rfc1987.txt

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Newman, et. al.              Informational                     [Page 10]

RFC 1987              GSMP Protocol Specification            August 1996


3.1 Add Branch Message

   The Add Branch message is a connection management message used to
   establish a virtual channel connection or to add an additional branch
   to an existing virtual channel connection. It may also be used to
   check the connection state stored in the switch. The connection is
   specified by the Input Port, Input VPI, and Input VCI fields. The
   output branch is specified by the Output Port, Output VPI, and Output
   VCI fields. The priority of the connection is specified by the
   Priority field. The Add Branch message is:

      Message Type = 16

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields does not already exist, it must be
   established with the single output branch specified in the request
   message. The output branch should have the priority specified by the
   Priority field. If the Result field of the request message is
   "AckAll" a success response message must be sent upon successful
   establishment of the specified branch.  The success response message
   must not be sent until the Add Branch operation has been completed.

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields already exists, but the specified output
   branch does not, the new output branch must be added. The new output
   branch should have the priority specified by the Priority field. If
   the Result field of the request message is "AckAll" a success
   response message must be sent upon successful establishment of the
   specified branch. The success response message must not be sent until
   the Add Branch operation has been completed.

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields already exists and the specified output
   branch also already exists, the priority of the connection, if
   different from the request message, should be changed to that in the
   request message. A success response message must be sent if the
   Result field of the request message is "AckAll".  This allows the
   controller to periodically reassert the state of a connection or to
   change its priority. If the result field of the request message is
   "NoSuccessAck" a success response message should not be returned.
   This may be used to reduce the traffic on the control link for
   messages that are reasserting previously established state. For
   messages that are reasserting previously established state, the
   switch must always check that this state is correctly established in
   the switch hardware (i.e. the actual connection tables used to
   forward cells).





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RFC 1987              GSMP Protocol Specification            August 1996


   The behavior is undefined if the output virtual channel specified by
   the Output Port, Output VPI, and Output VCI fields is already in use
   by any connection other than that specified by the Input Port, Input
   VPI, and Input VCI fields.

   A failure response must be returned if the switch is unable to
   establish the specified branch or if there is an error in any of the
   fields of the request message. If a failure message is returned the
   state of the switch must not have been modified by the request
   message.

   It should be noted that different switches support multicast in
   different ways. There will be a limit to the total number of
   multicast connections any switch can support, and possibly a limit on
   the maximum number of branches that a multicast connection may
   specify.  Some switches also impose a limit on the number of
   different VPI/VCI values that may be assigned to the output branches
   of a multicast connection. Many switches are incapable of supporting
   more than a single branch of any particular multicast connection on
   the same output port. Specific failure codes are defined for some of
   these conditions. If a switch sends a failure response to an Add
   Branch message it must choose the most specific failure code.

3.2 Delete Branch Message

   The Delete Branch message is a connection management message used to
   delete a single branch of a virtual channel connection, or in the
   case of the last branch, to delete the connection. The virtual
   channel connection is specified by the Input Port, Input VPI, and
   Input VCI fields. The specific branch is indicated by the Output
   Port, Output VPI, and Output VCI fields. The Delete Branch message
   is:

      Message Type = 17

   If the Result field of the request message is "AckAll" a success
   response message must be sent upon successful deletion of the
   specified branch. The success response message must not be sent until
   the delete branch operation has been completed and if possible, not
   until all data on that branch, queued for transmission, has been
   transmitted. A failure message indicating, "The specified connection
   does not exist," must be sent if the connection specified by the
   Input Port, Input VPI, and Input VCI fields does not exist. A failure
   message indicating, "The specified branch does not exist," must be
   sent if the connection specified by the Input Port, Input VPI, and
   Input VCI fields exists but the branch specified by the Output Port,
   Output VPI, and Output VCI fields does not exist.




