The Session layer implements the user interface to the network.
    It is responsible for connection negotiation and establishment.
    The Session Control module performs the following functions:

    o  Manages transport connections on behalf of Session Control
       users.

    o  Enforces access control policies to restrict communication
       between users and between Session Control modules.

    o  Maps from a DNA Naming Service object name to protocols and
       addresses.

    o  Selects from the set of protocols supporting Session Control
       to attempt connection establishment.

    o  Maintains in the namespace the protocol and address
       information corresponding to objects that reside in the same
       node as the local Session Control module.

1  –  Subentities

    The entity hierarchy for the Session Control module is:

                              _Application
                             |_Backtranslation_Softlink
    Node___Session_Control___|_Port
                             |_Tower_Maintenance
                             |_Proxy (Tru64 UNIX)
                             |_Transport_Service

    The SESSION CONTROL entity is the top-level entity in the
    hierarchy of entities belonging to the Session Control module.

    A SESSION CONTROL APPLICATION entity stores information about an
    end user that is activated for receipt of an incoming connection
    request when the request contains that end user's name in its
    destination name field. The application-name refers to the
    application managed by this command.

    A SESSION CONTROL BACKTRANSLATION SOFTLINK entity stores
    information about entries in the backtranslation soft link
    database. The name is the unique name among the set of
    backtranslation soft-link subentities maintained by session
    control.

    A SESSION CONTROL PORT entity stores Session Control information
    about the transport connection. The port-name refers to the port
    managed by this command.

    A SESSION CONTROL PROXY entity stores the information that
    grants remote users proxy access to given application subentity
    instances.

    A SESSION CONTROL TOWER MAINTENANCE entity stores information
    about entries in the tower maintenance data base. A tower
    maintenance entity is automatically created when a client issues
    a dnaKeepMeHere call, using the programming interface. The name
    refers to the tower maintenance entity managed by this command.

    A SESSION CONTROL TRANSPORT SERVICE entity stores information
    about modules in the Transport layer that support Session
    Control. The transport-name refers to the transport service
    managed by this command.