Take a look at a smokeping. Cable tends to be +/- 10 ms from what I can tell. Comcast here in CO seems a little more reliable than TWC/RR in Fredericksburg TX as far as I can see.
But the variance on Embarq, usually less than 1ms...rock solid. Not that it impacts connection quality a ton, but it's funny that the phone company's internet service is the best one for VoIP.
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