Editing Wide area network

{{short description|Computer network that connects devices across a large distance and area}}
{{Use British English|date=September 2020}}

[[File:LAN WAN scheme.svg|thumb|A [[local area network]] (LAN) with connection to a wide area network (WAN)]]
{{Area networks}}

A '''wide area network''' ('''WAN''') is a [[telecommunications network]] that extends over a large geographic area. Wide area networks are often established with [[Leased line|leased telecommunication circuits]].<ref>{{Cite news|url=https://www.lifewire.com/wide-area-network-816383 |first1=Bradley |last1=Mitchell |title=What Is a Wide Area Network (WAN)? |work=Lifewire|access-date=2017-04-21|archive-date=2018-06-12|archive-url=https://web.archive.org/web/20180612143457/https://www.lifewire.com/wide-area-network-816383|url-status=live}}</ref>

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. The [[Internet]] may be considered a WAN.<ref>{{cite book|last1=Groth|first1=David |last2=Skandler |first2=Toby |title=Network+ Study Guide, Fourth Edition |year=2005 |publisher=Sybex, Inc |isbn=0-7821-4406-3}}</ref> Many WANs are, however, built for one particular organization and are private. WANs can be separated from [[local area network]]s (LANs) in that the latter refers to physically proximal networks.

==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]].

==Private networks==
Of the approximately four billion addresses defined in IPv4, about 18 million addresses in three ranges are reserved for use in [[private network]]s. 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 require [[network address translation]] at a routing gateway for this purpose.
<section begin=IPv4-private-networks/><!-- This table is transcluded to other pages, such as [[Blackhole server]]. (see: [[Wikipedia:transclusion]]) -->
:{| class="wikitable"
|+ Reserved private IPv4 network ranges<ref name=rfc1918>{{cite IETF|rfc=1918|bcp=5|title=Address Allocation for Private Internets|publisher=Network Working Group [[IETF]]|author1=Y. Rekhter|author2=B. Moskowitz|author3=D. Karrenberg|author4=G. J. de Groot|author5=E. Lear|date=February 1996}}</ref>
|-
!Name!![[CIDR]] block!!Address range!!Number of addresses!!''Obsolete [[classful]]'' description
|-
|24-bit block||10.0.0.0/8||10.0.0.0 – 10.255.255.255||align="right"|{{val|16777216}}||Single Class A.                         
|-
|20-bit block|||172.16.0.0/12||172.16.0.0 – 172.31.255.255||align="right"|{{val|1048576}}||Contiguous range of 16 Class B blocks.  
|-
|16-bit block||192.168.0.0/16||192.168.0.0 – 192.168.255.255||align="right"|{{val|65536}}||Contiguous range of 256 Class C blocks. 
|}<section end=IPv4-private-networks/>

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 a [[virtual private network]] (VPN) or other form of [[IP tunnel]] that [[Encapsulation (networking)|encapsulates]] packets, including their headers containing the private addresses, for transmission across the public network. Additionally, encapsulated packets may be encrypted to secure their data.

==Connection technology==
Many technologies are available for wide area network links. Examples include [[circuit-switched]] telephone lines, [[radio wave]] transmission, and [[optical fiber]]. New developments have successively increased transmission rates. In {{circa|1960}}, a {{val|110|ul=bit/s}} line was normal on the edge of the WAN, while core links of 56 or 64&nbsp;kbit/s were considered fast. Today, households are connected to the Internet with [[dial-up]], [[asymmetric digital subscriber line]] (ADSL), [[Cable Internet access|cable]], [[WiMAX]], [[cellular network]] or [[Fiber-optic communication|fiber]]. The speeds that people can currently use range from 28.8&nbsp;kbit/s through a 28K [[modem]] over a telephone connection to speeds as high as 100&nbsp;Gbit/s using [[100 Gigabit Ethernet]].

