Cable Modems and OS/2: Speed and Benefits

So, what's the deal?

asically, the list of benefits of cable modem access over POTS Internet access is short, but significant. First of all, of course, cable modem service is a lot faster than a dialup telephone modem.

Secondly, since it uses your cable TV line instead of your telephone line, you won't tie up your phone when you're on-line.

And speaking of being on-line, you will be, 24 hours a day, 7 days a week. Cable modems are always on, connected to the network, so most companies (at least all we have heard of so far) are offering unlimited access. Also, due to its "always on" status, there is no annoying login delay with a cable modem. Open Netscape Navigator or your favourite e-mail app and you're in business.

And, finally since you're always on-line with your cable modem, your IP address may remain the same for long periods. You could theoretically set up a WWW or FTP server and give out your IP address to your friends. (Because my area uses DHCP to give new IP addresses each time a machine is booted and logs on to the network, my IP will still change each time I reboot. Some areas use static IPs so you could theoretically register with InterNIC for your own domain name and serve it from your home machine.)

Quit playing with me! How fast is it?

Claims vary widely from one cable company to another, depending on many things (the state of their network, internal marketing decisions, the amount of local competition, etc.), but basically, cable modem service is offered at roughly 500kbps or, in my area, at 5 mbps.

Yes, that says 5 mbps, as in five megabits per second. But before you get delirious and rip out your USRobotics 14.4 (the cable modem is 347 times faster, after all), you should know that that is only a technical specification. Real world speeds will likely not ever be that good for you -- they will likely be much faster than your telephone modem, but realistically, not 347 times faster. For various reasons, it seems that the 5 mbps service offered here is really little different than the 500 kbps service offered by cable companies elsewhere, so don't feel cheated if you're in one of the "slow" areas.

Some of the limiting factors on cable modem speeds are:

1. the available bandwidth on the Internet itself;
2. special considerations for WWW sites;
3. sharing of bandwidth between local cable customers; and
4. possible inadequacies of the cable network itself

First and foremost, you've got to realize that promises of 5 mbps, 10 mbps or 27 mbps access to the Internet is actually more hype than substance due to the structure of the Internet itself. Because it is a diversified network, bottlenecks abound, and data often doesn't flow too quickly between you and another point. Some sites might have a great pipeline directly to you, but others might be hobbled by a weak link somewhere. Also, no matter how fat the pipe between you and www.yahoo.com is, if 1,000 people in your area are using that pipe at a given time, you're only going to have access to 1/1,000th of that bandwidth.

Depending on your uses of the Internet, another very important consideration may be the speed of WWW sites. A great deal of time on-line can be spent waiting for WWW sites to reply to your requests for HTML pages, graphics, sound files, etc. You've all seen the messages: "Contacting host: www.yahoo.com..." and "Host www.yahoo.com contacted. Waiting for reply..." in Navigator's status line. Neither a cable modem nor a direct line to God will speed those wait times up. These times depend on the speed of the remote server and the number of people trying to access that server, so expect to still spend some time staring at blank screens, no matter what technology you're using.

You will also theoretically be sharing whatever bandwidth is available from your cable company with every other customer on your local 'node'. In my case this hasn't proved to be an issue yet (because we have a ton of bandwidth each and because there are only few customers so far), but it's something to consider for the future. For what it's worth, my cable company has made vague promises that overall network bandwidth will be raised to meet any needs of increased customers.

Finally, your cable company does have to make a substantial investment to their network to bring you all these wonders. While the old coaxial cable network that they have lined your city with has tons of bandwidth for one way transmission, it lacks the capacity for good two way transmissions. There are various solutions to this problem, but one of the best (and most expensive) is to completely upgrade the system to a hybrid of coaxial cable and fiber-optic cable. This is what Access Cable did here (finishing about a year ago, they tell me), but you should check your provider to see what their status is.

Benchmarking the Internet

The good news is that even with these caveats, you'll still enjoy much faster Internet access with a cable modem than you're probably used to. For example, in my experience with a USRobotics Sportster 33.6 fax modem, I would rarely see transfer speeds over 3.5 - 4.0 kBps (or 28,000 - 112,000 bps), usually much less. With my cable modem firmly installed, WWW pages, graphics, zip files downloads, etc. normally speed to me at 30 - 50 kBps (or 240,000 - 400,000 bps), depending on time of day and remote location. I have even seen extremely good connections with speeds up to 130 kBps (1,040,000 bps) which is approaching T1 speeds (1,500,000 bps). While writing this article I downloaded a 5.2 megabyte Java runtime file from IBM at a sustained transfer rate of 70 kBps. Over time, I have found the average file transfer speed of the cable modem to hover around 40 or 50 kBps.

To give you some reference to what this speed means to you, take the Stardock Systems' Entrepreneur Demo. This 11.2 megabyte file takes between 4.5 and 5.0 minutes to download at roughly 40 kBps in the middle of the day over my cable modem. Try that on a telephone modem.

As with all things, speeds will vary from user to user, and place to place, but it's clear that the bottom speeds here are much faster than can be achieved with a telephone solution.