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RFC 2297

 
 
 

Ipsilon's General Switch Management Protocol Specification Version 2.0

Part 3 of 4, p. 59 to 86
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8. Event Messages

   Event messages allow the switch to inform the controller of certain
   asynchronous events. Event messages are not acknowledged. The Result
   field and the Code field in the message header are not used and
   should be set to zero. Event messages are not sent during
   initialization. Event messages 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Port                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Event Sequence Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |          VPI          |              VCI              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Event Sequence Number
             The current value of the Event Sequence Number for the
             specified port. The Event Sequence Number is set to zero
             when the port is initialized. It is incremented by one each
             time the port detects an asynchronous event that the switch
             would normally report via an Event message. The Event
             Sequence Number must be incremented each time an event
             occurs even if the switch is prevented from sending an
             Event message due to the action of the flow control.

   VPI/VCI
             Field gives the VPI/VCI to which the event message refers.
             If this field is not required by the event message it is
             set to zero.

   Each switch port must maintain an Event Sequence Number and a set of
   Event Flags, one Event Flag for each type of Event message.  When a
   switch port sends an Event message it must set the Event Flag on that
   port corresponding to the type of the event. The port is not
   permitted to send another Event message of the same type until the
   Event Flag has been reset. Event Flags are reset by the "Reset Event
   Flags" function of the Port Management message. This is a simple flow
   control preventing the switch from flooding the controller with event
   messages. The Event Sequence Number of the port must be incremented
   every time an event is detected on that port even if the port is
   prevented from reporting the event due to the action of the flow
   control. This allows the controller to detect that it has not been
   informed of some events that have occurred on the port due to the
   action of the flow control.

8.1 Port Up Message

   The Port Up message informs the controller that the Line Status of a
   port has changed from either the Down or Test state to the Up state.
   When the Line Status of a switch port changes to the Up state from
   either the Down or Test state a new Port Session Number must be
   generated, preferably using some form of random number. The new Port
   Session Number is given in the Port Session Number field. The VPI/VCI
   field is not used and is set to zero.  The Port Up message is:

      Message Type = 80

8.2 Port Down Message

   The Port Down message informs the controller that the Line Status of
   a port has changed from the Up state to the Down state. This message
   will be sent to report link failure if the switch is capable of
   detecting link failure. The port session number that was valid before

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   the port went down is reported in the Port Session Number field. The
   VPI/VCI field is not used and is set to zero. The Port Down message
   is:

      Message Type = 81

8.3 Invalid VPI/VCI Message

   The Invalid VPI/VCI message is sent to inform the controller that one
   or more cells have arrived at an input port with a VPI/VCI that is
   currently not allocated to an assigned connection. The input port is
   indicated in the Port field, and the VPI/VCI in the VPI/VCI field.
   The Invalid VPI/VCI message is:

      Message Type = 82

8.4 New Port Message

   The New Port message informs the controller that a new port has been
   added to the switch. The port number of the new port is given in the
   Port field. A new Port Session Number must be assigned, preferably
   using some form of random number.  The new Port Session Number is
   given in the Port Session Number field.  The state of the new port is
   undefined so the VPI/VCI field is not used and is set to zero.  The
   New Port message is:

      Message Type = 83

8.5 Dead Port Message

   The Dead Port message informs the controller that a port has been
   removed from the switch. The port number of the port is given in the
   Port field. The Port Session Number that was valid before the port
   was removed is reported in the Port Session Number field.  The
   VPI/VCI fields are not used and are set to zero. The Dead Port
   message is:

      Message Type = 84


9. Quality of Service Messages

   The GSMP Quality of Service (QoS) messages allow a controller to
   group virtual path connections and virtual channel connections into
   QoS classes, and to allocate QoS resources to both QoS classes and to
   individual connections. At initialization, the switch describes its
   QoS capabilities to the controller, in terms of the abstract switch
   model, using the QoS Configuration message. The controller issues

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   Scheduler Establishment messages to configure the scheduler on each
   switch output port. It also issues QoS Class Establishment messages
   to configure QoS classes. Connections may be added to, or deleted
   from, a QoS class using the QoS Connection Management message. QoS
   resources may also be assigned to individual connections using the
   QoS Connection Management message. Connections that only require the
   scheduler may use the simple connection management messages defined
   in Section 3, "Connection Management Messages."

9.1 Abstract Switch Model

   The abstract switch model, fig. 1, is the means by which a switch can
   describe its fundamental QoS capabilities to a controller. It
   consists of four main functions: a policer, a classifier, a
   regulator, and a scheduler.  The classifier groups multiple
   connections (VPCs or VCCs) together into a QoS class such that QoS
   resources may be shared by the QoS class as a whole. Within a QoS
   class there is no differentiation between members of the class in
   terms of QoS resources received. However, the ordering of cells
   within each constituent VPC or VCC must be preserved on exit from the
   switch. Connections are not required to be aggregated into a QoS
   class with other connections; they may be allocated individual QoS
   resources.

