In computing, bandwidth
is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth
, data bandwidth
or digital bandwidth
This definition of bandwidth
is in contrast to the field of signal processing, wireless communications, modem data transmission, digital communications
, and electronics
, in which bandwidth
is used to refer to analog signal bandwidth
measured in hertz
, meaning the frequency range between lowest and highest attainable frequency while meeting a well-defined impairment level in signal power. The actual bit rate that can be achieved depends not only on the signal bandwidth but also on the noise on the channel.
Network bandwidth capacity
The term bandwidth
sometimes defines the net bit rate
'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 maximum rate that can be sustained on a link are limited by the Shannon–Hartley channel capacity
for these communication systems, which is dependent on the bandwidth
in hertz and the noise on the channel.
Network bandwidth consumption
may be confused with useful data throughput (or goodput
). For example, 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, much internet traffic uses the transmission control protocol
(TCP), which requires a three-way handshake for each transaction. Although in many modern implementations the protocol is efficient, it does add significant overhead compared to simpler protocols. Also, data packets may be lost, which further reduces the useful data throughput. In general, for any effective digital communication, a framing protocol is needed; overhead and effective throughput depends on implementation. Useful throughput is less than or equal to the actual channel capacity minus implementation overhead.
The asymptotic bandwidth
(formally asymptotic throughput
) for a network is the measure of maximum throughput
for a greedy source
, for example when the message size (the number of packets per second from a source) approaches close to the maximum amount.
Asymptotic bandwidths are usually estimated by sending a number of very large messages through the network, measuring the end-to-end throughput. As other bandwidths, the asymptotic bandwidth is measured in multiples of bits per seconds. Since bandwidth spikes can skew the measurement, carriers often use the 95th percentile
method. This method continuously measures bandwidth usage and then removes the top 5 percent.
Due to the impractically high bandwidth requirements of uncompressed digital media
, the required multimedia bandwidth can be significantly reduced with data compression.
The most widely used data compression technique for media bandwidth reduction is the discrete cosine transform
(DCT), which was first proposed by Nasir Ahmed
in the early 1970s.
DCT compression significantly reduces the amount of memory and bandwidth required for digital signals, capable of achieving a data compression ratio
of up to 100:1 compared to uncompressed media.
Bandwidth in web hosting
In Web hosting service
, the term bandwidth
is often incorrectly used to describe the amount of data transferred to or from the website or server within a prescribed period of time, for example bandwidth consumption accumulated over a month
measured in gigabytes per month.
The more accurate phrase used for this meaning of a maximum amount of data transfer each month or given period is monthly data transfer
A similar situation can occur for end user ISPs as well, especially where network capacity is limited (for example in areas with underdeveloped internet connectivity and on wireless networks).
Internet connection bandwidth
This table shows the maximum bandwidth (the physical layer net bitrate
) of common Internet access technologies. For more detailed lists see
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Last edited on 27 January 2021, at 19:16
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