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</p><p>In <a href="Information_technology" title="Information technology">information technology</a>, a <b>trailer</b> or <b>footer</b> refers to supplemental <a href="Data" title="Data">data</a> (<a href="Metadata" title="Metadata">metadata</a>) placed at the end of a block of data being stored or transmitted, which may contain information for the handling of the data block, or simply mark the block's end.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>
</p><p>In data transmission, the data following the end of the <a href="Header_(computing)" title="Header (computing)">header</a> and preceding the start of the trailer is called the <a href="Payload_(computing)" title="Payload (computing)">payload</a> or body.
</p><p>It is vital that trailer composition follow a clear and unambiguous <a href="Specification" class="mw-redirect" title="Specification">specification</a> or <a href="File_format" title="File format">format</a>, to allow for <a href="Parsing" title="Parsing">parsing</a>. If a trailer is not removed properly, or part of the payload is removed thinking it is a trailer, it can cause confusion.
</p><p>The trailer contains information concerning the destination of a packet being sent over a network so for instance in the case of emails the destination of the email is contained in the trailer
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<div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2></div>
<ul><li>In data transfer, the <a href="OSI_model" title="OSI model">OSI model</a>'s <a href="Data_link_layer" title="Data link layer">data link layer</a> adds a trailer at the end of <a href="Frame_(networking)" title="Frame (networking)">frames</a> of the <a href="Encapsulation_(networking)" title="Encapsulation (networking)">data encapsulation</a>.</li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><cite id="CITEREFAmbarisha_MalladiM._Chandra_NaikSayyed_Nagul_Meera2013" class="citation journal cs1">Ambarisha Malladi; M. Chandra Naik; Sayyed Nagul Meera (2013). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20170309064912/https://pdfs.semanticscholar.org/d952/ce9228a9e8e898328867bc7c90eb4b085d44.pdf">"Enhanced Packet Delivery Techniques Using Crypto-Logic on Jamming Attacks for Wireless Communication Medium"</a> <span class="cs1-format">(PDF)</span>. <i>International Journal of Computer & Organization Trends</i>. <b>3</b> (4): 109. <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/2249-2593">2249-2593</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:18200687">18200687</a>. Archived from <a rel="nofollow" class="external text" href="https://pdfs.semanticscholar.org/d952/ce9228a9e8e898328867bc7c90eb4b085d44.pdf">the original</a> <span class="cs1-format">(PDF)</span> on March 9, 2017.</cite></span>
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