Jump to content

Cable modem: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous edit
Content deleted Content added
VisualWikitext
Tags: Reverted references removed
remove some confusing OSI info
 
(35 intermediate revisions by 17 users not shown)
Line 1: Line 1:
{{Short description|Broadband Internet access device}}
{{Short description|Broadband Internet access device}}
{{More citations needed|date=August 2010}}
{{Technical|date=May 2024}}
{{Use American English|date=November 2024}}
[[File:ARRIS CM820B DOCSIS Cable Modem.jpg|thumb|right|[[ARRIS Group|ARRIS]] Touchstone CM820B DOCSIS 3.0 cable modem]]


[[File:CBN CG3368 cable modem.jpg|thumb|Example of a cable modem installed in a home office.]]
⚫
A '''cable modem''' is a type of [[network bridge]] that provides bi-directional data communication via [[radio frequency channel]]s on a [[hybrid fibre-coaxial]] (HFC), [[radio frequency over glass]] (RFoG) and [[coaxial cable]] infrastructure. Cable modems are primarily used to deliver [[broadband Internet access]] in the form of [[cable Internet]], taking advantage of the high [[Bandwidth (signal processing)|bandwidth]] of a HFC and RFoG network. They are commonly deployed in the [[Americas]], [[Asia]], [[Australia]], and [[Europe]].

⚫
A '''cable modem''' is a type of [[network bridge]] that provides bi-directional data communication via [[radio frequency channel]]s on a [[hybrid fiber-coaxial]] (HFC), [[radio frequency over glass]] (RFoG) and [[coaxial cable]] infrastructure. Cable modems are primarily used to deliver [[broadband Internet access]] in the form of [[cable Internet]], taking advantage of the high [[Bandwidth (signal processing)|bandwidth]] of a HFC and RFoG network. They are commonly deployed in the [[Americas]], [[Asia]], [[Australia]], and [[Europe]].


==History==
==History==
===MITRE Cablenet===
===MITRE Cablenet===
[[Internet Experiment Note|Internet Experiment Note (IEN)]] 96<ref name="IEN 96">[http://ftp.rfc-editor.org/in-notes/ien/ien96.txt IEN 96] - The [[MITRE]] Cablenet Project</ref> (1979) describes an early [[Radio frequency|RF]] cable modem system. From pages 2 and 3 of IEN 96:
[[Internet Experiment Note|Internet Experiment Note (IEN)]] 96<ref name="IEN 96">[http://ftp.rfc-editor.org/in-notes/ien/ien96.txt IEN 96] - The [[MITRE]] Cablenet Project</ref> (1979) describes an early [[RF]] cable modem system. From pages 2 and 3 of IEN 96:
<blockquote>The Cable-Bus System
<blockquote>The Cable-Bus System


The MITRE/Washington Cablenet system is based on a technology developed at MITRE/Bedford. Similar cable-bus systems are in operation at a number of government sites, e.g. [[Walter Reed Army Medical Center|Walter Reed Army Hospital]], and the [[NASA]] [[Lyndon B. Johnson Space Center|Johnson Space Center]], but these are all standalone, local-only networks.
The MITRE/Washington Cablenet system is based on a technology developed at MITRE/Bedford. Similar cable-bus systems are in operation at a number of government sites, e.g. [[Walter Reed Army Hospital]], and the [[NASA]] [[Johnson Space Center]], but these are all standalone, local-only networks.


The system uses standard [[Cable television|Community Antenna Television]] (CATV) [[coaxial cable]] and microprocessor based Bus Interface Units (BIUs) to connect subscriber [[computer]]s and [[Terminal (telecommunication)|terminals]] to the cable. ... The cable bus consists of [[Four-wire circuit|two parallel]] coaxial cables, one inbound and the other outbound. The inbound cable and outbound cable are connected at one end, the [[Cable television headend|headend]], and [[Electrical termination|electrically terminated]] at their other ends. This architecture takes advantage of the well developed [[Simplex communication|unidirectional]] CATV [[Distribution amplifier|components]].<ref name="RF Micro Devices, Inc. Whitepaper Describing Historical CATV Components">{{cite web|url=http://www.piedmontscte.org/resources/CATV+Hybrid+Amplifier+Modules+Past$2C+Present$2C+FutureWP.pdf|title=RF Micro Devices, Inc. Whitepaper Describing Historical CATV Components|website=Piedmontscte.org|access-date=2016-08-03|quotation=Amplifiers are one of the common components used in CATV system}}</ref> The [[Network topology|topology]] is dendritic (i.e. [[Tree topology|branched like a tree]]).<br/>
The system uses standard [[community antenna television]] (CATV) [[coaxial cable]] and microprocessor based Bus Interface Units (BIUs) to connect subscriber [[computer]]s and [[Terminal (telecommunication)|terminals]] to the cable. ... The cable bus consists of [[Four-wire circuit|two parallel]] coaxial cables, one inbound and the other outbound. The inbound cable and outbound cable are connected at one end, the [[Cable television headend|headend]], and [[Electrical termination|electrically terminated]] at their other ends. This architecture takes advantage of the well developed [[Simplex communication|unidirectional]] CATV [[Distribution amplifier|components]].<ref name="RF Micro Devices, Inc. Whitepaper Describing Historical CATV Components">{{cite web|url=http://www.piedmontscte.org/resources/CATV+Hybrid+Amplifier+Modules+Past$2C+Present$2C+FutureWP.pdf|title=RF Micro Devices, Inc. Whitepaper Describing Historical CATV Components|website=Piedmontscte.org|access-date=2016-08-03|quotation=Amplifiers are one of the common components used in CATV system}}</ref> The [[Network topology|topology]] is dendritic (i.e. [[Tree topology|branched like a tree]]).<br/>
...<br/>
...<br/>
The BIUs contain [[Radio frequency|Radio Frequency]] (RF) modems which [[Modulation|modulate]] a [[carrier signal]] to transmit [[Digital signal (electronics)|digital]] [[Information theory|information]] using 1 [[Hertz|MHz]] of the available [[Bandwidth (signal processing)|bandwidth]] in the 24 MHz frequency range. The remainder of the 294 MHz bandwidth can be used to carry other [[communication channel]]s, such as [[Terrestrial television|off-the-air]] [[NTSC|TV]], [[FM radio|FM]], [[Closed-circuit television|closed circuit TV]], or a [[Voice frequency|voice]] [[Digital Telephony|telephone system]], or, other digital channels. The [[Bit rate|data rate]] of our test-bed system is 307.2&nbsp;[[Kilobit per second|kbps]].</blockquote>
The BIUs contain [[Radio Frequency]] (RF) modems which [[Modulation|modulate]] a [[carrier signal]] to transmit [[Digital signal (electronics)|digital]] [[Information theory|information]] using 1 [[MHz]] of the available [[Bandwidth (signal processing)|bandwidth]] in the 24&nbsp;MHz frequency range. The remainder of the 294&nbsp;MHz bandwidth can be used to carry other [[communication channel]]s, such as [[Terrestrial television|off-the-air]] [[NTSC|TV]], [[FM radio|FM]], [[Closed-circuit television|closed circuit TV]], or a [[Voice frequency|voice]] [[Digital Telephony|telephone system]], or, other digital channels. The [[Bit rate|data rate]] of our test-bed system is 307.2&nbsp;[[Kilobit per second|kbps]].</blockquote>


