rfc2297.txt

RFC 的详细文档！

   to-multipoint connection with two branches will result in a point-
   to-point connection. However, the switch may structure this
   connection as a point-to-multipoint connection with a single output
   branch if it chooses. (For some switch designs this structure may be
   more convenient.) Use of the Delete Branch message on a point-to-
   point connection will delete the point-to-point connection. There is
   no concept of a connection with zero output branches. All connections
   are unidirectional, one input virtual path or virtual channel to one
   or more output virtual paths or virtual channels.

   GSMP supports point-to-point and point-to-multipoint connections. A
   multipoint-to-point connection is specified by establishing multiple
   point-to-point connections each of them specifying the same output
   branch.  (An output branch is specified by an output port and output



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   VPI for a virtual path connection and by an output port, output VPI,
   and output VCI for a virtual channel connection.) A multipoint-to-
   multipoint connection is specified by establishing multiple point-
   to-multipoint trees each of them specifying the same output branches.

   The connection management messages apply both to virtual channel
   connections and virtual path connections. The Add Branch and Move
   Branch connection management messages have two Message Types. One
   Message Type indicates that a virtual channel connection is required,
   and the other Message Type indicates that a virtual path connection
   is required. The Delete Branches, Delete Tree, and Delete All
   connection management messages have only a single Message Type
   because they do not need to distinguish between virtual channel
   connections and virtual path connections. For virtual path
   connections, neither Input VCI fields nor Output VCI fields are
   required. They should be set to zero by the sender and ignored by the
   receiver. Virtual channel branches may not be added to an existing
   virtual path connection.  Conversely, virtual path branches may not
   be added to an existing virtual channel connection.  In the Port
   Configuration message each switch input port may declare whether it
   is capable of supporting virtual path switching (i.e. accepting
   connection management messages requesting virtual path connections).

   The connection management messages may be issued regardless of the
   Port Status of the switch port. Connections may be established or
   deleted when a switch port is in the Available, Unavailable, or any
   of the Loopback states. However, all connection state on an input
   port will be deleted when the port returns to the Available state
   from any other state, i.e. when a Port Management message is received
   for that port with the Function field indicating either Bring Up, or
   Reset Input Port.

4.1 Add Branch Message

   The Add Branch message is a connection management message used to
   establish a virtual channel connection or a virtual path connection
   or to add an additional branch to an existing virtual channel
   connection or virtual path 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 quality of service requirements of the connection are
   specified by the Class of Service field. To request a virtual channel
   connection the Virtual Channel Connection (VCC) Add Branch message
   is:

      Message Type = 16




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   To request a virtual path connection the Virtual Path Connection
   (VPC) Add Branch message is:

      Message Type = 26

   If a VPC Add Branch message is received and the switch input port
   specified by the Input Port field does not support virtual path
   switching, a failure response message must be returned indicating,
   "Virtual path switching is not supported on this input port."

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields; or the virtual path connection specified
   by the Input Port and Input VPI fields; does not already exist, it
   must be established with the single output branch specified in the
   request message. If the Bidirectional Flag in the Flags field is set,
   the reverse connection must also be established.  The output branch
   should have the QoS attributes specified by the Class of Service
   field.

   For the VCC Add Branch message, if a virtual path connection already
   exists on the virtual path specified by the Input Port and Input VPI
   fields, a failure response message must be returned indicating,
   "Attempt to add a virtual channel connection branch to an existing
   virtual path connection." For the VPC Add Branch message, if a
   virtual channel connection already exists on any of the virtual
   channels within the virtual path specified by the Input Port and
   Input VPI fields, a failure response message must be returned
   indicating, "Attempt to add a virtual path connection branch to an
   existing virtual channel connection."

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields; or the virtual path connection specified
   by the Input Port and Input VPI fields; already exists, but the
   specified output branch does not, the new output branch must be
   added.  The new output branch should have the QoS attributes
   specified by the Class of Service field.

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields; or the virtual path connection specified
   by the Input Port and Input VPI fields; already exists and the
   specified output branch also already exists, the QoS attributes of
   the connection, specified by the Class of Service field, 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.



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   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).

   If the output branch specified by the Output Port, Output VPI, and
   Output VCI fields for a virtual channel connection; or the output
   branch specified by the Output Port and Output VPI fields for a
   virtual path connection; is already in use by any connection other
   than that specified by the Input Port, Input VPI, and Input VCI
   fields, then the resulting output branch will have multiple input
   branches. If multiple point-to-point connections share the same
   output branch the result will be a multipoint-to-point connection. If
   multiple point-to-multipoint trees share the same output branches the
   result will be a multipoint-to-multipoint connection.

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields, or the virtual path connection specified
   by the Input Port and Input VPI fields, already exists, and the
   Bidirectional Flag in the Flags field is set, a failure response must
   be returned indicating: "Only point-to-point bidirectional
   connections may be established."

   It should be noted that different switches support multicast in
   different ways. There will be a limit to the total number of point-
   to-multipoint connections any switch can support, and possibly a
   limit on the maximum number of branches that a point-to-multipoint
   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 point-to-multipoint connection. Many switches are
   incapable of supporting more than a single branch of any particular
   point-to-multipoint connection on the same output port. Specific
   failure codes are defined for some of these conditions.

4.2 Delete Tree Message

   The Delete Tree message is a connection management message used to
   delete an entire virtual channel connection or an entire virtual path
   connection. All remaining branches of the connection are deleted. A
   virtual channel connection is specified by the Input Port, Input VPI,
   and Input VCI fields. A virtual path connection is specified by the
   Input Port and Input VPI fields. The Output Port, Output VPI, and
   Output VCI fields are not used in this message. The Delete Tree
   message is:

      Message Type = 18



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   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. The Number of Branches field is not used in either the
   request or response messages of the Delete Tree message.

4.3 Verify Tree Message

   The Verify Tree message has been removed from this version of GSMP.
   Its function has been replaced by the Number of Branches field in the
   success response to the Add Branch message which contains the number
   of branches on a virtual channel connection after successful
   completion of an add branch operation.

      Message Type = 19 is reserved.

   If a request message is received with Message Type = 19 a failure
   response must be returned with the Code field indicating: "The
   specified request is not implemented in this version of the
   protocol."

4.4 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.  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
   Number of Branches field is not used in either the request or
   response messages of the Delete All message.  The success response
   message must not be sent until the operation has been completed.

   The following failure response messages may be returned to a Delete
   All request.

         The specified request is not implemented on this switch.




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         One or more of the specified ports does not exist.

         Invalid Port Session Number.

   If any field in a Delete All message not covered by the above failure
   codes is invalid, a failure response must be returned indicating:
   "Invalid request message." Else, the delete all operation must be
   completed successfully and a success message returned. No other
   failure messages are permitted.

4.5 Delete Branches Message

   The Delete Branches message is a connection management message used
   to request one or more delete branch operations. Each delete branch
   operation deletes a branch of a virtual channel connection or a
   virtual path connection, or in the case of the last branch of a
   connection, it deletes the connection. The Delete Branches message
   is:

      Message Type = 17

   The request message has 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
   +-+-+-+-+-+-+-+-