Re: Linux based router for Gigabit traffic

[Stephen Samuel <samuel@bcgreen.com>]

An HTTP load is pretty much unidirectional (outbound), so that
700megabits is the total system load.

Anantha wants to  ROUTE 1gigabit of traffic -- That's
1gig in + 1gig out =2gig total.

if you divide your 700Megabit HTTP traffic by two, you'll
get a bit less than the 400Mb that he's claiming to have
gotten so far.

A quick overview:

Matti's bus bandwith calcs indicate that standard PCI won't
do the job in terms of theoretical bandwidth capability.
Once you switch up to PCI-Express, you'll have the
bus bandwith, but you may end up with A CPU limit
(the soft INT's).
   At that point, you might have to go to Real-Time Linux
   and, possibly, custom drivers.  If you can get away from
   the the kernel Task Switching overhead for each packet,
   you should be OK in terms of CPU capability.




Stephen J. Smoogen wrote:
 > On Sun, 22 Aug 2004 23:55:29 +0530, Anantha Kiran
 > <ananth.kandukuri@gmail.com> wrote:
 >
 >>No, we are not using NAPI for this. But we wrote a net_hook module
 >>which catches the pkts before allowing it to go upper layers.
 >>
 >>CPU utilization is 70+ while dropping.
 >>
 >>Can u tell me the configuration of your low-end machine.Like PCI-bus,
 >>and others.
 >>
 >
 >
 > Ours are Intel(R) Xeon(TM) CPU 2.40GHz and the motherboard has a PCI-X
 > chipset on it. We have one Intel fibre optic Gig-E on the 02:01 PCI-X
 > Bus, and the other on the 03:01 PCI-X bus. I see a limit of about 750
 > mbits/sec on a fixed load (HTTP accesses for specific boxes), and 400
 > mbits/sec on a mixed load (ICMP/UDP/TCP). In each case, the maximum
 > looks to not be the bus speed as much as the soft-irq limit (which is
 > what mpstat says is using all the resources). The number of packets
 > per second that ifconfig and other tools gives me looks about the
 > same. so I am thinking it isnt bus width at the moment as much as
 > IRQ/packets per second.
 >
 > The kernels are NAPI compiled.. but I really havent figure out if
 > using netfilters on these mixed loads 'disables' it.
 >


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Stephen Samuel +1(604)876-0426                samuel@bcgreen.com
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