Abstract

This paper presents the core of a distributed document-sharing environment with particular focus on distributed searching and retrieval of research papers. Problems with Current p2p Systems Despite their obvious popularity, systems like Napster and Gnutella suffer from many problems. Napster uses centralised indexing servers, an approach which is vulnerable to failure. Gnutella avoids Napsters weakness by using a decentralised indexing technique, however this leaves Gnutella with the problem of locating objects within its network. Gnutella uses a flood-based search technique where each search request blindly hops across the network from one node to another searching for the requested file. The search request will only reach an ever-decreasing section of the network as more users join; as a result this technique doesnt scale very well. In recent times, more scalable object location algorithms have emerged that are based on Distributed Hashtables (DHT). Let us consider these useful constructs and how they can be used to facilitate searches in a distributed environment. 3 Existing Structured p2p Overlays Based originally on the research of Plaxton et al in the late 1990s [4], DHT overlay network implementations first appeared during 2001. Projects such as Pastry [5], Tapestry [6], CAN [7] and Chord [8], all produced implementations that adhered to the principles of P2P, decentralisation, robustness and scalability. These systems may be used to form the foundation for functional p2p systems. They provide a routing substrate; a mechanism that efficiently locates objects within a certain number of routing hops. The subject of keyword searching is of particular importance if such DHT systems are to become part of the more mainstream p2p systems ...

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