What is a network?

A network is a network of multiple independent computer systems that are connected to each other in such a way that data exchange is possible. In addition to a physical connection, there must also be a logical connection between the systems in the network. The latter is established by special network protocols, such as TCP (Transmission Control Protocol). Even two computers that are connected to each other can be considered a network. Networks are set up to send data from one system to another or to share common resources, such as servers, databases and printers. Depending on the size and scope of the computer network, a distinction can be made between different network dimensions. The most important types of networks are:

• Personal Area Networks (PAN)

• Local Area Networks (LAN)

• Metropolitan Area Networks (MAN)

• Wide Area Networks (WAN)

• Global Area Networks (GAN)

The physical connection on which these types of networks are based can be established via a cable or via wireless technology. Physical communication networks often form the basis for multiple logical communication networks, so-called Virtual Private Networks (VPN). Although these use a common physical transmission medium, such as a fibre optic cable, for data transmission, they are nevertheless logically assigned to different virtual networks using tunnelling software.

All types of networks have been developed for specific areas of application and are based on their own technologies and standards. They therefore each have their own advantages and limitations.

 

Personal Area Network (PAN)

To enable data exchange, modern devices such as smartphones, tablets, laptops and desktop computers can be integrated ad hoc into a network. This can be done via a cable or in the form of a Personal Area Network (PAN). Common transmission techniques are USB and FireWire. The wireless variant Wireless Personal Area Network (WPAN) is based on techniques such as Bluetooth, Wireless USB, Insteon, IrDA, ZigBee and Z-Wave. A wireless Personal Area Network that is established via Bluetooth is called Piconet. PANs and WPANs generally have a range of only a few metres. This makes them unsuitable for connecting devices that are located in different rooms or even buildings.

In addition to establishing communication between individual devices, a Personal Area Network can be used to connect to other, often larger networks. This is called an uplink. Due to the limited range and relatively low data transmission speed, PANs are mainly used for connecting peripherals for hobbies and entertainment. Typical examples are wireless headphones, game consoles and digital cameras. Within the Internet of Things (IoT), WPANs are responsible for the communication of control and monitoring applications with low data rates. Protocols such as Insteon, Z-Wave and ZigBee are specifically designed for smart homes and home automation.

 

Local Area Network (LAN)

When multiple computers are connected to each other via a network, this is usually in the form of a Local Area Network (LAN). These networks can consist of two computers within a household, but also of thousands of devices within a company. Networks in public institutions, such as government buildings, schools and universities, are also connected via LAN. A commonly used standard for wired Local Area Networks is Ethernet. Less well-known and often outdated are network technologies such as ARCNET, FDDI and Token Ring. Data transmission takes place electronically via copper cables or via fibre optic cables.

When more than two computers are connected to each other in a LAN, additional network components are required, such as hubs, bridges and switches. These function as coupling elements and distribution nodes. The LAN network type was developed to enable the rapid transmission of large amounts of data. Depending on the structure of the network and the transmission medium used, a data throughput of 10 to 1,000 Mbit/s is common. LANs enable a convenient exchange of information between the various devices that are connected to each other in the network. In companies, it is common to share file servers, network printers and applications with multiple work computers via LAN.

When a Local Area Network has wireless connections, it is called a Wireless Local Area Network (WLAN). The technical basis of the WLAN standard is defined by the IEEE 802.11 family of standards. Wireless Local Area Networks offer the possibility of easily integrating devices into a home or business network and are compatible with wired Ethernet LANs. However, the data throughput is often lower than with an Ethernet connection.

The range of a LAN depends on the standard and the transmission medium, but can be improved with signal repeaters. With Gigabit Ethernet via fibre optics, a signal range of several kilometres is possible. However, Local Area Networks rarely extend beyond a single building complex. Multiple LANs in close proximity to each other can be connected to a higher-level Metropolitan Area Network (MAN) or Wide Area Network (WAN).

 

Metropolitan Area Network (MAN)

A Metropolitan Area Network (MAN) is a broadband telecommunications network that connects multiple LANs in close proximity to each other. Typically, these are individual locations of a company that are connected to a MAN via leased lines. Powerful routers and high-performance fiber-based connections are used, which enable significantly higher data throughput than the Internet. The transmission speed between two remote nodes is comparable to communication within a Local Area Network.

The infrastructure for MANs is provided by international network operators. Cities wired as Metropolitan Area Networks can be integrated nationally into Wide Area Networks (WAN) and internationally into Global Area Networks (GAN).

With Metro Ethernet, a special transmission technology is available for MANs, with which powerful Metro Ethernet Networks (MEN) can be built based on Carrier Ethernet (CE 1.0) or Carrier Ethernet 2.0 (CE 2.0).

A standard for larger regional wireless networks, so-called Wireless Metropolitan Area Networks (WMAN), has been developed with IEEE 802.16. With this technology, known as WiMAX (Worldwide Interoperability for Microwave Access), WLAN hotspots can be set up. These are multiple WLAN access points that work together at different locations. The current transmission standard DSL is technically only available in places where copper cables have been laid.

 

Wide Area Network (WAN)

While Metropolitan Area Networks connect locations that are close together, Wide Area Networks (WANs) span large areas, such as countries or continents. The number of local networks or individual computers that can be connected to each other via a WAN is in principle unlimited.

While LANs and MANs can be implemented using Ethernet due to the geographical proximity of the computers or networks, WANs use technologies such as IP/MPLS (Multiprotocol Label Switching), PDH (Plesiochronous Digital Hierarchy), SDH (Synchronous Digital Hierarchy), SONET (Synchronous Optical Network), ATM (Asynchronous Transfer Mode) and very occasionally the outdated X.25.

Wide Area Networks are usually owned by a specific organization or company and are privately operated or leased. In addition, Internet service providers use WANs to provide local business networks and consumers with an Internet connection.

 

Global Area Network (GAN)

A worldwide network, such as the Internet, is called a Global Area Network (GAN). But the Internet is not the only computer network of its kind. Internationally operating companies maintain shielded networks that include multiple WANs and connect corporate computers all over the world. GANs use the fiber optic infrastructure of Wide Area Networks and combine it with international cables under the sea or satellite transmissions.

 

Virtual Private Network (VPN)

A Virtual Private Network (VPN) is a virtual communications network that uses the infrastructure of a physical network to logically connect computer systems. This can be any of the types of networks discussed above, but the Internet is the most common transport medium. After all, the World Wide Web connects almost all computers in the world and is available free of charge (unlike privately managed MANs or WANs). Data transfer takes place in a virtual tunnel that is set up between a VPN client and a VPN server.

When the public network is used as a transport medium, Virtual Private Networks are usually encrypted to ensure the security of the data. VPNs are used to connect LANs via the Internet, or to enable remote access to a network or a specific computer.

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