Is that the internal Network or to the Internet?
If it is for the Internal Network have you checked for any type of Infections that may be chewing up your Internal Bandwidth? The more traffic that is on the Internal Network the slower the response times will appear to be.
For an External Connection what is the Speed of your Internet Connection? Splitting one Internet Connection over several users slows down response times considerably and if it was a slow ADSL Connection to begin with it will be too slow for any heavy Duty Web Browsing.
Remember that having things like Torrents Installed also qualifies as Infecting the units as they chew up Bandwidth like there is no tomorrow.
As for a Network Testing utility how about a Free one Wireshark?
http://www.wireshark.org/download.html
Just remember to look at the Get Help pages here
http://www.wireshark.org/docs/
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