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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: 'MPLS-ARCH' on line 91 -- Looks like a reference, but probably isn't: 'RFC2119' on line 122 == Outdated reference: A later version (-06) exists of draft-ietf-mpls-te-feed-03 == Outdated reference: A later version (-09) exists of draft-ietf-mpls-generalized-signaling-07 ** Obsolete normative reference: RFC 3036 (ref. '4') (Obsoleted by RFC 5036) Summary: 2 errors (**), 0 flaws (~~), 8 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Ashwood-Smith 3 Internet Draft A. Paraschiv 4 Expiration Date: January 2004 D. Allan 5 Nortel Networks 7 June 2003 9 Multi Protocol Label Switching Label Distribution Protocol 10 Query Message Description 12 draft-ietf-mpls-lsp-query-08.txt 14 Status of this Memo 16 This document is an Internet-Draft and is in full conformance with 17 all provisions of Section 10 of RFC2026. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six 25 months and may be updated, replaced, or obsoleted by other documents 26 at any time. It is inappropriate to use Internet-Drafts as 27 reference material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 Abstract 36 This document describes the encoding and procedures for three new 37 Label Distribution Protocol (LDP) messages: Query Message, Query- 38 Reply Message and Partial Query-Reply Message. A Label Edge Router 39 (LER) sends a Query message when it needs to find out information 40 about an established Label Switched Path (LSP). The Query message 41 can be used for LDP LSPs as well as for Constraint-Based Label 42 Switched Paths (CR-LSPs). The queried data is encoded into the 43 Query-Reply messages. 45 Contents 47 1. Introduction ........................................3 48 2. Specification........................................3 49 3. Overview.............................................3 50 3.1 LDP Overview .......................................3 51 3.2 CR-LDP Overview.....................................4 52 4. LDP Message Structure Overview.......................4 53 5. LSRs with constraints in handling the query messages.5 54 5.1 LSR does not support the query messages.............6 55 5.2 LSR cannot share any information....................6 56 5.3 LSR cannot share some of the queried information....6 57 5.4 LSR can share the queried information...............6 58 6. Query Message........................................7 59 6.1 Query Message encoding .............................7 60 6.2 Query Message Procedures............................9 61 7. Reply Messages.......................................10 62 7.1 Query-Reply Message encoding .......................10 63 7.2 Query-Reply Message Procedures......................12 64 7.3 Partial Query-Reply Message encoding................12 65 7.4 Partial Query-Reply Message Procedures .............13 66 8. Query TLVs...........................................13 67 8.1 Query Label TLV.....................................14 68 8.2 Query Merge Flags TLV...............................15 69 8.3 Query Payload TLV ..................................16 70 8.4 Status code summary.................................16 71 9. Security Considerations..............................17 72 10. IANA Considerations..................................17 73 10.1 Message Type Space Extension......................17 74 10.2 TLV Type Name Space Extension ....................17 75 10.3 Status Code Space Extension.......................18 76 11. Acknowledgments......................................18 77 12. Normative References.................................18 78 13. Author's Addresses...................................18 79 Changes from previous version: 81 o Additions to support ECMP 82 o Editorial changes 83 o Elaboration on security considerations 84 o Clarification to message fragmenting issues. 86 [Editor's note: This section has to be removed prior to publication] 88 1. Introduction 90 The original Multiprotocol Label Switching (MPLS) architecture 91 [MPLS-ARCH] was been defined to support the forwarding of data based 92 on a label. The MPLS architecture does not assume a single label 93 distribution protocol. A number of different label distribution 94 protocols are being standardized. This memo describes the query 95 mechanism for a Label Switched Path (LSP) or Constraint Based LSP 96 (CR-LSP). It specifies procedures and encodings for the new messages 97 added for the query mechanism. 99 The new LDP messages are: Query Message, Query-Reply Message and 100 Partial Query-Reply Message. The Partial Query Reply is almost 101 Identical to the Query Reply message; therefore all references to 102 the Query Reply message imply the Partial Query Reply Message as 103 well unless explicitly noted. 