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INFORMATIONAL

Network Working Group                                    P. Newman, Nokia
Request for Comments: 2297                             W. Edwards, Sprint
Updates: 1987                                            R. Hinden, Nokia
Category: Informational                                 E. Hoffman, Nokia
                                                            F. Ching Liaw
                                                           T. Lyon, Nokia
                                                   G. Minshall, Fiberlane
                                                               March 1998


       Ipsilon's General Switch Management Protocol Specification
                              Version 2.0

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.


Abstract

   This memo specifies enhancements to the  General Switch Management
   Protocol (GSMP) [RFC1987]. The major enhancement is the addition of
   Quality of Service (QoS) messages. Other improvements have been made
   to the protocol resulting from operational experience. GSMP is a
   general purpose protocol to control an ATM switch. It allows a
   controller to establish and release connections across the switch;
   add and delete leaves on a multicast connection; manage switch ports;
   request configuration information; and request statistics.

















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Table of Contents

   1. Introduction....................................................3

   2. GSMP Packet Encapsulation.......................................4
      2.1 ATM Encapsulation...........................................4
      2.2 Ethernet Encapsulation......................................6

   3. Common Definitions and Procedures...............................7
      3.1 GSMP Packet Format..........................................8
      3.2 Failure Response Messages..................................11

   4. Connection Management Messages.................................16
      4.1 Add Branch Message.........................................21
      4.2 Delete Tree Message........................................23
      4.3 Verify Tree Message........................................24
      4.4 Delete All Message.........................................24
      4.5 Delete Branches Message....................................25
      4.6 Move Branch Message........................................27

   5. Port Management Messages.......................................29
      5.1 Port Management Message....................................29
      5.2 Label Range Message........................................34

   6. State and Statistics Messages..................................37
      6.1 Connection Activity Message................................38
      6.2 Statistics Messages........................................40
          6.2.1 Port Statistics Message..............................44
          6.2.2 Connection Statistics Message........................44
          6.2.3 QoS Class Statistics Message.........................44
      6.3 Report Connection State Message............................45

   7. Configuration Messages.........................................49
      7.1 Switch Configuration Message...............................50
      7.2 Port Configuration Message.................................51
      7.3 All Ports Configuration Message............................57

   8. Event Messages.................................................59
      8.1 Port Up Message............................................60
      8.2 Port Down Message..........................................60
      8.3 Invalid VPI/VCI Message....................................61
      8.4 New Port Message...........................................61
      8.5 Dead Port Message..........................................61

   9. Quality of Service Messages....................................61
      9.1 Abstract Switch Model......................................62
      9.2 QoS Configuration Message..................................66
      9.3 Scheduler Establishment Message............................74



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      9.4 QoS Class Establishment Message............................78
      9.5 QoS Release Message........................................85
      9.6 QoS Connection Management Message..........................86
      9.7 QoS Failure Response Codes.................................97

   10. Adjacency Protocol............................................97
      10.1 Packet Format.............................................98
      10.2 Procedure.................................................101
      10.3 Loss of Synchronization...................................103

   11. Summary of Failure Response Codes.............................104

   12. Summary of Message Set........................................105

   References........................................................107
   Security Considerations...........................................107
   Authors' Addresses................................................107
   Full Copyright Statement..........................................109



1. Introduction

   The General Switch Management Protocol (GSMP), is a general purpose
   protocol to control an ATM switch. GSMP allows a controller to
   establish and release connections across the switch; add and delete
   leaves on a multicast connection; manage switch ports; request
   configuration information; and request statistics. It also allows the
   switch to inform the controller of asynchronous events such as a link
   going down. GSMP runs across an ATM link connecting the controller to
   the switch, on a control connection (virtual channel) established at
   initialization. GSMP operation across an Ethernet link is also
   specified. The GSMP protocol is asymmetric, the controller being the
   master and the switch being the slave. Multiple switches may be
   controlled by a single controller using multiple instantiations of
   the protocol over separate control connections.

   A switch is assumed to contain multiple "ports". Each port is a
   combination of one "input port" and one "output port". Some GSMP
   requests refer to the port as a whole whereas other requests are
   specific to the input port or the output port.  ATM cells arrive at
   the switch from an external communication link on incoming virtual
   paths or virtual channels at an input port. ATM cells depart from the
   switch to an external communication link on outgoing virtual paths or
   virtual channels from an output port. Virtual paths on a port or link
   are referenced by their virtual path identifier (VPI). Virtual
   channels on a port or link are referenced by their virtual path and
   virtual channel identifiers (VPI/VCI).



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   A virtual channel connection across a switch is formed by connecting
   an incoming virtual channel to one or more outgoing virtual channels.
   Virtual channel connections are referenced by the input port on which
   they arrive and the virtual path and virtual channel identifiers
   (VPI/VCI) of their incoming virtual channel. A virtual path
   connection across a switch is formed by connecting an incoming
   virtual path to one or more outgoing virtual paths. Virtual path
   connections are referenced by the input port on which they arrive and
   their virtual path identifier (VPI).  In a virtual path connection
   the value of the VCI in each cell on that, connection is not used by
   the switch and remains unchanged by the switch.

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

   In general a virtual channel is established with a certain quality of
   service (QoS). A rich set of QoS messages is introduced in this
   version of the protocol. However, implementation or operation of GSMP
   without any of the messages defined in Section 9, "Quality of service
   messages," is permitted.  In this case each virtual channel
   connection or virtual path connection may be assigned a priority when
   it is established. It may be assumed that for virtual 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 port of
   the switch supports may be obtained from the port configuration
   message.

   GSMP contains an adjacency protocol. The adjacency protocol is used
   to synchronize state across the link, to negotiate which version of
   the GSMP protocol to use, to discover the identity of the entity at
   the other end of a link, and to detect when it changes.


2. GSMP Packet Encapsulation

2.1 ATM Encapsulation

   GSMP packets are variable length and for an ATM data link layer they
   are encapsulated directly in an AAL-5 CPCS-PDU [I.363] with an
   LLC/SNAP header as illustrated:





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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               LLC (0xAA-AA-03)                |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
   |                   SNAP (0x00-00-00-88-0C)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                         GSMP Message                          ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Pad (0 - 47 octets)                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +               AAL-5 CPCS-PDU Trailer (8 octets)               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   (The convention in the documentation of Internet Protocols [RFC1700]
   is to express numbers in decimal. Numbers in hexadecimal format are
   specified by prefacing them with the characters "0x".  Data is
   pictured in "big-endian" order. That is, fields are described left to
   right, with the most significant octet on the left and the least
   significant octet on the right. Whenever a diagram shows a group of
   octets, the order of transmission of those octets is the normal order
   in which they are read in English. Whenever an octet represents a
   numeric quantity the left most bit in the diagram is the high order
   or most significant bit. That is, the bit labeled 0 is the most
   significant bit. Similarly, whenever a multi-octet field represents a
   numeric quantity the left most bit of the whole field is the most
   significant bit. When a multi-octet quantity is transmitted, the most
   significant octet is transmitted first. This is the same coding
   convention as is used in the ATM layer [I.361] and AAL-5 [I.363].)

   The LLC/SNAP header contains the octets: 0xAA 0xAA 0x03 0x00 0x00
   0x00 0x88 0x0C. (0x880C is the assigned Ethertype for GSMP.)

   The maximum transmission unit (MTU) of the GSMP Message field is 1492
   octets.

   The virtual channel over which a GSMP session is established between
   a controller and the switch it is controlling is called the GSMP
   control channel.  The default VPI and VCI of the GSMP control channel
   for LLC/SNAP encapsulated GSMP messages on an ATM data link layer is:

      VPI = 0
      VCI = 15.




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2.2 Ethernet Encapsulation

   GSMP packets may be encapsulated on an Ethernet data link as
   illustrated:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Destination Address                      |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                         Source Address                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Ethertype (0x88-0C)       |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   ~                         GSMP Message                          ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sender Instance                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Receiver Instance                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Pad                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Frame Check Sequence                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Destination Address
             For the SYN message of the adjacency protocol the
             Destination Address is the broadcast address
             0xFFFFFFFFFFFF. (Alternatively, it is also valid to
             configure the node with the unicast 48-bit IEEE MAC address
             of the destination. In this case the configured unicast
             Destination Address is used in the SYN message.) For all
             other messages the Destination Address is the unicast 48-
             bit IEEE MAC address of the destination. This address may
             be discovered from the Source Address field of messages
             received during synchronization of the adjacency protocol.

   Source Address
             For all messages the Source Address is the 48-bit IEEE MAC
             address of the sender.

   Ethertype
             The assigned Ethertype for GSMP is 0x880C.




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   GSMP Message
             The maximum transmission unit (MTU) of the GSMP Message
             field is 1492 octets.

   Sender Instance
             The Sender Instance number for the link obtained from the
             adjacency protocol.  This field is already present in the
             adjacency protocol message. It is appended to all non-
             adjacency GSMP messages in the Ethernet encapsulation to
             offer additional protection against the introduction of
             corrupt state.

   Receiver Instance
             The Receiver Instance number is what the sender believes is
             the current instance number for the link, allocated by the
             entity at the far end of the link.  This field is already
             present in the adjacency protocol message. It is appended
             to all non-adjacency GSMP messages in the Ethernet
             encapsulation to offer additional protection against the
             introduction of corrupt state.

   Pad
             The minimum length of the data field of an Ethernet packet
             is 46 octets.  If necessary, padding should be added such
             that it meets the minimum Ethernet frame size. This padding
             should be octets of zero and it is not considered to be
             part of the GSMP message.

   After the adjacency protocol has achieved synchronization, for every
   GSMP message received with an Ethernet encapsulation, the receiver
   must check the Source Address from the Ethernet MAC header, the
   Sender Instance, and the Receiver Instance.  The incoming GSMP
   message must be discarded if the Sender Instance and the Source
   Address do not match the values of Sender Instance and Sender Name
   stored by the "Update Peer Verifier" operation of the GSMP adjacency
   protocol. The incoming GSMP message must also be discarded if it
   arrives over any port other than the port over which the adjacency
   protocol has achieved synchronization.  In addition, the incoming
   message must also be discarded if the Receiver Instance field does
   not match the current value for the Sender Instance of the GSMP
   adjacency protocol.


3. Common Definitions and Procedures

   GSMP is a master-slave protocol. The controller issues request
   messages to the switch. Each request message indicates whether a
   response is required from the switch and contains a transaction



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   identifier to enable the response to be associated with the request.
   The switch replies with a response message indicating either a
   successful result or a failure. There are five classes of GSMP
   request-response message: Connection Management, Port Management,
   State and Statistics, Configuration, and Quality of Service.  The
   switch may also generate asynchronous Event messages to inform the
   controller of asynchronous events.  Event messages are not
   acknowledged by the controller. There is also an adjacency protocol
   message used to establish synchronization across the link and
   maintain a handshake.

   For the request-response messages, each message type has a format for
   the request message and a format for the success response.  Unless
   otherwise specified a failure response message is identical to the
   request message that caused the failure, with the Code field
   indicating the nature of the failure. Event messages have only a
   single format defined as they are not acknowledged by the controller.

   Switch ports are described by a 32-bit port number. The switch
   assigns port numbers and it may typically choose to structure the 32
   bits into subfields that have meaning to the physical structure of
   the switch (e.g. slot, port). In general, a port in the same physical
   location on the switch will always have the same port number, even
   across power cycles. The internal structure of the port number is
   opaque to the GSMP protocol. However, for the purposes of network
   management such as logging, port naming, and graphical
   representation, a switch may declare the physical location (physical
   slot and port) of each port. Alternatively, this information may be
   obtained by looking up the product identity in a database.

   Each switch port also maintains a port session number assigned by the
   switch. A message, with an incorrect port session number must be
   rejected.  This allows the controller to detect a link failure and to
   keep state synchronized.

   Except for the adjacency protocol message, no GSMP messages may be
   sent across the link until the adjacency protocol has achieved
   synchronization, and all GSMP messages received on a link that does
   not currently have state synchronization must be discarded.

3.1 GSMP Packet Format

   All GSMP messages, except the adjacency protocol message, 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                          Message Body                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
             The version number of the GSMP protocol being used in this
             session. It should be set by the sender of the message to
             the GSMP protocol version negotiated by the adjacency
             protocol.

