Upstream

Upstream, or the speed at which data can be transferred from the client to the server (uploading), differs greatly from downstream not only in theory and usage, but also in that upstream speeds are usually at a premium. Whereas downstream is important to the average home user for purposes of downloading content, uploads are used mainly for web server applications and similar processes where the sending of data is critical. ADSL and Cable modems are asynchronous, thereby rendering the upstream speed to be much lower than that of its downstream. Synchronous connections such as SDSL and T1, however, offer identical upstream and downstream speeds.

See also: downstream