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Network Working Group                                          K. NagamiRequest for Comments: 3038                                    Y. KatsubeCategory: Standards Track                                  Toshiba Corp.                                                               N. Demizu                                                        WaterSprings.ORG                                                                H. Esaki                                                          Univ. of Tokyo                                                               P. Doolan                                                       Ennovate Networks                                                            January 2001VCID Notification over ATM link for LDPStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2001).  All Rights Reserved.Abstract   The Asynchronous Transfer Mode Label Switching Router (ATM-LSR) is   one of the major applications of label switching.  Because the ATM   layer labels (VPI and VCI) associated with a VC rewritten with new   value at every ATM switch nodes, it is not possible to use them to   identify a VC in label mapping messages.  The concept of Virtual   Connection Identifier (VCID) is introduced to solve this problem.   VCID has the same value at both ends of a VC.  This document   specifies the procedures for the communication of VCID values between   neighboring ATM-LSRs that must occur in order to ensure this   property.1. Introduction   Several label switching schemes have been proposed to integrate Layer   2 and Layer 3.  The ATM Label Switching Router (ATM-LSR) is one of   the major applications of label switching.   In the case of ATM VCs, the VPI and VCI labels are, in the general   case, rewritten with new values at every switch node through which   the VC passes and cannot be used to provide end to end identification   of a VC.Nagami, et al.              Standards Track                     [Page 1]

RFC 3038               VCID Notification for LDP            January 2001   In the context of MPLS 'stream', which are classes of packets that   have some common characteristic that may be deduced by examination of   the layer 3 header in the packets, are bound to layer 2 'labels'. We   speak of stream being 'bound' to labels.  These bindings are conveyed   between peer LSRs by means of a Label Distribution Protocol [LDP].   In order to apply MPLS to ATM links, we need some way to identify ATM   VCs in LDP mapping messages.  An identifier called a Virtual   Connection ID (VCID) is introduced.  VCID has the same value at both   ends of a VC.  This document specifies the procedures for the   communication of VCID values between neighboring ATM-LSRs that must   occur in order to ensure this property.2. Overview of VCID Notification Procedures2.1 VCID Notification procedures   The ATM has several types of VCs (transparent point-to-point   link/VP/PVC/SVC).  A transparent point-to-point link is defined as   one that has the same VPI/VCI label at both ends of a VC.  For   example, two nodes are directly connected (i.e., without intervening   ATM switches) or are connected through a VP with the same VPI value   at both ends of the VP.   There are two broad categories of VCID notification procedures;   inband and outband.  The categorization refers to the connection over   which the messages of the VCID notification procedure are forwarded.   In the case of the inband procedures, those messages are forwarded   over the VC to which they refer.  In contrast the out of band   procedures transmit the messages over some other connection (than the   VC to which they refer).   We list below the various types of link and briefly mention the VCID   notification procedures employed and the rational for that choice.   The procedures themselves are discussed in detail in later sections.   Transparent point-to-point link : no VCID notification       VCID notification procedure is not necessary because the label       (i.e., VPI/VCI) is the same at each end of the VC.   VP : inband notification or VPID notification or no notification    - Inband notification      VCID notification is needed because the VPI at each end of the VC      may not be the same.  Inband VCID notification is used in this      case.Nagami, et al.              Standards Track                     [Page 2]

RFC 3038               VCID Notification for LDP            January 2001    - VPID notification      VCID notification is needed because the VPI at each end of the VC      may not be the same.  VPID notification is used in this case.    - No notification      If a node has only one VP to a neighboring node, VCID notification      procedure is not mandatory.  The VCI can be used as the VCID.      This is because the VCI value is the same at each end of the VP.   PVC : inband notification      Inband VCID notification is used in this case because the labels      at each end of the VC may not be the same.   SVC : there are three possibilities    - Outband notification      If a signaling message has a field which is large enough to carry      a VCID value (e.g., GIT [GIT]), then the VCID is carried directly      in it.    - Outband notification using a small-sized field      If a signaling message has a field which is not large enough to      carry a VCID value, this procedure is used.    - Inband notification      If a signaling message can not carry user information, this      procedure is used.      When an LSP is a point-to-multipoint VC and an ATM switch in an      LSR is not capable of VC merge, it may cause problems in      performance and quality of service.  When the LSR wants to add a      new leaf to the LSP, it needs to split the active LSP temporarily      to send an inband notification message.2.2 VC direction   A VC has a directionality.  The VCID procedure for a VC is always   triggered from the upstream node of the VC, i.e., the upstream node   notifies the downstream node of the VCID.   If bidirectional use of a label switched VC is allowed, the label   switched VC is said to be bidirectional.  In this case, two VCID   procedures are taken, one for each direction.   If bidirectional use of a label switched VC is not allowed, the label   switched VC is said to be unidirectional.  In this case, only one   VCID procedure is taken for the allowed direction.   VC directionality is communicated through LDP.Nagami, et al.              Standards Track                     [Page 3]

