A Survey of Peer- to -Peer Overlay Schemes: Effectiveness, Efficiency and Security
Recent Patents on Computer Science
In distributed computing, the peer-to-peer paradigm enables two or more entities to collaborate spontaneously in an overlay network of equals (peers) by using appropriate information and communication schemes without the necessity for central coordination. The key concept of the peer-to-peer paradigm is leveraging idle resources to do something useful, based on a collaborative approach. The increasing academic and industrial interest is resulting in the definition of standards and writing of
... ents. In this paper we propose a categorization for the peer-to-peer overlay schemes and a survey of the most popular ones, comparing each other with respect to effectiveness and security. Most of them have been or are being used in content sharing systems, that over the last few years have enjoyed explosive popularity. Others are used in parallel and distributed computing, massively multi-player gaming, Internet streaming, ambient intelligence, etc. Considering such a wide range of applications, we discuss the importance of reputation management in supporting trust management among peer participants. Search performance and consistency are two important measures for the sharing of dynamic contents (e.g. in P2P storage systems). Search performance concerns how fast the users locate and obtain copies of requested resources (time complexity) and how many nodes must be involved in that process (space complexity). Consistency concerns how old the acquired data (resource descriptions or shared content) are with respect to the actual available resources. Stability refers to the ability of the overlay scheme to guarantee the correctness of its functionalities regardless of the churn rate of the network. The churn rate is a measure of the number of peers joining and leaving the system over a specific period of time. Users of the peer-to-peer system join and leave the network randomly, which makes the overlay network dynamic and unstable in nature. This dynamical behavior of the peers frequently partitions the network into smaller fragments which results in the breakdown of communication among peers. Thus, design and tuning of the overlay scheme should be made taking into account different churn rate profiles, depending on the distributed application the scheme should support.