The hardest question is still Can You Get DSL. After years of software development effort and data cleaning by Telcos and their DCLEC competitors, there is still no reliable answer to this question, without actually ordering it, then plugging in the DSL modem in and waiting for a green light.

Perhaps these screenshots can explain why nobody knows availability for a new address for sure: Telco, CLEC, ISP, for many addresses, we're all in the dark.

The screen-shot to the left is a 500 mile chunk of California coastline, taken from the SBC DSL Availability tool. (Click on the picture to enlarge it). This program allows SBC and authorized CLECs to zoom into increasing levels of detail of SBCs wire center and DSL boundary database.
Each of those little blue stars is a Telco Wire Center, and the lines define the boundaries of the area they serve. (It is interesting to note lines of blue stars marching across the country, perhaps following a major communications link, and/or highway).

Zooming further into the San Francisco bay area, one can see that some wire centers serve huge, albeit sparsely populated geographical areas.. 30 miles or more! On the other hand, the populated areas are still a mass of COs. For even the largest CLECs offering DSL, such as Covad and NorthPoint, all they have to go on for DSL availablity in any state are the location of these COs, and the boundaries of their service areas. They then must make educated guesses using further mapping databases to filter customers that are likely to be too far, from those that are almost certainly near enough. How well can an automatic filter based on positions and maps really do? lets continue down to further levels of detail and see!

Now we down into a 100 mile square area, and most of the COs are switched on for DSL.. but of course that still leaves the problem of distance from the CO.. Please note, this mapping tool is unique to SBC, and not employed like this for the mass of DSL prequalifications done by the CLECs or their partner ISPs.. so you are looking at a more accurate picture here than even Covad and NorthPoint is utilizing in production!

At the level of 30 mile square areas, the application is able to start giving us critical information on DSL availablity.. Green for DSL Yes, Yellow for DSL Maybe, and Red for DSL No.
It is plain that despite the number of COs that are DSL equipped in such an important city, zones are still unreachable. In addition, one can start to see the irregular nature of DSL availablity. Little green DSL compass circles with radius 18000 freet are clearly not the case.

At the 10 mile level, the streets become clearer. There are obviously thousands of cases here where even direct neighbors will have radically different experiences when ordering the same service. It is also possible to tell that driving distance estimates on DSL availability such as typically offered on other web-sites, are of limited use.. availability as predicted by the SBC system here, does not obey crow-fly, or crow-drives, distance rules!


Here we can see street names. For those in the green area, DSL availability is a high probability, and only very unusual problems could get in the way of a connection. For those in the yellow area, DSL availability is impossible to tell from data alone.. the only way to find out is to try an order. For those in the red area, only a remote DSL terminal will help their situation.

So next time your ISP does a flip/flop on availability, or available speeds, remember that until your sync light goes green, there are no guarantees and no fast answers when it comes to the question, Can I get DSL?.

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See also: DSL install explained from start to finish
DSL from the installer