Design Options
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 Layer 1/2 (such as the forms of Ethernet or Wifi) are often geared towards physically localised networks, and thus cannot transmit data over tens, hundreds or even thousands of miles or kilometres.
WANs necessarily do not just connect physically disparate LANs. A CAN, for example, may have a localised 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.
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, MPLS, 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.
Academic research into wide area networks can be broken down into three areas: mathematical models, network emulation and network simulation.
Performance improvements are sometimes delivered via wide area file services or WAN optimization.
Read more about this topic: Wide Area Network
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