Number 197 - October 1999

How Fast Is A Cable Modem?
by Bob Thomson, Tacoma Open Group
I am a subscriber to TCI's @Home service which uses a fiber optic cable network throughout the city of Tacoma, a coaxial cable to a cable modem then an interface device and USB connection to my computer. It is very fast. It does not use the telephone system in any way.     At a recent TOG meeting, the experiences of some of our members using the telephone company's ADSL service were discussed. I mentioned my cable modem is very fast--faster than ADSL. When asked what speeds it achieved and I couldn't answer. I now have information which is more than anecdotal. The Official Line     The following question and answer were excerpted from an official TCI document:     Q. How Fast is TCI@Home?     A. @Home's broadband technology offers speeds far greater than dial-up modems, ISDN or even ADSL. For example, a file that takes 9 minutes to download over a 28.8 phone modem would take 2 minutes on ISDN, compared to 2 seconds on TCI@Home. Actual speed experienced is dependent on several factors, including the file size, server congestion and your computer."	My Unofficial Experience     I have observed that, when I am downloading from another @Home service, transfer rates are at least 400 KB/sec often exceeding 500 KB/sec. Although I saw it happen only once, one download speed went as high as 1100 KB/sec!     Recently, I downloaded the free StarOffice 5.1 suite which is a Microsoft Office work-alike and is free for personal non-business use. It is available at several sites around the world listed at www.stardivision.com. I downloaded it from a North Carolina University site. When it started out the transfer speed was 9 KB/sec then as it proceeded the throughput quickly increased, in 10 or 15 seconds, to 30 KB/sec finally reaching 50 KB/sec in a minute or so. It then hovered between 49 and 52 KB/sec for the remainder of the download. This was a 62MB file so at 9 KB/sec would take over 2 hours to download. I didn't time it exactly, but it took less than the 21 minutes calculated using a 50 KB/sec rate.     Clearly the transfer rate depends on the throughput capability of the originating site server as well as every element in the infrastructure between it and my computer. My computer, modem and cable system is capable of at least 500 KB/sec. The other elements in the download described reduced this capability to one tenth of this capacity. I don't know how "typical" this is. Some sites are probably worse, some better. This was just one experience where I took note of the numbers for comparison.
Number 197 - October 1999