In computer networking and computer science, digital bandwidth, network bandwidth or just bandwidth is a measure of available or consumed data communication resources expressed in bit/s or multiples of it (kbit/s, Mbit/s etc).

Bandwidth may refer to bandwidth capacity or available bandwidth in bit/s, which typically means the net bit rate, channel capacity or the maximum throughput of a logical or physical communication path in a digital communication system. For example, bandwidth test implies measuring the maximum throughput of a computer network. The reason for this usage is that according to Hartley's law, the maximum data rate of a physical communication link is proportional to its bandwidth in hertz, which is sometimes called frequency bandwidth, radio bandwidth or analog bandwidth, the last especially in computer networking literature.

Bandwidth may also refer to consumed bandwidth (bandwidth consumption), corresponding to achieved throughput or goodput, i.e. average data rate of successful data transfer through a communication path. This meaning is for example used in expressions such as bandwidth shaping, bandwidth management, bandwidth throttling, bandwidth cap, bandwidth allocation (for example bandwidth allocation protocol and dynamic bandwidth allocation), etc. An explanation to this usage is that digital bandwidth of a bit stream is proportional to the average consumed signal bandwidth in Hertz (the average spectral bandwidth of the analog signal representing the bit stream) during a studied time interval.

Digital bandwidth may also refer to: average bitrate (ABR) after multimedia data compression (source coding), defined as the total amount of data divided by the playback time.

Some authors prefer less ambiguous terms such as gross bit rate, net bit rate, channel capacity and throughput, to avoid confusion between digital bandwidth in bits per second and analog bandwidth in hertz.

http://en.wikipedia.org/wiki/Bandwidth_(computing)

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