Bandwidth (computing)

In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth,[1] data bandwidth,[2] or digital bandwidth.[3][4]

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.

However, 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

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 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 plus implementation overhead.

Asymptotic bandwidth

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.[5]

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.[6]

Multimedia bandwidth

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.

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

56 kbit/s Modem / Dialup
1.5 Mbit/s ADSL Lite
1.544 Mbit/s T1/DS1
2.048 Mbit/s E1 / E-carrier
4 Mbit/s ADSL1
10 Mbit/s Ethernet
11 Mbit/s Wireless 802.11b
24 Mbit/s ADSL2+
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
1.3 Gbit/s Wireless 802.11ac
2.5 Gbit/s OC48
5 Gbit/s USB 3.0
7 Gbit/s Wireless 802.11ad
9.6 Gbit/s OC192
10 Gbit/s 10 Gigabit Ethernet, USB 3.1
40 Gbit/s Thunderbolt 3
100 Gbit/s 100 Gigabit Ethernet

References

  1. ^ Douglas Comer, Computer Networks and Internets, page 99 ff, Prentice Hall 2008.
  2. ^ Fred Halsall, to data+communications and computer networks, page 108, Addison-Wesley, 1985.
  3. ^ Cisco Networking Academy Program: CCNA 1 and 2 companion guide, Volym 1–2, Cisco Academy 2003
  4. ^ Behrouz A. Forouzan, Data communications and networking, McGraw-Hill, 2007
  5. ^ Chou, C. Y.; et al. (2006). "Modeling Message Passing Overhead". In Chung, Yeh-Ching; Moreira, José E. (eds.). Advances in Grid and Pervasive Computing: First International Conference, GPC 2006. pp. 299–307. ISBN 3540338098.
  6. ^ "What is Bandwidth? - Definition and Details". www.paessler.com. Retrieved 2019-04-18.
Bandwidth

Bandwidth has several related meanings:

Bandwidth (signal processing) or analog bandwidth, frequency bandwidth or radio bandwidth, a measure of the width of a range of frequencies, measured in hertz

Bandwidth (computing), the rate of data transfer, bit rate or throughput, measured in bits per second (bit/s)

Spectral linewidth, the width of an atomic or molecular spectral line, measured in HertzBandwidth may also refer to:

Bandwidth (company), an American communications provider

Bandwidth (linear algebra), the width of the non-zero terms around the diagonal of a matrix

In statistics kernel density estimation, the width of the convolution kernel used

In language expectancy theory, a normative expected range of linguistic behavior

In business jargon, the resources needed to complete a task or project

Bandwidth (radio program), a Canadian radio program

Graph bandwidth, in graph theory

Coherence bandwidth, a frequency range over which a channel can be considered "flat"

Power bandwidth of an amplifier, a frequency range for which power output exceeds a given fraction of full rated power

Bandwidth (signal processing)

Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. It is typically measured in hertz, and depending on context, may specifically refer to passband bandwidth or baseband bandwidth. Passband bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum. Baseband bandwidth applies to a low-pass filter or baseband signal; the bandwidth is equal to its upper cutoff frequency.

Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel.

A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the frequency spectrum. For example, a 3 kHz band can carry a telephone conversation whether that band is at baseband (as in a POTS telephone line) or modulated to some higher frequency.

Bit rate

In telecommunications and computing, bit rate (bitrate or as a variable R) is the number of bits that are conveyed or processed per unit of time.The bit rate is quantified using the bits per second unit (symbol: "bit/s"), often in conjunction with an SI prefix such as "kilo" (1 kbit/s = 1,000 bit/s), "mega" (1 Mbit/s = 1,000 kbit/s), "giga" (1 Gbit/s = 1,000 Mbit/s) or "tera" (1 Tbit/s = 1000 Gbit/s). The non-standard abbreviation "bps" is often used to replace the standard symbol "bit/s", so that, for example, "1 Mbps" is used to mean one million bits per second.

In most environments, one byte per second (1 B/s) corresponds to 8 bit/s.

Channel capacity

Channel capacity, in electrical engineering, computer science and information theory, is the tight upper bound on the rate at which information can be reliably transmitted over a communication channel.

Following the terms of the noisy-channel coding theorem, the channel capacity of a given channel is the highest information rate (in units of information per unit time) that can be achieved with arbitrarily small error probability. Information theory, developed by Claude E. Shannon during World War II, defines the notion of channel capacity and provides a mathematical model by which one can compute it. The key result states that the capacity of the channel, as defined above, is given by the maximum of the mutual information between the input and output of the channel, where the maximization is with respect to the input distribution. The notion of channel capacity has been central to the development of modern wireline and wireless communication systems, with the advent of novel error correction coding mechanisms that have resulted in achieving performance very close to the limits promised by channel capacity.

Data signaling rate

In telecommunication, data signaling rate (DSR), also known as gross bit rate, is the aggregate rate at which data pass a point in the transmission path of a data transmission system.

Ilkposta

ilkposta is a free webmail service, located in Istanbul, Turkey. The service started as a research and development (R&D) project in 2001. This project primarily intended to decrease E-mail spams in users' inbox. Secondary focus given on user experience for providing better server responsiveness where bandwidth (computing) is a profound issue.

Perl based open-source software, Open WebMail is used in server side, for the purpose of simplicity.

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