<P> Related terms for other types of networks are personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area respectively . </P> <P> The textbook definition of a WAN is a computer network spanning regions, countries, or even the world . However, in terms of the application of computer networking protocols and concepts, it may be best to view WANs as computer networking technologies used to transmit data over long distances, and between different LANs, MANs and other localised computer networking architectures . This distinction stems from the fact that common LAN technologies operating at lower layers of the OSI model (such as the forms of Ethernet or Wi - Fi) are often designed for physically proximal networks, and thus cannot transmit data over tens, hundreds or even thousands of miles or kilometres . </P> <P> WANs do not just necessarily connect physically disparate LANs . A CAN, for example, may have a localized backbone of a WAN technology, which connects different LANs within a campus . This could be to facilitate higher bandwidth applications or provide better functionality for users in the CAN . </P> <P> WANs are used to connect LANs and other types of networks together so that users and computers in one location can communicate with users and computers in other locations . Many WANs are built for one particular organization and are private . Others, built by Internet service providers, provide connections from an organization's LAN to the Internet . WANs are often built using leased lines . At each end of the leased line, a router connects the LAN on one side with a second router within the LAN on the other . Leased lines can be very expensive . Instead of using leased lines, WANs can also be built using less costly circuit switching or packet switching methods . Network protocols including TCP / IP deliver transport and addressing functions . Protocols including Packet over SONET / SDH, Multiprotocol Label Switching (MPLS), Asynchronous Transfer Mode (ATM) and Frame Relay are often used by service providers to deliver the links that are used in WANs . X. 25 was an important early WAN protocol, and is often considered to be the "grandfather" of Frame Relay as many of the underlying protocols and functions of X. 25 are still in use today (with upgrades) by Frame Relay . </P>

Network categories is the largest in term of its size