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PEER-TO-PEER NETWORKING

Soutrik GuptaBCA 3rd YearNetworking and CommunicationComputer NetworksA computer network or data network is a telecommunications network which allows computers to exchange data. In computer networks, networked computing devices pass data to each other along data connections (network links). Data is transferred in the form of packets. The connections between nodes are established using either cable media or wireless media. The best-known computer network is the Internet.

Computer NetworksComputer Networks are categorized into many different ways and into many different types of network.One way of categorizing network is by method of connectionThe two main types of connection methods are :

WiredNetworkWireless Network

Another way of categorizing network is by Scale of the network.Computer NetworksThe classification of network using network scale are:PAN : Personal Area Network

CAN : Campus Area Network

LAN : Local Area Network

MAN : Metropolitan Area NetworkWAN : Wide Area Network

SAN : Storage Area Network

VPN : Virtual Private Network

Which network to be used for a specific job is decided by the scale of jobComputer NetworksAnother way of categorizing network is by the architecture of the networkThe Three main architectures are:Active Networking

Client Server Networking

Peer To Peer Networking

Computer NetworksActive Networking: Active networking is a communication pattern that allows packets flowing through a network to dynamically modify the operation of the network.Client-Server Network: In the Client-Server model, two processes are involved, one on the client side and one on the server side. First client sends a message over the network to the server, the client then waits for a reply. When the server receives the request it performs the requested work and sends back a reply to the client. This network becomes unusable if for any reason the server is down.Peer-to-Peer Network : In the per-to-peer architecture individuals are connected to a loose group can communicate with others in the group. There is no need to distinguish clients the servers in this architecture. Every single node ( computers ) can communicate with all other computers in the network and the network wont be affected if a single node is down.Peer-To-Peer NetworkingAny type of network architecture that is composed of contributors that make a part of their resources available to other contributors as well as the connected members on the same network without the need for a server to oversee the transfer of the information is considered as a peer-to-peer network.A peer-to-peer networks architecture is generally formed dynamically by an ad-hoc type of addition of nodes, meaning the loss of a certain node does not have a significant impact on the rest of the network.This aspect of peer-to-peer networks gives the system the ability to easily scale to any size that may be need for a certain application.Regarding different types of peer-to-peer architecture, there are generally two major types, structured and unstructured. These two types of networks also contain even more specific underlying types of networks.Peer-To-Peer NetworkingUn Structured To be considered an unstructured peer-to-peer network, the network must not use any algorithm for organization or optimization of the network.For unstructured peer-to-peer networks there are three different models which include pure peer-to-peer networks, hybrid peer-to-peer networks, and centralized peer-to-peer networks.

In a pure peer-to-peer network, or sometimes called a purely decentralized network, all nodes are of equal ability meaning that there are no nodes that have any special infrastructure function that could affect the network.

The second type of unstructured peer-to-peer networks is called the hybrid peer-to-peer network.In this type of network, infrastructure nodes are allowed to exist and are often a type of central directory server.All clients connected to the network must connect to one of these servers.The central server maintains a table of registered user connection information (IP address, connection bandwidth etc.) and a table listing the files that each user holds and shares in the network, along with metadata descriptions of the files(e.g. filename, time of creation, etc.)A user that wishes to join the network must first contact the central directory server and report its files that wish to be shared. To find a file on this type of network, the user must send a request for that file to the directory server. The server then searches into database for said file and returns a list of users that possess that file. The requesting user then opens a direct connection with the list of users and downloads the file.Peer-To-Peer NetworkingUn Structured

The final type of unstructured peer-to-peer network is called a centralized peer-to-peer network.These centralized peer-to-peer networks are very similar to the pure peer-to-peer networks except for the added concept of supernodes.These supernodes are nodes that are dynamically assigned the task of servicing a small subpart of the peer network by indexing and caching files contained therein.Peers are chosen to be supernode automatically if said peers bandwidth and processing power is sufficient. All queries for files on this type of network are sent to and processed by these supernodes.Peer-To-Peer NetworkingUn Structured

Peer-To-Peer NetworkingStructured Structured peer-to-peer networks generally hold the traits of using some type of algorithm for organization or optimization of the network.Structured peer-to-peer networks use some type of global protocol to ensure that any node in the network can proficiently route a search to some peer that has a desired file.

Distributed hash tables are a class of decentralized distributed systems that provide a lookup service similar to that of a hash table.Pairs, key and value, are stored in the distributed has table and any connected node can proficiently retrieve the value associated with a given key.Maintaining the mapping from keys to values is the responsibility of each of the nodes in the network.

This is done in such a way that a change to the set of peers causes a negligible amount of disruption to the rest of the network.The most popular example of a network using a distributed hash table is Bit Torrents distributed tracker.Peer-To-Peer NetworkingAdvantages and Limitation One of the major advantages to a peer-to-peer network is that each time a new node is connected to the network the total capacity of the system increases.This point differs from the client-server model standpoint since the addition of new nodes to a network that connects to a set number of servers could possibly slow data transfers for all of the connected users.Another advantage in regards to a pure peer-to-peer network is that there is no single point of failure in the network.When compared to the client-server model on this point if the server fails the network is brought down since the server is unable to relay information to the connected nodes.On the pure peer-to-peer side of the topic, if one of the nodes fails the rest of the nodes are ablePeer-To-Peer NetworkingAdvantages and Limitation One of the weaknesses of peer-to-peer networks is that of security. Generally speaking peer-to-peer networks are more susceptible to security problems.Another disadvantage of peer-to-peer networks is the high bandwidth usage required. This high bandwidth usage has lead to Internet Service Providers starting to throttle, or limit, peer-to-peer traffic.On the other side, the server-client model usually consists of short quick bursts of data.An emerging solution to this problem is called peer-to-peer caching.Peer-to-peer caching is defined as a network traffic management service that accelerates data delivered over peer-to-peer networks by means of the Internet Service Provider storing pieces of files that are most accessed by peer-to-peer users.Another disadvantage of peer-to-peer networks is the high bandwidth usage required. This high bandwidth usage has lead to Internet Service Providers starting to throttle, or limit, peer-to-peer traffic.Peer-to-Peer NetworkingApplicationsSome popular applications of peer-to-peer networking are:

File SharingMedia StreamingGrid ComputingTelevision StreamingOne of the very popular use of Peer-to-Peer technology is Grid Computing.

Grid computing applications share processing power over a networking to accomplish some type of goal.

The two most popular grid computing applications include BOINC and Folding@Home.Thank You