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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group P. Ashwood-Smih 2 Internet Draft A. Paraschiv 3 Expiration Date: May 2001 Nortel Networks 5 November 2000 7 MPLS LDP Query Message Description 9 draft-ietf-mpls-lsp-query-01.txt 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. Internet-Drafts are working 15 documents of the Internet Engineering Task Force (IETF), its areas, 16 and its working groups. Note that other groups may also distribute 17 working documents as Internet-Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 Abstract 32 This document describes the encoding and procedures for three new LDP 33 messages, the Query Message and Query-Reply Message and Partial 34 Query-Reply Message (the last one is almost identical to the Query- 35 Reply message; therefore all references to the Query-Reply messages 36 imply the Partial Query-Reply messages as well, unless otherwise 37 specified). An LER sends a Query message when it needs to find out 38 information about an LSP. The Query message is sent for an 39 established LSP. The Query message can be used for LDP LSPs as well 40 as for CR-LSPs. The queried data is encoded into the Query-Reply 41 messages. 43 Contents 45 1 Introduction ............................................. 3 46 2 Overview ................................................. 3 47 2.1 LDP Overview ............................................. 4 48 2.2 CR-LDP Overview .......................................... 4 49 3 LDP Message Structure Overview ........................... 4 50 4 Behavior of LSRs with constraints in handling the query messages 5 51 4.1 LSR does not support the query messages .................. 6 52 4.2 LSR cannot share any information ......................... 6 53 4.3 LSR cannot share some of the queried information ........ 6 54 4.4 LSR can share the queried information ................... 7 55 5 Query Message ............................................ 7 56 5.1 Query Message encoding ................................ 8 57 5.2 Query Message Procedures ................................. 9 58 6 Reply Messages .......................................... 10 59 6.1 Query-Reply Message encoding .......................... 10 60 6.2 Query-Reply Message Procedures ........................... 12 61 6.3 Partial Query-Reply Message encoding .................. 13 62 6.4 Partial Query-Reply Message Procedures ................... 13 63 7 Query TLVs ............................................... 14 64 7.1 Query Label TLV .......................................... 15 65 7.2 Query Merge Flags TLV .................................... 15 66 7.3 Status code summary ..................................... 16 67 8 Acknowledgments .......................................... 16 68 9 References ............................................... 17 69 10 Author's Addresses ....................................... 18 70 Changes from previous version: 72 o Added description for the behavior of an LSR that is configured not 73 to share the queried data. 74 o Added a new type of Query message - Partial Query-Reply message; this 75 new reply is introduced to address cases when the Query message doesn't 76 get a reply back from the egress LER; it is used by the ingress LER to 77 gather information about the LSP, up to the failure node in the path; 78 it is recommended to be used when Query message fails to receive a 79 Query-Reply). 81 1. Introduction 83 The original Multiprotocol Label Switching (MPLS) architecture 84 [MPLS-ARCH] was been defined to support the forwarding of data based 85 on a label. The MPLS architecture does not assume a single label 86 distribution protocol. A number of different label distribution 87 protocols are being standardized. This draft describes the query 88 mechanism for an LSP or CR-LSP. It specifies procedures and encodings 89 for the new messages added for the query mechanism. Extensions to 90 RSVP-TE to provide the same functionality are subject for future 91 study and will be covered in future draft versions. 93 The new LDP messages are: Query Message, Query-Reply Message and 94 Partial Query-Reply Message. The following new TLVs are added to 95 accommodate the encodings for the new query messages: 96 - Query TLV 97 - Query Label TLV 98 - Query Merge Flags TLV 100 LDP uses the TCP transport for session, advertisement and 101 notification messages; i.e., for everything but the UDP-based 102 discovery mechanism. The messages which are added to support the 103 query mechanism are sent over TCP as well. 105 2. Overview 106 2.1. LDP Overview 108 Label Distribution Protocol (LDP) defined in [LDP Specification] 109 contains a set of procedures and messages by which Label Switched 110 Routers (LSR) establish Label Switch Paths (LSP) through a network by 111 mapping network layer routing information directly to data-link layer 112 switched paths. LDP associates a Forwarding Equivalence Class (FEC) 113 with each LSP it creates. The FEC associated with an LSP specifies 114 which packets are mapped to that LSP. 116 2.2. CR-LDP Overview 118 As described in [Constraint-Base LSP Setup using LDP], Constraint 119 Base Routing (CR-LDP) offers the opportunity to extend the 120 information used to setup paths beyond what is available for the 121 routing protocol. 