In computer networking and computer science, bandwidth,[1] network bandwidth,[2] data bandwidth,[3] or digital bandwidth[4][5] is a measure of available or consumed data communication resources expressed in bits/second or multiples of it (kilobits/s, megabits/s etc.).
Note that in textbooks on wireless communications, modem data transmission, digital communications, electronics, etc., bandwidth refers to analog signal bandwidth measured in hertz—the original meaning of the term. Some computer networking authors prefer less ambiguous terms such as bit rate, channel capacity and throughput rather than bandwidth in bit/s, to avoid this confusion.
Contents |
In computer networking, bandwidth in bit/s sometimes means the net bit rate (also known as 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.
In computer networking, 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 expressions 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.
Digital bandwidth may also refer to: multimedia bit rate or average bitrate after multimedia data compression (source coding), defined as the total amount of data divided by the playback time.
In website hosting, 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..
This table shows the maximum bandwidth (the physical layer net bitrate) of common Internet access technologies. For a more detailed list see list of device bandwidths, bit rate progress trends and list of bit rates in multimedia.
| 56 kbit/s | Modem / Dialup |
| 1.5 Mbit/s | ADSL Lite |
| 1.544 Mbit/s | T1/DS1 |
| 10 Mbit/s | Ethernet |
| 11 Mbit/s | Wireless 802.11b |
| 44.736 Mbit/s | T3/DS3 |
| 54 Mbit/s | Wireless 802.11g |
| 100 Mbit/s | Fast Ethernet |
| 155 Mbit/s | OC3 |
| 600 Mbit/s | Wireless 802.11n |
| 622 Mbit/s | OC12 |
| 1 Gbit/s | Gigabit Ethernet |
| 2.5 Gbit/s | OC48 |
| 9.6 Gbit/s | OC192 |
| 10 Gbit/s | 10 Gigabit Ethernet |
| 100 Gbit/s | 100 Gigabit Ethernet |