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   VPC/VCCs  Policer  Classifier   Regulator       Scheduler

             +--+     +----+                       +--------+
    -------->|  |---->|    |                       |        |
             +--+     |    |                       |        |
                      |    |                       |        |
             +--+     |    |       +----+          |        |
    -------->|  |---->|    |       |    |--------->|        |
             +--+     |    |       |    |conforming|        |
                      |    |------>|    |          |        |
             +--+     |    |  QoS  |    |          |        |
    -------->|  |---->|    | Class |    |--------->|        |
             +--+     |    |       +----+  excess  |        |
                      |    |                       |        |
             +--+     |    |                       |        |
    -------->|  |---->|    |                       |        |
             +--+     +----+                       |        |
                                                   |        |
                                                   |        |   Output
                                                   |        |    Port
                                                   |        |---------->
                                                   |        |
                                                   |        |
             +--+     +----+                       |        |
    -------->|  |---->|    |                       |        |
             +--+     |    |                       |        |
                      |    |                       |        |
             +--+     |    |       +----+          |        |
    -------->|  |---->|    |       |    |--------->|        |
             +--+     |    |       |    |conforming|        |
                      |    |------>|    |          |        |
             +--+     |    |  QoS  |    |          |        |
    -------->|  |---->|    | Class |    |--------->|        |
             +--+     |    |       +----+  excess  |        |
                      |    |                       |        |
             +--+     |    |                       |        |
    -------->|  |---->|    |                       |        |
             +--+     +----+                       |        |
                                                   +--------+

                       Fig. 1: Abstract Switch Model

   The policer is a single input, single output device that can discard
   or tag cells.  A policer may be applied to police each individual
   connection.  A policer may also be applied to police the aggregate
   traffic of a QoS class.  The policer is  used to enforce an upper
   bound on the traffic on a connection or on a QoS class.

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   The regulator follows the policer and classifier. It offers either a
   policing function or a shaping function. The policing function
   evaluates cells as conforming to the rate specified by the regulator
   parameters or as being in excess of that rate. One of three actions
   can be specified to be taken for each cell as a result of this
   evaluation: tagging, discard or differentiated scheduling. Tagging
   sets the CLP bit of cells deemed to be in excess of the rate defined
   by the regulator parameters.  The discard function discards excess
   cells. The differentiated scheduling function allows conforming cells
   and excess cells to be scheduled for service at different points in
   the scheduler. This would allow conforming cells, for example, to
   receive service with a QoS guarantee, whereas excess cells receive
   best-effort service.  The implementation of differentiated
   scheduling, however, is complicated by the requirement not to reorder
   cells within each connection.

   The shaping function of the regulator paces cells out, on each QoS
   class or individual connection, at the rate specified by the
   regulator parameters. No jitter requirement may be specified, nor is
   any specific guarantee of jitter given. If traffic arrives on any QoS
   class or individual connection at a greater rate than the output rate
   specified, that traffic will be delayed. If the delayed traffic for
   any QoS class or individual connection exceeds a bound, discard will
   occur.  Differentiated scheduling is supported by the shaper but its
   application to shaping is somewhat different than its application to
   policing. Conforming traffic is that traffic which leaves the shaper
   as a result of the shaping process.  The conforming pointer specifies
   the point in the scheduler structure where such traffic is scheduled
   for output. (This is typically the highest priority of the scheduler
   but the GSMP specification permits other priorities to be specified.)
   If an excess pointer is also enabled for a particular QoS class or
   individual connection, traffic in excess of the rate specified by the
   shaper may also be transmitted.  The position of the excess pointer
   in the scheduler structure determines the undefined amount of
   additional traffic that will be supported. The excess traffic may be
   tagged if required, if tagging is supported. The excess pointer will
   receive the same share of bandwidth that a best-effort class or
   connection would receive at the same location in the scheduler
   structure.

   The location of the classifier and regulator functions in the switch
   is important. If the classifier is located on an input port, only
   virtual connections that arrive at that input port may be aggregated
   into a QoS class. If the classifier is centralized, or located on an
   output port, virtual connections that arrive at any input port may be
   aggregated into the same QoS class. If the regulator is located on an
   output port all virtual connections within a QoS class passing
   through that regulator must exit the switch at that output port.

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   However, if the regulator is centralized, or located on an input
   port, virtual connections that are part of the same QoS class may be
   switched to different output ports.  Each switch port must specify
   the location of its classifier and regulator functions.

   The scheduler is located on the output port, fig. 2. It distributes
   the bandwidth of the output link between the QoS classes and
   individual connections.  It is a two-level scheduler: a priority
   scheduler at one level and a FIFO or a weighted scheduler at the
   other.  Up to 255 strict priority levels may be supported. Traffic in
   any specific priority level may only be transmitted if no traffic is
   queued for transmission in any higher priority level. Within each
   priority level a weighted scheduler may be defined. Each leaf of the
   scheduler tree is connected to a waiting room. The waiting room has
   two functions. When it receives service from the scheduler, it must
   select a QoS class or individual connection for transmission. When it
   is notified of traffic arrival on a QoS class or connection, it must
   decide whether there is enough room left in the waiting room to
   accept the traffic, else that traffic must be discarded. The waiting
   room has a size parameter indicating how much traffic may be
   accepted.  Other queueing parameters may be attached to the waiting
   room. Multiple conforming and excess pointers from the regulators may
   point to each waiting room. Within a waiting room, the scheduling of
   multiple connections sharing that waiting room may support weighted
   sharing between the connections.

