Comcast made good on its pledge to migrate its entire network management system to a new protocol agnostic platform by the end of 2008, according to reports, and the new rules are now fully operational in all markets. Broadband Reports has a fairly detailed summary of how the new Comcast policy works so as to slow traffic to high-bandwidth users during time of peak network congestion.
Basically the plan checks for two conditions to engage throttling: sustained usage of 70 percent or more of your allotted up or downstream throughput or if you are somehow identified as clogging things up for up to 15,000 subscribers attached to a given Cable Modem Termination System. Given any of these two conditions a users internet connection will be throttled for at least 15 minutes, or until his average bandwidth utilization rate drops below 50 percent for 15 minutes.
The new technique will not manage congestion based on what applications high-bandwidth subscribers are using. While this is certainly a more transparent approach it remains to be seen how effective it will be. In addition to the new throttling system, Comcast has also a 250GB monthly usage cap for all users.