Bandwidth on demand:

You use and pay for bandwidth only when you need it. This flexibility, offered by more and more ISPs, is usually related to a T-1 line and works well for growing companies that have high-volume connectivity needs that require the use of a full T-1 only during certain busy times.

High-demand needs might include Web and e-mail servers, active networks, large data and file transfers (including CAD/CAM files), multimedia applications (including video or image file transfers and online videoconferencing) and more.