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        From      Waiting        FIFO/Weighted        Priority
      Regulator     Room           Scheduler          Scheduler

                           Net       +---+
                  +------+ Weight    |   |
       ---------->|      |-%-------->| 0 |------\
                  +------+           |   |       \
                                     +---+        \
       ---------->+------+                        |
                  |      |-%--\      +---+        |
       ---------->+------+     \---->|   |        |
                                     | 1 |---\    |
                  +------+     /---->|   |    \   \
       ---------->|      |-%--/      +---+     \   \    +---+
                  +------+                      \   \-->|   |
                                                 \----->|   |--------->
       ---------->+------+                          /-->|   |  Output
       ---------->|      |-%-\                     /    +---+   Port
       ---------->+------+    \                   /
                               \     +---+       /
                  +------+      \--->|   |      /
       ---------->|      |-%-------->| 2 |-----/
                  +------+      /--->|   |
                               /     +---+
                  +------+    /
       ---------->|      |-%-/
                  +------+

                           Fig. 2: The Scheduler

9.2 QoS Configuration Message

   The QoS Configuration message permits the controller to discover the
   QoS capabilities of each switch port in terms of the abstract switch
   model. The QoS Configuration message is:

      Message Type = 96


   The QoS Configuration request message has the following format:

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    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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The QoS Configuration success response 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    | Message Type  |    Result     |     Code      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Transaction Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Port                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Port Session Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Scheduler Flags        |       Regulator Flags         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Excess Capabilities      |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Hi Sharing   |  Lo Sharing   |          Max Classes          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Default Size                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Default Discard Threshold                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Max Buffer                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Max Shaper Buffer                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Scaling Factor                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port
             The switch port to which the QoS configuration information
             refers. QoS configuration information relating to both the
             input and the output sides of the switch port is given.

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   Scheduler Flags

         0                   1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |W|Q|S|G|D|F|M|B|I|x x x x x x x|
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        W: Weighted Connections
             Bit 0 of the Scheduler Flags field, if set, indicates that
             a weighted service algorithm (such as weighted round-robin)
             is available for allocation of service to individual
             connections within at least some waiting rooms. It means
             that a Connection Weight parameter can be attached to a QoS
             Connection Management message. Not all waiting rooms at all
             priority levels may be able to support this function.
             Whether a particular waiting room can support this function
             will be discovered when a QoS Connection Management message
             is issued.

        Q: Weighted QoS Classes
             Bit 1 of the Scheduler Flags field, if set, indicates that
             a weighted service algorithm (such as weighted round-robin)
             is available for allocation of service to QoS classes
             within at least some waiting rooms.  It means that a QoS
             Class Weight parameter can be attached to a QoS Class
             Establishment message.  Not all waiting rooms at all
             priority levels may be able to support this function.
             Whether a particular waiting room can support this function
             will be discovered when a QoS Class Establishment message
             is issued.

        S: Shared Waiting Room
             Bit 2 of the Scheduler Flags field, if set, indicates that
             multiple QoS classes and multiple connections may be
             scheduled within a single waiting room. This is expected to
             be the normal case. If Bit 2 of the Scheduler Flags field
             is zero, it indicates that only a single QoS class or a
             single connection may be directed to any single waiting
             room.

        G: Global Max Classes
             Bit 3 of the Scheduler Flags field, if set, indicates that
             the Max Classes field gives the maximum number of QoS
             classes that may be supported by the entire switch. If
             zero, it indicates that the Max Classes field gives the
             maximum number of QoS classes that may be supported by this
             switch port.

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        D: Packet Discard
             Bit 4 of the Scheduler Flags field, if set, indicates that
             the scheduler on this output port is capable of packet
             discard. Packet discard indicates a discard algorithm that
             is aware of AAL-5 packet boundaries and attempts to discard
             whole packets. No specific algorithm is indicated though
             Early Packet Discard (EPD) is likely to be the most common.
             Other algorithms such as "push from front" schemes, dynamic
             threshold, or Random Early Detection (RED) are also
             examples of possible packet discard algorithms. The only
             parameters available to the packet discard algorithm, via
             GSMP, are the Size and Discard Threshold of the waiting
             room.

        F: Frame-Based Scheduling
             Bit 5 of the Scheduler Flags field, if set, indicates that
             the scheduler on this output port is capable of frame-based
             scheduling. In frame-based scheduling, a connection is only
             scheduled for transmission when a complete AAL-5 packet is
             available.  When a connection is scheduled for
             transmission, all cells belonging to one or more complete
             packets from that connection will be transmitted without
             being interleaved with any other cells on that output port
             (regardless of their priority).  Frame-based scheduling is
             a property of the waiting room and is requested in the
             Scheduler Establishment message.  A QoS class may be routed
             through a waiting room configured with frame-based
             scheduling.  In this case each component connection of the
             QoS class will receive frame based scheduling. For correct
             distribution of bandwidth, each QoS class that requires
             frame-based scheduling should have its own waiting room.

        M: VC Merging
             Bit 6 of the Scheduler Flags field, if set, indicates that
             the scheduler on this output port is capable of VC merging
             by a mechanism other than frame-based scheduling. VC
             merging indicates that the switch is capable of the
             multipoint-to-point merging of two or more incoming virtual
             connections onto a single outgoing virtual connection
             without interleaving cells from different AAL-5 packets
             that bear the same VPI/VCI. VC merging differs from frame-
             based scheduling in that cells with a different VPI/VCI may
             be interleaved with those of a multipoint-to-point VC
             merging connection. Thus, higher priority cells may be
             interleaved during the transmission of a packet on a lower
             priority VC merging connection.  Most switches achieve VC
             merging by using frame-based scheduling.  VC merging is a
             property of the waiting room and is requested in the

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             Scheduler Establishment message.  A QoS class may be routed
             through a waiting room configured with VC merging.  In this
             case each component connection of the QoS class will
             receive VC merging.

