A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information Cable modems are primarily used to deliver broadband Internet access in the form of cable internet, taking advantage of unused bandwidth on a cable television network. Broadband Internet access, often shortened to just Broadband, is high-speed Internet access—typically contrasted with dial-up access over a Modem In Telecommunications cable Internet is a form of Broadband Internet access that uses the Cable television infrastructure They are commonly found in Australia, New Zealand, Canada, Europe, the United Kingdom, Costa Rica, and the United States. For a topic outline on this subject see List of basic Australia topics. New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Costa Rica, officially the Republic of Costa Rica ( Spanish: Costa Rica or República de Costa Rica,) is a Country in The United States of America —commonly referred to as the In the USA alone there were 22. 5 million cable modem users during the first quarter of 2005, up from 17. 4 million in the first quarter of 2004. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again "
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Cable modems in the OSI model or TCP/IP model
In network topology, a cable modem is a network bridge that conforms to IEEE 802.1D for Ethernet networking (with some modifications). The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol The TCP/IP model is a specification for computer network protocols created in the 1970s by DARPA, an agency of the United States Department of Defense. A network bridge connects multiple Network segments at the Data link layer (layer 2 of the OSI model, and the term layer 2 switch is often 8021D is the IEEE MAC Bridges standard which includes Bridging, Spanning Tree, interworking for 802 Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs The cable modem bridges Ethernet frames between a customer LAN and the coax cable network.
With respect to the OSI model, a cable modem is a data link layer (or layer 2) forwarder, rather than simply a modem. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol The Data Link Layer is Layer 2 of the seven-layer OSI model. It responds to service requests from the Network Layer and issues service requests to the Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information
A cable modem does support functionalities at other layers. In physical layer (or layer 1), the cable modem supports the Ethernet PHY on its LAN interface, and a DOCSIS defined cable-specific PHY on its HFC cable interface. The Physical Layer is the first level in the seven-layer OSI model of computer networking. There are a few standards for Ethernet over twisted pair or Copper -based computer networking physical connectivity methods In Telecommunications and Computer networking, a network interface is one of The point of Interconnection between a user terminal Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS Hybrid fibre-coaxial ( HFC) is a Telecommunications industry term for a broadband network which combines Optical fiber and Coaxial cable It is to this cable-specific PHY that the name cable modem refers. In the network layer (or layer 3), the cable modem is a IP host in that it has its own IP address used by the network operator to manage and troubleshoot the device. The Network Layer is Layer 3 (of seven in the OSI model of networking The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network In the transport layer (or 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 Computer networking, the Transport Layer is a group of methods and protocols within a layered architecture of network components within which it is responsible for encapsulating User Datagram Protocol ( UDP) is one of the core protocols of the Internet Protocol Suite. In Computer networking, a port is an application-specific or process-specific software construct serving as a communications endpoint used by Transport Layer protocols NetBIOS ( is an acronym for Network Basic Input/Output System. In the application layer (layer 5 or layer 7), the cable modem supports certain protocols that are used for management and maintenance, notably DHCP, SNMP, and TFTP. The Application Layer is the seventh level of the seven-layer OSI model, and the top layer of the TCP/IP model Simple Network Management Protocol ( SNMP) forms part of the Internet protocol suite as defined by the Internet Engineering Task Force (IETF Trivial File Transport Protocol ( TFTP) is a very simple file transfer protocol, with the functionality of a very basic form of FTP; it was
Some cable modem devices may incorporate a router along with the cable modem functionality, to provide the LAN with its own IP network addressing. A router ('rautər in the USA 'rutər in the UK and Ireland, or either pronunciation in Australia and Canada is a Computer whose software and hardware are usually The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol 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. So, the cable modem function will have its own IP address and MAC address as will the router. An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network In Computer networking a Media Access Control address ( MAC address) or Ethernet Hardware Address ( EHA) hardware address
History
Hybrid Networks
Hybrid Networks developed, demonstrated and patented the first high speed, asymmetrical cable modem systems in 1990. A key Hybrid Networks insight was that highly asymmetrical communications would be sufficient to satisfy consumers connected remotely to an otherwise completely symmetric high speed data communications network. This was important because it was very expensive to provide high speed in the upstream direction, while the CATV systems already had substantial broadband capacity in the downstream direction. 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 cable for the upstream as well as the downstream path.
There was extreme skepticism to this approach initially. In fact, many technical people doubted that it could work at all. Hybrid's system architecture is the way most cable modem systems operate today.
