[ILUG] Network Analysis software for examining headers?

[P at draigBrady.com]

Conor Wynne wrote:
>>On Tue, 15 Feb 2005 15:26:07 -0000 (GMT)
>>"Conor Wynne" <weeboy at conorwynne.com> wrote:
>>
>>
>>>Hi all,
>>>
>>>I'm in search of a network analysis tool to look at the headers of
>>>network packets.
>>>
>>>I checked out ethereal, and sadly it falls short of the job.
>>
>>Huh ? What packet types are you trying to look at if ethereal
>>isn't doing it for you ?
> 
> 
> I need to know what the "real" length of the preamble. It should be
> 64bits, but some vendors do not follow the specifications (apparently).

well its 64 bits preamble and 160 bits postamble,
so 20 bytes in total. Where and how are you
seeing a discrepency? see the gnuplot e.g. here:
http://www.pixelbeat.org/cmdline.html

> I cannot tell this with ethereal.

Only the nic will no about layer 1 stuff like that,
and that info is not passed up.
You will need to get some specialised equipment for L1.

I suppose you could saturate the line with 1500 byte packets
and infer the preamble from the received packet rate.

-- 
Pádraig Brady - http://www.pixelbeat.org
--- Following generated by rotagator ---

Shell loops

for item in 1 2 3 4; do          while read line; do
     echo "item=$item"                echo "line=$line"
done                             done

Note you can pipe into and out of loops also
but be wary as they're run in a subshell so
any change in environment variables are local
to the loop.
--