Internet Draft Network Working Group P. Ashwood-Smih Internet Draft A. Paraschiv Expiration Date: May 2001 Nortel Networks November 2000 MPLS LDP Query Message Description draft-ietf-mpls-lsp-query-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes the encoding and procedures for three new LDP messages, the Query Message and Query-Reply Message and Partial Query-Reply Message (the last one is almost identical to the Query- Reply message; therefore all references to the Query-Reply messages imply the Partial Query-Reply messages as well, unless otherwise specified). An LER sends a Query message when it needs to find out information about an LSP. The Query message is sent for an established LSP. The Query message can be used for LDP LSPs as well as for CR-LSPs. The queried data is encoded into the Query-Reply messages. Paraschiv, et. al. [Page 1] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 Contents 1 Introduction ............................................. 3 2 Overview ................................................. 3 2.1 LDP Overview ............................................. 4 2.2 CR-LDP Overview .......................................... 4 3 LDP Message Structure Overview ........................... 4 4 Behavior of LSRs with constraints in handling the query messages 5 4.1 LSR does not support the query messages .................. 6 4.2 LSR cannot share any information ......................... 6 4.3 LSR cannot share some of the queried information ........ 6 4.4 LSR can share the queried information ................... 7 5 Query Message ............................................ 7 5.1 Query Message encoding ................................ 8 5.2 Query Message Procedures ................................. 9 6 Reply Messages .......................................... 10 6.1 Query-Reply Message encoding .......................... 10 6.2 Query-Reply Message Procedures ........................... 12 6.3 Partial Query-Reply Message encoding .................. 13 6.4 Partial Query-Reply Message Procedures ................... 13 7 Query TLVs ............................................... 14 7.1 Query Label TLV .......................................... 15 7.2 Query Merge Flags TLV .................................... 15 7.3 Status code summary ..................................... 16 8 Acknowledgments .......................................... 16 9 References ............................................... 17 10 Author's Addresses ....................................... 18 Paraschiv, et. al. [Page 2] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 Changes from previous version: o Added description for the behavior of an LSR that is configured not to share the queried data. o Added a new type of Query message - Partial Query-Reply message; this new reply is introduced to address cases when the Query message doesn't get a reply back from the egress LER; it is used by the ingress LER to gather information about the LSP, up to the failure node in the path; it is recommended to be used when Query message fails to receive a Query-Reply). 1. Introduction The original Multiprotocol Label Switching (MPLS) architecture [MPLS-ARCH] was been defined to support the forwarding of data based on a label. The MPLS architecture does not assume a single label distribution protocol. A number of different label distribution protocols are being standardized. This draft describes the query mechanism for an LSP or CR-LSP. It specifies procedures and encodings for the new messages added for the query mechanism. Extensions to RSVP-TE to provide the same functionality are subject for future study and will be covered in future draft versions. The new LDP messages are: Query Message, Query-Reply Message and Partial Query-Reply Message. The following new TLVs are added to accommodate the encodings for the new query messages: - Query TLV - Query Label TLV - Query Merge Flags TLV LDP uses the TCP transport for session, advertisement and notification messages; i.e., for everything but the UDP-based discovery mechanism. The messages which are added to support the query mechanism are sent over TCP as well. 2. Overview Paraschiv, et. al. [Page 3] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 2.1. LDP Overview Label Distribution Protocol (LDP) defined in [LDP Specification] contains a set of procedures and messages by which Label Switched Routers (LSR) establish Label Switch Paths (LSP) through a network by mapping network layer routing information directly to data-link layer switched paths. LDP associates a Forwarding Equivalence Class (FEC) with each LSP it creates. The FEC associated with an LSP specifies which packets are mapped to that LSP. 2.2. CR-LDP Overview As described in [Constraint-Base LSP Setup using LDP], Constraint Base Routing (CR-LDP) offers the opportunity to extend the information used to setup paths beyond what is available for the routing protocol. 