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Computer networks

The role of networks

Independently, the computers can accomplish almost anything, but if their resources are shared, computers become more efficient. For example, all the computers in an office can be connected to one printer, saving the cost of acquisition for many printers.

As such, the main goal of computer networks is to enable the sharing of resources. These resources are very diverse: printer, scanner, storage space for files and information.


From the point of view of resource sharing, computers in a traditional network fall into servers that provide (serve) resources, and customers who use them.

The alternative to the client-server networks are the P2P (Peer-to-Peer) networks, in which computers have the same role. Their appearance coincided with the development of applications such as Napster, for file sharing.

Data transmission networks

The main channels used for data transmission in the network are:

  • Telephone lines (including ISDN);
  • Coaxial cable – formerly the coaxial cable used was (very similar to the TV antenna), but lately it has become the de facto standard UTP (Unshielded Twisted Pairs)
  • Optical fiber – allows for much higher capacities for data transmission, is generally used between important nodes in the network or between networks;
  • Satellite – the same way as the signal transmitted by satellite TV;
  • Wireless (WLAN or Wi-Fi4) – the most recent connection method in recent years, has seen an unprecedented rise in popularity. This popularity is due to just its main characteristics: lack of cables.

Types of networks

After scale / scope, networks can be:

  • LAN (Local Area Network), in local networks, which are limited to the area of a department, a building on the campus of a school / university, or within an enterprise. Networks are the most common and usually do not exceed a few hundred square meters.
  • MAN (Metropolitan Area Network) in more extensive networks, covering an area towns / cities, interconnecting LANs in that locality. Some of these networks are initiated and managed by local government.
  • WAN (Wide Area Network), networks covering a wide and wider, such as a country or continent.
  • GAN (Global Area Network), the global network, the Internet.

By type of target users, there are three types of networks:

  • Internet
  • Intranet
  • Extranet


Internet is a global network of interconnected computers to put together information and other resources. Any computer connected to the Internet can communicate with any other computer connected to the Internet, so the Internet can be viewed as a huge network made up of millions of computers worldwide network (MAN + LAN + WAN).

A network consists of computers that have a client and server computer role (client-server architecture). A server is a computer that provides services such as distributing e-mails or web pages, while the client is a computer that connects to the server to request and receive information from or to access available resources there.

Every computer connected to the Internet is assigned a unique identification number, which is the Internet address. Because the user holds more difficult a number, it is backed by a name known as domain name.

Internet is a decentralized network, meaning that there is no institution or State to hold and govern his operation. Financial and logistical support is made by companies they access and its management from a technical standpoint is supervised by a committee called ICANN (Internet Corporation for Assigned Names and Numbers).

Because basically everyone in the world can connect to the Internet without restrictions, it is considered as public.


An intranet is a private network inside a company or institution, which transmit documents, allowing access to the database, ensure staff training and communication between employees and distributed software. Unlike the Internet, Intranet is serving only the staff of the organization and it is therefore necessary to implement a password system that ensures privacy.

Computers within the Intranet are not accessible outside the network, but can access both internal resources and resources from Internet servers. This is possible using a device called “firewall”.


Extranet is an extension of Intranet network that uses Internet technology to connect private intranet networks of organizations that want to work together to share an important resource – information. The extranet provides structured information on three levels: public, private and mixed.


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