Need to test an internet connection for reliability?

I need to run some tests on my parents DSL connection. From what I can tell, devices connecting to the Internet through their router lose their connection approximately every 10 minutes. The connection stays down for 30 seconds or so, then it's back to normal as if nothing had happened.

I'm going to call their ISP and talk to tech support, but before I do that I'd like to have a little more data about what exactly is going on. Ideally I'd like a program or something that I can run overnight, which will monitor their connection and record when it goes out and for how long. I did some checking with Google, but all of the internet testers I was able to find were simple speed tests, rather then the long-term reliability test I need. Any suggestions about where to look or other ideas I might try would be most appreciated.