 The View from Landmark |
Email Edition #2 | A publication of Landmark Computer Laboratories |
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DSL*: Distance vs. speed * DSL = Digital Subscriber Line, a technology for moving data over regular phone lines much faster than a regular phone connection It's a curious fact that the speed of a DSL connection can vary tremendously, even in a given neighborhood. Take Alexandria's Landmark area, where we live and work. Our Verizon DSL service zips along with an effective download rate of 690 kilobits per second, according to the Toastnet performance benchmark. That's an acceptable speed for a small business's broadband connection. The Verizon tech support people have told us that the Toastnet test is reasonably accurate. Yet in the next high-rise building, 800 feet away, our friend L. (he prefers anonymity) is not eligible for DSL service at all. Too far from the Verizon Central Office (CO -- the site that contains the local telephone company's equipment that routes calls to and from customers). "Too far" matters, because DSL signals dissipate over distance. In fact, according to DSL Reports, Verizon won't accept an order for DSL installation if the distance from the CO is over 15,000 feet.
We know for a fact that the DSL modem you use plays a role, too. The Westell 2100 modem left over from our last Verizon DSL hookup poked along at a consistent 88K: about half again as fast as a dialup modem. It was pathetic, and we cancelled the service. But now with the hot new Westell 2200 modem, our Verizon DSL service is fine. We can swap in the old modem and the speed goes down. Put back the new modem and it's fine. One of our commercial clients recently called us in to find out why his DSL service was so slow. Our conclusion was that his network is okay, his computers are okay, and his router is okay, but something between his modem and the Central Office is limiting the speed of his service. Exactly what is slowing down his DSL connection is something for his DSL provider to determine. If you've figured out by now that DSL is a flaky, shaky technology, you are quite right. We'll be covering DSL and other broadband issues periodically in The View from Landmark. Stay tuned.
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DSL availability: Only about 50% of Americans are eligible for DSL service, according to DSLReports, because they are too far from the Central Office, or their CO is not DSL-enabled yet, or because their local telephone company's architecture is not yet DSL-compatible.  Yet here on the eastern seaboard we often have a variety of providers we can choose. The green dots on the map represent DSL-enabled Central Offices, and the red dots, those COs without DSL. Click on the map to see the picture nationwide, and recognize how lucky we are in the Washington metropolitan area. Map from DSLReports
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