This paper is under submission. To obtain a copy for the group discussion, contact schulman@cs.umd.edu.

Broadcast is one of the fundamental communication primitives, and yet it is constrained in the Internet to individual links or subnets. In this paper, we propose an architecture that allows any host to broadcast arbitrary data to large geographic areas. Our architecture exposes the policy concerns of sharing a wide-area, resource-constrained broadcast medium—who gets to send, what data should they send, and how do receivers know what to listen for?—and provides
mechanisms that allow these issues to be resolved in-band.

We ground our architecture with an implementation that we show is feasible to deploy today. Specifically, we investigate
complementing existing Internet links with the FM Radio Data System (RDS), and demonstrate that even a modest
deployment could cover millions of hosts in the continental US. Seamlessly integrating FM transmissions into existing
end-hosts raises its own challenges, which we address with the design of an inexpensive, embeddable receiver.

With several application case studies—including anonymous communication, fault tolerance, and content distribution—
we show that system designers currently emulate broadcast via unicast, and that having access to a true broadcast primitive can simplify protocol design and implementation.