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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Peter Ashwood-Smith (Nortel Networks Corp.) 2 Internet Draft Ayan Banerjee (Calient Networks) 3 Expiration Date: May 2001 Lou Berger (Movaz Networks) 4 Greg Bernstein (Ciena Corporation) 5 John Drake (Calient Networks) 6 Yanhe Fan (Axiowave Networks) 7 Kireeti Kompella (Juniper Networks, Inc.) 8 Eric Mannie (GTS) 9 Jonathan P. Lang (Calient Networks) 10 Bala Rajagopalan (Tellium, Inc.) 11 Yakov Rekhter (Cisco Systems) 12 Debanjan Saha (Tellium, Inc.) 13 Vishal Sharma (Tellabs) 14 George Swallow (Cisco Systems) 15 Z. Bo Tang (Tellium, Inc.) 17 November 2000 19 Generalized MPLS Signaling - RSVP-TE Extensions 21 draft-ietf-mpls-generalized-rsvp-te-00.txt 23 Status of this Memo 25 This document is an Internet-Draft and is in full conformance with 26 all provisions of Section 10 of RFC2026. Internet-Drafts are working 27 documents of the Internet Engineering Task Force (IETF), its areas, 28 and its working groups. Note that other groups may also distribute 29 working documents as Internet-Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 To view the current status of any Internet-Draft, please check the 43 "1id-abstracts.txt" listing contained in an Internet-Drafts Shadow 44 Directory, see http://www.ietf.org/shadow.html. 46 Abstract 48 This document describes extensions to RSVP-TE signaling required to 49 support Generalized MPLS. Generalized MPLS extends MPLS to encompass 50 time-division (e.g. SONET ADMs), wavelength (optical lambdas) and 51 spatial switching (e.g. incoming port or fiber to outgoing port or 52 fiber). This document presents an RSVP-TE specific description of 53 the extensions. A CR-LDP specific description can be found in 54 [GMPLS-LDP]. A generic functional description is presented in 55 [GMPLS-SIG]. 57 Contents 59 1 Introduction .............................................. 3 60 2 Label Related Formats .................................... 3 61 2.1 Generalized Label Request ................................ 3 62 2.1.1 Generalized Label Request with SONET/SDH Label Range ...... 4 63 2.1.2 Procedures ................................................ 4 64 2.1.3 Bandwidth Encoding ........................................ 5 65 2.2 Generalized Label ......................................... 5 66 2.2.1 Procedures ................................................ 6 67 2.3 Waveband Switching ........................................ 6 68 2.3.1 Procedures ................................................ 7 69 2.4 Suggested Label ........................................... 7 70 2.5 Label Set ................................................. 7 71 2.5.1 Procedures ................................................ 8 72 3 Bidirectional LSPs ........................................ 9 73 3.1 Procedures ................................................ 9 74 3.2 Contention Resolution ..................................... 10 75 4 Notification .............................................. 10 76 4.1 Notify Request Object ..................................... 10 77 4.1.1 Required Information ...................................... 11 78 4.1.2 Procedures ................................................ 11 79 4.2 Notify Message ............................................ 12 80 4.2.1 Required Information ...................................... 12 81 4.2.2 Procedures ................................................ 13 82 4.3 Removing State with a PathErr message ..................... 13 83 5 Explicit Label Control .................................... 14 84 5.1 Procedures ................................................ 15 85 6 RSVP Message Formats ...................................... 16 86 7 Acknowledgments ........................................... 17 87 8 Security Considerations ................................... 17 88 9 References ................................................ 18 89 10 Authors' Addresses ........................................ 18 90 Changes from previous version: 92 o Moved protocol specific details into two documents, one for RSVP-TE 93 and one for CR-LDP. 94 o Fixed bandwidth encodings 95 o Revised Notify message format to disambiguate upstream and 96 downstream notifications. 97 o Minor text cleanup 99 1. Introduction 101 Generalized MPLS extends MPLS from supporting packet (PSC) interfaces 102 and switching to include support of three new classes of interfaces 103 and switching: Time-Division Multiplex (TDM), Lambda Switch (LSC) and 104 Fiber-Switch (FSC). A functional description of the extensions to 105 MPLS signaling needed to support the new classes of interfaces and 106 switching is provided in [GMPLS-SIG]. This document presents RSVP-TE 107 specific formats and mechanisms needed to support all four classes of 108 interfaces. CR-LDP extensions can be found in [GMPLS-LDP]. 110 [GMPLS-SIG] should be viewed as a companion document to this 111 document. The format of this document parallels [GMPLS-SIG]. In 112 addition to the other features of Generalized MPLS, this document 113 also defines RSVP-TE specific features to support rapid failure 114 notification, see Section 4. 