Point to Point Architecture
The term peer means equal which can be informally interpreted as a process with capability similar to the other processes with process communicates. In the context of P2P networks a peer process acts as a client process and at the same time a server process for the same functions. For example a process that downloads files from other and meanwhile the process shared files for others to download is a peer process in file downloading uploading. There is no distinction between these processes in terms of which is providing or using services. Peer processes communicate with each other in a symmetric pattern. Note that the function that a peer process requests and offer must by the same within the context of a given applications.
In P2P architecture there is not an always on server at the centre of the applications. Instead arbitrary pairs of hosts called peers communicate directly with each other because the peers communicate without passing through some special server, the architecture is called peer to peer. The P2P architecture is illustrated in figure 3.1 (b).
One of the greatest strengths of the P2P architecture is its scalability. For example in a P2P file sharing application millions of peers may participate in the file sharing community with each one functioning as a server and contributing resources files and also community. This while each peer will generals work load by requesting files, and also adds serves capacity to the system sub responding to the requests of other peers. Thus increases the demand but also increase service capacity on the other hand because of the highly distributed and decentralized nature of P2P applications they can be difficult to manage.
figure client Server Application P2P architecture