On the impact of the initial peer list in P2P live streaming applications: the case of Sopcast

The acronym P2PTV, which stands for Peer-to-Peer Television, refers to P2P applications that enable multimedia contents broadcasting through the Internet. These applications have become very popular due to their capability of delivering material with or without copyright protection to a large audience. In P2PTV applications, the start-up phase - from the moment the client joins an existing channel to the moment she can start viewing the content - is crucial. A long time before showing the first images of a video, can make a user switch to another channel or to an alternative P2P application. Later on, the same user behavior is expected in case of frozen images. In this paper, we consider the case of Sopcast, which is currently one of the most popular P2PTV applications. Sopcast recently modified its start-up algorithms. We uncover the details of the new strategy adopted by Sopcast and evaluate its performance as a function of the swarm size and the geographic source of the content.