Telecommunications Design & Analysis

August 1999

Digital Subscriber Line (DSL) service is a high-speed digital service that works on copper cabling. In addition to the Bell Atlantic service I wrote about in my last newsletter, Internet Service Providers sell DSL.

What are these DSL lines used for?
Small and medium sized companies usually use DSL for Internet access. They purchase it as a lower cost alternative to T-1 service.

Who are some of the Internet Service Providers that sell DSL services?
Service providers such as Concentric Networks, Cyber Access, Flashcom, HarvardNet, ShoreNet, and Verio offer DSL. For the most part, they resell DSL from wholesalers such as NorthPoint, Covad and Rhythms.

In addition to Internet access, these providers sell e-mail, security software and web page hosting services.

What type of DSL do they sell?
The DSL service offered by Internet Service Providers is often symmetric. It is called SDSL for symmetric DSL. It has the same speed for downloading and sending to the Internet. The Bell Atlantic ADSL service is asymmetric, slower speeds are attained when sending to the Internet than when receiving information from the Internet.

Service providers claim businesses send large files and thus need equal speeds for sending as well as downloading from the Internet.

What are sample speeds and costs?
Fees depend on the speed of the DSL service and the number of IP and mailbox addresses and hosting requirements. The speeds range from 144, 160 and 784 kilobits per second to 1.54 megabits per second. Installation costs which include a router/modem are about $1000. Monthly service ranges from $150 for the lowest speed service to $500.

What is a wholesaler’s role?
Wholesalers buy copper local loops that run from Bell Atlantic’s equipment to customers’ premises. They also rent space in Bell Atlantic’s central office in which they place their DSL equipment. Specialized DSL equipment aggregates traffic from multiple DSL users and sends it to the Service Provider over high-speed links. Some wholesalers sell directly to end users.

What is the role of the Service Provider?
Service providers receive traffic from multiple wholesalers’ DSL equipment located in Bell Atlantic central offices. The service provider in turn has a high-speed connection to the Internet. Customers’ email service and web pages may be located in Service Providers’ computers.

The Service Provider sells end-users a device with both DSL modem and router functionality. The router has a connection to the customer’s internal local area network. The DSL modem connects the customer to the outside network.

How are repairs handled?
If a customer has a repair problem, they call their Service Provider who determines if the trouble is in the DSL hardware or the telephone line. If it is in the telephone line, the provider calls the wholesaler e.g. Covad or NorthPoint. The wholesaler reports the trouble to Bell Atlantic.

Who bills the customer?
The Service Provider bills the end user for installation, DSL hardware and monthly service.

What about DSL availability?
The condition of the outside telephone company-cabling impacts availability. DSL does not work on cabling that has bridge taps. (Bridge taps allow multiple customers to share a length of cabling.) According to Bell Atlantic, about 20% of metropolitan and 60% of suburban locations have bridge taps. In addition, customers must not be more than a certain number of feet from the nearest Bell Atlantic central office. About 85% of customers are close enough to central offices to get DSL service.

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Annabel Dodd Consulting • 46 Woodmere Road • Framingham, MA 01701 • Voice 508-877-6089 • Fax 508-877-9475 • adodd@doddontheline.com