        B: Shared Buffer
             Bit 7 of the Scheduler Flags field, if set, indicates that
             at least some of the buffer space specified by the Max
             Buffer field is shared with other ports.  If zero, it
             indicates that the buffer space specified by the Max Buffer
             field is not shared with other ports.

        I: Identical Ports
             Bit 8 of the Scheduler Flags field, if set, indicates that
             all ports of the switch have identical QoS capabilities. If
             this bit is set the controller does not have to request the
             QoS configuration of each port individually as all ports
             have the same capability.

        x: Bits 9--15 of the Scheduler Flags field are not used.

   Regulator Flags

         0                   1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |C|Q|I O|P|S|H|M|x x x x x x x x|
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        C: Connection Policing
             Bit 0 of the Regulator Flags field indicates that this
             input port supports the policing of individual incoming
             connections. The parameters for the policer are specified
             in the QoS Connection Management message when the
             connection is established.

        Q: QoS Class Policing
             If bit 1 of the Regulator Flags field is set, a policer
             function is available to police each QoS class on output
             from the classifier. The parameters for this policer are
             specified in the QoS Class Establishment message. If this
             bit is zero, no policer function is available to police a
             QoS class.

        IO: QoS Class Location
             Bits 2 and 3 of the Regulator Flags field specify the
             location of the classifier and regulator functions. If both

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             bits 2 and 3 of the Regulator Flags field are zero, no
             classifier or regulator function is available to this port.

             If bit 2 of the Regulator Flags field is set and bit 3 is
             zero, the classifier and regulator functions are available
             on the input port. This implies that only virtual
             connections arriving at this input port may be grouped into
             QoS classes by this classifier. However, connections in a
             QoS class output from this regulator may be switched to any
             output port.

             If bit 2 of the Regulator Flags field is zero and bit 3 is
             set, the classifier and regulator functions are available
             on the output port. This implies that virtual connections
             arriving at any input port may be grouped into QoS classes
             by this classifier. However, all connections in any QoS
             class output from this regulator may only be switched to
             this output port.

             If both bits 2 and 3 of the Regulator Flags field are set,
             this switch port has access to centralized classifier and
             regulator functions. This implies that virtual connections
             arriving at any input port may be grouped into a QoS class
             by this classifier. Also, connections in a QoS class output
             from this regulator may be switched to any output port.

        Regulator Function

        P: If bit 4 of the Regulator Flags field is set, the regulator
             is able to support the policing function.

        S: If bit 5 of the Regulator Flags field is set, the regulator
             is able to support the shaping function on all priority
             levels of the scheduler.

        H: If bit 5 of the Regulator Flags field is zero and bit 6 is
             set, the regulator is able to support the shaping function
             but only on the highest priority level of the scheduler.
             All connections and QoS classes using this regulator must
             be routed to a waiting room at the highest priority level
             of the scheduler.

        M: QoS Multicast
             If bit 7 of the Regulator Flags field is set, any point-
             to-multipoint connection arriving on this input port, with
             QoS parameters established by the GSMP Quality of Service
             messages, must use the same QoS parameters for all output
             branches.

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        x: Bits 8--15 of the Regulator Flags field are not used.

   Excess Capabilities

         0                   1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |D|T|S|A|B|x x x x x x x x x x x|
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Policer:

        D: If bit 0 of the Excess Capabilities field is set, the policer
             function of the regulator is able to support discard.

        T: If bit 1 of the Excess Capabilities field is set, the policer
             function of the regulator is able to support tagging.

        S: If bit 2 of the Excess Capabilities field is set, the policer
             function of the regulator is able to support differentiated
             scheduling.

        Shaper:

        A: If bit 3 of the Excess Capabilities field is set, the shaper
             function of the regulator is able to support tagging.

        B: If bit 4 of the Excess Capabilities field is set, the shaper
             function of the regulator is able to support differentiated
             scheduling.

        x: Bits 5--15 of the Excess Capabilities field are not used.

   Hi Sharing
   Lo Sharing
             Defines a range of priority levels that support weighted
             sharing. Each priority level in the range Lo Sharing to Hi
             Sharing inclusive, supports weighted sharing. A priority
             level that supports weighted sharing offers a weighted
             sharing algorithm (for example, weighted round-robin)
             between waiting rooms within that priority level. This
             permits the output link bandwidth available at that
             priority level, to be shared between the waiting rooms
             allocated to that priority level, according to the Net
             Weight parameter of each waiting room.  The value 0xFF for
             both parameters indicates that this output port does not
             support weighted sharing in any priority level.

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   Max Classes
             If bit 3 of the Scheduler Flags field is zero, Max Classes
             gives the maximum number of QoS classes that may be
             supported by this switch port. In this case the maximum
             number of QoS classes that may be supported by this switch
             port is not affected by the number of QoS classes in use by
             other switch ports.  If bit 3 of the Scheduler Flags field
             is set, Max Classes gives the maximum number of QoS classes
             that may be supported by the entire switch. In this case it
             is assumed that use of these QoS classes may be distributed
             among the various switch ports.

