[ILUG] Network Analysis software for examining headers?

[P at draigBrady.com]

Chris Higgins wrote:
> On Tue, 15 Feb 2005 16:09:17 +0000
> P at draigBrady.com wrote:
> 
> 
> 
>>I suppose you could saturate the line with 1500 byte packets
>>and infer the preamble from the received packet rate.
> 
> 
> Only if you are sure about the bit encoding scheme used on the wire, and
> you'll also need to know what interframe gap[1] your generating machine is using... 
> but if you know that you surely can get the info on the size of the preamble ;-)

Wha?

I'm saying that if you make the assumption that the transmitter
can saturate the line with 1500 byte packets then one can
infer the inter packet gap like:

echo 'rate=8000; size=1500; ((100*10^6)/(8*rate))-size' | bc

I.E on 100Mb/s receiving only 8000 packets per second would
suggest a preamble of 62 bytes was being used.

As an aside, did you know that a preamble is only strictly
required on 10Mb/s LAN as 100 and 1000 used constant signalling.
The preamble is still used though, to avoid any changes in the
ethernet frame structure.

-- 
Pádraig Brady - http://www.pixelbeat.org
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