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---
title: UDP (User Datagram Protocol)
slug: Glossary/UDP
translation_of: Glossary/UDP
---
<p><strong>UDP </strong>(User Datagram Protocol) is a long standing {{glossary("protocol")}} used together with {{glossary("IPv6","IP")}} for sending data when transmission speed and efficiency matter more than security and reliability.</p>
<p>UDP uses a simple <a href="https://en.wikipedia.org/wiki/Connectionless_communication" title="Connectionless communication">connectionless communication</a> model with a minimum of protocol mechanism. UDP provides <a href="https://en.wikipedia.org/wiki/Checksum" title="Checksum">checksums</a> for data integrity, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Port_numbers" title="Port numbers">port numbers</a> for addressing different functions at the source and destination of the datagram. It has no <a href="https://en.wikipedia.org/wiki/Handshaking" title="Handshaking">handshaking</a> dialogues, and thus exposes the user's program to any <a href="https://en.wikipedia.org/wiki/Reliability_(computer_networking)" title="Reliability (computer networking)">unreliability</a> of the underlying network; There is no guarantee of delivery, ordering, or duplicate protection. If error-correction facilities are needed at the network interface level, an application may use the <a href="https://en.wikipedia.org/wiki/Transmission_Control_Protocol" title="Transmission Control Protocol">Transmission Control Protocol</a> (TCP) or <a href="https://en.wikipedia.org/wiki/Stream_Control_Transmission_Protocol" title="Stream Control Transmission Protocol">Stream Control Transmission Protocol</a> (SCTP) which are designed for this purpose.</p>
<p>UDP is suitable for purposes where error checking and correction are either not necessary or are performed in the application; UDP avoids the overhead of such processing in the <a href="https://en.wikipedia.org/wiki/Protocol_stack" title="Protocol stack">protocol stack</a>. Time-sensitive applications often use UDP because dropping packets is preferable to waiting for packets delayed due to <a href="https://en.wikipedia.org/wiki/Retransmission_(data_networks)" title="Retransmission (data networks)">retransmission</a>, which may not be an option in a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Real-time_system" title="Real-time system">real-time system</a>.</p>
<h3 id="一般知識">一般知識</h3>
<ul>
<li>Wikipedia の {{Interwiki("wikipedia", "User Datagram Protocol")}} </li>
</ul>
<h3 id="技術リファレンス">技術リファレンス</h3>
<ul>
<li><a href="http://tools.ietf.org/html/rfc768">Specification</a></li>
</ul>
<ul>
</ul>
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