How to measure Router/Switch performance

[danigoulart]

I need to measure router/switch performance for capacity planning purposes.

So I've been using the Router/Switch Switching Performance in Packets Per Second (PPS) getting the CISCO maximum values versus the data transferred on the device itself, but most of the time the devices has transferred more than the maximum CISCO PPS values.

So I'm looking for the correct way of collecting the Router/Switch Switching Performance in Packets Per Second (PPS) - nowadays I've been gathering the transmited/received data in Bps - from the device itself and a proper procedure to predict the required capacity on the devices where the maximum CISCO PPS is achieved.

[Joseph W. Doherty]

If you need to measure device performance capacity, and devices are carrying production traffic, you might capture the device's CPU load relative to traffic transiting the box and scale. (This might best reflect capacity against your specific traffic.)

When using PPS, you realize it varies per packet size? You often need to read the "fine print" on performance sheets with regard to the traffic packet sizes and PPS rates. If PPS is provided for minimum size packets, device is often able to forward increased bandwidth if average packet size larger.

[danigoulart]

The reason I've been considering the PPS is because I was told this is the only effective way to measure a device capacity, using the CISCO indicated Fast/CEF Switching for routers and Switching Performance for switches in PPS.

So I've been dathering the average number of data transferred on all interfaces on the device in question in Bps and then calculating it to define the device capacity rather than using the CPU and memory values.

Is this a valid way to measure the device capacity?