Automatic repeat request

<h2 id="examples">Examples</h2>
<p>The <a href="/facts/Transmission_Control_Protocol/WW4sPrt9">Transmission Control Protocol</a> uses a variant of <a href="/facts/Go-Back-N_ARQ/GyblPqaN">Go-Back-N ARQ</a> to ensure reliable transmission of data over the <a href="/facts/Internet_Protocol/Qq6VeEal">Internet Protocol</a>, which does not provide guaranteed delivery of packets; with Selective Acknowledgement (SACK), it uses <a href="/facts/Selective_Repeat_ARQ/cuMB31b5">Selective Repeat ARQ</a>.
</p><p><a href="/facts/IEEE_802.11/ryEGu6Vq">IEEE 802.11</a> wireless networking uses ARQ retransmissions at the data-link layer.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a>
</p><p><a href="/facts/ITU-T_G.hn/Tf9P5x7s">ITU-T G.hn</a> uses <a href="/facts/Hybrid_automatic_repeat_request/tlFUMWfQ">hybrid ARQ</a>, a mixture of high-rate <a href="/facts/Forward_error_correction/cLUTUJrA">forward error correction</a> (FEC) and ARQ. It is a high-speed <a href="/facts/Local_area_network/edUDxJ6J">local area network</a> standard that can operate at data rates up to 1 Gbit/s over existing home wiring (<a href="/facts/Power_line_communication/y0QpHy0V">power lines</a>, phone lines and <a href="/facts/Ethernet_over_coax/MYXFbf0C">coaxial cables</a>). G.hn uses <a href="/facts/CRC-32C/u2exo4sv">CRC-32C</a> for Error Detection, <a href="/facts/Low-density_parity-check_code/yPYHEKAP">LDPC</a> for FEC and selective repeat for ARQ.
</p><p>ARQ systems are widely used on shortwave radio to ensure reliable delivery of data such as for telegrams.  These systems came in forms called <a href="/facts/ARQ-E/LJhDJrdj">ARQ-E</a> and <a href="/facts/ARQ-M/ssKMtKdY">ARQ-M</a>, which also included the ability to multiplex two or four channels.
</p><p>A number of patents exist for the use of ARQ in live video contribution environments. In these high throughput environments negative acknowledgements are used to drive down overheads.
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Hybrid_automatic_repeat_request/tlFUMWfQ">Hybrid automatic repeat request</a></li></ul>

<ul><li>Peterson and Davie, <i>Computer Networks: A Systems Approach</i>, Third Edition, 2003</li>
<li>RFC <a href="https://www.rfc-editor.org/rfc/rfc3366">3366</a> - Advice to link designers on link Automatic Repeat reQuest (ARQ)</li>
<li><a href="https://web.archive.org/web/20160304032149/http://www.techex.co.uk/other/arq-video-packet-resend">Negative acknowledgement ARQ</a> for live video</li>
<li> This article incorporates <a href="/facts/Copyright_status_of_works_by_the_federal_government_of_the_United_States/Q1jvr96g">public domain material</a> from <a href="https://web.archive.org/web/20220122224547/https://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm"><i>Federal Standard 1037C</i></a>. <a href="/facts/General_Services_Administration/Np3opv9x">General Services Administration</a>. Archived from <a href="https://www.its.bldrdoc.gov/fs-1037/fs-1037c.htm">the original</a> on January 22, 2022. (in support of <a href="/facts/MIL-STD-188/D5rsvdsW">MIL-STD-188</a>).</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"802.11 Reference Design: Recovery Procedures and Retransmit Limits". Retrieved July 21, 2020. <a href="https://warpproject.org/trac/wiki/802.11/MAC/Lower/Retransmissions" target="_blank">https://warpproject.org/trac/wiki/802.11/MAC/Lower/Retransmissions</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
</ol>

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Automatic repeat request