116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 118 document are to be interpreted as described in [RFC2119]. 120 2. Label Related Formats 122 This section defines formats for a generalized label request, a 123 generalized label, support for waveband switching, suggested label 124 and label sets. 126 2.1. Generalized Label Request 128 A Path message SHOULD contain as specific an LSP Encoding Type as 129 possible to allow the maximum flexibility in switching by transit 130 LSRs. A Generalized Label Request object is set by the ingress node, 131 transparently passed by transit nodes, and used by the egress node. 133 The format of a Generalized Label Request is: 135 0 1 2 3 136 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 1 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | Length | Class-Num (19)|C-Type (4)[TBA]| 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 | LSP Enc. Type |Link Prot.Flags| G-PID | 141 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 143 See [GMPLS-SIG] for a description of parameters. 145 2.1.1. Generalized Label Request with SONET/SDH Label Range 147 The format of a Generalized Label Request with SONET/SDH Label Range 148 (in RSVP) is: 150 0 1 2 3 151 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 1 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | Length | Class-Num (19)|C-Type (5)[TBA]| 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 | LSP Enc. Type |Link Prot.Flags| G-PID | 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 | RGT | RT | Reserved | RNC | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 See [GMPLS-SIG] for a description of parameters. 162 2.1.2. Procedures 164 A node processing the Path message containing the Generalized Label 165 Request must verify that the requested parameters can be satisfied by 166 the incoming interface, the node and by the outgoing interface. The 167 node may either directly support the LSP or it may use a tunnel (FA), 168 i.e., another class of switching. In either case, each parameter 169 must be checked. 171 Note that local node policy dictates when tunnels may be used and 172 when they may be created. Local policy may allow for tunnels to be 173 dynamically established or may be solely administratively controlled. 174 For more information on tunnels and processing of ER hops when using 175 tunnels see [MPLS-HIERARCHY]. 177 Transit and egress nodes MUST verify that the node itself and, where 178 appropriate, that the outgoing interface or tunnel can support the 179 requested LSP Encoding Type. If encoding cannot be supported, the 180 node MUST generate a PathErr message, with a "Routing 181 problem/Unsupported Encoding" indication. 183 Transit nodes MUST verify that the outgoing interface or tunnel can 184 support the requested Link Protection Flags. If it cannot, the node 185 MUST generate a PathErr message, with a "Routing problem/Unsupported 186 Link Protection" indication. 188 The G-PID parameter is normally only examined at the egress. If the 189 indicated G-PID cannot be supported then the egress MUST generate a 190 PathErr message, with a "Routing problem/Unsupported GPID" 191 indication. In the case of PSC and when penultimate hop popping 192 (PHP) is requested, the penultimate hop also examines the (stored) G- 193 PID during the processing of the Resv message. In this case if the 194 G-PID is not supported, then the penultimate hop MUST generate a 195 ResvErr message with a "Routing problem/Unacceptable label value" 196 indication. 198 When an error message is not generated, normal processing occurs. In 199 the transit case this will typically result in a Path message being 200 propagated. In the egress case and PHP special case this will 201 typically result in a Resv message being generated. 203 2.1.3. Bandwidth Encoding 205 Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC 206 objects. See [GMPLS-SIG] for a definition of values to be used for 207 specific signal types. These values are set in the Peak Data Rate 208 field of Int-Serv objects. Other bandwidth/service related 209 parameters in the object are ignored and carried transparently. 211 2.2. Generalized Label 213 The format of a Generalized Label is: 215 0 1 2 3 216 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 1 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 | Length | Class-Num (16)| C-Type (2) | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | Label | 221 | ... | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 See [GMPLS-SIG] for a description of parameters and encoding of 224 SDH, SONET, port, wavelength and other labels. 226 2.2.1. Procedures 228 The Generalized Label travels in the upstream direction in Resv 229 messages. 231 The presence of both a generalized and normal label object in a Resv 232 message is a protocol error and should treated as a malformed message 233 by the recipient. 235 The recipient of a Resv message containing a Generalized Label 236 verifies that the values passed are acceptable. If the label is 237 unacceptable then the recipient MUST generate a ResvErr message with 238 a "Routing problem/MPLS label allocation failure" indication. 