Local Area Network
The term local area network (LAN) is commonly used to describe a network of devices in a limited area (a house, office, building…). This type of network is usually capable of achieving high data transfer rate (up to 10 Gbps!) at low cost. Examples of this type of network are a small office network inside a single building or your home network.
A typical SOHO (small office/home office) LAN consist of PCs, printers, switches, routers, and cabling that connects all these devices together. The following figure shows a typical LAN:
In the picture above we have two computers that are connected to a switch. The switch is then connected to a router that provides the LAN with access to the Internet.
Some of the most popular LAN technologies are Ethernet, Token Ring and FDDI. Most LAN networks use TCP/IP to communicate. Twisted-pair cabling is usually used in a LAN.
Ethernet is by far the most popular wired LAN technology. It defines wiring, signaling, connectors, frame formats, protocol rules, etc. Most modern LANs also support the wireless LAN (WLAN) technology, defined by the IEEE 802.11 standards. WLANs use radio waves instead of wires or cables for links between devices.NOTE
The term metropolitan area network is used to describe a network in a single metropolitan area, hence the name. This type of network is usually bigger than a LAN and smaller than a WAN. An example of this type of network would be a network that connects two company offices inside the same city.
Wide Area Network
The term wide area network is used to describe a network that spans multiple geographic locations. Consider an example. A company has two offices, one in London and one in Berlin. Both offices have a LAN. If the company connects these two LANs together using WAN technology, a WAN is created.
The key difference between LANs and WANs is that the company usually doesn’t own WAN infrastructure. A company usually leases WAN services from a service provider. A WAN spanning multiple cities could look something like this:
