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Computer Science Colloquia

Trust is a cornerstone of most congestion control protocols deployed in the Internet today. Unfortunately, with the growth and commercialization of the Internet, the assumption of universal trust is no longer tenable. A communicating entity can misbehave to elicit a self-beneficial bandwidth allocation. Thus, design of congestion control protocols that are robust to such misbehavior has become an important research area.

This talk discusses design of robust congestion control for a multicast service in the presence of distrusted receivers. We show that protection against receiver misbehavior is harder than in unicast and poses new research challenges. After presenting our threat model, we classify vulnerabilities of existing multicast congestion control protocols to receiver attacks.

Then, we focus on a specific attack of inflated subscription which enables a misbehaving multicast receiver to acquire data at an unfairly high rate at the expense of competing traffic. We argue that robustness to inflated subscription requires a mechanism for restricted group access where eligibility to access a multicast group is a function of the congestion status. Our design guards access to multicast groups with dynamic keys and consists of two independent components: DELTA (Distribution of ELigibility To Access) - a novel method for in-band distribution of the keys to receivers that are eligible to access the groups according to the congestion control protocol, and SIGMA (Secure Internet Group Management Architecture) - a generic architecture for key-based group access at edge routers. We conclude by arguing that intrinsically different design requirements imposed by distrusted environments point to the need for an integrative alternative to the traditional layered approach to networking.