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Re: system requirements


On Mon, 18 Aug 2003 09:26:23 +0200 Martin Burman <martin@default.nu>

> Mathias Kölsch wrote:
> >What are the system requirements for a debian-based router/firewall
> >for gigabit ethernet adapters?
> The PCI-bus got some limitations, i think it was about 433 mbit/s IRL.
> I recommend you to investigate PCI-X (or newer if it exists, I didn't 
> find the article so I don't now how outdated this information is).

PCI busses are theoretically maxed out at
	1 Gbit/s	standard:  32bit @ 33MHz (usually 5V)
	2 Gbit/s	wide:	   64bit @ 33MHz
	2 Gbit/s	fast:	   32bit @ 66MHz
	4 Gbit/s	wide+fast: 64bit @ 66MHz (usually 3.3V only)

So the PCI bus limits to one halfduplex (std) or two duplex (fast+wide)
Gig-eth cards. Plus there is the limiting CPU. As filtering usually is
done in kernel space, multiple CPUs don't help overly much.

If you have multiple CPU busses (busses != slots), you can distribute
the fast eth cards among them to max out system performance. But make
sure the backplane is fast enough to cope with them. I've seen backplane
designs where multiple PCI bus controllers only shared a common 1Gbit/s
interconnect bus.  *sigh*  


Volker Tanger


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