Editing Wide area network (section)

==Design options==
The textbook definition of a WAN is a computer network spanning regions, countries, or even the world.<ref>{{Cite book|title=Data Communications and Networking|last=Forouzan|first=Behrouz|publisher=McGraw-Hill|isbn=9780073376226|pages=14|date=2012-02-17}}</ref><ref>{{Cite journal|last1=Zhang|first1=Yan|last2=Ansari|first2=Nirwan|last3=Wu|first3=Mingquan|last4=Yu|first4=Heather|date=2011-10-13|title=On Wide Area Network Optimization|url=https://ieeexplore.ieee.org/document/6042388|journal=IEEE Communications Surveys & Tutorials|volume=14|issue=4|pages=1090–1113|doi=10.1109/SURV.2011.092311.00071|s2cid=18060|issn=1553-877X|access-date=2022-01-29|archive-date=2022-02-08|archive-url=https://web.archive.org/web/20220208215301/http://ieeexplore.ieee.org/document/6042388/|url-status=live|citeseerx=10.1.1.459.4653}}</ref> However, in terms of the application of [[communication protocol]]s 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 common [[local area network]] (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.

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 provider]]s, provide connections from an organization's LAN to the Internet. 

WANs are often built using [[leased line]]s. At each end of the leased line, a [[Router (computing)|router]] connects the LAN on one side with a second router within the LAN on the other. Because 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 [[communications protocol|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. It is also possible to build a WAN with [[Ethernet]].<ref>{{cite book | url=https://books.google.com/books?id=qLtoBQAAQBAJ&dq=wan+technology&pg=PT173 | isbn=978-0-13-378782-5 | title=CCNA Data Center DCICN 640-911 Official Cert Guide | date=14 November 2014 | publisher=Cisco Press }}</ref>

Academic research into wide area networks can be broken down into three areas: [[mathematical model]]s, [[network emulation]], and [[network simulation]]. 

Performance improvements are sometimes delivered via [[wide area file services]] or [[WAN optimization]].