rfc1987.txt

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RFC 1987              GSMP Protocol Specification            August 1996


   synchronization, and all GSMP messages received on a link that does
   not currently have state synchronization must be discarded.

   All GSMP messages, except the adjacency protocol message, 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    | Message Type  |    Result     |     Code      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Transaction Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                          Message Body                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
             The GSMP protocol version number, currently Version = 1. It
             should be set by the sender of the message to the GSMP
             protocol version that the sender is currently running.

   Message Type
             The GSMP message type. GSMP messages fall into five
             classes: Connection Management, Port Management,
             Statistics, Configuration, and Events. Each class, except
             for port management, has a number of different message
             types. In addition, one Message Type is allocated to the
             adjacency protocol.

   Result
             Field in a connection management request message or a port
             management request message, is used to indicate whether a
             response is required to the request message if the outcome
             is successful. A value of "NoSuccessAck" indicates that the
             request message does not expect a response if the outcome
             is successful, and a value of "AckAll" indicates that a
             response is expected if the outcome is successful.  In both
             cases a failure response will be generated if the request
             fails. This facility reduces the traffic in the case where
             the controller is simply checking that the state in the
             switch is correct. For all other request messages a value
             of "NoSuccessAck" in the request message is ignored and the
             request message is handled as if the field were set to
             "AckAll".  In a response message the result field can have
             two values: "Success" and "Failure".




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RFC 1987              GSMP Protocol Specification            August 1996


             The encoding of the result field is:

                  NoSuccessAck:  Result = 1
                  AckAll:        Result = 2
                  Success:       Result = 3
                  Failure:       Result = 4.


             The Result field is not used in an adjacency protocol
             message and should be set to zero by the sender and ignored
             by the receiver.

   Code
             Field gives further information concerning the result in a
             response message. It is mostly used to pass an error code
             in a failure response but can also be used to give further
             information in a success response message or an event
             message. In a request message the code field is not used
             and is set to zero. In an adjacency protocol message the
             Code field is used to determine the function of the
             message.

   Transaction Identifier
             Used to associate a request message with its response
             message. For request messages the controller may select any
             transaction identifier. For response messages the
             transaction identifier is set to the value of the
             transaction identifier from the message to which it is a
             response.  For event messages the transaction identifier
             should be set to zero. In the adjacency protocol the
             Transaction Identifier is not used. This field is not
             present in the adjacency protocol message.


3. Connection Management Messages

   Connection management messages are used by the controller to
   establish, delete, modify and verify connections across the switch.
   The Add Branch, Delete Branch, Delete Tree, Verify Tree, and Delete
   All connection management messages have 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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Output Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |      Output VPI       |          Output VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Number of Branches       |   Reserved    |   Priority    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port Session Number
             Field gives the session number of the input port. Each
             switch port maintains a Port Session Number assigned by the
             switch. The port session number of a port remains unchanged
             while the port is continuously in the Available state and
             the link status is continuously Up. When a port returns to
             the Available state after it has been Unavailable or in any
             of the Loopback states, or when the line status returns to
             the Up state after it has been Down or in Test, or after a
             power cycle, a new Port Session Number must be generated.
             Port session numbers should be assigned using some form of
             random number.  The switch must reject any connection
             management request message that has an invalid Port Session
             Number for the port specified in the Input Port field by
             returning a failure response message with the Code field
             indicating, "Invalid port session number." The current port
             session number may be obtained using a configuration
             message.

   Input Port
             Indicates a switch input port.  Switch ports are referenced
             by a 32 bit value assigned by the switch.

   Input VPI
             Identifies an ATM virtual path arriving at the switch input
             port indicated by the Input Port field.





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RFC 1987              GSMP Protocol Specification            August 1996


   Input VCI
             Identifies an ATM virtual channel arriving on the virtual
             path indicated by the Input VPI field at the switch input
             port indicated by the Input Port field.

   Output Port
             Indicates a switch output port.  Switch ports are
             referenced by a 32 bit value assigned by the switch.

   Output VPI
             Identifies an outgoing virtual path departing from the
             switch output port indicated in the Output Port field.

   Output VCI
             Identifies an outgoing virtual channel departing on the
             virtual path indicated by the Output VPI field from the
             switch output port indicated in the Output Port field.

   Number of Branches
             Gives the number of output branches on a virtual channel
             connection. (A unicast connection will have one branch, a
             multicast connection will have two or more branches.) This
             field is only used in the Verify Tree message.  In all
             other connection management messages this field should be
             set to zero by the sender and ignored by the receiver.

   Reserved
             This field is not used. It is set to zero by the sender and
             ignored by the receiver.

   Priority
             Gives the priority of the connection.  The highest priority
             is numbered zero and the lowest priority is numbered "Q-1"
             where "Q" is the number of priorities that the output port
             can support. The ability to offer different qualities of
             service to different connections based upon their priority
             is assumed to be a property of the output port of the
             switch. It is assumed that for virtual channel connections
             that share the same output port, an ATM cell on a
             connection with a higher priority is much more likely to
             exit the switch before an ATM cell on a connection with a
             lower priority if they are both in the switch at the same
             time. The number of priorities that each output port can
             support is given in the Port Configuration message. If a
             connection request is received with a value in the priority
             field that the switch cannot support, the switch will
             assign the closest priority that it is capable of
             supporting.  This field is only used in the Add Branch and



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RFC 1987              GSMP Protocol Specification            August 1996


             Move Branch messages.  In all other connection management
             messages this field should be set to zero by the sender and
             ignored by the receiver.

   If the result field of the request message is "AckAll" the switch
   must reply to all connection management request messages with a
   success response message or a failure response message.  If the
   result field of the request message is "NoSuccessAck" the switch must
   only reply in the case of a failure.

   A success response message must not be sent until the operation has
   been successfully completed. For connection management messages the
   success response message is a copy of the request message returned
   with a Result field indicating success. The Code field is not used in
   a connection management success response message and should be set to
   zero. The failure response message is a copy of the request message
   returned with a Result field indicating failure. The Code field is
   used to pass the Failure Code in a connection management failure
   response message. If the switch issues a failure response the
   connection state within the switch must not be modified by the
   request message that resulted in the failure.

   No distinction is made between unicast connections and multicast
   connections. The first Add Branch message for a particular Input
   Port, Input VPI, and Input VCI will establish a unicast connection.
   The second Add Branch message with the same Input Port, Input VPI,
   and Input VCI fields will convert the connection to a multicast
   connection with two branches. Subsequent Add Branch messages with the
   same Input Port, Input VPI, and Input VCI fields will add further
   branches to the multicast connection. Use of the Delete Branch
   message on a multicast connection with two branches will result in a
   unicast connection. Use of the Delete Branch message on a unicast
   connection will delete the unicast connection. There is no concept of
   a connection with zero output branches. All connections are
   unidirectional, one input virtual channel to one or more output
   virtual channels.

   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.