VMS Help TCPIP Services, Programming Interfaces, RPC XDR Routines, xdr_authunix_parms, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Used for externally describing standard UNIX credentials. On a
    TCP/IP Services host, this routine encodes the host name, the
    user ID, and the group ID. It sets the group ID list to NULL.
    This routine is useful for users who want to generate these
    credentials without using the ONC RPC authentication package.