   Default Size
             The size of waiting room that this output port allocates by
             default. The actual size of waiting room may be specified
             in the Scheduler Establishment message. The size of a
             waiting room specifies the maximum number of cells
             permitted to wait for transmission via that waiting room.
             Any further cells arriving at that waiting room beyond this
             number will be discarded.

   Default Discard Threshold
             The value of discard threshold that this output port
             allocates by default. The actual value of discard threshold
             may be specified in the Scheduler Establishment message.
             The discard threshold specifies the number of cells waiting
             for transmission via a waiting room after which further
             arriving cells will be subject to a discard mechanism.

   Max Buffer
             The maximum amount of buffer space, measured in cells,
             available to this port. If bit 7 of the Scheduler Flags
             field is zero this, buffer space is not shared with other
             ports. If bit 7 of the Scheduler Flags field is set, at
             least some of this buffer space is shared with other ports.

   Max Shaper Buffer
             The maximum amount of buffer space, measured in cells,
             available to a QoS connection or a QoS class within the
             shaper function of the regulator. This shaper buffer space
             is likely to be shared among all QoS classes and QoS
             connections using the shaper, so there is no guarantee that
             the amount of buffer space defined by the Max Shaper Buffer
             field will be available to any particular QoS class or QoS
             connection.

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   Scaling Factor
             The QoS Class Establishment and QoS Connection Management
             messages require parameters that describe cell rates in
             cells per second or their reciprocal, cell interarrival
             periods, in seconds per cell. In order that these
             parameters may be specified with a 32-bit unsigned integer,
             the switch defines a Scaling Factor to be used in defining
             such parameters. By appropriate choice of the Scaling
             Factor the switch can select the range and granularity of
             rate or time that can be specified with the 32-bit unsigned
             integer.  Further details are given in the discussion of
             the UPC Parameters field of the QoS Connection Management
             message.

9.3 Scheduler Establishment Message

   The Scheduler Establishment message is used to configure the
   scheduler on a specified output port. It is used to configure a
   waiting room, attach it to a leaf of the scheduler tree, and return a
   Scheduler Identifier to reference the waiting room. The Scheduler
   Establishment message may also be used to modify the parameters of an
   already established waiting room.

   Scheduler Identifiers in the range 0--255 represent default values.
   They are used for the priority levels that may be specified in the
   Class of Service field of Connection Management messages without
   requiring explicit establishment via a Scheduler Establishment
   message.  Each of these default values specifies a single waiting
   room with default parameters, configured as a FIFO queue, on each of
   the valid scheduler priority levels. (This permits Connection
   Management messages to continue to specify QoS requirements as a
   priority without requiring the use of any of the QoS messages.) The
   number of priority levels available to the scheduler is specified in
   the Priorities field of the Port Configuration and All Ports
   Configuration messages.

   The Scheduler Establishment Message is:

      Message Type = 97

   The Scheduler Establishment request and success response messages
   have the following format:

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    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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scheduler Identifier      |          Net Weight           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Reserved            |D|F|M|W|x x x x|   Priority    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Waiting Room Size                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Discard Threshold                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Scheduler Identifier
             The Scheduler Identifier is selected by the controller. It
             is used to identify the waiting room being established or
             modified in future messages. The Scheduler Identifier is
             taken from a namespace that is local to the switch port. A
             Scheduler Identifier in the Scheduler Establishment message
             must be greater than 0x00FF but less than 0xFFFF. The
             values 0 -- 0x00FF are reserved for use as default values.
             The default values of the Scheduler Identifier are used to
             specify the default settings for the scheduler. Each of the
             default values maps directly to one of the scheduler
             priority levels.  The value 0xFFFF is reserved for use in
             the QoS Connection Management message.

   Net Weight
             The Net Weight specifies the share of the bandwidth
             available to the priority level, specified by the Priority
             field, that should be given to this waiting room.  The Net
             Weight parameter is only valid if the priority level
             specified by the Priority field supports weighted sharing.

             The Net Weight is an unsigned 16-bit field specifying a
             binary fraction.  I.e. the bandwidth share, as a fraction
             of the bandwidth available to the priority level, is given
             by:

                Bandwidth share = Net Weight * 2**(-16)

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             A Net Weight of zero indicates equal sharing between all
             waiting rooms sharing this priority level that request a
             Net Weight of zero.  While a 16-bit field is used to
             specify the Net Weight it is understood that the accuracy
             of the bandwidth sharing is hardware dependent and is not
             specified.

             If weighted sharing is not required at a particular
             priority level, a waiting room with a Net Weight value of
             0xFFFF must be specified for that priority level. A
             priority level that does not support weighted sharing can
             only support a single waiting room.

   Flags

        D: Packet Discard
             Bit 0 of the Flags field, if set, indicates that packet
             discard is required on all connections and QoS classes
             routed through this waiting room.

        F: Frame-Based Scheduling
             Bit 1 of the Flags field, if set, indicates that frame-
             based scheduling is required on all connections and QoS
             classes routed through this waiting room.  In frame-based
             scheduling, a connection is only scheduled for transmission
             when a complete AAL-5 packet is available.  When a
             connection is scheduled for transmission, all cells
             belonging to one or more complete packets from that
             connection will be transmitted without being interleaved
             with any other cells on that output port. A QoS class may
             be routed through a waiting room configured with frame-
             based scheduling.  In this case each component connection
             of the QoS class will receive frame based scheduling. For
             correct distribution of bandwidth, each QoS class that
             requires frame-based scheduling should have its own waiting
             room.