   Message Type
             The GSMP message type. GSMP messages fall into six classes:
             Connection Management, Port Management, State and
             Statistics, Configuration, Quality of Service, and Events.
             Each class 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, a Port
             Management request message, or a Quality of Service 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 must be generated if the request fails.
             For Sate and Statistics, and Configuration 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". (This facility was added to
             reduce the control traffic in the case where the controller
             periodically checks that the state in the switch is
             correct. If the controller does not use this capability,
             all request messages should be sent with a value of
             "AckAll.")






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             In a response message the result field can have three
             values: "Success," "More," and "Failure". The "Success" and
             "More" results both indicate a success response. The "More"
             result indicates that the success response exceeds the
             maximum transmission unit of the data link and that one or
             more further messages will be sent to complete the success
             response. All messages that belong to the same success
             response will have the same Transaction Identifier. The
             "Success" result indicates a success response that may be
             contained in a single message or the final message of a
             success response spanning multiple messages.

             The encoding of the result field is:

                  NoSuccessAck:  Result = 1
                  AckAll:        Result = 2
                  Success:       Result = 3
                  Failure:       Result = 4
                  More:          Result = 5.


             The Result field is not used in an adjacency protocol
             message.

   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. The Transaction Identifier is not
             used, and the field is not present, in the adjacency
             protocol.

   The following fields are frequently found in GSMP messages. They are
   defined here to avoid repetition.




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   Port
             Gives the port number of the switch port to which the
             message applies.

   Port Session Number
             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.

             If the Port Session Number in a request message does not
             match the current Port Session Number for the specified
             port, a failure response message must be returned with the
             Code field indicating, "Invalid port session number."  The
             current port session number for a port may be obtained
             using a Port Configuration or an All Ports Configuration
             message.

   Any field in a GSMP message that is unused or defined as "reserved"
   must be set to zero by the sender and ignored by the receiver.

   It is not an error for a GSMP message to contain additional data
   after the end of the Message Body. This is to support development and
   experimental purposes. However, the maximum transmission unit of the
   GSMP message, as defined by the data link layer encapsulation, must
   not be exceeded.

   A success response message must not be sent until the requested
   operation has been successfully completed.

3.2 Failure Response Messages

   A failure response message is formed by returning the request message
   that caused the failure with the Result field in the header
   indicating failure (Result = 4) and the Code field giving the failure
   code. The failure code specifies the reason for the switch being
   unable to satisfy the request message.

   If the switch issues a failure response in reply to a request
   message, no change should be made to the state of the switch as a
   result of the message causing the failure. (For request messages that
   contain multiple requests, such as the Delete Branches message, the



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   failure response message will specify which requests were successful
   and which failed. The successful requests may result in changed
   state.)

   If the switch issues a failure response it must choose the most
   specific failure code according to the following precedence:

       Invalid Message

       Failure specific to the particular message type (failure code
           16). (The meaning of this failure is dependent upon the
           particular message type and is specified in the text defining
           the message.)

       A failure response specified in the text defining the message
           type.

       Connection Failures

       Virtual Path Connection Failures

       Multicast Failures

       QoS Failures (QoS failures are specified in Section 9.7.)

       General Failures

   If multiple failures match in any of the following categories, the
   one that is listed first should be returned. The following failure
   response messages and failure codes are defined:

   Invalid Message

       3:  The specified request is not implemented on this switch.
               The Message Type field specifies a message that is not
               implemented on the switch or contains a value that is not
               defined in the version of the protocol running in this
               session of GSMP.

       5:  One or more of the specified ports does not exist.
               At least one of the ports specified in the message is
               invalid. A port is invalid if it does not exist or if it
               has been removed from the switch.

       4:  Invalid Port Session Number.
               The value given in the Port Session Number field does not
               match the current Port Session Number for the specified
               port.



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   Connection Failures

       8:  The specified connection does not exist.
               An operation that expects a connection to be specified,
               either a virtual channel or a virtual path connection,
               cannot locate the specified connection. A virtual channel
               connection is specified by the input port, input VPI, and
               input VCI on which it arrives. A virtual path connection
               is specified by the input port and input VPI on which it
               arrives.

       9:  The specified branch does not exist.
               An operation that expects a branch of an existing
               connection to be specified, either a virtual channel or a
               virtual path connection, cannot locate the specified
               branch.  A branch of a virtual channel connection is
               specified by the virtual channel connection it belongs to
               and the output port, output VPI, and output VCI on which
               it departs. A branch of a virtual path connection is
               specified by the virtual path connection it belongs to
               and the output port and output VPI on which it departs.

       18: One or more of the specified input VPIs is invalid.

       19: One or more of the specified input VCIs is invalid.

       20: One or more of the specified output VPIs is invalid.

       21: One or more of the specified output VCIs is invalid.

       22: Invalid Class of Service field in a Connection Management
               message.
               The value of the Class of Service field is invalid.

       23: Insufficient resources for QoS Profile.
               The resources requested by the QoS Profile in the Class
               of service field are not available.

   Virtual Path Connections

       24: Virtual path switching is not supported on this input port.

       25: Point-to-multipoint virtual path connections are not
               supported on either the requested input port or the
               requested output port.
               One or both of the requested input and output ports is
               unable to support point-to-multipoint virtual path
               connections.



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       26: Attempt to add a virtual path connection branch to an
               existing virtual channel connection.
               It is invalid to mix branches switched as virtual channel
               connections with branches switched as virtual path
               connections on the same point-to-multipoint connection.

       27: Attempt to add a virtual channel connection branch to an
               existing virtual path connection.
               It is invalid to mix branches switched as virtual channel
               connections with branches switched as virtual path
               connections on the same point-to-multipoint connection.

   Multicast Failures

       10: A branch belonging to the specified point-to-multipoint
               connection is already established on the specified output
               port and the switch cannot support more than a single
               branch of any point-to-multipoint connection on the same
               output port.

       11: The limit on the maximum number of point-to-multipoint
               connections that the switch can support has been reached.

       12: The limit on the maximum number of branches that the
               specified point-to-multipoint connection can support has
               been reached.

       17: Cannot label each output branch of a point-to-multipoint tree
               with a different label.
               Some early designs, and some low-cost ATM switch designs,
               require all output branches of a multicast connection to
               use the same value of VPI/VCI.

       28: Only point-to-point bidirectional connections may be
               established.
               It is an error to attempt to add an additional output
               branch to an existing connection with the bidirectional
               flag set.

       13: Unable to assign the requested VPI/VCI value to the requested
               branch on the specified point-to-multipoint connection.
               Although the requested VPI and VCI are valid, the switch
               is unable to support the request using the specified
               values of VPI and VCI for some reason not covered by the
               above failure responses. This message implies that a
               valid value of VPI or VCI exists that the switch could





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               support. For example, some switch designs restrict the
               number of distinct VPI/VCI values available to a point-
               to-multipoint connection. (Most switch designs will not
               require this message.)

       14: General problem related to the manner in which point-to-
               multipoint is supported by the switch.
               Use this message if none of the more specific multicast
               failure messages apply.  (Most switch designs will not
               require this message.)

   General Failures

       2:  Invalid request message.
               There is an error in one of the fields of the message not
               covered by a more specific failure message.

       6:  One or more of the specified ports is down.
               A port is down if its Port Status is Unavailable.
               Connection Management, Connection State, Port Management,
               and Configuration operations are permitted on a port that
               is Unavailable. Connection Activity and Statistics
               operations are not permitted on a port that is
               Unavailable and will generate this failure response. A
               Port Management message specifying a Take Down function
               on a port already in the Unavailable state will also
               generate this failure response.

       15: Out of resources.
               The switch has exhausted a resource not covered by a more
               specific failure message, for example, running out of
               memory.

       1:  Unspecified reason not covered by other failure codes.
               The failure message of last resort.

   The following failure response messages are only used by the Label
               Range message.

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

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



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

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

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

4.1 Add Branch Message

   The Add Branch message is a connection management message used to
   establish a virtual channel connection or a virtual path connection
   or to add an additional branch to an existing virtual channel
   connection or virtual path connection. It may also be used to check
   the connection state stored in the switch. The connection is
   specified by the Input Port, Input VPI, and Input VCI fields. The
   output branch is specified by the Output Port, Output VPI, and Output
   VCI fields. The quality of service requirements of the connection are
   specified by the Class of Service field. To request a virtual channel
   connection the Virtual Channel Connection (VCC) Add Branch message
   is:

      Message Type = 16




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

      Message Type = 26

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

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

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

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

   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields; or the virtual path connection specified
   by the Input Port and Input VPI fields; already exists and the
   specified output branch also already exists, the QoS attributes of
   the connection, specified by the Class of Service field, if different
   from the request message, should be changed to that in the request
   message.  A success response message must be sent if the Result field
   of the request message is "AckAll".  This allows the controller to
   periodically reassert the state of a connection or to change its
   priority. If the result field of the request message is
   "NoSuccessAck" a success response message should not be returned.



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   This may be used to reduce the traffic on the control link for
   messages that are reasserting previously established state. For
   messages that are reasserting previously established state, the
   switch must always check that this state is correctly established in
   the switch hardware (i.e. the actual connection tables used to
   forward cells).

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

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

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

4.2 Delete Tree Message

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

      Message Type = 18



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   If the Result field of the request message is "AckAll" a success
   response message must be sent upon successful deletion of the
   specified connection. The success message must not be sent until the
   delete operation has been completed and if possible, not until all
   data on the connection, queued for transmission, has been
   transmitted. The Number of Branches field is not used in either the
   request or response messages of the Delete Tree message.

4.3 Verify Tree Message

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

      Message Type = 19 is reserved.

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

4.4 Delete All Message

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

      Message Type = 20

   If the Result field of the request message is "AckAll" a success
   response message must be sent upon completion of the operation. The
   Number of Branches field is not used in either the request or
   response messages of the Delete All message.  The success response
   message must not be sent until the operation has been completed.

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

         The specified request is not implemented on this switch.




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         One or more of the specified ports does not exist.

         Invalid Port Session Number.

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

4.5 Delete Branches Message

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

      Message Type = 17

   The request message has the following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    | Message Type  |    Result     |     Code      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Transaction Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Reserved            |      Number of Elements       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                    Delete Branch Elements                     ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Number of Elements
             Specifies the number of Delete Branch Elements to follow in
             the message. The number of Delete Branch Elements in a
             Delete Branches message must not cause the packet length to
             exceed the maximum transmission unit defined by the
             encapsulation.

   Each Delete Branch Element specifies an output branch to be deleted
   and has the following structure:





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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Input Port                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Error |      Input VPI        |          Input VCI            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Output Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |x x x x|      Output VPI       |          Output VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Error
             Is used to return a failure code indicating the reason for
             the failure of a specific Delete Branch Element in a Delete
             Branches failure response message.  The Error field is not
             used in the request message and must be set to zero.  A
             value of zero is used to indicate that the delete operation
             specified by this Delete Branch Element was successful.
             Values for the other failure codes are specified in Section
             3.2, "Failure Response Messages."

             All other fields of the Delete Branch Element have the same
             definition as specified for the other connection management
             messages.

   In each Delete Branch Element, either a virtual channel connection is
   specified by the Input Port, Input VPI, and Input VCI fields; or a
   virtual path connection is specified by the Input Port and Input VPI
   fields. The specific branch to be deleted is indicated by the Output
   Port, Output VPI, and Output VCI fields for virtual channel
   connections and by the Output Port and Output VPI for virtual path
   connections.

   If the Result field of the Delete Branches request message is
   "AckAll" a success response message must be sent upon successful
   deletion of the branches specified by all of the Delete Branch
   Elements. The success response message must not be sent until all of
   the delete branch operations have been completed. The success
   response message is only sent if all of the requested delete branch
   operations were successful. No Delete Branch Elements are returned in
   a Delete Branches success response message and the Number of Elements
   field must be set to zero.

   If there is a failure in any of the Delete Branch Elements a Delete
   Branches failure response message must be returned. The Delete
   Branches failure response message is a copy of the request message
   with the Code field of the entire message set to, "Failure specific



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   to the particular message type," and the Error field of each Delete
   Branch Element indicating the result of each requested delete
   operation. A failure in any of the Delete Branch Elements must not
   interfere with the processing of any other Delete Branch Elements.

