A cable modem allows your cable television company to provide Internet access through your cable wiring. Usually you don't have to subscribe to cable TV services to subscribe to cable Internet services.
A cable television system typically has 60 or more channels, and most of them are used for programming services like CNN, ESPN and HBO. These channels also can be used to offer high-speed Internet access service. Cable modems connect to the cable network with a standard coaxial cable, just like the wiring that's plugged into your television set to receive cable TV service. The cable modem then connects to your PC through a standard Ethernet interface.
Your cable company will tell you what the system requirements are for your machine. In addition to a capable computer system, you will probably need a network interface controller (an Ethernet Card).
Usually the cable company provides the cable modem on a lease or rental basis.
There are more than 20 manufacturers of cable modems today, including 3Com, Cisco Systems, Com21, Motorola, Nortel Networks, Philips, Terayon, Thomson, Toshiba, Samsung and Sony.
Today, cable modems aren't widely available for purchase by consumers, primarily because most products are proprietary. That is, if your cable company is using Motorola network equipment, only a Motorola modem will work with it. That's why cable companies usually lease modems to subscribers. Then, you won't get stuck with an obsolete unit as the technology evolves.
Cable companies are just starting to deploy cable modems based on the DOCSIS standard, and some of the units are available in a few retail outlets, but distribution is limited. You may want to lease the modem your cable company is offering today, and buy a new DOCSIS modem down the road.
DOCSIS, which stands for Data Over Cable Service Interface Specification, is the North American standard for cable modem products. CableLabs, an industry technology organization, developed the DOCSIS standard to ensure that cable modem equipment built by a variety of manufacturers is compatible.
CableLabs is managing a rigorous testing process for DOCSIS cable modems. Products that pass the tests are deemed "CableLabs Certified." So far, DOCSIS modems from 12 manufacturers have won approval.
Like DSL, the most obvious advantage is speed. Cable modems can offer download speeds from the Internet in excess of 1 mbps -- at least 20 times as fast as a traditional telephone modem. Web pages that take minutes to paint in with a dial-up connection pop up instantly with a cable modem.
Another advantage is that your connection to the Internet is instantaneous and available 24 hours a day. When you want surf the Web, all you need to do is type in a site's address. There's no need to "dial up" an Internet service provider, as you must do with traditional telephone modems.
Most cable service providers issue a static IP address for each subscriber. With a static IP address you can run various servers such as your own Web site, FTP site or game server.
Cable modems typically have an Ethernet output, so they can connect to the LAN with a standard Ethernet hub or router. With a low-cost router that uses IP masquerading or by using Network Address Translation (NAT) software, such as WinGate, you have the ability to share your Internet access between several local machines.
Some telephone companies argue that ADSL is superior to cable modems because it offers a "dedicated" connection and that cable network performance degrades at peak hours, but this dedicated connection is at lower bandwidth. For example, while an ADSL modem may offer a dedicated 256 kbps, a cable modem can burst to speeds many times higher than that.
You will probably need to provide a network interface controller (nic) such as an Ethernet card. Price range for a 10/100mbps auto-sensing PCI network card for a PC is currently from $20-$60.
Since your computer sits directly on the Internet, it is open to attacks from hackers, therefore some sort of firewall software should be used. Many firewalls are commercially available.
The one area of vulnerability for both cable and ADSL modems is tied to the network settings for file- and printer-sharing options on your Windows or Macintosh computers. To keep hackers out of your files, be sure to disable those settings before connecting your cable modem.
Cable modem Internet service is only available in certain areas. Check with your local cable company for details.
Last updated: 11 January 2001
Comments: webmaster
Copyright 2000, The
Trustees of Indiana University