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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: January 2008 Matthew Bocci (Ed.) 5 Alcatel-Lucent 6 Florin Balus (Ed.) 7 Alcatel-Lucent 9 July 2007 11 Dynamic Placement of Multi Segment Pseudo Wires 13 draft-ietf-pwe3-dynamic-ms-pw-04.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 ........ 8 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 ............................ 10 69 7.2.2 Active/Passive T-PE Election Procedure ............... 12 70 7.2.3 Detailed Signaling Procedures ........................ 12 71 7.2.4 Support for Explicit PW Path ......................... 13 72 8 Failure Handling Procedures .......................... 14 73 8.1 PSN Failures ......................................... 14 74 8.2 S-PE Reachability 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 ............................................. 16 80 12 Full Copyright Statement ............................. 16 81 13 Intellectual Property Statement ...................... 16 82 14 Normative References ................................. 17 83 15 Informative References ............................... 17 84 16 Author Information ................................... 18 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 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 MS-PW. PW segments of the same MS-PW (e.g., PW 184 segment 1 and PW segment 3) MUST be of the same PW type, and PSN 185 tunnels (e.g., PSN1 and PSN2) can be the same or different 186 technology. An S-PE switches an MS-PW from one segment to another 187 based on the PW identifiers. ( PWid , or AII ) How the Pw PDUs are 188 switched at the S-PE depends on the PSN tunnel technology: in case of 189 an MPLS PSN to another MPLS PSN PW switching the operation is a 190 standard MPLS label switch operation. 192 Note that although Figure 1 only shows a single S-PE, a PW may 193 transit more one S-PE along its path. For instance, in the multi- 194 provider case, there can be an S-PE at the border of one provider 195 domain and another S-PE at the border of the other provider domain. 197 5. Applicability 199 In this document we describe the case where the PSNs carrying the 200 SS-PW are only MPLS PSNs using the generalized FEC 129. Interactions 201 with an IP PSN using L2TPv3 as described in [PW-SEG] section 7.4 are 202 left for further study. 204 5.1. Requirements Addressed 206 Specifically the following requirements are addressed [MS-REQ]: 207 - Dynamic End-to-end Signaling 208 - Scalability and Inter-domain Signaling and Routing 209 - Minimal number of provisioning touches (provisioning only at the 210 T-PEs) 211 - Same set of T-PEs/S-PEs for both directions of a MS-PWs 212 - QoS Signaling, Call Admission Control 213 - Resiliency 214 - End-to-end negotiation of OAM Capability 216 5.2. Changes to Existing PW Signaling 218 The procedures described in this document make use of existing LDP 219 TLVs and related PW signaling procedures described in [RFC4447] and 220 [PW-SEG]. Only an optional Bandwidth TLV is added to address the QoS 221 Signaling requirements (see "MS-PW Next Hop Bandwidth Signaling" 222 section for details). 224 6. PW layer 2 addressing 226 Single segment pseudo wires on an MPLS PSN use Attachment circuit 227 identifiers for a PW using FEC 129. In the case of an automatically 228 placed MS-PW, there is a requirement to have individual global 229 addresses assigned to PW attachment circuits, for reachability , and 230 manageability of the PW. Referencing figure 1 above, individual 231 globally unique addresses MUST be allocated to all the ACs , and S- 232 PEs composing an MS-PW. 234 6.1. Attachment Circuit Addressing 236 The attachment circuit addressing is derived from [AII] AII type 2 237 shown here: 239 0 1 2 3 240 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 1 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 | AII Type=02 | Length | Global ID | 243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 244 | Global ID (contd.) | Prefix | 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 | Prefix (contd.) | AC ID | 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | AC ID | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 Implementations