3. LDP Message Structure Overview As described in LDP Specification draft, all LDP messages have the following format: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U| Message Type | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Mandatory Parameters | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Optional Parameters | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ U bit Unknown message bit. Upon receipt of an unknown message, if U is Paraschiv, et. al. [Page 4] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 clear (=0), a notification is returned to the message originator; if U is set (=1), the unknown message is silently ignored. Message Type Identifies the type of message Message Length Specifies the cumulative length in octets of the Message ID, Mandatory Parameters, and Optional Parameters. Message ID 32-bit value used to identify this message. Used by the sending LSR to facilitate identifying notification messages that may apply to this message. An LSR sending a notification message in response to this message should include this Message Id in the Status TLV carried by the notification message; see Section "Notification Message". Mandatory Parameters Variable length set of required message parameters. Some messages have no required parameters. For messages that have required parameters, the required parameters MUST appear in the order specified by the individual message specifications in the sections that follow. Optional Parameters Variable length set of optional message parameters. Many messages have no optional parameters. For messages that have optional parameters, the optional parameters may appear in any order. 4. Behavior of LSRs with constraints in handling the query messages Upon receiving a Query message, an LSR has to behave according to its configuration constraints in handling the query messages and returning the queried information. The following cases were identified: Paraschiv, et. al. [Page 5] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 - the LSR does not support the code to handle the messages for the query mechanism - the LSR supports the code to handle the messages for the query mechanism, but it is configured not to return any data - the LSR supports the code to handle the messages for the query mechanism, but it is configured not to return part of the queried data - the LSR supports the code to handle the messages for the query mechanism, and it is configured to return all the data which is queried. The draft provides flexibility to handle each of the above cases. 4.1. LSR does not support the query messages In this case, the LSR has to behave as if it received an unknown message type. It has therefore to honor the U bit. 4.2. LSR cannot share any information In this case, the LSR is able to decode and process the query messages. However, it is configured to hide all the data. It should propagate the message after it encodes a zero-length TLV for its hop in the hop list in the Query message. When Query-Reply message is received from downstream, the LSR is requested to propagate the reply message upstream after it encodes the zero-length tlvs for the queried data. When the ingress receives back the reply, it can identify which TLVs are empty; it can therefore ignore the zero- length TLVs and process the rest of the data. Note: zero-length TLV encoding can be used for all types of queried information except the merge information. The LSR is requested to signal the fact that the merging information is private by encoding a special value in the corresponding merge bits (for more information on the merge flags values please refer to Query Merge Flags TLV section). 4.3. LSR cannot share some of the queried information In this case, the LSR is able to decode and process the query messages. It has to propagate the query messages. It has to encode values for the data types that it is willing to return and zero- length TLVs for values for the data that is hidden. Note: zero-length TLV encoding can be used for all types of queried Paraschiv, et. al. [Page 6] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 information except the merge information. The LSR is requested to signal the fact that the merging information is private by encoding a special value in the corresponding merge bits (for more information on the merge flags values please refer to Query Merge Flags TLV section). 4.4. LSR can share the queried information This is the normal case for an LSR. In this case, the LSR's behavior has to follow the query and replies procedures described in the following sections of the draft. In order to have consistency among data encoded in the query and reply messages, each LSR which can propagate the messages has to encode its information in the query and in the reply messages. The decision that an LSR can share the queried information has to be controlled through configuration flags. This way each node along the path can protect its data if they consider it private. Note: It would be more efficient to control/restrict the private data per MPLS cloud (inter MPLS domain) and not per LSR node (inter and intra MPLS domain). When there are different MPLS clouds which have nodes belonging to different vendors, the control of the private information could be restricted to the boundary nodes. Within an MPLS domain, there should be no restrictions on the queried information. It would be useful to have some knowledge on which are the nodes on the boundaries and have only those hiding the queried data. Because there is no mechanism to identify which are the boundary nodes, this is subject for future study. 