rfc2126.txt

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   Actions

      N-CONNECT.REQUEST
         - a NS-user indicates that it wants to establish a network
           connection

      N-CONNECT.RESPONSE
         - a NS-user indicates that it will honour the request

      N-DISCONNECT.REQUEST
         - a NS-user indicates that the network connection is to be
           closed

      N-DATA.REQUEST
         - a NS-user sends data

      N-EXPEDITED_DATA.REQUEST
         - a NS-user sends "expedited" data

   Events

      N-CONNECT.INDICATION
         - a NS-user is notified that a network connection establishment
           is in progress

      N-CONNECT.CONFIRMATION
         - a NS-user is notified that the network connection has been
           established

      N-DISCONNECT.INDICATION
         - a NS-user is notified that the network connection is closed

      N-DATA.INDICATION
         - a NS-user is notified that data can be read from the network
           connection

      N-EXPEDITED_DATA.INDICATION
         - a NS-user is notified that expedited data can be read from
           the connection



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3.2.2 TCP Service primitives

   The mapping between, ISO 8348 CONS primitives and TCP Service
   primitives, defined in this document assumes that the TCP offers the
   following service primitives:

   Actions

      TCP-LISTEN_PORT
         - PASSIVE open on given port

      TCP-OPEN_PORT
         - ACTIVE open to the given port

      TCP-READ_DATA
        - data is read from the connection

      TCP-SEND_DATA
        - data is sent on the connection

      TCP-CLOSE
        - the connection is closed (pending data is sent)

   Events

      TCP-CONNECTED
        - open succeeded (either ACTIVE or PASSIVE)

      TCP-CONNECT_FAIL
        - ACTIVE open failed

      TCP-DATA_READY
        - Data can be read from the connection

      TCP-ERRORED
        - the connection has errored and is now closed

      TCP-CLOSED
        - an orderly disconnection has started

3.2.3 Mapping TCP as a Network Service Provider

3.2.3.1 Network Connection Establishment

   In order to perform a N-CONNECT.REQUEST action, the TS-Provider
   performs a TCP-OPEN_PORT to the desired IPv4 or IPv6 address using
   the selected TCP port. When the TCP signals either success or
   failure, this results in an N-CONNECT.INDICATION action.



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   In order to await a N-CONNECT.INDICATION event, a server performs a
   TCP-LISTEN_PORT to the selected TCP port.  When a client successfully
   connects to this port, the TCP-CONNECTED event occurs and an implicit
   N-CONNECT.RESPONSE action is performed.

   Mapping parameters between the TCP service and the ISO 8348 CONS
   service is done as follow:

   Network Service                 TCP
   ---------------                 ---
   CONNECTION ESTABLISHMENT

           Called address          server's IPv4 or IPv6 address
                                   and TCP port number.

           Calling address         client's IPv4 or IPv6 address

           all others parameters   ignored

   Please also refer to 'Notes to Implementors' section 6.1.

   TCP port 102 is reserved for implementations conforming to this
   specification.  Use of any TCP port is conformant to this
   specification.

3.2.3.2 Network Data Transfer

   In order perform a N-DATA.REQUEST action, the TS-provider constructs
   the desired transport protocol data unit (TPDU), encapsulates the
   TPDU in a discrete unit called TPKT and uses the TCP-SEND_DATA
   primitive.  Please also refer to 'Notes to Implementors' section 6.2.

   In order to trigger a N-DATA.INDICATION action, the TCP indicates
   that data is ready through TCP-DATA_READY event and a TPKT is read
   using the TCP-READ_DATA primitive.

   Mapping parameters between the TCP service and the ISO 8348 CONS
   service is done as follow:

   Network Service                 TCP
   ---------------                 ---
   DATA TRANSFER

           NS User Data (NSDU)     DATA







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3.2.3.3 Network Connection Release

   In order to perform an N-DISCONNECT.REQUEST action, the TS-provider
   simply closes the TCP connection through TCP-CLOSE primitive.

   In order to trigger a N-DISCONNECT.INDICATION, the TCP indicates that
   the connection has been closed through TCP-CLOSE event.  If the TCP
   connection has failed the TCP indicates that the connection has been
   closed through TCP-ERRORED event, this trigger a N-
   DISCONNECT.INDICATION.

   Mapping parameters between the TCP service and the ISO 8348 CONS
   service is done as follow:

   Network Service                 TCP
   ---------------                 ---
   CONNECTION RELEASE

           all parameters          ignored

4. Transport Protocol Specification

   ISO 8073 Transport Protocol Classes 0 and 2 are supported with
   extensions as defined in each subsections below.

   A Transport Protocol class is selected for a particular transport
   connection based on the requirements of the TS-User.

   ISO 8073 Transport Protocol exchanges information between peers in
   discrete units of information called transport protocol data units
   (TPDU). The protocol defined in this document encapsulates these
   TPDUs in discrete units termed Packets (TPKT).

   This document mandates the implementation of ISO 8073 Transport
   Protocol options negotiation (which includes class negotiation).

