 |
DOCSIS Set-top Gateway (or DSG) is a specification describing how out-of-band data is delivered to a cable set-top box. Cable set-top boxes need a reliable source of out of band data for information such as program guides, channel lineups, and updated code images.
DSG is an extension of the DOCSIS protocol governing cable modems, and applies to all versions of DOCSIS.
The principal features of DSG are:
The original DOCSIS protocol supports only two way connectivity. A cable modem that is unable to acquire an upstream channel will give up and resume scanning for new channels. Likewise, persistent upstream errors will cause a cable modem to "reinitialize its MAC" and scan for new downstream channels. This behavior is appropriate for traditional cable modems, but not for cable set-top boxes. A cable set-top box still needs to acquire its out of band data even if the upstream channel is impaired.
The DSG specification introduced one way (downstream only) modes of operation. When upstream errors occur, the set-top enters a downstream-only state, periodically attempting to reacquire the upstream channel.
Set-top out of band data is generally present only on certain downstream channels. The set-top needs a way to distinguish a valid downstream (containing the set-top's data) from an invalid one used only by standalone cable modems.
The DSG specification defines a special downstream keep-alive message so that the set-top can recognize an appropriate downstream channel.
The Advanced Mode of the DSG Specification introduces a special MAC Management message called the Downstream Channel Descriptor (DCD). The DCD provides a directory identifying the MAC and IP parameters associated with the out of band data streams.
Each data consumer is assigned a special Client Identifier that names the out of band data stream in the DCD.
The DSG Specification creates two new SNMP management information bases (MIBs) to manage DSG devices. One MIB is used by the set-top, the other by the cable modem termination system (CMTS).
A DSG network comprises three components. The Conditional Access Server generates a stream of out of band data. The DSG Agent (the CMTS) forwards the out of band data and publishes the out of band directory (the DCD). The DSG client on the set-top digests the DSG data.
The set-top device comprises three subcomponents. The DSG-capable cable modem is referred to as the DSG eCM (Embedded Cable Modem). A data consumer is called a DSG Client (there are generally many of these.) Finally, the eCM is configured and controlled by a component called the DSG Client Controller.
Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broadcast television, in which the television signal is transmitted over-the-air by radio waves and received by a television antenna attached to the television; or satellite television, in which the television signal is transmitted over-the-air by radio waves from a communications satellite orbiting the Earth, and received by a satellite dish antenna on the roof. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation.
Digital subscriber line is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access.
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.
Multichannel multipoint distribution service (MMDS), formerly known as broadband radio service (BRS) and also known as wireless cable, is a wireless telecommunications technology, used for general-purpose broadband networking or, more commonly, as an alternative method of cable television programming reception.
A digital subscriber line access multiplexer is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques. Its cable internet (DOCSIS) counterpart is the cable modem termination system.
Data Over Cable Service Interface Specification (DOCSIS) is an international telecommunications standard that permits the addition of high-bandwidth data transfer to an existing cable television (CATV) system. It is used by many cable television operators to provide cable Internet access over their existing hybrid fiber-coaxial (HFC) infrastructure.
Hybrid fiber-coaxial (HFC) is a broadband telecommunications network that combines optical fiber and coaxial cable. It has been commonly employed globally by cable television operators since the early 1990s.
A cable modem termination system is a piece of equipment, typically located in a cable company's headend or hubsite, which is used to provide high speed data services, such as cable Internet or Voice over Internet Protocol, to cable subscribers. A CMTS provides many of the same functions provided by the DSLAM in a DSL system.
A passive optical network (PON) is a fiber-optic telecommunications technology for delivering broadband network access to end-customers. Its architecture implements a point-to-multipoint topology in which a single optical fiber serves multiple endpoints by using unpowered (passive) fiber optic splitters to divide the fiber bandwidth among the endpoints. Passive optical networks are often referred to as the last mile between an Internet service provider (ISP) and its customers. Many fiber ISPs prefer this technology.
In computer networking, link aggregation is the combining of multiple network connections in parallel by any of several methods. Link aggregation increases total throughput beyond what a single connection could sustain, and provides redundancy where all but one of the physical links may fail without losing connectivity. A link aggregation group (LAG) is the combined collection of physical ports.
A digital subscriber line (DSL) modem is a device used to connect a computer or router to a telephone line which provides the digital subscriber line (DSL) service for connection to the Internet, which is often called DSL broadband. The modem connects to a single computer or router, through an Ethernet port, USB port, or is installed in a computer PCI slot.
In telecommunications, cable Internet access, shortened to cable Internet, is a form of broadband internet access which uses the same infrastructure as cable television. Like digital subscriber line and fiber to the premises services, cable Internet access provides network edge connectivity from the Internet service provider to an end user. It is integrated into the cable television infrastructure analogously to DSL which uses the existing telephone network. Cable TV networks and telecommunications networks are the two predominant forms of residential Internet access. Recently, both have seen increased competition from fiber deployments, wireless, mobile networks and satellite internet access.
In computer networking, out-of-band data is the data transferred through a stream that is independent from the main in-band data stream. An out-of-band data mechanism provides a conceptually independent channel, which allows any data sent via that mechanism to be kept separate from in-band data. The out-of-band data mechanism should be provided as an inherent characteristic of the data channel and transmission protocol, rather than requiring a separate channel and endpoints to be established. The term "out-of-band data" probably derives from out-of-band signaling, as used in the telecommunications industry.
The Multimedia over Coax Alliance (MoCA) is an international standards consortium that publishes specifications for networking over coaxial cable. The technology was originally developed to distribute IP television in homes using existing cabling, but is now used as a general-purpose Ethernet link where it is inconvenient or undesirable to replace existing coaxial cable with optical fiber or twisted pair cabling.
YouSee is the largest quadruple play service provider in Denmark, and is a part of Nuuday which is a spun-off company from TDC Group, the largest telecommunications company in Denmark which was split into two separate companies. YouSee currently has 994,000 customers, down from its peak of 1.4 million in 2015.
Zenith Cable Modem was one of the first proprietary cable modems. The two basic models are one operating at 500 kilobits per second (kbit/s), and the other at four megabits per second (mbit/s) with BPSK and approximately a 25% alpha.
In telecommunications, radio frequency over glass (RFoG) is a deep-fiber network design in which the coax portion of the hybrid fiber coax (HFC) network is replaced by a single-fiber passive optical network (PON). Downstream and return-path transmission use different wavelengths to share the same fiber. The return-path wavelength standard is expected to be 1610 nm, but early deployments have used 1590 nm. Using 1590/1610 nm for the return path allows the fiber infrastructure to support both RFoG and a standards-based PON simultaneously, operating with 1490 nm downstream and 1310 nm return-path wavelengths.
Com21 was an early pioneer in developing cable modem networks in the era before the standard DOCSIS was introduced for Internet access via cable television networks. The company filed for bankruptcy in 2003.
Subisu Cablenet Ltd. is a Nepalese Internet Service Provider company located in Kathmandu, Nepal, and was established in 2001. Subisu employs over 1500 full-time employees, of which around 900 are technical and around 700 are non-technical. As of 2023, the company has over 235,000 customers. It has coverage in all 77 districts of Nepal. Subisu primarily provides cable & fiber internet and Digital TV services through a hybrid fiber-coaxial (HFCC) network. The Internet and 280+ TV channels that it offers provides support to Nepal's educational, entertainment, professional and other sectors. It is the first and the only cable internet service provider in Nepal.