Editing Internet access (section)

====Digital subscriber line (DSL, ADSL, SDSL, and VDSL)====
[[Digital subscriber line]] (DSL) service provides a connection to the Internet through the telephone network. Unlike dial-up, DSL can operate using a single phone line without preventing normal use of the telephone line for voice phone calls. DSL uses the high frequencies, while the low (audible) frequencies of the line are left free for [[Plain old telephone service|regular telephone]] communication.<ref name="howstuffworks" /> These frequency bands are subsequently separated by filters installed at the customer's premises.

DSL originally stood for "digital subscriber loop". In telecommunications marketing, the term digital subscriber line is widely understood to mean [[asymmetric digital subscriber line]] (ADSL), the most commonly installed variety of DSL. The data throughput of consumer DSL services typically ranges from 256&nbsp;kbit/s to 20&nbsp;Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (i.e., in the direction to the service provider) is lower than that in the downstream direction (i.e. to the customer), hence the designation of asymmetric.<ref>[http://whirlpool.net.au/wiki/?tag=ADSL_Theory "ADSL Theory"] {{webarchive|url=https://web.archive.org/web/20100724040222/http://whirlpool.net.au/wiki/?tag=ADSL_Theory |date=2010-07-24 }}, Australian broadband news and information, Whirlpool, accessed 3 May 2012</ref> With a [[symmetric digital subscriber line]] (SDSL), the downstream and upstream data rates are equal.<ref>[http://docwiki.cisco.com/wiki/Digital_Subscriber_Line#SDSL "SDSL"] {{webarchive|url=https://web.archive.org/web/20120418172858/http://docwiki.cisco.com/wiki/Digital_Subscriber_Line |date=2012-04-18 }}, ''Internetworking Technology Handbook'', Cisco DocWiki, 17 December 2009, accessed 3 May 2012</ref>

[[Very-high-bit-rate digital subscriber line]] (VDSL or VHDSL, ITU G.993.1)<ref>{{cite web|url=http://www.kpn.com/artikel.htm?contentid=2895 |publisher=[[KPN]] |title=KPN starts VDSL trials |url-status=dead |archive-url=https://web.archive.org/web/20080504192232/http://www.kpn.com/Artikel.htm?contentid=2895 |archive-date=2008-05-04 }}</ref> is a digital subscriber line (DSL) standard approved in 2001 that provides data rates up to 52&nbsp;Mbit/s downstream and 16&nbsp;Mbit/s upstream over copper wires<ref>{{cite web |url=http://computer.howstuffworks.com/vdsl2.htm |publisher=[[HowStuffWorks]] |title=VDSL Speed |url-status=live |archive-url=https://web.archive.org/web/20100312075145/http://computer.howstuffworks.com/vdsl2.htm |archive-date=2010-03-12 |date=2001-05-21 }}</ref> and up to 85&nbsp;Mbit/s down- and upstream on coaxial cable.<ref>{{cite web |url=http://www.etherwan.com/Product/ViewProduct.asp?View=64 |archive-url=https://web.archive.org/web/20110710203152/http://www.etherwan.com/Product/ViewProduct.asp?View=64 |url-status=dead |archive-date=2011-07-10 |publisher=EtherWAN |title=Industrial VDSL Ethernet Extender Over Coaxial Cable, ED3331 }}</ref> VDSL is capable of supporting applications such as high-definition television, as well as telephone services ([[voice over IP]]) and general Internet access, over a single physical connection.

[[VDSL2]] ([[ITU-T]] [[G.993.2]]) is a second-generation version and an enhancement of VDSL.<ref name="press">{{Cite news |title= New ITU Standard Delivers 10x ADSL Speeds: Vendors applaud landmark agreement on VDSL2 |date= 27 May 2005 |work= News release |publisher= International Telecommunication Union |url= http://www.itu.int/newsroom/press_releases/2005/06.html |access-date= 22 September 2011 |url-status= live |archive-url= https://web.archive.org/web/20160903203113/http://www.itu.int/newsroom/press_releases/2005/06.html |archive-date= 3 September 2016 }}</ref> Approved in February 2006, it is able to provide data rates exceeding 100&nbsp;Mbit/s simultaneously in both the upstream and downstream directions. However, the maximum data rate is achieved at a range of about 300 meters and performance degrades as distance and loop [[attenuation]] increases.