105 The following new TLVs are added to accommodate the encodings for 106 the new query messages: 107 - Query TLV 108 - Query Label TLV 109 - Query Merge Flags TLV 110 - Query Payload TLV 112 LDP uses the TCP transport for session, advertisement and 113 notification messages; i.e., for everything but the UDP-based 114 discovery mechanism. The messages which are added to support the 115 query mechanism are sent over TCP as well. 117 2. Specification 119 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 120 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 121 document are to be interpreted as described in [RFC2119]. 123 3. Overview 125 3.1 LDP Overview 126 Label Distribution Protocol (LDP) defined in [4] contains a set of 127 procedures and messages by which Label Switched Routers (LSR) 128 establish Label Switch Paths (LSP) through a network by mapping 129 network layer routing information directly to data-link layer 130 switched paths. LDP associates a Forwarding Equivalence Class (FEC) 131 with each LSP it creates. The FEC associated with an LSP specifies 132 which packets are mapped to that LSP. 134 3.2 CR-LDP Overview 136 As described in CR-LDP [1], Constraint Base Routing offers the 137 opportunity to extend the information used to setup paths beyond 138 what is available from the routing protocol. For instance, an LSP 139 can be setup based on explicit route constraints, QoS constraints, 140 and other constraints. 142 4. LDP Message Structure Overview 144 The LDP message format is specified in the LDP Specification [4]. 145 All LDP messages have the following format: 147 0 1 2 3 148 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 1 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 |U| Message Type | Message Length | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Message ID | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | | 155 + + 156 | Mandatory Parameters | 157 + + 158 | | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | | 161 + + 162 | Optional Parameters | 163 + + 164 | | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 U bit 168 Unknown message bit. Upon receipt of an unknown message, if U 169 is clear (=0), a notification is returned to the message 170 originator; if U is set (=1), the unknown message is silently 171 ignored. 173 Message Type 174 Identifies the type of message 176 Message Length 177 Specifies the cumulative length in octets of the Message ID, 178 Mandatory Parameters, and Optional Parameters. 180 Message ID 181 32-bit value used to identify this message. It is used by the 182 sending LSR to facilitate identifying notification messages 183 that may apply to this message. An LSR sending a notification 184 message in response to this message should include this 185 MessageId in the Status TLV carried by the notification 186 message. 188 Mandatory Parameters 189 Variable length set of required message parameters. Some 190 messages have no required parameters. 192 For messages that have required parameters, the required parameters 193 must appear in the order specified by the individual message 194 specifications in the sections that follow. 196 Optional Parameters 197 Variable length set of optional message parameters. Many messages 198 have no optional parameters. 200 For messages that have optional parameters, the optional parameters 201 may appear in any order. 203 5. LSRs with constraints in handling the query messages 205 Upon receiving a Query message, an LSR has to behave according to 206 its configuration constraints in handling the query messages and 207 returning the queried information. The following cases were 208 identified: 209 - The LSR does not support the code to handle the messages 210 for the query mechanism 211 - The LSR supports the code to handle the messages for the 212 query mechanism, but it is configured not to return any 213 data 214 - The LSR supports the code to handle the messages for the 215 query mechanism, but it is configured not to return part of 216 the queried data 217 - The LSR supports the code to handle the messages for the 218 query mechanism, and it is configured to return all the 219 data which is queried. 221 This memo provides flexibility to handle each of the above cases. 