[c-nsp] 877 Throughput and others

[Mikael Abrahamsson]

On Fri, 25 Apr 2008, Skeeve Stevens wrote:

> I'm a little confused about the throughput of Cisco devices.
>
> The portable product sheet lists the 870 series as Fast/CEF switching as
> 12.80 Mbps maximum theoretical throughput.

No, that is not "maximum theoretical thruput". It means "with minimum 
packet size, this was the largest aggregate number of pps we managed to do 
with minimum features, without packetloss". So as packet size goes up, 
Mbps goes up, but the total attainable pps goes down.

> Does this mean an 877 with a ADSL2 service trained up at 20-24Mbps will
> never actually be able to attain those speeds?

No, because with larger packet sizes, you'll be able to do more Mbps than 
that.

> Does this mean 2 PC's on FE0 and FE1, the real layer 3 ports, can only talk
> at a maximum of 35Mbps?

See above.

> And take say a 7200G1 which says 521Mbps..  Does this mean between two of
> its 1GB interfaces, it can't get anywhere near 1GB?

See above.

> How much would NAT (if any) slow down the throughput?  What happens on a 
> 870 with 12, a 1811 with 35 and a 7200-G1 with 512Mbps?

You have to test it yourself. My guess would be that performance goes down 
with tens of percents.

> Is there a list perhaps of what is Process Switched, what is Fast/CEF
> switched and so on?

"show int switching" on the device. Usually there should be no traffic 
going thru the device that is process switched.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se