o  client data size not supportable

    Client's buffer size is larger than the HDLC software can
    support.

 o  incompatible communications mode

    The value of the link type argument specified in the create
    command is incompatible with the actual type of link.

    Argument:

    reason   Feature of the line that is incompatible with the link
             type.

             CRC       The line does not support CRC selected
             mode not  by the preferred CRC type characteristic
             supported attribute.

             full-     The line is full-duplex and the link type is
             duplex    primary/secondary.
             mode

             half-     The line is half-duplex and the linktype is
             duplex    balanced.
             mode

             protocol  The line does not support HDLC framing.
             not
             supported

    Correct the value of the link type argument, or use a line
    that supports the appropriate protocol. Then reissue the enable
    command.

 o  open physical port failed

    Attempt to open a port to the Physical layer failed.

    Argument:

    reason  Specifies why the Physical layer rejected the open
            operation.

            invalid      The call to the Physical layer was
            argument     improperly formed.

            insufficient The Physical layer had insufficient system
            resources    resources to be able to open the port.

            line not     The line specified as the value to the
            available    physical line characteristic is already
                         allocated to another entity in the Data
                         link layer. Change the value of the physical
                         line characteristic to an unused line, and
                         reissue the enable command.

            no such      The entity specified in the physical line
            physical     characteristic does not exist. Check the
            line         value of the characteristic and if necessary
                         change it to the correct name, then reissue
                         the enable command. If the name is correct,
                         create the necessary Physical layer entity
                         and then reissue the enable command.