What is a network? De­f­i­n­i­tion, ex­pla­na­tion, and examples

When you buy a new computer, the first thing you’ll probably try to do is connect to the Internet. To do this, you establish a con­nec­tion to your router, which receives the data from the Internet and then forwards it to the computer.

Of course that’s not all: Next, you could also connect your printer, smart­phone or TV to the router so that these devices are also connected to the Internet. Now you have connected different devices to each other via a central access point and created your own network.

But what exactly does that mean?

In in­for­ma­tion tech­nol­o­gy, a network is defined as the con­nec­tion of at least two computer systems, either by a cable or a wireless con­nec­tion. The simplest network is a com­bi­na­tion of two computers connected by a cable. This type of network is called a peer-to-peer network. There is no hierarchy in this network; both par­tic­i­pants have equal priv­i­leges. Each computer has access to the data of the other device and can share resources such as disk space, ap­pli­ca­tions or pe­riph­er­al devices (printers, etc.).

Today’s networks tend to be a bit more complex and don’t just consist of two computers. Systems with more than ten par­tic­i­pants usually use client-server networks. In these networks, a central computer (server) provides resources to the other par­tic­i­pants in the network (clients).

The Wireless LAN (Wireless Local Area Network, i.e. the Wi-Fi network) in your home is a good example of a small client-server network. The various devices in your home are wire­less­ly connected to the router, which acts as a central node (server) for the household. The router itself is connected to a much larger network: the Internet.

Since the devices are connected to the router as clients, they are part of the network and can use the same resource as the server, namely the Internet. The devices can also com­mu­ni­cate with each other without having to establish a direct con­nec­tion to each device. For example, you can send a print job to a Wi-Fi-enabled printer without first con­nect­ing the printer to the computer using a cable.

Before the advent of modern networks, com­mu­ni­ca­tion between different computers and devices was very com­pli­cat­ed. Computers were connected using a LAN cable. Me­chan­i­cal switches were used so that pe­riph­er­al devices could also be shared. Due to physical lim­i­ta­tions (cable length), the devices and computers always had to be very close to each other.

The main task of a network is to provide par­tic­i­pants with a single platform for ex­chang­ing data and sharing resources. This task is so important that many aspects of everyday life and the modern world would be unimag­in­able without networks.

Here’s a real-life example: In a typical office, every work­sta­tion has its own computer. Without a network of computers, it would be very difficult for a team to work on a project since there would be no common place to share or store digital documents and in­for­ma­tion, and team members would not be able to share certain ap­pli­ca­tions.

In addition, many offices only have one printer or a few printers that are shared by everyone. Without a network, the IT de­part­ment would have to connect every single computer to the printer, which is difficult to implement from a technical stand­point. A network elegantly solves this problem because all computers are connected to the printer via one central node.

The main ad­van­tages of networks are:

• Shared use of data
• Shared use of resources
• Central control of programs and data
• Central storage and backup of data
• Shared pro­cess­ing power and storage capacity
• Easy man­age­ment of au­tho­riza­tions and re­spon­si­bil­i­ties

In larger networks, such as corporate networks, the server is usually a central computer. This computer is used ex­clu­sive­ly for running special server software and services, not regular ap­pli­ca­tions and programs. The server must operate con­tin­u­ous­ly, whereas the other computers (clients) can be switched off.

The server and the client com­mu­ni­cate as follows in this server-based network: The client first sends a request to the server. The server evaluates the request and then transmits the response. In this model, the client always connects to the server, never the other way around.

Network protocols ensure smooth com­mu­ni­ca­tion between the different com­po­nents in a network. They control data exchange and determine how com­mu­ni­ca­tion is es­tab­lished and ter­mi­nat­ed as well as which data is trans­mit­ted. There are usually multiple network protocols that each perform a specific subtask and are hi­er­ar­chi­cal­ly organized into layers.

In addition, it is necessary to ensure that the trans­mit­ter and receiver can be correctly iden­ti­fied. Network addresses are used for this purpose. In computer networks, each computer typically has an IP address, similar to a telephone number, that uniquely iden­ti­fies the computer. This internal IP address is used only for com­mu­ni­ca­tion between the par­tic­i­pants in the local network. For com­mu­ni­ca­tion on the Internet, external IP addresses are used that are au­to­mat­i­cal­ly assigned by the Internet provider.

A dis­tinc­tion is also made between IPv4 and IPv6 addresses. IPv4 addresses used to be standard, but only a total of around 4.3 billion of these addresses could be assigned before they were exhausted. Due to the massive expansion of the Internet, ad­di­tion­al IP addresses were urgently needed. Therefore, the new IPv6 standard was developed, allowing up to 3.4 x 10³⁸ (340 sex­til­lion) addresses. This should be suf­fi­cient for the future.

You can find detailed in­for­ma­tion on the IP protocol and its important role in computer networks in our article “What is the Internet Protocol ?”.

Networks are usually divided into different network types according to trans­mis­sion type and range, that is, depending on how or how far the data is trans­mit­ted.

Networks are clas­si­fied by trans­mis­sion type as either wireless or wired. Examples of wireless networks include Wi-Fi networks based on the IEEE 802.11 standard, or the LTE networks used for mobile devices and smart­phones. Wired networks such as DSL are also known as broadband Internet.

Networks are typically clas­si­fied by range as follows:

• Personal Area Network (PAN): A PAN is used for in­ter­con­nect­ing devices within a short range of ap­prox­i­mate­ly 10 meters. Examples include Bluetooth tech­nol­o­gy or Apple’s Airdrop ad hoc Wi-Fi service.
• Local Area Network (LAN): Local area networks are among the most wide­spread networks and are used in house­holds or small and medium-sized companies.
• Met­ro­pol­i­tan Area Network (MAN): These types of networks cover cities or single ge­o­graph­ic regions.
• Wide Area Network (WAN): The na­tion­wide broadband or cellular network in the US is an example of a Wide Area Network.
• GAN (Global Area Network): The best known example of a global network is the Internet.

Note that there is some overlap between the different network types: As a Wi-Fi user, you are si­mul­ta­ne­ous­ly part of a WAN and a GAN when you’re connected to the Internet.