Editing Cable modem (section)

===DOCSIS===
{{main|DOCSIS}}
In the late 1990s, a consortium of US [[Multiple system operator|cable operators]], known as "MCNS" formed to quickly develop an open and interoperable cable modem specification. The group essentially combined technologies from the two dominant proprietary systems at the time, taking the [[physical layer]] from the [[Motorola]] [[#CDLP|CDLP]] system and the [[MAC layer]] from the LANcity system. When the initial specification had been drafted, the MCNS consortium handed over control of it to [[CableLabs]] which maintained the specification, promoted it in various standards organizations (notably [[SCTE]] and [[ITU]]), developed a certification testing program for cable modem equipment, and has since drafted multiple extensions to the original specification.

While deployed [[DOCSIS|DOCSIS RFI 1.0]] equipment generally only supported [[best-effort service]], the DOCSIS RFI 1.0 Interim-01 document discussed [[quality of service]] (QoS) extensions and mechanisms using [[IntServ]], [[Resource Reservation Protocol|RSVP]], [[Real-time Transport Protocol|RTP]], and Synchronous Transfer Mode (STM) [[telephony]] (as opposed to [[Asynchronous Transfer Mode|ATM]]).<ref name="DOCSIS RFI 1.0-I01"/> [[DOCSIS|DOCSIS RFI 1.1]]<ref name="DOCSIS RFI 1.1-I01">[https://web.archive.org/web/20200729172439/https://www.cablelabs.com/specifications/SP-RFIv1.1-I01-990311.pdf DOCSIS RFI 1.1-I01 (March 11, 1999)] (See section 8 and Appendix M.)</ref> later added more robust and standardized QoS mechanisms to DOCSIS. [[DOCSIS|DOCSIS 2.0]] added support for [[Synchronous Code Division Multiple Access|S-CDMA]] [[PHY]], while DOCSIS 3.0 added [[IPv6]] support and [[channel bonding]] to allow a single cable modem to use concurrently more than one upstream channel and more than one downstream channel in parallel.

Virtually all cable modems operating in the field today are compliant with one of the DOCSIS versions. Because of the differences in the European [[PAL]] and US's [[NTSC]] systems two main versions of DOCSIS exist, DOCSIS and EuroDOCSIS. The main differences are found in the width of RF-channels: 6&nbsp;MHz for the US and 8&nbsp;MHz for Europe. A third variant of DOCSIS was developed in [[Japan]] and has seen limited deployment in that country.

Although interoperability "was the whole point of the DOCSIS project,"<ref>{{cite web|url=http://stuff.mit.edu/afs/sipb.mit.edu/contrib/doc/DOCSIS/overview/certification/Certification_Overview.pdf |title=DOCSIS Modem Interoperability and Certification Overview |website=Stuff.mit.edu |access-date=2016-08-03}}</ref> most cable operators only approve a very restricted list of cable modems on their network,<ref>{{cite web |url=http://teksavvy.com/en/residential/internet/cable |title=Cable |website=TekSavvy.com |access-date=2016-08-03 |archive-url=https://web.archive.org/web/20160801135543/http://teksavvy.com/en/residential/internet/cable |archive-date=2016-08-01 |url-status=dead }}</ref><ref>{{cite web|url=http://www.vmedia.ca/en/internet/compatible-modems |title=Compatible Modems |website=vmedia.ca |access-date=2021-10-27}}</ref><ref>{{cite web |url=http://www.acanac.ca/Approved_Modems_Ontario.html |title=Unlimited Internet Plans Quebec &#124; Cable, Fibre Optic &#124; Acanac |website=Acanac.ca |access-date=2016-08-03 |archive-url=https://web.archive.org/web/20150512090341/http://www.acanac.ca/Approved_Modems_Ontario.html |archive-date=2015-05-12 |url-status=dead }}</ref><ref>{{Cite web|url=http://www.worldline.ca/services/high-speed-internet/cable/75/|title=Fast Unlimited Download High Speed Cable 75 Internet Plus Home Phone Bundle|website=www.worldline.ca|language=en|access-date=2018-04-23}}</ref> identifying the 'allowed' modems by their brand, models, sometimes firmware version and occasionally going as far as imposing a hardware version of the modem, instead of simply allowing a supported DOCSIS version.