full-disclosure - Sniffing on 1GBps

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Message-ID: <4496A1D0.20904@csuohio.edu>
Date: Mon Jun 19 14:07:55 2006
From: michael.holstein at csuohio.edu (Michael Holstein)
Subject: Sniffing on 1GBps

Sure, it's possible .. but (possible != cheap).

A cheap way to go is to use a Intel card, and enable device polling for 
it in the kernel (*bsd), or use PF_RING (linux). A lot of other factors 
will come into play, depending on the link utilization (sustained 
line-rate capture at 1gbps is much harder than 1gpbs bursts).

While 33mhz 32bit PCI will get you close, you should get something 
that's 66mhz or PCI-X, etc. You should also try to get the ethernet card 
on it's own PCI bus if possible (eg: don't put it next to the RAID 
card). You will also need a fairly fast disk array to offload the 
capture at line rate, and you should have lots of physical memory.

If you've got deep pockets, get a dedicated capture card like the DAG 
units from Endace (there are a half-dozen folks that make similar 
models) .. these let you put BPF expressions on the card itself, and 
offload a lot of the capture CPU overhead onto dedicated processors.

Also .. if you've got fiber as your PHY and you're using passive taps, 
you'll actually need 2 cards (using receive on each card for one half 
the link), and combine the two in the kernel using something like 
netgraph (again, *bsd).

When doing gigabit (or faster) capture at wire-speed, a lot of other 
factors like PCI bandwidth, disk bandwidth, interrupts, etc. come into play.

Good luck.

Michael Holstein CISSP GCIA
Cleveland State University

crazy frog crazy frog wrote:
> Hi List,
> I m just wondering if it is possible to capture the data from a
> highspeed NIC card?if it is possible then wht kind of precaution we
> have to take so that we does not miss the data?
> thanks for any help.
> -------
> CF
> 
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