Compared to the performance of cable Internet service, DSL speed has historically been slower. However, the speed of DSL Internet is increasing as the technology improves and service providers upgrade their network infrastructure. The exact DSL speed you will enjoy varies depending on several factors. How fast, then, is DSL?
Service providers advertise DSL speed in terms of bandwidth ratings. Bandwidth numbers advertised for residential DSL service range from 128 Kbps to 3 Mbps (3000 Kbps).
Because these DSL speed ratings vary so widely, it’s best to check first with your service provider to determine the bandwidth levels associated with your subscription. Many providers offer a choice of DSL services with different bandwidth ratings.
DSL Speed of Downloading and Uploading
Your DSL speed can change depending on how you use the network.
DSL providers often advertise speed of their service using a combination of two bandwidth numbers; for example, “1.5 Mbps / 128 Kbps.”
The first number, 1.5 Mbps in this case, refers to the maximum bandwidth available for downloads. Examples of network download activities include browsing Web sites, receiving files from P2P networks, and receiving emails.
The second number, 128 Kbps in this case, corresponds to the bandwidth available for uploads. An example of network upload activities includes publishing to Web sites, sending files over a P2P network, and sending emails.
Residential DSL services often provide higher bandwidth for downloads than for uploads, as most customers spend more time in network downloading activities. These are sometimes called asymmetric DSL (ADSL) services. In ADSL, the first bandwidth number will be much higher than the second as in the example above.
With symmetric DSL (SDSL), both numbers will be the same. Many business-class DSL services utilize SDSL, as business customers often spend significant time uploading over their networks.
DSL Speed Differences Between Households
The rated maximum bandwidth of a DSL connection often cannot be reached. Additionally, actual DSL speeds vary between households. Factors affecting DSL speed include:
Quality of the phone line at your residence. Neighborhoods with better copper wiring can achieve somewhat faster DSL speeds.
Length of the phone line between the residence and the phone company hub (often called “central office”). DSL technology is “distance sensitive” because its performance decreases significantly as you get further away from this hub.
Service glitches. While normally a constant, DSL speed can suddenly drop if the service provider has technical difficulty with their network. Speeds should return to normal after a few minutes or hours.
Short of rewiring their residence, customers can do little about changing these factors. Other factors you can more directly control include:
Spyware on the computer(s). Even when the DSL network may be functioning at full speed, spyware programs may be consuming the bandwidth, robbing your DSL speed. Anti-spyware programs should be run regularly on networks to prevent this problem.
Misconfigured wires or wireless router. Routers sit between your computers and the Internet connection. If not functioning properly, a router can greatly limit the DSL speed achievable on all computers. Temporarily connecting a computer directly to the Internet can help diagnose this situation.
Slow wireless network connection. In extreme cases, a very slow Wi-Fi connection between a computer and a wireless home network will not keep pace with the speed of the DSL Internet connection. Improving the quality of the Wi-Fi connection will solve this problem.
Old computer(s). Very old computers lacking sufficient processing power or memory cannot keep pace with a high-speed DSL connection. You can verify this problem by comparing the DSL speed between computers at the residence.