Amount of data that can be transferred in a given unit of time.

Network bandwidth capacity

Bandwidth sometimes defines the net bit rate (aka. peak bit rate, information rate or physical layer useful bit rate), channel capacity, or the maximum throughput of a logical or physical communication path in a digital communication system. For example, bandwidth tests measure 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, spectral bandwidth, RF bandwidth, signal bandwidth or analog bandwidth.

Network bandwidth consumption

Bandwidth in bit/s may also refer to consumed bandwidth, corresponding to achieved throughput or goodput, i.e., the average rate of successful data transfer through a communication path. This sense applies to concepts and technologies such as bandwidth shaping, bandwidth management, bandwidth throttling, bandwidth cap, bandwidth allocation (for example bandwidth allocation protocol and dynamic bandwidth allocation), etc. A bit stream's bandwidth 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.

Channel bandwidth may be confused with data throughput. A channel with x bps may not necessarily transmit data at x rate, since protocols, encryption, and other factors can add appreciable overhead. For instance, a lot of internet traffic uses the transmission control protocol (TCP) which requires a three-way handshake for each transaction, which, though in many modern implementations is efficient, does add significant overhead compared to simpler protocols. In general, for any effective digital communication, a framing protocol is needed; overhead and effective throughput depends on implementation. Actual throughput is less than or equal to the actual channel capacity plus implementation overhead.