layers of TCP/IP
TCP/IP协议分层<p>提到协议分层，我们很容易联想到ISO-OSI的七层协议经典架构，但是TCP/IP协议族的结构则稍有不同。如图所示 </p><p><img 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" alt=""></p><span class="mw-headline" id="Layer_names_and_number_of_layers_in_the_literature">Layer names and number of layers in the literature</span>
<p>The following table shows the layer names and the number of layers of networking models presented in <a href="http://en.wikipedia.org/wiki/Request_for_comments" title="Request for comments" class="mw-redirect" target="_blank">RFCs</a> and textbooks in widespread use in today's university computer networking courses.</p>
<table class="wikitable">
<tbody><tr>
<th style="background:#adb"><a href="http://tools.ietf.org/html/rfc1122" class="external mw-magiclink-rfc" target="_blank">RFC 1122</a> <sup id="cite_ref-6" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-6" target="_blank"><span>[</span>7<span>]</span></a></sup></th>
<th style="background:#adb">Tanenbaum</th>
<th style="background:#adb">Cisco Academy<sup id="cite_ref-7" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-7" target="_blank"><span>[</span>8<span>]</span></a></sup></th>
<th style="background:#adb">Kurose<sup id="cite_ref-8" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-8" target="_blank"><span>[</span>9<span>]</span></a></sup> Forouzan <sup id="cite_ref-Forouzan_9-0" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-Forouzan-9" target="_blank"><span>[</span>10<span>]</span></a></sup></th>
<th style="background:#adb">Comer<sup id="cite_ref-Comer_10-0" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-Comer-10" target="_blank"><span>[</span>11<span>]</span></a></sup> Kozierok<sup id="cite_ref-11" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-11" target="_blank"><span>[</span>12<span>]</span></a></sup></th>
<th style="background:#adb">Stallings<sup id="cite_ref-Stallings_12-0" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-Stallings-12" target="_blank"><span>[</span>13<span>]</span></a></sup></th>
<th style="background:#adb">Arpanet Reference Model 1982 (<a href="http://tools.ietf.org/html/rfc871" class="external mw-magiclink-rfc" target="_blank">RFC 871</a>)</th>
</tr>
<tr>
<td style="background:#cfc"><i>Four layers</i> <sup id="cite_ref-RFC1122Layers_13-0" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-RFC1122Layers-13" target="_blank"><span>[</span>14<span>]</span></a></sup></td>
<td style="background:#cfc"><i>Four layers</i> <sup id="cite_ref-14" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-14" target="_blank"><span>[</span>15<span>]</span></a></sup></td>
<td style="background:#cfc"><i>Four layers</i></td>
<td style="background:#cfc"><i>Five layers</i></td>
<td style="background:#cfc"><i>Four+one layers</i></td>
<td style="background:#cfc"><i>Five layers</i></td>
<td style="background:#cfc"><i>Three layers</i></td>
</tr>
<tr>
<td style="background:#cfc">"Internet model"<sup class="Template-Fact" title="This claim needs references to reliable sources from September 2009" style="white-space:nowrap;">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" target="_blank">citation needed</a></i>]</sup></td>
<td style="background:#cfc">"TCP/IP reference model"<sup id="cite_ref-15" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-15" target="_blank"><span>[</span>16<span>]</span></a></sup></td>
<td style="background:#cfc">"Internet model"</td>
<td style="background:#cfc">"Five-layer Internet model" or "TCP/IP protocol suite"</td>
<td style="background:#cfc">"TCP/IP 5-layer reference model"</td>
<td style="background:#cfc">"TCP/IP model"</td>
<td style="background:#cfc">"Arpanet reference model"</td>
</tr>
<tr>
<td>Application <sup id="cite_ref-RFC1122Layers_13-1" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-RFC1122Layers-13" target="_blank"><span>[</span>14<span>]</span></a></sup><sup id="cite_ref-16" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-16" target="_blank"><span>[</span>17<span>]</span></a></sup></td>
