I would first connect a wired pc to the modem directly then test the connect from PC to modem. You would be pinging the modems IP address, 192.168.100.1.
Then connect up your router and test the routers IP then test the modem thru the router. Then test pingplotter.com site. You need to let the test run for a few minutes to see results. Right click on the title row for each column name and select them ALL. Err, PL% and latency is most important to look at.
Review pingplotters site info on how to run it as well or
http://www.badmodems.com/Issue3.htm
