I missed the original request but I saw the response about using ping and comparing 
results over time. I wanted to interject some points.

Network overload needs a definition before you go too far. If you have batch type 
traffic and response time is not an issue, then overload is different than say SSH 
based user sessions. If you are transfering files and it gets done in time, then your 
fine.

If your interactive sessions are the concern, then using a response measurement tool 
such as ping may be appropriate. However, ping tests tend to use the same size packet 
for each test. Networks may or may not function this way. Say for example a web site. 
Small packets in, large packets out is a common generalization. Therefore it is best 
to use something that emulates the typical traffic. A web response measurement tool is 
one way of doing it for web sites.

All of the above also have the added feature of adding load while measuring it. That 
means you may be creating the very problem you want to avoid yet measure. This leads 
to methods that look at traffic measured at the server such as monitoring the TCP 
round trip timers (difficult to do and difficult to interpret) or looking at network 
devices and server statistics to check their load handling statistics.

Sorry to be so verbose. The underlying point is that you need to be specific in 
defining what you want to measure and how you want to do it. Then look for proven 
tools. I have used Solarwinds and the stuff at the National Labs for Applied Network 
Research (dast.nlanr.net) also looks good. I'd also speak with your network equipment 
provider as sometimes they have tools for this as well (Cisco does).

Good luck,

Mark


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Mark Reardon
Reardon Information Security Corporation
156 Blue Sky Drive
Marietta, GA 30068
(770) 565-0544
(404) 444-0041 cell

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