5. Query Message This sections describes the Query message and its encodings and procedures. This message is meant to be used to gather information about an LSP. It can be sent at any time for an established LSP. The draft currently describes the procedures for the cases when the Query Message is initiated by the ingress LER. Future versions of the draft may add the procedures for the query message when issued from a core LSR or from egress. The Query Message can be used to gather information about: Paraschiv, et. al. [Page 7] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 - LSRs which form the LSP - labels along the LSP - information on what LSRs are merging points along the path - unused bandwidth (as described in "Improving Topology Data Base Accuracy with LSP Feedback") - congestion status - round trip delay - anything that is needed in the future and can be computed and encoded in a TLV. The queried information is encoded in the Query-Reply message which is sent back upstream, as a response to the Query message. 5.1. Query Message encoding The encoding for the Query message is: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Query (0x0409) | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Query Label TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Query TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Hop Count TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional Parameters | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Message ID 32-bit value used to identify this message. Query Label TLV The label associated to the LSP which is queried. This TLV is a list of Generalized Label TLVs [OPTICAL reference]. The Generalized Label TLV provides a more generic encoding for different types of labels. Most of the time the list has one element; this is the case when the LSP is not tunneled. For tunneled LSPs, the Label TLV has more that one element; it has to behave like a label stack (it contains the previous label and the tunnel's label). See Section Query Label TLV for more information Paraschiv, et. al. [Page 8] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 on Label TLV encoding. Query TLV What to query. See Section Query TLV for encoding. Hop Count TLV Specifies the number of LSR hops that can still be traversed before the message is dropped due to loop detection. It is initialized to the max value of 255 (or the configured value, if any). Every LSR that receives the Query Message has to subtract 1 from the Hop Count value. The Query message should be dropped if the hop count value becomes zero; a Notification signaling Loop Detection should be sent in reply to the sender of the message. See [LDP Specification] for Hop Count TLV encoding. Optional Parameters This variable length field contains 0 or more parameters, each encoded as a TLV. Optional Parameter Length Value ER TLV var See CR-LDP The ER TLV is a list of hops. It is used when the Query flag Q3 is set. Every LSR should add its IP address. The address to be added should be the outgoing interface address. Addresses are organized as a last-in-fist-out stack (the first address in TLV is considered the top). By carrying this TLV in the Query Message and preserving this order for the hops, we allow the possibility to interwork the Query Message with the RSVP Path message. 5.2. Query Message Procedures The LER ingress initiates the Query message. It populates the Query TLV Parameters according to what kind of information it wants to gather. The query for an LSP is done by its label. The only data that the Query Message carries is the list of hops. This way, each node along the path will have a complete route from source to destination. The hop list information is useful for network management. Upon receiving a Query Message, an LSR decodes the label to identify which LSP is queried. If it cannot find the LSP which is using the label, it sends back a Notification message with "No Lsp to query" status. Otherwise, it checks which is the out label which is bound to the queried in-label and which is the downstream LSR peer. It replaces the in-label from Query Label TLV with the out-label used by Paraschiv, et. al. [Page 9] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 the LSP. It then passes the Query message to the downstream peer. When the Query message gets to a tunnel, it has to be able to handle both the previous label and the tunnel's label. The Query Label TLV behaves like a label stack. The previous label is pushed and the tunnel label is used. At the end of the tunnel, we need to pop the stack and start substituting the lower level labels. Upon receiving the Query message, the egress node has to reply with a Query Reply Message. The Query-Reply Message contains the Query TLV which was received in the Query Message. The Query TLV tells the LSRs along the path which information is being queried and allows intermediate LSRs to piggy back their own queried information on the Query reply message. 6. Reply Messages These messages are propagated upstream. There are situations in which the Query message does not reach the end point of the queried LSP. In these scenarios it would be useful if the ingress LSR gathered at least some information about the LSRs which are along the path, up to the one that failed. The Partial Query-Reply message provides this mechanism. It is recommended to use the Partial Query- Reply messages when a Query message fails. There are two types of reply messages: - Query-Reply message (final reply) - Partial Query-Reply message. Both of the reply messages are described in the following sections. 