Broadcasting on Large Scale Heterogeneous Platforms with Connectivity Artifacts under the Bounded Multi-port Model

We consider the classical problem of broadcasting a large message at an optimal rate in a large scale distributed network. The main novelty of our approach is that we consider that the set of participating nodes can be split into two parts: "green" nodes that stay in the open-Internet and "red" nodes that lie behind firewalls or NATs. Two red nodes cannot communicate directly, but rather need to use a green node as a gateway for transmitting a message. In this context, we are interested in both maximizing the throughput (i.e. the rate at which nodes receive the message) and minimizing the degree at the participating nodes, i.e. the number of TCP connections they must handle simultaneously. We consider both cyclic and a cyclic solutions for the flow graph. In the cyclic case, our main contributions are a closed form formula for the optimal cyclic throughput and the proof that the optimal solution may require arbitrarily large degrees. In the a cyclic case, we propose an algorithm to achieve the optimal throughput with low degree. Then, we prove a worst case ratio between the optimal a cyclic and cyclic throughput and show through simulations that this ratio is on average very close to 1, which makes a cyclic solutions efficient both in terms of throughput and of number of connections.