Television and the Internet have proven to be a popular combination for both broadcasters and viewers. Because of this popularity they are increasingly facing the consequences of central bottlenecks, which could be overcome by taking a different approach: Peer-to-Peer (P2P) technology. However, P2P systems can only be successful with as much cooperation among as many users as possible. This chapter explains how this cooperation is hard to enforce, and how inducing it might be more successful. Relevant psychological theories are listed that can be used to induce this user cooperation, along with possible applications of cooperation inducing mechanisms for Peer-to-Peer Television (P2P-TV) systems. The authors aim to provide practical criteria along which these mechanisms can be evaluated on their contribution to social activity in P2P-TV systems.
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The combination of Television and Internet is expanding traditional broadcasts with flexible, nearly unlimited access to content and narrowcasting of niche content. The movement beyond the channel model frees viewers from fixed schedules and gets them faster and more dynamic access to more content, including large quantities of user generated content. Probably the best example at this moment is YouTube.com, which initiated large-scale production and distribution of user generated content. YouTube.com and similar video distribution systems, however, make use of traditional client-server architectures, requiring the maintenance of large and expensive servers. The main drawback is that they are unsuitable for large amounts of viewers trying to access the same video content at the same time, resulting in reduced quality-of-service (QoS) and availability of content, plus delays and increased download times. An interesting alternative for broadcasters to distribute up to HDTV quality content to millions of viewers in a short period of time is Peer-to-Peer (P2P) technology. An explanation of P2P technology can be found in Answer.com (2008). Instead of a large central server sending the complete file to all interested clients, a P2P system allows broadcasters to reach the same clients by just sending parts of one copy to a limited number of clients and having them distribute the file by exchanging these parts with other interested clients, or ‘peers’ in terminology of P2P technology, until each peer has the complete file. This illustrates one aspect of P2P technology, namely the injection of content. See section User Cooperation in P2P-TV Systems for more details.
A recent white paper by Cisco (2008) forecasts that during the coming three years P2P traffic will grow at about 30 percent per year with the increasing use of P2P for standard-definition video file exchange, and advent of high-definition video files and television content exchange. Figure 1 shows Cisco’s forecasts about consumer Internet traffic up to 2011 (Cisco, 2008) in which P2P clearly dominates and Internet video to PC and TV is rising.
Figure 1. Global consumer Internet traffic 2007-2011 forecast (source: Cisco, 2008)
In recent years, the number of initiatives focusing on combining P2P with TV has grown rapidly. Examples are Joost.com, Babelgum.com, Livestation.com, Sopcast.com, PPLive.com, and Tribler.org (Wang et al., 2008). The latter is a system especially developed to investigate means to distribute and share large multimedia data. We will further elaborate on Tribler in the section Tribler and User Cooperation but first discuss the advantages of P2P technology and its challenges.
Both users and broadcasters benefit from P2P technology for a number of reasons. First of all, P2P technology yields low cost of ownership of content, because it aggregates distributed resources through smart interoperability. One-click uploading and near simultaneous distribution to thousands of viewers of user-generated content become possible with hardly any costs involved. Secondly, P2P technology is a promising approach in that television broadcasters do not need expensive and high maintenance central servers. Existing network connections plus infrastructure can be used and any maintenance effort is distributed over the users. It can be used for distributing large files among large amounts of viewers simultaneously.