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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Arbitration Interframe Space</span></h1>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="fr" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="fr" dir="ltr"><p>L'<b>Arbitration Interframe Space (AIFS)</b> est l'un des intervalles inter-trames utilisé par les réseaux <a href="R%C3%A9seau_sans_fil" title="Réseau sans fil">WLAN</a> de la norme <a href="IEEE_802.11" title="IEEE 802.11">IEEE 802.11</a>. Il représente la durée écoulée entre deux transmission de trames et se fonde sur le mode <i><span class="lang-en" lang="en">Enhanced Distributed Channel Access</span></i> (<a href="Enhanced_Distributed_Channel_Access_Function" title="Enhanced Distributed Channel Access Function">EDCA</a>) de l'amendement <a href="IEEE_802.11e" title="IEEE 802.11e">IEEE 802.11e</a>. L'AIFS peut alors avoir une valeur différente en fonction des catégories de trafic (TC), ce qui permet une priorisation différente des trames en fonction des applications. Par exemple, un AIFS court permettra de raccourcir le temps entre deux trames, ce qui est favorisé dans le cas d'une application sensible à la <a href="Gigue_(informatique)" title="Gigue (informatique)">gigue</a>, comme la <a href="VoIP" class="mw-redirect" title="VoIP">VoIP</a> ou le <span class="lang-en" lang="en"><a href="Streaming" title="Streaming">streaming</a></span> en temps réel.
La valeur de l'AIFS dépend de la catégorie de trafic (<span class="lang-en" lang="en">access category</span>), représentée par l'AIFSN (AIFS Number). Il est calculé de la manière suivante :
</p><p><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {AIFS} =(\mathrm {AIFSN[AC]} \times {\text{Dur}}\mathrm {\acute {e}} {\text{e d'un slot}})+}">
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<mtext>Dur</mtext>
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<mtext>e d'un slot</mtext>
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<annotation encoding="application/x-tex">{\displaystyle \mathrm {AIFS} =(\mathrm {AIFSN[AC]} \times {\text{Dur}}\mathrm {\acute {e}} {\text{e d'un slot}})+}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1001bf3ce398419f0faa38def9fb6ec0a4d3859f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:42.291ex; height:2.843ex;" alt="{\displaystyle \mathrm {AIFS} =(\mathrm {AIFSN[AC]} \times {\text{Dur}}\mathrm {\acute {e}} {\text{e d'un slot}})+}" loading="lazy"></span><a href="Intervalle_inter-trame_court" title="Intervalle inter-trame court"><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \color {Blue}\mathrm {SIFS} }">
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<annotation encoding="application/x-tex">{\displaystyle \color {Blue}\mathrm {SIFS} }</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/50bd2780383363059dd5e31df82b253b1a2d4437.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:4.942ex; height:2.176ex;" alt="{\displaystyle \color {Blue}\mathrm {SIFS} }" loading="lazy"></span></a><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>L'AIFS est toujours au moins égal au <a href="DCF_Interframe_Space" title="DCF Interframe Space">DIFS</a>.
</p><p>Les AIFSN peuvent être définis par le point d'accès, dans le paramètre EDCA des trames de <i>beacon</i> et de <i>probe response</i>. Dans le cas contraire, la station doit utiliser les valeurs par défaut définies dans la norme <a href="IEEE_802.11" title="IEEE 802.11">IEEE 802.11</a> :
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<table class="wikitable">
<tbody><tr>
<th><span class="lang-en" lang="en">Access category</span>
</th>
<th>AIFSN
</th></tr>
<tr>
<td><span class="lang-en" lang="en">Background</span> (BK)
</td>
<td>7
</td></tr>
<tr>
<td><span class="lang-en" lang="en">Best Effort</span> (BE)
</td>
<td>3
</td></tr>
<tr>
<td><span class="lang-en" lang="en">Video</span> (VI)
</td>
<td>2
</td></tr>
<tr>
<td><span class="lang-en" lang="en">Voice</span> (VO)
</td>
<td>2
</td></tr></tbody></table>
<div class="mw-heading mw-heading2"><h2 id="Références"><span id="R.C3.A9f.C3.A9rences"></span>Références</h2></div>
<div class="references-small decimal" style=""><div class="mw-references-wrap"><ol class="references">
<li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a> </span><span class="reference-text"><span class="ouvrage">« <a rel="nofollow" class="external text" href="http://standards.ieee.org/getieee802/download/802.11-2012.pdf"><cite style="font-style:normal;">Norme IEEE 802.11-2012</cite></a> », sur <span class="italique">standards.ieee.org</span> <small style="line-height:1em;">(consulté le <time class="nowrap" datetime="2015-09-09" data-sort-value="2015-09-09">9 septembre 2015</time>)</small></span></span>
</li>
</ol></div>
</div>
<div class="mw-heading mw-heading2"><h2 id="Voir_aussi">Voir aussi</h2></div>
<div class="mw-heading mw-heading3"><h3 id="Articles_connexes">Articles connexes</h3></div>
<ul><li>SIFS - <a href="Intervalle_inter-trame_court" title="Intervalle inter-trame court">Short Interframe Space</a></li>
<li>RIFS - <a href="Reduced_Interframe_Space" title="Reduced Interframe Space">Reduced Interframe Space</a></li>
<li>PIFS - <a href="PCF_Interframe_Space" title="PCF Interframe Space">PCF Interframe Space</a></li>
<li>EIFS - <a href="Extended_Interframe_Space" title="Extended Interframe Space">Extended Interframe Space</a></li>
<li>PCF - <a href="Point_Coordinated_Function" title="Point Coordinated Function">Point Coordination Function</a></li>
<li>DCF - <a href="Distributed_Coordination_Function" title="Distributed Coordination Function">Distributed Coordination Function</a></li>
<li>EDCAF - <a href="Enhanced_Distributed_Channel_Access_Function" title="Enhanced Distributed Channel Access Function">Enhanced Distributed Channel Access Function</a></li>
<li><a href="IEEE_802.11e" title="IEEE 802.11e">IEEE 802.11e</a></li></ul>
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