===IEEE 802.3b (10BROAD36)===
===IEEE 802.3b (10BROAD36)===
The [[IEEE]] [[IEEE 802|802 Committee]] defined [[10BROAD36]] in [[10BROAD36|802.3b-1985]]<ref name="IEEE 802.3b (10BROAD36) Standard">[http://standards.ieee.org/findstds/standard/802.3b-1985.html IEEE 802.3b-1985 (10BROAD36)] {{Webarchive|url=https://web.archive.org/web/20120225203804/http://standards.ieee.org/findstds/standard/802.3b-1985.html |date=2012-02-25 }} - Supplement to 802.3: Broadband Medium Attachment Unit and Broadband Medium Specifications, Type 10BROAD36 (Section 11)</ref> as a 10 [[Bit rate|Mbit/s]] [[IEEE 802.3]]/[[Ethernet]] broadband system to run up to {{convert|3600|m}} over CATV coax network cabling. The word ''[[broadband]]'' as used in the original IEEE 802.3 specifications implied operation in [[Multiplexing#Frequency-division multiplexing|frequency-division multiplexed]] ([[Frequency-division multiplexing|FDM]]) channel bands as opposed to digital ''[[baseband]]'' [[Square wave|square-waveform]] [[modulation]]s (also known as [[line coding]]), which begin near zero [[Hz]] and [[Fourier series|theoretically]] consume [[Square wave#Fourier Analysis|infinite]] [[frequency bandwidth]]. (In real-world systems, higher-order [[signal]] [[Square wave#Fourier Analysis|components]] become indistinguishable from background [[Signal-to-noise ratio|noise]].) In the market [[10BROAD36]] equipment was not developed by many vendors nor deployed in many user networks as compared to equipment for IEEE 802.3/[[Ethernet]] [[Baseband#Baseband Ethernet|baseband]] standards such as [[10BASE5]] (1983), [[10BASE2]] (1985), [[10BASE-T]] (1990), etc.
A plaintiff who was injured as as result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant.A plaintiff is entitled to a verdict if jury finds1. That a defendant was negligent, and2. That such negligence was a cause of injury to the plaintiff.A plaintiff who was injured as as result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant.A plaintiff is entitled to a verdict if jury finds1. That a defendant was negligent, and2. That such negligence was a cause of injury to the plaintiff.A plaintiff who was injured as as result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant.A plaintiff is entitled to a verdict if jury finds1. That a defendant was negligent, and2. That such negligence was a cause of injury to the plaintiff.A plaintiff who was injured as as result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant.A plaintiff is entitled to a verdict if jury finds1. That a defendant was negligent, and2. That such negligence was a cause of injury to the plaintiff.A plaintiff who was injured as as result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant.A plaintiff is entitled to a verdict if jury finds1. That a defendant was negligent, and2. That such negligence was a cause of injury to the plaintiff.


===IEEE 802.7===
===IEEE 802.7===
The [[Institute of Electrical and Electronics Engineers|IEEE]] 802 Committee also specified a broadband CATV digital networking standard in 1989 with [[IEEE 802.7|802.7-1989]].<ref name="IEEE 802.7-1989 Standard">{{cite web|url=http://standards.ieee.org/findstds/standard/802.7-1989.html |title=IEEE SA - 802.7-1989 - Local Area Networks: IEEE Recommended Practice: Broadband Local Area Networks |website=Standards.ieee.org |date=1990-03-09 |access-date=2016-08-03}}</ref> However, like [[10BROAD36]], 802.7-1989 saw little commercial success.
The [[IEEE]] 802 Committee also specified a broadband CATV digital networking standard in 1989 with [[IEEE 802.7|802.7-1989]].<ref name="IEEE 802.7-1989 Standard">{{cite web|url=http://standards.ieee.org/findstds/standard/802.7-1989.html |archive-url=https://archive.today/20130415013437/http://standards.ieee.org/findstds/standard/802.7-1989.html |url-status=dead |archive-date=April 15, 2013 |title=IEEE SA - 802.7-1989 - Local Area Networks: IEEE Recommended Practice: Broadband Local Area Networks |website=[[IEEE]] |date=1990-03-09 |access-date=2016-08-03}}</ref> However, like [[10BROAD36]], 802.7-1989 saw little commercial success.


===Hybrid networks===
===Hybrid networks===
Hybrid Networks developed, demonstrated and patented the first high-speed, asymmetrical cable modem system in 1990. A key Hybrid Networks insight was that in the nascent days of the Internet, data downloading constitutes the majority of the data traffic, and this can be served adequately with a highly asymmetrical data network (i.e. a large downstream data pipe and many small upstream data pipes). This allowed CATV operators to offer high speed data services immediately without first requiring an expensive system upgrade. Also key was that it saw that the upstream and downstream communications could be on the same or different communications media using different protocols working in each direction to establish a closed loop communications system. The speeds and protocols used in each direction would be very different. The earliest systems used the [[public switched telephone network]] (PSTN) for the return path since very few cable systems were bi-directional. Later systems used CATV for the upstream as well as the downstream path. Hybrid's system architecture is used for most cable modem systems today.
Hybrid Networks developed, demonstrated and patented the first high-speed, asymmetrical cable modem system in 1990. A key Hybrid Networks insight was that in the nascent days of the Internet, data downloading constitutes the majority of the data traffic, and this can be served adequately with a highly asymmetrical data network (i.e. a large downstream data pipe and many small upstream data pipes). This allowed CATV operators to offer high-speed data services immediately without first requiring an expensive system upgrade. Also key was that it saw that the upstream and downstream communications could be on the same or different communications media using different protocols working in each direction to establish a closed-loop communications system. The speeds and protocols used in each direction would be very different. The earliest systems used the [[public switched telephone network]] (PSTN) for the return path since very few cable systems were bi-directional. Later systems used CATV for the upstream as well as the downstream path. Hybrid's system architecture is used for most cable modem systems today.


