Ask HN: Best way to know your ISP is throttling you?

I am a (unhappy) Comcast customer and there is no other service that I can get in my area. I have to teleword and do required high-speed connection. Problem is that I feel many times I am being throttled for even stuff like Youtube videos, remote login etc.

So, anyone here knows tools etc. to see whether my ISP is throttling me? I pay for 30mbps down. Is there a tool to sample that at given intervals to see if I do get what I pay for?

Any other thoughts on this subject are also appreciated.