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DOCSIS and Cable Modems – How it works :: Introduction

Post 193 of 194


Over the past several years of training people on troubleshooting DOCSIS® networks and explaining how DOCSIS cable modems and CMTSs work, I have been asked numerous times - "Why don't you write a book on this?"  You see, there is no definitive book, guide or manual that explains the Data-over-Cable Service Interface Specification (DOCSIS) other than the several hundred page specification itself.  While I recommend that everyone interested in fully understanding DOCSIS read the specification located on the CableLabs website at www.cablelabs.com, I will warn you that it can be very technical.  So what I will do over the next several posts on this DOCSIS 101 blog is provide a boiled-down version of the operation of the DOCSIS specification, i.e. how cable modems connect to the cable modem termination system (CMTS) and transmit data.  While I will provide quite a bit of technical detail, I will try to communicate it in such a way that a Ph.D is not required to comprehend it.

First, some disclaimers.  DOCSIS® is a registered trademark of CableLabs.  Founded in 1988 by cable operating companies, Cable Television Laboratories, Inc. (CableLabs®) is a non-profit research and development consortium that is dedicated to pursuing new cable telecommunications technologies and to helping its cable operator members integrate those technical advancements into their business objectives. CableLabs has been the cornerstone for the development of many standards in the cable telecommunications industry, most notably DOCSIS and a number of standards which have extended the capabilities of the DOCSIS specification.

Tune in for my next post where I will describe the radio frequency (RF) spectrum allocated to DOCSIS cable modem communication and how this allows the data to be transported from the cable operator to your home or office.


Mr. Volpe has over 25 years of communications industry experience. He is focused on the cable and telecom industry with deep technical and business skills. Mr. Volpe is currently the president and chief technologist of the Volpe Firm and holds an MSEE with honors.

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