223 5.1 LSR does not support the query messages 225 In this case, the LSR has to behave as if it received an unknown 226 message type. It therefore honors the U bit. 228 5.2 LSR cannot share any information 230 In this case, the LSR is able to decode and process the query 231 messages. However, it is configured to hide all the data. It should 232 propagate the message after it encodes a zero-length TLV for its hop 233 in the hop list in the Query message. When Query-Reply message is 234 received from downstream, the LSR is requested to propagate the 235 reply message upstream after it encodes the zero-length TLVs for the 236 queried data. When the ingress receives back the reply, it can 237 identify which TLVs are empty; it can therefore ignore the zero- 238 length TLVs and process the rest of the data. 240 Note: zero-length TLV encoding can be used for all types of queried 241 information except the merge information. The LSR is requested to 242 signal the fact that the merging information is private by encoding 243 a special value in the corresponding merge bits (for more 244 information on the merge flags values please refer to Section 7.2 of 245 this memo - Query Merge Flags TLV). 247 5.3 LSR cannot share some of the queried information 249 In this case, the LSR is able to decode and process the query 250 messages. It has to propagate the query messages. It has to encode 251 values for the data types that it is willing to return and zero- 252 length TLVs for values for the data that is hidden. 254 Note: zero-length TLV encoding can be used for all types of queried 255 information except the merge information. The LSR is requested to 256 signal the fact that the merging information is private by encoding 257 a special value in the corresponding merge bits (for more 258 information on the merge flags values please refer to Section 7.2 of 259 this memo - Query Merge Flags TLV). 261 5.4 LSR can share the queried information 263 In this case, the LSR's behavior has to follow the query and replies 264 procedures described in the following sections of this memo. 266 In order to have consistency among data encoded in the query and 267 reply messages, each LSR which can propagate the messages has to 268 encode its information in the query and in the reply messages. 270 The decision that an LSR can share the queried information has to be 271 controlled through configuration flags. This way each node along the 272 path can protect its data if they consider it private. 274 Note: It would be more efficient to control/restrict the private 275 data per MPLS cloud (inter MPLS domain) and not per LSR node (inter 276 and intra MPLS domain). When there are different MPLS clouds which 277 have nodes belonging to different vendors, the control of the 278 private information could be restricted to the boundary nodes. 279 Within an MPLS domain, there should be no restrictions on the 280 queried information. It would be useful to have some knowledge on 281 which are the nodes on the boundaries and have only those hiding the 282 queried data. Because there is no mechanism to identify which are 283 the boundary nodes, this is subject for future study. 285 6. Query Message 287 This section describes the Query message and its encodings and 288 procedures. This message is meant to be used to gather information 289 about an LSP. It can be sent at any time for an established LSP. 290 This memo currently describes the procedures for the cases when the 291 Query Message is initiated by the ingress LER. Additional procedures 292 may be added in the future for the query message when issued from an 293 LSR or from egress. 295 The Query Message can be used to gather information about: 296 - LSRs which form the LSP 297 - Labels along the LSP 298 - Information on what LSRs are merging points along the path 299 - Unused bandwidth (as described in "Improving Topology Data 300 Base Accuracy with LSP Feedback" [2]) 301 - What path any specific payload may follow in the presence 302 of load spreading mechanisms such as ECMP 303 - Anything that is needed in the future and can be computed 304 and encoded in a TLV. 306 It should be noted that useful information can still be extracted 307 from partial responses due constraints on handling messages placed 308 on some LSRs along the LSP. In the fault diagnosis scenario 309 (particularly in the presence of ECMP), those LSRs that at a minimum 310 return their own LSR ID facilitate diagnosis when combined with data 311 plane tracing tools as those LSRs can act as segmentation boundaries 312 for fault isolation. 314 The queried information is encoded in the Query-Reply message which 315 is sent back upstream, as a response to the Query message. 317 6.1 Query Message encoding 319 The encoding for the Query message is: 321 0 1 2 3 322 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 1 324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 |0| Query type TBD IANA | Message Length | 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 | Message ID | 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 | Query Label TLV | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | Query TLV | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Hop Count TLV | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | Optional Parameters | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 338 Message ID 339 32-bit value used to identify this message. 