240 2.3. Waveband Switching 242 Waveband switching uses the same format as the generalized label, see 243 section 2.2. For compatibility reasons, a new RSVP c-type (3) is 244 assigned for the Waveband Label. 246 In the context of waveband switching, the generalized label has the 247 following format: 249 0 1 2 3 250 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 1 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Length | Class-Num (16)| C-Type (3) | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | Waveband Id | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | Start Label | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | End Label | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 See [GMPLS-SIG] for a description of parameters. 263 2.3.1. Procedures 265 The procedures defined in Section 2.2.1 apply to waveband switching. 266 This includes generating a ResvErr message with a "Routing 267 problem/MPLS label allocation failure" indication if any of the label 268 fields are unrecognized or unacceptable. 270 Additionally, when a waveband is switched to another waveband, it is 271 possible that the wavelengths within the waveband will be mirrored 272 about a center frequency. When this type of switching is employed, 273 the start and end label in the waveband label object MUST be flipped 274 before forwarding the label object with the new waveband Id. In this 275 manner an egress/ingress LSR which receives a waveband label which 276 has these values inverted, knows that it must also invert its egress 277 association to pick up the proper wavelengths. Without this 278 mechanism and with an odd number of mirrored switching operations, 279 the egress LSRs will not know that an input wavelength of say L1 will 280 emerge from the waveband tunnel as L100. 282 This operation MUST be performed in both directions when a 283 bidirectional waveband tunnel is being established. 285 2.4. Suggested Label 287 The format of a suggested label is identical to a generalized label. 288 It is used in Path messages. Suggested Label uses a new Class-Number 289 (TBD of form 10bbbbbb) and the C-type of the label being suggested. 291 Errors in received Suggested Labels MUST be ignored. This includes 292 any received inconsistent or unacceptable values. 294 2.5. Label Set 296 The Label_Set object uses a Class-Number TBA (of form 0bbbbbbb) and 297 the C-type of the label type being described. 299 The format of a Label_Set is: 301 0 1 2 3 302 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 1 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 | Length | Class-Num(TBA)| C-Type (1) | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | Reserved | Label Type | Action | 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 308 | Subchannel 1 | 309 | ... | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 : : : 312 : : : 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 314 | Subchannel N | 315 | ... | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 Label Type: 8 bits 320 Indicates the type and format of the labels carried in the 321 object. Values match the C-Type of the appropriate Label 322 object. 324 See [GMPLS-SIG] for a description of other parameters. 326 2.5.1. Procedures 328 A Label Set is defined via one or more Label_Set objects. Specific 329 labels/subchannels can be added to or excluded from a Label Set via 330 Action zero (0) and one (1) objects respectively. Ranges of 331 labels/subchannels can be added to or excluded from a Label Set via 332 Action two (2) and three (3) objects respectively. When the 333 Label_Set objects only list labels/subchannels to exclude, this 334 implies that all other labels are acceptable. 336 The absence of any Label_Set objects implies that all labels are 337 acceptable. A Label Set is included when a node wishes to restrict 338 the label(s) that may be used downstream. 340 On reception of a Path message a CI-capable interface will restrict 341 its choice of labels to one which is in the Label Set. The CI- 342 capable receiver may also remove the Label Set prior to forwarding 343 the Path message. If the node is unable to pick a label from the 344 Label Set or if there is a problem parsing the Label_Set objects, 345 then the request is terminated and a PathErr message with a "Routing 346 problem/Label Set" indication MUST be generated. It is a local matter 347 if the Label Set is stored for later selection on the Resv or if the 348 selection is made immediately for propagation in the Resv. 350 On reception of a Path message for a CI-incapable interface, the 351 Label Set represented in the message is compared against the set of 352 available labels at the downstream interface and the resulting 353 intersecting Label Set is forwarded in a Path message. When the 354 resulting Label Set is empty, the Path must be terminated, and a 355 PathErr message, and a "Routing problem/Label Set" indication MUST be 356 generated. Note that intersection is based on the physical labels 357 (actual wavelength/band values) which may have different logical 358 values on different links, as a result it is the responsibility of 359 the node to map these values so that they have a consistent physical 360 meaning, or to drop the particular values from the set if no suitable 361 logical label value exists. 