ADSL offers unequal throughput speeds of up to 1.54 Mbps downstream from the carrier (download) and up to 384 kbps upstream (upload), while SDSL delivers equal speed increments (192 kbps, 384 kbps, 768 kbps, 1.1 Mbps, and 1.5 Mbps, both ways).
Availability is also slightly different for ADSL and SDSL. ADSL is typically offered over a wider area, up to 18,000 feet from the CO. SDSL normally falls within a tighter range, offered up to 6,000-8,000 feet from the LEC office.
