Abstract: In this paper we examine the impact of router based congestion control mechanisms in the presence of uncooperative traffic. We consider two classes of control mechanisms: (1) fair queuing mechanisms (FRED, DRR, CSFQ) and (2) feedback based mechanisms (ERAF, NBP). Within the subclass of feedback based mechanisms we distinguish between binary feedback mechanisms (ERAF) and rate feedback mechanisms (NBP). The criteria we use for our comparison are: efficiency, fairness, convergence and scalability. Our results indicate that the feedback based mechanisms are able to shield responsive traffic competing with uncooperative traffic on a single link with the same efficiency as the fair queuing mechanisms. For more complex topologies, the feedback based mechanisms offer better bandwidth allocations than the fair queuing mechanisms alone.