header field to use to establish the covert channel. Currently the following fields are available:
<P>

ip-tos
<DL COMPACT><DT><DD>
IPv4 Type of Service. (8 bits).
</DL>

<P>

ip-id
<DL COMPACT><DT><DD>
IPv4 Identification. (16 bits).
</DL>

<P>

tcp-ack
<DL COMPACT><DT><DD>
TCP Acknowledgement Number (32 bits)
</DL>

<P>

tcp-seq (Default)
<DL COMPACT><DT><DD>
TCP Sequence Number (32 bits)
</DL>

<P>

tcp-sport
<DL COMPACT><DT><DD>
TCP Source Port (16 bits)
</DL>

<P>

tcp-win
<DL COMPACT><DT><DD>
TCP Wind