6.1. Query-Reply Message encoding This message is generated by the end point of the LSP. It is propagated upstream, by each LSR along the path. Paraschiv, et. al. [Page 10] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 The encoding for the Query-Reply message is: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Query-Reply (0x0410) | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Query TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MessageId TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional Parameters | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Message ID 32-bit value used to identify this message. Query TLV What is to be queried. See Section Query TLV for encoding. Message Id TLV The value of this parameter is the message id of the corresponding Query message. Optional Parameters This variable length field contains 0 or more parameters, each encoded as a TLV. The optional parameters are: Optional Parameter Length Value ER TLV var See CR-LDP Query Label TLV var See Query Label TLV section IPV4/6 specified link feedback TLV See Improving Topology ... Query Merge Flags TLV var See Query Merge Flags TLV section For simplicity we reuse here TLV types defined for CR-LDP and LDP. They are: - IPV4/6 specified link feedback TLV - ER TLV - Generalized Label TLV (used in the Query Label TLV encoding) - Hop Count TLV. The IPV4/6 specified link feedback TLV is used when the Q1 flag from Paraschiv, et. al. [Page 11] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 the Query TLV is set. It is used to encode the bandwidth information. For more information on query flags, Q1, ... Q6, refer to Query TLV section. The ER TLV is a list of hops. It is used when the Query flag Q3 is set. Every LSR should add its IP address. The address to be added should be the outgoing interface address. Addresses are organized as a last-in-fist-out stack (the first address in TLV is considered the top). The Query Label TLV is a list of labels. It is used when the Query flag Q2 is set. It is populated with the labels used for the path which is queried. For tunneled LSPs, the Query Label TLV represents a list of labels associated to the lowest level tunnel. If Q3 and Q2 flags are set, the labels should be encoded in the same order as the hops. Query Merge Flags TLV is a list of pairs of bits. It has variable length and every two bits in the mask will correspond to an LSR along the path. Its length is rounded up to the next byte. If Q6 is set, every LSP along the path will have to set its corresponding bits in the mask. The bits have to be set in the same order as the labels and hops. Usually, Q6 is set when Q2 set and/or Q3 set. For more information for the TLV encodings of the TLVs which are reused, please see CR-LDP draft, LDP draft and IMPROVING TOPOLOGY DATA BASE ACCURACY WITH LSP FEEDBACK VIA CR_LDP draft. 6.2. Query-Reply Message Procedures A Query-Reply message is initiated by an egress node which receives a Query message, if the egress is able to identify the queried LSP. If not, the egress replies with a Notification message with "No Lsp to query" status. Upon receiving the Query message, the egress node has to reply with a Query Reply message. The egress node has to encode into the Query- Reply message a MessageId Tlv. The mapping between a Query and a Query-Reply Message is done based on the message id. Besides the MessageId Tlv, the egress has to encode the information that was queried (bandwidth, path, etc). After the encoding is done, the query reply message is sent back, on the reversed path, towards the ingress. Every LSR across the LSP has to encode its information according to what query flags are set. Paraschiv, et. al. [Page 12] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 6.3. Partial Query-Reply Message encoding The Partial Query-Reply message is initiated by tandem LSRs along the queried path. The message is generated only if the following rules apply: - if the Query message asked for partial replies (the Query message signals this request through Q8 bit) - if the tandem LSR is configured to provide partial replies. The encoding for the Partial Query-Reply message is identical to the Query-Reply, except the message type. For more details on the encoding please refer to the Query-Reply encoding. 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|Partial Query-Reply (0x0411) | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Query TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MessageId TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional Parameters | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 6.4. Partial Query-Reply Message Procedures The procedures are similar to the Query-Reply's procedures. Upon receiving a Query message, a tandem LSR will check the flag from the Query message (Q8) which signals if the partial replies are requested by the ingress node. If the flag is set, the LSR has to check next if it is configured to fulfill this request. If the LSR supports partial replies, it has to create a Partial Query-Reply and encode the queried data and send it upstream like any Query-Reply messages. It has then to process the Query message according to the Query message procedures. When an LSR receives a Partial Query-Reply from upstream, it should encode its information according to what is queried and propagate the message. It is recommended to use the Partial Query mechanism when the Query message fails (when the ingress LER does not receive a Query-Reply message in response to a Query message). Paraschiv, et. al. [Page 13] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 7. Query TLVs The Query TLV is used to