A game theoretic comparison of TCP and digital fountain based protocols

In this paper we analyze a novel paradigm of reliable communication which is not based on the traditional timeout-and-retransmit mechanism of TCP. Our approach, which we call FBP (Fountain Based Protocol), consists of using a digital fountain encoding which guarantees that duplicate packets are almost impossible. By using Game Theory, we analyze the behavior of TCP and FBP in the presence of congestion. We show that hosts using TCP have an incentive to switch to an FBP approach, obtaining a higher goodput. Furthermore, we also show that a Nash equilibrium occurs when all hosts use FBP (i.e., when FBP hosts act in an absolutely selfish manner injecting packets into the network as fast as they can and without any kind of congestion control approach). At this equilibrium, the performance of the network is similar to the performance obtained when all hosts comply with TCP. Regarding the interaction of hosts using FBP at different rates, our results show that the Nash equilibrium is reached when all hosts send at the highest possible rate, and, as before, that the performance of the network in such a case is similar to the obtained when all hosts comply with TCP.