Network throughput: Difference between revisions

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{{Short description|Rate at which data is processed in communication networks}}

{{Redirect-distinguish|Throughput|Throughput (disk drive)|Throughput (business)}}

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'''<span lang="EN">Network</span> throughput''' (or just '''throughput''', when in context) refers to the rate of message delivery over a [[Communications of the Channel Islands|communication channel]] in a [[communication network]], such as [[EtherNet/IP|Ethernet]] or [[packet radio]]. The data that these messages contain may be delivered over physical or logical links, or through [[network nodes]]. Throughput is usually measured in [[bits per second]] ({{nowrap|bit/s}}, sometimes abbreviated bps), and sometimes in '''packets per second''' ({{nowrap|p/s}} or pps) or data packets per [[time-division multiplexing|time slot]].

The '''system throughput''' or '''aggregate throughput''' is the sum of the data rates that are delivered over all channels in a network.<ref>[[Guowang Miao]], Jens Zander, K-W Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, {{ISBN|1107143217}}, 2016.</ref> Throughput represents [[Bandwidth (computing)|digital bandwidth]] consumption.

The throughput of a communication system may be affected by various factors, including the limitations of the underlying physical medium, available processing power of the system components, [[end-user]] behavior, etc. When taking various [[protocol overheadsoverhead]]s into account, the useful rate of the data transfer can be significantly lower than the maximum achievable throughput; the useful part is usually referred to as [[goodput]].

==Maximum throughput==

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===Maximum sustained throughput===

Maximum sustained throughput is the throughput averaged or integrated over a long time. For networks under constant load, this is likely to be the most accurate indicator of system performance. The maximum throughput is defined as the [[asymptotic throughput]] when the load is large. In [[packet-switched network]]s while [[packet loss]] is not occurring, the load and the throughput always are equal. The maximum throughput may be defined as the minimum load in {{nowrap|bit/s}} that causes [[packet loss]] or causes the latency to become unstable and increase towards infinity.<!--[[User:Kvng/RTH]]-->

==Channel utilization and efficiency==

Throughput is sometimes normalized and measured in percentage, but normalization may cause confusion regarding what the percentage is related to. ''Channel utilization'', ''channel efficiency'' and ''[[Packet loss|packet drop rate]]'' in percentage are less ambiguous terms.

The channel efficiency, also known as [[bandwidth utilization efficiency]], is the percentage of the [[net bit rate]] (in {{nowrap|bit/s}}) of a digital [[communication channel]] that goes to the actually achieved throughput. For example, if the throughput is {{nowrap|70 Mbit/s}} inover a {{nowrap|100 Mbit/s}} Ethernet connection, the channel efficiency is 70%. In this example, effectively 70&nbsp;Mbit of data are transmitted every second.

Channel utilization isincludes instead a term related to the use of the channel, disregarding the throughput. It counts not only withboth the data bits, butand alsothe with thetransmission overhead that makes use ofin the channel. The transmission overhead consists of preamble sequences, frame headers and acknowledgeacknowledgment packets. The definitions assume a noiseless channel. Otherwise, the throughput would not be only associated with the nature (efficiency) of the protocol, but also to retransmissions resultant from the quality of the channel. In a simplistic approach, channel efficiency can be equal to channel utilization assuming that acknowledge packets are zero-length and that the communications provider will not see any bandwidth relative to retransmissions or headers. Therefore, certain texts mark a difference between channel utilization and protocol efficiency.

In a point-to-point or [[point-to-multipoint communication]] link, where only one terminal is transmitting, the maximum throughput is often equivalent to or very near the physical data rate (the [[channel capacity]]), since the channel utilization can be almost 100% in such a network, except for a small [[inter-frame gap]].

For example, the maximum frame size in Ethernet is 1526 bytes: up to 1500 bytes for the payload, eight bytes for the preamble, 14 bytes for the header, and 4 bytes for the trailer. An additional minimum interframe gap corresponding to 12 bytes is inserted after each frame. This corresponds to a maximum channel utilization of 1526&nbsp;/ (1526&nbsp;+ 12)&nbsp;× 100%&nbsp;= 99.22%, or a maximum channel use of {{nowrap|99.22 Mbit/s}} inclusive of Ethernet datalink layer protocol overhead inover a {{nowrap|100 Mbit/s}} Ethernet connection. The maximum throughput or channel efficiency is then 1500&nbsp;/ (1526&nbsp;+ 12)&nbsp;= 97.5%, exclusive of the Ethernet protocol overhead.<!--[[User:Kvng/RTH]]-->

==Factors affecting throughput==