docsis 3.1CableLabs has completed an addition to version 3.1 of the Data Over Cable Service Interface Specification (DOCSIS 3.1) designed to improve upload performance. The new capabilities will be known as full-duplex DOCSIS 3.1 and will enable symmetrical broadband services.

The addition to DOCSIS 3.1, Annex F per PHYv3.1-N-17.1771-6, enables full-duplex operation. This allows data to flow as fast as 10 Gbps in the upstream and downstream simultaneously, according to a Cablelabs blog post. Previously the DOCSIS 3.1 standard supported 10 Gbps downstream but only 1 Gbps upstream.

This is a significant improvement for the cable industry. Cable networks initially were architected to deliver data primarily in the downstream direction, from the headend to the subscriber. Upstream bandwidth has always lagged downstream, partly because it wasn’t critical.

My how times have changed. This imbalance became an increasingly larger problem as demands for upstream bandwidth have increased dramatically. Slow uploads of video to YouTube, difficulties of telecommuters sending files and similar inconveniences became a competitive disadvantage. Especially at the hands of fiber broadband providers who have been offering symmetrical broadband for many years.


CableLabs recently signaled the specification had been completed, and as of today, it’s actually published. It will be some time before equipment is actually shipping with the new symmetrical capability.

In another blog post, CableLabs mentions virtual reality, telemedicine and video chats as applications that could benefit from the high-speed symmetrical services.

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