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Encyclopedia > DOCSIS

Data Over Cable Service Interface Specification (DOCSIS) is an international standard developed by CableLabs and contributing companies that include: ARRIS, BigBand Networks, Broadcom, Cisco, Conexant, Correlant, Intel, Motorola, Netgear, Terayon, and Texas Instruments. DOCSIS defines the communications and operation support interface requirements for a data over cable system. It permits the addition of high-speed data transfer to an existing Cable TV (CATV) system. It is employed by many cable television operators to provide Internet access (see cable internet) over their existing hybrid fibre coaxial (HFC) infrastructure. The first DOCSIS specification was version 1.0, issued in March of 1997, with revision 1.1 (adding Quality of Service (QoS) capabilities) following in April of 1999. Because of increased demand for symmetric services such as IP telephony, DOCSIS was revised to enhance upstream transmission speeds; DOCSIS 2.0 was released in December 2001. Most recently, the specification was revised to significantly increase transmissions speeds (this time both upstream and downstream) and introduce support for Internet Protocol version 6 (IPv6). This version, DOCSIS 3.0, was released in August 2006. Cross-version compatibility has been maintained across all versions of DOCSIS, with the devices falling back to the highest supported version in common between both endpoints (cable modem and cable modem termination system). Cable Television Laboratories, Inc. ... An arris is an architectural term that describes the intersection between two outside planes such as the corner of a masonry unit or the intersection of divergent architectural details. ... BigBand Networks (known as BigBand ; NASDAQ: BBND) is a multinational corporation headquartered in Redwood City, California, United States. ... Broadcom Corporation is a leading American supplier of integrated circuits (ICs) for broadband communications. ... Cisco may refer to: Cisco Systems, a computer networking company Cisco IOS, an internet router operating system CISCO Security Private Limited, a security company in Singapore Commercial and Industrial Security Corporation, a statutory board in Singapore Abbreviation for San Francisco, California Cisco (wine) The Cisco Kid, a fictional character created... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Motorola Inc. ... NETGEAR, founded in 1996, is a manufacturer of computer networking equipment and other computer hardware. ... Terayon Communication Systems, Inc. ... Texas Instruments (NYSE: TXN), better known in the electronics industry (and popularly) as TI, is an American company based in Dallas, Texas, USA, renowned for developing and commercializing semiconductor and computer technology. ... Cable television or Community Antenna Television (CATV) (and often shortened to cable) is a system of providing television, FM radio programming and other services to consumers via radio waves transmitted directly to people’s televisions through fixed coaxial cables as opposed to the over-the-air method used in traditional... // The term cable Internet access or Cable Internet refers to the delivery of Internet service over this infrastructure. ... Hybrid fiber-coaxial (HFC) is a telecommunications industry term for a network which incorporates both optical fiber along with coaxial cable to create a broadband network. ... In the fields of packet-switched networks and computer networking, the traffic engineering term Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. ... Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. ... An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ...


As frequency allocation band plans differ between U.S. and European CATV systems, DOCSIS standards have been modified for use in Europe. These changes were published under the name of "EuroDOCSIS". The main differences account for differing TV channel bandwidths; European cable channels conform to PAL TV standards and are 8 MHz wide, whereas in North-America cable channels conform to NTSC standards which specify 6 MHz. The wider bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user). EuroDOCSIS certification testing is executed by Excentis (formerly known as tComLabs), while DOCSIS certification testing is executed by CableLabs. Typically, CPE gear receives "Certification", while CMTS equipment receives "Qualification". For other uses, see PAL (disambiguation). ... NTSC is the analog television system in use in the United States, Canada, Japan, Mexico, the Philippines, South Korea, Taiwan, and some other countries (see map). ... Customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment and inside wiring located at a subscribers premises and connected with a carriers telecommunication channel(s) at the demarcation point (demarc). The demarc is a point established in a building or complex to separate... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ...


Japan employs other variants of DOCSIS.

Contents

International Standards

The International Telecommunications Union Telecommunications Standardization Sector (ITU-T) has approved the various versions of DOCSIS as international standards. DOCSIS 1.0 was ratified as ITU-T Recommendation J.112 Annex B (1998), but it was superseded by DOCSIS 1.1 which was ratified as ITU-T Recommendation J.112 Annex B (2001). Subsequently, DOCSIS 2.0 was ratified as ITU-T Recommendation J.122. Most recently, DOCSIS 3.0 was ratified as ITU-T Recommendation J.222 (J.222.1J.222.2J.222.3). The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ...