===LANcity===
===LANcity===
LANcity was an early pioneer in cable modems, developing a proprietary system that was widely deployed in the U.S. LANcity, which was led by the Iranian-American engineer [[Rouzbeh Yassini]], was then acquired by [[Bay Networks]].<ref>{{Cite web|url=https://www.cnet.com/news/bay-networks-to-acquire-lancity/|title=Bay Networks to acquire LANcity|last=staff|first=CNET News|website=CNET|language=en|access-date=2019-09-05}}</ref> Bay Networks was subsequently acquired by [[Nortel]].<ref>{{Cite web|url=https://www.sfgate.com/business/article/Telecom-Giants-To-Merge-Bay-Networks-bought-by-3003305.php|title=Telecom Giants To Merge / Bay Networks bought by Nortel for $7.2 billion|last1=Marshall|first1=Jonathan|last2=Writer|first2=Chronicle Staff|date=1998-06-16|website=SFGate|access-date=2019-09-05}}</ref> Nortel at the time had formed a joint-venture with [[Antec]] called [[Arris Group|ARRIS]] Interactive.<ref>{{Cite web|url=https://www.cnet.com/news/nortel-ups-stake-in-joint-venture-with-antec/|title=Nortel ups stake in joint venture with Antec|website=CNET|language=en|access-date=2019-09-05}}</ref> Because of contractual agreements with Antec involving this joint venture, Nortel spun the LANCity group out into the ARRIS Interactive joint-venture. ARRIS continues to make cable modems and [[cable modem termination system]] (CMTS) equipment compliant with the [[DOCSIS]] standard.
LANcity was an early pioneer in cable modems, developing a proprietary system that was widely deployed in the U.S. LANcity, which was led by the Iranian-American engineer [[Rouzbeh Yassini]], was then acquired by [[Bay Networks]].<ref>{{Cite web|url=https://www.cnet.com/news/bay-networks-to-acquire-lancity/|title=Bay Networks to acquire LANcity|last=staff|first=CNET News|website=CNET|language=en|access-date=2019-09-05}}</ref> Bay Networks was subsequently acquired by [[Nortel]].<ref>{{Cite web|url=https://www.sfgate.com/business/article/Telecom-Giants-To-Merge-Bay-Networks-bought-by-3003305.php|title=Telecom Giants To Merge / Bay Networks bought by Nortel for $7.2 billion|last1=Marshall|first1=Jonathan|last2=Writer|first2=Chronicle Staff|date=1998-06-16|website=SFGate|access-date=2019-09-05}}</ref> Nortel at the time had formed a joint-venture with [[Antec]] called [[ARRIS]] Interactive.<ref>{{Cite web|url=https://www.cnet.com/news/nortel-ups-stake-in-joint-venture-with-antec/|title=Nortel ups stake in joint venture with Antec|website=CNET|language=en|access-date=2019-09-05}}</ref> Because of contractual agreements with Antec involving this joint venture, Nortel spun the LANCity group out into the ARRIS Interactive joint-venture. ARRIS continues to make cable modems and [[cable modem termination system]] (CMTS) equipment compliant with the [[DOCSIS]] standard.


===Zenith homeworks===
===Zenith homeworks===
[[Zenith Electronics|Zenith]] offered a cable modem technology using its own protocol which it introduced in 1993, being one of the first cable modem providers. The [[Zenith Cable Modem]] technology was used by several cable television systems in the United States and other countries, including Cox Communications San Diego, Knology in the Southeast United States, [[Ameritech]]'s Americast service (later to be sold off to [[Wide Open West]] after the SBC / Ameritech merger), Cogeco in Hamilton Ontario and Cablevision du Nord de Québec in Val-d'Or.<ref>{{cite news|title=Americast Places $1-Billion Order for Set-Top Boxes |newspaper=[[Los Angeles Times]]|author=Sallie Hofmeister|url=http://articles.latimes.com/1996-08-23/business/fi-36983_1_set-top-boxes|access-date=2010-08-28 | date=1996-08-23}}</ref> Zenith Homeworks used BPSK (Bi-Phase Shift Keyed) modulation to achieve 500 Kbit/sec in 600&nbsp;kHz, or 4 Mbit/sec in 6&nbsp;MHz.<ref>{{cite book|title=Network Design: Principles and Applications|author=Gilbert Held|year=2000|page=765|publisher=Auerbach Publications|url=https://books.google.com/books?id=06uBL8vGpoIC&q=zenith+cable+modem&pg=PA765|isbn=978-0-8493-0859-8}}</ref>
[[Zenith Electronics|Zenith]] offered a cable modem technology using its own protocol which it introduced in 1993, being one of the first cable modem providers. The [[Zenith Cable Modem]] technology was used by several cable television systems in the United States and other countries, including Cox Communications San Diego, Knology in the Southeast United States, [[Ameritech]]'s Americast service (later to be sold off to [[Wide Open West]] after the SBC / Ameritech merger), Cogeco in Hamilton Ontario and Cablevision du Nord de Québec in Val-d'Or.<ref>{{cite news|title=Americast Places $1-Billion Order for Set-Top Boxes |newspaper=[[Los Angeles Times]]|author=Sallie Hofmeister|url=https://www.latimes.com/archives/la-xpm-1996-08-23-fi-36983-story.html|access-date=2010-08-28 | date=1996-08-23}}</ref> Zenith Homeworks used BPSK (Bi-Phase Shift Keyed) modulation to achieve 500&nbsp;Kbit/sec in 600&nbsp;kHz, or 4&nbsp;Mbit/sec in 6&nbsp;MHz.<ref>{{cite book|title=Network Design: Principles and Applications|author=Gilbert Held|year=2000|page=765|publisher=Auerbach Publications|url=https://books.google.com/books?id=06uBL8vGpoIC&q=zenith+cable+modem&pg=PA765|isbn=978-0-8493-0859-8}}</ref>


===Com21===
===Com21===
{{main|Com21}}
{{main|Com21}}
[[Com21]] was another early pioneer in cable modems, and quite successful until proprietary systems were made obsolete by the DOCSIS standardization. The Com21 system used a ''ComController'' as central bridge in CATV network head-ends, the ComPort cable modem in various models and the NMAPS management system using [[HP OpenView]] as platform. Later they also introduced a return path multiplexer to overcome noise problems when combining return path signals from multiple areas. The proprietary protocol was based on [[Asynchronous Transfer Mode]] (ATM). The central ComController switch was a modular system offering one downstream channel (transmitter) and one management module. The remaining slots could be used for upstream receivers (2 per card), dual Ethernet 10BaseT and later also Fast-Ethernet and ATM interfaces. The ATM interface became the most popular, as it supported the increasing bandwidth demands and also supported [[VLAN]]s.
[[Com21]] was another early pioneer in cable modems, and quite successful until proprietary systems were made obsolete by the DOCSIS standardization. The Com21 system used a ''ComController'' as the central bridge in CATV network head-ends, the ComPort cable modem in various models and the NMAPS management system using [[HP OpenView]] as the platform. Later they also introduced a return path multiplexer to overcome noise problems when combining return path signals from multiple areas. The proprietary protocol was based on [[Asynchronous Transfer Mode]] (ATM). The central ComController switch was a modular system offering one downstream channel (transmitter) and one management module. The remaining slots could be used for upstream receivers (2 per card), dual Ethernet 10BaseT and later also Fast-Ethernet and ATM interfaces. The ATM interface became the most popular, as it supported the increasing bandwidth demands and also supported [[VLAN]]s.
Com21 developed a DOCSIS modem, but the company filed for bankruptcy in 2003 and closed. The DOCSIS CMTS assets of COM21 were acquired by [[Arris Group|ARRIS]].
Com21 developed a DOCSIS modem, but the company filed for bankruptcy in 2003 and closed. The DOCSIS CMTS assets of COM21 were acquired by [[ARRIS]].


