. Support for Explicit PW Path 538 The Explicit Route TLV format defined in [RFC3212] section 4.1 MAY be 539 used to signal an explicit path for a MS-PW. An Explicit PW path may 540 be required to provide a simple solution for 1:1 protection with 541 diverse primary and backup path or to enable controlled signaling 542 (strict or loose) for special PWs. Details of its usage to be 543 provided in a future version. 545 8. Failure Handling Procedures 547 8.1. PSN Failures 549 Failures of the PSN tunnel MUST be handled by PSN mechanisms. If the 550 PSN is unable to re-establish the PSN tunnel, then the S-PE SHOULD 551 follow the procedures defined in Section 8 of [PW-SEG]. 553 8.2. S-PE Failures 555 For defects in an S-PE, the procedures defined in [PW-SEG] SHOULD be 556 followed. However the ST-PE MAY re-signal the PW if an alternate 557 path is available. 559 9. Operations and Maintenance (OAM) 561 The OAM procedures defined in [PW-SEG] may be used also for MS-PWs. A 562 PW switching point TLV is used [PW-SEG] to record the switching 563 points that the PW traverses. 565 In the case of a MS-PW where the PW Endpoints are identified though 566 using a globally unique, FEC 129-based AII addresses, there is no 567 PWID defined on a per segment basis. Each individual PW segment is 568 identified by the address of adjacent S-PE(s) in conjunction with the 569 SAII and TAII. In this case, the following type MUST be used in place 570 of type 0x01 in the PW switching point TLV: 572 Type Length Description 573 0x04 8 Global ID/Prefix of the S-PE 575 The above field MUST be included together with type 0x02 in the TLV 576 once per individual PW Switching Point following the same rules and 577 procedures as described in [PW-SEG]. 579 10. Security Considerations 581 This document specifies only extensions to the protocols already 582 defined in [RFC4447], and [PW-SEG]. Each such protocol may have its 583 own set of security issues, but those issues are not affected by the 584 extensions specified herein. Note that the protocols for dynamically 585 distributing PW Layer 2 reachability information may have their own 586 security issues, however those protocols specifications are outside 587 the scope of this document. 589 11. IANA Considerations 591 This document uses several new LDP TLV types, IANA already maintains 592 a registry of name "TLV TYPE NAME SPACE" defined by RFC3036. The 593 following value is suggested for assignment: 595 TLV type Description 596 0x096E Bandwidth TLV 598 11.1. LDP Status Codes 600 This document uses several new LDP status codes, IANA already 601 maintains a registry of name "STATUS CODE NAME SPACE" defined by 602 RFC3036. The following value are suggested for assignment: 604 Range/Value E Description Reference 605 ------------- ----- ---------------------- --------- 606 0x00000037 0 Bandwidth resources unavailable RFCxxxx 607 0x00000038 0 Resources Unavailable RFCxxxx 608 0x00000039 0 AII Unreachable RFCxxxx 610 11.2. BGP SAFI 612 IANA needs to allocate a new BGP SAFI for "Pseudo Wire routing 613 information" from the L2VPN SAFI registry. 615 12. Full Copyright Statement 617 Copyright (C) The IETF Trust (2007). 619 This document is subject to the rights, licenses and restrictions 620 contained in BCP 78, and except as set forth therein, the authors 621 retain all their rights. 623 This document and the information contained herein are provided on an 624 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 625 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 626 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 627 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 628 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 629 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 631 13. Intellectual Property Statement 633 The IETF takes no position regarding the validity or scope of any 634 Intellectual Property Rights or other rights that might be claimed to 635 pertain to the implementation or use of the technology described in 636 this document or the extent to which any license under such rights 637 might or might not be available; nor does it represent that it has 638 made any independent effort to identify any such rights. Information 639 on the procedures with respect to rights in RFC documents can be 640 found in BCP 78 and BCP 79. 