[Jeff Morriss <jeff.morriss@xxxxxxxxxxx>]

Keith French wrote:
> If you have a trunk between two switches spanned, is there any way you 
> can calculate the percentage utilisation of that trunk (e.g. 100M) from 
> an Ethereal trace?
>  
> I know that from the summary screen you can get average packets/s & 
> average packet size. So there must be some way of calculating the 
> utilisation as a percentage of the 100M port?
>  
> Any ideas?

Statistics->Summary shows you average Mbits/s (remember that this number 
is shows traffic going in both ways).  Divide that number by your 
network speed (100 Mbits/sec half duplex but more likely 200 Mbits/sec 
full duplex) and you'll see your utilization.  (Ethereal won't show this 
to you for the reason in my last email: Ethereal doesn't know the 
network speed.)

Of course this will only count the packets that Ethereal actually got. 
Also, if you're really into measuring network utilization, you might 
want to consider ntop: http://www.ntop.org instead.