LANcity
LANcity was an early pioneer in cable modems, developing a proprietary system that saw fairly wide deployment in the US. LANcity was sold to Bay Networks which was then acquired by Nortel, which eventually spun the cable modem business off as ARRIS. Bay Networks was a network hardware vendor formed through the merger of Santa Clara California based SynOptics Communications and Billerica Massachusetts Nortel Networks Corporation () formerly known as Northern Telecom Limited and sometimes known simply as Nortel, is a multinational Telecommunications Arris is an architectural term that describes the sharp edge formed by the intersection of two surfaces such as the corner of a masonry unit; the junction between ARRIS continues to make cable modems and CMTS equipment compliant with the DOCSIS standard. Arris is an architectural term that describes the sharp edge formed by the intersection of two surfaces such as the corner of a masonry unit; the junction between A cable modem termination system or CMTS is equipment typically found in a cable company's headend, or at cable company hubsite and is used to provide high Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS
Com21
Com21 was another early pioneer in cable modems, and quite successful until proprietary systems became obsolete when DOCSIS became the widely accepted standard. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS 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. HP OpenView was a Hewlett Packard product range consisting of network and Systems management products [1] 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 the ATM protocol. In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells 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 Fastethernet and ATM interfaces. The ATM interface became the most popular as it supported the increasing bandwidth demands and also supported VLAN's. In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells A virtual LAN, commonly known as a VLAN, is a group of hosts with a common set of requirements that communicate as if they were attached to the Broadcast domain Com21 developed a DOCSIS modem, but didn't survive and filed bankruptcy in 2003.
CDLP
CDLP was a proprietary system that was made by Motorola. A cable modem is a type of Modem that provides access to a data signal sent over the Cable television infrastructure Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. CDLP CPE was capable of both PSTN (telephone network) and RF (cable network) return paths. Customer-premises equipment or customer-provided equipment ( CPE) is any terminal and associated Equipment located at a Subscriber The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the This article is about the type of television channel For cable television infrastructure i The PSTN return path cable modem service was considered 'one way cable' and had many of the same drawbacks as satellite Internet service, and as a result it quickly gave way to two way cable. Satellite Internet services are used in locations where terrestrial Internet access is not available and in locations which move frequently Cable modems that used the RF cable network for the return path were considered 'two way cable', and were better able to compete with DSL which was bidirectional. The standard is more or less defunct now with new providers using, and existing providers having changed over to, the DOCSIS standard. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS The Motorola CDLP Proprietary CyberSURFR is an example of a modem that was built to the CDLP standard, capable of a peak 10 Mbit/s downstream and 1. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission 532 Mbit/s upstream. (CDLP supported a maximum downstream bandwidth of 30 Mbit/s which could be reached by using several modems. )
The Australian ISP BigPond employed this system when it started cable modem trials in 1996. For a topic outline on this subject see List of basic Australia topics. BigPond is an Australian Internet service provider and is a Subsidiary of Telstra. For a number of years cable Internet access was only available to Sydney, Melbourne and Brisbane via CDLP. Sydney (ˈsɪdniː is the most populous city in Australia, with a Metropolitan area population of approximately 4 Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 Brisbane ( is the state capital of Queensland. Brisbane is the third most populous city in Australia and the most populous city of Queensland This network ran parallel to the newer DOCSIS system for a number of years. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS In 2004 the CDLP network was switched off and now is exclusively DOCSIS. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS
IEEE 802. 14
In the mid-1990s the IEEE 802 committee formed a subcommittee (802. IEEE 802 refers to a family of IEEE standards dealing with Local area networks and Metropolitan area networks More specifically the IEEE 802 standards are 14) to develop a standard for cable modem systems. While significant progress was made, the group was disbanded when North American MSOs instead backed the fledgling DOCSIS specification. A multiple system operator (MSO is an operator of multiple Cable television systems Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS
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. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS 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. The Physical Layer is the first level in the seven-layer OSI model of computer networking. Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. A cable modem is a type of Modem that provides access to a data signal sent over the Cable television infrastructure The Media Access Control (MAC Data communication protocol sub-layer also known as the Medium Access Control is a sublayer of the Data Link Layer specified in the When the initial specification had been drafted, the MCNS consortium handed over control of it to CableLabs. Cable Television Laboratories, also called CableLabs, is a non-profit Research and development consortium whose members are exclusively Cable television CableLabs took on maintenance of 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. The Society of Cable Telecommunications Engineers or SCTE is a Non-profit Professional association for the advancement of technology related to cable telecommunications Virtually all cable modems operating in the field today are compliant with one version or another of DOCSIS. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS Because of the differences in the European PAL and USA's NTSC systems two main versions of DOCSIS exist: DOCSIS and EuroDOCSIS. PAL, short for Phase Alternating Line, is a colour -encoding system used in Broadcast television systems in large parts of the world NTSC ( National Television System Committee) is the Analog television system used in the United States, Canada, Japan, Mexico Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS The main differences are found in the width of RF-channels: 6 Mhz for the USA and 8 Mhz for Europe. Japan uses their own version of DOCSIS. For a topic outline on this subject see List of basic Japan topics. Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS Nearly all current cablemodem systems use a version of this standard.
