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Computer Networking: Difference between revisions

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The layers are:
The layers are:
<ol style="transform: rotate(180deg);">
<ol reversed>
<li style="transform: rotate(-180deg);">Physical layer</li>
<li>Application layer</li>
<li style="transform: rotate(-180deg);">Data link layer</li>
<li>Presentation layer</li>
<li style="transform: rotate(-180deg);">Network layer</li>
<li>Session layer</li>
<li style="transform: rotate(-180deg);">Physical layer</li>
<li>Transport layer</li>
<li style="transform: rotate(-180deg);">Transport layer</li>
<li>Physical layer</li>
<li style="transform: rotate(-180deg);">Session layer</li>
<li>Network layer</li>
<li style="transform: rotate(-180deg);">Presentation layer</li>
<li>Data link layer</li>
<li style="transform: rotate(-180deg);">Application layer</li>
<li>Physical layer</li>
</ol>
</ol>


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{{main | Wikipedia: Internet protocol suite}}
{{main | Wikipedia: Internet protocol suite}}
TCP/IP has four layers:
TCP/IP has four layers:
<ol style="transform: rotate(180deg);">
<ol reversed>
<li style="transform: rotate(-180deg);">Link layer</li>
<li>Application layer</li>
<li style="transform: rotate(-180deg);">Internet layer</li>
<li>Transport layer</li>
<li style="transform: rotate(-180deg);">Transport layer</li>
<li>Internet layer</li>
<li style="transform: rotate(-180deg);">Application layer</li>
<li>Link layer</li>
</ol>
</ol>


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====BGP====
====BGP====
==Physical Layer==
There are several protocols at the physical layer such as ethernet, LTE, and DOCSIS.
===Multiplexing===
Multiplexing is used to send or receive multiple signals along the same wire. Note that, sending and receiving count as two separate signals.
Duplex means that the upstream and downstream are the the same speed. Full duplex (FDX) means the up and down can operate at the same time.
* Time-division Multiplexing/Duplex (TDD) - if you don't have enough frequencies, you spend some time sending and some time receiving the signal. This is inherently not full duplex.
* Frequency-division Multiplexing/Duplex (FDD) - with multiple frequencies, you can send and receive at the same time on separate frequencies. If the frequencies are evenly divided, you will have full duplex.
* Echo Cancellation - by sending and receiving on the same frequencies at the same time, you can get full duplex. This is more complicated than the other options.
===Terminology===
* US/DS - Upstream and downstream
* OOB - out of band, additional signals on a separate frequency or wire
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