Note: While ITU-T Recommendation J.112 Annex B corresponds to DOCSIS/EuroDOCSIS 1.1, Annex A describes an earlier European cable modem system ("DVB EuroModem") based on ATM transmission standards. Annex C describes a variant of DOCSIS 1.1 that is designed to operate in Japanese cable systems. The ITU-T Recommendation J.122 main body corresponds to DOCSIS 2.0, J.122 Annex F corresponds to EuroDOCSIS 2.0, and J.122 Annex J describes the Japanese variant of DOCSIS 2.0 (analogous to Annex C of J.112). DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 300 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC...


Features

DOCSIS provides great variety in options available at Open Systems Interconnection (OSI) layers 1 and 2, the Physical (PHY) and Media Access Control (MAC) layers. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design. ... This article does not cite any references or sources. ... The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ...

Physical layer
  • Channel Width: DOCSIS 1.0/1.1 specified channel widths between 200 kHz and 3.2 MHz. DOCSIS 2.0 specifies 6.4 MHz, but is backward compatible to the earlier, narrower channel widths.
  • Modulation: DOCSIS 1.0/1.1/2.0 specifies that 64-level or 256-level QAM (64-QAM or 256-QAM) be used for modulation of downstream data, and QPSK or 16-level QAM (16-QAM) be used for upstream modulation. DOCSIS 2.0 specifies 32-QAM, 64-QAM and 128-QAM also be available for upstream use.
MAC layer
DOCSIS employs a mixture of deterministic access methods, specifically TDMA for DOCSIS 1.0/1.1 and both TDMA and S-CDMA for DOCSIS 2.0, with a limited use of contention for bandwidth requests. In contrast to the pure contention-based MAC CSMA/CD employed in Ethernet systems, DOCSIS systems experience few collisions. For DOCSIS 1.1 and above the MAC layer also includes extensive Quality of Service (QoS) features that help to efficiently support applications, for example Voice over IP, that have specific traffic requirements, such as low latency.
Throughput
All of these features combined enable a total upstream throughput of 30.72 Mbit/s per channel (although the upstream speed in DOCSIS 1.0 and 1.1 is limited to 10.24 Mbit/s). All three versions of the DOCSIS standard support a downstream throughput of up to 42.88 Mbit/s per channel with 256-QAM (owing to 8 MHz channel width, the EuroDOCSIS standard supports downstream throughput of up to 55.62 Mbit/s per channel).

DOCSIS 3.0 features management over IPv6 and channel bonding, which enables multiple downstream and upstream channels to be used together at the same time by a single subscriber. [1] This article does not cite any references or sources. ... “QAM” redirects here. ... Quadrature phase-shift keying (quadriphase, quaternary phase-shift keying) is a form of modulation in which a carrier is sent in four phases, 45, 135, 225, and 315 degrees, and the change in phase from one symbol to the next encodes two bits per symbol. ... The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ... Time division multiple access (TDMA) is a channel access method for shared medium (usually radio) networks. ... Time division multiple access (TDMA) is a channel access method for shared medium (usually radio) networks. ... Synchronous Code Division Multiple Access is a multiplex method based on spread-spectrum CDMA. See also: TD-SCDMA. Categories: Multiplexing stubs ... In computer networking, Carrier Sense Multiple Access With Collision Detection (CSMA/CD) is a network control protocol in which (a) a carrier sensing scheme is used and (b) a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame, transmits a jam signal, and then... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... In the fields of packet-switched networks and computer networking, the traffic engineering term Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. ... An overview of how VoIP works A typical analog telephone adapter for connecting an ordinary phone to a VoIP network Ciscos implementation of VoIP - IP Phone Voice over Internet Protocol, also called VoIP (pronounced voyp), IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the... A megabit per second (mbps or mbit/s) is a unit of data transmission equal to 1,000 kilobits per second or 1,000,000 bits per second. ... Internet Protocol version 6 (IPv6) is a network layer for packet-switched internetworks. ... Channel bonding in computer networking is an arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput. ...


