For example, while the DOCSIS 1.0 protocols can support best-effort, nonreal-
time classes of service well, it cannot reliably support real-time or time-sensitive
services. The tradeoff was a good one, and the DOCSIS 1.0 standard quickly became a
success.
After realizing the tremendous success of the DOCSIS 1.0 standard, cable operators
decided to pursue enhancements for delivering real-time services, such as voice and
streaming video, over their networks. To enable those services, the second version of
the DOCSIS standard, DOCSIS 1.1, was developed, which contained several improvements,
including quality of service (QoS) capabilities. Those capabilities were put to use
via a QoS provisioning and management architecture dubbed PacketCable. The first
service offered via this framework was residential voice-over-IP telephony.
To significantly increase upstream capacity, a third version of the DOCSIS standard
was developed that built on the success of the first two versions. Known as DOCSIS 2.0,
this version enhanced the physical layer of the DOCSIS system by
?– Significantly increasing upstream bandwidth
?– Improving robustness to RF impairments
?– Providing backward compatibility with DOCSIS 1.
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