High-speed dialup is a feature provided by Internet service providers to speed up dialup connections using a special server called an acceleration server. An acceleration server acts as a channel of transfer between a Web page and a user’s dialup connection. By selectively compressing, filtering and caching the data, the acceleration server speeds up the process of loading a Web page.
For a common Internet user, high-speed dialup can make a dialup connection up to five times faster. Although broadband has largely replaced dialup Internet connections, a small percentage of Internet users in the U.S. still rely on it, particularly in rural areas.
Techopedia explains High-Speed Dialup
As soon the requested data arrives, the acceleration server caches the page and compresses the data received. Next, it filters out any pop-up ads before passing the Web page and its contents to the dialup user. This effectively increases the speed for the user. HTML text and other Web page markup that is compressed on the fly is then decompressed as it reaches the Web page.