        M: VC Merging
             Bit 2 of the Scheduler Flags field, if set, indicates that
             VC merging is required on all connections and QoS classes
             routed through this waiting room.  VC merging enables the
             multipoint-to-point merging of two or more incoming virtual
             connections onto a single outgoing virtual connection,
             without interleaving cells from different AAL-5 packets
             that bear the same VPI/VCI. VC merging differs from frame-
             based scheduling in that cells with a different VPI/VCI may
             be interleaved with those of a multipoint-to-point VC
             merging connection.  Most switches achieve VC merging by

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             using frame-based scheduling.  A QoS class may be routed
             through a waiting room configured with VC merging.  In this
             case each component connection of the QoS class will
             receive VC merging.

        W: Weighted Scheduling
             Bit 3 of the Flags field, if set, indicates that weighted
             scheduling is required on all connections and QoS classes
             routed through this waiting room.  All connections and QoS
             classes routed through this waiting room will require a
             Connection Weight or a QoS Class Weight respectively. The
             Connection Weight is specified in the QoS Connection
             Management message. The QoS Class Weight is specified in
             the QoS Class Establishment message. If weighted scheduling
             within this waiting room is unavailable, a failure response
             message must be returned indicating, "Weighted scheduling
             within this waiting room is unavailable."

             Bit 3 of the Flags field, if zero, indicates that this
             waiting room should be configured as a single FIFO queue.
             All cells arriving at this waiting room will receive
             first-in-first-out service. If Frame-Based Scheduling or VC
             Merging are also selected, the strict first-in-first-out
             service discipline will be modified by the requirement to
             support Frame-Based Scheduling or VC Merging.

        x: Bits 4--7 of the Flags field are not used.

   Priority
             Specifies the priority level in the scheduler to which the
             waiting room should be attached. Priorities are numbered
             from zero, with priority level zero being the highest
             priority.

   Waiting Room Size
             The required size of the waiting room.  The size of a
             waiting room specifies the maximum number of cells
             permitted to wait for transmission via that waiting room.
             Any further cells arriving at that waiting room beyond this
             number will be discarded. If the switch is unable to grant
             the size requested in the Scheduler Establishment request
             message it may reply with the actual size allocated to the
             waiting room in the Waiting Room Size field of the success
             response message.  A value of zero for the Waiting Room
             Size indicates that the default value should be used.

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   Discard Threshold
             The required value of the discard threshold.  The discard
             threshold specifies the number of cells waiting for
             transmission via a waiting room after which further
             arriving cells will be subject to a discard mechanism. The
             value of the Discard Threshold must be less than or equal
             to the value of the Waiting Room Size parameter for any
             given waiting room. If the switch is unable to grant the
             value of discard threshold requested in the Scheduler
             Establishment request message it may reply with the actual
             value of discard threshold allocated to the waiting room in
             the Discard Threshold field of the success response
             message.  A value of zero for the Discard Threshold
             indicates that the default value should be used.


9.4 QoS Class Establishment Message

   The QoS Class Establishment message is used to configure a QoS class
   on a specified port or to modify the parameters of an already
   established QoS class.  It configures the classifier and the
   regulator functions for the QoS class. It also configures the QoS
   class policer if a policing function is available for QoS classes.

   Two styles of QoS class are available. In one style each component
   connection of the QoS class may be routed independently to an output
   port and waiting room specified in its connection management message.
   In this case the Scheduler Identifier, and if required, the Excess
   Scheduler Id, are specified in the QoS Connection Management message
   that references this style of QoS class.  In the alternative style of
   QoS class, all component connections in the QoS class are routed to
   the same waiting room on the same output port. In this case the
   Output Port, the Scheduler Identifier, and if required, the Excess
   Scheduler Id, are specified in the QoS Class Establishment message.

   The classifier and regulator functions must be located together,
   either on an input port, on an output port, or centralized. Each port
   declares the location of its classifier and regulator functions at
   initialization using the QoS Configuration message. If the classifier
   and regulator functions are located on an input port, only
   connections that arrive at that input port may join a QoS class
   established on that port. However, each connection that is part of a
   QoS class established on that port may be switched to a different
   output port. If the classifier and regulator functions are located on
   an output port, connections that arrive at any input port may join a
   QoS class established on that port. However, all connections within a
   QoS class established on that port must be switched to that output
   port. For a centralized classifier and regulator function, there is

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   no restriction on the input ports on which connections in a QoS class
   must arrive, or on the output ports to which connections in a QoS
   class must be switched.  (For the case of a centralized classifier
   and regulator the actual port specified in the QoS Class
   Establishment message is used only for administrative purposes.  Any
   valid value of Port and Port Session Number, that specifies a
   centralized classifier and regulator function, may be used.)

