Home  Why ADSL?  The protocol stacks  References   Why ADSL? The growth in Internet usage and demand for wider bandwidth have led to improvement of the technologies of the Internet's WANs and LANs and enable them to transmit data at very high bit rates.  Even so, these improvements have not significantly affected the home end users' throughput. The problem lies at the connection between the Internet Service Providers (ISP) and the end users, also known as The Last Mile. The first dial up modems based on twisted pair phone lines served as the first last mile solution. They utilized the existing wide-spreading infrastructure that reaches every home, but its limited bit-rate transmission had created a bottle neck. Different last mile solutions were suggested instead, such as deploying an optical fibers infrastructure, but they turned out to be very expensive and difficult.  ADSL technology enables high-speed transmission over the existing copper telephone lines (twisted pair). Moreover, while previous solutions (such as ISDN or analog modems) require exclusive use of the line, making it unusable for phone calls, ADSL enables the usage of one line for both purposes at the same time. You can either examine the protocol stacks by clicking on the "protocol stacks" link above, or you can follow the journey of Grandma's recipe from her host at home through ADSL to the Internet by starting with Grandma's home computer - click on it to your right. It's the top left device. Network Components