o  physical port

    Name of the port entity in the Physical layer returned when the
    port is opened. If this is null, the port is not open.

 o  state

    State of the DDCMP link. The value of this attribute is
    determined by the enable and disable commands.

    off      The entity is disabled.

    on       The entity is enabled.

    In addition the link is disabled and its state set to off if the
    Physical layer port that the link uses is deleted.

 o  uid

    Entity's unique identifier, which is generated when the entity is
    created.