  Distributed systems with different levels of dependence to central services
have been designed and used during recent years. Pure peer-to-peer systems
among distributed systems have no dependence on a central resource. DHT is one
of the main techniques behind these systems resulting into failure tolerant
systems which are also able to isolate continuous changes to the network to a
small section of it and therefore making it possible to scale up such networks
to millions of nodes. This survey takes a look at P2P in general and DHT
algorithms and implementations in more detail.