The new 'DOCSIS 2.0 + IPv6' standard also supports IPv6, which may on the cable modem side only require a firmware upgrade [2] [3]


Speed Table

Maximum synchronization speed (Maximum usable speed)

Version DOCSIS EuroDOCSIS
Downstream Upstream Downstream Upstream
1.x 42.88 (38) Mbit/s 10.24 (9) Mbit/s 55.62 (50) Mbit/s 10.24 (9) Mbit/s
2.0 42.88 (38) Mbit/s 30.72 (27) Mbit/s 55.62 (50) Mbit/s 30.72 (27) Mbit/s
3.0 4channel +171.52 (+152) Mbit/s +122.88 (+108) Mbit/s +222.48 (+200) Mbit/s +122.88 (+108) Mbit/s
3.0 8channel +343.04 (+304) Mbit/s +122.88 (+108) Mbit/s +444.96 (+400) Mbit/s +122.88 (+108) Mbit/s
  • Note: NTSC 6MHZ channel spacing will allow 10 bonded 6MHz channels as MAX spectrum allocation for DOCSIS3.0 data, 60MHz spectrum allocation could increase with consumer needs and re-allocation of analog TV channels into compressed digital space, leveraging the capability of DOCSIS 3.0 infrastructure to allow for 1Gbps speeds in the future

Equipment

A DOCSIS architecture includes two primary components: a cable modem (CM) located at the customer premises, and a cable modem termination system (CMTS) located at the CATV headend. An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ...


A typical CMTS is a device which hosts downstream and upstream ports (it is functionally similar to the DSLAM used in DSL systems). While downstream and upstream communications travel on a shared coax line in the customer premises, and connect to a single F connector on the cable modem, it is typical for the CMTS to have separate F-connectors for downstream and for upstream communication. This allows flexibility for the cable operator. Because of the noise in the return (upstream) path, an upstream port is usually connected to a single neighborhood (fiber node), whereas a downstream port is usually shared across a small number of neighborhoods. Thus, there are generally more upstream ports than downstream ports on a CMTS. Typical ratios of downstream to upstream ports are: 1:4 & 1:6. Siemens DSLAM SURPASS hiX 5625 A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. ... DSL redirects here. ... Male F Connector The F connector is a type of RF connector commonly used for over the air terrestrial television, cable television and universally for satellite television and cable modems, usually with RG-6/U cable or (in older installations) with RG-59/U cable. ...


Before a cable company can deploy DOCSIS 1.1 or above, it must upgrade its Hybrid fibre-coaxial (HFC) network to support a return path for upstream traffic. Without a return path, the old DOCSIS 1.0 standard still allows use of data over cable system, by implementing the return path over regular phone lines, e.g. "plain old telephone service" (POTS). If the HFC is already 'two-way' or 'interactive', chances are high that DOCSIS 1.1 or higher can be implemented. Hybrid fiber-coaxial (HFC) is a telecommunications industry term for a network which incorporates both optical fiber along with coaxial cable to create a broadband network. ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ...


The customer PC and associated peripherals are termed Customer-premises equipment (CPE). The CPE are connected to the cable modem, which is in turn connected through the HFC network to the CMTS. The CMTS then routes traffic between the HFC and the Internet. Using the CMTS, the cable operator (or Multiple Service Operators - MSO) exercises full control over the cable modem's configuration; the CM configuration is changed to adjust for varying line conditions and customer service requirements. Customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment and inside wiring located at a subscribers premises and connected with a carriers telecommunication channel(s) at the demarcation point (demarc). The demarc is a point established in a building or complex to separate... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ...


DOCSIS 2.0 is also used over microwave frequencies (10GHz) in Ireland by Digiweb, using dedicated wireless links rather than HFC network. At each subscriber premises the ordinary CM is connected to an antenna box which converts to/from microwave frequencies and transmits/receives on 10GHz. Each customer has a dedicated link but the transmitter mast must be in line of sight (mast sites are hilltop, etc). Latency and ping times are similar to or better than DSL. Digiweb are a telecommunications provider offering various broadband, Internet service provider and telephony services in the Republic of Ireland, United Kingdom, France and Italy. ...


