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Cool rules
Why are some of the best minds of our generation working on a better way to send out party invitations?
By Mark Gimein
[09/22/99]

Silicon Follies
Silicon Follies
Chapter 55: Barry's Singularity -- ship without a captain
By Thomas Scoville
[09/22/99]

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Domain name dunces
Network Solutions fumbles its free e-mail scheme. Can we trust it with our Net addresses?
By Scott Rosenberg
[09/21/99]

Books
A tournament of apes
"The Gorilla Game" goes out on a limb, encouraging us to invest in -- duh! -- big companies that dominate rapidly expanding markets.
By Thomas Scoville
[09/20/99]

Technology: View from the top
Mr. Fix-it
After a summer of outages, eBay recruited Maynard Webb to be chief of technologies and shore up the auction site's systems.
By Sean Donahue
[09/20/99]

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The issue isn't whether or not a link is shared. The issue is whether or not there is enough bandwidth on the shared link to satisfy all of the users at a particular time.

In bandwidth, cable is king: With the exception of fiber optics, there is no faster way to send a data stream from one location to another. In my tests, I've seen instantaneous speeds of 7 megabits per second over my cable modem -- that's the underlying speed of the data channel between my house and the next router on the network. Of course, I don't actually see 7 Mbps in my daily use. When I transfer more than a few packets of data, the cable modem is programmed to slow down the rate of transfer to roughly 600 Kbps. This prevents me from taking more than my fair share of the available bandwidth.

From the cable provider's perspective, the key to maintaining good performance is to keep a watchful eye on customers' bandwidth utilization, then deploy more facilities in advance of customer demand. For example, by monitoring my cable modem, I've determined that slightly more than 800 subscribers share my cable segment. That number will increase as MediaOne sells more cable modems in my neighborhood.

Despite its capacity, at some point the cable will reach saturation. MediaOne can then reduce the congestion by splitting the cable segment in half and installing another router at its office. I suspect that the reported problems plaguing cable modems in the Bay Area are occurring because demand has grown too fast for the cable company to keep up.

That's not the end of the bandwidth story, of course. Two factors determine just how fast the Internet will seem to the average home user. The first factor is the connection between the subscriber's home computer and the ISP. But the second factor, the one that's frequently overlooked, is the connection between the ISP and the rest of the Net.

MediaOne has done a spectacular job in the Boston area of connecting its cable modem subscribers with the rest of the global network. Packets take 12 milliseconds (20 hops) to make the round-trip from my desk to the Exodus hub in Pennsauken, N.J. (For comparison, a particle of light would take just 3.2 milliseconds to make the round-trip, implying that MediaOne has installed some awesomely fast routers between Cambridge and the Garden State.) I am 80 milliseconds away from Microsoft in Redmond, Wash. I can download Netscape Communicator 4.5 -- which resides on a server in San Jose -- in less than 4 minutes.

But I'm even more impressed by the way that MediaOne has worked to deploy connectivity within my metropolitan area. A high-speed connection between MediaOne and the Massachusetts Institute of Technology puts just 3 milliseconds between my desk and the Media Lab. That link is so tremendously fast that I can access machines at MIT about as easily as computers on my local area network. I can download and install the entire FreeBSD operating system from MIT in less than 10 minutes.

To gauge Bell Atlantic's DSL Internet service, I called up the company and had its InfoSpeed service installed at my house in August. The company sent me a DSL modem in the mail, and added the DSL service to my existing phone line. Bell Atlantic also sent me a dozen "microfilters" that I needed to install on the other telephones in my house. Without the microfilters in place, the DSL connection's high-speed data stream sounds like a loud hiss in every phone. (Truth be told, though, even with the microfilters in place I could still hear the DSL on some of my phones.)

The performance was disappointing. But the fault was not with the DSL technology, but with Bell Atlantic's Internet service provider, BellAtlantic.net, which provides the connection between the DSL line and the Internet. Bell Atlantic, it seemed, didn't have very good connectivity in the Boston area. When I tried to connect to MIT, my Internet packets ended up going through New York or northern Virginia -- and sometimes both places. It took twice as long to download Netscape Navigator.

Now, to be fair, you can get DSL from companies other than Bell Atlantic. At my office in Boston, for instance, we have a 384K DSL connection from Concentric. It too has been something of a disappointment, but for a different reason. Concentric has been advertising heavily in the Boston subway system, but the company is fundamentally a West Coast ISP with delusions of grandeur. Specifically, Concentric doesn't actually have any employees in Boston. Instead, it contracts with a company called Covad to do all the grunt work.

Concentric's West Coast bias became clear when I looked at packet traces between my Boston office and the rest of the Internet. We have truly spectacular connectivity between our office and downtown San Jose -- we're just 40 milliseconds from MAE West. This speed is a good thing, because packets from our office destined for local sites, frequently go out to California, or Chicago or New York, before looping back to Beantown. Concentric, like Bell Atlantic, doesn't seem to be a peer with the major Boston Internet service providers or with the universities.

Next page | How do I know I share my cable with 800 people?