RFC 3038               VCID Notification for LDP            January 20013. VCID Notification Procedures3.1 Inband Notification Procedures3.1.1 Inband Notification for Point-to-point VC   VCID notification is performed by transmitting a control message   through the VC newly established (by signalling or management) for   use as an label switched path (LSP).  The procedure for VCID   notification between two nodes A and B is detailed below.   0. The node A establishes a VC to the destination node B (by      signalling or management).   1. The node A selects a VCID value.   2. The node A sends a VCID PROPOSE message which contains the VCID      value and a message ID through the newly established VC to the      node B.   3. The node A establishes an association between the outgoing label      (VPI/VCI) for the VC and the VCID value.   4. The node B receives the message from the VC and establishes an      association between the VCID in the message and the incoming      label(VPI/VCI) for the VC.  Until the node B receives the LDP      Request message, the node B discards any packet received over the      VC other than the VCID PROPOSE message.   5. The node B sends an ACK message to the node A.  This message      contains the same VCID and message ID as specified in the received      message.  This message is sent through the VC for LDP.   6. When node A receives the ACK message, it checks whether the VCID      and the message ID in the message are the same as the registered      ones.  If they are the same, node A regards that node B has      established the association between the VC and VCID.  Otherwise,      the message is ignored.  If the node A does not receive the ACK      message with the expected message ID and VCID during a given      period, the node A resends the VCID PROPOSE message to the node B.   7. After receiving the proposer ACK message, the node A sends an LDP      REQUEST message to the node B.  It contains the message ID used      for VCID PROPOSE.  When the node B receives the LDP REQUEST      message, it regards that the node A has received the ACK      correctly.  The message exchange using VCID PROPOSE, VCID ACK, and      LDP REQUEST messages constitutes a 3-way handshake.  The 3-way      handshake mechanism is required since the transmission of VCIDNagami, et al.              Standards Track                     [Page 4]

RFC 3038               VCID Notification for LDP            January 2001      PROPOSE message is unreliable.  Once the 3-way handshake      completes, the node B ignores all VCID PROPOSE messages received      over the VC.  The node B sends an LDP Mapping message, which      contains the VCID value in the label TLV.       Node A           Node B         |                |         |--------------->|     VCID PROPOSE         |                |         |<---------------|     VCID ACK         |                |         |--------------->|     LDP Label Request         |                |         |<---------------|     LDP Label Mapping3.1.2 Inband notification for point-to-multipoint VC   Current LDP specification does not support multicast.  But the VCID   notification procedure is defined for future use.  VCID notification   is performed by sending a control message through the VC to be used   as an LSP.  The upstream node assigns the VCID value.  The procedure   by which it notifies the downstream node of that value is given   below.  The procedure is used when a new VC is created or a new leaf   is added to the VC.   First, the procedure for establishing the first VC is described.   1. The upstream node assigns a VCID value for the VC.  When the VCID      value is already assigned to a VC, it is used for VCID.   2. The upstream node sends a message which contains the VCID value      and a message ID through the VC used for an LSP.  This message is      transferred to all leaf nodes.   3. The upstream node establishes an association between the outgoing      label for the VC and the VCID value.   4. When the downstream nodes receiving the message already received      the LDP REQUEST message for the VC, the received message is      discarded.  Otherwise, the downstream nodes establish an      association between the VCID in the message and the VC from which      the message is received.   5. The downstream nodes send an ACK message to the upstream node.   6. After the upstream node receives the ACK messages, the upstream      node and the downstream nodes share the VCID.  The upstream node      sends the LDP REQUEST message in order to make a 3-way handshake.Nagami, et al.              Standards Track                     [Page 5]

