How are ADSL and SDSL different?
ADSL and SDSL are the two common forms of commercially available DSL. ADSL (Asymmetric Digital Subscriber Line) means that the upstream and downstream bandwidths differ. For most residential customers ADSL is advantageous because most traffic is downstream. SDSL (Symmetric Digital Subscriber Line) means that the upstream and downstream bandwidths are equal. SDSL is useful for commercial applications, such as web servers, where there is a significant upstream traffic.