specify the information being queried. The Query TLV travels in the Query message to the egress node, where it is copied into a reverse flowing Query-Reply messages and used by the egress and intermediate LSRs to know what information is being queried. The format for the Query TLV is: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Query TLV (0x0840) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Query Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Query Flags can be set according to what the Query is used for. +--+--+--+--+--+--+--+--+ |Q8|Re|Q6|Q5|Q4|Q3|Q2|Q1| +--+--+--+--+--+--+--+--+ They can be: - Q1 : query the bandwidth; if set, the LSR that receives the Query message has to encode the bandwidth that is available on the link (unused bandwidth); - Q2 : query the labels which are associated to each hop in the path; - Q3 : query the LSRs which form the LSP which is queried; if set, the LSR that received the Query-Reply message has to encode the current hop in the ER-TLV - Q4 : reserved for congestion status; < format - TBD > - Q5 : query the round trip delay; if set, the LSR should fill in the link delay information if available; < format - TBD > - Q6 : query which LSPs along the path are merging points; if set, the LSR that receives the Query message has to encode if it is a merging point; the encoding is done in the Query Merge flags TLV. - Q8 : if set, the ingress requests partial query-replies; Paraschiv, et. al. [Page 14] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 7.1. Query Label TLV The Query Label TLV is used to encode the labels used along the path which is queried. Note: Query Label TLV is used in both Query and Query Reply. It is a required parameter in the Query message and it is an optional parameter in Query Reply message. When being used in the Query message, it carries the label or stack of labels which are being followed and queried. When being used in the Query Reply message, it carries the list of labels which make up the queried path. The format for the Query Label TLV is: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Query Label TLV (0x0841)| Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Generalized Label TLV 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Generalized Label TLV n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Generalized Label TLV is used to encode labels along the path. Please refer to [OPTICAL reference] for more information on the Generalized Label TLV encoding. If the Q2 flag is set, every LSR has to encode the out-label corresponding to the queried LSP. In the Query Label TLV, labels are organized as a last-in-fist-out stack (the first label in TLV is considered the top). They should be encoded in the same order as the hops and the merge flags. 7.2. Query Merge Flags TLV The Query Merge Flags TLV is used to encode the information about which LSRs along the path the queried LSP is being merged into. Paraschiv, et. al. [Page 15] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 The format for the Query Merge Flags TLV is: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Merge Flags TLV (0x0842) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Number of merge flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Merge flags | | | ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Query Merge Flags TLV has 4 bytes field to store the number of merge flags. This number is equal to the number of LSRs which are traversed by the Query-Reply Message. Each 2 bits in the Merge flags field represent the merge information for an LSR. The bits are set to 01 if the LSR does not do merge for the queried LSP and are set to 10 otherwise. If the LSR want to hide the merging information, it has to set the merging flags to 00. The length of the encoding is rounded up to the next byte. Every LSR which is asked to encode the merging info into this TLV has to update the Number of merge flags and to set its corresponding bits accordingly. 7.3. Status code summary Status Code E Status Data Section Title No Lsp to query 1 0x0000001a "Query Message Procedures..." 8. Acknowledgments The authors would like to acknowledge the careful review and comments of Jean-Pierre Coupal, Steve Hamilton, Don Fedyk and Gregory Wright. Paraschiv, et. al. [Page 16] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 9. References [CR-LDP] Jamoussi et al., "Constraint-Based LSP Setup using LDP", draft-ietf-mpls-cr-ldp-03.txt, October 1999 [LDP] Andersson et al., "LDP Specification", draft-ietf-mpls-ldp-07.txt, May 2000. [RSVP-RR] Berger L., Gan D., Swallow G., Pan P., Tommasi F., Molendini S., "RSVP Refresh Overhead Reduction Extensions", draft-ietf-rsvp- refresh-reduct-04.txt. [CR-LDP] Peter Ashwood-Smith et al., "Improving Topology Data Base Accuracy with LSP Feedback", draft-ietf-mpls-te-feed-01.txt Ashwood-Smith P., Berger L., "Generalized MPLS-Signaling Functional Description" draft-ashwood-generalized-mpls-signaling-00.txt Paraschiv, et. al. [Page 17] Internet Draft draft-ietf-mpls-lsp-query-01.txt November 2000 10. Author's Addresses Peter Ashwood-Smith Antonela Paraschiv Nortel Networks Corp. Nortel Networks Corp. P.O. Box 3511 Station C, 600 Technology Park Drive Ottawa, ON K1Y 4H7 Billerica, MA 01821 Canada USA Phone: +1 613-763-4534 phone: +1 978-288-6136 petera@nortelnetworks.com antonela@nortelnetworks.com Full Copyright Statement Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. Paraschiv, et. al. [Page 18]