of the following procedure MUST interpret the AII 252 type to determine the meaning of the address format of the AII, 253 irrespective of the number of segments in the MS-PW. 255 A unique combination Global ID, Prefix, and AC ID parts of the AII 256 type 2 will be assigned to each AC. In general the same global ID and 257 prefix will be assigned for all ACs belonging to the same T-PE, 258 however this is not a strict requirement. A particular T-PE might 259 have more than one prefix assigned to it, and likewise a fully 260 qualified AII with the same Global ID/Prefix but different AC IDs 261 might belong to different T-PEs. 263 For the purpose of MS-PW the AII MUST be globally unique across all 264 interconnected PW domains. 266 6.2. S-PE addressing 268 The T-PE may elect to select a known specific path along a set of S- 269 PEs for a specific PW. This requires that each S-PE be uniquely 270 addressable in terms of pseudo wires. For this purpose at least one 271 AI address of the format similar to AII type 2 [AII] composed of the 272 Global ID, and Prefix part only MUST be assigned to each S-PE. 274 7. Dynamic placement of MS-PWs 276 [PW-SEG] describes a procedure for connecting multiple pseudo wires 277 together. This procedure requires each S-PE to be manually configured 278 with the information required to terminate and initiate the SS-PW 279 part of the MS-PW. The procedures in the following sections describe 280 an method to extend [PW-SEG] by allowing the automatic selection of 281 pre-defined S-PEs, and automatically setting up a MS-PW between two 282 T-PEs. 284 7.1. Pseudo wire routing procedures 286 The AII type 2 described above contains a Global ID, Prefix, and AC 287 ID. The TAII is used by S-PEs to determine the next SS-PW destination 288 for LDP signaling. 290 Once an S-PE receives a MS-PW label mapping message containing a TAII 291 with an AII that is not locally present, the S-PE performs a lookup 292 in a local Layer 2 AII PW routing table. If this lookup results in an 293 IP address of the next PE that advertised reachability information 294 for the AII in question, then the S-PE will initiate the necessary 295 LDP messaging procedure for setting up the next PW segment. If the 296 AII PW routing table lookup does not result in a IP address of the 297 next PE, the destination AII has become unreachable, and the PW MUST 298 fail to setup. In this case the next PW segment is considered 299 unprovisioned, and a label release MUST be returned to the T-PE with 300 a status message of "AII Unreachable". 302 If the SAI of a MS-PW label mapping message, received by a PE, 303 contains the prefix of a locally provisioned prefix on that PE, but 304 an AC ID that is not provisioned, then the LDP liberal label 305 retention procedures apply, and the label mapping message is 306 retained. 308 To allow for dynamic end-to-end signaling of MS-PWs, information must 309 be present in S-PEs to support the determination of the next PW 310 signaling hop. Such information can be provisioned (static route 311 equivalent) on each S-PE system or disseminated via regular routing 312 protocols (e.g. BGP). 314 7.1.1. AII PW routing table Lookup aggregation rules 316 All PEs capable of dynamic multi segment pseudowire path selection, 317 must build a PW routing table to be used for PW next hop selection. 319 The PW addressing scheme (AII type 2 in [AII]) consists of a Global 320 Id, a 32 bit prefix and a 32 bit Attachment Circuit ID. 322 An aggregation scheme similar with the one used for classless IPv4 323 addresses can be employed. An (8 bits) length mask is specified as a 324 number ranging from 0 to 96 that indicates which Least Significant 325 Bits (LSB) are ignored in the address field when performing the PW 326 address matching algorithm. 328 0 31 32 63 64 95 (bits) 329 +-----------+--------+--------+ 330 | Global ID | Prefix | AC ID | 331 +-----------+--------+--------+ 333 During the signaling phase, the content of the (fully qualified) TAII 334 type 2 field from the FEC129 TLV is compared against routes from the 335 PW Routing table. Similar with the IPv4 case, the route with the 336 longest match is selected, determining the next signaling hop and 337 implicitly the next PW Segment to be signaled. 