   The QoS Class Establishment message is:

      Message Type = 98

   The QoS Class Establishment request and success response messages
   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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Port                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      QoS Class Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Regulator   | Excess Action |       QoS Class Weight        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scheduler Identifier      |      Excess Scheduler Id      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Output Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                 QoS Class Policer Parameters                  ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                QoS Class Regulator Parameters                 ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   QoS Class Identifier
             The QoS Class Identifier is selected by the controller. It
             is used to identify the QoS class being established or
             modified, in future QoS Connection Management and QoS Class
             Establishment messages.  It is taken from a namespace that

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             is global across the entire switch. No two QoS classes may
             have the same QoS Class Identifier regardless of the switch
             ports on which they are defined. A QoS Class Identifier in
             a QoS Class Establishment message must be greater than 0
             and less than 0xFFFFFFFF.

   Regulator
             The Regulator field specifies which function is required of
             the regulator.  Three possible functions are currently
             defined: none, policing, and shaping.

                None:      Regulator = 1
                Policing:  Regulator = 2
                Shaping:   Regulator = 3

             If the Regulator function is specified as none, no
             operations are performed by the regulator on the cells
             output from the classifier. Cells output from the
             classifier are transferred directly to the waiting room
             specified by the Scheduler Identifier.

             If policing is specified, a token bucket policer will be
             applied to the QoS class. The policer determines which
             cells conform to the specified policer traffic parameters
             and which do not. Conforming cells are transferred directly
             to the waiting room specified by the Scheduler Identifier.
             The action to be taken by the policer on the excess traffic
             is specified by the Excess Action field. The policer
             traffic parameters are specified in the QoS Class Regulator
             Parameters fields.

             If shaping is specified, traffic shaping will be applied to
             the QoS class.  Cells in a QoS class should leave the
             regulator spaced evenly apart at a rate defined by the QoS
             Class Regulator Parameters fields.  These cells are
             transferred directly to the waiting room specified by the
             Scheduler Identifier.  The jitter on the conforming cell
             stream on exit from the shaping function of the regulator
             is not specified.

   Excess Action

         0 1 2 3 4 5 6 7
        +-+-+-+-+-+-+-+-+
        |T|D|S|x x x x x|
        +-+-+-+-+-+-+-+-+

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        T: Tagging
             If bit 0 of the Excess Action field is set, all cells
             transferred to the waiting room specified by the Excess
             Scheduler Id will have their CLP bit set. If bit 0 of the
             Excess Action field is zero, the CLP bit of cells
             transferred to the waiting room specified by the Excess
             Scheduler Id will remain unchanged.

        D: Discard
             This function is only available if policing is selected as
             the regulator function.  If the Regulator field specifies
             Policing, and bit 1 of the Excess Action field is set, all
             cells determined by the policer to be in excess of the
             traffic parameters must be discarded. In this case the
             Excess Scheduler Id is not used and bit 0 of the Excess
             Action field should be ignored.

        S: Differentiated Scheduling
             This function operates differently according to whether
             policing or shaping is selected as the regulator function.

             If the Regulator field specifies Policing, and bit 1 of the
             Excess Action field is zero, and bit 2 of the Excess Action
             field is set, all cells determined by the policer to be in
             excess of the traffic parameters must be transferred to the
             waiting room specified by the Excess Scheduler Id.  In this
             case care must be taken in the implementation to ensure
             that within each virtual path connection or virtual channel
             connection, cells depart in the same order that they
             arrived.  If the Regulator field specifies Policing, and
             bit 1 of the Excess Action field is zero, and bit 2 of the
             Excess Action field is zero, all cells determined by the
             policer to be in excess of the traffic parameters must be
             transferred to the waiting room specified by the Scheduler
             Identifier.  In this case the Excess Scheduler Id is not
             used.

             If the Regulator field specifies Shaping, and bit 2 of the
             Excess Action field is zero, cells will be transferred from
             the QoS class to the waiting room pointed to by the
             Scheduler Identifier at a rate defined by the QoS Class
             Regulator Parameters. In this case the Excess Scheduler Id
             is not used.  If the Regulator field specifies Shaping, and
             bit 2 of the Excess Action field is set, additional cells
             will be scheduled for transmission by the waiting room
             pointed to by the Excess Scheduler Id. This permits a
             minimum cell rate to be allocated to the QoS class using
             the QoS Class Regulator Parameters and additional bandwidth

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             to be shared by the QoS class. The additional share of
             bandwidth is determined according to the parameters of the
             waiting room pointed to by the Excess Scheduler Id. If the
             Excess Scheduler Id is specified in the QoS Class
             Establishment message, the additional bandwidth will be
             shared by the entire QoS class. If the Excess Scheduler Id
             is specified in each individual QoS Connection Management
             message, the additional bandwidth is specific to that
             connection and not shared by the entire QoS class. Care
             must be taken in the implementation to ensure that within
             each virtual path connection or virtual channel connection,
             cells depart in the same order that they arrived.

        x: Bits 3--7 of the Excess Action field are not used.

   QoS Class Weight
             If bit 1 of the Scheduler Flags field of the QoS
             Configuration message indicates that weighted service may
             be applied to a QoS class, the QoS Class Weight parameter
             specifies the share of the bandwidth available to the
             waiting room that should be given to this QoS class.

             The QoS Class Weight is an unsigned 16-bit field specifying
             a binary fraction.  I.e. the bandwidth share, as a fraction
             of the bandwidth available to the waiting room, is given
             by:

                Bandwidth share = QoS Class Weight * 2**(-16)

             A QoS Class Weight of zero indicates equal sharing between
             all QoS classes sharing this waiting room that request a
             QoS Class Weight of zero.  While a 16-bit field is used to
             specify the QoS Class Weight it is understood that the
             accuracy of the bandwidth sharing is hardware dependent and
             is not specified.