341 Query Label TLV 342 The label associated to the LSP which is queried. This TLV is a 343 list of Generalized Label TLVs [3]. The Generalized Label TLV 344 provides a more generic encoding for different types of labels. 345 Most of the time the list has one element; this is the case when 346 the LSP is not tunneled. For tunneled LSPs, the Label TLV has 347 more that one element; it has to behave like a label stack (it 348 contains the previous label and the tunnel's label). See Section 349 7.1 of this memo - Query Label TLV - for more information on 350 Label TLV encoding. 352 Query TLV 353 What to query. See Section 7 of this memo - Query TLV - for 354 encoding. 356 Hop Count TLV 357 Specifies the number of LSR hops that can still be traversed 358 before the message is dropped due to loop detection. It is 359 initialized to the max default value of 255 (or the configured 360 value, if any). Every LSR that receives the Query Message has to 361 subtract 1 from the Hop Count value. The Query message should 362 be dropped if the hop count value becomes zero; a Notification 363 signaling Loop Detection should be sent in reply to the sender 364 of the message. See [4] for Hop Count TLV encoding. 366 Optional Parameters 367 This variable length field contains 0 or more parameters, each 368 encoded as a TLV. 370 Optional Parameter Length Value 372 ER TLV var See [1] 373 LSPID TLV var See [1] 374 FEC TLV var See [4] 375 Query Payload TLV var See below 377 The ER TLV is a list of hops. It is used when the Query flag Q3 is 378 set. Every LSR should add its IP address. The address to be added 379 should be the outgoing interface address. Addresses are organized as 380 a last-in-first-out stack (the first address in TLV is considered 381 the top). By carrying this TLV in the Query Message and preserving 382 this order for the hops, we allow the possibility to interwork the 383 Query Message with the RSVP Path message. 385 FEC TLV is used when penultimate hop popping (PHP) is in use, for 386 LDP. 388 LSPID TLV is used when PHP is in use, for CR-LDP. 390 Query Payload TLV is used where ECMP is deployed in order to qualify 391 the specific LSP hops chosen by intermediate LSRs. 393 For more details on the FEC, LSPID, or Query Payload TLVs usage, 394 please refer to the Query Message Procedures below. 396 6.2 Query Message Procedures 398 The LER ingress initiates the Query message. It populates the Query 399 TLV Parameters according to what kind of information it wants to 400 gather. The query for an LSP is done by its label. The only data 401 that the Query Message could carry is the list of hops. This way, 402 each node along the path can have a complete route from source to 403 destination. This is useful for network management. Please note 404 that this parameter is optional. If the Query message does not 405 contain the ER TLV, it should be propagated by LSRs along the path 406 without the ER TLV. 408 Upon receiving a Query Message, an LSR decodes the label to identify 409 which LSP is queried. If it cannot find the LSP which is using the 410 label, it sends back a Notification message with "No LSP to query" 411 status. Otherwise, it checks which is the out label which is bound 412 to the queried in-label and which is the downstream LSR peer. It 413 replaces the in-label from Query Label TLV with the out-label used 414 by the LSP. It then passes the Query message to the downstream peer. 416 Where there is more than one valid downstream peer, AND the Payload 417 Query TLV is present, the LSR may use the Payload Query TLV to 418 select the appropriate downstream LSP peer using the same algorithms 419 that it would use if the payload was carried in the LSP data plane. 420 If the Payload Query TLV is not present but the ECMP implementation 421 requires the payload information for downstream path selection, it 422 sends back a Notification message with "Payload Query TLV Required" 423 status. 425 When the Query message gets to a tunnel, it has to be able to handle 426 both the previous label and the tunnel's label. The Query Label TLV 427 behaves like a label stack. The previous label is pushed and the 428 tunnel label is used. At the end of the tunnel, we need to pop the 429 stack and start substituting the lower level labels. 