The stability of the current Internet depends on the end-to-endcongestion control mechanism provided by TCP. Recently, popularmultimedia applications (RealAudio, RLM) started using moreaggressive forms of congestion control. It is not clear yet how wideuncooperation will become in Internet, but it seems dangerous tobase the Internet congestion control solely on the assumption ofend-host cooperation. In this paper we examine the impact ofrouter based congestion control mechanisms in the presence ofuncooperative traffic. We consider two classes of congestioncontrol mechanisms (1) fair queuing mechanisms (FRED, DRR, CSFQ) and(2) feedback based mechanisms (ERAF, NBP). Within the subclassof feedback based mechanisms we distinguish between binary feedbackmechanisms (ERAF) and rate feedback mechanisms (NBP). The criteriawe use for our comparison are: efficiency, fairness, convergence andscalability. Our results indicate that the feedback based mechanismsare able to shield responsive traffic competing with uncooperativetraffic on a single link with the same efficiency as the fair queuingmechanisms. For more complex topologies, the feedback based mechanismsoffer better bandwidth allocations than the fair queuing mechanisms alone.In particular, the binary feedback mechanism we examine is able toprovide allocations close to proportional fairness.