339 7.1.2. PW Static Route 341 For the purpose of determining the next signaling hop for a segment 342 of the pseudo wire, the PEs MAY be provisioned with fixed route 343 entries in the PW next hop routing table. The static PW entries will 344 follow all the addressing rules and aggregation rules described in 345 the previous sections. The most common use of PW static provisioned 346 routes is this example of the "default" route entry as follows: 348 Global ID = 0 Prefix = 0 AC ID = 0 , Prefix Length = 0 Next Signaling 349 Hop = S-PE1 351 7.1.3. Dynamic advertisement with BGP 353 Any suitable routing protocol capable of carrying external routing 354 information may be used to propagate MS-PW path information among S- 355 PE, and T-PE. However, T-PE, and S-PEs, MAY choose to use Boundary 356 Gateway Protocol (BGP) [RFC2858] to propagate PW address information 357 throughout the PSN. 359 In the case of the MS-PW if the Source T-PE knows a priori the 360 address of the Terminating T-PE, there is no need to advertise a 361 "fully qualified" address on a per PW Attachment Circuit. Only the 362 T-PE Global ID, Prefix, and prefix length needs to be advertised as 363 part of well known BGP procedures - see [RFC2858]. 365 As PW Endpoints are provisioned in the T-PEs. The ST-PE will use this 366 information to obtain the first S-PE hop (i.e., first BGP next hop) 367 to where the first PW segment will be established. Any subsequent S- 368 PEs will use the same information (i.e. the next BGP next-hop(s)) to 369 obtain the next-signaling-hop(s) on the path to the TT-PE. 371 The PW dynamic path NLRI is advertised in BGP UPDATE messages using 372 the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC2858]. The [AFI, 373 SAFI] value pair used to identify this NLRI is (AFI=25, SAFI=6 374 (pending IANA allocation)). 376 The Next Hop field of MP_REACH_NLRI attribute shall be interpreted as 377 an IPv4 address, whenever the length of the NextHop address is 4 378 octets, and as a IPv6 address, whenever the length of the NextHop 379 address is 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. Prefix lengths of 65 to 393 95 are invalid as the AC ID field cannot be aggregated. 395 7.2. LDP Signaling 397 The LDP signaling procedures are described in [RFC4447] and expanded 398 in [PW-SEG]. No new LDP Signaling components are required for setting 399 up a dynamically placed MS-PW. However some optional signaling 400 extensions are described below. 402 7.2.1. MS-PW Bandwidth Signaling 404 In the SS-PW case the PW QoS requirements may easily be met by 405 selecting a MPLS PSN tunnel at the S-PE that meets the PW QoS 406 requirements. However in the case of an automatically placed MS-PW 407 the QoS requirements for a SS-PW not initiating on a T-PE MAY need to 408 be indicated along with the MS-PW addressing. This is accomplished by 409 including an OPTIONAL PW Bandwidth TLV. The PW Bandwidth TLV is 410 specified as follows: 412 0 1 2 3 413 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 1 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 |1|0| PW BW TLV (0x096E) | TLV Length | 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | Forward SENDER_TSPEC | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 | Reverse SENDER_TSPEC | 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 422 The complete definitions of the content of the SENDER_TSPEC objects 423 are found in [TSPEC] section 3.1. The forward SENDER_TSPEC refers to 424 the data path in the direction of ST-PE to TT-PE. The reverse 425 SENDER_TSPEC refers to the data path in the direction TT-PE to ST-PE. 427 In the forward direction, after a next hop selection is determined, a 428 T/S-PE SHOULD reference the forward SENDER_TSPEC object to determine 429 an appropriate PSN tunnel towards the next signaling hop. If such a 430 tunnel exists, the MS-PW signaling procedures are invoked with the 431 inclusion of the PW Bandwidth TLV. When the PE searches for a PSN 432 tunnel, any tunnel which points to a next hop equivalent to the next 433 hop selected will be included in the search.