642 Copies of IPR disclosures made to the IETF Secretariat and any 643 assurances of licenses to be made available, or the result of an 644 attempt made to obtain a general license or permission for the use of 645 such proprietary rights by implementers or users of this 646 specification can be obtained from the IETF on-line IPR repository at 647 http://www.ietf.org/ipr. 649 The IETF invites any interested party to bring to its attention any 650 copyrights, patents or patent applications, or other proprietary 651 rights that may cover technology that may be required to implement 652 this standard. Please address the information to the IETF at ietf- 653 ipr@ietf.org. 655 14. Normative References 657 [PW-SEG] Martini et.al. "Segmented Pseudo Wire", 658 draft-ietf-pwe3-segmented-pw-04.txt, IETF Work in Progress, 659 February 2007 661 [TSPEC] Wroclawski, J. "The Use of RSVP with IETF Integrated 662 Services", RFC 2210, September 1997 664 [RFC3036bis] Andersson, Minei, Thomas. "LDP Specification" 665 draft-ietf-mpls-rfc3036bis-03.txt, IETF Work in Progress, 666 October 2005 668 [RFC4447] "Pseudowire Setup and Maintenance Using the Label 669 Distribution Protocol (LDP)", Martini L.,et al, RFC 4447, 670 June 2005. 672 [AII] "Pseudowire Attachment Identifiers for Aggregation and VPN 673 Autodiscovery", Metz, et al, 674 draft-ietf-pwe3-aii-aggregate-02.txt, February 2007 676 [RFC3212] B. Jamoussi, et al. "Constraint-Based LSP Setup using LDP", 677 RFC3212, January 2002. 679 15. Informative References 681 [MS-REQ] Martini et al, "Requirements for Multi-Segment Pseudowire 682 Emulation Edge-to-Edge (PWE3)", 683 draft-ietf-pwe3-ms-pw-requirements-05.txt, Martini, et al., 684 March 2007 686 [MS-ARCH] Bocci at al, "An Architecture for Multi-Segment Pseudo Wire 687 Emulation Edge-to-Edge", draft-ietf-pwe3-ms-pw-arch-03.txt, 688 June 2007, IETF work in progress 690 [L2VPN-SIG] E. Rosen, et Al. "Provisioning, Autodiscovery, 691 and Signaling in L2VPNs", draft-ietf-l2vpn-signaling-08.txt, 692 May 2006 ( work in progress ) 694 [RFC2858] Bates, T., Rekhter, Y., Chandra, R. and D. Katz, 695 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. 697 16. Author Information 699 Luca Martini 700 Cisco Systems, Inc. 701 9155 East Nichols Avenue, Suite 400 702 Englewood, CO, 80112 703 e-mail: lmartini@cisco.com 705 Matthew Bocci 706 Alcatel-Lucent, 707 Voyager Place 708 Shoppenhangers Road 709 Maidenhead 710 Berks, UK 711 e-mail: matthew.bocci@alcatel-lucent.co.uk 712 Florin Balus 713 Alcatel-Lucent 714 701 E. Middlefield Rd. 715 Mountain View, CA 94043 716 e-mail: florin.balus@alcatel-lucent.com 718 Nabil Bitar 719 Verizon 720 40 Sylvan Road 721 Waltham, MA 02145 722 e-mail: nabil.bitar@verizon.com 724 Himanshu Shah 725 Ciena Corp 726 35 Nagog Park, 727 Acton, MA 01720 728 e-mail: hshah@ciena.com 730 Mustapha Aissaoui 731 Alcatel-Lucent 732 600 March Road 733 Kanata 734 ON, Canada 735 e-mail: mustapha.aissaoui@alcatel-lucent.com 737 Jason Rusmisel 738 Alcatel-Lucent 739 600 March Road 740 Kanata 741 ON, Canada 742 e-mail: Jason.rusmisel@alcatel-lucent.com 744 Yetik Serbest 745 SBC Labs 746 9505 Arboretum Blvd. 747 Austin, TX 78759 748 e-mail: Yetik_serbest@labs.sbc.com 749 Andrew G. Malis 750 Verizon 751 2730 Orchard Parkway 752 San Jose, CA, USA 95134 753 e-mail: Andy.Malis@tellabs.com 755 Chris Metz 756 Cisco Systems, Inc. 757 3700 Cisco Way 758 San Jose, Ca. 95134 759 e-mail: chmetz@cisco.com 761 David McDysan 762 Verizon 763 22001 Loudoun County Pkwy 764 Ashburn, VA, USA 20147 765 e-mail: dave.mcdysan@verizon.com 767 Jeff Sugimoto 768 Nortel 769 3500 Carling Ave. 770 Ottawa, Ontario, CANADA 771 e-mail: sugimoto@nortel.com 773 Mike Duckett 774 Bellsouth 775 Lindbergh Center D481 776 575 Morosgo Dr 777 Atlanta, GA 30324 778 e-mail: mduckett@bellsouth.net 780 Mike Loomis 781 Nortel 782 600, Technology Park Dr 783 Billerica, MA, USA 784 e-mail: mloomis@nortel.com 785 Paul Doolan 786 Mangrove Systems 787 IO Fairfield Blvd 788 Wallingford, CT, USA 06492 789 e-mail: pdoolan@mangrovesystems.com 791 Ping Pan 792 Hammerhead Systems 793 640 Clyde Court 794 Mountain View, CA, USA 94043 795 e-mail: ppan@hammerheadsystems.com 797 Prayson Pate 798 Overture Networks, Inc. 799 507 Airport Blvd, Suite 111 800 Morrisville, NC, USA 27560 801 e-mail: prayson.pate@overturenetworks.com 803 Vasile Radoaca 804 Alcatel-Lucent 805 Optics Divison, Westford, MA, USA 806 email: vasile.radoaca@alcatel-lucent.com 808 Yuichiro Wada 809 NTT Communications 810 3-20-2 Nishi-Shinjuku, Shinjuke-ku 811 Tokyo 163-1421, Japan 812 e-mail: yuichiro.wada@ntt.com 814 Yeongil Seo 815 Korea Telecom Corp. 816 463-1 Jeonmin-dong, Yusung-gu 817 Daejeon, Korea 818 e-mail: syi1@kt.co.kr