===CDLP===
===CDLP===
CDLP was a proprietary system manufactured by [[Motorola]]. CDLP [[customer premises equipment]] (CPE) was capable of both [[PSTN|PSTN (telephone network)]] and [[cable network|radio frequency (cable network)]] return paths. The PSTN-based service was considered 'one-way cable' and had many of the same drawbacks as [[satellite Internet]] service; as a result, it quickly gave way to "two-way cable." Cable modems that used the RF cable network for the return path were considered 'two-way cable', and were better able to compete with the bi-directional [[digital subscriber line]] (DSL) service. The standard is in little use now while new providers use, and existing providers having changed to the DOCSIS standard. The Motorola CDLP proprietary CyberSURFR is an example of a device that was built to the CDLP standard, capable of a peak 10 [[Mbit/s]] downstream and 1.532 Mbit/s upstream. CDLP supported a maximum downstream bandwidth of 30 Mbit/s which could be reached by using several cable modems.
CDLP was a proprietary system manufactured by [[Motorola]]. CDLP [[customer premises equipment]] (CPE) was capable of both [[PSTN|PSTN (telephone network)]] and radio frequency (cable) return paths. The PSTN-based service was considered 'one-way cable' and had many of the same drawbacks as [[satellite Internet]] service; as a result, it quickly gave way to "two-way cable." Cable modems that used the RF cable network for the return path were considered 'two-way cable', and were better able to compete with the bi-directional [[digital subscriber line]] (DSL) service. The standard is in little use now as new providers use, and existing providers having changed to, the DOCSIS standard. The Motorola CDLP proprietary CyberSURFR is an example of a device that was built to the CDLP standard, capable of a peak 10&nbsp;[[Mbit/s]] downstream and 1.532&nbsp;Mbit/s upstream. CDLP supported a maximum downstream bandwidth of 30&nbsp;Mbit/s which could be reached by using several cable modems.


The [[Australia]]n ISP [[BigPond]] employed this system when it started cable modem tests in 1996. For a number of years [[cable Internet access]] was only available in [[Sydney]], [[Melbourne]] and [[Brisbane]] via CDLP. This network ran parallel to the newer DOCSIS system for several years. In 2004, the CDLP network was terminated and replaced by DOCSIS.
The [[Australia]]n ISP [[BigPond]] employed this system when it started cable modem tests in 1996. For a number of years [[cable Internet access]] was only available in [[Sydney]], [[Melbourne]] and [[Brisbane]] via CDLP. This network ran parallel to the newer DOCSIS system for several years. In 2004, the CDLP network was terminated and replaced by DOCSIS.
Line 44: Line 46:


===DVB/DAVIC===
===DVB/DAVIC===
[[Digital Video Broadcasting]] ([[Digital Video Broadcasting|DVB]]) and [[DAVIC|Digital Audio Visual Council]] (DAVIC) are European-formed organizations that developed some cable modem standards. However, these standards have not been as widely adopted as DOCSIS.
[[Digital Video Broadcasting]] ([[DVB]]) and [[DAVIC|Digital Audio Visual Council]] (DAVIC) are European-formed organizations that developed some cable modem standards. However, these standards have not been as widely adopted as DOCSIS.


===IEEE 802.14===
===IEEE 802.14===
In the mid-1990s the [[IEEE 802]] committee formed a subcommittee (802.14)<ref name="IEEE 802.14 WG Homepage">{{cite web|url=http://walkingdog.com/ |title=WalkingDog.com |access-date=2012-05-13 |url-status=bot: unknown |archive-url=https://web.archive.org/web/19961226193928/http://walkingdog.com/ |archive-date=1996-12-26 }} The IEEE 802.14 Working Group used WalkingDog.com as its web site.</ref> to develop a standard for cable modem systems. IEEE 802.14 developed a draft standard, which was [[Asynchronous Transfer Mode|ATM-based]]. However, the [[IEEE 802.14|802.14]] working group was disbanded when North American [[multiple system operator|multi system operators]] ([[multiple system operator|MSOs]]) instead backed the then-fledgling [[DOCSIS|DOCSIS 1.0]] specification, which generally used [[Best-effort|best efforts service]] and was [[Internet Protocol|IP-based]] (with extension [[Code point|codepoints]] to support [[Asynchronous Transfer Mode|ATM]]<ref name="DOCSIS RFI 1.0-I01">[http://www.cablelabs.com/specifications/SP-RFI-I01-970326.pdf DOCSIS RFI 1.0-I01 (March 26, 1997)] {{webarchive|url=https://web.archive.org/web/20110525094347/http://www.cablelabs.com/specifications/SP-RFI-I01-970326.pdf |date=May 25, 2011 }} (See section 6.2.3 for the DOCSIS [[Asynchronous Transfer Mode|ATM]] codepoint. See sections 6.1.2.3, 6.2.5.3, 6.4.7, 9, and 9.2.2 for DOCSIS 1.0 [[Quality of service|QoS]] mechanisms.)</ref> for [[Quality of service|QoS]] in the future). [[multiple system operator|MSOs]] were interested in quickly deploying service to compete for [[Internet access|broadband Internet access]] customers instead of waiting on the slower, iterative, and deliberative processes of standards development committees. Albert A. Azzam was Secretary of the IEEE 802.14 Working Group,<ref name="IEEE 802.14 WG Officers">{{cite web|url=http://www.walkingdog.com/catv/officers.htm |title=IEEE 802.14 WG Officers |access-date=2012-05-13 |url-status=bot: unknown |archive-url=https://web.archive.org/web/19970129161548/http://www.walkingdog.com/catv/officers.htm |archive-date=1997-01-29 }}</ref> and his book, ''High-Speed Cable Modems'',<ref name="Azzam - High Speed Cable Modems">Albert A. Azzam, ''High-Speed Cable Modems'' {{ISBN|978-0-07-006417-1}}</ref> describes many of the proposals submitted to 802.14.
In the mid-1990s the [[IEEE 802]] committee formed a subcommittee (802.14)<ref name="IEEE 802.14 WG Homepage">{{cite web|url=http://walkingdog.com/ |title=WalkingDog.com |access-date=2012-05-13 |url-status=bot: unknown |archive-url=https://web.archive.org/web/19961226193928/http://walkingdog.com/ |archive-date=1996-12-26 }} The IEEE 802.14 Working Group used WalkingDog.com as its web site.</ref> to develop a standard for cable modem systems. IEEE 802.14 developed a draft standard, which was [[Asynchronous Transfer Mode|ATM-based]]. However, the [[IEEE 802.14|802.14]] working group was disbanded when North American [[multiple system operator|multi system operators]] ([[multiple system operator|MSOs]]) instead backed the then-fledgling [[DOCSIS|DOCSIS 1.0]] specification, which generally used [[best-effort service]] and was [[Internet Protocol|IP-based]] (with extension [[Code point|codepoints]] to support [[Asynchronous Transfer Mode|ATM]]<ref name="DOCSIS RFI 1.0-I01">[http://www.cablelabs.com/specifications/SP-RFI-I01-970326.pdf DOCSIS RFI 1.0-I01 (March 26, 1997)] {{webarchive|url=https://web.archive.org/web/20110525094347/http://www.cablelabs.com/specifications/SP-RFI-I01-970326.pdf |date=May 25, 2011 }} (See section 6.2.3 for the DOCSIS [[Asynchronous Transfer Mode|ATM]] codepoint. See sections 6.1.2.3, 6.2.5.3, 6.4.7, 9, and 9.2.2 for DOCSIS 1.0 QoS mechanisms.)</ref> for [[Quality of service|QoS]] in the future). [[multiple system operator|MSOs]] were interested in quickly deploying service to compete for [[Internet access|broadband Internet access]] customers instead of waiting on the slower, iterative, and deliberative processes of standards development committees. Albert A. Azzam was Secretary of the IEEE 802.14 Working Group,<ref name="IEEE 802.14 WG Officers">{{cite web|url=http://www.walkingdog.com/catv/officers.htm |title=IEEE 802.14 WG Officers |access-date=2012-05-13 |url-status=bot: unknown |archive-url=https://web.archive.org/web/19970129161548/http://www.walkingdog.com/catv/officers.htm |archive-date=1997-01-29 }}</ref> and his book, ''High-Speed Cable Modems'',<ref name="Azzam - High Speed Cable Modems">{{cite book |last1=Azzam |first1=Albert A. |title=High speed cable modems : including IEEE 802.14 standards |date=1997 |publisher=New York : McGraw-Hill |location=New York, NY |isbn=978-0-07-006417-1 |url=https://archive.org/details/highspeedcablemo0000azza |access-date=7 April 2024}}</ref> describes many of the proposals submitted to 802.14.


