<h1 id="osi-model"><a aria-hidden="true" class="anchor-heading icon-link" href="#osi-model"></a>OSI model</h1>
<p>The <abbr title="Open Systems Interconnection">OSI</abbr> model is a means of grouping protocols by the layer at which they operate.</p>
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<table><thead><tr><th>Layer</th><th>Name</th><th>Description</th><th>Examples</th><th></th><th></th><th></th></tr></thead><tbody><tr><td>7</td><td>Application</td><td>Primary interface for working with a communication system</td><td><abbr title="File Transfer Protocol">FTP</abbr>, [[<abbr title="HyperText Transfer Protocol">HTTP</abbr></td><td>net.http]], <abbr title="Secure Shell">SSH</abbr></td><td></td><td></td></tr><tr><td>6</td><td>Presentation</td><td>Formatting and presentation of data; e.g. encoding, data compression, encryption/decryption</td><td><abbr title="American Standard Code for Information Interchange">ASCII</abbr>, <abbr title="Portable Network Graphic">PNG</abbr></td><td></td><td></td><td></td></tr><tr><td>5</td><td>Session</td><td>Managing communication sessions (continuous transmissions between two nodes)</td><td><abbr title="Synchronise">SYN</abbr>, <abbr title="Acknowledge">ACK</abbr>, source and destination ports</td><td></td><td></td><td></td></tr><tr><td>4</td><td>Transport</td><td>Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing</td><td>[[<abbr title="Transmission Control Protocol">TCP</abbr></td><td>net.tcp]], [[<abbr title="User Datagram Protocol">UDP</abbr></td><td>net.udp]], [[port numbers</td><td>net#common-port-numbers]]</td></tr><tr><td>3</td><td>Network</td><td>Structuring and managing a multi-node network, including addressing, routing and traffic control</td><td><abbr title="Internet Protocol">IP</abbr> ([[v4</td><td>net.ipv4]] and [[v6</td><td>net.ipv6]]), routers</td><td></td></tr><tr><td>2</td><td>Data link</td><td>Reliable transmission of data frames between two nodes connected by a physical layer</td><td>[[Ethernet</td><td>net.ethernet]], <abbr title="Media Access Control">MAC</abbr>, switches</td><td></td><td></td></tr><tr><td>1</td><td>Physical</td><td>Transmission and reception of raw bit streams over a physical medium</td><td>[[Ethernet</td><td>net.ethernet]], Twisted pair, optical fiber, <abbr title="Registered Jack 45">RJ45</abbr></td><td></td><td></td></tr></tbody></table></div>
<hr>
<strong>Backlinks</strong>
<ul>
<li><a href="/notes/f4578b78-ef2d-4f26-8f17-4ea8de6d227a">Networking (public)</a></li>
<li><a href="/notes/9827ec43-7f9e-43d0-a87e-ebad41289de9">Ethernet (public)</a></li>
<li><a href="/notes/b62426f2-a0fc-41b3-9962-9f128016c91e">IPv6 (public)</a></li>
<li><a href="/notes/70115b63-9d8f-408d-a9f9-a598dabf89fc">SRE at Google (public)</a></li>
<li><a href="/notes/ae6f1257-3526-4a3b-b120-9046050e4faf">Shield (public)</a></li>
<li><a href="/notes/09dd764d-8bcb-48c8-83fa-3fae21b3ad36">WAF (public)</a></li>
<li><a href="/notes/f4e23836-db17-4c8c-8302-1d66cec79189">Application Gateway (public)</a></li>
<li><a href="/notes/08ee6339-6b80-4f74-8c71-5e99c4d12832">Load Balancer (public)</a></li>
<li><a href="/notes/e6e75d75-2351-467f-b8c6-bc1bf23db32c">ALB (public)</a></li>
<li><a href="/notes/b2618f9e-e0e1-4bef-9ba2-444e17bbbd63">NLB (public)</a></li>
<li><a href="/notes/4cf53e08-fce4-432e-9d22-2cd44204713c">Ingress (public)</a></li>
<li><a href="/notes/08adad76-6eb0-45e6-9a26-e4fa9f411ad9">Networking (public)</a></li>
<li><a href="/notes/c36504e3-c5c7-4304-9949-c25e0cf7b5b8">Services (public)</a></li>
</ul>

OSI model


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Layer	Name	Description	Examples
7	Application	Primary interface for working with a communication system	FTP, [[HTTP	net.http]], SSH
6	Presentation	Formatting and presentation of data; e.g. encoding, data compression, encryption/decryption	ASCII, PNG
5	Session	Managing communication sessions (continuous transmissions between two nodes)	SYN, ACK, source and destination ports
4	Transport	Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing	[[TCP	net.tcp]], [[UDP	net.udp]], [[port numbers	net#common-port-numbers]]
3	Network	Structuring and managing a multi-node network, including addressing, routing and traffic control	IP ([[v4	net.ipv4]] and [[v6	net.ipv6]]), routers
2	Data link	Reliable transmission of data frames between two nodes connected by a physical layer	[[Ethernet	net.ethernet]], MAC, switches
1	Physical	Transmission and reception of raw bit streams over a physical medium	[[Ethernet	net.ethernet]], Twisted pair, optical fiber, RJ45