Creates an instance of a frame link entity, which is associated with
    a physical line and controls the framing protocol used on that line.
    There is one frame link entity for each physical line.  The link-id
    is a simplename that identifies this frame link instance.

    create  [node node-id] frame link link-id -
          protocol protocol-type [,control mode mode]

    The Protocol argument is required.  It determines the framing
    protocol used over the link.  Possible protocol-type values are:
    bisync, hdlc, chips, sdlc, ddcmp, swift, and genbyte.

    The Control Mode argument is optional.