[Jack Jackson <jack@xxxxxxxxxxxxxxx>]

At 09:35 PM 4/20/2005, bunty wrote:

>   hello,
>               I use ethereal and transfer data from linux machine to 
> windows and capture analysis says that it captured FTP-DATA packet of 
> 1460 bytes. Now i try to use FTP between 2 redhat linux machines and 
> capture results shows that FTP-DATA is of 1448 bytes. Then i found that 
> Linux uses some 12 bytes header at TCP. Anybody knows for what purpose 
> linux uses these 12 bytes?
> regards,
> bunty.

If I understand you correctly, the TCP header is 12 bytes longer for some 
of the messages.  If so, then those headers probably have TCP options in 
them.  Look at the headers and see what is different.