rfc2297.txt

RFC 的详细文档！

       29: Cannot support requested VPI range.

       30: Cannot support requested VCI range on all requested VPIs.

   The following failure response messages are only used by the Set
               Transmit Cell Rate function of the Port Management
               message.

       31: The transmit cell rate of this output port cannot be changed.



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       32: Requested transmit cell rate out of range for this output
               port.


4. Connection Management Messages

   Connection management messages are used by the controller to
   establish, delete, modify and verify virtual channel connections and
   virtual path connections across the switch. The Add Branch, Delete
   Tree, and Delete All connection management messages have the
   following format for both request and response messages:

    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                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |M|Q|B|C|      Input VPI        |          Input VCI            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Output Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |x x x x|      Output VPI       |          Output VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Number of Branches       |       Class of Service        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Input Port
             Identifies a switch input port.

   Flags

        M: Multicast
             The Multicast flag is used as a hint for point-to-
             multipoint connections in the Add Branch message. It is not
             used in any other connection management messages and in
             these messages it should be set to zero. If set, it
             indicates that the virtual channel connection or the
             virtual path connection is very likely to be a point-to-
             multipoint connection. If zero, it indicates that this
             connection is very likely to be a point-to-point connection
             or is unknown.




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             The Multicast flag is only used in the Add Branch message
             when establishing the first branch of a new connection. It
             is not required to be set when establishing subsequent
             branches of a point-to-multipoint connection and on such
             connections it should be ignored by the receiver. (On
             receipt of the second and subsequent Add Branch messages
             the receiver knows that this is a point-to-multipoint
             connection.) If it is known that this is the first branch
             of a point-to-multipoint connection this flag should be
             set. If it is unknown, or if it is known that the
             connection is point-to-point this flag should be zero. The
             use of this flag is not mandatory. It may be ignored by the
             switch.  If unused the flag should be set to zero. Some
             switches use a different data structure for point-to-
             multipoint connections than for point-to-point connections.
             This flag avoids the switch setting up a point-to-point
             structure for the first branch of a point-to-multipoint
             connection which must immediately be deleted and
             reconfigured as point-to-multipoint when the second branch
             is established.

        Q: QoS Profile
             The QoS Profile flag, if set, indicates that the Class of
             Service field contains a QoS Profile Identifier.  If this
             flag is zero, it indicates that the Class of Service field
             contains a Priority or a Scheduler Identifier.

        B: Bidirectional
             The Bidirectional flag applies only to the Add Branch
             message. In all other Connection Management messages it is
             not used. It may only be used when establishing a point-
             to-point connection.  The Bidirectional flag in an Add
             Branch message, if set, requests that two unidirectional
             virtual channels or virtual paths be established, one in
             the forward direction, and one in the reverse direction. It
             is equivalent to two Add Branch messages, one specifying
             the forward direction, and one specifying the reverse
             direction. The forward direction uses the values of Input
             Port, Input VPI, Input VCI, Output Port, Output VPI, and
             Output VCI as specified in the Add Branch message. The
             reverse direction is derived by exchanging the values
             specified in the Input Port, Input VPI, and Input VCI
             fields, with those of the Output Port, Output VPI, and
             Output VCI fields respectively. Thus, a virtual connection
             in the reverse direction arrives at the input port
             specified by the Output Port field, on the VPI/VCI
             specified by the Output VPI and Output VCI fields. It
             departs from the output port specified by the Input Port



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             field, on the VPI/VCI specified by the Input VPI and Input
             VCI fields.

             The Bidirectional flag is simply a convenience to establish
             two unidirectional virtual connections in opposite
             directions between the same two ports, with identical
             VPI/VCIs, using a single Add Branch message. In all future
             messages the two unidirectional virtual connections must be
             handled separately. There is no bidirectional delete
             message. However, a single Delete Branches message with two
             Delete Branch Elements, one for the forward connection and
             one for the reverse, may be used.

        C: Congestion Indication
             The Congestion Indication flag, if set, requests that cells
             on this connection be marked if congestion is experienced.
             If this connection passes through a queue that the switch
             considers to be congested, the Congestion Experienced bit
             will be set in the Payload Type field of the cell header of
             all cells on the connection. GSMP does not specify the
             algorithm or any threshold by which the switch decides when
             a queue is congested.

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

   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. For virtual path
             connections the Input VCI field is not used.

   Output Port
             Identifies a switch output port.

   x: Unused

   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. For
             virtual path connections the Output VCI field is not used.




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   Number of Branches
             In a success response message and a failure response
             message, gives the number of output branches on a virtual
             channel connection or a virtual path connection after
             completion of the requested operation.  (A point-to-point
             connection will have one branch, a point-to-multipoint
             connection will have two or more branches.) If the switch
             is unable to keep track of the number of branches on a
             virtual path connection or a virtual channel connection it
             must respond with the value 0xFFFF meaning: "number of
             branches unknown".  This field is not used in the request
             message.

   Class of Service
             This field can contain either a QoS Profile Identifier, a
             Priority, or a Scheduler Identifier.  If the QoS Profile
             flag in the Flags field is set, the Class of Service field
             contains a QoS Profile.  If the QoS Profile flag in the
             Flags field is zero, and the value of the Class of Service
             field is greater than or equal to 0x100, the Class of
             Service field contains a Scheduler Identifier.  If the QoS
             Profile flag in the Flags field is zero, and the value of
             the Class of Service field is less than 0x100, the Class of
             Service field contains a Priority. (Values of Scheduler
             Identifier less than 0x100 are interpreted as priorities.)
             The Class of Service field is only used in the Add Branch
             and Move Branch messages.

             A QoS Profile Identifier is an opaque 16-bit value. It is
             used to identify a QoS profile in the switch which
             specifies the Quality of Service required by the
             connection. QoS profiles are established by a mechanism
             external to GSMP.

             A Scheduler Identifier is an alternative method of
             communicating the QoS requirements of a connection. The
             Scheduler Identifier is defined in Section 9, "Quality of
             Service Messages."

             A Priority specifies the priority of the connection for Add
             Branch and Move Branch messages that choose not to use a
             QoS profile, or the QoS capabilities defined in Section 9,
             "Quality of Service Messages." 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



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             switch. It is assumed that for virtual path connections or
             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.

   For all connection management messages, except the Delete Branches
   message, the success response message is a copy of the request
   message returned with the Result field indicating success and the
   Number of Branches field indicating the number of branches on the
   connection after completion of the operation. The Code field is not
   used in a connection management success response message.

   The failure response message is a copy of the request message
   returned with a Result field indicating failure and the Number of
   Branches field indicating the number of branches on the connection.

   Fundamentally, no distinction is made between point-to-point and
   point-to-multipoint connections. By default, the first Add Branch
   message for a particular Input Port, Input VPI, and Input VCI will
   establish a point-to-point virtual connection.  The second Add Branch
   message with the same Input Port, Input VPI, and Input VCI fields
   will convert the connection to a point-to-multipoint virtual
   connection with two branches. (For virtual path connections the Input
   VCI is not required.) However, to avoid possible inefficiency with
   some switch designs, the Multicast Flag is provided. If the
   controller knows that a new connection is point-to-multipoint when
   establishing the first branch, it may indicate this in the Multicast
   Flag.  Subsequent Add Branch messages with the same Input Port, Input
   VPI, and Input VCI fields will add further branches to the point-to-
   multipoint connection. Use of the Delete Branch message on a point-