You'll recall that after Comcast had their wrist slapped by the FCC, they wound up shifting to a protocol agnostic network management platform in late 2008. Instead of using a blunt hammer to throttle all users 24/7, the system targets only heavy users on the heaviest nodes, and temporarily flips the user to a lower quality of service (QoS) until they ease off consumption. This platform is supplied in large part by Sandvine, who calls it "Fairshare," and says they're now testing the system on DOCSIS 3.0 CMTS' with four tier 1 providers in North America and Europe (you can probably safely assume Comcast is one of them).