   Please refer to 'Notes to Implementors' section 6.3 with respect to
   Class negotiation and to the 'Rationale' section 7. with respect to
   Interoperability with RFC1006.

4.1 Class 0 over TCP

   Class 0 provides the functions needed for connection establishment
   with negotiation, data transfer with segmentation, and protocol error
   reporting.  It provides Transport Connection with flow control based
   on that of the NS-provider (TCP).  It provides Transport
   Disconnection based on the NS-provider Disconnection.




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   Class 0 is suitable for data transfer with no Explicit Transport
   Disconnection.

4.1.1 Connection Establishment

   The principles used in connection establishment are based upon those
   described in ISO 8073, with the following extensions:

   - Connect Data may be exchanged using the user data fields
     of Connect Request (CR) and Connect Confirm (CC) TPDUs

   - Use of "Expedited Data Transfer Service" may be negotiated
     using the negotiation mechanism specified in ISO 8073. The
     default is to not use "Expedited Data Transfer Service".

   - Non-standard TPDU size may be negotiated using the negotiation
     mechanism specified in ISO 8073. The maximum TPDU size is 65531
     octets. The Default maximum TPDU size is 65531 octets.
     Please refer to 'Notes to Implementors' section 6.4.

4.1.2 Data Transfer

   The elements of procedure used during transfer are based upon those
   presented in ISO 8073, with the following extension:

      - Expedited Data may be supported (if negotiated during connection
        establishment) by sending the defined Expedited Data (ED) TPDU.

   The ED TPDU is sent inband on the same TCP connection as all of the
   other TPDUs.

   To support Expedited Data a non-standard TPDU is defined. The format
   used for the ED TPDU is nearly identical to the format for the Normal
   Data (DT) TPDU. The only difference between ED TPDU and DT TPDU is
   that the value used for the TPDU code is ED and not DT. The size of a
   Expedited Data user data field is 1 to 16 octets.

   For TPDU bit encoding please refer to 'Notes to Implementors' section
   6.5.

4.1.3 Connection Release

   The elements of procedure used during a connection release are
   identical to those presented in ISO 8073.

   Transport Disconnection is based on the NS-provider (TCP)
   Disconnection and is therefore disruptive.




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4.2 Class 2 over TCP

   Class 2 provides the functions needed for connection establishment
   with negotiation, data transfer with segmentation, and protocol error
   reporting.  It provides Transport Connection with flow control based
   on that of the NS-provider (TCP). It provides Explicit Transport
   Disconnection.

   Class 2 is suitable when independence of Normal and Expedited Data
   channels are required or when Explicit Transport Disconnection is
   needed.

4.2.1 Connection Establishment

   The principles used in connection establishment are based upon those
   described in ISO 8073, with the following extensions:

   - Connection Request and Connection Confirmation TPDUs may
     negotiate use of "Transport Expedited Data Transfer" service.
     "Transport Expedited Data Transfer" service is selected
     by setting bit 1 of the "Additional Option" parameter,
     and is negotiated using the mechanism specified in ISO 8073.

     The default is to not use "Transport Expedited Data Transfer
     Service".

   - Connection Request and Connection Confirmation TPDUs may
     negotiate use of "Expedited Data Acknowledgement".
     "Expedited Data Acknowledgement" is selected by setting
     bit 6 of the "Additional Option" parameter, and is
     negotiated using the mechanism specified in ISO 8073.

     The default is to not use "Expedited Data Acknowledgement"
     for Expedited Data transfer.

   - Connection Request and Connection Confirmation TPDUs may
     negotiate use of the "Non-blocking Expedited Data" service.
     "Non-blocking Expedited Data" is selected by setting
     bit 7 of the "Additional Option" parameter, and is
     negotiated using the mechanism specified in ISO 8073.

     The default is to not use the "Non-blocking Expedited
     Data" service.

   - Connection Request and Connection Confirmation TPDUs may
     negotiate use of either "Forward Connection (Splitting
     and Recombining)" or "Reverse Connection" procedure for
     Expedited Data transfer.



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     Use of "Forward Connection" or use of "Reverse Connection"
     procedure is selected by setting bit 4 of the "Additional
     Option" parameter, and is negotiated using the mechanism
     specified in ISO 8073.

     The default is to use "Forward Connection" procedure for
     Expedited Data transfer.

   - Connection Request and Connection Confirmation TPDUs must not
     negotiate the use of "Explicit Flow Control".

   - Non-standard TPDU size may be negotiated using the negotiation
     mechanism specified in ISO 8073. The maximum TPDU size is 65531
     octets. The default maximum TPDU size is 65531 octets.
     Please refer to 'Notes to Implementors' section 6.4.

   In the absence of a Flow Control policy, the use of ISO 8073
   Multiplexing procedure lead to degradation of the quality of service.
   The Protocol defined in this document does not supported
   Multiplexing.

   For the values of the "Additional Option" parameter please refer to
   'Notes to Implementors' section 6.6.