Network Performance.

Currently we are having some problems with a couple of our remote computers,
at specific times in the day they seem to be slowing down for no reason. No
auto updates/scheduled tasks running etc.

It seems to be network related, but as of yet I'm unable to find a cause.
Does anyone have any software that they can recommend to monitor network
performance. i.e. Bandwidth, Packet Lose, Collision's etc.

It would also be useful to monitor our VPN, even if this means separate
software. We have tried to get something done through BT, but the result's
are rather disappointing as it gives nothing more than peek and average
usage, which tells me nothing.

Thanks in advance, Andrew.