The DOCSIS standard was created by the CableLabs consortium of cable operators and the contributing equipment manufacturers to unify the method of broadband Internet delivery over cable infrastructure, allowing vendor solutions to interoperate and lower costs.
A complimentary set of specifications was developed for the European cable standards of cable infrastucture, commonly referred to as EuroDOCSIS.
With DOCSIS 1.0 CableLabs established the hardware and communication specifications for the high speed, two-way data transfer over cable infrastructure. It specified downstream channel widths of 6 MHz and modulations of 64- or 256-QAM, and upstream widths up to 3.2 MHz using QPSK or 16-QAM modulations. This allowed a shared medium of up to 40 mbit/s downstream and 10 mbit/s upstream.
DOCSIS 1.1
With an increase in demand for specialized traffic such as voice, CableLabs developed DOCSIS 1.1. This introduced service flows into the DOCSIS architecture. These service flows can be uniquely defined to allow specific types of traffic well defined parameters for enhanced throughput to meet the needs of that traffic type. This allowed efficient support of applications requiring predictable traffic requirements, such as Voice over IP (VoIP). The downstream and upstream specifications remained the same as DOCSIS 1.0.
DOCSIS 2.0
As customer demand on upstream bandwidth requirements grew, DOCSIS 2.0 was developed to enhance upstream bandwidth capabilities. To accomplish this, the specification utilizes a new channel width up to 6.4 MHz and modulations up to 64- or 128-QAM. By doing this the upstream speed capabilities were increased from 10 Mbit/s to 30 mbit/s per channel.
Backwards Compatibility
Backwards compatibility was built into each new revision of the DOCSIS specification, allowing continued utilization of the existing infrastructure. For instance, DOCSIS 1.1 capable cable modems can be provisioned for enhanced QOS which will be applied and enforced on the same cable segment populated by modems provisioned for DOCSIS 1.0, and both can run simultaneously. Similarly DOCSIS 2.0 enhanced upstream modulations of 64-QAM can be run on the same channel as DOCSIS 1.0 modems only capable of 16-QAM in mixed mode operation.
DOCSIS 3.0
With downstream and upstream bandwidth being consumed by newer applications, a need for even more bandwidth emerged. In keeping up with the growing need for bandwidth DOCSIS 3.0 was developed and maintained the same backwards compatibility by utilizing the same upstream and downstream standards.
The benefit of DOCSIS 3.0 capable modems is the ability to bond multiple channels, greatly increasing bandwidth availability. While the practical limit of 10 or 20 Mbit/s on downstream speeds could be offered on single channel, DOCSIS 3.0 can add up channels and allow 100 Mbit/s and above. The current cable infrastructure, including plant and cable modems, is still utilized. Additional channels in each cable segment are provided by the CMTS, which can be used by both existing DOCSIS 2.0 (and below) modems and DOCSIS 3.0 modems for bonding across the new channels.
Why You Need DOCSIS 3.0
With channel bonding schemes of four or more channels, downstream speeds exceeding 100 Mbit/s can be offered. With the much increased downstream speeds, many service providers are investigating DOCSIS 3.0 as a method to deliver IPTV. With the enhanced two-way communication and interactive services, as well as customized content delivery similar to Switched Digital Video and Video on Demand, DOCSIS 3.0 can be the launchpad for an enhanced customer experience.
Typically the downstream has been the bottleneck most providers have experienced, and most vendors have concentrated on solving that problem first. Upstream bonding is soon to be supported on the Cisco uBR10012 platform on the "H" version of the 5x20 line card, and future cards will enhance the upstream capabilities even further. Current cable modem packages usually only offer a maximum of two to three Mbit/s upstream, but DOCSIS 3.0 will make upstream offerings of 20 Mbit/s or even higher a reality.