===IETF===
===IETF===
Although the [[Internet Engineering Task Force]] (IETF) generally does not generate complete cable modem standards, the IETF chartered [[Working group|Working Groups]] ([[Working group|WGs]]) that produced various standards related to cable modem technologies (including 802.14, DOCSIS, [[PacketCable]], and others). In particular, the IETF WGs on IP over Cable Data Network (IPCDN)<ref name="IETF IPCDN WG">{{cite web|url=http://tools.ietf.org/wg/ipcdn/ |title=Ipcdn Status Pages |website=Tools.ietf.org |access-date=2016-08-03}}</ref> and IP over [[Digital Video Broadcasting]] (DVB)<ref name="IETF IPDVB WG">{{cite web|url=http://tools.ietf.org/wg/ipdvb/ |title=Ipdvb Status Pages |website=Tools.ietf.org |access-date=2016-08-03}}</ref> produced some standards applicable to cable modem systems, primarily in the areas of [[Simple Network Management Protocol]] (SNMP) [[Management information base|Management Information Bases]] ([[Management information base|MIBs]]) for cable modems and other networking equipment that operates over CATV [[Television network|networks]].
Although the [[Internet Engineering Task Force]] (IETF) generally does not generate complete cable modem standards, the IETF chartered [[Working Groups]] ([[Working group|WGs]]) that produced various standards related to cable modem technologies (including 802.14, DOCSIS, [[PacketCable]], and others). In particular, the IETF WGs on IP over Cable Data Network (IPCDN)<ref name="IETF IPCDN WG">{{cite web|url=http://tools.ietf.org/wg/ipcdn/ |title=Ipcdn Status Pages |website=Tools.ietf.org |access-date=2016-08-03}}</ref> and IP over [[Digital Video Broadcasting]] (DVB)<ref name="IETF IPDVB WG">{{cite web|url=http://tools.ietf.org/wg/ipdvb/ |title=Ipdvb Status Pages |website=Tools.ietf.org |access-date=2016-08-03}}</ref> produced some standards applicable to cable modem systems, primarily in the areas of [[Simple Network Management Protocol]] (SNMP) [[Management information base|Management Information Bases]] ([[Management information base|MIBs]]) for cable modems and other networking equipment that operates over CATV [[Television network|networks]].


===DOCSIS===
===DOCSIS===
Line 56: Line 58:
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.
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 supports [[Best-effort|best efforts service]], the DOCSIS RFI 1.0 Interim-01 document discussed [[Quality of service|QoS]] extensions and mechanisms using [[Integrated services|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 [[Quality of service|QoS]] mechanisms to DOCSIS. [[DOCSIS|DOCSIS 2.0]] added support for [[Synchronous Code Division Multiple Access|S-CDMA]] [[PHY]], while DOCSIS 3.0 added [[Internet Protocol version 6|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.
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|quality of servce (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 USA'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 USA and 8&nbsp;MHz for Europe. A third variant of DOCSIS was developed in [[Japan]] and has seen limited deployment in that country.
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.
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.
Line 75: Line 77:
In network topology, a cable modem is a [[network bridge]] that conforms to [[IEEE 802.1D]] for [[Ethernet]] networking (with some modifications). The cable modem bridges Ethernet frames between a customer [[LAN]] and the coax network. Technically, it is a modem because it must modulate data to transmit it over the cable network, and it must demodulate data from the cable network to receive it.
In network topology, a cable modem is a [[network bridge]] that conforms to [[IEEE 802.1D]] for [[Ethernet]] networking (with some modifications). The cable modem bridges Ethernet frames between a customer [[LAN]] and the coax network. Technically, it is a modem because it must modulate data to transmit it over the cable network, and it must demodulate data from the cable network to receive it.


⚫
It implements an [[Ethernet over twisted pair|Ethernet PHY]] on its LAN [[Network interface controller|interface]], and a DOCSIS-defined cable-specific [[PHY]] on its HFC cable interface. The term ''cable modem'' refers to this cable-specific PHY. The [[Network Layer]] is implemented as an IP host in that it has its own [[IP address]] used by the network operator to maintain the device. In the [[transport layer]] the cable modem supports [[User Datagram Protocol|UDP]] in association with its own IP address, and it supports filtering based on [[TCP and UDP port]] numbers to, for example, block forwarding of [[NetBIOS]] traffic out of the customer's LAN. In the [[Application Layer]], the cable modem supports certain protocols that are used for management and maintenance, notably [[Dynamic Host Configuration Protocol]] (DHCP), [[SNMP]], and [[TFTP]].
With respect to the [[OSI model]] of [[network planning and design|network design]], a cable modem is both physical layer (layer 1) device and a [[data link layer]] (layer 2) forwarder. As an [[IP address]]able network node, cable modems support functionality at other layers.

⚫
Layer 1 is implemented in the [[Ethernet over twisted pair|Ethernet PHY]] on its LAN [[Network interface controller|interface]], and a DOCSIS defined cable-specific [[PHY]] on its HFC cable interface. The term ''cable modem'' refers to this cable-specific PHY. The [[Network Layer]] (Layer 3) is implemented as an [[Internet protocol|IP]] host in that it has its own [[IP address]] used by the network operator to maintain the device. In the [[transport layer]] (layer 4) the cable modem supports [[user datagram protocol|UDP]] in association with its own IP address, and it supports filtering based on [[TCP and UDP port]] numbers to, for example, block forwarding of [[NetBIOS]] traffic out of the customer's LAN. In the [[Application Layer]] (Layer 7), the cable modem supports certain protocols that are used for management and maintenance, notably [[Dynamic Host Configuration Protocol]] (DHCP), [[SNMP]], and [[trivial file transfer protocol|TFTP]].


Some cable modems may incorporate a [[Router (computing)|router]] and a DHCP server to provide the LAN with [[Internet Protocol|IP]] network addressing. From a data forwarding and network topology perspective, this router functionality is typically kept distinct from the cable modem functionality (at least logically) even though the two may share a single enclosure and appear as one unit, sometimes called a [[residential gateway]]. So, the cable modem function will have its own [[IP address]] and [[MAC address]] as will the router.
Some cable modems may incorporate a [[Router (computing)|router]] and a DHCP server to provide the LAN with IP network addressing. From a data forwarding and network topology perspective, this router functionality is typically kept distinct from the cable modem functionality (at least logically) even though the two may share a single enclosure and appear as one unit, sometimes called a [[residential gateway]]. So, the cable modem function will have its own [[IP address]] and [[MAC address]] as will the router.


