Software router state of the art

William Herrin herrin-nanog at
Wed Jul 23 18:17:53 UTC 2008

On Wed, Jul 23, 2008 at 2:03 PM, Naveen Nathan <naveen at> wrote:
>> The Endace DAG cards claim they can move 7 gbps over a PCI-X bus from
>> the NIC to main DRAM. They claim a full 10gbps on a PCIE bus.
> I wonder, has anyone heard of this used for IDS? I've been looking at
> building a commodity SNORT solution, and wondering if a powerful network
> card will help, or would the bottleneck be in processing the packets and
> overhead from the OS?

The first bottleneck is the interrupts from the NIC. With a generic
Intel NIC under Linux, you start to lose a non-trivial number of
packets around 700mbps of "normal" traffic because it can't service
the interrupts quickly enough.

The DAG card can be dropped in to replace the interface used for a
libpcap-based application. When I tested the 1gbps PCIE version, I
lost no packets to 1gbps and my capture application's CPU usage
dropped to about 1/5th of what it was with the generic NIC. YMMV.

Bill Herrin

William D. Herrin ................ herrin at bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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