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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Service Access Point</span></span>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p>A <b>Service Access Point</b> (<b>SAP</b>) is an identifying label for network endpoints used in <a href="Open_Systems_Interconnection" class="mw-redirect" title="Open Systems Interconnection">Open Systems Interconnection</a> (OSI) networking.
</p><p>The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. As an example, PD-SAP or PLME-SAP in <a href="IEEE_802.15.4" title="IEEE 802.15.4">IEEE 802.15.4</a> can be mentioned, where the <a href="Medium_access_control" title="Medium access control">medium access control</a> (MAC) layer requests certain services from the <a href="Physical_layer" title="Physical layer">physical layer</a>. Service access points are also used in <a href="IEEE_802.2" title="IEEE 802.2">IEEE 802.2</a> <a href="Logical_Link_Control" class="mw-redirect" title="Logical Link Control">Logical Link Control</a> in <a href="Ethernet" title="Ethernet">Ethernet</a> and similar <a href="Data_link_layer" title="Data link layer">data link layer</a> protocols.
</p><p>When using the OSI Network system (<a href="CONS" class="mw-redirect" title="CONS">CONS</a> or <a href="CLNS" class="mw-redirect" title="CLNS">CLNS</a>), the base for constructing an address for a network element is an <a href="NSAP_address" class="mw-redirect" title="NSAP address">NSAP address</a>, similar in concept to an <a href="IP_address" title="IP address">IP address</a>. OSI protocols as well as <a href="Asynchronous_Transfer_Mode" title="Asynchronous Transfer Mode">Asynchronous Transfer Mode</a> (ATM) can use Transport (TSAP), Session (SSAP) or Presentation (PSAP) Service Access Points to specify a destination address for a connection. These SAPs consist of NSAP addresses combined with optional transport, session and presentation selectors, which can differentiate at any of the three layers between multiple services at that layer provided by a network element.
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<p><a href="IEEE_802" title="IEEE 802">IEEE 802</a>'s reference model (RM) guarantees the following SAPs:<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>
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<ul><li>LSAP - <a href="Link_layer" title="Link layer">Link</a></li>
<li>MSAP - <a href="Media_access_control" class="mw-redirect" title="Media access control">MAC</a></li>
<li>PSAP - <a href="Physical_layer" title="Physical layer">PHY</a></li></ul>
<p><a href="IEEE_802.3" title="IEEE 802.3">802.3</a> (the Ethernet standard) optionally includes:
</p>
<ul><li>OSAP - operations, administration and maintenance (OAM)</li>
<li>MCSAP - MAC control</li>
<li>Energy efficient Ethernet PSAP</li>
<li>Time sync PSAP</li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><cite class="citation techreport cs1"><i>IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture</i> (Technical report). <a href="IEEE" class="mw-redirect" title="IEEE">IEEE</a>. 2014. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FIEEESTD.2014.6847097">10.1109/IEEESTD.2014.6847097</a>. <a href="IEEE_802" title="IEEE 802">802</a>.</cite></span>
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