04-01-2013, 12:31 PM
Peer-to-Peer Network
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ABSTRACT
The subject of “P2P” attracts much interest in the networking community, even though many disagree on its exact meaning. P2P technology promises to radically change the future of networking, yet the concept has existed for years. P2P also raises interesting cultural issues despite its “policy free” architecture. All in all, these apparent paradoxes of P2P only add to its mystique.
Peer to peer networks are gaining widespread acceptance as a scalable and robust model for data-sharing Internet applications. Building on the successful, though technically deficient, legacy of Napster and Gnutella, these systems strive to provide a scalable, decentralized, fault-tolerant, and self-stabilizing architecture for large scale data sharing applications. The broad vision of P2P systems, however, goes well beyond the sharing of music files.
INTRODUCTION
Peer-to-peer is a type of network in which each work-station has equivalent capabilities and responsibilities. This differs from client/server architecture in which some computers are dedicated to serve others. Peer-to-peer (P2P) networks are increasingly becoming popular because they offer opportunities for real-time communication, ad-hoc collaboration and information sharing in a large-scale distributed environment. Peer-to-peer computing is defined as the sharing of computer resources and information through direct exchange.The most distinct characteristic of P2P computing is that there is symmetric communication between the peers; each peer has both a client and a server role. The advantages of the P2P systems are multi-dimensional; they improve scalability by enabling direct and real timesharing of services and information; enable knowledge sharing by aggregating information and resources from nodes that are located on geographically distributed and potentially heterogeneous platforms; and, provide high availability by eliminating the need for a single centralized component.
Historical Development
Before discussing the history of peer-to-peer computing (P2P), we must first decide what it is. According to Whatis.com, P2P is "A communications model in which each party has the same capabilities and either party can initiate a communication session". So we could define P2P as direct communication or collaboration (mostly file-sharing) between computers, where none are simply client or server, but all machines are equals - peers. In that case, P2P is at least 30 years old. With this definition, communication between two servers is P2P. It could even be argued that telephones and email are P2P.
Past
What came before P2P?
Before we had P2P, one of the big favorites for companies to use was B2C. B2C stands for "Business-To-Consumer".
The P2P Overnight Explosion
The history of P2P cannot be recounted without reference to Napster, the software that brought P2P into the mainstream. Napster became the single most popular P2P application literally overnight.
Napster's winning idea was in giving P2P, for free, to the masses. At the same time as Napster was released three factors greatly increased its mass popularity - higher bandwidth, more powerful desktop processors and cheaper storage. Since the Napster case, many other P2P programs have surfaced including Gnutella, KaZaa and Winmp.
Present
The growth in the number of P2P technology users has been exponential since the birth of Napster. The vacuum left by Napster's demise has been filled by numerous other companies/applications, with Kazaa and Gnutella dominating the market. It has been reported that these two account for between 40% and 60% of all traffic on the Internet. In recent years we have seen P2P technologies being embraced by large companies trying to tap its vast potential. Two of the more notable examples of this are Deloitte & Touché, and Intel. Central databases are no longer required when using P2P. This means it can be less expensive and far easier to scale. Intel has been using P2P since 1992, thus avoiding the need for a large server. Traditional databases are still commonplace today, but as increasing numbers of companies follow the example of organizations like Intel, such databases could be overtaken and replaced by P2P.
Future
It's hard to know what the future of P2P is until the legal situation becomes clear. Companies will have to expend significant resources to protect themselves against lawsuits. There will always be illegal file-sharing and copyright infringement, but these will be at the periphery. A lot depends on the legislation drawn up by governments in response to P2P. Searching is a definite area in which P2P will prosper in the future. P2P allows queries to be sent to a number of machines. If the initial search is unsuccessful, the query is passed on by each of the original machines to a number of further machines. Thus the search area increases exponentially until a result is found. This eliminates the need for a huge central search engine. The big guns such as Intel, Microsoft and Xerox have recently stressed the potential of P2P and the likelihood is that P2P will continue to be adopted by big business as a cheaper way of storing and sharing files internally.
PEER TO PEER NETWORKS
The current article deals with the definition of Peer-to-peer network and how it differs from Client/server network. It also describes advantages and disadvantages of Client/Server and p2p networks.
What is peer to peer?
P2P in some sense is decentralization – moving away from monolithic central hub-spoke model to the decentralized device to device or service to service model. The devices can be edge devices or they could be servers talking to each other to make a server overlay. Even though traditional definitions of P2P include similar devices at the edges communicating without *any* central system.
Traditional Peer-to-Peer
The P2P acronym technically stands for "peer-to-peer" computer networking. Webopedia defines P2P as
“A type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. "
This definition captures the traditional meaning of peer-to-peer networking. Computers in a workgroup, or home computers, are configured for the sharing of resources such as files and printers.
P2P with simple Discovery server
Figure 2 represents the configuration of a P2P network with simple discovery server. In this configuration there is one central server that is used to discover locations of other peers. Usually this is implemented so that when application starts it registers to discovery server that keeps track of machines that are available. When a peer wants to contact another it first queries discovery server for a list of locations and then one at the time makes queries directly to peers in the list.
What is Freenet?
Freenet is a completely distributed decentralized peer-to-peer system. It has no notion of global coordination at all. Communication is handled entirely by peers operating at a global level.
A node is simply a computer that is running the Freenet software, and all nodes are treated as equals by the network. Each node maintains its own local data store which it makes available to the network for reading and writing, as well as dynamic routing table containing addresses of other nodes and the keys that they are thought to hold. This removes any single point of failure or control.
It is intended that most users of the system will run nodes, to
- provide security guarantees against inadvertently using a hostile node
- increase the storage capacity available to the network as a whole.
Freenet enables users to share unused disk space, just like systems like distributed.net enable ordinary users to share unused CPU cycles. The system operates at the application layer and assumes the existence of a secure transport layer, although it is transport-independent.
CONCLUSION
It seems that P2P technology is still evolving and all of its capabilities haven’t even been found yet. However, there is no doubt that P2P is here to stay and quite likely it will replace client/server model in the near future. P2P communication model seems to fit perfectly to home environments where there are many different devices and it is crucial that they are able to communicate with each other. Using P2P model home networks can orient themselves to the most effective form and P2P networks become much cheaper than centrally managed networks. Interoperability of different digital devices definitely is something that has been waited for and it opens huge amount of possibilities when designing home of the future.