(The LDP address TLV is 434 used to determine the next hop equivalence) 436 When an S/T-PE receives a PW Bandwidth TLV, once the PW next hop is 437 selected, the S/T-PE MUST request the appropriate resources from the 438 PSN. The resources described in the reverse SENDER_TSPEC are 439 allocated from the PSN toward the originator of the message or 440 previous hop. When resources are allocated from the PSN for a 441 specific PW, then the PSN SHOULD account for the PW usage of the 442 resources. 444 In the case where PSN resources towards the previous hop are not 445 available the following procedure MUST be followed: 446 -i. The PSN MAY allocate more QoS resources, e.g. Bandwidth, to 447 the PSN tunnel. 448 -ii. The S-PE MAY attempt to setup another PSN tunnel to 449 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 the 481 LDP label mapping before sending the respective PW LDP label mapping 482 message. (passive role). The Active T-PE (the ST-PE) and the passive 483 T-PE (the TT-PE) MUST be identified before signaling is initiated for 484 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. 504 - Otherwise this represents signaling in the forward direction. 506 For the forward direction: 507 -i. Determine the next hop S-PE or T-PE according to the 508 procedures above. 509 -ii. Check that a PSN tunnel exists to the next hop S-PE or T-PE. 510 If no tunnel exists to the next hop S-PE or T-PE the S-PE 511 MAY attempt to setup a PSN tunnel. 512 -iii. Check that a PSN tunnel exists to the previous hop. If no 513 tunnel exists to the previous hop S-PE or T-PE the S-PE MAY 514 attempt to setup a PSN tunnel. 515 -iv. If the S-PE cannot get enough PSN resources to setup the 516 segment to the next or previous S-PE or T-PE, a label 517 release MUST be returned to the T-PE with a status message 518 of "Resources Unavailable". 519 -v. If the label mapping message contains a Bandwidth TLV, 520 allocate the required resources on the PSN tunnels in the 521 forward and reverse directions according to the procedures 522 above. 523 -vi. Allocate a new PW label for the forward direction. 524 -vii. Install the FEC for the forward direction. 525 -viii. Send the label mapping message with the new forward label 526 and the FEC to the next hop S-PE/T-PE. 528 For the reverse direction: 529 -i. Install the received FEC for the reverse direction. 530 -ii. Determine the next signaling hop by referencing the LDP 531 sessions used to setup the LSP in the Forward direction. 532 -iii. Allocate a new PW label for the reverse direction. 533 -iv. Install the FEC for the reverse direction. 534 -v. Send the label mapping message with a new label and the FEC 535 to the next hop S-PE/ST-PE. 537 7.2.4. Support for Explicit PW Path 539 The Explicit Route TLV format defined in [RFC3212] section 4.1 MAY be 540 used to signal an explicit path for a MS-PW. An Explicit PW path may 541 be required to provide a simple solution for 1:1 protection with 542 diverse primary and backup path or to enable controlled signaling 543 (strict or loose) for special PWs. Details of its usage to be 544 provided in a future study. 546 8. Failure Handling Procedures 548 8.1. PSN Failures 550 Failures of the PSN tunnel MUST be handled by PSN mechanisms. If the 551 PSN is unable to re-establish the PSN tunnel, then the S-PE SHOULD 552 follow the procedures defined in Section 8 of [PW-SEG]. 554 8.2. S-PE Reachability Failures 556 For defects in an S-PE, the procedures defined in [PW-SEG] SHOULD be 557 followed. However in general an established MS-PW will not be 558 affected by changes in L2 PW reachability information. 560 T-PEs that receive a label release message with a status of "AII 561 Unreachable" MUST re-attempt to establish the PW immediately. However 562 the T-PE MUST throttle its PW setup message retry attempts with an 563 exponential backoff in situations where PW setup messages are being 564 constantly released. It is also recommended that a T-PE detecting 565 such a situation take action to notify an operator. 