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DescriptionData-over-Cable Service Interface Specifications (DOCSIS)

Complete Description

Data Over Cable Service Interface Specification (DOCSIS) is an international standard developed by CableLabs and contributing companies that include: ARRIS, Harmonic, 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 1997, with revision 1.1 (adding Quality of Service (QoS) capabilities) following in April 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 CMTS).

Speed Table

Maximum synchronization speed (Maximum usable speed)

Downstream Upstream Downstream Upstream
1.x 42.88 (38) Mbit/s10.24 (9) Mbit/s55.62 (50) Mbit/s10.24 (9) Mbit/s
2.0 42.88 (38) Mbit/s30.72 (27) Mbit/s55.62 (50) Mbit/s30.72 (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 6 MHz channels as MAX spectrum allocation for DOCSIS3.0 data, 60 MHz 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 1 Gbit/s speeds in the future

Other Definitions:

Wikipedia DOCSIS Definition


The International Telecommunications Union Telecommunications Standardization Sector (ITU-T) has approved the various versions of DOCSIS as international standards.

  • DOCSIS 1.0 ITU-T Recommendation J.112 Annex B
  • DOCSIS 1.1 ITU-T Recommendation J.112 Annex B
  • DOCSIS 2.0 ITU-T Recommendation J.122
  • DOCSIS 3.0 ITU-T Recommendation J.222 (J.222.1J.222.2, J.222.3).

Note: There are also version of Euro DOCSIS.

Also See:

  • UBR Universal Broadband Router

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