Investigation and Evaluation of Upload and Download Allocation Strategies for P2P Video Streaming

Increasing bandwidth demand for online video streaming is posing challenges and opportunities for content delivery on the Internet. Studies, such as [2], show that Internet traffic for video delivery is increasing despite its quality being usually lower than for television. Reasons for that include the on-demand behavior, community participation, possibility of interactivity, creation of content by users, and availability of media worldwide.

Peer-to-peer (P2P) networks offer the possibility of distributing bandwidth usage to reduce bandwidth bottleneck on source, besides making network more robust against occasional failures [7]. Networks such as BitTorrent [3], SopCast [10] are already a success on the field of P2P video distribution.

LiveShift is a P2P video streaming application developed by the CSG group at the University of Zurich. The application, implemented in Java, supports both live streaming and video-on-demand in an integrated manner. While video is transmitted through the peer-to-peer network in a live fashion, all peers participate in distributed storage. This adds the ability to replay time-shifted streams from other peers in a distributed and scalable manner.

There are important challenges in allocating upload and download capacity of peers, especially due to lack of a global view of the system and of unstability of peers. It is unclear what are optimal strategies that would maximize the welfare of peers in the system, ultimately reflected in Quality-of-Experience (QoE) for the end user.

Besides availability challenges normally present in P2P systems, a P2P video streaming system has special requirements. Playback must be uniform, in the sense that having scattered short-length streams is not acceptable. The real-time nature of video streaming makes quick decisions very important.

The objective of this thesis is to investigate, design, implement, and evaluate upload and download allocation strategies for video streams in the LiveShift application. The design must offer a good trade-off among QoE and overhead. The mechanisms that must be defined are download and upload peer selection, including number of upload slots offered. Further optimizations can be made, for example, by taking advantage of the fact that peers may suggest candidates to other peers.