A computer network is nothing more than a network composed of personal computers, smartphones, tablets, etc. In general, any electronic device equipped with a network card can be part of a computer network or a computer network.

Definition

A computer network is made up of a set of nodes interconnected via a communication channel. The main purpose of a computer network is to share information between the computers connected to the network.

A node is a PC, a notebook, a router, or another hardware device, such as a printer. In order for each node to exchange information with another node, it is necessary to have a network. Each of them must be equipped with a network card.

A communication channel is any transmission medium used to transmit the information that nodes exchange. If the transmission medium is air, we speak of wireless networks; if the transmission medium is a cable, we speak of wired networks.

Transmission of Information

In computer networks, there is always at least one sending node and one receiving node, which use a communication channel to exchange data.

Naturally, for communication to be effective, it cannot be based on improvisation but must be regulated through what we define as a protocol. A network protocol is defined as a set of rules and actions that two or more entities that want to communicate with each other must apply and follow to exchange data.

Regarding the communication channel, we can distinguish three different modes of channel use:

• simplex - transmission can only occur from the sender to the receiver and not vice versa;
• duplex - transmission can occur from the sender to the receiver and vice versa, but not at the same time;
• full-duplex - transmission can occur from the sender to the receiver and vice versa, even simultaneously.

If we refer to the simplex mode, we mean: Finally, we can distinguish two communication categories:

• Connection-oriented mode. In this mode, before sending data, the sender and receiver must establish a connection. This implies, for example, that the receiver is already prepared to receive the data and any intermediate nodes through which the communication will pass have already been identified.
• Connectionless mode. In this mode, the sender sends the data without first establishing a connection with the recipient. It is therefore a simple mode, but it can happen that the receiver is "caught by surprise" by the sending and therefore all or part of the transmission can be delayed. fail.

In general, it can be said that connection-oriented mode is a reliable data transmission method, but this reliability is achieved at the cost of greater complexity, which is necessary for the preliminary establishment of the connection.

Classification of networks by size

One way to classify networks uses their size. According to this criterion, networks can be divided into:

• Personal Area Networks. A PAN (Personal Area Network) is a typically personal network, used to connect nodes that are typically within a few meters (no more than ten). As the name suggests, it is used to connect two or more devices together. personal devices such as smartphones, earphones, smartwatches, notebooks, etc.
• Local Area Networks. A LAN (Local Area Network) is a typically private network, used to connect nodes typically located within a radius of hundreds of meters. It can be used, for example, within an office or a school.
• Metropolitan Area Networks. A MAN (Metropolitan Area Network) is a network that can be either public or private, used to connect nodes typically located within a radius of a few kilometers. It can be used, for example, for a university campus or a city network.
• Geographic Networks. A WAN (Wide Area Network) is a public network, typically managed by a telecommunications company. It is used to cover a large area, such as the territory of a nation or a continent.
• Networks of networks or internetworks. A network of networks is used to interconnect LANs and/or WANs to achieve global coverage. An example of an internetwork is the current global Internet.

Classification of networks by privacy

Another way to classify computer networks is to consider the privacy of the information shared through the network itself. According to this criterion, we can mention:

• Internet. The information contained in the global Internet is accessible to anyone. The only way to protect information is to At the directory or application level, for example, through restricted parts of a website. In these cases, access is protected by username and password.
• Intranet. The information contained in an intranet is accessible only to users belonging to that specific intranet. An intranet therefore has a typically corporate dimension and is used to allow only members easy access to the information of that particular company or institution.
• Extranet. This is an extension of the intranet, in which information is accessible not only to intranet users but also to specific authorized external users. An extranet is typically used by a company to securely share internal information with other organizations with which it has relationships, such as partners, suppliers, or customers.