Future Internet Congestion Control: The Diminishing Feedback Problem

Abstract: It is increasingly difficult for Internet congestion control mechanisms to obtain the feedback that they need. This lack of feedback can have severe performance implications, and it is bound to become worse. In the long run, the problem may only be fixable by fundamentally changing the way congestion control is done in the Internet. We substantiate this claim by looking at the evolution of the Internet's infrastructure over the past thirty years, and by examining the most common behavior of Internet traffic. Considering the goals that congestion control mechanisms are intended to address, and taking into account contextual developments in the Internet ecosystem, we arrive at conclusions and recommendations about possible future congestion control design directions. In particular, we argue that congestion control mechanisms should move away from their strict "end-to-end" adherence. This change would benefit from avoiding a "one size fits all circumstances" approach, and moving towards a more selective set of mechanisms that will result in a better performing Internet. We will also discuss how this future vision differs from today's use of Performance Enhancing Proxies (PEPs).