==Cable modem flap==
==Cable modem flap==
Line 85: Line 85:


== Known vulnerabilities ==
== Known vulnerabilities ==
In January 2020, a vulnerability affecting cable modems using [[Broadcom]] chipsets was disclosed and named [[Cable Haunt]]. Security researchers say that the vulnerability affects hundreds of millions of devices. Exploits are possible because of the use of default credentials in the [[spectrum analyzer]] component of the modem (mostly used for debugging purposes) accessible through a network [[port (network)|port]] which is open by default in the vulnerable models.<ref>{{cite journal|url=https://www.zdnet.com/article/hundreds-of-millions-of-cable-modems-are-vulnerable-to-new-cable-haunt-vulnerability/|title=Hundreds of millions of cable modems are vulnerable to new Cable Haunt vulnerability|journal=Zdnet}}</ref><ref>{{Cite web|url=https://arstechnica.com/information-technology/2020/01/exploit-that-gives-remote-access-affects-200-million-cable-modems/|title=Exploit that gives remote access affects ~200 million cable modems|last=Goodin|first=Dan|date=2020-01-13|website=Ars Technica|language=en-us|access-date=2020-01-15}}</ref>
In January 2020, a vulnerability affecting cable modems using [[Broadcom]] chipsets was disclosed and named [[Cable Haunt]]. Security researchers say that the vulnerability affects hundreds of millions of devices. Exploits are possible because of the use of default credentials in the [[spectrum analyzer]] component of the modem (mostly used for debugging purposes) accessible through a network [[port (network)|port]] which is open by default in the vulnerable models.<ref>{{cite journal|url=https://www.zdnet.com/article/hundreds-of-millions-of-cable-modems-are-vulnerable-to-new-cable-haunt-vulnerability/|title=Hundreds of millions of cable modems are vulnerable to new Cable Haunt vulnerability|journal=ZDNet}}</ref><ref>{{Cite web|url=https://arstechnica.com/information-technology/2020/01/exploit-that-gives-remote-access-affects-200-million-cable-modems/|title=Exploit that gives remote access affects ~200 million cable modems|last=Goodin|first=Dan|date=2020-01-13|website=Ars Technica|language=en-us|access-date=2020-01-15}}</ref>


==See also==
==See also==
{{colbegin}}
{{colbegin}}
*[[Cable modem termination system]] (CMTS)
*[[Cable telephone]]
*[[Cable telephone]]
*[[Internet access#Cable Internet access|Internet access with a cable modem]]
*[[Internet access#Cable Internet access|Internet access with a cable modem]]
*[[List of device bandwidths]]
*[[List of device bandwidths]]
*[[NABU Network]]
*[[Triple play (telecommunications)]]
*[[Triple play (telecommunications)]]
*[[HomePNA]]
*[[HomePNA]]
Line 100: Line 102:


== Further reading ==
== Further reading ==
* {{cite web|title=How Cable Modems Work|author=Curt Franklin|url=http://computer.howstuffworks.com/cable-modem.htm/printable|publisher=[[HowStuffWorks]]|access-date=2010-08-28}}
* {{cite web|title=How Cable Modems Work|author=Curt Franklin|date=20 September 2000 |url=http://computer.howstuffworks.com/cable-modem.htm/printable|publisher=[[HowStuffWorks]]|access-date=2010-08-28}}
* {{cite magazine|title=How It Works: Cable Modems|url=http://www.pcworld.com/article/14281-2/how_it_works_cable_modems.html|author=Andrew Brandt|magazine=[[PC World (magazine)|PC World]]|year=1999|access-date=2010-08-28|archive-url=https://web.archive.org/web/20111103142827/http://www.pcworld.com/article/14281-2/how_it_works_cable_modems.html|archive-date=2011-11-03|url-status=dead}}
* {{cite magazine|title=How It Works: Cable Modems|url=http://www.pcworld.com/article/14281-2/how_it_works_cable_modems.html|author=Andrew Brandt|magazine=[[PC World]]|year=1999|access-date=2010-08-28|archive-url=https://web.archive.org/web/20111103142827/http://www.pcworld.com/article/14281-2/how_it_works_cable_modems.html|archive-date=2011-11-03|url-status=dead}}


==External links==
==External links==
{{Commons category|Cable modems}}
{{Commons category|Cable modems}}
* {{Curlie|Computers/Data_Communications/Cable_Modem/}}


{{Internet Access}}
{{Internet Access}}

Latest revision as of 23:18, 21 November 2024

Example of a cable modem installed in a home office.

A cable modem is a type of network bridge that provides bi-directional data communication via radio frequency channels on a hybrid fiber-coaxial (HFC), radio frequency over glass (RFoG) and coaxial cable infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. They are commonly deployed in the Americas, Asia, Australia, and Europe.

History

[edit]

MITRE Cablenet

[edit]

Internet Experiment Note (IEN) 96[1] (1979) describes an early RF cable modem system. From pages 2 and 3 of IEN 96:

The Cable-Bus System

The MITRE/Washington Cablenet system is based on a technology developed at MITRE/Bedford. Similar cable-bus systems are in operation at a number of government sites, e.g. Walter Reed Army Hospital, and the NASA Johnson Space Center, but these are all standalone, local-only networks.

The system uses standard community antenna television (CATV) coaxial cable and microprocessor based Bus Interface Units (BIUs) to connect subscriber computers and terminals to the cable. ... The cable bus consists of two parallel coaxial cables, one inbound and the other outbound. The inbound cable and outbound cable are connected at one end, the headend, and electrically terminated at their other ends. This architecture takes advantage of the well developed unidirectional CATV components.[2] The topology is dendritic (i.e. branched like a tree).
...

The BIUs contain Radio Frequency (RF) modems which modulate a carrier signal to transmit digital information using 1 MHz of the available bandwidth in the 24 MHz frequency range. The remainder of the 294 MHz bandwidth can be used to carry other communication channels, such as off-the-air TV, FM, closed circuit TV, or a voice telephone system, or, other digital channels. The data rate of our test-bed system is 307.2 kbps.

IEEE 802.3b (10BROAD36)

[edit]

The IEEE 802 Committee defined 10BROAD36 in 802.3b-1985[3] as a 10 Mbit/s IEEE 802.3/Ethernet broadband system to run up to 3,600 metres (11,800 ft) over CATV coax network cabling. The word broadband as used in the original IEEE 802.3 specifications implied operation in frequency-division multiplexed (FDM) channel bands as opposed to digital baseband square-waveform modulations (also known as line coding), which begin near zero Hz and theoretically consume infinite frequency bandwidth. (In real-world systems, higher-order signal components become indistinguishable from background noise.) In the market 10BROAD36 equipment was not developed by many vendors nor deployed in many user networks as compared to equipment for IEEE 802.3/Ethernet baseband standards such as 10BASE5 (1983), 10BASE2 (1985), 10BASE-T (1990), etc.

IEEE 802.7

[edit]

The IEEE 802 Committee also specified a broadband CATV digital networking standard in 1989 with 802.7-1989.[4] However, like 10BROAD36, 802.7-1989 saw little commercial success.

