The congestion control algorithm(s) of TCP seem to distribute the available bandwidth fairly between individual TCP flows.

Is there some way to enable (or more precisely, enforce) fair bandwidth sharing on a per-host instead of a per-flow basis on a router? There should not be an (easy) way for a user to gain a disproportional bandwidth share by using multiple concurrent TCP flows (the way some download managers and most P2P clients do).

I'm currently running a DD-WRT router to share a residential DSL line, and currently it's possible to (inadvertently or maliciously) hog most of the bandwidth by using multiple concurrent connections, which affecty VoIP conversations badly. I've played with the QoS settings a bit, but I'm not sure how to enable fair bandwidth sharing on a per-IP basis (per-service is not an option, as most of the flows are HTTP).