Library /sys$common/syshlp/tcpip$ucp_help.hlb LOOP, Qualifiers, /PATTERN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /PATTERN=hexadecimal-string

    Optional.

    Fills out the packet you send with up to 16 bytes, which is
    useful for diagnosing data-dependent problems. The hexadecimal-
    string is a string of hexadecimal digits of up to 32 characters
    (16 bytes).

    For example, /PATTERN="ff" causes the sent packet to be filled
    with ones (1).