123 3. LDP Message Structure Overview 125 As described in LDP Specification draft, all LDP messages have the 126 following format: 128 0 1 2 3 129 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 1 130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 |U| Message Type | Message Length | 132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 | Message ID | 134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 | | 136 + + 137 | Mandatory Parameters | 138 + + 139 | | 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 | | 142 + + 143 | Optional Parameters | 144 + + 145 | | 146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 U bit 149 Unknown message bit. Upon receipt of an unknown message, if U is 150 clear (=0), a notification is returned to the message originator; 151 if U is set (=1), the unknown message is silently ignored. 153 Message Type 154 Identifies the type of message 156 Message Length 157 Specifies the cumulative length in octets of the Message ID, 158 Mandatory Parameters, and Optional Parameters. 160 Message ID 161 32-bit value used to identify this message. Used by the sending 162 LSR to facilitate identifying notification messages that may apply 163 to this message. An LSR sending a notification message in 164 response to this message should include this Message Id in the 165 Status TLV carried by the notification message; see Section 166 "Notification Message". 168 Mandatory Parameters 169 Variable length set of required message parameters. Some messages 170 have no required parameters. 172 For messages that have required parameters, the required parameters 173 MUST appear in the order specified by the individual message 174 specifications in the sections that follow. 176 Optional Parameters 177 Variable length set of optional message parameters. Many messages 178 have no optional parameters. 180 For messages that have optional parameters, the optional parameters 181 may appear in any order. 183 4. Behavior of LSRs with constraints in handling the query messages 185 Upon receiving a Query message, an LSR has to behave according to its 186 configuration constraints in handling the query messages and 187 returning the queried information. The following cases were 188 identified: 190 - the LSR does not support the code to handle the messages 191 for the query mechanism 192 - the LSR supports the code to handle the messages for the 193 query mechanism, but it is configured not to return any data 194 - the LSR supports the code to handle the messages for the 195 query mechanism, but it is configured not to return part of 196 the queried data 197 - the LSR supports the code to handle the messages for the 198 query mechanism, and it is configured to return all the data 199 which is queried. 201 The draft provides flexibility to handle each of the above cases. 203 4.1. LSR does not support the query messages 205 In this case, the LSR has to behave as if it received an unknown 206 message type. It has therefore to honor the U bit. 208 4.2. LSR cannot share any information 210 In this case, the LSR is able to decode and process the query 211 messages. However, it is configured to hide all the data. It should 212 propagate the message after it encodes a zero-length TLV for its hop 213 in the hop list in the Query message. When Query-Reply message is 214 received from downstream, the LSR is requested to propagate the reply 215 message upstream after it encodes the zero-length tlvs for the 216 queried data. When the ingress receives back the reply, it can 217 identify which TLVs are empty; it can therefore ignore the zero- 218 length TLVs and process the rest of the data. 220 Note: zero-length TLV encoding can be used for all types of queried 221 information except the merge information. The LSR is requested to 222 signal the fact that the merging information is private by encoding a 223 special value in the corresponding merge bits (for more information 224 on the merge flags values please refer to Query Merge Flags TLV 225 section). 227 4.3. LSR cannot share some of the queried information 229 In this case, the LSR is able to decode and process the query 230 messages. It has to propagate the query messages. It has to encode 231 values for the data types that it is willing to return and zero- 232 length TLVs for values for the data that is hidden. 