4.6 Move Branch Message

   The Move Branch message is used to move a branch of an existing
   connection from its current output port VPI/VCI to a new output port
   VPI/VCI in a single atomic transaction. This operation occurs
   frequently in IP switching, every time a flow is switched from hop-
   by-hop forwarding to a dedicated virtual channel.  The Move Branch
   connection management message has 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                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Flags |        Input VPI      |           Input VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Old Output Port                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |x x x x|    Old Output VPI     |        Old Output VCI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        New Output Port                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |x x x x|    New Output VPI     |        New Output VCI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Number of Branches      |       Class of Service        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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




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      Message Type = 22

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

   For the VCC Move Branch message, if the virtual channel connection
   specified by the Input Port, Input VPI, and Input VCI fields already
   exists, but the output branch specified by the Old Output Port, Old
   Output VPI, and Old Output VCI fields does not exist as a branch on
   that connection, a failure response must be returned with the Code
   field indicating, "The specified branch does not exist."

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

      Message Type = 27

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

   For the VPC Move Branch message, if the virtual path connection
   specified by the Input Port and Input VPI fields already exists, but
   the output branch specified by the Old Output Port and Old Output VPI
   fields does not exist as a branch on that connection, a failure
   response must be returned with the Code field indicating, "The
   specified branch does not exist."



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   If the virtual channel connection specified by the Input Port, Input
   VPI, and Input VCI fields; or the virtual path connection specified
   by the Input Port and  Input VPI fields; does not exist, a failure
   response must be returned with the Code field indicating, "The
   specified connection does not exist."

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


5. Port Management Messages

5.1 Port Management Message

   The Port Management message allows a port to be brought into service,
   taken out of service, looped back, reset, or the transmit cell rate
   changed.  Only the Bring Up and the Reset Input Port functions change
   the connection state (established connections) on the input port.
   Only the Bring Up function changes the value of the Port Session
   Number. If the Result field of the request message is "AckAll" a
   success response message must be sent upon successful completion of
   the operation. The success response message must not be sent until
   the operation has been completed. The Port Management Message is:

      Message Type = 32

   The Port Management message has the following format for the request
   and success response messages:














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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                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Event Sequence Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Event Flags  |   Duration    |          Function             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Transmit Cell Rate                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Event Sequence Number
             In the success response message gives the current value of
             the Event Sequence Number of the switch port indicated by
             the Port field. 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. If the Event
             Sequence Number in the success response differs from the
             Event Sequence Number of the most recent Event message
             received for that port, events have occurred that were not
             reported via an Event message. This is most likely to be
             due to the flow control that restricts the rate at which a
             switch can send Event messages for each port. In the
             request message this field is not used.

   Event Flags
             Field in the request message is used to reset the Event
             Flags in the switch port indicated by the Port field. Each
             Event Flag in a switch port corresponds to a type of Event
             message. When a switch port sends an Event message it sets
             the corresponding Event Flag on that port. The port is not
             permitted to send another Event message of the same type
             until the Event Flag has been reset. If the Function field
             in the request message is set to "Reset Event Flags," for
             each bit that is set in the Event Flags field, the
             corresponding Event Flag in the switch port is reset.

             The Event Flags field is only used in a request message
             with the Function field set to "Reset Event Flags." For all
             other values of the Function field, the Event Flags field



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             is not used.  In the success response message the Event
             Flags field must be set to the current value of the Event
             Flags for the port, after the completion of the operation
             specified by the request message, for all values of the
             Function field. Setting the Event Flags field to all zeros
             in a "Reset Event Flags" request message allows the
             controller to obtain the current state of the Event Flags
             and the current Event Sequence Number of the port without
             changing the state of the Event Flags.

             The correspondence between the types of Event message and
             the bits of the Event Flags field is as follows:

                 0 1 2 3 4 5 6 7
                +-+-+-+-+-+-+-+-+
                |U|D|I|N|Z|x x x|
                +-+-+-+-+-+-+-+-+

                U: Port Up          Bit 0, (most significant bit)
                D: Port Down        Bit 1,
                I: Invalid VPI/VCI  Bit 2,
                N: New Port         Bit 3,
                Z: Dead Port        Bit 4,
                x: Unused           Bits 5--7.

   Duration
             Is the length of time, in seconds, that any of the loopback
             states remain in operation. When the duration has expired
             the port will automatically be returned to service.  If
             another Port Management message is received for the same
             port before the duration has expired, the loopback will
             continue to remain in operation for the length of time
             specified by the Duration field in the new message. The
             Duration field is only used in request messages with the
             Function field set to Internal Loopback, External Loopback,
             or Bothway Loopback.

   Function
             Specifies the action to be taken. The specified action will
             be taken regardless of the current status of the port
             (Available, Unavailable, or any Loopback state).  If the
             specified function requires a new Port Session Number to be
             generated, the new Port Session Number must be returned in
             the success response message.  The defined values of the
             Function field are:

             Bring Up:
                  Function = 1. Bring the port into service. All



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                  connections that arrive at the specified input port
                  must be deleted and a new Port Session Number must be
                  selected using some form of random number. On
                  completion of the operation all dynamically assigned
                  VPI/VCI values for the specified input port must be
                  unassigned, i.e. no virtual connections will be
                  established in the VPI/VCI space that GSMP controls on
                  this input port. The Port Status of the port
                  afterwards will be Available.

             Take Down:
                  Function = 2. Take the port out of service. Any cells
                  received at this port will be discarded. No cells will
                  be transmitted from this port. The Port Status of the
                  port afterwards will be Unavailable.

                  The behavior is undefined if the port is taken down
                  over which the GSMP session that controls the switch
                  is running. (In this case the most probable behavior
                  would be for the switch either to ignore the message
                  or to terminate the current GSMP session and to
                  initiate another session, possibly with the backup
                  controller, if any.) The correct method to reset the
                  link over which GSMP is running is to issue an RSTACK
                  message in the adjacency protocol.

             Internal Loopback:
                  Function = 3. Cells arriving at the output port from
                  the switch fabric are looped through to the input port
                  to return to the switch fabric. All of the ATM
                  functions of the input port above the physical layer,
                  e.g. header translation, are performed upon the looped
                  back cells. The Port Status of the port afterwards
                  will be Internal Loopback.

             External Loopback:
                  Function = 4. Cells arriving at the input port from
                  the external communications link are immediately
                  looped back to the communications link at the physical
                  layer without entering the input port. None of the ATM
                  functions of the input port above the physical layer
                  are performed upon the looped back cells. The Port
                  Status of the port afterwards will be External
                  Loopback.

             Bothway Loopback:
                  Function = 5. Both internal and external loopback are




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                  performed. The Port Status of the port afterwards will
                  be Bothway Loopback.

             Reset Input Port:
                  Function = 6. All connections that arrive at the
                  specified input port must be deleted and the input and
                  output port hardware re-initialized. On completion of
                  the operation all dynamically assigned VPI/VCI values
                  for the specified input port must be unassigned, i.e.
                  no virtual connections will be established in the
                  VPI/VCI space that GSMP controls on this input port.
                  The range of VPIs and VCIs that may be controlled by
                  GSMP on this port will be set to the default values
                  specified in the Port Configuration message.  The
                  transmit cell rate of the output port must be set to
                  its default value. The Port Session Number is not
                  changed by the Reset Input Port function.  The Port
                  Status of the port afterwards will be Unavailable.

             Reset Event Flags:
                  Function = 7. For each bit that is set in the Event
                  Flags field, the corresponding Event Flag in the
                  switch port must be reset. The Port Status of the port
                  is not changed by this function.

             Set Transmit Cell Rate:
                  Function = 8. Sets the transmit cell rate of the
                  output port as close as possible to the rate specified
                  in the Transmit Cell Rate field. In the success
                  response message the Transmit Cell Rate must indicate
                  the actual transmit cell rate of the output port.  If
                  the transmit cell rate of the requested output port
                  cannot be changed, a failure response must be returned
                  with the Code field indicating: "The transmit cell
                  rate of this output port cannot be changed." If the
                  transmit cell rate of the requested output port can be
                  changed, but the value of the Transmit Cell Rate field
                  is beyond the range of acceptable values, a failure
                  response must be returned with the Code field
                  indicating: "Requested transmit cell rate out of range
                  for this output port." In the failure response message
                  the Transmit Cell Rate must contain the same value as
                  contained in the request message that caused the
                  failure. The transmit cell rate of the output port is
                  not changed by the Bring Up, Take Down, or any of the
                  Loopback functions. It is returned to the default
                  value by the Reset Input Port function.




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        Transmit Cell Rate
             This field is only used in request and success response
             messages with the Function field set to "Set Transmit Cell
             Rate." It is used to set the output cell rate of the output
             port. It is specified in cells/s. If the Transmit Cell Rate
             field contains the value 0xFFFFFFFF the transmit cell rate
             of the output port should be set to the highest valid
             value.

5.2. Label Range Message

   The default label range, Min VPI to Max VPI and Min VCI to Max VCI,
   is specified for each port by the Port Configuration or the All Ports
   Configuration messages.  When the protocol is initialized, before the
   transmission of any Label Range messages, the label range of each
   port will be set to the default label range. (The default label range
   is dependent upon the switch design and configuration and is not
   specified by the GSMP protocol.) The Label Range message allows the
   range of VPIs supported by a specified port, or the range of VCIs
   supported by a specified VPI on a specified port, to be changed.
   Each switch port must declare whether it supports the Label Range
   message in the Port Configuration or the All Ports Configuration
   messages.  The Label Range message is:

      Message Type = 33

   The Label Range message has the following format for the request and
   success 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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Port Session Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Q|V|x x|      Min VPI          |x x x x|       Max VPI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Min VCI            |           Max VCI             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Remaining VPIs         |        Remaining VCIs         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   Flags

        Q: Query
             If the Query flag is set in a request message, the switch
             must respond with the current range of valid VPIs, or the
             current range of valid VCIs on a specified VPI, according
             to the VPI/VCI flag. The current label range is not changed
             by a request message with the Query flag set. If the Query
             flag is zero, the message is requesting a label change
             operation.

        V: VPI/VCI
             If the VPI/VCI flag is set, the message refers to a range
             of VPIs only. The Min VCI and Max VCI fields are unused. If
             the VPI/VCI flag is zero the message refers to a range of
             VCIs on either one VPI or on a range of VPIs.

        x: Unused

   Min VPI
   Max VPI
             Specify a range of VPI values, Min VPI to Max VPI
             inclusive.  A single VPI may be specified with a Min VPI
             and a Max VPI having the same value.  In a request message,
             if the value of the Max VPI field is less than or equal to
             the value of the Min VPI field, the requested range is a
             single VPI with a value equal to the Min VPI field. Zero is
             a valid value.  In a request message, if the Query flag is
             set, and the VPI/VCI flag is zero, the Max VPI field
             specifies a single VPI and the Min VPI field is not used.
             The maximum valid value of these fields for both request
             and response messages is 0xFFF.

   Min VCI
   Max VCI
             Specify a range of VCI values, Min VCI to Max VCI
             inclusive.  A single VCI may be specified with a Min VCI
             and a Max VCI having the same value.  In a request message,
             if the value of the Max VCI field is less than or equal to
             the value of the Min VCI field, the requested range is a
             single VCI with a value equal to the Min VCI field. Zero is
             a valid value.  (However, VPI=0, VCI=0 is not available as
             a virtual channel connection as it is used as a special
             value in ATM to indicate an unassigned cell.)

   Remaining VPIs
   Remaining VCIs
             These fields are unused in the request message. In the



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             success response message and in the failure response
             message these fields give the maximum number of remaining
             VPIs and VCIs that could be requested for allocation on the
             specified port (after completion of the requested operation
             in the case of the success response). It gives the switch
             controller an idea of how many VPIs and VCIs it could
             request. The number given is the maximum possible given the
             constraints of the switch hardware. There is no implication
             that this number of VPIs and VCIs is available to every
             switch port.

   If the Query flag and the VPI/VCI flag are set in the request
   message, the switch must reply with a success response message
   containing the current range of valid VPIs that are supported by the
   port.  The Min VPI and Max VPI fields are not used in the request
   message.

   If the Query flag is set and the VPI/VCI flag is zero in the request
   message, the switch must reply with a success response message
   containing the current range of valid VCIs that are supported by the
   VPI specified by the Max VPI field.  If the requested VPI is invalid,
   a failure response must be returned indicating: "One or more of the
   specified input VPIs is invalid." The Min VPI field is not used in
   either the request or success response messages.

   If the Query flag is zero and the VPI/VCI flag is set in the request
   message, the Min VPI and Max VPI fields specify the new range of VPIs
   to be allocated to the input port specified by the Port field.
   Whatever the range of VPIs previously allocated to this port it
   should be increased or decreased to the specified value.

