Robust Congestion Control for Multicast: Challenges and Opportunities

Trust is the foundation of most congestion control protocols developed and deployed in the Internet today. Unfortunately, with the growth of the Internet, the assumption of universal trust is no longer tenable. A communicating entity can misbehave to obtain a self-beneficial bandwidth allocation. Thus, design of congestion control protocols that are robust to such misbehavior has become an important research area. In this paper, we discuss the specific problem of designing robust congestion control for multicast in the presence of untrusted hosts. We examine IP and peer-to-peer instantiations of the multicast service. For both cases, we show that protection against host misbehavior is harder than in unicast and poses new research challenges. We outline possible solutions for designing robust multicast congestion control protocols. Further, we argue that intrinsically different design requirements imposed by untrusted environments point to the need for exploring an integrative alternative to the traditional layered network architecture.