Hybrid networks

[edit]

Hybrid Networks developed, demonstrated and patented the first high-speed, asymmetrical cable modem system in 1990. A key Hybrid Networks insight was that in the nascent days of the Internet, data downloading constitutes the majority of the data traffic, and this can be served adequately with a highly asymmetrical data network (i.e. a large downstream data pipe and many small upstream data pipes). This allowed CATV operators to offer high-speed data services immediately without first requiring an expensive system upgrade. Also key was that it saw that the upstream and downstream communications could be on the same or different communications media using different protocols working in each direction to establish a closed-loop communications system. The speeds and protocols used in each direction would be very different. The earliest systems used the public switched telephone network (PSTN) for the return path since very few cable systems were bi-directional. Later systems used CATV for the upstream as well as the downstream path. Hybrid's system architecture is used for most cable modem systems today.

LANcity

[edit]

LANcity was an early pioneer in cable modems, developing a proprietary system that was widely deployed in the U.S. LANcity, which was led by the Iranian-American engineer Rouzbeh Yassini, was then acquired by Bay Networks.[5] Bay Networks was subsequently acquired by Nortel.[6] Nortel at the time had formed a joint-venture with Antec called ARRIS Interactive.[7] Because of contractual agreements with Antec involving this joint venture, Nortel spun the LANCity group out into the ARRIS Interactive joint-venture. ARRIS continues to make cable modems and cable modem termination system (CMTS) equipment compliant with the DOCSIS standard.

Zenith homeworks

[edit]

Zenith offered a cable modem technology using its own protocol which it introduced in 1993, being one of the first cable modem providers. The Zenith Cable Modem technology was used by several cable television systems in the United States and other countries, including Cox Communications San Diego, Knology in the Southeast United States, Ameritech's Americast service (later to be sold off to Wide Open West after the SBC / Ameritech merger), Cogeco in Hamilton Ontario and Cablevision du Nord de Québec in Val-d'Or.[8] Zenith Homeworks used BPSK (Bi-Phase Shift Keyed) modulation to achieve 500 Kbit/sec in 600 kHz, or 4 Mbit/sec in 6 MHz.[9]

Com21

[edit]
Main article: Com21

Com21 was another early pioneer in cable modems, and quite successful until proprietary systems were made obsolete by the DOCSIS standardization. The Com21 system used a ComController as the central bridge in CATV network head-ends, the ComPort cable modem in various models and the NMAPS management system using HP OpenView as the platform. Later they also introduced a return path multiplexer to overcome noise problems when combining return path signals from multiple areas. The proprietary protocol was based on Asynchronous Transfer Mode (ATM). The central ComController switch was a modular system offering one downstream channel (transmitter) and one management module. The remaining slots could be used for upstream receivers (2 per card), dual Ethernet 10BaseT and later also Fast-Ethernet and ATM interfaces. The ATM interface became the most popular, as it supported the increasing bandwidth demands and also supported VLANs. Com21 developed a DOCSIS modem, but the company filed for bankruptcy in 2003 and closed. The DOCSIS CMTS assets of COM21 were acquired by ARRIS.

CDLP

[edit]

CDLP was a proprietary system manufactured by Motorola. CDLP customer premises equipment (CPE) was capable of both PSTN (telephone network) and radio frequency (cable) return paths. The PSTN-based service was considered 'one-way cable' and had many of the same drawbacks as satellite Internet service; as a result, it quickly gave way to "two-way cable." Cable modems that used the RF cable network for the return path were considered 'two-way cable', and were better able to compete with the bi-directional digital subscriber line (DSL) service. The standard is in little use now as new providers use, and existing providers having changed to, the DOCSIS standard. The Motorola CDLP proprietary CyberSURFR is an example of a device that was built to the CDLP standard, capable of a peak 10 Mbit/s downstream and 1.532 Mbit/s upstream. CDLP supported a maximum downstream bandwidth of 30 Mbit/s which could be reached by using several cable modems.

The Australian ISP BigPond employed this system when it started cable modem tests in 1996. For a number of years cable Internet access was only available in Sydney, Melbourne and Brisbane via CDLP. This network ran parallel to the newer DOCSIS system for several years. In 2004, the CDLP network was terminated and replaced by DOCSIS.

CDLP has been also rolled out at the French cable operator Numericable before upgrading its IP broadband network using DOCSIS.

DVB/DAVIC

[edit]

Digital Video Broadcasting (DVB) and Digital Audio Visual Council (DAVIC) are European-formed organizations that developed some cable modem standards. However, these standards have not been as widely adopted as DOCSIS.

IEEE 802.14

[edit]

In the mid-1990s the IEEE 802 committee formed a subcommittee (802.14)[10] to develop a standard for cable modem systems. IEEE 802.14 developed a draft standard, which was ATM-based. However, the 802.14 working group was disbanded when North American multi system operators (MSOs) instead backed the then-fledgling DOCSIS 1.0 specification, which generally used best-effort service and was IP-based (with extension codepoints to support ATM[11] for QoS in the future). MSOs were interested in quickly deploying service to compete for broadband Internet access customers instead of waiting on the slower, iterative, and deliberative processes of standards development committees. Albert A. Azzam was Secretary of the IEEE 802.14 Working Group,[12] and his book, High-Speed Cable Modems,[13] describes many of the proposals submitted to 802.14.

IETF

[edit]

Although the Internet Engineering Task Force (IETF) generally does not generate complete cable modem standards, the IETF chartered Working Groups (WGs) that produced various standards related to cable modem technologies (including 802.14, DOCSIS, PacketCable, and others). In particular, the IETF WGs on IP over Cable Data Network (IPCDN)[14] and IP over Digital Video Broadcasting (DVB)[15] produced some standards applicable to cable modem systems, primarily in the areas of Simple Network Management Protocol (SNMP) Management Information Bases (MIBs) for cable modems and other networking equipment that operates over CATV networks.

DOCSIS

[edit]
Main article: DOCSIS

In the late 1990s, a consortium of US 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 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 RFI 1.0 equipment generally only supported best-effort service, the DOCSIS RFI 1.0 Interim-01 document discussed quality of servce (QoS) extensions and mechanisms using IntServ, RSVP, RTP, and Synchronous Transfer Mode (STM) telephony (as opposed to ATM).[11] DOCSIS RFI 1.1[16] later added more robust and standardized QoS mechanisms to DOCSIS. DOCSIS 2.0 added support for 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 MHz for the US and 8 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,"[17] most cable operators only approve a very restricted list of cable modems on their network,[18][19][20][21] 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.

Multimedia over Coax Alliance

[edit]
Main article: Multimedia over Coax Alliance

In 2004, the Multimedia over Coax Alliance (MoCA) was established to develop industry standard for the connected home, using the existing coaxial cabling. Initially developed for in-home networking with MoCA 1.0/1.1, the MoCA standards has continued to develop with MoCA 2.0/2.1 in 2010 and MoCa 2.5 in 2016.

In 2017, Multimedia over Coax Alliance introduced MoCA Access specification, based on the MoCA 2.5 standard, suitable for addressing broadband network access in-building using coaxial cabling.[22] MoCA Access extends MoCA 2.5 in-home networking to fit operators and ISPs that are installing fiber-to-the-basement/drop point (FTTB/FTTdp) and want to use the existing coax for connection to each apartment or house."