   If the Query flag and the VPI/VCI flag are zero in the request
   message, the Min VCI and Max VCI fields specify the range of VCIs to
   be allocated to each of the VPIs specified by the VPI range.
   Whatever the range of VCIs previously allocated to each of the VPIs
   within the specified VPI range on this port, it should be increased
   or decreased to the specified value.  The allocated VCI range must be
   the same on each of the VPIs within the specified VPI range.

   The success response to a Label Range message requesting a change of
   label range is a copy of the request message with the Remaining VPIs
   and Remaining VCIs fields updated to the new values after the Label
   Range operation.

   If the switch is unable to satisfy a request to change the VPI range,
   it must return a failure response message with the Code field set to
   "Cannot support requested VPI range." In this failure response




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   message the switch must use the Min VPI and Max VPI fields to suggest
   a VPI range that it would be able to satisfy.

   If the switch is unable to satisfy a request to change the VCI range
   on all VPIs within the requested VPI range, it must return a failure
   response message with the Code field set to "Cannot support requested
   VCI range on all requested VPIs." In this failure response message
   the switch must use the Min VPI, Max VPI, Min VCI, and Max VCI fields
   to suggest a VPI and VCI range that it would be able to satisfy.

   In all other failure response messages for the label range operation
   the switch must return the values of Min VPI, Max VPI, Min VCI, and
   Max VCI from the request message.

   While switches can typically support all 256 or 4096 VPIs the VCI
   range that can be supported is often more constrained. Often the Min
   VCI must be 0 or 32. Typically all VCIs within a particular VPI must
   be contiguous.  The hint in the failure response message allows the
   switch to suggest a label range that it could satisfy in view of its
   particular architecture.

   While the Label Range message is defined to specify both a range of
   VPIs and a range of VCIs within each VPI, the most likely use is to
   change either the VPI range or the range of VCIs within a single VPI.
   It is possible for a VPI to be valid but to be allocated no valid
   VCIs. Such a VPI could be used for a virtual path connection but to
   support virtual channel connections it would need to be allocated a
   range of VCIs.

   A Label Range request message may be issued regardless of the Port
   Status or the Line Status of the target switch port. If the Port
   field of the request message contains an invalid port (a port that
   does not exist or a port that has been removed from the switch) a
   failure response message must be returned with the Code field set to,
   "One or more of the specified ports does not exist."


6. State and Statistics Messages

   The state and statistics messages permit the controller to request
   the values of various hardware counters associated with the switch
   input and output ports, virtual path connections, virtual channel
   connections, and QoS Classes.  They also permit the controller to
   request the connection state of a switch input port.  The Connection
   Activity message is used to determine whether one or more specific
   virtual channel connections or virtual path connections have recently
   been carrying traffic.  The Statistics message is used to query the
   various port, connection, and QoS class traffic and error counters.



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   The Report Connection State message is used to request an input port
   to report the connection state for a single virtual channel
   connection, a single virtual path connection, or for the entire input
   port.

6.1 Connection Activity Message

   The Connection Activity message is used to determine whether one or
   more specific virtual channel connections or virtual path connections
   have recently been carrying traffic. The Connection Activity message
   contains one or more Activity Records. Each Activity Record is used
   to request and return activity information concerning a single
   virtual channel connection or virtual path connection.  Each virtual
   channel connection is specified by its input port, input VPI, and
   input VCI. Each virtual path connection is specified by its input
   port and input VPI. These are specified in the Input Port, Input VPI,
   and Input VCI fields of each Activity Record.  Two forms of activity
   detection are supported. If the switch supports per connection
   traffic accounting, the current value of the traffic counter for each
   specified virtual channel connection or virtual path connection must
   be returned. The units of traffic counted are not specified but will
   typically be either cells or frames.  The controller must compare the
   traffic counts returned in the message with previous values for each
   of the specified connections to determine whether each connection has
   been active in the intervening period.  If the switch does not
   support per connection traffic accounting, but is capable of
   detecting per connection activity by some other unspecified means,
   the result may be indicated for each connection using the Flags
   field. The Connection Activity message is:

      Message Type = 48

   The Connection Activity 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Number of Records       |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                       Activity Records                        ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   Number of Records
             Field specifies the number of Activity Records to follow.
             The number of Connection Activity records in a single
             Connection Activity message must not cause the packet
             length to exceed the maximum transmission unit defined by
             the encapsulation.

   Each Activity Record has the following format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Input Port                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V|C|A|x|      Input VPI        |          Input VCI            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                         Traffic Count                         +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Input Port
             Identifies the port number of the input port on which the
             connection of interest arrives in order to identify the
             connection (regardless of whether the traffic count for the
             connection is maintained on the input port or the output
             port).

   Input VPI
   Input VCI
             Fields identify the specific virtual path connection or
             virtual channel connection for which statistics are being
             requested. For a virtual path connection the Input VCI
             field is not used.

   Flags

        V: Valid Record
             In the success response message the Valid Record flag is
             used to indicate an invalid Activity Record. The flag must
             be zero if any of the fields in this Activity Record are
             invalid, if the input port specified by the Input Port
             field does not exist, or if the specified connection does
             not exist. If the Valid Record flag is zero in a success
             response message, the Counter flag, the Activity flag, and
             the VC Traffic Count field are undefined. If the Valid
             Record flag is set, the Activity Record is valid, and the
             Counter and Activity flags are valid. The Valid Record flag
             is not used in the request message.




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        C: Counter
             In a success response message, if the Valid Record flag is
             set, the Counter flag, if zero, indicates that the value in
             the VC Traffic Count field is valid.  If set, it indicates
             that the value in the Activity flag is valid. The Counter
             flag is not used in the request message.

        A: Activity
             In a success response message, if the Valid Record and
             Counter flags are set, the Activity flag, if set, indicates
             that there has been some activity on this connection since
             the last Connection Activity message for this connection.
             If zero, it indicates that there has been no activity on
             this connection since the last Connection Activity message
             for this connection. The Activity flag is not used in the
             request message.

        x: Unused

   Traffic Count
             Field is not used in the request message.  In the success
             response message, if the switch supports per connection
             traffic counting, the Traffic Count field must be set to
             the value of a free running, connection specific, 64-bit
             traffic counter counting traffic flowing across the
             specified connection.  The value of the traffic counter is
             not modified by reading it.  If per connection traffic
             counting is supported, the switch must report the
             Connection Activity result using the traffic count rather
             than using the Activity flag.

   The format of the failure response is the same as the request message
   with the Number of Records field set to zero and no VC Activity
   records returned in the message. If the switch is incapable of
   detecting per connection activity, a failure response must be
   returned indicating, "The specified request is not implemented on
   this switch."

6.2 Statistics Messages

   The Statistics messages are used to query the various port,
   connection, and QoS class traffic and error counters.

   The Statistics request 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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |          VPI          |              VCI              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      QoS Class Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   VPI
   VCI
             Fields identify the specific virtual path connection or
             virtual channel connection for which statistics are being
             requested.  For a virtual path connection the Input VCI
             field is not used.  For requests that do not require a
             virtual path connection or virtual channel connection to be
             specified, the VPI and VCI fields are not used.

   QoS Class Identifier
             Field identifies the QoS class for which statistics are
             being requested. This field is only used if the QoS Class
             Establishment message defined in section 9.4 is
             implemented.

   The success response for the Statistics 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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | zero  |          VPI          |              VCI              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      QoS Class Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                       Input Cell Count                        +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                       Input Frame Count                       +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                    Input Cell Discard Count                   +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                   Input Frame Discard Count                   +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                     Input HEC Error Count                     +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                  Input Invalid VPI/VCI Count                  +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                       Output Cell Count                       +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                      Output Frame Count                       +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                   Output Cell Discard Count                   +
   |                                                               |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                  Output Frame Discard Count                   +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port
   VPI/VCI
   QoS Class Identifier
             Fields are the same as those of the request message.

   Input Cell Count
   Output Cell Count
             Give the value of a free running 64-bit counter counting
             cells arriving at the input or departing from the output
             respectively.

   Input Frame Count
   Output Frame Count
             Give the value of a free running 64-bit counter counting
             frames (packets) arriving at the input or departing from
             the output respectively.

   Input Cell Discard Count
   Output Cell Discard Count
             Give the value of a free running 64-bit counter counting
             cells discarded due to queue overflow on an input port or
             on an output port respectively.

   Input Frame Discard Count
   Output Frame Discard Count
             Give the value of a free running 64-bit counter counting
             frames discarded due to congestion on an input port or on
             an output port respectively.

   HEC Error Count
             Gives the value of a free running 64-bit counter counting
             cells discarded due to header checksum errors on arrival at
             an input port.

   Invalid VPI/VCI Count
             Gives the value of a free running 64-bit counter counting
             cells discarded because their VPI/VCI is invalid on arrival
             at an input port. For a virtual channel connection an
             incoming VPI/VCI is invalid if no connection is currently
             established having that value of VPI/VCI. For a virtual
             path connection an incoming VPI is invalid if no connection
             is currently established having that value of VPI.



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6.2.1 Port Statistics Message

   The Port Statistics message requests the statistics for the switch
   port specified in the Port field. The contents of the VPI/VCI and the
   QoS Class Identifier fields in the Port Statistics request message
   are ignored. All of the count fields in the success response message
   refer to per-port counts regardless of the connection or QoS class to
   which the cells belong.  Any of the count fields in the success
   response message not supported by the port must be set to zero. The
   Port Statistics message is:

      Message Type = 49

6.2.2 Connection Statistics Message

   The Connection Statistics message requests the statistics for the
   virtual channel connection specified in the VPI/VCI field, or the
   virtual path connection specified in the VPI field, that arrives on
   the switch input port specified in the Port field, regardless of the
   QoS class to which the cells belong. All of the count fields in the
   success response message refer only to the specified connection.  The
   HEC Error Count and Invalid VPI/VCI Count fields are not connection
   specific and must be set to zero. Any of the other count fields not
   supported on a per connection basis must be set to zero in the
   success response message. The Connection Statistics message is:

      Message Type = 50

6.2.3 QoS Class Statistics Message

   The QoS Class Statistics message requests the statistics for the QoS
   class specified by the QoS Class Identifier field that arrives on the
   switch input port specified in the Port field, regardless of the
   connection to which the cells belong. The QoS Statistics message is
   only used if the QoS Class Establishment message defined in section
   9.4 is implemented.  The contents of the VPI/VCI fields in the QoS
   Class Statistics request message are ignored. All of the count fields
   in the success response message refer only to the specified QoS
   class.  The HEC Error Count and Invalid VPI/VCI Count fields are not
   specific to a QoS class and must be set to zero. Any of the other
   count fields not supported on a per QoS class basis must be set to
   zero in the success response message. The QoS Class Statistics
   message is:

      Message Type = 51






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6.3 Report Connection State Message

   The Report Connection State message is used to request an input port
   to report the connection state for a single virtual channel
   connection, a single virtual path connection, or for the entire input
   port. The Report Connection State message is:

      Message Type = 52

   The Report Connection State request message has the following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    | Message Type  |    Result     |     Code      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Transaction Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Input Port                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|V|x x|       Input VPI       |          Input VCI            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Input Port
             Identifies the port number of the input port for which the
             connection state is being requested.

   Flags

        A: All Connections
             If the All Connections flag is set, the message requests
             the connection state for all virtual path connections and
             virtual channel connections that arrive at the input port
             specified by the Input Port field. In this case the Input
             VPI and Input VCI fields and the VPI/VCI flag are unused.

        V: VPI/VCI
             If the All Connections flag is zero and the VPI/VCI flag is
             set, the message requests the connection state for the
             virtual path connection that arrives at the input port
             specified by the Input Port and Input VPI fields.  If the
             specified Input VPI identifies a virtual path connection
             (i.e. a single switched virtual path) the state for that
             connection is requested.  If the specified Input VPI
             identifies a virtual path containing virtual channel
             connections, the message requests the connection state for
             all virtual channel connections that belong to the
             specified virtual path. The Input VCI field is not used.



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             If the All Connections flag is zero and the VPI/VCI flag is
             also zero, the message requests the connection state for
             the virtual channel connection that arrives at the input
             port specified by the Port, Input VPI and Input VCI fields.

             x: Unused.

   Input VPI
   Input VCI
             Fields identify the specific virtual path connection, the
             specific virtual path, or the specific virtual channel
             connection for which connection state is being requested.
             For a virtual path connection (switched as a single virtual
             path connection) or a virtual path (switched as one or more
             virtual channel connections within the virtual path) the
             Input VCI field is not used.  For requests that do not
             require a virtual path connection or virtual channel
             connection to be specified, the Input VPI and Input VCI
             fields are not used.

