Arunkumar wrote:
> Dear all
> I have modelled Cisco catalyst 2948G.It has 48+2 ports which were
> assumed as interfaces.Since it supports RFC1213,Interface Utilisation
> of each port is calculated based on
> 800 * max( $ifInOctets,$ifOutOctets ) / $ifSpeed*timeInterval
>
> Now i need to find "Bandwidth Utilisation" of Switch.In CISCO-STACK
> MIB,node "sysTraffic" with oid ..1.3.6.1.4.1.9.5.1.1.8 states:
> "Traffic meter value, i.e. the percentage of bandwidth utilization for
> the
> previous polling interval".
>
> But i read somewhere it gives the value of the "Backplane Utilisation"
> of switch and not "Bandwidth Utilisation".my question is
> 1.)What is the difference between two?
> 2.)If "sysTraffic" points to BackplaneUtilisation,how is Bandwidth
> Utilisation of a switch
>
> Thanks in advance
> E.L.R.Arunkumar
> www.adventnet.com

I think you need to be a bit clearer about exactly what the "bandwidth
utilisation" of a switch means.

Imagine a switch in whch two ports are active, both 10M, and traffic is
streaming at 10M from port 1 to port 2, with nothing in the other
direction. What is the bandwith utilisation? 100% or 50%?

Now plug in a third 10M port which carries no traffic. Is the
utilisation now 66% or 33%?

Now change that silent third port from 10M to 100M. What's the
utilisation now?

It seems reasonable to me to give the utilisation of the backplane,
which is a known fixed capability.

Steve