431 Upon receiving the Query message, the egress node has to reply with 432 a Query Reply Message. The Query-Reply Message contains the Query 433 TLV which was received in the Query Message. The Query TLV tells the 434 LSRs along the path which information is being queried and allows 435 intermediate LSRs to piggy back their own queried information on the 436 Query reply message. 438 The initiator of a Query reply might not receive a response back. In 439 this case, it is the initiator's responsibility to decide if and 440 when to retry. 442 If PHP is in use, the Query Message sent from the PHP to the 443 destination node needs to carry the FEC (for LDP) or LSPID (for CR- 444 LDP). This information is required because the label between the PHP 445 and the destination is a special label and the destination cannot 446 uniquely identify the queried LSP just by using the label value. If 447 the PHP does not encode the FEC or the LSPID, the destination node 448 should reply with a notification message with "Ambiguous label 449 value". 451 7. Reply Messages 453 These messages are propagated upstream. There are two types of 454 reply messages: 456 - Query-Reply message (final reply) 457 - Partial Query-Reply message. 459 The Reply messages carry the queried information upstream. A Query- 460 Reply message is sent in response to a Query message. The ingress 461 which initiated the Query message is interested to gather the 462 information from all the nodes along the queried LSP. However, 463 there are situations in which the Query message does not reach the 464 end point of the queried LSP. In these scenarios it would be useful 465 if the ingress LSR gathered at least some information about the LSRs 466 which are along the path, up to the one that failed. The Partial 467 Query-Reply message provides this mechanism. It is recommended to 468 use the Partial Query-Reply messages when a Query message fails. 470 Both reply messages are described in the following sections. 472 7.1 Query-Reply Message encoding 474 This message is generated by the end point of the LSP. It is 475 propagated upstream, by each LSR along the path. 477 The encoding for the Query-Reply message is: 479 0 1 2 3 480 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 1 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 |0| Query-Reply Type TBD IANA | Message Length | 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | Message ID | 485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 | Query TLV | 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 488 | MessageId TLV | 489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 490 | Optional Parameters | 491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 Message ID 494 32-bit value used to identify this message. 496 Query TLV 497 What is to be queried. See Section 7 of this memo - Query TLV - 498 for encoding. 500 MessageId TLV 501 The value of this parameter is the message id of the 502 corresponding Query message. 504 Optional Parameters 505 This variable length field contains 0 or more parameters, each 506 encoded as a TLV. The optional parameters are: 508 Optional Parameter Length Value 509 ------------------ ------ ----- 510 ER TLV var See [1] 512 Query Label TLV var See Query Label TLV 513 section 514 IPV4/6 specified link feedback TLV var See [2] 516 Query Merge Flags TLV var See Query Merge Flags 517 TLV section 519 The TLV types are defined in CR-LDP [1] and LDP [4]. They are: 521 - IPV4/6 specified link feedback TLV 522 - ER TLV 523 - Generalized Label TLV (used in the Query Label TLV 524 encoding) 525 - Hop Count TLV. 527 The IPV4/6 specified link feedback TLV is used when the Q1 flag from 528 the Query TLV is set. It is used to encode the bandwidth 529 information. For more information on query flags, Q1, Q2, Q3 and Q4, 530 refer to Query TLV section. 532 The ER TLV is a list of hops. It is used when the Query flag Q3 is 533 set. Every LSR should add its IP address. The address to be added 534 should be the outgoing interface address. Addresses are organized as 535 a last-in-first-out stack (the first address in TLV is considered 536 the top). 538 The Query Label TLV is a list of labels. It is used when the Query 539 flag Q2 is set. It is populated with the labels used for the path 540 which is queried. For tunneled LSPs, the Query Label TLV represents 541 a list of labels associated to the lowest level tunnel. 543 If Q3 and Q2 flags are set, the labels should be encoded in the same 544 order as the hops. 546 Query Merge Flags TLV is a list of pairs of bits. It has variable 547 length and every two bits in the mask will correspond to an LSR 548 along the path. Its length is rounded up to the next byte. If Q4 is 549 set, every LSP along the path will have to set its corresponding 550 bits in the mask. The bits have to be set in the same order as the 551 labels and hops. Usually, Q4 is set when Q2 set and/or Q3 set. 553 For more information for the TLV encodings of the TLVs which are 554 used, please see [1], [4] and [2]. 