In computer networking and computer science

Computer science

Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

, bandwidth, network bandwidth, data bandwidth, or digital bandwidth 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

Modem

A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

 data transmission

Data transmission

Data transmission, digital transmission, or digital communications is the physical transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media...

, digital communications, electronics

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

, etc., bandwidth refers to analog signal bandwidth measured in hertz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

—the original meaning of the term. Some computer networking authors prefer less ambiguous terms such as bit rate

Bit rate

In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

, channel capacity

Channel capacity

In electrical engineering, computer science and information theory, channel capacity is the tightest upper bound on the amount of information that can be reliably transmitted over a communications channel...

and throughput

Throughput

In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...

rather than bandwidth in bit/s, to avoid this confusion.

Network bandwidth capacity

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

Channel capacity

In electrical engineering, computer science and information theory, channel capacity is the tightest upper bound on the amount of information that can be reliably transmitted over a communications channel...

, 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

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 bandwidth, signal bandwidth or analog bandwidth.

Network bandwidth consumption

In computer networking, bandwidth in bit/s may also refer to consumed bandwidth, corresponding to achieved throughput

Throughput

In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...

 or goodput

Goodput

In computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...

, 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 management

Bandwidth management is the process of measuring and controlling the communications on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance of the network.- Management :Bandwidth management mechanisms may be...

, bandwidth throttling

Bandwidth throttling

Bandwidth throttling is a reactive measure employed in communication networks to regulate network traffic and minimize bandwidth congestion. Bandwidth throttling can occur at different locations on the network. On a local area network , a sysadmin may employ bandwidth throttling to help limit...

, bandwidth cap

Bandwidth cap

A bandwidth cap, also known as a bit cap, limits the transfer of a specified amount of data over a period of time. Internet service providers commonly apply a cap when a channel intended to be shared by many users becomes overloaded, or may be overloaded, by a few users...

, bandwidth allocation

Bandwidth allocation

Bandwidth allocation refers to how radio frequencies are assigned to different applications. The radio spectrum is a finite resource creating the need for an effective allocation process. In the United States, the Federal Communications Commission or FCC has the responsibility allocating the...

 (for example bandwidth allocation protocol

Bandwidth Allocation Protocol

The Bandwidth Allocation Protocol, along with its control protocol, the Bandwidth Allocation Control Protocol, is used to add and remove links in a multilink bundle over PPP, and specifying which peer is responsible for making decisions regarding bandwidth management...

 and dynamic bandwidth allocation

Dynamic bandwidth allocation

Dynamic bandwidth allocation is a technique by which traffic bandwidth in a shared telecommunications medium can be allocated on demand and fairly between different users of that bandwidth. This is a form of bandwidth management, and is essentially the same thing as statistical multiplexing...

), 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.

Multimedia bandwidth

Digital bandwidth may also refer to: multimedia bit rate or average bitrate

Average bitrate

Average bitrate refers to the average amount of data transferredper unit of time, usually measured per second. This is commonly referred to for digital music or video. An MP3 file, for example, that has an average bit rate of 128 kbit/s transfers, on average, 128,000 bits every second...

 after multimedia data compression

Data compression

In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

 (source coding

Source coding

In information theory, Shannon's source coding theorem establishes the limits to possible data compression, and the operational meaning of the Shannon entropy....

), defined as the total amount of data divided by the playback time.

Bandwidth in web hosting

In website hosting

Web hosting service

A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own or lease for use by their clients as well as providing Internet...

, 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..

Internet connection bandwidths

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 Digital Signal 1 Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...
10 Mbit/s	Ethernet Ethernet Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
11 Mbit/s	Wireless 802.11b
44.736 Mbit/s	T3/DS3 Digital Signal 3 A Digital Signal 3 is a digital signal level 3 T-carrier. It may also be referred to as a T3 line.*The data rate for this type of signal is 44.736 Mbit/s.*This level of carrier can transport 28 DS1 level signals within its payload....
54 Mbit/s	Wireless 802.11g
100 Mbit/s	Fast Ethernet Fast Ethernet In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the...
155 Mbit/s	OC3
600 Mbit/s	Wireless 802.11n
622 Mbit/s	OC12
1 Gbit/s	Gigabit Ethernet Gigabit Ethernet Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
2.5 Gbit/s	OC48
9.6 Gbit/s	OC192
10 Gbit/s	10 Gigabit Ethernet 10 Gigabit Ethernet The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
100 Gbit/s	100 Gigabit Ethernet 100 Gigabit Ethernet 40 Gigabit Ethernet, or 40GbE, and 100 Gigabit Ethernet, or 100GbE, are high-speed computer network standards developed by the Institute of Electrical and Electronics Engineers . They support sending Ethernet frames at 40 and 100 gigabits per second over multiple 10 Gbit/s or 25 Gbit/s lanes...

See also

• 92 Code
  92 Code
  The 92 Code was first adopted by Western Union in 1859. The reason for this adoption was to reduce bandwidth usage over the telegraph lines and speed transmissions by utilizing a numerical code system for various frequently used phrases....
  
  
• Bandwidth cap
  Bandwidth cap
  A bandwidth cap, also known as a bit cap, limits the transfer of a specified amount of data over a period of time. Internet service providers commonly apply a cap when a channel intended to be shared by many users becomes overloaded, or may be overloaded, by a few users...
  
  
• Bandwidth extension
  Bandwidth extension
  Bandwidth extension of signal is defined as the deliberate process of expanding the frequency range of a signal in which it contains an appreciable and useful content, and/or the frequency range in which its effects are such...
  
  
• Bandwidth hogging
  Bandwidth hogging
  A bandwidth hog is a derogatory term for a user of an internet connection who uses more bandwidth than other users on the network. ISPs now refer to bandwidth hogs as heavy users in an attempt to avoid backlash by the public....
  
  
• Bandwidth optimization
  Bandwidth optimization
  Bandwidth optimization is one of many concerns webmasters deal with when hosting web content. Since most web hosts charge by bandwidth used or have an account limit on bandwidth, a prudent webmaster will squeeze and compress their files as much as possible without affecting the content's integrity....
  
  
• Bandwidth test
• Bandwidth theft
• Bit rate
  Bit rate
  In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
  
  
• Broadband
  Broadband
  The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
  
  
• Comparison of latency and throughput
• Goodput
  Goodput
  In computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...
  
  
• List of device bandwidths
• Measuring network throughput
  Measuring network throughput
  Throughput of a network can be measured using various tools available on different platforms. This page explains the theory behind what these tools set out to measure and the issues regarding these measurements.-Reasons for measuring throughput in networks:...
  
  
• Narrowband
  Narrowband
  In radio, narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. It is a common misconception that narrowband refers to a channel which occupies only a "small" amount of space on the radio spectrum.The opposite of...
  
  
• Signal processing
  Signal processing
  Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time...
  
  
• Throughput
  Throughput
  In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...