Cable modems and VoIP
With the advent of Voice over IP telephony, cable modems can also be used to provide telephone service. Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet Many people who have cable modems have opted to eliminate their Plain Old Telephone Service (POTS). Because most telephone companies do not offer naked DSL (DSL service without a POTS line), VoIP use is higher amongst cable modem users. A naked DSL (aka standalone or dryloop DSL) is a Digital subscriber line (DSL without a PSTN ( analogue Telephony) service &mdash Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet
A cable modem subscriber can make use of VoIP telephony by subscribing to a third party service (e. Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet g. Vonage or Skype). Vonage ( (ˈvɑːnɪdʒ is a publicly-held commercial Voice over IP (VoIP network and SIP company that provides Telephone service Skype (skaɪp is Software that allows users to make telephone calls over the Internet. As an alternative, many cable operators offer a VoIP service based on PacketCable. PacketCable is a project started by CableLabs.The purpose of the organization is to define standards for the Cable TV industry PacketCable allows MSOs to offer both High Speed Internet and VoIP through a single piece of customer premise equipment, known as an Embedded Multimedia Terminal Adapter (EMTA or E-MTA). A multiple system operator (MSO is an operator of multiple Cable television systems An EMTA is basically a cable modem and a VoIP adapter (known as a Multimedia Terminal Adapter) bundled into a single device. PacketCable service has a significant technical advantage over third-party providers in that voice packets are given guaranteed Quality of Service across their entire path so that call quality can be assured.
To attain a higher quality VoIP telephone line, cable modem users often will take advantage of the two IP addresses that many ISPs provide. An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network An Internet service provider ( ISP, also called Internet access provider or IAP) is a company which primarily offers their customers access to the Internet This type of setup allows the PCs to access the internet under one IP address while the VoIP gateway has its own IP address. This is advantageous to many VoIP users as it creates a network where their PC network activity doesn't affect their call quality. To achieve this setup, a switch/hub is placed downline of the modem. Doing so will assign two IP addresses (one to the computer network i. e. router and one to the voice gateway).
See also
- Cable internet
- DOCSIS
- Residential gateway
- Cable modem termination system
- Hybrid Fibre Coaxial
- List of device bandwidths
- Triple play (telecommunications)
Cable modem manufacturers
External links
General information
- Cable Modem Information Network
- Cable modem
- DOCSIS standard
- The Cable Modem Reference Guide
- VelocityGuide Cable Modem Information
References via external links
- ^ Details ComUNITY productline via (Google cache of): Com21 SEC filing on 4 feb 1999, detailing products. In Telecommunications cable Internet is a form of Broadband Internet access that uses the Cable television infrastructure Data Over Cable Service Interface Specification ( DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS This article is about the types of network routers and modems found in many homes known colloquially as "residential gateways" A cable modem termination system or CMTS is equipment typically found in a cable company's headend, or at cable company hubsite and is used to provide high Hybrid fibre-coaxial ( HFC) is a Telecommunications industry term for a broadband network which combines Optical fiber and Coaxial cable This is a list of device bandwidths: the Net bit rate (or more informally Digital bandwidth) of some computer devices employing methods of data transport is quantified In Telecommunications the triple play service is a marketing term for the provisioning of the two broadband services high-speed Internet access and television and Ambit Broadband are a Taiwanese supplier of broadband Internet equipment including Cable modems ADSL modems VoIP IPTV etc Arris is an architectural term that describes the sharp edge formed by the intersection of two surfaces such as the corner of a masonry unit; the junction between D-Link Corporation was founded in 1986 in Taipei as Datex Systems Inc Ericsson ( Telefonaktiebolaget L M Ericsson) () one of the largest Swedish companies is a leading provider of telecommunication and data communication systems Linksys, founded in 1988 and acquired by Cisco Systems in 2003, is the leader in sales of home and small office network products Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. Nortel Networks Corporation () formerly known as Northern Telecom Limited and sometimes known simply as Nortel, is a multinational Telecommunications Netgear, founded in 1996 is a US manufacturer of Computer networking equipment and other Computer hardware. Koninklijke Philips Electronics NV ( Royal Philips Electronics Inc. RCA Corporation, founded as Radio Corporation of America, was an electronics company in existence from 1919 to 1986 Scientific Atlanta Inc, a Cisco company is a Georgia -based manufacturer of Cable television, Telecommunications, and Broadband Terayon Communication Systems Inc is a company that vends equipment to Broadband service providers for delivering broadband voice video and data services to Thomson SA (,) formerly known as Thomson Multimedia is an international provider of solutions for the creation management delivery and access of video for the ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. Zoom Technologies Inc designs and produces Voice over IP gateways DSL modems Cable modems Dial-up Modems Bluetooth Huawei Technologies Co Ltd ( in Shenzhen, Guangdong, People's Republic of China is the largest networking and telecommunications equipment supplier ZyXEL Communications Corp ( Chinese:zh 合勤科技 TSE 2391 located in Hsinchu, Taiwan, is a manufacturer of DSL and other networking devices
Dictionary
cable modem
-noun
- (Internet) A modem that connects a personal computer to a fibreoptic cable, typically one used by a digital television system to provide broadband access
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