             If the Regulator field of the QoS Class Establishment
             message indicates None, or Policer, the QoS Class Weight
             should be applied to the waiting room pointed to by the
             Scheduler Identifier. If the Regulator field of the QoS
             Class Establishment message indicates Shaper, the QoS Class
             Weight should be applied to the waiting room pointed to by
             the Excess Scheduler Id.

             If the specified waiting room is unable to offer weighted
             sharing for a QoS class, a failure response message should
             be returned with the failure code indicating: "This waiting
             room is unable to offer weighted sharing for a QoS class."

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   Scheduler Identifier
             If all conforming traffic from this QoS class is directed
             to the same waiting room, on the same output port, this
             field specifies the Scheduler Identifier for the entire QoS
             class. The Scheduler Identifier points to the waiting room,
             on the output port specified by the Output Port field, to
             which all conforming traffic should be sent.  If this field
             is not used it should be set to 0xFFFF. If each component
             connection of the QoS class specifies its own output port
             and waiting room, the Scheduler Identifier must be
             specified in the QoS Connection Management message and this
             field must be set to 0xFFFF.

   Excess Scheduler Id
             If all conforming traffic from this QoS class is directed
             to the same waiting room, on the same output port, this
             field specifies the Excess Scheduler Id for the entire QoS
             class. The Excess Scheduler Id points to the waiting room,
             on the output port specified by the Output Port field, to
             which all excess traffic should be sent.  If this field is
             not used it should be set to 0xFFFF. If each component
             connection of the QoS class specifies its own output port
             and waiting room, the Excess Scheduler Id must be specified
             in the QoS Connection Management message and this field
             must be set to 0xFFFF. If the Scheduler Id is specified in
             the QoS Class Establishment message, the Excess Scheduler
             Id must also be specified in the QoS Class Establishment
             message (or not used). If the Scheduler Id is specified in
             the QoS Connection Management message, the Excess Scheduler
             Id must also be specified in the QoS Connection Management
             message (or not used). The Excess Scheduler Id must not
             point to the same waiting room on the same output port as
             the Scheduler Identifier.

   Output Port
             If the Scheduler Identifier field in the QoS Establishment
             message is not 0xFFFF the Output Port field specifies the
             Output Port to which traffic from this QoS class should be
             routed. If the Scheduler Identifier field in the QoS
             Establishment message is 0xFFFF, this field is not used.

   QoS Class Policer Parameters
             A policer function may be applied to a QoS class on output
             from the classifier independently of the regulator
             function.  The QoS class policer function is identical to
             the connection policer function defined in the QoS

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             Connection Management message with the exception that it
             applies to all cells that belong to the QoS class rather
             than just cells that belong to a single connection.

             The QoS Class Policer Parameters 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     QoS Class Increment-1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       QoS Class Limit-1                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     QoS Class Increment-2                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       QoS Class Limit-2                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Reserved                     |C|A|x x x x x x|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             The definition of these fields is given in the UPC
             Parameters section of the QoS Connection Management
             message.

   QoS Class Regulator Parameters
             The QoS class regulator function is identical to the
             regulator function defined in the QoS Connection Management
             message with the exception that it applies to all cells
             that belong to the QoS class rather than just cells that
             belong to a single connection.

             The QoS Class Regulator Parameters 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                QoS Class Regulator Increment                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  QoS Class Regulator Limit                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             The definition of these fields is given in the Regulator
             Parameters section of the QoS Connection Management
             message.

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9.5 QoS Release Message

   The QoS Release message is used to delete a Scheduler Identifier or a
   QoS Class Identifier and to release all resources associated with it.

   The QoS Release message is:

      Message Type = 99

   The QoS Release request and success response messages 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Port                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Reserved            |     Scheduler Identifier      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      QoS Class Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port
             If the QoS Release message contains a Scheduler Identifier,
             the Port field must contain the Port Number of the switch
             output port to which the Scheduler Identifier applies. If
             the QoS Release message contains a QoS Class Identifier,
             any valid Port number may be used. (The QoS Class
             Identifier has a global namespace.)

   Port Session Number
             The current Port Session Number for the port specified in
             the Port field.

   Scheduler Identifier
             If the Scheduler Identifier contains the value 0xFFFF the
             QoS Class Identifier specified in the QoS Class Identifier
             field should be released.  Else, if the value of the
             Scheduler Identifier lies in the range 0x0100 -- 0xFFFE
             inclusive, the Scheduler Identifier specified by the
             Scheduler Identifier field should be released.  A Scheduler

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             Identifier with a value less than 0x0100 is invalid in a
             QoS Release message.  (It specifies a default value which
             may not be released.)

   QoS Class Identifier
             If the Scheduler Identifier contains the value 0xFFFF the
             QoS Class Identifier field specifies the QoS Class
             Identifier to be released.

   If the QoS Release message requests that a Scheduler Identifier be
   released, and the Scheduler Identifier is still in use by one or more
   established connections, a failure response must be returned with the
   failure code indicating: "Scheduler Identifier still in use." If the
   QoS Release message requests that a QoS Class Identifier be released,
   and the QoS Class Identifier is still in use by one or more
   established connections, a failure response must be returned with the
   failure code indicating: "QoS Class Identifier still in use."



(page 86 continued on part 4)

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