556 7.2 Query-Reply Message Procedures 558 A Query-Reply message is initiated by an egress node which receives 559 a Query message, if the egress is able to identify the queried LSP. 560 If not, the egress replies with a Notification message with "No LSP 561 to query" status. 563 Upon receiving the Query message, the egress node has to reply with 564 a Query Reply message. The egress node has to encode into the Query- 565 Reply message a MessageId TLV. The mapping between a Query and a 566 Query-Reply Message is done based on the message id. Besides the 567 MessageId TLV, the egress has to encode the information that was 568 queried (bandwidth, path, etc). 570 After the encoding is done, the query reply message is sent back, on 571 the reversed path, towards the ingress. Every LSR across the LSP has 572 to encode its information according to what query flags are set. 574 7.3 Partial Query-Reply Message encoding 575 The Partial Query-Reply message is initiated by LSRs along the 576 queried path. The message is generated only if the following rules 577 apply: 578 - if the Query message asked for partial 579 replies (the Query message signals this request 580 through Q8 bit) 581 - if the LSR is configured to provide partial replies. 583 The encoding for the Partial Query-Reply message is identical to the 584 Query-Reply, except the message type. For more details on the 585 encoding please refer to the Query-Reply encoding. 587 0 1 2 3 588 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 1 589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 |0|Partial Query-Reply TBD IANA | Message Length | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Message ID | 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Query TLV | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | MessageId TLV | 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | Optional Parameters | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 7.4 Partial Query-Reply Message Procedures 603 The procedures are similar to the Query-Reply's procedures. Upon 604 receiving a Query message, an LSR will check the flag from the Query 605 message (Q8) which signals if the partial replies are requested by 606 the ingress node. If the flag is set, the LSR has to check next if 607 it is configured to fulfill this request. If the LSR supports 608 partial replies, it has to create a Partial Query-Reply and encode 609 the queried data and send it upstream like any Query-Reply messages. 610 It has then to process the Query message according to the Query 611 message procedures. When an LSR receives a Partial Query-Reply from 612 upstream, it should encode its information according to what is 613 queried and propagate the message. It is recommended to use the 614 Partial Query mechanism when the Query message fails (when the 615 ingress LER does not receive a Query-Reply message in response to a 616 Query message). 618 8. Query TLVs 620 The Query TLV is used to specify the information being queried. The 621 Query TLV travels in the Query message to the egress node, where it 622 is copied into a reverse flowing Query-Reply messages and used by 623 the egress and intermediate LSRs to know what information is being 624 queried. 626 The format for the Query TLV is: 628 0 1 2 3 629 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 1 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 |0|0| Query TLV Type TBD IANA | Length | 632 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 | Query Flags | Reserved | 634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 Query Flags can be set according to what the Query is used for. 637 A query flag is set when it is 1. 639 +--+--+--+--+--+--+--+--+ 640 |Q8|Reserved|Q4|Q3|Q2|Q1| 641 +--+--+--+--+--+--+--+--+ 643 They can be: 645 - Q1 : query the bandwidth; if set, the LSR that 646 receives the Query message has to encode the bandwidth 647 that is available on the link (unused bandwidth); 648 - Q2 : query the labels which are associated to each hop in the 649 path; 650 - Q3 : query the LSRs which form the LSP which is queried; 651 if set, the LSR that received the Query-Reply message 652 has to encode the current hop in the ER-TLV 653 - Q4 : query which LSPs along the path are merging points; 654 if set, the LSR that receives the Query message has 655 to encode if it is a merging point; the encoding is 656 done in the Query Merge flags TLV. 657 - Q8 : if set, the ingress requests partial query-replies; 658 each LSR along the path is signaled to send a Partial 659 Query Reply. 