/sys$common/syshlp/helplib.hlb TCPTRACE, Qualifiers, /PROTOCOL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /PROTOCOL = {ARP | ICMP | IP | TCP | UDP}

    Optional. Default: IP

    Specifies the protocol to trace. Use in conjunction with the
    /PORT qualifier to filter tracing to an exact port and protocol.