Performs a loop operation with another system.  If you optionally
    chose to enter a Client Name in the previous menu, the default loop
    parameters for this operation were obtained by looking up the
    information for that MOP Client, and those parameters are present in
    the current display.

    The required arguments for this loop operation are:

     o  Address

        The LAN address of the target node on the circuit named in the
        circuit argument.

     o  Circuit

        The MOP circuit you have currently selected for the loop operation.

     The optional arguments for this loop operation are:

     o  Client

        A client entity to be used for this operation, if you provided one
        in the previous display.

     o  Count

        An integer representing the number of messages to be looped.
        On failure of the loop test, a the count of messages
        successfully looped will be displayed.

     o  Format

        Value of each byte in the test data part of each loop message.
        The default results in alternating 0 and 1 bits.

     o  Length

        Integer representing length of the test data part of each loop
        message. The maximum and minimum permitted values depend on the
        particular data link in use.

     o  Assistance Type

        Degree of loopback assistance required, for LAN circuits only.
        Valid values are none, transmit, receive, and full.

     o  Assistant Address

        LAN address to be used as a loopback assistant. The involvement
        of the assistant depends on the assistance type parameter. For
        assistance of type none, no assistant is needed, and is ignored
        if specified. For other values, an assistant is required. If not
        specified, an assistant is located by first sending a request to
        the loopback assistant multicast address.

     o  Assistant System

        A MOP Client entity, from which an assistant address is obtained.
        Meaningful for LAN circuits only, see assistant address.

    Pressing the OK button will cause the loop command to be executed and
    will return control back to the main window.

    Pressing the RESET button will cause all the arguments to be reset back
    to the state they were in when you first entered this display.

    Pressing the CANCEL button will return you to the main window.  No loop
    command will be issued.