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Wikipedia

Cable modem

May 04, 2023

A cable modem is a type of network bridge that provides bi-directional data communication via radio frequency channels 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 of a HFC and RFoG network. They are commonly deployed in the Americas, Asia, Australia, and Europe.

ARRIS Touchstone CM820B DOCSIS 3.0 cable modem

History

MITRE Cablenet

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)

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

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

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 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

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

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 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 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

CDLP was a proprietary system manufactured by Motorola. CDLP customer premises equipment (CPE) was capable of both PSTN (telephone network) and 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 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

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

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

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

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 supports best efforts service, the DOCSIS RFI 1.0 Interim-01 document discussed 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 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 MHz for the USA 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

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

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

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.

With respect to the OSI model of network design, a cable modem is both physical layer (layer 1) device and a data link layer (layer 2) forwarder. As an IP addressable network node, cable modems support functionality at other layers.

Layer 1 is implemented in the 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 (Layer 3) 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 (layer 4) 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 (Layer 7), 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

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

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

References

  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) - 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". Standards.ieee.org. 1990-03-09. 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. ^ . 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) 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. ^ . Archived from the original on 1997-01-29. Retrieved 2012-05-13.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  13. ^ Albert A. Azzam, High-Speed Cable Modems ISBN 978-0-07-006417-1
  14. ^ "Ipcdn Status Pages". Tools.ietf.org. Retrieved 2016-08-03.
  15. ^ "Ipdvb Status Pages". Tools.ietf.org. Retrieved 2016-08-03.
  16. ^ (See section 8 and Appendix M.)
  17. ^ "DOCSIS Modem Interoperability and Certification Overview" (PDF). Stuff.mit.edu. Retrieved 2016-08-03.
  18. ^ . TekSavvy.com. Archived from the original on 2016-08-01. Retrieved 2016-08-03.
  19. ^ "Compatible Modems". vmedia.ca. Retrieved 2021-10-27.
  20. ^ . 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

  • Curt Franklin. "How Cable Modems Work". HowStuffWorks. Retrieved 2010-08-28.
  • Andrew Brandt (1999). . PC World. Archived from the original on 2011-11-03. Retrieved 2010-08-28.

External links

 
Wikimedia Commons has media related to Cable modems.

May 04, 2023
cable, modem, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, august, 2010,. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Cable modem news newspapers books scholar JSTOR August 2010 Learn how and when to remove this template message A cable modem is a type of network bridge that provides bi directional data communication via radio frequency channels 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 of a HFC and RFoG network They are commonly deployed in the Americas Asia Australia and Europe ARRIS Touchstone CM820B DOCSIS 3 0 cable modem Contents 1 History 1 1 MITRE Cablenet 1 2 IEEE 802 3b 10BROAD36 1 3 IEEE 802 7 1 4 Hybrid networks 1 5 LANcity 1 6 Zenith homeworks 1 7 Com21 1 8 CDLP 1 9 DVB DAVIC 1 10 IEEE 802 14 1 11 IETF 1 12 DOCSIS 1 13 Multimedia over Coax Alliance 2 Multimedia terminal adapter 3 Network architectural functions 4 Cable modem flap 5 Known vulnerabilities 6 See also 7 References 8 Further reading 9 External linksHistory EditMITRE 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 SystemThe 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 Quebec 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 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 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 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 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 supports best efforts service the DOCSIS RFI 1 0 Interim 01 document discussed 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 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 MHz for the USA 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 AllianceIn 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 EditWith 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 EditIn 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 With respect to the OSI model of network design a cable modem is both physical layer layer 1 device and a data link layer layer 2 forwarder As an IP addressable network node cable modems support functionality at other layers Layer 1 is implemented in the 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 Layer 3 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 layer 4 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 Layer 7 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 EditCable 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 EditIn 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 EditCable modem termination system CMTS Cable telephone Internet access with a cable modem List of device bandwidths Triple play telecommunications HomePNAReferences Edit IEN 96 The MITRE Cablenet Project 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 IEEE 802 3b 1985 10BROAD36 Supplement to 802 3 Broadband Medium Attachment Unit and Broadband Medium Specifications Type 10BROAD36 Section 11 IEEE SA 802 7 1989 Local Area Networks IEEE Recommended Practice Broadband Local Area Networks Standards ieee org 1990 03 09 Retrieved 2016 08 03 staff CNET News Bay Networks to acquire LANcity CNET Retrieved 2019 09 05 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 Nortel ups stake in joint venture with Antec CNET Retrieved 2019 09 05 Sallie Hofmeister 1996 08 23 Americast Places 1 Billion Order for Set Top Boxes Los Angeles Times Retrieved 2010 08 28 Gilbert Held 2000 Network Design Principles and Applications Auerbach Publications p 765 ISBN 978 0 8493 0859 8 WalkingDog com Archived from the original on 1996 12 26 Retrieved 2012 05 13 a href Template Cite web html title Template Cite web cite web a CS1 maint bot original URL status unknown link The IEEE 802 14 Working Group used WalkingDog com as its web site 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 IEEE 802 14 WG Officers Archived from the original on 1997 01 29 Retrieved 2012 05 13 a href Template Cite web html title Template Cite web cite web a CS1 maint bot original URL status unknown link Albert A Azzam High Speed Cable Modems ISBN 978 0 07 006417 1 Ipcdn Status Pages Tools ietf org Retrieved 2016 08 03 Ipdvb Status Pages Tools ietf org Retrieved 2016 08 03 DOCSIS RFI 1 1 I01 March 11 1999 See section 8 and Appendix M DOCSIS Modem Interoperability and Certification Overview PDF Stuff mit edu Retrieved 2016 08 03 Cable TekSavvy com Archived from the original on 2016 08 01 Retrieved 2016 08 03 Compatible Modems vmedia ca Retrieved 2021 10 27 Unlimited Internet Plans Quebec Cable Fibre Optic Acanac Acanac ca Archived from the original on 2015 05 12 Retrieved 2016 08 03 Fast Unlimited Download High Speed Cable 75 Internet Plus Home Phone Bundle www worldline ca Retrieved 2018 04 23 KMCreative MoCA Access www mocalliance org Retrieved 2017 10 03 Flap List Troubleshooting for the Cisco CMTS PDF Cisco Retrieved 26 July 2016 Cable modem flapping RCN DSLReports Forums Dslreports com Retrieved 2016 08 03 CMTS Troubleshooting and Network Management Features Configuration Guide Cisco com 2016 01 27 Retrieved 2016 08 03 Hundreds of millions of cable modems are vulnerable to new Cable Haunt vulnerability Zdnet Goodin Dan 2020 01 13 Exploit that gives remote access affects 200 million cable modems Ars Technica Retrieved 2020 01 15 Further reading EditCurt Franklin How Cable Modems Work HowStuffWorks Retrieved 2010 08 28 Andrew Brandt 1999 How It Works Cable Modems PC World Archived from the original on 2011 11 03 Retrieved 2010 08 28 External links Edit Wikimedia Commons has media related to Cable modems Cable modem at Curlie Retrieved from https en wikipedia org w index php title Cable modem amp oldid 1148186265, wikipedia, wiki, book, books, library,

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