Security

DOCSIS includes MAC layer security services in its Baseline Privacy Interface specifications. DOCSIS 1.0 utilized the initial Baseline Privacy Interface (BPI) specification. BPI was later improved with the release of the Baseline Privacy Interface Plus (BPI+) specification used by DOCSIS 1.1 & 2.0. Most recently, a number of enhancements to the Baseline Privacy Interface were added as part of DOCSIS 3.0, and the specification was renamed "Security" (SEC). The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ...


The intent of the BPI/SEC specifications is to describe MAC layer security services for DOCSIS CMTS to CM communications. BPI/SEC security goals are twofold: The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ... A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure. ...

  • provide cable modem users with data privacy across the cable network
  • provide cable service operators with service protection; i.e., prevent unauthorized users from gaining access to the network’s RF MAC services

BPI/SEC is intended to provide a level of data privacy across the shared medium cable network equal to or better than that provided by dedicated line network access services (analog modem or digital subscriber line). It does this by encrypting data flows between the CMTS and the CM. BPI & BPI+ utilize 56-bit DES encryption, while SEC adds support for 128-bit AES. All versions provide for periodic key refreshes (at a period configured by the network operator) in order to increase the level of protection. An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... RF may mean: RF, the IATA code for Florida West International Airways RF, NYSE ticker symbol for Regions Financial Corporation Royalty free Rf or RF may stand for: Radio frequency Volumetric flow rate/rate of flow (Rf) RF connectors, electrical connectors designed to work at radio frequencies Red Faction, a... The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2). ... For other uses, see Modem (disambiguation). ... DSL redirects here. ... This article is about algorithms for encryption and decryption. ... A cable modem termination system or CMTS is equipment typically found in a cable companys headend and is used to provide high speed data services, such as Cable Internet or Voice over IP, to cable subscribers. ... A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure. ... The Data Encryption Standard (DES) is a cipher (a method for encrypting information) selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976, and which has subsequently enjoyed widespread use internationally. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ...


The earlier BPI specification [ANSI/SCTE 22-2] had limited service protection because the underlying Key management protocol did not authenticate cable modems. BPI+ strengthened the service protection feature by adding digital certificate based authentication with a public key infrastructure to its Key exchange protocol. In cryptography, key management includes all of the provisions made in a cryptosystem design, in cryptographic protocols in that design, in user procedures, and so on, which are related to generation, exchange, storage, safeguarding, use, vetting, and replacement of keys. ... This page deals with authentication in computing. ... A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure. ... In cryptography, a public key certificate (or identity certificate) is a certificate which uses a digital signature to bind together a public key with an identity — information such as a the name of a person or an organisation, their address, and so forth. ... For other uses of the terms authentication, authentic and authenticity, see authenticity. ... Diagram of a public key infrastructure In cryptography, a public key infrastructure (PKI) is an arrangement that binds public keys with respective user identities by means of a certificate authority (CA). ... Key exchange is any method in cryptography which, naturally, exchanges keys between users, allowing use of a cryptographic algorithm. ...


See also

// Introduction DOCSIS Set-top Gateway (or DSG) is a specification describing how out of band data is delivered to a cable set-top box. ... This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is listed by bit/s, kilobit/s (kbit/s), megabit/s (Mbit/s), or gigabit/s (Gbit/s) as appropriate and also MB/s or megabytes per...

External links


  Results from FactBites:
 
DOCSIS project home page (194 words)
docsis is a small program that can be used to generate binary configuration files for DOCSIS-compliant cable modems.
DOCSIS stands for Data over Cable Service Interface Specification and is a standard developed by Cablelabs.
This program is useful for people/operators using DOCSIS Cable Modems that want to implement their own provisioning system, or for people testing/working with DOCSIS technology in general.
DOCSIS: Information from Answers.com (1899 words)
Modulation: DOCSIS 1.0/1.1/2.0 specifies that 64-level or 256-level QAM (64-QAM or 256-QAM) be used for modulation of downstream data, and QPSK or 16-level QAM (16-QAM) be used for upstream modulation.
MAC layer: DOCSIS employs a mixture of deterministic access methods, specifically TDMA for DOCSIS 1.0/1.1 and both TDMA and S-CDMA for DOCSIS 2.0, with a limited use of contention for bandwidth requests.
DOCSIS 3.0 features IPv6 and channel bonding, which enables multiple downstream and upstream channels to be used together at the same time by a single subscriber.
  More results at FactBites »

 
 

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