DSL (Digital Subscriber Line) is basically 24-hours on internet connection and working with high speed up to 10 Mbps. DSL service provider offering different packages with speed 128 Kbps to 10 Mbps. But the actual speed at user end may be different from user to user due to the modem speed, telephone line condition and the distance between services provider to user home. If you want your DSL working with good speed and error free then make sure there is no any joint between telephone line tower and modem line. Your DSL modem may be heat up, hang and slow, if your DSL modem continually on for 24-hours, then restart it to solve this problem.
There are many DSL providers offers free speed test software with Internet connection package to check speed frequently. Many third parties software provider companies offer free speed check software on internet, download and use it to monitor speed constantly. Yon can test speed using any website for this purpose, search speed test tools websites using any search engine. DSL speed test result will be different in different times, may be fast during early morning and slow at peak hours. You should get the results in different hours then with the help of average decide about the actual speed.