A Computer Network Is Defined As

a computer network is defined as

The computer network is a system that consists of computers, software and other networking devices that work together to achieve a common goal. The purpose of the network is the computer:

* Sharing of resources: for example, shared use of printers, CPU, memory, hard drive

* Communication: eg electronic mail, instant messaging, chat

* Access to information: for example web browsing

In order to achieve the same purpose, every piece of computer network request and provide the service (service). The party requesting / receiving the service are called clients (client) and providing / sending service called the waiter (server). This architecture is called client-server systems, and is used in almost all computer network applications.

[Edit] Classification

Based on the scale:

* Local Area Network (LAN): A computer network that connects a computer to another computer with a limited range.

* Metropolitant Area Network (MAN): the same principle with the LAN, only the distance is larger, which is 10-50 km.

* Wide Area Network (WAN): the distance between cities, countries, and continents. This is the same with the Internet.

By function: Basically any existing computer network that serves as a client and server. But there is a network that has a dedicated computer as a server and the other as a client. There is also a computer that does not have a specific function as a server only. Because it is based on function then there are two types of computer networks:

* Client-server

That is a computer network with a dedicated computer as a server. A service / service can be provided by a computer or more. An example is a domain such www.detik.com served by many of the web server computer. Or it could be a lot of service / services provided by a single computer. Examples are jtk.polban.ac.id server which is a computer with a multi service that mail server, web server, file server, database server and others.

* Peer-to-peer

That is a computer network in which each host can be a server and a client simultaneously. For example, the file sharing between computers on the network Windows Network Neighbourhood there are 5 computers (we named A, B, C, D and E) are granted access to the files they have. At one point A to access the file share of B named data_nilai.xls and also gives access to the file soal_uas.doc C. When accessing a file from B then A serves as a client and as a give file access to C then A is acting as a server. Both functions were performed by the same A network like this so called peer to peer.

Based on the network topology, computer networks can be distinguished:

* Topology bus

* The star topology

* Topology Ring

* Topology mesh

* Topology tree

* Topology linear

Based on the criteria, a computer network can be divided into four, namely:

1. Based on the distribution of sources of information / data

* Centralized Network

This network consists of client and server computer where the client computer that serves as an intermediary to access sources of information / data from one computer server

* Distributed Networks

Is a combination of several centralized network so that there are multiple server computers interconnected by a network client to establish a specific system.

2. Based on the geographic range is divided into:

* Network LAN

is a network that connects two computers or more in coverage such as laboratories, offices, and in one cafe.

* Network MAN

Is the tissue that covers the major cities and their local area. Examples of local telephone networks, cellular telephone systems, as well as some ISPs relay networks

* Network WAN

Is a network with worldwide coverage. For example, a network of PT Telkom, PT. Indosat, as well as Satelindo GSM Mobile, Telkomsel, and much more.

3. Based on the roles and relationships of each computer in processing data.

* Client-Server Network

In this network there are one or more computer servers and client computers. The computer that will be the server computer and a client computer and changed through software on the network protocol. Client computer as an intermediary to be able to access data on the server computer while the computer server providing the information required by the client computer.

* Peer-to-peer

In this network there are no computer client or server computer for all computers can do the delivery and receipt of information so that all the computers to function as a client as well as server.

4. Based on the data transmission medium

* Wired Network (Wired Network)

In this network, to connect one computer to another computer in the form required connecting a network cable. Cable network functions to send information in the form of electrical signals between the network computer.

* Wireless Network (WI-FI)

Is a network of the medium in the form of electromagnetic waves. In this network cables are not required to connect between computers because it uses electromagnetic waves will transmit signal information between networked computers.