661 The reserved bits need to be set to zero on transmission and must be 662 ignored on receipt. They might be used in the future to signal other 663 types of queried information. The Query Flags can only be defined by 664 updating this memo. 666 8.1 Query Label TLV 668 The Query Label TLV is used to encode the labels used along the path 669 which is queried. 671 Note: Query Label TLV is used in both Query and Query Reply. It is a 672 required parameter in the Query message and it is an optional 673 parameter in Query Reply message. When being used in the Query 674 message, it carries the label or stack of labels which are being 675 followed and queried. When being used in the Query Reply message, it 676 carries the list of labels which make up the queried path. 678 The format for the Query Label TLV is: 680 0 1 2 3 681 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 1 682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 |0|0| Query Label TLV TBD IANA | Length | 684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 685 | Generalized Label TLV 1 | 686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 ~ ~ 688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 | Generalized Label TLV n | 690 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 692 Generalized Label TLV is used to encode labels along the path. 693 Please refer to [3] for more information on the Generalized Label 694 TLV encoding. If the Q2 flag is set, every LSR has to encode the 695 out-label corresponding to the queried LSP. In the Query Label TLV, 696 labels are organized as a last-in-first-out stack (the first label 697 in TLV is considered the top). They should be encoded in the same 698 order as the hops and the merge flags. 700 8.2 Query Merge Flags TLV 702 The Query Merge Flags TLV is used to encode the information about 703 which LSRs along the path the queried LSP is being merged into. 705 The format for the Query Merge Flags TLV is: 707 0 1 2 3 708 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 1 709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 |0|0| Merge Flags TLV TBD IANA | Length | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | Number of merge flags | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | Merge flags ~ 715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 716 ~ ~ 717 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 718 | | 719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 721 The Query Merge Flags TLV has 4 bytes field to store the number of 722 merge flags. This number is equal to the number of LSRs which are 723 traversed by the Query-Reply Message. The Merge flags field 724 contains the merge information. It is a variable length field which 725 is rounded up to the next byte. Each pair of bits in the Merge flags 726 field carries the merge information for one LSR. The valid values 727 for the merge bits for an LSR are: 729 01 - LSR does not do merge for the queried LSP 730 10 - LSR does merge for the queried LSP 731 00 - LSR cannot share the merge information. 733 Every LSR which is asked to encode the merging info has to update 734 the number of merge flags and to set its corresponding bits 735 accordingly. 737 8.3 Query Payload TLV 739 The Query Payload TLV is used to encode the payload that LSRs 740 implementing ECMP or similar load spreading should use when 741 selecting a downstream peer. 743 The format for the Query Payload TLV is: 745 0 1 2 3 746 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 1 747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 748 |0|0| Query Payload TLV TBD IANA| Length | 749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 750 | Payload Identifier | Reserved (=0) | 751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 752 | | 753 | Example payload ~ 754 ~ | 755 | | 756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 The Query Payload TLV carries an example of the payload of the LSP 759 that is of interest for tracing purposes. The payload example may 760 be: 761 - an MPLS label stack, 762 - an MPLS label stack followed by an IPv4 or IPv6 packet header or 763 - an IPv4 or IPv6 packet header. 765 The contents of the Query Payload TLV are identified via use of the 766 payload identifier (currently used as a bitmap) 767 0x01 - label stack present 768 0x02 - IP packet present 770 When the IP packet present flag is set, the IP version is determined 771 by examining the version number field of the packet header in the 772 example payload. 774 8.4 Status code summary 776 Status Code E Status Data Section Title 778 No LSP to query 1 TBD IANA "Query Message Procedures..." 779 Ambiguous label value 1 TBD IANA "Query Message Procedures..." 