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RFC 1987              GSMP Protocol Specification            August 1996


3.3 Delete Tree Message

   The Delete Tree message is a connection management message used to
   delete an entire virtual channel connection. All remaining branches
   of the connection are deleted. The virtual channel connection is
   specified by the Input Port, Input VPI, and Input VCI fields.  The
   Output Port, Output VPI, and Output VCI fields are not used in this
   message and their contents should be set to zero by the sender and
   ignored by the receiver. The Delete Tree message is:

      Message Type = 18

   If the Result field of the request message is "AckAll" a success
   response message must be sent upon successful deletion of the
   specified connection. The success message must not be sent until the
   delete operation has been completed and if possible, not until all
   data on the connection, queued for transmission, has been
   transmitted. A failure message indicating, "The specified connection
   does not exist," must be sent if the connection specified by the
   Input Port, Input VPI, and Input VCI fields does not exist.

3.4 Verify Tree Message

   The Verify Tree message is a connection management message used to
   verify the number of branches on a virtual channel connection.  The
   virtual channel connection is specified by the Input Port, Input VPI,
   and Input VCI fields. The Output Port, Output VPI, and Output VCI
   fields are not used in this message and their contents should be set
   to zero by the sender and ignored by the receiver.  The number of
   branches that the sender believes that this virtual channel
   connection should contain is given by the Number of Branches field.
   The Verify Tree message is:

      Message Type = 19

   If the Result field of the request message is "AckAll" a success
   response message must be sent if the receiver agrees that the actual
   number of branches of the specified virtual channel connection
   matches the number contained in the Number of Branches field of the
   request message. The failure response message, with the code field
   set to "Failure specific to the particular message type," must be
   sent if the actual number of branches of the specified virtual
   channel connection does not match the number contained in the Number
   of Branches field of the request message. In this failure response
   message the Number of Branches field must be changed to contain the
   actual number of branches of the specified virtual channel
   connection. A failure response message with the code field set to a
   different value must be used to indicate some other failure such as,



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RFC 1987              GSMP Protocol Specification            August 1996


   "The specified connection does not exist." In this case the Number of
   Branches field will be the same as that of the request message.

   The Verify Tree message can only be guaranteed to yield a correct
   response when there are no other connection request messages or their
   response messages pending for the specified connection.  If this is
   not the case the result of the Verify Tree message is undefined.

3.5 Delete All Message

   The Delete All message is a connection management message used to
   delete all connections on a switch input port. All connections that
   arrive at the specified input port must be deleted. On completion of
   the operation all dynamically assigned VPI/VCI values for the
   specified port must be unassigned, i.e. there must be no virtual
   connections established in the VPI/VCI space that GSMP controls on
   this port. The Input VPI, Input VCI, Output Port, Output VPI, and
   Output VCI fields are not used in this message and their contents are
   ignored and unspecified. The Delete All message is"

      Message Type = 20

   If the Result field of the request message is "AckAll" a success
   response message must be sent upon completion of the operation. The
   success response message must not be sent until the operation has
   been completed.


3.6 Move Branch Message

   The Move Branch connection management message has the following
   format for both request and response messages:



















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RFC 1987              GSMP Protocol Specification            August 1996


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    | Message Type  |    Result     |     Code      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Transaction Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Input Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |        Input VPI      |           Input VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Old Output Port                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |    Old Output VPI     |        Old Output VCI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        New Output Port                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |    New Output VPI     |        New Output VCI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Reserved                   |   Priority    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Move Branch message is a connection management message used to
   move a single output branch of a virtual channel connection from its
   current output port, output VPI, and output VCI, to a new output
   port, output VPI, and output VCI on the same virtual channel
   connection. None of the other output branches are modified.  When the
   operation is complete the original output VPI/VCI on the original
   output port will be deleted from the connection.  The Move Branch
   message is:

      Message Type = 22

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields already exists, and the output branch
   specified by the Old Output Port, Old Output VPI, and Old Output VCI
   fields exists as a branch on that connection, the output branch
   specified by the New Output Port, New Output VPI, and New Output VCI
   fields is added to the connection and the branch specified by the Old
   Output Port, Old Output VPI, and Old Output VCI fields is deleted. If
   the Result field of the request message is "AckAll" a success
   response message must be sent upon successful completion of the
   operation. The success response message must not be sent until the
   Move Branch operation has been completed.