Businesses, as well as schools and government entities, use wide area networks to relay data to staff, students, clients, buyers and suppliers from various locations around the world. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. TheInternet may be considered a WAN.[2] Many WANs are, however, built for one particular organization and are private. WANs can be separated fromlocal area networks (LANs) in that the latter refers to physically proximal networks.
The textbook definition of a WAN is a computer network spanning regions, countries, or even the world.[3][4] However, in terms of the application ofcommunication protocols and concepts, it may be best to view WANs as computer networking technologies used to transmit data over long distances, and between different networks. This distinction stems from the fact that commonlocal area network (LAN) technologies operating at lower layers of theOSI model (such as the forms ofEthernet orWi-Fi) are often designed for physically proximal networks, and thus cannot transmit data over tens, hundreds, or even thousands of miles or kilometres.
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 byInternet service providers, provide connections from an organization's LAN to the Internet.
Of the approximately four billion addresses defined in IPv4, about 18 million addresses in three ranges are reserved for use inprivate networks. Packets addressed in these ranges are not routable on the public Internet; they are ignored by all public routers. Therefore, private hosts cannot directly communicate with public networks, but requirenetwork address translation at a routing gateway for this purpose.
Since two private networks, e.g., two branch offices, cannot directly communicate via the public Internet, the two networks must be bridged across the Internet via avirtual private network (VPN) or other form ofIP tunnel thatencapsulates packets, including their headers containing the private addresses, for transmission across the public network. Additionally, encapsulated packets may be encrypted to secure their data.
Many technologies are available for wide area network links. Examples includecircuit-switched telephone lines,radio wave transmission, andoptical fiber. New developments have successively increased transmission rates. Inc. 1960, a110 bit/s line was normal on the edge of the WAN, while core links of 56 or 64 kbit/s were considered fast. Today, households are connected to the Internet withdial-up,asymmetric digital subscriber line (ADSL),cable,WiMAX,cellular network orfiber. The speeds that people can currently use range from 28.8 kbit/s through a 28Kmodem over a telephone connection to speeds as high as 100 Gbit/s using100 Gigabit Ethernet.
The following communication and networking technologies have been used to implement WANs.
AT&T conducted trials in 2017 for business use of400-gigabit Ethernet.[8] Researchers Robert Maher, Alex Alvarado, Domaniç Lavery, and Polina Bayvel ofUniversity College London were able to increase networking speeds to 1.125 terabits per second.[9] Christos Santis, graduate student Scott Steger, Amnon Yariv, Martin and Eileen Summerfield developed a new laser that potentially quadruples transfer speeds with fiber optics.[10]