234 Note: zero-length TLV encoding can be used for all types of queried 235 information except the merge information. The LSR is requested to 236 signal the fact that the merging information is private by encoding a 237 special value in the corresponding merge bits (for more information 238 on the merge flags values please refer to Query Merge Flags TLV 239 section). 241 4.4. LSR can share the queried information 243 This is the normal case for an LSR. In this case, the LSR's behavior 244 has to follow the query and replies procedures described in the 245 following sections of the draft. 247 In order to have consistency among data encoded in the query and 248 reply messages, each LSR which can propagate the messages has to 249 encode its information in the query and in the reply messages. 251 The decision that an LSR can share the queried information has to be 252 controlled through configuration flags. This way each node along the 253 path can protect its data if they consider it private. 255 Note: It would be more efficient to control/restrict the private data 256 per MPLS cloud (inter MPLS domain) and not per LSR node (inter and 257 intra MPLS domain). When there are different MPLS clouds which have 258 nodes belonging to different vendors, the control of the private 259 information could be restricted to the boundary nodes. Within an MPLS 260 domain, there should be no restrictions on the queried information. 261 It would be useful to have some knowledge on which are the nodes on 262 the boundaries and have only those hiding the queried data. Because 263 there is no mechanism to identify which are the boundary nodes, this 264 is subject for future study. 266 5. Query Message 268 This sections describes the Query message and its encodings and 269 procedures. This message is meant to be used to gather information 270 about an LSP. It can be sent at any time for an established LSP. 271 The draft currently describes the procedures for the cases when the 272 Query Message is initiated by the ingress LER. Future versions of 273 the draft may add the procedures for the query message when issued 274 from a core LSR or from egress. 276 The Query Message can be used to gather information about: 278 - LSRs which form the LSP 279 - labels along the LSP 280 - information on what LSRs are merging points along the path 281 - unused bandwidth (as described in "Improving Topology Data 282 Base Accuracy with LSP Feedback") 283 - congestion status 284 - round trip delay 285 - anything that is needed in the future and can be computed and 286 encoded in a TLV. 288 The queried information is encoded in the Query-Reply message which 289 is sent back upstream, as a response to the Query message. 291 5.1. Query Message encoding 293 The encoding for the Query message is: 295 0 1 2 3 296 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 1 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 |0| Query (0x0409) | Message Length | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | Message ID | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 | Query Label TLV | 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 | Query TLV | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 306 | Hop Count TLV | 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 308 | Optional Parameters | 309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 Message ID 312 32-bit value used to identify this message. 314 Query Label TLV 315 The label associated to the LSP which is queried. This TLV is a 316 list of Generalized Label TLVs [OPTICAL reference]. The 317 Generalized Label TLV provides a more generic encoding for 318 different types of labels. Most of the time the list has one 319 element; this is the case when the LSP is not tunneled. For 320 tunneled LSPs, the Label TLV has more that one element; it has to 321 behave like a label stack (it contains the previous label and the 322 tunnel's label). See Section Query Label TLV for more information 323 on Label TLV encoding. 325 Query TLV 326 What to query. See Section Query TLV for encoding. 328 Hop Count TLV 329 Specifies the number of LSR hops that can still be traversed 330 before the message is dropped due to loop detection. It is 331 initialized to the max value of 255 (or the configured value, if 332 any). Every LSR that receives the Query Message has to subtract 1 333 from the Hop Count value. The Query message should be dropped if 334 the hop count value becomes zero; a Notification signaling Loop 335 Detection should be sent in reply to the sender of the message. 336 See [LDP Specification] for Hop Count TLV encoding. 