Networks & Network Security: Lecture Notes

A network belongs to one of the following categories:

Local Area Network (LAN): A network that is confined to a relatively small geographical area such as a school or an office building and occasionally a group of nearby buildings. LAN connects a relatively small number of systems within the same organization. The most common LAN protocol is Ethernet.
Metropolitan Area Network (MAN): Metropolitan Area Networks (MAN) is a network of connected systems within the same metropolitan city. A MAN is larger than a LAN but smaller than a WAN. For practical reasons, a MAN is optimized for a large geographical area, and can connect two types of networks – LAN and WAN.
Wide Area Network (WAN): connects two or more LANs which are geographically apart. For example, an organization may have two different offices in two different places or countries and they are connected together to form a WAN. WAN connections comprises of several devices including multiplexers, bridges, and routers. WAN link can be a private dedicated link or a public link. The Internet is the largest existing WAN.