363 When processing a Resv message at an intermediate node, the label 364 propagated upstream MUST fall within the Label Set. 366 Note, on reception of a Resv message for an interface which is CI- 367 incapable it has no other choice than to use the same physical label 368 (wavelength/band) as received in the Resv. In this case, the use and 369 propagation of a Label Set will significantly reduce the chances that 370 this allocation will fail when CI-incapable nodes are traversed. 372 3. Bidirectional LSPs 374 Bidirectional LSP setup is indicated by the presence of an Upstream 375 Label in the Path message. An Upstream Label has the same format as 376 the generalized label, see Section 2.2. The Upstream Label uses 377 Class-Number TBD (of form 0bbbbbbb) and the C-type of the label being 378 suggested. 380 3.1. Procedures 382 The process of establishing a bidirectional LSP follows the 383 establishment of a unidirectional LSP with some additions. To 384 support bidirectional LSPs an Upstream Label is added to the Path 385 message. The Upstream Label MUST indicate a label that is valid for 386 forwarding at the time the Path message is sent. 388 When a Path message containing an Upstream Label is received, the 389 receiver first verifies that the upstream label is acceptable. If 390 the label is not acceptable, the receiver MUST issue a PathErr 391 message with a "Routing problem/Unacceptable label value" indication. 393 An intermediate node must also allocate a label on the outgoing 394 interface and establish internal data paths before filling in an 395 outgoing Upstream Label and propagating the Path message. If an 396 intermediate node is unable to allocate a label or internal 397 resources, then it MUST issue a PathErr message with a "Routing 398 problem/Label allocation failure" indication. 400 Terminator nodes process Path messages as usual, with the exception 401 that the upstream label can immediately be used to transport data 402 traffic associated with the LSP upstream towards the initiator. 404 When a bidirectional LSP is removed, both upstream and downstream 405 labels are invalidated and it is no longer valid to send data using 406 the associated labels. 408 3.2. Contention Resolution 410 There are two additional contention resolution related considerations 411 when controlling bidirectional LSPs setup via RSVP-TE. The first is 412 that for the purposes of RSVP contention resolution, the node ID is 413 the IP address used in the RSVP_HOP object. The second is that a 414 neighbor's node ID might not be known when sending an initial Path 415 message. When this case occurs, a node should suggest a label chosen 416 at random from the available label space. 418 4. Notification 420 This section defines three signaling extensions that modify error 421 handling, enable expedited notification of failures and other events 422 to nodes responsible for restoring failed LSPs. The first extension, 423 the Notify Request object, identifies where event notifications are 424 to be sent. The second, the Notify message, provides for general 425 event notification. The final extension allows for the removal of 426 Path state on handling of PathErr messages. 428 4.1. Notify Request Object 430 Notifications may be sent via the Notify message defined below. The 431 Notify Request object is used to request the generation of 432 notifications. Notifications, i.e., the sending of a Notify message, 433 may be requested in both the upstream and downstream directions. 435 4.1.1. Required Information 437 The Notify Request Object may be carried in Path or Resv Messages, 438 see Section 6. The NOTIFY_REQUEST Class-Number is TBA (of form 439 11bbbbbb). The format of a Notify Request is: 441 0 1 2 3 442 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 1 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | Length | Class-Num(TBD)| C-Type (1) | 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | IPv4 Notify Node Address | 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 IPv4 Notify Node Address: 32 bits 451 The IP address of the node that should be notified when 452 generating an error message. 454 If a message contains multiple NOTIFY_REQUEST objects, only the first 455 object is meaningful. Subsequent NOTIFY_REQUEST objects MAY be 456 ignored and SHOULD NOT be propagated. 458 4.1.2. Procedures 460 A Notify Request object may be inserted in Path or Resv messages to 461 indicate the address of a node that should be notified of an LSP 462 failure. As previously mentioned, notifications may be requested in 463 both the upstream and downstream directions. Upstream notification is 464 indicated via the inclusion of a Notify Request Object in the 465 corresponding Path message. Downstream notification is indicated via 466 the inclusion of a Notify Request Object in the corresponding Resv 467 message. 