Wireshark-users: Re: [Wireshark-users] Question on Internet PerformanceTroubleshooting

From: Sake Blok <sake@xxxxxxxxxx>
Date: Fri, 2 Mar 2007 23:20:15 +0100

Hi Jim :)

On Fri, Mar 02, 2007 at 04:24:01PM -0500, Small, James wrote:
> 
> One more thing I didn't mention - the problems are mainly between 7-3
> when they have their peak load.  However, they are usually not getting
> to more then 70% of their theoretical bandwidth capacity so I'm not sure
> that it's necessarily a bandwidth problem.  When you look at an SNMP
> graph of their bandwidth usage, it doesn't seem like the are maxing out
> much and when they do it's very short lived.

You probably have checked this already, but I could not resist in 
mentioning it, did you check the duplex settings on the uplink-router,
the firewall and the switch-ports? If the packet-loss is higher when 
your (local) traffic increases, but your traffic is not maxing out
your links, it does sound like a local problem and duplex mismatches
are still source nr.1 in my experience.

If it is possible, set all speeds and duplex-modes fixed. Having one
side on fixed and the other side on auto is a sure cause for trouble.
Having both sides on auto usually works, but does indeed give you
duplex-mismatches sometimes. If you have a duplex mismatch, you will
see a lot of FCS/alignment errors on the interface in full-duplex
mode and a lot of collisions on the interface in half-duplex mode.

Cheers,


Sake