Adaptation of BitTorrent for Heterogeneous Networks and ISPs´ Constraints

The Bittorrent P2P (Peer-to-Peer) network is now well-known and widely used. In Europe, it is mainly used with people connected to ADSL networks. However, with the emergence of various access networks with various capabilities (bandwidth, delay, etc.), we might wonder if Bittorrent is well suited to those heterogeneous networks. Moreover, some mobile 3G network operators even forbid the use of P2P networks in their contract (and eventually block it) because it overloads the shared wireless links. This heterogeneity of networks as well as the the possibility that ISPs block P2P traffic, could have an impact on the Bittorrent system. This is what this paper addresses with simulations of a swarm composed of peers, connected to heterogeneous access networks. The simulations we performed enable us to highlight that the Bittorrent protocol is not optimised for being used from various ISP access networks and thus we propose a simple adaptation of the Bittorrent algorithm, which classifies peers, depending on their access network capabilities and unchokes peers, based on their class and no more independently. This adapted algorithm allows to maintain a good QoE (Quality of Experience) to end-users while satisfying ISPs´ constraints since it does no longer load the wireless access network.