RFC 3038               VCID Notification for LDP            January 2001       Upstream        Downstream 1   Downstream 2         |                |               |         |-----------+--->|               |   VCID PROPOSE         |           +------------------->|         |                |               |         |<---------------|               |         |  VCID ACK      |               |         |<-------------------------------|   VCID ACK   Second, the procedure for adding a leaf to the existing point-to-   multipoint VC is described.   0. The upstream node adds the downstream node, using the ATM      signaling.   1. The VCID value which already assigned to the VC is used.   2. The upstream node sends a message which contains the VCID value      and a message ID through the VC used for an LSP.  This message is      transferred to all leaf nodes.   3. When the downstream nodes receiving the message already received      the LDP REQUEST message for the VC, the received message is      discarded.  Otherwise, the downstream nodes establish an      association between the VCID in the message and the VC from which      the message is received.   4. After the upstream node receives the ACK messages, the upstream      node and the downstream nodes share the VCID.  The upstream node      sends the LDP REQUEST message in order to make a 3-way handshake.3.2 Outband Notification using a small-sized field   This method can be applied when a VC is established using an ATM   signaling message and the message has a field which is not large   enough to carry a VCID value.   SETUP message of the ATM Forum UNI 3.1/4.0 has a 7-bit mandatory   field for the user.  This is a user specific field in the Layer 3   protocol field in the BLLI IE (Broadband Low Layer Information   Information Element).   The BLLI value is used as a temporary identifier for a VC during a   VCID notification procedure.  This mechanism is defined as "Outband   Notification using a small-sized field".  The BLLI value of a new VC   must not be assigned to other VCs during the procedure to avoid   identifier conflict.  When the association among the BLLI value, aNagami, et al.              Standards Track                     [Page 6]

RFC 3038               VCID Notification for LDP            January 2001   VCID value, and the corresponding VC is established, the BLLI value   can be reused for a new VC.  VCID values can be assigned   independently from BLLI values.       Node A           Node B         |                |         |--------------->|     ATM Signaling with BLLI         |<---------------|         |                |         |--------------->|     VCID PROPOSE with BLLI         |                |         |<---------------|     VCID ACK         |                |         |--------------->|     LDP Label Request         |                |         |<---------------|     LDP Label Mapping   A point-to-multipoint VC can also be established using ADD_PARTY of   the ATM Forum Signaling.  ADD_PARTY adds a new VC leaf to an existing   VC or an existing VC tree.  In this procedure, the BLLI value of   ADD_PARTY has to be the same value as that used to establish the   first point-to-point VC of the tree.  The same BLLI value can be used   in different VC trees only when these VC trees can not add a leaf at   the same time.  As a result, the BLLI value used in the signaling   must be determined by the root node of the multicast tree.   [note]      BLLI value is unique at the sender node.  But BLLI value is not      unique at the receiver node because multiple sender nodes may      allocate the same BLLI value.  So, the receiver node must      recognize BLLI value and the sender address.  ATM Signaling      messages (SETUP and ADD_PARTY) carry both the BLLI and the sender      ATM address.  The receiver node can realize which node sends the      BLLI message.3.2.1 Outband notification using a small-sized field for      point-to-point VC   This subsection describes procedures for establishing a VC and for   notification of its VCID between neighboring LSRs for unicast   traffic.Nagami, et al.              Standards Track                     [Page 7]