567 If there is a change in the L2 PW reachability information in the 568 forward direction only, the T-PE MAY elect to tear down the MS-PW by 569 sending a label withdraw message and re-establish the MS-PW. In the 570 same case, an S-PE MAY do the same by sending a label withdraw 571 message in the forward direction, and a label release message in the 572 opposite direction along the MS-PW. 574 A change in L2 reachability information in the reverse direction has 575 no effect on an MS-PW. 577 9. Operations and Maintenance (OAM) 579 The OAM procedures defined in [PW-SEG] may be used also for MS-PWs. A 580 PW switching point TLV is used [PW-SEG] to record the switching 581 points that the PW traverses. 583 In the case of a MS-PW where the PW Endpoints are identified though 584 using a globally unique, FEC 129-based AII addresses, there is no 585 PWID defined on a per segment basis. Each individual PW segment is 586 identified by the address of adjacent S-PE(s) in conjunction with the 587 SAI and TAI. In this case, the following type MUST be used in place 588 of type 0x01 in the PW switching point TLV: 590 Type Length Description 591 0x06 8 L2 PW address of PW Switching Point 593 The above field MUST be included together with type 0x02 in the TLV 594 once per individual PW Switching Point following the same rules and 595 procedures as described in [PW-SEG]. 597 10. Security Considerations 599 This document specifies only extensions to the protocols already 600 defined in [RFC4447], and [PW-SEG]. Each such protocol may have its 601 own set of security issues, but those issues are not affected by the 602 extensions specified herein. Note that the protocols for dynamically 603 distributing PW Layer 2 reachability information may have their own 604 security issues, however those protocols specifications are outside 605 the scope of this document. 607 11. IANA Considerations 609 This document uses several new LDP TLV types, IANA already maintains 610 a registry of name "TLV TYPE NAME SPACE" defined by RFC3036. The 611 following value is suggested for assignment: 613 TLV type Description 614 0x096E Bandwidth TLV 616 11.1. LDP Status Codes 618 This document uses several new LDP status codes, IANA already 619 maintains a registry of name "STATUS CODE NAME SPACE" defined by 620 RFC3036. The following value are suggested for assignment: 622 Range/Value E Description Reference 623 ------------- ----- ---------------------- --------- 624 0x00000037 0 Bandwidth resources unavailable RFCxxxx 625 0x00000038 0 Resources Unavailable RFCxxxx 626 0x00000039 0 AII Unreachable RFCxxxx 627 0x0000003A 0 PW Loop Detected RFCxxxx 629 11.2. BGP SAFI 631 IANA needs to allocate a new BGP SAFI for "Network Layer Reachability 632 Information used for Dynamic Placement of Multi-Segment Pseudiwires" 633 from the L2VPN SAFI registry. The following aloocation is suggested: 635 Value Description Reference 636 ----- ----------- --------- 637 6 Network Layer Reachability Information used [RFCxxxx] 638 for Dynamic Placement of Multi-Segment 639 Pseudowires 641 12. Full Copyright Statement 643 Copyright (C) The IETF Trust (2007). 645 This document is subject to the rights, licenses and restrictions 646 contained in BCP 78, and except as set forth therein, the authors 647 retain all their rights. 649 This document and the information contained herein are provided on an 650 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 651 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 652 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 653 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 654 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 655 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 657 13. Intellectual Property Statement 659 The IETF takes no position regarding the validity or scope of any 660 Intellectual Property Rights or other rights that might be claimed to 661 pertain to the implementation or use of the technology described in 662 this document or the extent to which any license under such rights 663 might or might not be available; nor does it represent that it has 664 made any independent effort to identify any such rights. Information 665 on the procedures with respect to rights in RFC documents can be 666 found in BCP 78 and BCP 79. 