Bandwidth (computing)
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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 or the maximum throughput of a logical or physical communication path in a digital communication system. 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 "analog bandwidth" in computer networking literature.
Bandwidth may also refer to consumed bandwidth (bandwidth consumption), corresponding to acheived 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 tests, bandwidth shaping, bandwidth management, bandwidth throttling, bandwidth cap, bandwidth allocation (for example bandwidth allocation protocol and dynamic bandwidth allocation), etc. For references supporting this usage, see these articles. 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 bandwith of the analog signal representing the bit stream) during a studied time interval.
Digital bandwidth may also refer to average bitrate after multimedia data compression (source coding), defined as the total amount of data divided by the playback time.
Some authors prefer less ambiguos 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.
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[edit] Bandwidth in web hosting
In website hosting, the term "bandwidth" is often used to describe the amount of data transferred to or from the website or server within a prescribed period of time. Another more specific phrase used for this meaning of bandwidth is monthly data transfer.
Web hosting companies often quote a monthly bandwidth limit for a website, for example 500 gigabytes per month. If the total amount of data downloaded from the website in a particular month reaches this limit, the hosting company may shut off further public access to the site.
When a website grows in popularity or exceeds its bandwidth limits, webmasters may reduce bandwidth usage by employing bandwidth optimization techniques.
[edit] Internet connection bandwidths
Below is a table showing the maximum bandwidth of different connection types to the internet:
| 56 kbit/s | Modem / Dialup |
| 1.544 Mbit/s | T1 |
| 10 Mbit/s | Ethernet |
| 11 Mbit/s | Wireless 802.11b |
| 43.232 Mbit/s | T3 |
| 54 Mbit/s | Wireless-G 802.11g |
| 100 Mbit/s | Fast Ethernet |
| 155 Mbit/s | OC3 |
| 300 Mbit/s | Wireless-N 802.11n |
| 622 Mbit/s | OC12 |
| 1000 Mbit/s | Gigabit Ethernet |
| 2.5 Gbit/s | OC48 |
| 9.6 Gbit/s | OC192 |
| 10 Gbit/s | 10 Gigabit Ethernet |
[edit] See also
- Bandwidth (Wiktionary entry)
- Bandwidth cap
- Bandwidth extension
- Bandwidth test
- Bandwidth theft
- Bit rate
- Broadband
- Comparison of latency and throughput
- Goodput
- List of device bandwidths
- Measuring network throughput
- Narrowband
- Signal processing
- Throughput
