switch forwarding rates

carl_townshend · ‎12-16-2008

Hi all

when we look at the pps forwarding rates of switches, is this the backplane speed?

and being a switch would it be expressed in frames per second?

Giuseppe Larosa · ‎12-16-2008

Hello Carl,

yes they are frame per seconds at the backplane level.

Be aware that all numbers in data sheet don't make distinction between received and transmitted

So 2Mpps should be seen as able to tx and rx 1Mpps

Hope to help

Giuseppe

Joseph W. Doherty · ‎12-16-2008

PPS (packets per second) is how fast the hardware can forward packets and should be noted for a certain packet size. Backplane speed, bps, is the bandwidth supported within the device. The two are interrelated, but can be different. There is an optimal value for both, for instance:

100 Mbps Ethernet's bandwidth is 100 Mbps, but to fully drive that, in one direction, requires 148,809 pps if packets are 64 bytes or 8,100 pps if packets are 1518 bytes.

On many non-wirespeed switches, either pps and/or backplane might be insufficent to drive all ports at full bandwidth with minimum sized packets.