338 Optional Parameters 339 This variable length field contains 0 or more parameters, each 340 encoded as a TLV. 342 Optional Parameter Length Value 344 ER TLV var See CR-LDP 346 The ER TLV is a list of hops. It is used when the Query flag Q3 is 347 set. Every LSR should add its IP address. The address to be added 348 should be the outgoing interface address. Addresses are organized as 349 a last-in-fist-out stack (the first address in TLV is considered the 350 top). By carrying this TLV in the Query Message and preserving this 351 order for the hops, we allow the possibility to interwork the Query 352 Message with the RSVP Path message. 354 5.2. Query Message Procedures 356 The LER ingress initiates the Query message. It populates the Query 357 TLV Parameters according to what kind of information it wants to 358 gather. The query for an LSP is done by its label. The only data that 359 the Query Message carries is the list of hops. This way, each node 360 along the path will have a complete route from source to destination. 361 The hop list information is useful for network management. 363 Upon receiving a Query Message, an LSR decodes the label to identify 364 which LSP is queried. If it cannot find the LSP which is using the 365 label, it sends back a Notification message with "No Lsp to query" 366 status. Otherwise, it checks which is the out label which is bound to 367 the queried in-label and which is the downstream LSR peer. It 368 replaces the in-label from Query Label TLV with the out-label used by 369 the LSP. It then passes the Query message to the downstream peer. 370 When the Query message gets to a tunnel, it has to be able to handle 371 both the previous label and the tunnel's label. The Query Label TLV 372 behaves like a label stack. The previous label is pushed and the 373 tunnel label is used. At the end of the tunnel, we need to pop the 374 stack and start substituting the lower level labels. 376 Upon receiving the Query message, the egress node has to reply with a 377 Query Reply Message. The Query-Reply Message contains the Query TLV 378 which was received in the Query Message. The Query TLV tells the LSRs 379 along the path which information is being queried and allows 380 intermediate LSRs to piggy back their own queried information on the 381 Query reply message. 383 6. Reply Messages 385 These messages are propagated upstream. There are situations in 386 which the Query message does not reach the end point of the queried 387 LSP. In these scenarios it would be useful if the ingress LSR 388 gathered at least some information about the LSRs which are along the 389 path, up to the one that failed. The Partial Query-Reply message 390 provides this mechanism. It is recommended to use the Partial Query- 391 Reply messages when a Query message fails. There are two types of 392 reply messages: 394 - Query-Reply message (final reply) 395 - Partial Query-Reply message. 397 Both of the reply messages are described in the following sections. 399 6.1. Query-Reply Message encoding 401 This message is generated by the end point of the LSP. It is 402 propagated upstream, by each LSR along the path. 404 The encoding for the Query-Reply message is: 406 0 1 2 3 407 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 1 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 |0| Query-Reply (0x0410) | Message Length | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Message ID | 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 | Query TLV | 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 | MessageId TLV | 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | Optional Parameters | 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 Message ID 421 32-bit value used to identify this message. 423 Query TLV 424 What is to be queried. See Section Query TLV for encoding. 426 Message Id TLV 427 The value of this parameter is the message id of the corresponding 428 Query message. 430 Optional Parameters 431 This variable length field contains 0 or more parameters, each 432 encoded as a TLV. The optional parameters are: 434 Optional Parameter Length Value 436 ER TLV var See CR-LDP 437 Query Label TLV var See Query Label TLV section 438 IPV4/6 specified link feedback TLV See Improving Topology ... 439 Query Merge Flags TLV var See Query Merge Flags TLV 440 section 442 For simplicity we reuse here TLV types defined for CR-LDP and LDP. 443 They are: 445 - IPV4/6 specified link feedback TLV 446 - ER TLV 447 - Generalized Label TLV (used in the Query Label TLV encoding) 448 - Hop Count TLV. 450 The IPV4/6 specified link feedback TLV is used when the Q1 flag from 451 the Query TLV is set. It is used to encode the bandwidth information. 452 For more information on query flags, Q1, ... Q6, refer to Query TLV 453 section. 455 The ER TLV is a list of hops. It is used when the Query flag Q3 is 456 set. Every LSR should add its IP address. The address to be added 457 should be the outgoing interface address. Addresses are organized as 458 a last-in-fist-out stack (the first address in TLV is considered the 459 top). 