Multimedia terminal adapter

[edit]

With the development of voice over Internet Protocol (VoIP) telephony, analog telephone adapters (ATA) have been incorporated into many cable modems for providing telephone service. An embedded ATA is known as an embedded multimedia terminal adapter (E-MTA).

Many cable TV service providers also offer VoIP-based telephone service via the cable infrastructure (PacketCable). Some high-speed Internet customers may use VoIP telephony by subscribing to a third-party service, such as Vonage, MagicJack+ and NetTALK.

Network architectural functions

[edit]

In network topology, a cable modem is a network bridge that conforms to IEEE 802.1D for Ethernet networking (with some modifications). The cable modem bridges Ethernet frames between a customer LAN and the coax network. Technically, it is a modem because it must modulate data to transmit it over the cable network, and it must demodulate data from the cable network to receive it.

It implements an Ethernet PHY on its LAN interface, and a DOCSIS-defined cable-specific PHY on its HFC cable interface. The term cable modem refers to this cable-specific PHY. The Network Layer is implemented as an IP host in that it has its own IP address used by the network operator to maintain the device. In the transport layer the cable modem supports UDP in association with its own IP address, and it supports filtering based on TCP and UDP port numbers to, for example, block forwarding of NetBIOS traffic out of the customer's LAN. In the Application Layer, the cable modem supports certain protocols that are used for management and maintenance, notably Dynamic Host Configuration Protocol (DHCP), SNMP, and TFTP.

Some cable modems may incorporate a router and a DHCP server to provide the LAN with IP network addressing. From a data forwarding and network topology perspective, this router functionality is typically kept distinct from the cable modem functionality (at least logically) even though the two may share a single enclosure and appear as one unit, sometimes called a residential gateway. So, the cable modem function will have its own IP address and MAC address as will the router.

Cable modem flap

[edit]

Cable modems can have a problem known in industry jargon as "flap" or "flapping".[23] A modem flap is when the connection by the modem to the head-end has been dropped (gone offline) and then comes back online. The time offline or rate of flap is not typically recorded, only the incidence. While this is a common occurrence and usually unnoticed, if a modem's flap is extremely high, these disconnects can cause service to be disrupted. If there are usability problems due to flap the typical cause is a defective modem or very high amounts of traffic on the service provider's network (upstream utilization too high).[24] Types of flap include reinsertions, hits and misses, and power adjustments.[25]

Known vulnerabilities

[edit]

In January 2020, a vulnerability affecting cable modems using Broadcom chipsets was disclosed and named Cable Haunt. Security researchers say that the vulnerability affects hundreds of millions of devices. Exploits are possible because of the use of default credentials in the spectrum analyzer component of the modem (mostly used for debugging purposes) accessible through a network port which is open by default in the vulnerable models.[26][27]

See also

[edit]

References

[edit]
  1. ^ IEN 96 - The MITRE Cablenet Project
  2. ^ "RF Micro Devices, Inc. Whitepaper Describing Historical CATV Components" (PDF). Piedmontscte.org. Retrieved 2016-08-03. Amplifiers are one of the common components used in CATV system
  3. ^ IEEE 802.3b-1985 (10BROAD36) Archived 2012-02-25 at the Wayback Machine - Supplement to 802.3: Broadband Medium Attachment Unit and Broadband Medium Specifications, Type 10BROAD36 (Section 11)
  4. ^ "IEEE SA - 802.7-1989 - Local Area Networks: IEEE Recommended Practice: Broadband Local Area Networks". IEEE. 1990-03-09. Archived from the original on April 15, 2013. Retrieved 2016-08-03.
  5. ^ staff, CNET News. "Bay Networks to acquire LANcity". CNET. Retrieved 2019-09-05.
  6. ^ Marshall, Jonathan; Writer, Chronicle Staff (1998-06-16). "Telecom Giants To Merge / Bay Networks bought by Nortel for $7.2 billion". SFGate. Retrieved 2019-09-05.
  7. ^ "Nortel ups stake in joint venture with Antec". CNET. Retrieved 2019-09-05.
  8. ^ Sallie Hofmeister (1996-08-23). "Americast Places $1-Billion Order for Set-Top Boxes". Los Angeles Times. Retrieved 2010-08-28.
  9. ^ Gilbert Held (2000). Network Design: Principles and Applications. Auerbach Publications. p. 765. ISBN 978-0-8493-0859-8.
  10. ^ "WalkingDog.com". Archived from the original on 1996-12-26. Retrieved 2012-05-13.{{cite web}}: CS1 maint: bot: original URL status unknown (link) The IEEE 802.14 Working Group used WalkingDog.com as its web site.
  11. ^ a b DOCSIS RFI 1.0-I01 (March 26, 1997) Archived May 25, 2011, at the Wayback Machine (See section 6.2.3 for the DOCSIS ATM codepoint. See sections 6.1.2.3, 6.2.5.3, 6.4.7, 9, and 9.2.2 for DOCSIS 1.0 QoS mechanisms.)
  12. ^ "IEEE 802.14 WG Officers". Archived from the original on 1997-01-29. Retrieved 2012-05-13.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  13. ^ Azzam, Albert A. (1997). High speed cable modems : including IEEE 802.14 standards. New York, NY: New York : McGraw-Hill. ISBN 978-0-07-006417-1. Retrieved 7 April 2024.
  14. ^ "Ipcdn Status Pages". Tools.ietf.org. Retrieved 2016-08-03.
  15. ^ "Ipdvb Status Pages". Tools.ietf.org. Retrieved 2016-08-03.
  16. ^ DOCSIS RFI 1.1-I01 (March 11, 1999) (See section 8 and Appendix M.)
  17. ^ "DOCSIS Modem Interoperability and Certification Overview" (PDF). Stuff.mit.edu. Retrieved 2016-08-03.
  18. ^ "Cable". TekSavvy.com. Archived from the original on 2016-08-01. Retrieved 2016-08-03.
  19. ^ "Compatible Modems". vmedia.ca. Retrieved 2021-10-27.
  20. ^ "Unlimited Internet Plans Quebec | Cable, Fibre Optic | Acanac". Acanac.ca. Archived from the original on 2015-05-12. Retrieved 2016-08-03.
  21. ^ "Fast Unlimited Download High Speed Cable 75 Internet Plus Home Phone Bundle". www.worldline.ca. Retrieved 2018-04-23.
  22. ^ KMCreative. "MoCA Access™". www.mocalliance.org. Retrieved 2017-10-03.
  23. ^ "Flap List Troubleshooting for the Cisco CMTS" (PDF). Cisco. Retrieved 26 July 2016.
  24. ^ "Cable modem flapping.. - RCN | DSLReports Forums". Dslreports.com. Retrieved 2016-08-03.
  25. ^ "CMTS Troubleshooting and Network Management Features Configuration Guide". Cisco.com. 2016-01-27. Retrieved 2016-08-03.
  26. ^ "Hundreds of millions of cable modems are vulnerable to new Cable Haunt vulnerability". ZDNet.
  27. ^ Goodin, Dan (2020-01-13). "Exploit that gives remote access affects ~200 million cable modems". Ars Technica. Retrieved 2020-01-15.

Further reading

[edit]
[edit]
Wikimedia Commons has media related to Cable modems.
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Cable_modem&oldid=1258844990"