780 Payload Query TLV 1 TBD IANA "Query Message Procedures..." 781 Required 782 Message space 1 TBD IANA "Query Message Procedures..." 783 exhausted 785 9. Security Considerations 787 The Query mechanism inherits the same security mechanism described 788 in Section 5.0 of [4]. The Query mechanism provides an additional 789 security measure for cases when a node cannot share the queried 790 information. Such nodes have the option of hiding their information, 791 if their configuration requires it. Please refer to Section 4 of 792 this memo - "Behavior of LSRs with constraints in handling the query 793 messages" - for more details. 795 The Query mechanism focuses on the ability to trace the control 796 plane, the outcome of which may then be compared against the output 797 of data plane tracing tools to ensure system consistency. If the 798 control plane maintains a chain of trust from LSP ingress to egress 799 using mechanisms to secure individual adjacencies against known or 800 yet to be developed attacks, then LSP Query will produce useful 801 information. Where the chain of trust is incomplete, the partial- 802 query reply mechanism may be used to trace the control plane up to 803 the point of the boundary between trusted and untrusted network 804 elements on the LSP path. 806 10. IANA Considerations 808 RFC 3036 [4] defines several name spaces including the Message Type 809 Name Space, the TLV Type Name Space, and the Status Code Name Space. 810 This document makes the following assignments within those spaces. 812 10.1 Message Type Space Extension 814 The message types for Query Message, Query-Reply Message and Partial 815 Query-Reply Message are as follows: 817 Message Type 818 -------------------------------------- ---------- 819 Query Message TBD IANA 820 Query Reply Message TBD IANA 821 Partial Query Reply Message TBD IANA 823 10.2 TLV Type Name Space Extension 825 The TLV types for Query TLV, Query Label TLV and Query Merge Flags 826 TLV are as follows: 828 TLV Type 829 -------------------------------------- ---------- 830 Query TLV TBD IANA 831 Query Label TLV TBD IANA 832 Query Merge Flags TLV TBD IANA 833 Query Payload TLV TBD IANA 835 10.3 Status Code Space Extension 837 The Status codes are as follows: 839 Status Code Type 840 -------------------------------------- ---------- 841 No LSP to query TBD IANA 842 Ambiguous label value TBD IANA 843 Payload Query TLV Required TBD IANA 844 Message space exhausted TBD IANA 846 11. Acknowledgments 848 The authors would like to acknowledge the careful review and 849 comments of Jean-Pierre Coupal, Steve Hamilton, Don Fedyk, Gregory 850 Wright and Adrian Farrel. 852 12. Normative References 854 [1] B. Jamoussi et al., "Constraint-Based LSP Setup using LDP", RFC 855 3212, January 2002 857 [2] Peter Ashwood-Smith et al., "Improving Topology Data Base 858 Accuracy with LSP Feedback", Work in Progress, draft-ietf-mpls-te- 859 feed-03.txt. 861 [3] Ashwood-Smith P., Berger L., "Generalized MPLS - Signaling 862 Functional Description", Work in Progress, draft-ietf-mpls- 863 generalized-signaling-07.txt. 865 [4] Andersson et al., "LDP Specification", RFC 3036, January 2001. 867 13. Author's Addresses 869 Peter Ashwood-Smith Antonela Paraschiv 870 Nortel Networks Corp. Nortel Networks Corp. 871 P.O. Box 3511 Station C, 600 Technology Park Drive 872 Ottawa, ON K1Y 4H7 Billerica, MA 01821 873 Canada USA 874 Phone: +1 613-763-4534 phone: +1 978-288-6136 875 petera@nortelnetworks.com antonela@nortelnetworks.com 876 Dave Allan 877 Nortel Networks Corp. 878 P.O. Box 3511 Station C, 879 Ottawa, ON K1Y 4H7 880 Canada 881 Phone: +1 613-763-6362 882 dallan@nortelnetworks.com 884 Full Copyright Statement 886 Copyright (C) The Internet Society (2002). All Rights Reserved. This 887 document and translations of it may be copied and furnished to 888 others, and derivative works that comment on or otherwise explain it 889 or assist in its implementation may be prepared, copied, published 890 and distributed, in whole or in part, without restriction of any 891 kind, provided that the above copyright notice and this paragraph 892 are included on all such copies and derivative works. However, this 893 document itself may not be modified in any way, such as by removing 894 the copyright notice or references to the Internet Society or other 895 Internet organizations, except as needed for the purpose of 896 developing Internet standards in which case the procedures for 897 copyrights defined in the Internet Standards process must be 898 followed, or as required to translate it into languages other than 899 English. 901 The limited permissions granted above are perpetual and will not be 902 revoked by the Internet Society or its successors or assigns.