Hardware Reference
In-Depth Information
Figure 16.1. A typical hybrid fiber-coax cable TV network that also includes two-way cable
modem service.
A typical two-way cable modem connection is shown in
Figure 16.1
.
Originally, cable modems used proprietary technology and were not sold to users of CATV Internet
access but were leased by the CATV companies offering Internet access to their cable modem
customers. This is because each cable modem on a particular CATV network had to match the
proprietary technology the network used. In late 1998, some CATV companies began to use DOCSIS-
compliant cable modems. DOCSIS refers to devices that meet the Data Over Cable Service Interface
Specification standards established by Cable Television Laboratories, Inc. (CableLabs). Modems
that meet DOCSIS standards are now referred to as
CableLabs Certified cable modems
. Visit the
CableLabs website at
www.cablelabs.com
for a complete list of cable modems that are CableLabs
Certified.
Many vendors of traditional modems and other types of communications products, such as 3Com,
ARRIS, Motorola, Cisco, and D-Link, make CableLabs Certified cable modem-compliant hardware.
The models supported by your CATV Internet provider are usually dependent on the DOCSIS
standard they support.
Table 16.1
provides a brief overview of the differences in these standards.
Table 16.1. DOCSIS Standards Overview
Many cable providers now require modems that are DOCSIS 2.0 or 3.0 certified to provide stated
performance. Older DOCSIS 1.1 or earlier modems might work, but only at lower speeds. The latest
high-speed (50Mbps or faster) connections require DOCSIS 3.0, which uses channel bonding to
achieve higher speeds. Check with your cable service provider for the minimum required standard
before you purchase or install a cable modem. To verify the certification level of a specific modem,
you can check the modem specifications on the manufacturer's website or look it up in the current
cable modem certification list (Certified_Products.pdf or cert_qual.xls), which you can download
from CableLabs (
www.cablemodem.com
). Most cable modems also have their own built-in web
page, which can show DOCSIS version and modem status information. To view the page, enter
192.168.100.1
in the address bar of your web browser, and press Enter. If you are suddenly
experiencing problems with your cable modem, I recommend you contact your provider to find out if
the requirements have changed. If so, you may need an upgraded modem.
Note
Cable Internet providers have greatly increased connection speeds over the years. If your cable
