What's Wrong with High Bit Rate DSL Offerings?

Joe St Sauver
joe@oregon.uoregon.edu

When we think about DSL service, most of us think about the 256Kbps (or maybe 640Kbps) DSL service we can get for home use for $30/month plus $20/month for ISP service.

However, DSL service is also available at much higher speeds. Many businesses and smaller schools may be tempted to consider it as an alternative to traditional point-to-point T1 service, which may run $700 to $2000/month for ISP service, plus additional hundreds of dollars (or more) per month for the leased T1 line itself.

Given those charges, many would be intrigued to learn that they could buy 7.1 Mbps worth of download and 1.1 Mbps worth of upload DSL service for only $405/month ($250/month for the circuit plus typically $155/month for ISP service on the circuit).

Given that huge difference in pricing and capacity, you may wonder why anyone still buys point-to-point T1 service. In fact, there are actually a number of reasons why high bit rate DSL hasn't driven point-to-point T1 service out of the marketplace:

1. High bit rate DSL service is not going to be available everywhere. Typically, DSL service is limited to sites no more than 18,000' from a DSLAM equipped telephone company central office, and high bit rate DSL service may require that you be even closer. T1s, on the other hand, can be installed virtually anywhere.
2. High bit rate DSL service is asymmetric. While you will be able to download content at 7Mbps from the Internet, you will only be able to upload content to the Internet at 1.1Mbps. (Contrast that with a point-to-point T1 which would offer you 1.5Mbps symmetrically in each direction.)
3. At least some DSL-servicing ISPs (such as qwest.net) force all web traffic through their local web cache box, thereby breaking Internet transparency. You wondered how they could afford to offer those great prices--and now you know! ISPs are taking advantage of the fact that some large fraction of your traffic will probably be http--and most likely web pages serviceable from a local web cache, at that.
4. Your equipment options may be limited. Most DSL service providers have standardized on a particular brand of DSL modem (such as the ~$300 Cisco 675 or 678), and that is what you'll need to use if you want DSL service, like it or not. Why is this an issue? Well, for example, many DSL modems are clearly consumer grade products rather than carrier grade gear.
5. You have a restricted set of possible ISPs to offer service on your DSL circuit. Most national backbones and many regional ISPs will not be available, with the result that you need to pick either a local DSL-servicing ISP or the phone company's unregulated ISP affiliate. See, for example, http://www.qwest.com/dsl/learn/isplist.html
6. Finally, because DSL service is basically positioned as a consumer Internet access technology, outage response and repair times--critical factors for commercial/institutional connectivity--are essentially unbounded for DSL service. Given the thin profit margins associated with DSL service vis-a-vis traditional leased line T1 service, it is simply not realistic to expect the same level of service from the telephone company in case of a loss of service.

For all of these reasons, do not expect to see high bit rate DSL service completely displace traditional point-to-point T1 service any time in the near future.