   The Report Connection State 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Input Port                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                       Connection Records                      ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Input Port
             Is the same as the Input Port field in the request message.
             It identifies the port number of the input port for which
             the connection state is being reported.

   Sequence Number
             In the case that the requested connection state cannot be
             reported in a single success response message, each
             successive success response message in reply to the same



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             request message must increment the Sequence Number. The
             Sequence Number of the first success response message, in
             response to a new request message, must be zero.

   Connection Records
             Each success response message must contain one or more
             Connection Records. Each Connection Record specifies a
             single point-to-point or point-to-multipoint virtual path
             connection or virtual channel connection. The number of
             Connection Records in a single Report Connection State
             success response must not cause the packet length to exceed
             the maximum transmission unit defined by the encapsulation.
             If the requested connection state cannot be reported in a
             single success response message, multiple success response
             messages must be sent. All success response messages that
             are sent in response to the same request message must have
             the same Input Port and Transaction Identifier fields as
             the request message. A single Connection Record must not be
             split across multiple success response messages. The More
             flag of the last Connection Record in a success response
             message indicates whether the response to the request has
             been completed or whether one or more further success
             response messages should be expected in response to the
             same request message.

   Each Connection Record has the following format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|V|P|M|       Input VPI       |          Input VCI            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                      Output Branch Records                    ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Flags

        A: All Connections
        V: VPI/VCI
             For the first Connection Record in each success response
             message the All Connections and the VPI/VCI flags must be
             the same as those of the request message. For successive
             Connection Records in the same success response message
             these flags are not used.

        P: VPC
             The VPC flag, if set, indicates that the Connection Record
             refers to a virtual path connection.  If zero, it indicates



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             that the Connection Record refers to a virtual channel
             connection.

        M: More
             If the More flag is set, it indicates that another
             Connection Record, in response to the same request message,
             will follow either in the same success response message or
             in a successive success response message. If the More flag
             is zero it indicates that this is the last Connection
             record in this success response message and that no further
             success response messages will be sent in response to the
             current request message. It indicates that the response to
             the request message is now complete.

   Input VPI
   Input VCI
             The input VPI and VCI of the connection specified in this
             Connection Record. If this Connection Record specifies a
             virtual path connection (the VPC flag is set) the Input VCI
             field is unused.

   Output Branch Records
             Each Connection Record must contain one or more Output
             Branch Records. Each Output Branch Record specifies a
             single output branch belonging to the connection identified
             by the Input VPI and Input VCI fields of the Connection
             Record. A point-to-point connection will require only a
             single Output Branch Record. A point-to-multipoint
             connection will require multiple Output Branch Records. The
             last Output Branch Record of each Connection Record is
             indicated by the Last Branch flag of the Output Branch
             Record. If a point-to-multipoint connection has more output
             branches than can fit in a single Connection Record
             contained within a single success response message, that
             connection may be reported using multiple Connection
             Records in multiple success response messages.

   Each Output Branch Record has the following format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Output Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|x x x|       Output VPI      |          Output VCI           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Output Port
             The output port of the switch to which this output branch
             is routed.



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   Flags

        L: Last Branch
             The Last Branch flag, if set, indicates that this is the
             last Output Branch Record of this Connection Record. If
             zero, it indicates that one or more further Output Branch
             Records are to follow. If this is the last Output Branch
             Record in the message and the Last Branch flag is zero,
             further output branches belonging to the same connection
             will be given in another Connection Record. This Connection
             Record will be the first Connection Record in the next
             success response message. This Connection Record must have
             the same Input VPI and Input VCI values as the current
             Connection Record.

             x: Unused.

   Output VPI
   Output VCI
             The output VPI and VCI of the output branch specified in
             this Output Branch Record.  If this Output Branch Record is
             part of a Connection Record that specifies a virtual path
             connection (the VPC flag is set) the Output VCI field is
             unused.

   A Report Connection State request message may be issued regardless of
   the Port Status or the Line Status of the target switch port.

   If the Input Port of the request message is valid, and the All
   Connections flag is set, but there are no connections established on
   that port, a failure response message must be returned with the code
   field set to, "Failure specific to the particular message type." For
   the Report Connection State message, this failure code indicates that
   no connections matching the request message were found.  This failure
   message should also be returned if the Input Port of the request
   message is valid, the All Connections flag is zero, and no
   connections are found on that port matching the specified virtual
   path connection, virtual path, or virtual channel connection.


7. Configuration Messages

   The configuration messages permit the controller to discover the
   capabilities of the switch. Three configuration request messages have
   been defined: Switch, Port, and All Ports.

   All configuration request 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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7.1 Switch Configuration Message

   The Switch Configuration message requests the global (non port-
   specific) configuration for the switch. The Switch Configuration
   message is:

      Message Type = 64

   The Port field is not used in the request message.

   The Switch 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Firmware Version Number    |          Window Size          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Switch Type          |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                          Switch Name                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Firmware Version Number
             The version number of the switch control firmware
             installed.

   Window Size
             The maximum number of unacknowledged request messages that
             may be transmitted by the controller without the
             possibility of loss.  This field is used to prevent request
             messages being lost in the switch because of overflow in
             the receive buffer. The field is a hint to the controller.
             If desired, the controller may experiment with higher and



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             lower window sizes to determine heuristically the best
             window size.

   Switch Type
             A 16-bit field allocated by the manufacturer of the switch.
             (For these purposes the manufacturer of the switch is
             assumed to be the organization identified by the OUI in the
             Switch Name field.) The Switch Type identifies the product.
             When the Switch Type is combined with the OUI from the
             Switch Name the product is uniquely identified. Network
             Management may use this identification to obtain product
             related information from a database.

   Switch Name
             A 48-bit quantity that is unique within the operational
             context of the device. A 48-bit IEEE 802 MAC address, if
             available, may be used as the Switch Name. The most
             significant 24 bits of the Switch Name must be an
             Organizationally Unique Identifier (OUI) that identifies
             the manufacturer of the switch.

7.2 Port Configuration Message

   The Port Configuration message requests the switch for the
   configuration information of a single switch port. The Port field in
   the request message specifies the port for which the configuration is
   requested.  The Port Configuration message is:

      Message Type = 65.

   The Port Configuration success response 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                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Port Session Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V|M|L|R|      Min VPI          |Q|x x x|       Max VPI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Min VCI            |           Max VCI             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Receive Cell Rate                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Transmit Cell Rate                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Port Status  |   Port Type   |  Line Status  |  Priorities   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Physical Slot Number      |     Physical Port Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port
             The switch port to which the configuration information
             refers. Configuration information relating to both the
             input and the output sides of the switch port is given.
             Port numbers are 32 bits wide and allocated by the switch.
             The switch may choose to structure the 32 bits into
             subfields that have meaning to the physical structure of
             the switch hardware (e.g.  physical slot and port). This
             structure may be indicated in the Physical Slot Number and
             Physical Port Number fields.

   Flags

        V: VP Switching
             The VP Switching flag, if set, indicates that this input
             port is capable of supporting virtual path switching. Else,
             if zero, it indicates that this input port is only capable
             of virtual channel switching.

        M: Multicast Labels
             The Multicast Labels flag, if set, indicates that this
             output port is capable of labelling each output branch of a
             point-to-multipoint tree with a different label. If zero,
             it indicates that this output port is not able to label



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             each output branch of a point-to-multipoint tree with a
             different label.

        L: Logical Multicast
             The Logical Multicast flag, if set, indicates that this
             output port is capable of supporting more than a single
             branch from any point-to-multipoint connection.  This
             capability is often referred to as logical multicast.  If
             zero, it indicates that this output port can only support a
             single output branch from each point-to-multipoint
             connection.

        R: Label Range
             The Label Range flag, if set, indicates that this switch
             port is capable of reallocating its VPI label range or its
             VCI label range and therefore accepts the Label Range
             message. Else, if zero, it indicates that this port does
             not accept Label Range messages.

        Q: QoS
             The QoS flag, if set, indicates that this switch port is
             capable of handling the Quality of Service messages defined
             in section 9 of this specification.  Else, if zero, it
             indicates that this port does not accept the Quality of
             Service messages.

        x: Unused

   Min VPI
             The default minimum value of dynamically assigned incoming
             VPI that the connection table on the input port supports
             and that may be controlled by GSMP. This value is not
             changed as a result of the Label Range message.

   Max VPI
             The default maximum value of dynamically assigned incoming
             VPI that the connection table on the input port supports
             and that may be controlled by GSMP.  This value is not
             changed as a result of the Label Range message.

             At power-on, after a hardware reset, and after the Reset
             Input Port function of the Port Management message, the
             input port must handle all values of VPI within the range
             Min VPI to Max VPI inclusive and GSMP must be able to
             control all values within this range.  It should be noted
             that the range Min VPI to Max VPI refers only to the
             incoming VPI range that can be supported by the associated
             port. No restriction is placed on the values of outgoing



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             VPIs that may be written into the cell header. If the
             switch does not support virtual paths it is acceptable for
             both Min VPI and Max VPI to specify the same value, most
             likely zero.

             Use of the Label Range message allows the range of VPIs
             supported by the port to be changed. However, the Min VPI
             and Max VPI fields in the Port Configuration and All Ports
             Configuration messages always report the same default
             values regardless of the operation of the Label Range
             message.

   Min VCI
             The default minimum value of dynamically assigned incoming
             VCI that the connection table on the input port can support
             and may be controlled by GSMP. This value is not changed as
             a result of the Label Range message.

   Max VCI
             The default maximum value of dynamically assigned incoming
             VCI that the connection table on the input port can support
             and may be controlled by GSMP. This value is not changed as
             a result of the Label Range message.

             At power-on, after a hardware reset, and after the Reset
             Input Port function of the Port Management message, the
             input port must handle all values of VCI within the range
             Min VCI to Max VCI inclusive, for each of the virtual paths
             in the range Min VPI to Max VPI inclusive, and GSMP must be
             able to control all values within this range.  It should be
             noted that the range Min VCI to Max VCI refers only to the
             incoming VCI range that can be supported by the associated
             port on each of the virtual paths in the range Min VPI to
             Max VPI. No restriction is placed on the values of outgoing
             VCIs that may be written into the cell header.

             Use of the Label Range message allows the range of VCIs to
             be changed on each VPI supported by the port.  However, the
             Min VCI and Max VCI fields in the Port Configuration and
             All Ports Configuration messages always report the same
             default values regardless of the operation of the Label
             Range message.

             For a port over which the GSMP protocol is operating, the
             VCI of the GSMP control channel may or may not be reported
             as lying within the range Min VCI to Max VCI.  A switch
             should honor a connection request message that specifies




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             the VCI value of the GSMP control channel even if it lies
             outside the range Min VCI to Max VCI.

   Receive Cell Rate
             The maximum rate of cells that may arrive at the input port
             in cells/s.

   Transmit Cell Rate
             The maximum rate of cells that may depart from the output
             port in cells/s. (The transmit cell rate of the output port
             may be changed by the Set Transmit Cell Rate function of
             the Port Management message.)

   Port Status
             Gives the administrative state of the port. The defined
             values of the Port Status field are:

             Available:
                  Port Status = 1. The port is available to both send
                  and receive cells. When a port changes to the
                  Available state from any other administrative state,
                  all dynamically assigned virtual connections must be
                  cleared and a new Port Session Number must be
                  generated.

             Unavailable:
                  Port Status = 2. The port has intentionally been taken
                  out of service. No cells will be transmitted from this
                  port.  No cells will be received by this port.

             Internal Loopback:
                  Port Status = 3. The port has intentionally been taken
                  out of service and is in internal loopback: cells
                  arriving at the output port from the switch fabric are
                  looped through to the input port to return to the
                  switch fabric. All of the ATM functions of the input
                  port above the physical layer, e.g. header
                  translation, are performed upon the looped back cells.

             External Loopback:
                  Port Status = 4. The port has intentionally been taken
                  out of service and is in external loopback: cells
                  arriving at the input port from the external
                  communications link are immediately looped back to the
                  communications link at the physical layer without
                  entering the input port. None of the ATM functions of
                  the input port above the physical layer are performed
                  upon the looped back cells.



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             Bothway Loopback:
                  Port Status = 5. The port has intentionally been taken
                  out of service and is in both internal and external
                  loopback.

             The Port Status of the port over which the GSMP session
             controlling the switch is running, must be declared
             Available. The controller will ignore any other Port status
             for this port. The Port Status of switch ports after
             power-on initialization is not defined by GSMP.

