In telecommunications or computer networks , downstream describes the direction of the data flow from the source to the consumer. Complementary to this, upstream describes the opposite direction. The term is used both as a directional adjective and as a proportion of the available bandwidth as a noun .
The use of computer networks is often the answering of inquiries and thus the supply of data. This is expressed in the client-server concept . If these inquiries, measured by the amount of data or speed expectations , are in a strong imbalance to the answer on a network link , asymmetrical connection technologies are preferred for this network link. In the broadband connection of households this z. B. the connection technology Very High Speed Digital Subscriber Line (VDSL) or Asymmetric Digital Subscriber Line (ADSL) is used. The limiting bandwidth is divided unequally into downstream and upstream. This asymmetry varies depending on the standard used, for example in the ratio 10: 1 for ADSL over ISDN ( ITU-T G.992.1 Annex B ), i.e. H. 10 Mbit / s downstream and 1 Mbit / s upstream.
For the integration of companies in Wide Area Networks (WAN) such as the Internet or networking within companies, symmetrical use cases often arise, e.g. B. if the sending of data ( upload ) is more important. When using peer-to-peer applications, the central sources ( servers ) are relieved or dissolved by the consumers assuming this role by making a portion of their upstream bandwidth available to other consumers downstream .
- Andreas Bluschke, Michael Matthews, Reinhard Schiffel: access networks for telecommunications. Hanser, Munich 2004, p. 18.
- ITU-T G.992.1: Asymmetric digital subscriber line (ADSL) transceivers. 06-1999, p. 4.
- Gerd Siegmund: Technology of the networks. 5th edition, Hüthig, Heidelberg 2002, p. 216.
- Gerd Siegmund: Network technology. 5th edition, Hüthig, Heidelberg 2002, ISBN 3-8266-5021-2 .