Beyond TCP-Friendliness: A New Paradigm for End-to-End Congestion Control

The dominant paradigm for congestion control in the Internet today is based on the notion of TCP-friendliness. To be TCP-friendly, a source must behave in such a way to achieve a bandwidth that is similar to the bandwidth obtained by a TCP flow that would observe the same Round Trip Time (RTT) and the same loss rate. However, with the success of the Internet comes the deployment of an increasing number of applications that do not use TCP as a transport protocol. These applications can often improve their own performance by not being “TCP-friendly” which severely penalize TCP flows. Also, designing these new applications to be “TCP-friendly” is often a difficult task. For these reasons, we propose a new paradigm for end-to-end congestion control (the FS paradigm) that relies on a Fair Scheduler network and assumes only selfish and non-collaborative end users. We rigorously define the properties of an ideal congestion control protocol and show that the FS paradigm allows to devise end-to-end congestion control protocols that meet almost all the properties of an ideal congestion control protocol. Moreover, the FS paradigm does not aversely impact the TCP flows. We show that the incremental deployment of the FS paradigm is feasible per ISP and leads to immediate benefits for the TCP flows. Our main contribution is the formal statement of the congestion control problem as a whole that allows to rigorously prove the validity of the FS paradigm. Moreover, we explain how to apply the FS paradigm for the design of new congestion control protocols, and we introduce as a pragmatic validation of the FS paradigm a new multicast congestion control protocol called PLM.