What is a LAN (Local Area Network)?

Nowadays, virtually all LANs are realized via Ethernet. In the past, LANs were also implemented using the following technologies which nowadays hardly play a role anymore:

• Token Ring
• DECNET
• FDDI (still used in some cases to connect Ethernet and Token Ring technology)
• ARCNET (outdated but still used in industrial automation)

Ethernet achieves data transmission rates of up to several hundred Gbits/s. The technology uses either twisted pair cable or – the newer method – fiber optic cable. While conventional copper cables can only bridge up to 100 meters, fiber optic cables can stretch over several miles. In order to ensure that the data actually arrives via the cable connections and that data packets don’t block each other, technology such as CSMA/CD is used. In the case of a WLAN in which data packets are transmitted wirelessly, CSMA/CA is utilized.

An Ethernet LAN can be divided into multiple virtual LANs (VLANs) or physical LANs. The virtual structure enables administrators to partition networks without needing to implement major infrastructure changes.

Switches and routers are used to organize Local Area Networks. The hardware acts as an interface and governs the connections between the individual network participants, ensuring the data packets reach their destination. Also, when data is transmitted from a LAN to the internet or information is to be accessed from other networks or data centers, the connection occurs via a router. By contrast, repeaters and hubs which previously performed similar tasks are scarcely used in modern LANs.

Network cables, network sockets, and network patches are also used as physical components when setting up a LAN. They connect the individual end devices and servers with each other and offer network administrators and home admins the ability to neatly install the network in the office or at home.