Replication has been a popular technique that provides increased data or service availability in case of failure or crash of server or the node which is responsible to serve the requested data or service. Replication improves data availability, data accessibility, fault tolerance and reliability of the network that is targeted to provide data or service to its clients. The concept of replication and its various techniques have its footprint which is decade older. Numerous techniques can be found in the literature for various network or system environments. With the existence of rapid changes in computing paradigm and evolution of networks such as distributed, Cluster, Grid, Cloud, Wired, Wireless, Mobile and MANET, the way the replication performed is also changed. The entity or the unit of replication that is being replicated depends upon the choice, such as a simple data object, a data block, a Database file, Domain name information, Multimedia contents, web files and web services etc. This paper analyses the various approaches for replication in different computing or network environments with varying requirements and presents the summary of each approach and identifies the scope for possible extensions in all dimensions which would be a vital resource for researchers for future work in replication in the emerging area such as cloud. © Research India Publications.