To Code or Not to Code: Rate Optimality of Network Coding versus Routing in Peer-to-Peer Networks

Peer-to-peer (P2P) systems have provided a scalable and cost effective way for file sharing and multimedia streaming in the past decade. The implementation of P2P systems usually involves two transmission schemes: routing (store-and-forward), and network coding. In this paper, we make a theoretical investigation of the rate that can be achieved by routing vs. network coding. We model P2P networks as node-capacitated networks with constraints on both node upload capacity and node download capacity. We compare routing and network coding for unicast, multicast and broadcast transmissions with both single-source scenario and multi-source scenario. Our results present not only a unification of existing results, but also extensions to new scenarios for node-capacitated networks.