   Port Type
             The type of physical transmission interface for this port.
             The values for this field are defined by the atmIfType
             object specified in the Ipsilon IP Switch MIB [IpsilonMIB].

   Line Status
             The status of the physical transmission medium connected to
             the port. The defined values of the Line Status field are:

             Up:
                  Line Status = 1. The line is able to both send and
                  receive cells.  When the Line Status changes to Up
                  from either the Down or Test states, a new Port
                  Session Number must be generated.

             Down:
                  Line Status = 2. The line is unable either to send or
                  receive cells or both.

             Test:
                  Line Status = 3. The port or line is in a test mode,
                  for example, power-on test.

   Priorities
             The number of different priority levels that this output
             port can assign to virtual connections.  Zero is invalid in
             this field. If an output port is able to support "Q"
             priorities, the highest priority is numbered zero and the
             lowest priority is numbered "Q-1". 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 may be assumed that for
             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.



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   Physical Slot Number
             The physical location of the slot in which the port is
             located. It is an unsigned 16-bit integer that can take any
             value except 0xFFFF. The value 0xFFFF is used to indicate
             "unknown." The Physical Slot Number is not used by the GSMP
             protocol. It is provided to assist network management in
             functions such as logging, port naming, and graphical
             representation.

   Physical Port Number
             The physical location of the port within the slot in which
             the port is located. It is an unsigned 16-bit integer that
             can take any value except 0xFFFF. The value 0xFFFF is used
             to indicate "unknown." The Physical Port Number is not used
             by the GSMP protocol. It is provided to assist network
             management in functions such as logging, port naming, and
             graphical representation.

             There must be a one to one mapping between Port Number and
             the Physical Slot Number and Physical Port Number
             combination. Two different Port Numbers must not yield the
             same Physical Slot Number and Physical Port Number
             combination. The same Port Number must yield the same
             Physical Slot Number and Physical Port Number within a
             single GSMP session.  If both Physical Slot Number and
             Physical Port Number indicate "unknown" the physical
             location of switch ports may be discovered by looking up
             the product identity in a database to reveal the physical
             interpretation of the 32-bit Port Number.

7.3 All Ports Configuration Message

   The All Ports Configuration message requests the switch for the
   configuration information of all of its ports. The All Ports
   Configuration message is:

      Message Type = 66

   The Port field is not used in the request message.

   The All Ports Configuration success response 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                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Number of Records       |      Port Record Length       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                          Port Records                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Number of Records
             Field gives the total number of Port Records to be returned
             in response to the All Ports Configuration request message.
             The number of port records in a single All Ports
             Configuration success response must not cause the packet
             length to exceed the maximum transmission unit defined by
             the encapsulation. If a switch has more ports than can be
             sent in a single success response message it must send
             multiple success response messages. All success response
             messages that are sent in response to the same request
             message must have the same Transaction Identifier as the
             request message and the same value in the Number of Records
             field.  All success response messages that are sent in
             response to the same request message, except for the last
             message, must have the result field set to "More." The last
             message, or a single success response message, must have
             the result field set to "Success." All Port records within
             a success response message must be complete, i.e. a single
             Port record must not be split across multiple success
             response messages.

   Port Record Length
             Field gives the length of each port record in bytes. This
             is currently 32 but the Port Record Length field allows for
             the future definition of further fields at the end of the
             port record while preserving compatibility with earlier
             versions of the protocol.

   Port Records
             Follow in the remainder of the message. Each port record
             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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Port                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Port Session Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V|M|L|R|      Min VPI          |Q|x x x|       Max VPI         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Min VCI            |           Max VCI             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Receive Cell Rate                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Transmit Cell Rate                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Port Status  |   Port Type   |  Line Status  |  Priorities   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Physical Slot Number      |     Physical Port Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The definition of the fields in the Port Record is exactly the same
   as that of the Port Configuration message.


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."

9.6 QoS Connection Management Message

   The QoS Connection Management message is used by the controller to
   establish and modify virtual channel connections and virtual path
   connections across the switch which require QoS parameters to be
   specified. The functionality of the QoS Connection Management message
   is identical to that of the Add Branch connection management message
   with the additional specification of QoS parameters.  No specific QoS
   connection release messages are defined. QoS connections may be
   released with the Delete Tree, Delete All, and Delete Branches
   messages defined in Section 4, "Connection Management Messages." When
   a QoS connection is released, all associated QoS resources are
   released.

   There are three styles of connection with specified QoS parameters:

   QoS Connection:
      This connection style specifies its own individual QoS parameters
      and is routed independently to the waiting room and output port
      specified in the QoS Connection Management message. It is not a
      member of a QoS class. Each output branch of a point-to-multipoint
      QoS connection may specify its own QoS parameters which may be
      different from all other output branches of that point-to-
      multipoint QoS connection, if the switch supports this capability.
      However, all output branches must specify identical connection
      policer parameters. A QoS Connection Management message requesting
      this style of connection is identified by a QoS Class Identifier
      with the value 0xFFFFFFFF.





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   QoS Class Connection:
      This connection style does not specify its own individual QoS
      parameters. It is a member of a QoS class, and the QoS parameters
      are specified by the QoS class.  It is, however, routed
      independently to the waiting room and output port specified in the
      QoS Connection Management message.  Each output branch of a
      point-to-multipoint QoS Class Connection must use the same QoS
      parameters. A QoS Connection Management message requesting this
      style of connection will have a valid QoS Class Identifier and a
      valid Scheduler Identifier.

   QoS Class Member:
      This connection style does not specify its own individual QoS
      parameters. It is a member of a QoS class, and the QoS parameters
      are specified by the QoS class.  The QoS class also specifies the
      waiting room and output port to which all members of the class are
      routed. This style of connection does not support point-to-
      multipoint connections. A QoS Connection Management message
      requesting this style of connection will have a valid QoS Class
      Identifier and a Scheduler Identifier with the value 0xFFFF.

   To request a virtual channel connection with specified QoS
   parameters, the Virtual Channel Connection (VCC) QoS Connection
   Management message is:

      Message Type = 100.

   To request a virtual path connection with specified QoS parameters,
   the Virtual Path Connection (VPC) QoS Connection Management message
   is:

      Message Type = 101.

   The QoS Connection Management message has the following format for
   both request and response messages:
















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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 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       |     Scheduler Identifier      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      QoS Class Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Regulator   | Excess Action |       Connection Weight       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S|A|x x x x x x|   Reserved    |      Excess Scheduler Id      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                         UPC Parameters                        ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                      Regulator Parameters                     ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Port Session Number
   Input Port
   Input VPI
   Input VCI
   Output Port
   Output VPI
   Output VCI
   Number of Branches
             The definition of these fields is exactly the same as
             defined for the Add Branch message in Section 4.1,
             "Connection Management Messages."






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   M B C Flags
             The definition of the M, B, and C flags is exactly the same
             as defined in Section 4, "Connection Management Messages."
             They apply to the QoS Connection Management message exactly
             as defined for the Add Branch message.

   Q: QoS Profile Flag The QoS Profile flag is not used in the QoS
             Connection Management message.

   Scheduler Identifier
             For QoS Connection and QoS Class Connection styles, the
             Scheduler Identifier points to the waiting room, on the
             output port specified by the Output Port field, to which
             all conforming traffic on the connection should be routed.
             The values 0 -- 255 specify the default settings for the
             scheduler. Each of the default values maps directly to one
             of the scheduler priority levels. A Scheduler Identifier in
             the range 0 -- 255 may be used without first being
             established by a Scheduler Establishment message. All
             Scheduler Identifiers in the range 0x0100 to 0xFFFE must
             first be established by a Scheduler Establishment message.

             A Scheduler Identifier with a value of 0xFFFF indicates
             that a QoS Class Member connection style is being
             requested. In this connection style, the waiting room and
             output port are specified by reference to the QoS class
             specified by the QoS Class Identifier field. In this case
             the QoS Class Identifier field must contain a valid QoS
             Class Identifier.

   QoS Class Identifier
             For QoS Class Connection and QoS Class Member connection
             styles, the QoS Class Identifier specifies the QoS Class to
             which the connection belongs. It must first be established
             by a QoS Class Establishment message and must have a value
             greater than 0 and less than 0xFFFFFFFF.

             A QoS Class Identifier with a value of 0xFFFFFFFF indicates
             that a connection of style "QoS Connection" is being
             requested. In this connection style, the connection does
             not belong to a QoS class. All QoS parameters are specified
             by the QoS Connection Management message and apply only to
             the specified connection.

   Regulator
   Excess Action
             The Regulator and Excess Action parameters are only used in
             connection requests of style "QoS Connection." The



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             definition of these fields in the QoS Connection Management
             message is exactly the same as defined for the QoS Class
             Establishment message with the exception that they apply to
             an individual connection rather than to an entire QoS
             class.

   Connection Weight
             This field is only used in connections of style "QoS
             Connection" and "QoS Class Connection." For QoS Class
             Member style connections, the QoS Class Weight parameter of
             the QoS Class Establishment message should be used to
             assign a weight to the QoS Class.

             If bit 0 of the Scheduler Flags field of the QoS
             Configuration message indicates that weighted service may
             be applied to a connection, the Connection Weight parameter
             specifies the share of the bandwidth available to the
             waiting room that should be given to this connection.

             The Connection 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 = Connection Weight * 2**(-16)

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

             For connections of style "QoS Class Connection," if the
             Regulator function of the QoS Class is specified as None,
             or Policer, the Connection Weight should be applied to the
             waiting room pointed to by the Scheduler Identifier field
             in the QoS Connection Management message. If the Regulator
             function of the QoS Class is specified as Shaper, the
             Connection Weight should be applied to the waiting room
             pointed to by the Excess Scheduler Id field in the QoS
             Connection Management message.

             For connections of style "QoS Connection," if the Regulator
             field of the QoS Connection Management message specifies
             None, or Policer, the Connection Weight should be applied
             to the waiting room pointed to by the Scheduler Identifier
             field. If the Regulator field of the QoS Connection



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             Management message specifies Shaper, the Connection Weight
             should be applied to the waiting room pointed to by the
             Excess Scheduler Id field.

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

   QoS Flags

        S: Selective Discard
             If the Selective Discard flag is set, only cells with the
             Cell Loss Priority (CLP) bit set will be subject to the
             discard mechanism when the number of cells in the waiting
             room exceeds the Discard Threshold.  If the Selective
             Discard flag is zero, all cells (CLP=0 and CLP=1) will be
             subject to the discard mechanism when the number of cells
             in the waiting room exceeds the Discard Threshold.
             Selective discard can be combined with packet discard. In
             this case only packets in which at least one cell has the
             CLP bit set will be subject to the discard mechanism.

        A: All Branches
             For a QoS Connection Management message that specifies a
             point-to-multipoint connection, if the All Branches flag is
             set, all branches of the point-to-multipoint connection
             must be set to the QoS parameters specified in the message.
             If the All Branches flag is zero, only the single output
             branch specified in the message should be set to the QoS
             parameters specified in the message. For a QoS Connection
             Management message that specifies a point-to-point
             connection, the All Branches flag is not used.

        x: Unused

   Excess Scheduler Id
             For connections of style "QoS Connection" and "QoS Class
             Connection," 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 routed. The
             values 0 -- 255 specify the default settings for the
             scheduler. Each of the default values maps directly to one
             of the scheduler priority levels. An Excess Scheduler Id in
             the range 0 -- 255 may be used without first being
             established by a Scheduler Establishment message. All





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             values of Excess Scheduler Id in the range 0x0100 to 0xFFFE
             must first be established by a Scheduler Establishment
             message.

             If this field is not used it should be set to 0xFFFF.  The
             Excess Scheduler Id must not point to the same waiting room
             on the same output port as the Scheduler Identifier.

   UPC Parameters
             All connection styles may be subject to a Usage Parameter
             Control (UPC) function, also known as a connection policer.
             The policing function is applied to each individual
             connection before it is combined with other connections
             into a QoS class by the classifier function. A policing
             function applied to an entire QoS class is defined in the
             QoS Class Establishment message.

             The connection policer is defined by reference to the
             Generic Cell Rate Algorithm (GCRA) defined by the ATM Forum
             [af-tm-0056], although any equivalent policing algorithm
             may be used. The GCRA takes two parameters, the increment
             (I) and the limit (L). The reciprocal of the increment
             (1/I) specifies the rate being policed. The limit specifies
             the burst tolerance. (For comparison with the token bucket
             policer discussed in [Partridge], the size of the token
             bucket is given by L/I.)

