Editing Internet access (section)

====Leased lines====
[[Leased line]]s are dedicated lines used primarily by ISPs, business, and other large enterprises to connect LANs and campus networks to the Internet using the existing infrastructure of the [[Public switched telephone network|public telephone network]] or other providers. Delivered using wire, [[optical fiber]], and [[radio]], leased lines are used to provide Internet access directly as well as the building blocks from which several other forms of Internet access are created.<ref name="Horak">[http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470396075.html ''Telecommunications and Data Communications Handbook''] {{webarchive|url=https://web.archive.org/web/20130308075758/http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470396075.html |date=2013-03-08 }}, Ray Horak, 2nd edition, Wiley-Interscience, 2008, 791 p., {{ISBN|0-470-39607-5}}</ref>

[[T-carrier]] technology<ref name="lightwaveonline.com">{{cite web | url=https://www.lightwaveonline.com/fttx/pon-systems/article/16649783/fiber-optics-among-carrier-ethernets-multiple-access-technologies | title=Fiber optics among Carrier Ethernet's multiple access technologies | date=July 2009 }}</ref> dates to 1957 and provides data rates that range from 56 and {{val|64|u=kbit/s}} ([[Digital Signal 0|DS0]]) to {{val|1.5|u=Mbit/s}} ([[Digital Signal 1|DS1]] or T1), to {{val|45|u=Mbit/s}} ([[Digital Signal 3|DS3]] or T3).<ref name="auto">{{cite journal | url=https://ieeexplore.ieee.org/document/774937 | doi=10.1109/6294.774937 | title=Emerging high-speed access technologies | year=1999 | last1=Cuffie | first1=D. | last2=Biesecker | first2=K. | last3=Kain | first3=C. | last4=Charleston | first4=G. | last5=Ma | first5=J. | journal=IT Professional | volume=1 | issue=2 | pages=20–28 | url-access=subscription }}</ref> A T1 line carries 24 voice or data channels (24 DS0s), so customers may use some channels for data and others for voice traffic or use all 24 channels for clear channel data. A DS3 (T3) line carries 28 DS1 (T1) channels. Fractional T1 lines are also available in multiples of a DS0 to provide data rates between 56 and {{val|1,500|u=kbit/s}}. T-carrier lines require special termination equipment such as [[Data service unit]]s<ref>{{cite book | url=https://books.google.com/books?id=VZ0vDwAAQBAJ&dq=data+service+unit+t1&pg=PA375 | title=Transmission Systems Design Handbook for Wireless Networks | isbn=978-1-58053-243-3 | last1=Lehpamer | first1=Harvey | date=2002 | publisher=Artech House }}</ref><ref>{{cite book | url=https://books.google.com/books?id=SQ2WAAAAQBAJ&dq=data+service+unit+t1&pg=PT89 | title=A Practical Guide to Advanced Networking | isbn=978-0-13-335400-3 | last1=Beasley | first1=Jeffrey S. | last2=Nilkaew | first2=Piyasat | date=5 November 2012 | publisher=Pearson Education }}</ref><ref>{{cite book | url=https://books.google.com/books?id=YSzMBQAAQBAJ&dq=data+service+unit+t1&pg=PA52 | title=Practical Network Design Techniques: A Complete Guide for WANs and LANs | isbn=978-0-203-50745-2 | last1=Held | first1=Gilbert | last2=Ravi Jagannathan | first2=S. | date=11 June 2004 | publisher=CRC Press }}</ref> that may be separate from or integrated into a router or switch and which may be purchased or leased from an ISP.<ref>{{cite book|last=Dean|first=Tamara|title=Network+ Guide to Networks|edition=5th|publisher=Course Technology, Cengage Learning|year=2009|url=http://www.cengage.com/search/productOverview.do?N=0&Ntk=P_Isbn13&Ntt=9781423902454|isbn=978-1-4239-0245-4|url-status=dead|archive-url=https://web.archive.org/web/20130420223256/http://www.cengage.com/search/productOverview.do?N=0&Ntk=P_Isbn13&Ntt=9781423902454|archive-date=2013-04-20}} pp 312–315.</ref> In Japan the equivalent standard is J1/J3. In Europe, a slightly different standard, [[E-carrier]], provides 32 user channels ({{val|64|u=kbit/s}}) on an E1 ({{val|2.0|u=Mbit/s}}) and 512 user channels or 16 E1s on an E3 ({{val|34.4|u=Mbit/s}}).

[[Synchronous Optical Networking]] (SONET, in the U.S. and Canada) and Synchronous Digital Hierarchy (SDH, in the rest of the world)<ref name="lightwaveonline.com"/> are the standard multiplexing protocols used to carry high-data-rate digital bit-streams over optical fiber using [[lasers]] or highly [[coherent light]] from [[light-emitting diodes]] (LEDs). At lower transmission rates data can also be transferred via an electrical interface. The basic unit of framing is an [[OC-3c]] (optical) or [[Synchronous optical networking#The basic unit of transmission|STS-3]]c (electrical) which carries {{val|155.520|u=Mbit/s}}. Thus an OC-3c will carry three [[Optical Carrier#OC-1|OC-1]] (51.84&nbsp;Mbit/s) payloads each of which has enough capacity to include a full DS3. Higher data rates are delivered in OC-3c multiples of four providing [[OC-12]]c ({{val|622.080|u=Mbit/s}}), [[OC-48]]c ({{val|2.488|u=Gbit/s}}), [[OC-192]]c ({{val|9.953|u=Gbit/s}}), and [[OC-768]]c ({{val|39.813|u=Gbit/s}}). The "c" at the end of the OC labels stands for "concatenated" and indicates a single data stream rather than several multiplexed data streams.<ref name="Horak" /> [[Optical transport network]] (OTN) may be used instead of SONET<ref>{{cite book | url=https://books.google.com/books?id=EisDEAAAQBAJ&dq=otn+replaces+sonet&pg=PA613 | title=Springer Handbook of Optical Networks | isbn=978-3-030-16250-4 | last1=Mukherjee | first1=Biswanath | last2=Tomkos | first2=Ioannis | last3=Tornatore | first3=Massimo | last4=Winzer | first4=Peter | last5=Zhao | first5=Yongli | date=15 October 2020 | publisher=Springer }}</ref> for higher data transmission speeds of up to {{val|400|u=Gbit/s}} per OTN channel.

The [[Gigabit Ethernet|1]], [[10 Gigabit Ethernet|10]], [[100 Gigabit Ethernet|40, and 100 Gigabit Ethernet]] [[IEEE 802.3|IEEE standards (802.3)]] allow digital data to be delivered over copper wiring at distances to 100&nbsp;m and over optical fiber at distances to {{val|40|u=km}}.<ref>[http://www.ieee802.org/3/ "IEEE 802.3 Ethernet Working Group"] {{webarchive|url=https://web.archive.org/web/20141012182235/http://www.ieee802.org/3/ |date=2014-10-12 }}, web page, IEEE 802 LAN/MAN Standards Committee, accessed 8 May 2012</ref>