461 The Query Label TLV is a list of labels. It is used when the Query 462 flag Q2 is set. It is populated with the labels used for the path 463 which is queried. For tunneled LSPs, the Query Label TLV represents a 464 list of labels associated to the lowest level tunnel. 466 If Q3 and Q2 flags are set, the labels should be encoded in the same 467 order as the hops. 469 Query Merge Flags TLV is a list of pairs of bits. It has variable 470 length and every two bits in the mask will correspond to an LSR along 471 the path. Its length is rounded up to the next byte. If Q6 is set, 472 every LSP along the path will have to set its corresponding bits in 473 the mask. The bits have to be set in the same order as the labels and 474 hops. Usually, Q6 is set when Q2 set and/or Q3 set. 476 For more information for the TLV encodings of the TLVs which are 477 reused, please see CR-LDP draft, LDP draft and IMPROVING TOPOLOGY 478 DATA BASE ACCURACY WITH LSP FEEDBACK VIA CR_LDP draft. 480 6.2. Query-Reply Message Procedures 482 A Query-Reply message is initiated by an egress node which receives a 483 Query message, if the egress is able to identify the queried LSP. If 484 not, the egress replies with a Notification message with "No Lsp to 485 query" status. 487 Upon receiving the Query message, the egress node has to reply with a 488 Query Reply message. The egress node has to encode into the Query- 489 Reply message a MessageId Tlv. The mapping between a Query and a 490 Query-Reply Message is done based on the message id. Besides the 491 MessageId Tlv, the egress has to encode the information that was 492 queried (bandwidth, path, etc). 494 After the encoding is done, the query reply message is sent back, on 495 the reversed path, towards the ingress. Every LSR across the LSP has 496 to encode its information according to what query flags are set. 498 6.3. Partial Query-Reply Message encoding 500 The Partial Query-Reply message is initiated by tandem LSRs along the 501 queried path. The message is generated only if the following rules 502 apply: 503 - if the Query message asked for partial 504 replies (the Query message signals this request 505 through Q8 bit) 506 - if the tandem LSR is configured to provide partial replies. 508 The encoding for the Partial Query-Reply message is identical to the 509 Query-Reply, except the message type. For more details on the 510 encoding please refer to the Query-Reply encoding. 512 0 1 2 3 513 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 1 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 |0|Partial Query-Reply (0x0411) | Message Length | 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | Message ID | 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | Query TLV | 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 | MessageId TLV | 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 523 | Optional Parameters | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 6.4. Partial Query-Reply Message Procedures 528 The procedures are similar to the Query-Reply's procedures. Upon 529 receiving a Query message, a tandem LSR will check the flag from the 530 Query message (Q8) which signals if the partial replies are requested 531 by the ingress node. If the flag is set, the LSR has to check next if 532 it is configured to fulfill this request. If the LSR supports partial 533 replies, it has to create a Partial Query-Reply and encode the 534 queried data and send it upstream like any Query-Reply messages. It 535 has then to process the Query message according to the Query message 536 procedures. When an LSR receives a Partial Query-Reply from upstream, 537 it should encode its information according to what is queried and 538 propagate the message. It is recommended to use the Partial Query 539 mechanism when the Query message fails (when the ingress LER does not 540 receive a Query-Reply message in response to a Query message). 542 7. Query TLVs 544 The Query TLV is used to specify the information being queried. The 545 Query TLV travels in the Query message to the egress node, where it 546 is copied into a reverse flowing Query-Reply messages and used by the 547 egress and intermediate LSRs to know what information is being 548 queried. 