             Two policers in series may be specified to permit the
             policing of both peak rate and average rate (also called
             sustainable rate). The parameters for the first policer are
             Increment-1 and Limit-1. For comparison with the ATM Forum
             specification these would be used to police the Peak Cell
             Rate (PCR) and Cell Delay Variation Tolerance (CDVT)
             respectively. The parameters for the second policer are
             Increment-2 and Limit-2. For comparison with the ATM Forum
             specification these would be used to police the Sustainable
             Cell Rate (SCR), and Burst Tolerance.  (The Burst Tolerance
             may be computed from the Maximum Burst Size [af-tm-0056].)

             There are two configurations in which the two policers may
             be connected in series.  In the All Cells configuration,
             all cells (cells with the Cell Loss Priority (CLP) bit set
             to zero and cells with the CLP bit set to one) are subject
             to the policing action of both policers in series. In the
             CLP Selective configuration, all cells, both CLP=0 and
             CLP=1, are policed by the first policer; but only cells





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             with CLP=0 are subject to policing by the second policer.
             Either tagging or discard may be specified for each of the
             policer configurations.

             The values of the parameters Increment and Limit in the UPC
             Parameters fields are given in terms of a time unit
             specified by the switch in the QoS Configuration Parameters
             message. The time unit is specified by the switch as a
             rate, the Scaling Factor, which gives the rate in cells per
             second that would result from an Increment parameter value
             of one. Thus to determine the value of the Increment
             parameter from the desired policed rate given in cells per
             second:

                Increment parameter = (Scaling_Factor)/(policed_rate)

             To determine the value of the Limit parameter from the
             desired Cell Delay Variation Tolerance (CDVT) given in
             seconds:

                Limit parameter = CDVT * Scaling_Factor

             To determine the value of the Limit parameter from the
             desired Burst Tolerance (BT) given in seconds:

                Limit parameter = BT * Scaling_Factor

             The Increment and Limit parameters are specified as 32-bit
             unsigned integers; so the choice of the Scaling Factor
             allows the switch to select the range and granularity of
             the policer parameters with respect to the line rate of the
             switch port.  For example, a SONET STS-3c (155.52 Mbps)
             switch port has a line rate of approximately 353 kcells/s.
             With a Scaling Factor value of 353,000,000 we can specify a
             policed rate slightly less than the line rate with a
             granularity of 0.1%. For a policed rate of 1 kbps we can
             still support a bucket size of 31 cells.

             The UPC Parameters 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Increment-1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Limit-1                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Increment-2                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Limit-2                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Reserved                     |C|A|x x x x x x|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Increment-1
             The increment parameter for the first policer, specified as
             a 32-bit unsigned integer.  A value of zero for the
             Increment-1 parameter is used to disable the first policer.
             In this case all cells will be considered to conform to the
             traffic parameters of the first policer.

   Limit-1
             The limit parameter for the first policer, specified as a
             32-bit unsigned integer.

   Increment-2
             The increment parameter for the second policer, specified
             as a 32-bit unsigned integer.  A value of zero for the
             Increment-2 parameter is used to disable the second
             policer.  In this case all cells will be considered to
             conform to the traffic parameters of the second policer.

   Limit-2
             The limit parameter for the second policer, specified as a
             32-bit unsigned integer.

   Flags

        C: Configuration
             If the Configuration flag is set, the policer should be set
             to the All Cells configuration. If the Configuration flag
             is zero, the policer should be set to the CLP Selective
             configuration.

             In the All Cells configuration, all cells (both CLP=0 and
             CLP=1) are subject to the policing action of both policers
             in series. In the CLP Selective configuration, all cells,
             both CLP=0 and CLP=1, are policed by the first policer; but



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             only cells with CLP=0 are subject to policing by the second
             policer. Either tagging or discard may be specified for
             each of the policer configurations.

        A: Action
             If the Action flag is zero, discard is required as the
             policing action. If the Action flag is set, tagging is
             required as the policing action.

             If tagging is selected in the All Cells configuration, any
             cell with CLP=0 in either policer, that the policer
             determines to be in excess of the specified policer
             parameters, will be changed to CLP=1. If discard is
             selected in the All Cells configuration, any cell (CLP=0 or
             CLP=1) in either policer, that the policer determines to be
             in excess of the specified policer parameters, will be
             discarded.

             In the CLP Selective configuration, the first policer is
             always set to discard any cell (CLP=0 or CLP=1) that it
             determines to be in excess of its specified policer
             parameters. If tagging is selected in the CLP Selective
             configuration, the second policer will change the CLP bit
             to CLP=1 of any cell that it determines to be in excess of
             its specified parameters. If discard is selected in the CLP
             Selective configuration, the second policer will discard
             any cell that it determines to be in excess of its
             specified parameters.

             To configure the policer for the conformance definitions
             specified by the ATM Forum [af-tm-0056] the following
             configurations are suggested:

                CBR.1:   One policer,     All Cells,        Discard
                VBR.1:   Two policers,    All Cells,        Discard
                VBR.2:   Two policers,    CLP Selective,    Discard
                VBR.3:   Two policers,    CLP Selective,    Tagging
                UBR.1:   One policer,     All Cells,        Discard
                UBR.2:   One policer,     All Cells,        Tagging.

        x: Unused

   Regulator Parameters
             Only connections of style "QoS Connection" require the
             Regulator Parameters to be specified in the QoS Connection
             Management message. For connections of style "QoS Class
             Connection" and "QoS Class Member" the Regulator Parameters
             are specified in the QoS Class Establishment message.



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             The Regulator Parameters are specified in a similar manner
             to the UPC parameters. If the regulator function is
             specified as Policing, a single GCRA policer is applied to
             all cells (both CLP=0 and CLP=1) on the connection. The
             policer takes two parameters: an increment, the Regulator
             Increment, and a limit, the Regulator Limit. The reciprocal
             of the increment (1/I) specifies the rate being policed.
             The limit (L) specifies the burst tolerance. (For
             comparison with the token bucket policer discussed in
             [Partridge], the size of the token bucket is given by L/I.)

             The Regulator Increment and Regulator Limit parameters are
             32-bit unsigned integers. Their values are determined in
             terms of the Scaling Factor specified by the switch in the
             QoS Configuration Parameters message. To determine the
             value of the Regulator Increment parameter from the desired
             policed rate given in cells per second:

                Regulator Increment = (Scaling_Factor)/(policed_rate)

             For a policed rate (r) the GCRA policer guarantees that
             over any time period T the amount of traffic determined by
             the policer to be conforming to the traffic parameters does
             not exceed:

                rT + L/I

             The value of the Regulator Limit may be determined from
             this relation.

             If the regulator function is specified as Shaping, only the
             Regulator Increment parameter is used. The Regulator Limit
             parameter is not used. The value of the Regulator Increment
             parameter is determined in terms of the Scaling Factor
             specified by the switch in the QoS Configuration Parameters
             message. To determine the value of the Regulator Increment
             parameter from the desired shaper rate, given in cells per
             second, on output from the shaper:

                Regulator Increment = (Scaling_Factor)/(shaper_rate)

             An Increment value of zero is used to disable the policer.
             In this case all cells on that connection will be
             considered to conform to the policer traffic parameters. A
             shaper given a Regulator Increment parameter of zero will
             perform no shaping function on that connection.

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

9.7 QoS Failure Response Codes

   A failure response message is formed by returning the request message
   that caused the failure with the Result field in the header
   indicating failure (Result = 4) and the Code field giving the failure
   code. The failure code specifies the reason for the switch being
   unable to satisfy the request message.  The following additional
   failure codes are defined for use in response to QoS messages.
   General failure codes are specified in Section 3.2, Failure Response
   Messages.

       128: Weighted scheduling within this waiting room is unavailable.
       129: This waiting room is unable to offer weighted sharing for a
              QoS class.
       130: This waiting room is unable to offer weighted sharing for a
              connection.
       131: Scheduler Identifier still in use.
       132: QoS Class Identifier still in use.
       133: Invalid QoS parameter.
       134: Insufficient QoS resources.
       135: Any point-to-multipoint connection arriving on this input
              port must use the same QoS parameters for all output
              branches.


10. Adjacency Protocol

   The adjacency protocol is used to synchronize state across the link,
   to agree on which version of the protocol to use, to discover the
   identity of the entity at the other end of a link, and to detect when
   it changes. GSMP is a hard state protocol.  It is therefore important
   to detect loss of contact between switch and controller, and to
   detect any change of identity of switch or controller.  No GSMP
   messages other than those of the adjacency protocol may be sent
   across the link until the adjacency protocol has achieved
   synchronization.







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10.1 Packet Format

   All GSMP messages belonging to the adjacency protocol have the
   following structure:

    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  |     Timer     |M|     Code    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Sender Name                          |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                         Receiver Name                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Sender Port                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Receiver Port                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sender Instance                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Receiver Instance                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
             In the adjacency protocol the Version field is used for
             version negotiation.  In a SYN message the Version field
             always contains the highest version understood by the
             sender.  A receiver receiving a SYN message with a version
             higher than understood will ignore that message.  A
             receiver receiving a SYN message with a version lower than
             its own highest version, but a version that it understands,
             will reply with a SYNACK with the version from the received
             SYN in its GSMP Version field. This defines the version of
             the GSMP protocol to be used while the adjacency protocol
             remains synchronized. All other messages will use the
             agreed version in the Version field.

             The version number for the version of the GSMP protocol
             defined by this specification is Version = 2.

   Message Type
             The adjacency protocol is:

                Message Type = 10





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   Timer
             The Timer field is used to inform the receiver of the timer
             value used in the adjacency protocol of the sender. The
             timer specifies the nominal time between periodic adjacency
             protocol messages. It is a constant for the duration of a
             GSMP session. The timer field is specified in units of
             100ms.

   M-Flag
             The M-Flag is used in the SYN message to indicate whether
             the sender is a master or a slave. If the M-Flag is set in
             the SYN message, the sender is a master.  If zero, the
             sender is a slave. The GSMP protocol is asymmetric, the
             controller being the master and the switch being the slave.
             The M-Flag prevents a master from synchronizing with
             another master, or a slave with another slave. If a slave
             receives a SYN message with a zero M-Flag, it must ignore
             that SYN message. If a master receives a SYN message with
             the M-Flag set, it must ignore that SYN message. In all
             other messages the M-Flag is not used.

   Code
             Field specifies the function of the message. Four Codes are
             defined for the adjacency protocol:

                SYN:     Code = 1
                SYNACK:  Code = 2
                ACK:     Code = 3
                RSTACK:  Code = 4.

   Sender Name
             For the SYN, SYNACK, and ACK messages, is the name of the
             entity sending the message. The Sender Name is a 48-bit
             quantity that is unique within the operational context of
             the device. A 48-bit IEEE 802 MAC address, if available,
             may be used for the Sender Name. If the Ethernet
             encapsulation is used the Sender Name must be the Source
             Address from the MAC header.  For the RSTACK message, the
             Sender Name field is set to the value of the Receiver Name
             field from the incoming message that caused the RSTACK
             message to be generated.

   Receiver Name
             For the SYN, SYNACK, and ACK messages, is the name of the
             entity that the sender of the message believes is at the
             far end of the link. If the sender of the message does not
             know the name of the entity at the far end of the link,
             this field should be set to zero. For the RSTACK message,



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             the Receiver Name field is set to the value of the Sender
             Name field from the incoming message that caused the RSTACK
             message to be generated.

   Sender Port
             For the SYN, SYNACK, and ACK messages, is the local port
             number of the link across which the message is being sent.
             For the RSTACK message, the Sender Port field is set to the
             value of the Receiver Port field from the incoming message
             that caused the RSTACK message to be generated.

   Receiver Port
             For the SYN, SYNACK, and ACK messages, is what the sender
             believes is the local port number for the link, allocated
             by the entity at the far end of the link.  If the sender of
             the message does not know the port number at the far end of
             the link, this field should be set to zero. For the RSTACK
             message, the Receiver Port field is set to the value of the
             Sender Port field from the incoming message that caused the
             RSTACK message to be generated.

   Sender Instance
             For the SYN, SYNACK, and ACK messages, is the sender's
             instance number for the link. It is used to detect when the
             link comes back up after going down or when the identity of
             the entity at the other end of the link changes. The
             instance number is a 32-bit number that is guaranteed to be
             unique within the recent past and to change when the link
             or node comes back up after going down. Zero is not a valid
             instance number. For the RSTACK message, the Sender
             Instance field is set to the value of the Receiver Instance
             field from the incoming message that caused the RSTACK
             message to be generated.