668 Copies of IPR disclosures made to the IETF Secretariat and any 669 assurances of licenses to be made available, or the result of an 670 attempt made to obtain a general license or permission for the use of 671 such proprietary rights by implementers or users of this 672 specification can be obtained from the IETF on-line IPR repository at 673 http://www.ietf.org/ipr. 675 The IETF invites any interested party to bring to its attention any 676 copyrights, patents or patent applications, or other proprietary 677 rights that may cover technology that may be required to implement 678 this standard. Please address the information to the IETF at ietf- 679 ipr@ietf.org. 681 14. Normative References 683 [PW-SEG] Martini et.al. "Segmented Pseudo Wire", 684 draft-ietf-pwe3-segmented-pw-04.txt, IETF Work in Progress, 685 February 2007 687 [TSPEC] Wroclawski, J. "The Use of RSVP with IETF Integrated 688 Services", RFC 2210, September 1997 690 [RFC3036bis] Andersson, Minei, Thomas. "LDP Specification" 691 draft-ietf-mpls-rfc3036bis-03.txt, IETF Work in Progress, 692 October 2005 694 [RFC4447] "Pseudowire Setup and Maintenance Using the Label 695 Distribution Protocol (LDP)", Martini L.,et al, RFC 4447, 696 June 2005. 698 [AII] "Pseudowire Attachment Identifiers for Aggregation and VPN 699 Autodiscovery", Metz, et al, 700 draft-ietf-pwe3-aii-aggregate-02.txt, February 2007 702 [RFC3212] B. Jamoussi, et al. "Constraint-Based LSP Setup using LDP", 703 RFC3212, January 2002. 705 15. Informative References 707 [MS-REQ] Martini et al, "Requirements for Multi-Segment Pseudowire 708 Emulation Edge-to-Edge (PWE3)", 709 draft-ietf-pwe3-ms-pw-requirements-05.txt, Martini, et al., 710 March 2007 712 [MS-ARCH] Bocci at al, "An Architecture for Multi-Segment Pseudo Wire 713 Emulation Edge-to-Edge", draft-ietf-pwe3-ms-pw-arch-03.txt, 714 June 2007, IETF work in progress 716 [RFC2858] Bates, T., Rekhter, Y., Chandra, R. and D. Katz, 717 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. 719 16. Author Information 721 Luca Martini 722 Cisco Systems, Inc. 723 9155 East Nichols Avenue, Suite 400 724 Englewood, CO, 80112 725 e-mail: lmartini@cisco.com 727 Matthew Bocci 728 Alcatel-Lucent, 729 Voyager Place 730 Shoppenhangers Road 731 Maidenhead 732 Berks, UK 733 e-mail: matthew.bocci@alcatel-lucent.co.uk 735 Florin Balus 736 Alcatel-Lucent 737 701 E. Middlefield Rd. 738 Mountain View, CA 94043 739 e-mail: florin.balus@alcatel-lucent.com 741 Nabil Bitar 742 Verizon 743 40 Sylvan Road 744 Waltham, MA 02145 745 e-mail: nabil.bitar@verizon.com 747 Himanshu Shah 748 Ciena Corp 749 35 Nagog Park, 750 Acton, MA 01720 751 e-mail: hshah@ciena.com 753 Mustapha Aissaoui 754 Alcatel-Lucent 755 600 March Road 756 Kanata 757 ON, Canada 758 e-mail: mustapha.aissaoui@alcatel-lucent.com 759 Jason Rusmisel 760 Alcatel-Lucent 761 600 March Road 762 Kanata 763 ON, Canada 764 e-mail: Jason.rusmisel@alcatel-lucent.com 766 Yetik Serbest 767 SBC Labs 768 9505 Arboretum Blvd. 769 Austin, TX 78759 770 e-mail: Yetik_serbest@labs.sbc.com 772 Andrew G. Malis 773 Verizon 774 2730 Orchard Parkway 775 San Jose, CA, USA 95134 776 e-mail: Andy.Malis@tellabs.com 778 Chris Metz 779 Cisco Systems, Inc. 780 3700 Cisco Way 781 San Jose, Ca. 95134 782 e-mail: chmetz@cisco.com 784 David McDysan 785 Verizon 786 22001 Loudoun County Pkwy 787 Ashburn, VA, USA 20147 788 e-mail: dave.mcdysan@verizon.com 790 Jeff Sugimoto 791 Nortel 792 3500 Carling Ave. 793 Ottawa, Ontario, CANADA 794 e-mail: sugimoto@nortel.com 795 Mike Duckett 796 Bellsouth 797 Lindbergh Center D481 798 575 Morosgo Dr 799 Atlanta, GA 30324 800 e-mail: mduckett@bellsouth.net 802 Mike Loomis 803 Nortel 804 600, Technology Park Dr 805 Billerica, MA, USA 806 e-mail: mloomis@nortel.com 808 Paul Doolan 809 Mangrove Systems 810 IO Fairfield Blvd 811 Wallingford, CT, USA 06492 812 e-mail: pdoolan@mangrovesystems.com 814 Ping Pan 815 Hammerhead Systems 816 640 Clyde Court 817 Mountain View, CA, USA 94043 818 e-mail: ppan@hammerheadsystems.com 820 Prayson Pate 821 Overture Networks, Inc. 822 507 Airport Blvd, Suite 111 823 Morrisville, NC, USA 27560 824 e-mail: prayson.pate@overturenetworks.com 826 Vasile Radoaca 827 Alcatel-Lucent 828 Optics Divison, Westford, MA, USA 829 email: vasile.radoaca@alcatel-lucent.com 831 Yuichiro Wada 832 NTT Communications 833 3-20-2 Nishi-Shinjuku, Shinjuke-ku 834 Tokyo 163-1421, Japan 835 e-mail: yuichiro.wada@ntt.com 836 Yeongil Seo 837 Korea Telecom Corp. 838 463-1 Jeonmin-dong, Yusung-gu 839 Daejeon, Korea 840 e-mail: syi1@kt.co.kr