The following communication and networking technologies have been used to implement WANs.
{{div col|colwidth=20em}}
* [[Asynchronous Transfer Mode]]
* [[Cable modem]]
* [[Cellular network]]s<ref>{{cite web | url=https://www.ciscopress.com/articles/article.asp?p=2832405&seqNum=5 | title=Selecting a WAN Technology (1.2) > WAN Concepts &#124; Cisco Press }}</ref>
* [[Dial-up internet]]
* [[Digital subscriber line]]
* [[Fiber-optic communication]]
* [[Frame Relay]]
* [[ISDN]]
* [[Leased line]]
* [[Software-defined networking#SD-WAN|SD-WAN]]
* [[Synchronous optical networking]]
* [[Very small aperture terminal]] (VSAT)<ref>{{cite web | url=https://www.ciscopress.com/articles/article.asp?p=2832405&seqNum=5 | title=Selecting a WAN Technology (1.2) > WAN Concepts &#124; Cisco Press }}</ref>
*[[Wi-Fi]]<ref>{{cite web | url=https://www.ciscopress.com/articles/article.asp?p=2832405&seqNum=5 | title=Selecting a WAN Technology (1.2) > WAN Concepts &#124; Cisco Press }}</ref>
*[[WiMAX]]<ref>{{cite web | url=https://www.ciscopress.com/articles/article.asp?p=2832405&seqNum=5 | title=Selecting a WAN Technology (1.2) > WAN Concepts &#124; Cisco Press }}</ref>
* [[X.25]]
{{div col end}}

AT&T conducted trials in 2017 for business use of [[400-gigabit Ethernet]].<ref>{{cite web |url=http://about.att.com/story/att_completes_industry_leading_ethernet_testing.html |title=AT&T Completes Industry-Leading 400 Gb Ethernet Testing, Establishing A Future Network Blueprint for Service Providers and Businesses |website=www.att.com |date=September 8, 2017 |access-date=August 20, 2018 |archive-date=January 5, 2022 |archive-url=https://web.archive.org/web/20220105095752/https://about.att.com/story/att_completes_industry_leading_ethernet_testing.html |url-status=live }}</ref> Researchers Robert Maher, Alex Alvarado, Domaniç Lavery, and Polina Bayvel of [[University College London]] were able to increase networking speeds to 1.125 terabits per second.<ref>{{cite journal|title=Increasing the information rates of optical communications via coded modulation: a study of transceiver performance |first1=Robert |last1=Maher |first2=Alex |last2=Alvarado |first3=Domaniç |last3=Lavery |first4=Polina|last4=Bayvel|date=11 February 2016 |journal=Scientific Reports|volume=6|issue=1|pages=21278 |doi=10.1038/srep21278|pmid=26864633|pmc=4750034|bibcode=2016NatSR...621278M }}</ref> Christos Santis, graduate student Scott Steger, Amnon Yariv, Martin and Eileen Summerfield developed a new laser that potentially quadruples transfer speeds with fiber optics.<ref>{{cite web|url=https://www.caltech.edu/news/new-laser-faster-internet-42090|title=A New Laser for a Faster Internet - Caltech|date=19 February 2014 |publisher=Cal Tech|access-date=2017-02-05|archive-date=2017-05-11|archive-url=https://web.archive.org/web/20170511203500/http://www.caltech.edu/news/new-laser-faster-internet-42090|url-status=live}}</ref>

==See also==
*[[Cell relay]]
*[[Internet area network]] (IAN)
*[[Label switching]]
*[[Low-power wide-area network]] (LPWAN)
*[[Wide area application services]]
*[[Wireless WAN]]

==References==
{{Reflist}}

== External links ==
*[https://web.archive.org/web/20110722135521/http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook Cisco - Introduction to WAN Technologies]
*{{Citation |url=http://searchenterprisewan.techtarget.com/definition/WAN |title=What is WAN (wide area network)? - Definition from WhatIs.com |website=SearchEnterpriseWAN |access-date=2017-04-21 |language=en-US |archive-url=https://web.archive.org/web/20170429083554/http://searchenterprisewan.techtarget.com/definition/WAN |archive-date=2017-04-29 |url-status=dead}}
*[https://www.ibm.com/services/network/sd-wan  What is a software-defined wide area network?]

{{Telecommunications}}

{{Authority control}}

{{DEFAULTSORT:Wide Area Network}}
[[Category:Wide area networks]]
[[Category:Telecommunications]]
[[Category:Data transmission]]