On Tue, 15 Feb 2005 15:50:10 -0000 (GMT)
"Conor Wynne" <weeboy at conorwynne.com> 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
Ahh... Ok .. That info is not likely to get past the network card itself.
Also - there is no guarantee that your network card will see all of the
preamble ( which is why it's there )... if your network card is otherwise
occupied then it may miss the first couple of bits of the preamble.. and it's
spending it's time using the preamble to synchronise on the incoming signal
rather than reading it as data.. so it's not really 'data' as such.
The preamble is just 1010101010101010 for 7 octets, followed by the start
of frame designator which is 10101011 as the 8th octet ( that final change
from (10)+ to 11 identifies the start of the frame ).
I don't know that anything passed up from the network driver will include
or even consider the preamble... so you may have to get down below the
network driver ( or look for hardware that will pull the electrical signal off
the wire itself )
Have you considered licking the end of the cable and counting the bits by hand ? :-)
>> I cannot tell this with ethereal.
>> > --
> > Chris Higgins
> > Darach Technology Ltd tel: +353-1-6204370
Darach Technology Ltd tel: +353-1-6204370
email: chris.higgins at darach.ie fax: +353-1-6204371
Maintained by the ILUG website team. The aim of Linux.ie is to
support and help commercial and private users of Linux in Ireland. You can
display ILUG news in your own webpages, read backend
information to find out how. Networking services kindly provided by HEAnet, server kindly donated by
Dell. Linux is a trademark of Linus Torvalds,
used with permission. No penguins were harmed in the production or maintenance
of this highly praised website. Looking for the
Indian Linux Users' Group? Try here. If you've read all this and aren't a lawyer: you should be!