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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

Previously I have discussed that cable modems share the upstream channel by using Time Division Multiple Access (TDMA).  This means that when a cable modem is not transmitting data its RF transmitter is turned off.  In order to transmit data it must transmit a burst of data which contains a REQUEST to the CMTS.  The [...]

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 [...]