Local area network

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of data and sharing network devices, such as printers.

The LAN contrasts the wide area network (WAN), which not only covers a larger geographic distance, but also generally involves leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business and personal computers.

Ethernet and Wi-Fi are the two most common technologies used for local area networks; historical network technologies include ARCNET, Token Ring, and LocalTalk.

Most wired network infrastructures utilize Category 5 or Category 6 twisted pair cabling with RJ45 compatible terminations. This medium provides physical connectivity between the Ethernet interfaces present on a large number of IP-aware devices. Depending on the grade of cable and quality of installation, speeds of up to 10 Mbit/s, 100 Mbit/s, 1 Gbit/s, or 10 Gbit/s are supported.

In a wireless LAN, users have unrestricted movement within the coverage area. Wireless networks have become popular in residences and small businesses because of their ease of installation, convenience, and flexibility. Most wireless LANs consist of devices containing wireless radio technology that conforms to 802.11 standards as certified by the IEEE. Most wireless-capable residential devices operate at both the 2.4 GHz and 5 GHz frequencies and fall within the 802.11n or 802.11ac standards. Some older home networking devices operate exclusively at a frequency of 2.4 GHz under 802.11b and 802.11g, or 5 GHz under 802.11a. Some newer devices operate at the aforementioned frequencies in addition to 6 GHz under Wi-Fi 6E. Wi-Fi is a marketing and compliance certification for IEEE 802.11 technologies. The Wi-Fi Alliance has tested compliant products, and certifies them for interoperability. The technology may be integrated into smartphones, tablet computers and laptops. Guests are often offered Internet access via a hotspot service.

Simple LANs in office or school buildings generally consist of cabling and one or more network switches; a switch is used to allow devices on a LAN to talk to one another via Ethernet. A switch can be connected to a router, cable modem, or ADSL modem for Internet access. LANs at residential homes usually tend to have a single router and often may include a wireless repeater. A LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection. A wireless access point is required for connecting wireless devices to a network; when a router includes this device, it is referred to as a wireless router.

Advanced LANs are characterized by their use of redundant links with switches using the Spanning Tree Protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and their ability to segregate traffic with VLANs. A network bridge binds two different LANs or LAN segments to each other, often in order to grant a wired-only device access to a wireless network medium.

Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star. The star topology is the most common in contemporary times. Wireless LAN (WLAN) also has its topologies: independent basic service set (IBSS, an ad-hoc network) where each node connects directly to each other (this is also standardized as Wi-Fi Direct), or basic service set (BSS, an infrastructure network that uses an wireless access point).