RFC 3038               VCID Notification for LDP            January 2001   The procedure employed when the upstream LSR assigns a VCID is as   follows.   1. An upstream LSR establishes a VC to the downstream LSR using ATM      signaling and supplies a value in the BLLI field that it is not      currently using for any other (incomplete) VCID notification      transaction with this peer.   2. The upstream LSR sends the VCID PROPOSE message through the VC for      LDP to notify the downstream LSR of the association between the      BLLI and VCID values.   3. The downstream LSR establishes the association between the VC with      the BLLI value and the VCID and sends an ACK message to the      upstream LSR.   4. After the upstream LSR receives the ACK message, it establishes      the association between the VC and the VCID.  The VC is ready to      be used.  At this time the BLLI value employed in this transaction      is free for reuse.   5. After VCID notification, the upstream node sends the LDP REQUEST      message to the downstream node.  The downstream node sends the LDP      mapping message, which contains the VCID value in the label TLV of      LDP.3.2.2 Outband notification using a small-sized field      for point-to-multipoint VC   This subsection describes procedures for establishing the first VC   for a multicast tree and for adding a new VC leaf to an existing VC   tree including the notification of its VCID for a multicast stream   using point-to-multipoint VCs.   In this procedure, an upstream LSR determines both the VCID and BLLI   value in the multicast case.  The reason that the BLLI value is   determined by an upstream LSR is described above.   First, the procedure for establishing the first VC is described.   1. An upstream LSR establishes a VC by the ATM Forum Signaling      between the downstream LSR with a unique BLLI value at this time.   2. The upstream LSR notifies the downstream LSR of a paired BLLI      value and VCID using a message dedicated for this purpose.Nagami, et al.              Standards Track                     [Page 8]

RFC 3038               VCID Notification for LDP            January 2001   3. The downstream LSR establishes the association between the VC with      the BLLI value and the VCID and sends an ACK message to the      upstream LSR.  If the VCID is used by some other VC between the      upstream and downstream LSRs, the old VC is discarded.   4. After the upstream LSR receives the ACK message, the VC is ready      to be used and the BLLI value can be used for another VC.   Second, the procedure for adding a leaf to the existing point-to-   multipoint VC is described.   1. The upstream LSR establishes a VC by the ATM Forum Signaling      between its downstream LSR with the BLLI value that was used      during the first signaling procedure.  If another VC is using the      BLLI value at the same time, the upstream waits for the completion      of the signaling procedure that is using this BLLI value.   2. Go to step 2 of the procedure for the first VC.3.3 Outband notification   This method can be applied when a VC is established using a ATM   signaling message and the message has a field (e.g., GIT [GIT]) which   is large enough to carry a VCID value.  Message format is described   in [GIT].  After the VCID notification, the node A sends the LDP   request message is sent to the node B.  Then, the node B sends the   LDP mapping message to the node A.       Node A           Node B         |                |         |--------------->|   ATM signaling with VCID         |<---------------|         |                |         |--------------->|     LDP Label Request         |                |         |<---------------|     LDP Label Mapping4 VPID Notification Procedure   The approach that is used for the VCID notification procedure is also   applicable to share the same identifier between both ends for a VP.   VPID notification procedure is defined for this purpose.   A distinct VPID notification procedure is performed for each   direction of each VP.Nagami, et al.              Standards Track                     [Page 9]

RFC 3038               VCID Notification for LDP            January 2001   After the VPID notification is finished for a VP, a VCID of a VC in   the VP is constructed with the VPID(MSB) and VCI(LSB) of the VC.  The   VCID can be used by LDP without performing VCID notification   procedure.  The message sequence is given below.   1. An upstream node sends the VPID PROPOSE message. In the case of      bidirectional label switched VC, both the upstream and downstream      nodes use VCI=33.  In the case of unidirectional label switched      VC, the node which has larger LDP Identifier uses VCI=33 and the      other node uses VCI=34.  Note that VCI=32, which is used for      unlabeled packet transfer, is not used for VPID notification      procedure so that the same encapsulation method can be applied for      both VPID procedure and inband VCID procedure.   2. The downstream node sends the VPID ACK message.   3. The upstream node sends the LDP Label Request message.   4. The downstream node sends the LDP Label Mapping message.5 VCID Message Format5.1 VCID Messages   An LDP VCID message consists of the LDP [LDP] fixed header followed   by one or more TLV.  A VCID PROPOSE inband message and a VPID PROPOSE   message are sent as a null encapsulation packet through a VC to be   used as an LSP.  There is only the label stack header before the LDP   VCID PDU.  A label value in the label stack entry [ENCAPS] for the   VCID PROPOSE inband message and the VPID PROPOSE message are 4.   Other messages are sent as TCP packets.  This is the same as LDP.   The VCID message type field is as follows:         VCID Propose inband Message  = 0x0501         VCID Propose Message         = 0x0502         VCID ACK Message             = 0x0503         VCID NACK Message            = 0x0504         VPID Propose inband Message  = 0x0505         VPID ACK Message             = 0x0506         VPID NACK Message            = 0x05075.1.1 VCID Propose inband Message   This message is sent as a null encapsulation packet with LDP header   and label stack header through a VC to be used as an LSP.  The label   value is 4.  The reserved label value is required because the   downstream node may receive this message after receiving the LDPNagami, et al.              Standards Track                    [Page 10]