469 A node receiving a message containing a Notify Request object SHOULD 470 store the Notify Node Address in the corresponding state block. If 471 the node is a transit node, it SHOULD also included a Notify Request 472 object in the outgoing Path or Resv message. The outgoing Notify 473 Node Address MAY be updated based on local policy. 475 Note that the inclusion of a Notify Request object does not guarantee 476 that a Notify message will be generated. 478 4.2. Notify Message 480 The Notify message provides a mechanism to inform non-adjacent nodes 481 of LSP related events. Notify messages are only generated after a 482 Notify Request object has been received. The Notify message differs 483 from the currently defined error messages (i.e., PathErr and ResvErr 484 messages of RSVP) in that it can be "targeted" to a node other than 485 the immediate upstream or downstream neighbor and that it is a 486 generalized notification mechanism. The Notify message does not 487 replace existing error messages. The Notify message may be sent 488 either (a) normally, where non-target nodes just forward the Notify 489 message to the target node, similar to ResvConf processing in [RSVP]; 490 or (b) encapsulated in a new IP header whose destination is equal to 491 the target IP address. Regardless of the transmission mechanism, 492 nodes receiving a Notify message not destined to the node forward the 493 message, unmodified, towards the target. 495 To support reliable delivery of the Notify message, an Ack Message 496 [RSVP-RR] is used to acknowledge the receipt of a Notify Message. 497 See [RSVP-RR] for details on reliable RSVP message delivery. 499 4.2.1. Required Information 501 The Notify message is a generalized notification message. The IP 502 destination address is set to the IP address of the intended 503 receiver. The Notify message is sent without the router alert 504 option. A single Notify message may contain notifications being 505 sent, with respect to each listed session, both upstream and 506 downstream. 508 ::= [] 509 511 ::= [ ] 512 | 513 515 ::= [...] 516 518 ::= [...] 519 521 The ERROR_SPEC object specifies the error and includes the IP address 522 of either the node that detected the error or the link that has 523 failed. See ERROR_SPEC definition in [RFC2205]. The MESSAGE_ID 524 object is defined in [RSVP-RR]. 526 4.2.2. Procedures 528 Notify messages are generated at nodes that detect an error that will 529 trigger the generation of a PathErr or ResvErr message. If a PathErr 530 message is to be generated and a Notify Request object has been 531 received in the corresponding Path message, then a Notify message 532 destined to the recorded node SHOULD be generated. If a ResvErr 533 message is to be generated and a Notify Request object has been 534 received in the corresponding Resv message, then a Notify message 535 destined to the recorded node SHOULD be generated. As previously 536 mentioned, a single error may generate a Notify message in both the 537 upstream and downstream directions. Note a Notify message MUST NOT 538 be generated unless an appropriate Notify Request object has been 539 received. 541 When generating Notify messages, a node SHOULD attempt to combine 542 notifications being sent to the same Notify Node and that share the 543 same ERROR_SPEC into a single Notify message. The means by which a 544 node determines which information may be combined is implementation 545 dependent. Implementations may use event, timer based or other 546 approaches. If using a timer based approach, the implementation 547 SHOULD allow the user to configure the interval over which 548 notifications are combined. When using a timer based approach, a 549 default "notification interval" of 1 ms SHOULD be used. Notify 550 messages SHOULD be delivered using the reliable message delivery 551 mechanisms defined in [RSVP-RR]. 553 Upon receiving a Notify message, the Notify Node SHOULD send a 554 corresponding Ack message. 556 4.3. Removing State with a PathErr message 558 The PathErr message as defined in [RFC2205] is sent hop-by-hop to the 559 source of the associated Path message. Intermediate nodes may 560 inspect this message, but take no action upon it. In an environment 561 where Path messages are routed according to an IGP and that route may 562 change dynamically, this behavior is a fine design choice. 564 However, when RSVP is used with explicit routes, it is often the case 565 that errors can only be corrected at the source node or some other 566 node further upstream. In order to clean up resources, the source 567 must receive the PathErr and then either send a PathTear (or wait for 568 the messages to timeout). This causes idle resources to be held 569 longer than necessary increases control message load. In a situation 570 where the control plane is attempting to recover from a serious 571 outage, both the message load and the delay in freeing resources 572 hamper the ability to rapidly reconverge. 