docsis tutorial Archives

28 02, 2009

DOCSIS and Cable Modems – How it works :: UCD

Mia Colabrese2021-08-17T10:36:51-04:00February 28th, 2009|

Just as a picture is worth a thousand words, so is a complete Upstream Channel Descriptor (UCD) as seen by a cable modem. This message, sent every two seconds by the the CMTS, contains an enourmous amount of valuable information that every cable modem on a DOCSIS network needs to know in order to communicate. Often undervalued, the UCD is a virtual Hitchiker's Guide to the DOCSIS network! So without any further ado, let me show you an example of a full UCD message and then explain its contents further

16 02, 2009

Troubleshooting DOCSIS – VoIP Impairments > Delay & Jitter

Mia Colabrese2021-08-17T15:54:55-04:00February 16th, 2009|

In this blog I will address delay and jitter as they pertain to VoIP in a DOCSIS network. Delay, jitter and packet loss are the three primary impairment in a VoIP network, but packet loss was addressed in my Troubleshooting DOCSIS - VoIP Impairments > Packet Loss blog. After packet loss, delay is the second most disruptive impairment in VoIP networks. The effects of delay to the caller generally appear as echo and talker overlap. In PSTN communications, echo can arise as acoustic echo between the mouthpiece and

13 02, 2009

Troubleshooting DOCSIS – VoIP Impairments

Mia Colabrese2023-02-18T10:49:47-05:00February 13th, 2009|

In this blog I am going to digress for a moment from my standard DOCSIS 101 tutorial and spend a little time on DOCSIS troubleshooting basics, especially with respect to Voice-over-Internet Protocol (VoIP). I am doing this as due to many offline questions specific to this topic. Don't worry, though I may start to inter-mix some troubleshooting blogs now and again, just check the DOCSIS 101 page to stay on top of the latest DOCSIS tutorial blogs.

9 02, 2009

DOCSIS and Cable Modems – How it works :: Cable Modem Registration

Mia Colabrese2021-08-17T09:54:53-04:00February 9th, 2009|

Through DOCSIS tutorial seminars, I have found the most effective way to bring someone up to speed on DOCSIS communications is by teaching the cable modem registration process. During the registration process, we will cover the RF physical layer, theDOCSIS Media Access Layer (MAC) and the Internet Protocol (IP) layer. Yes, the cable modem exercises the first three layers of the Open Systems Interconnection Reference Model (OSI Reference Model or OSI Model)...

5 02, 2009

DOCSIS and Cable Modems – How it works :: Upstream RF

Mia Colabrese2021-08-17T13:29:04-04:00February 5th, 2009|

Cable modems use RF (radio frequency) signals to transport data over hybrid-fiber coax (HFC) networks according to the DOCSIS® specification. This blog will discuss the finer points extracted from the DOCSIS specification related to how cable modems communicate with the headend Cable Modem Termination System (CMTS), allowing two-way transport of Ethernet traffic over a cable TV network. There are currently three major revisions and one sub-revision of the DOCSIS specification; DOCSIS 1.0, 1.1, 2.0 and 3.0. With each major revision came significant changes to the cable modem upstream specification because the upstream has typically been the bottleneck in terms of data through-put rates as will be discussed.

27 01, 2009

DOCSIS and Cable Modems – How it works :: Introduction

Mia Colabrese2021-08-26T08:28:17-04:00January 27th, 2009|

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...