Transport Optimization in Peer-to-Peer Networks

The peer-to-peer networking concept has revolutionized the cost structure of Internet data dissemination by making large scale content delivery with low server cost feasible. In a peer-to-peer network, the total upload capacity increases with the number of down loaders instead of staying constant as in a client-server architecture, making it highly scalable. Despite of its importance, the problem of efficient data transport in a peer-to-peer network is still an open issue, mainly due to its complex combinatorial structure. In the presented work, we formulate the problem of optimizing a peer-to-peer download with respect to its make span (time until all peers finish downloading)as a mixed integer linear program. Other than previous studies, we consider the case of arbitrary heterogeneous uplink and downlink capacities of the peers. Moreover, we do not consider the fluid limit case but allow the file to be subdivided in finitely many chunks. On the one hand, our results allow to infer the capacity of a peer-to-peer network, providing a benchmark for performance analysis of existing peer-to-peer protocols. On the other hand, we believe that our results build a step towards the development of efficient algorithms serving as a base for the design of data transport protocols leveraging the peer-to-peer concept.