Asymmetric Digital Subscriber Line. This is the technology used to deliver broadband over traditional copper telephone lines. The term Asymmetric denotes the difference between the download and upload speeds of broadband connections. Usually the download speeds are much higher than upload speeds in ADSL. So if you see an advertisement for ADSL at 1 Mbps, most likely that’s the download speed. The upload speed maybe 256 or 512 Kbps. In comparison SDSL (Symmetric Digital Subscriber Line) offers equivalent download and upload speeds. Almost always when you read about DSL in the media it normally refers to ADSL.