574 The situation can be greatly improved by allowing state to be removed 575 by intermediate nodes on certain error conditions. To facilitate 576 this a new flag is defined in the ERROR_SPEC object. The two 577 currently defined ERROR_SPEC objects (IPv4 and IPv6 error spec 578 objects) each contain a one byte flag field. Within that field two 579 flags are defined. This specification defines a third flag, 0x04, 580 Path_State_Removed. 582 The semantics of the Path_State_Removed flag are simply that the node 583 forwarding the error message has removed the Path state associated 584 with the PathErr. By default, the Path_State_Removed flag is always 585 set to zero when generating or forwarding a PathErr message. A node 586 which encounters an error MAY set this flag if the error results in 587 the associated Path state being discarded. If the node setting the 588 flag is not the session endpoint, the node SHOULD generate a 589 corresponding PathTear. A node receiving a PathErr message 590 containing an ERROR_SPEC object with the Path_State_Removed flag set 591 MAY also remove the associated Path state. If the Path state is 592 removed the Path_State_Removed flag SHOULD be set in the outgoing 593 PathErr message. A node which does not remove the associated Path 594 state MUST NOT set the Path_State_Removed flag. A node that receives 595 an error with the Path_State_Removed flag set to zero MUST NOT set 596 this flag unless it also generates a corresponding PathTear message. 598 Note that the use of this flag does not result in any 599 interoperability incompatibilities. 601 5. Explicit Label Control 603 The Label ERO subobject is defined as follows: 605 0 1 2 3 606 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 1 607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 608 |L| Type | Length |U| Reserved | C-Type | 609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 | Label | 611 | ... | 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 614 See [GMPLS-SIG] for a description of L, U and Label parameters. 616 Type 618 3 Label 620 Length 622 The Length contains the total length of the subobject in bytes, 623 including the Type and Length fields. The Length is always 624 divisible by 4. 626 C-Type 628 The C-Type of the included Label Object. Copied from the Label 629 Object. 631 5.1. Procedures 633 The Label subobject follows a subobject containing the IP address, or 634 the interface identifier [MPLS-UNNUM], associated with the link on 635 which it is to be used. The preceding subobject must be a strict 636 object. Up to two label subobjects may be present, one for the 637 downstream label and one for the upstream label. The following 638 SHOULD result in "Bad EXPLICIT_ROUTE object" errors: 639 - If the first label subobject is not preceded by a subobject 640 containing an IP address, or a interface identifier 641 [MPLS-UNNUM], associated with an output link. 642 - For a label subobject to follow a subobject that has the L-bit 643 set 644 - On unidirectional LSP setup, for there to be a label subobject 645 with the U-bit set 646 - For there to be two label subobjects with the same U-bit values 648 To support the label subobject, a node must check to see if the 649 subobject following it's associate address/interface is a label 650 subobject. If it is, one subobject is examined for unidirectional 651 LSPs and two subobjects for bidirectional LSPs. If the U-bit of the 652 subobject being examined is clear (0), then value of the label is 653 copied into a new Label_Set object. This Label_Set object MUST be 654 included on the corresponding outgoing Path message. 656 If the U-bit of the subobject being examined is set (1), then value 657 of the label is label to be used for upstream traffic associated with 658 the bidirectional LSP. If this label is not acceptable, a "Bad 659 EXPLICIT_ROUTE object" error SHOULD be generated. If the label is 660 acceptable, the label is copied into a new Upstream Label object. 661 This Upstream Label object MUST be included on the corresponding 662 outgoing Path message. 664 After processing, the label subobjects are removed from the ERO. 666 Note an implication of the above procedures is that the label 667 subobject should never be the first subobject in a newly received 668 message. If the label subobject is the the first subobject an a 669 received ERO, then it SHOULD be treated as a "Bad strict node" error. 671 Procedures by which an LSR at the head-end of an LSP obtains the 672 information needed to construct the Label subobject are outside the 673 scope of this document. 675 6. RSVP Message Formats 677 This section presents the RSVP message related formats as modified by 678 this document. Where they differ, formats for unidirectional LSPs 679 are presented separately from bidirectional LSPs. Unmodified formats 680 are not listed. 682 The format of a Path message is as follows: 684 ::= [ ] 685 686 687 [ ] 688 689 [ ... ] 690 [ ] 691 [ ] 692 [ ... ] 693 695 The format of the sender description for unidirectional LSPs is: 697 ::= 698 [ ] 699 [ ] 700 [ ] 702 The format of the sender description for bidirectional LSPs is: 704 ::= 705 [ ] 706 [ ] 707 [ ] 708 710 The format of a Resv message is as follows: 712 ::= [ ] 713 714 715 [ ] [ ] 716 [ ] 717 [ ... ] 718