RFC 3038               VCID Notification for LDP            January 2001   Label Request message in the case of point-to-multipoint VC.  The   downstream node must distinguish the VCID PROPOSE message from other   messages and ignore the VCID PROPOSE message when the node already   received the LDP Label Request message for the VC.    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|VCID Inband Propose (0x0501) |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Label TLV                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message Id     Four octet integer used to identify this message.   Label TLV     Label TLV contains VCID value.  Type of label TLV is VCID(0x0203).5.1.2 VCID Propose Message   An LSR uses the VCID PROPOSE message for the VCID notification   procedure of the outband notification using a small-sized field.   This message is sent through the VC for the LDP.    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|  VCID Propose (0x0502)      |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Label TLV                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Temporary ID TLV                    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message ID     Four octet integer used to identify this message.   Label TLV     Label TLV contains VCID value.  Type of label TLV is VCID(0x0203).Nagami, et al.              Standards Track                    [Page 11]

RFC 3038               VCID Notification for LDP            January 2001   Temporary ID TLV     The value carried in the user specific field in the layer 3     protocol field in the BLLI ID in the ATM Forum UNI 3.1/4.0 Type of     label TLV is VCID temporary ID(0x0702).5.1.3 VCID ACK Message   An LSR send the VCID ACK message when the LSR accepts the VCID   PROPOSE message.    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|  VCID ACK     (0x0503)      |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Label TLV                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VCID Message ID                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message ID     Four octet integer used to identify this message.   Label TLV     The label TLV contains the VCID value of the received VCID PROPOSE     message.  Type of label TLV is VCID(0x0203).   VCID Message ID     This value is the same as that of received VCID PROPOSE message.5.1.4 VCID NACK Message   An LSR send the VCID NACK message when the LSR does not accept the   VCID PROPOSE message.Nagami, et al.              Standards Track                    [Page 12]

RFC 3038               VCID Notification for LDP            January 2001    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|  VCID NACK    (0x0504)      |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Label TLV                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VCID Message ID                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message ID     Four octet integer used to identify this message.   Label TLV     The label TLV contains the VCID value of the received VCID PROPOSE     message.  Type of label TLV is VCID(0x0203).   VCID Message ID     This value is the same as that of received VCID PROPOSE message.5.1.5 VPID Propose inband Message   This message is sent as a null encapsulation packet with LDP header   and label stack header through a VC to be used as an LSP.  The label   value is 4.  The downstream node must distinguish the VPID PROPOSE   message from other messages and ignore the VPID PROPOSE message when   the node already received the LDP Label Request message for the VC.    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|VPID Inband Propose (0x0505) |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VPID TLV                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message Id     Four octet integer used to identify this message.Nagami, et al.              Standards Track                    [Page 13]

RFC 3038               VCID Notification for LDP            January 2001   VPID TLV     VPID TLV contains VPID value.  Type of label TLV is VPID(0x0703).5.1.6 VPID ACK Message   An LSR send the VPID ACK message when the LSR accepts the VPID   PROPOSE message.    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|  VPID ACK     (0x0506)      |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VPID TLV                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VCID Message ID                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message ID     Four octet integer used to identify this message.   VPID TLV     The VPID TLV contains the VPID value of the received VPID PROPOSE     message.   VCID Message ID     This value is the same as that of received VCID PROPOSE message.Nagami, et al.              Standards Track                    [Page 14]

