Find out everything you need to know about cable broadband.

What is it?

Cable Internet is one of the two most common ways of going broadband. It can make your Internet access many times faster than with a conventional dialup modem. Cable Internet works over the same HFC networks that provide cable television service. In HFC (hybrid fiber-coax) networks, coax (TV cable) is used within neighborhoods, and optical fiber connects neighborhoods to central facilities.

How does it work?

Cable Internet works by using TV channel space for data transmission, with certain channels used for downstream transmission, and other channels for upstream transmission. Typically, there is considerably more capacity deployed for downstream transmission than for upstream transmission, which is why many cable Internet providers prohibit types of use that make heavy use of upstream capacity (e.g. servers). The shared nature of cable Internet makes everyone on a given segment (neighborhood) suffer if the capacity of that segment is overwhelmed.

Cable Internet is based on transmission between a subscriber cable Modem (which looks like a conventional dialup modem) and a CMTS (cable modem termination system), a relatively large headend box. The range of cable Internet is effectively unlimited, available at any location passed by an appropriate HFC network.

What makes cable Internet better than dialup?

  • Speed. Typical downstream cable Internet speed is 1,500 Kbps, roughly 25 to 50 times faster than standard 56-Kbps V.90 (or newer V.92) dialup modems.
  • Always on. Because it is always connected, cable Internet is more convenient than having to dial up with a conventional modem. In addition, cable Internet doesn't need a telephone line.
  • Latency. Cable Internet signals have much less transmission delay than do dialup signals. While that difference in delay doesn't make much difference when surfing the Web, it can make a big difference in real-time gaming over the Internet.


Can you get it?

Older cable television systems have to be upgraded to make cable Internet possible. If your service is so-called digital cable, then your chances of being able to get cable Internet are good. Contact your cable television company to find out if cable Internet service is available. Note that you may be able to get cable Internet service even if you don't subscribe to cable television.

Where do you get the cable modem?

Cable Internet has embraced a standard known as Docsis (data over cable service interface specification). If your cable Internet provider supports Docsis, then you aren't necessarily stuck getting your cable modem from your provider -- you should be able to purchase your own cable modem from a retail or mail-order reseller. Nevertheless, it is still important to select a cable modem that is supported by your provider -- ask for a list of approved cable modems before making a purchase.

How is cable Internet installed?

Of the two basic types of cable modems, external and internal, external is strongly recommended because it is easier to install and generally avoids driver problems. External modems are further divided into two types of connections to your computer: Ethernet and USB. Although USB is convenient and usually works fairly well, Ethernet tends to be more stable and efficient. USB requires a USB port in your computer, whereas Ethernet requires an Ethernet port. Performing the installation yourself is relatively simple.

Can I share cable Internet service on more than one computer?

Although cable Internet service can be shared by using software (e.g. Microsoft Internet Connection Sharing), the recommended way to share broadband is to obtain a low-cost SOHO router (e.g. Linksys BEFSR41), which is essentially a connection-sharing device. A SOHO router has the additional benefit of providing protection from Internet crackers by using NAT (network address translation) or a firewall. (A firewall is designed to block unwanted traffic.) A wealth of information on sharing and networking can be found at Practically Networked.

Is cable Internet safe?

Yes and no. You run a significant risk of being victimized by Internet crackers, but you can greatly minimize that risk by taking some simple precautions:

  • Antivirus. Run good antivirus software and keep it up to date.
  • Software firewall. Run firewall software on any computer that is connected to the Internet. An excellent free choice is ZoneAlarm.
  • File sharing. If you want to share files locally on more than one computer over your own network, a SOHO router is highly recommended. Otherwise, sharing could make you wide open to Internet crackers. (For detailed advice on file sharing, read how to share your files with NetBIOS over cable modem or cable Internet.)


Are all cable Internet providers the same?

Cable Internet increasingly gives you a choice of Internet service providers (ISPs). Quality of service can and does vary widely, even on the same HFC network. Be sure to find out if more than one ISP is available to you, and take the time to compare service offerings and reputations.

For more information on cable Internet, see the Navas Cable Modem/Cable Internet Tuning Guide.

John Navas is the author of the Navas Cable Modem/Cable Internet Tuning Guide.