<td>Application</td>
<td>Application</td>
<td>Application</td>
<td>Application</td>
<td>Application</td>
<td>Application/Process</td>
</tr>
<tr>
<td>Transport <sup id="cite_ref-RFC1122Layers_13-2" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-RFC1122Layers-13" target="_blank"><span>[</span>14<span>]</span></a></sup></td>
<td>Transport</td>
<td>Transport</td>
<td>Transport</td>
<td>Transport</td>
<td>Host-to-host or transport</td>
<td rowspan="2">Host-to-host</td>
</tr>
<tr>
<td>Internet <sup id="cite_ref-RFC1122Layers_13-3" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-RFC1122Layers-13" target="_blank"><span>[</span>14<span>]</span></a></sup></td>
<td>Internet</td>
<td>Internetwork</td>
<td>Network</td>
<td>Internet</td>
<td>Internet</td>
</tr>
<tr>
<td>Link <sup id="cite_ref-RFC1122Layers_13-4" class="reference"><a href="http://en.wikipedia.org/wiki/TCP/IP#cite_note-RFC1122Layers-13" target="_blank"><span>[</span>14<span>]</span></a></sup></td>
<td>Host-to-network</td>
<td>Network interface</td>
<td>Data link</td>
<td>Data link (Network interface)</td>
<td>Network access</td>
<td>Network interface</td>
</tr>
<tr>
<td><br></td>
<td><br></td>
<td><br></td>
<td>Physical</td>
<td>(Hardware)</td>
<td>Physical</td>
<td><br></td></tr></tbody></table><table class="wikitable"><tbody><tr><th colspan="5">OSI Model</th>
</tr>
<tr>
<th><br></th>
<th>Data unit</th>
<th>Layer</th>
<th style="width:9em;">Function</th>
</tr>
<tr>
<th rowspan="4">Host<br>
layers</th>
<td style="background:#d8ec9b;" rowspan="3">Data</td>
<td style="background:#d8ec9b;">7. <a href="http://en.wikipedia.org/wiki/Application_Layer" title="Application Layer" target="_blank">Application</a></td>
<td style="background:#d8ec9c;">Network process to application</td>
</tr>
<tr>
<td style="background:#d8ec9b;">6. <a href="http://en.wikipedia.org/wiki/Presentation_Layer" title="Presentation Layer" target="_blank">Presentation</a></td>
<td style="background:#d8ec9b;">Data representation, encryption and decryption, convert machine dependent data to machine independent data</td>
</tr>
<tr>
<td style="background:#d8ec9b;">5. <a href="http://en.wikipedia.org/wiki/Session_Layer" title="Session Layer" target="_blank">Session</a></td>
<td style="background:#d8ec9b;">Interhost communication</td>
</tr>
<tr>
<td style="background:#e7ed9c;">Segments</td>
<td style="background:#e7ed9c;">4. <a href="http://en.wikipedia.org/wiki/Transport_Layer" title="Transport Layer" target="_blank">Transport</a></td>
<td style="background:#e7ed9c;">End-to-end connections, reliability and <a href="http://en.wikipedia.org/wiki/Flow_control" title="Flow control" target="_blank">flow control</a></td>
</tr>
<tr>
<th rowspan="3">Media<br>
layers</th>
<td style="background:#eddc9c;">Packet/Datagram</td>
<td style="background:#eddc9c;">3. <a href="http://en.wikipedia.org/wiki/Network_Layer" title="Network Layer" target="_blank">Network</a></td>
<td style="background:#eddc9c;">Path determination and <a href="http://en.wikipedia.org/wiki/Logical_address" title="Logical address" target="_blank">logical addressing</a></td>
</tr>
<tr>
<td style="background:#e9c189;">Frame</td>
<td style="background:#e9c189;">2. <a href="http://en.wikipedia.org/wiki/Data_Link_Layer" title="Data Link Layer" target="_blank">Data Link</a></td>
<td style="background:#e9c189;">Physical addressing</td>
</tr>
<tr>
<td style="background:#e9988a;">Bit</td>
<td style="background:#e9988a;">1. <a href="http://en.wikipedia.org/wiki/Physical_Layer" title="Physical Layer" target="_blank">Physical</a></td>
<td style="background:#e9988a;">Media, signal and binary transmission</td></tr></tbody></table><p><br></p><br><br>
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