The optional argument Length specifies the length, in octets,
    of the data field in each loop message.  The default is 40,
    and the value must be 0-65534.

    loop [node node-id] loopback application name full-name, -
         length integer [,optional arguments...]

    loop [node node-id] loopback application address tower-set, -
         length integer [,optional arguments...]

    Example:

    loop loopback application name DEC:.SCH.LAMCHP, length 80