Upstream (Softwareentwicklung)
The word upstream has several meanings in the field of computer science.
Software Development
Upstream in software development refers to a direction toward the original authors or maintainers of software that is distributed as source code, and is a qualification of either a bug or a patch. A patch sent upstream, i.e. offered to the original authors or maintainers of the software the patch applies to, would be targeted at being included in (a future release of) the original software instead of being maintained by a distribution's maintainer of said software. This would allow other distributions to benefit from it when they pick up the future release. The term also pertains to bugs - responsibility for a bug is said to lie upstream when it is not caused through the distribution's porting and integration efforts.
Networking
Another use of the word refers to the speed at which data can be transferred from the client to the server (uploading). This 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. Upstream speeds are also important to users of P2P software.
ADSL and Cable modems are asymmetric, thereby rendering the upstream speed to be much lower than that of its downstream. Symmetric connections such as SDSL and T1, however, offer identical upstream and downstream speeds.
If a node A on the Internet is closer (fewer hops away) to the Internet backbone than a node B, then A is said to be upstream of B or conversely, B is downstream of A. Related to this is the idea of upstream providers. An upstream provider is usually a large ISP that provides Internet access to a local ISP. Hence, the word upstream also refers to the data connection between two ISPs.
See also: Downstream