Gnutella's service announcement in March 2000 stirred worldwide interest by referring to P2P model. Basically, the P2P model needs not the broker "the centralized management server" that until now has figured so importantly in prevailing business models, and offers a new approach that enables peers such as end terminals to discover out and locate other suitable peers on their own without going through an intermediary server. It seems clear that the wealth of content made available by peer-to-peer systems like Gnutella and Freenet have spurred many authors into considering how meta-data might be used to support more effective search in a distributed environment. This paper has reviewed a number of these systems and attempted to identify some common themes. At this time the major division between the different approaches is the use of a hash-based routing scheme.

This paper outlines and analyses major P2P technologies currently being actively studied at various research organisations or already in use in both business and personal environments. Various technical features of P2P as well as its history and market trends are shown. P2P principles focussing on discovery and network-organisational mechanisms of major P2P systems such as JXTA, SIONet, Freenet, and Chord are first summarised. Also, other technical issues related to delivery, network control, security, digital rights management, and distributed computing are described. Then, P2P technologies to promote next-generation community networks with autonomous and intelligent characteristics are addressed. Based on these, P2P applications are analysed and some examples are shown. Studies of P2P traffic measurement, which is difficult by using traditional evaluation methods, are taken up to consider total network design in the P2P era.