RFC 3038               VCID Notification for LDP            January 20015.1.7 VPID NACK Message   An LSR send the VPID NACK message when the LSR accepts the VPID   PROPOSE message.    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|  VPID NACK    (0x0507)      |      Message Length           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Message ID                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VPID TLV                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           VCID Message ID                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Optional Parameters                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Message ID     Four octet integer used to identify this message.   VPID TLV     The VPID TLV contains the VPID value of the received VPID PROPOSE     message.   VCID Message ID     This value is the same as that of received VCID PROPOSE message.5.2 Objects5.2.1 VCID Label TLV   An LSR uses VCID Label TLV to encode labels for use on the link which   does not have the same data link label at both ends of a VC.    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|F|VCID Label   (0x0203)      |          Length               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                              VCID                             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   VCID     This is 4 byte VCID value.Nagami, et al.              Standards Track                    [Page 15]

RFC 3038               VCID Notification for LDP            January 20015.2.2 VCID Message ID TLV    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|F|VCID Message ID(0x0701)    |          Length               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       VCID Message ID                         |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   VCID Message ID     This is 4 byte VCID Message ID5.2.3 VCID Temporary ID TLV   An LSR uses the VCID temporary ID TLV for the VCID notification   procedure of the outband notification using a small-sized field.    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|F| VCID Temporary ID (0x0702)|          Length               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  Temporary ID |   +-+-+-+-+-+-+-+-+   Temporary ID:     The value carried in the user specific field in the layer 3     protocol field in the BLLI ID in the ATM Forum UNI 3.1/4.05.2.4 VPID Label TLV   An LSR uses VPID TLV for the VPID notification procedure.    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|F|   VPID      (0x0703)      |          Length               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |            VPID               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   VPID     This is 2 byte VPID value.Nagami, et al.              Standards Track                    [Page 16]

RFC 3038               VCID Notification for LDP            January 2001Security Considerations   This document does not introduce new security issues other than those   present in the LDP and may use the same mechanisms proposed for this   technology.Acknowledgments   The authors would like to acknowledge the valuable technical comments   of Yoshihiro Ohba, Shigeo Matsuzawa, Akiyoshi Mogi, Muneyoshi Suzuki,   George Swallow and members of the LAST-WG of the WIDE Project.References   [LDP]    Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B.            Thomas, "LDP Specification",RFC 3036, January 2001.   [GIT]    Suzuki, M., "The Assignment of the Information Field and            Protocol Identifier in the Q.2941 Generic Identifier and            Q.2957 User-to-user Signaling for the Internet Protocol",RFC 3033, January 2001.   [ENCAPS] Rosen, E., Viswanathan, A. and R. Callon, "MPLS Label Stack            Encoding",RFC 3032, January 2001.Nagami, et al.              Standards Track                    [Page 17]

RFC 3038               VCID Notification for LDP            January 2001Authors' Addresses   Ken-ichi Nagami   Computer & Network Development Center, Toshiba Corporation,   1, Toshiba-cho, Fuchu-shi,   Tokyo, 183-8511, Japan   Phone: +81-42-333-2884   EMail: ken.nagami@toshiba.co.jp   Noritoshi Demizu   WaterSprings.ORG   1-6-11-501, Honjo, Sumida-ku, Tokyo, 130-0004, Japan   EMail: demizu@dd.iij4u.or.jp   Hiroshi Esaki   Computer Center, University of Tokyo,   2-11-16 Yayoi, Bunkyo-ku,   Tokyo, 113-8658, Japan   Phone: +81-3-3812-1111   EMail: hiroshi@wide.ad.jp   Yasuhiro Katsube   Computer & Network Development Center, Toshiba Corporation,   1, Toshiba-cho, Fuchu-shi,   Tokyo, 183-8511, Japan   Phone: +81-42-333-2844   EMail: yasuhiro.katsube@toshiba.co.jp   Paul Doolan   Ennovate Networks   60 Codman Hill Road   Boxborough, MA   Phone: 978-263-2002 x103   EMail: pdoolan@ennovatenetworks.comNagami, et al.              Standards Track                    [Page 18]

RFC 3038               VCID Notification for LDP            January 2001Full Copyright Statement   Copyright (C) The Internet Society (2001).  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.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Nagami, et al.              Standards Track                    [Page 19]