   Receiver Instance
             For the SYN, SYNACK, and ACK messages, is what the sender
             believes is the current instance number for the link,
             allocated by the entity at the far end of the link. If the
             sender of the message does not know the current instance
             number at the far end of the link, this field should be set
             to zero. For the RSTACK message, the Receiver Instance
             field is set to the value of the Sender Instance field from
             the incoming message that caused the RSTACK message to be
             generated.







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10.2 Procedure

   The adjacency protocol is described by the following rules and state
   tables.

   The rules and state tables use the following operations:

    o The "Update Peer Verifier" operation is defined as storing the
      values of the Sender Instance, Sender Port, and Sender Name fields
      from a SYN or SYNACK message received from the entity at the far
      end of the link.

    o The procedure "Reset the link" is defined as:

          1. Generate a new instance number for the link
          2. Delete the peer verifier (set to zero the values of Sender
             Instance, Sender Port, and Sender Name previously stored by
             the Update Peer Verifier operation)
          3. Send a SYN message
          4. Enter the SYNSENT state.

    o The state tables use the following Boolean terms and operators:

        A    The Sender Instance in the incoming message matches the
             value stored from a previous message by the "Update Peer
             Verifier" operation.

        B    The Sender Instance, Sender Port, and Sender Name fields in
             the incoming message match the values stored from a
             previous message by the "Update Peer Verifier" operation.

        C    The Receiver Instance, Receiver Port, and Receiver Name
             fields in the incoming message match the values of the
             Sender Instance, Sender Port, and Sender Name currently
             sent in outgoing SYN, SYNACK, and ACK messages.

        "&&" Represents the logical AND operation

        "||" Represents the logical OR operation

        "!" Represents the logical negation (NOT) operation.

    o A timer is required for the periodic generation of SYN, SYNACK,
      and ACK messages. The value of the timer is announced in the Timer
      field.  The period of the timer is unspecified but a value of one
      second is suggested.





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      There are two independent events: the timer expires, and a packet
      arrives. The processing rules for these events are:

         Timer Expires:   Reset Timer
                          If state = SYNSENT Send SYN
                          If state = SYNRCVD Send SYNACK
                          If state = ESTAB   Send ACK

          Packet Arrives:
              If incoming message is an RSTACK:
                  If (A && C && !SYNSENT) Reset the link
                  Else Discard the message.
              If incoming message is a SYN, SYNACK, or ACK:
                  Response defined by the following State Tables.
              If incoming message is any other GSMP message and state !=
                  ESTAB:
                  Discard incoming message.
                  If state = SYNSENT Send SYN (Note 1)
                  If state = SYNRCVD Send SYNACK (Note 1)

              Note 1: No more than two SYN or SYNACK messages should be
              sent within any time period of length defined by the
              timer.

    o State synchronization across a link is considered to be achieved
      when the protocol reaches the ESTAB state. All GSMP messages,
      other than adjacency protocol messages, that are received before
      synchronization is achieved will be discarded.

State Tables

State: SYNSENT

+======================================================================+
|     Condition      |                Action               | New State |
+====================+=====================================+===========+
|    SYNACK && C     |  Update Peer Verifier; Send ACK     |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|    SYNACK && !C    |            Send RSTACK              |  SYNSENT  |
+--------------------+-------------------------------------+-----------+
|        SYN         |  Update Peer Verifier; Send SYNACK  |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|        ACK         |            Send RSTACK              |  SYNSENT  |
+======================================================================+







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State: SYNRCVD

+======================================================================+
|     Condition      |                Action               | New State |
+====================+=====================================+===========+
|    SYNACK && C     |  Update Peer Verifier; Send ACK     |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|    SYNACK && !C    |            Send RSTACK              |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|        SYN         |  Update Peer Verifier; Send SYNACK  |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|   ACK && B && C    |              Send ACK               |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|  ACK && !(B && C)  |            Send RSTACK              |  SYNRCVD  |
+======================================================================+


State: ESTAB

+======================================================================+
|     Condition      |                Action               | New State |
+====================+=====================================+===========+
|   SYN || SYNACK    |           Send ACK (note 2)         |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|   ACK && B && C    |           Send ACK (note 3)         |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|  ACK && !(B && C)  |              Send RSTACK            |   ESTAB   |
+======================================================================+

   Note 2: No more than two ACKs should be sent within any time period
   of length defined by the timer. Thus, one ACK must be sent every time
   the timer expires. In addition, one further ACK may be sent between
   timer expirations if the incoming message is a SYN or SYNACK. This
   additional ACK allows the adjacency protocol to reach synchronization
   more quickly.

   Note 3: No more than one ACK should be sent within any time period of
   length defined by the timer.

10.3 Loss of Synchronization

   If after synchronization is achieved, no valid GSMP messages are
   received in any period of time in excess of three times the value of
   the Timer field announced in the incoming adjacency protocol
   messages, loss of synchronization may be declared.

   The preferred procedure for a switch to use when it looses
   synchronization with its active controller is to attempt to establish



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   synchronization with (one of) its backup controller(s).  However, in
   this preferred approach, it must not reset its state until it
   achieves synchronization with a backup controller.  This means that
   if, before achieving synchronization with a backup controller, it
   regains synchronization with its original controller, it may continue
   the original session (and cease attempting to establish
   synchronization with a backup controller). If synchronization with
   the original session is regained it is the responsibility of the
   controller to ensure consistent state between the switch and
   controller.

   While the above is the preferred procedure, it is also the case that
   the simplest procedure when declaring loss of synchronization with
   the active controller is to reset the switch state, and start
   searching for a controller.  This simple procedure is legitimate.

11. Summary of Failure Response Codes

   The following list gives a summary of the failure codes defined for
   failure response messages:

        1: Unspecified reason not covered by other failure codes.
        2: Invalid request message.
        3: The specified request is not implemented on this switch.
        4: Invalid Port Session Number.
        5: One or more of the specified ports does not exist.
        6: One or more of the specified ports is down.
        7: Unused. (This failure code has been replaced by failure codes
             18--21.)
        8: The specified connection does not exist.
        9: The specified branch does not exist.
       10: A branch belonging to the specified point-to-multipoint
             connection is already established on the specified output
             port and the switch cannot support more than a single
             branch of any point-to-multipoint connection on the same
             output port.
       11: The limit on the maximum number of point-to-multipoint
             connections that the switch can support has been reached.
       12: The limit on the maximum number of branches that the
             specified point-to-multipoint connection can support has
             been reached.
       13: Unable to assign the requested VPI/VCI value to the requested
             branch on the specified point-to-multipoint connection.
       14: General problem related to the manner in which point-to-
             multipoint is supported by the switch.
       15: Out of resources (e.g. memory exhausted, etc.).
       16: Failure specific to the particular message type. (The meaning
             of this failure code depends upon the Message Type. It is



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             defined within the description of any message that uses
             it.)
       17: Cannot label each output branch of a point-to-multipoint tree
             with a different label.
       18: One or more of the specified input VPIs is invalid.
       19: One or more of the specified input VCIs is invalid.
       20: One or more of the specified output VPIs is invalid.
       21: One or more of the specified output VCIs is invalid.
       22: Invalid Class of Service field in a Connection Management
             message.
       23: Insufficient resources for QoS Profile.
       24: Virtual path switching is not supported on this input port.
       25: Point-to-multipoint virtual path connections are not
             supported on either the requested input port or the
             requested output port.
       26: Attempt to add a virtual path connection branch to an
             existing virtual channel connection.
       27: Attempt to add a virtual channel connection branch to an
             existing virtual path connection.
       28: Only point-to-point bidirectional connections may be
             established.
       29: Cannot support requested VPI range.
       30: Cannot support requested VCI range on all requested VPIs.
       31: The transmit cell rate of this output port cannot be changed.
       32: Requested transmit cell rate out of range for this output
             port.
      128: Weighted scheduling within this waiting room is unavailable.
      129: This waiting room is unable to offer weighted sharing for a
             QoS class.
      130: This waiting room is unable to offer weighted sharing for a
             connection.
      131: Scheduler Identifier still in use.
      132: QoS Class Identifier still in use.
      133: Invalid QoS parameter.
      134: Insufficient QoS resources.
      135: Any point-to-multipoint connection arriving on this input
             port must use the same QoS parameters for all output
             branches.


12. Summary of Message Set

   The following table gives a summary of the messages defined in this
   version of the specification. It also indicates which messages must
   be supported in a minimal implementation of the protocol. Those
   messages marked as "Required" must be supported by the switch for an
   implementation to be considered to conform to this specification.
   (While the controller should also implement those messages marked



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   "Required," conformance cannot be tested for the controller due to
   the Master-Slave nature of the protocol.)

       Message Name                Message Type    Status

   Connection Management Messages
       Add Branch VCC....................16        Required
                  VPC....................26
       Delete Tree.......................18
       Delete All........................20
       Delete Branches...................17        Required
       Move Branch VCC...................22
                   VPC...................27

   Port Management Messages
       Port Management...................32        Required
       Label Range.......................33

   State and Statistics Messages
       Connection Activity...............48
       Port Statistics...................49        Required
       Connection Statistics.............50
       QoS Class Statistics..............51
       Report Connection State...........52

   Configuration Messages
       Switch Configuration..............64        Required
       Port Configuration................65        Required
       All Ports Configuration...........66        Required

   Event Messages
       Port Up...........................80
       Port Down.........................81
       Invalid VPI/VCI...................82
       New Port..........................83
       Dead Port.........................84

   Quality of Service Messages
       QoS Configuration.................96
       Scheduler Establishment...........97
       QoS Class Establishment...........98
       QoS Release.......................99
       QoS Connection Management VCC....100
                                 VPC....101

   Adjacency Protocol....................10        Required





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REFERENCES

   [af-tm-0056] ATM Forum Traffic Management Specification 4.0, af-tm-
                0056.000, April 1996.

   [I.361]      "B-ISDN ATM Layer Specification," International
                Telecommunication Union, ITU-T Recommendation I.361,
                Mar. 1993.

   [I.363]      "B-ISDN ATM Adaptation Layer (AAL) Specification,"
                International Telecommunication Union, ITU-T
                Recommendation I.363, Mar. 1993.

   [IpsilonMIB] Ipsilon IP Switch MIB,
                http://www.ipsilon.com/products/ips.mib

   [Partridge]  C. Partridge, "Gigabit Networking," Addison-Wesley,
                1994.

   [RFC1700]    Reynolds, J., and J. Postel, "Assigned Numbers," STD 2,
                RFC 1700, October 1994.

   [RFC1987]    Newman, P, Edwards, W., hinden, R., Hoffman, E. Ching
                Liaw, F., Lyon, T. and G. Minshall, "Ipsilon's General
                Switch Management Protocol Specification," Version 1.1,
                RFC 1987, August 1996.


SECURITY CONSIDERATIONS

   Physical security on the control link connecting the controller to
   the switch is assumed. Security issues are not discussed in this
   document.


AUTHORS' ADDRESSES

   Peter Newman                        Phone: +1 (408) 990 2003
   Nokia                               EMail: pn@ipsilon.com

   W. L. Edwards, Chief Scientist      Phone: +1 (913) 534 5334
   Sprint                              EMail: texas@sprintcorp.com

   Robert M. Hinden                    Phone: +1 (408) 990 2004
   Nokia                               EMail: hinden@ipsilon.com

   Eric Hoffman                        Phone: +1 (408) 990 2010
   Nokia                               EMail: hoffman@ipsilon.com



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   Fong Ching Liaw                     Phone: +1 (408) 873 2688
   Coppercom                           EMail: fong@coppercom.com

   Tom Lyon                            Phone: +1 (408) 990 2001
   Nokia                               EMail: pugs@ipsilon.com

   Greg Minshall                       Phone: +1 (650) 237 3164
   Fiberlane Communications            EMail: minshall@fiberlane.com

Nokia (Sunnyvale) is located at:

   232 Java Drive
   Sunnyvale, CA 94089
   USA

Sprint is located at:

   Sprint
   Sprint Technology Services - Long Distance Division
   9300 Metcalf Avenue
   Mailstop KSOPKB0802
   Overland Park, KS 66212-6333
   USA

Fiberlane Communications is located at:

   1399 Charleston Road
   Mountain View, CA 94043
   USA






















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Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
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   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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