Cable Modem Terminology
Cisco uBR904 Cable Modem Installation and Configuration Guide
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User data privacy—Upstream and downstream data is encrypted to provide data privacy
protection
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Downloadable software—Software and configuration information is downloaded from
the cable headend to the cable modem
Note
Data-over-cable systems are capable of providing access speeds up to 36 Mbps.
That bandwidth, however, is shared by several subscribers because there are very few
computers today that can connect to a network at such high speeds. Typical connection
speeds to be expected are 5 Mbps downstream and 1 Mbps upstream.
To compare data-over-cable speeds with other Internet access technologies available
today, a file that would take eight minutes to download over standard telephone lines
with a 28.8 kbps modem would take two minutes to download over ISDN. The same file
would take approximately eight seconds to download over a data-over-cable system.
Cable Modem Terminology
CATV
Originally stood for Community Antenna Television. Now refers to any cable
(coaxial/fiber) based system that provides television services.
Cable modem
Any device that modulates and demodulates digital data onto a CATV plant.
Cable router
A modular chassis-based router optimized for the data over CATV HFC
application.
Channel
A specific frequency allocation and bandwidth. Downstream channels used for
television in the U.S. are 6 MHz wide.
CM Cable
modem.
Downstream
The set of frequencies used to send data from a headend to a subscriber.
Headend
Central distribution point for a CATV system. Video signals are received here
from satellite (either co-located or remote), frequency converted to the
appropriate channels, combined with locally originated signals, and rebroadcast
onto the HFC plant. For a CATV data system, the headend is the typical place to
link between the HFC system and any external data networks.
