In the keynote entitled 'QoE Issues in P2P Video Streaming', Prof. Touradj Ebrahimi will provide an overview of the major issues and challenges for streaming of video content in peer-to-peer (P2P) environments.
P2P file sharing has been among one of the most widely used applications, and a considerable part of the Internet traffic in the last few years. Although all sorts of data (software, image, audio, video, etc.) have been shared in P2P networks, a growing interest in media streaming solutions over P2P has been taking place recently , giving birth to several operational systems, either in open source or as proprietary solutions and architectures . In addition, several recent studies indicate that a significant portion of the Internet traffic will be devoted to video streaming. For instance, CISCO predicts that the total amount of the Internet traffic will reach 767 exabytes, a ten-fold increase when compared to its 2008 level, of which, more than 90% will be devoted to video data! It is therefore only natural to assume that a significant part of P2P traffic will also be devoted to video streaming, as opposed to downloads, hence the importance of this topic.
Engines Behind the Growth of P2P Video Streaming
CISCO justifies the reason behind this tremendous growth in the Internet traffic, as a consequence of two main factors: 1) availability of better annotation, search and retrieval tools which allow for finding video content in a more efficient manner, and 2) widespread access to broadband Internet communication channels, which allows for higher quality video streaming, not only in standard definition, but also in high definition and even 3D. It is likely that the same factors will be also the engines behind the future growth of P2P video streaming, if several challenges in such environments are resolved efficiently.
Quality of Experience Issues in P2P
Streaming in P2P environments is considered as a potentially appealing solution, as it offers an intrinsic scalability, without requiring costly infrastructures. In fact, in P2P streaming, a consumer node can also act as a broadcaster, and the more users consume a given content in a network, the more bandwidth in the network will be devoted to it, further facilitating access to that content by more users. Until recently, P2P was mainly for downloading files, where most important issues were efficient search mechanisms that allow access to trusted and reliable nodes, and reasonable delay to download the data to one’s node. The constraints in a P2P streaming environment are more severe and concern a rather broad range of Quality of Experience issues, among which some have been explicitly identified as main challenges for its future developments . For instance, fidelity metrics that measure how closely a video content should be reproduced at a receiver when compared to an original sent by a transmitter are not anymore sufficient, and other metrics taking into account access delays, a major challenge in P2P streaming, and robustness to node terminations, become essential.
Furthermore, no-reference quality metrics are needed as part of optimization, procedures which require any node to decide how to manage its incoming and outgoing streams, so as to reduce other important QoE issues such as delays between broadcasting of a live event and its decoding at a consumer node, which can take up to several minutes in current solutions. Such QoE issues become even more challenging in mobile environments, when considerations such as power-consumption, usability, and context (location, situation, etc.) should also be taken into account.
References Yong Liu, Yang Guo and Chao Liang. A survey on peer-topeer video streaming systems. Peer-to-Peer Networking and Applications, Volume 1, Number 1, 18-28, (January 2008). DOI:10.1007/s12083-007-0006-y.
 Eric Setton and Bernd Girod. Peer-to-peer video streaming, Spinger, (October 2007), ISBN: 978-0387741147.