550 The format for the Query TLV is: 552 0 1 2 3 553 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 1 554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 555 |0|0| Query TLV (0x0840) | Length | 556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 557 | Query Flags | Reserved | 558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 Query Flags can be set according to what the Query is used for. 562 +--+--+--+--+--+--+--+--+ 563 |Q8|Re|Q6|Q5|Q4|Q3|Q2|Q1| 564 +--+--+--+--+--+--+--+--+ 566 They can be: 567 - Q1 : query the bandwidth; if set, the LSR that 568 receives the Query message has to encode the bandwidth 569 that is available on the link (unused bandwidth); 570 - Q2 : query the labels which are associated to each hop in the 571 path; 572 - Q3 : query the LSRs which form the LSP which is queried; 573 if set, the LSR that received the Query-Reply message 574 has to encode the current hop in the ER-TLV 575 - Q4 : reserved for congestion status; < format - TBD > 576 - Q5 : query the round trip delay; if set, the LSR should fill in 577 the link delay information if available; < format - TBD > 578 - Q6 : query which LSPs along the path are merging points; if set, 579 the LSR that receives the Query message has to encode 580 if it is a merging point; the encoding is done in the 581 Query Merge flags TLV. 583 - Q8 : if set, the ingress requests partial query-replies; 584 7.1. Query Label TLV 586 The Query Label TLV is used to encode the labels used along the path 587 which is queried. Note: Query Label TLV is used in both Query and 588 Query Reply. It is a required parameter in the Query message and it 589 is an optional parameter in Query Reply message. When being used in 590 the Query message, it carries the label or stack of labels which are 591 being followed and queried. When being used in the Query Reply 592 message, it carries the list of labels which make up the queried 593 path. 595 The format for the Query Label TLV is: 597 0 1 2 3 598 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 1 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 |0|0| Query Label TLV (0x0841)| Length | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 | Generalized Label TLV 1 | 603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 604 ~ ~ 605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 606 | Generalized Label TLV n | 607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 Generalized Label TLV is used to encode labels along the path. Please 610 refer to [OPTICAL reference] for more information on the Generalized 611 Label TLV encoding. If the Q2 flag is set, every LSR has to encode 612 the out-label corresponding to the queried LSP. In the Query Label 613 TLV, labels are organized as a last-in-fist-out stack (the first 614 label in TLV is considered the top). They should be encoded in the 615 same order as the hops and the merge flags. 617 7.2. Query Merge Flags TLV 619 The Query Merge Flags TLV is used to encode the information about 620 which LSRs along the path the queried LSP is being merged into. 622 The format for the Query Merge Flags TLV is: 624 0 1 2 3 625 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 1 626 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 |0|0| Merge Flags TLV (0x0842) | Length | 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 | Number of merge flags | 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 | Merge flags | | | ~ 632 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 ~ ~ 634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 | | 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 The Query Merge Flags TLV has 4 bytes field to store the number of 639 merge flags. This number is equal to the number of LSRs which are 640 traversed by the Query-Reply Message. Each 2 bits in the Merge flags 641 field represent the merge information for an LSR. The bits are set to 642 01 if the LSR does not do merge for the queried LSP and are set to 10 643 otherwise. If the LSR want to hide the merging information, it has to 644 set the merging flags to 00. The length of the encoding is rounded 645 up to the next byte. Every LSR which is asked to encode the merging 646 info into this TLV has to update the Number of merge flags and to set 647 its corresponding bits accordingly. 649 7.3. Status code summary 651 Status Code E Status Data Section Title 653 No Lsp to query 1 0x0000001a "Query Message Procedures..." 655 8. Acknowledgments 657 The authors would like to acknowledge the careful review and comments 658 of Jean-Pierre Coupal, Steve Hamilton, Don Fedyk and Gregory Wright. 660 9. References 662 [CR-LDP] Jamoussi et al., "Constraint-Based LSP Setup using LDP", 663 [LDP] Andersson et al., "LDP Specification", draft-ietf-mpls-ldp-07.txt, 664 May 2000. 666 [RSVP-RR] Berger L., Gan D., Swallow G., Pan P., Tommasi F., Molendini 667 S., "RSVP Refresh Overhead Reduction Extensions", draft-ietf-rsvp- 668 refresh-reduct-04.txt. 670 [CR-LDP] Peter Ashwood-Smith et al., "Improving Topology Data Base 671 Accuracy with LSP Feedback", draft-ietf-mpls-te-feed-01.txt 673 Ashwood-Smith P., Berger L., "Generalized MPLS-Signaling Functional 674 Description" draft-ashwood-generalized-mpls-signaling-00.txt 675 10. Author's Addresses 677 Peter Ashwood-Smith Antonela Paraschiv 678 Nortel Networks Corp. Nortel Networks Corp. 679 P.O. 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