rfc3038.txt

最新的RFC

         |                |
         |<---------------|     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.










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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.






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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 Mapping

4 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.






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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 Format

5.1 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            = 0x0507

5.1.1 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 LDP



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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).



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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.













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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