  P2P computing lifts taxing issues in various areas of computer science. The
largely used decentralized unstructured P2P systems are ad hoc in nature and
present a number of research challenges. In this paper, we provide a
comprehensive theoretical survey of various state-of-the-art search and
replication schemes in unstructured P2P networks for file-sharing applications.
The classifications of search and replication techniques and their advantages
and disadvantages are briefly explained. Finally, the various issues on
searching and replication for unstructured P2P networks are discussed.
