Computer Networking: Difference between revisions
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Computer networking theory | |||
==OSI Model== | ==Reference Models== | ||
===OSI Model=== | |||
{{main | Wikipedia: OSI model}} | {{main | Wikipedia: OSI model}} | ||
The OSI model presents the network stack using multiple layers. | The OSI model presents the network stack using multiple layers. | ||
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The layers are: | The layers are: | ||
<ol | <ol reversed> | ||
<li | <li>Application layer</li> | ||
<li | <li>Presentation layer</li> | ||
<li | <li>Session layer</li> | ||
<li | <li>Transport layer</li> | ||
<li | <li>Physical layer</li> | ||
<li | <li>Network layer</li> | ||
<li | <li>Data link layer</li> | ||
<li | <li>Physical layer</li> | ||
</ol> | </ol> | ||
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Finally, the application layer is what highest-level, whatever service is being provided to the user. | Finally, the application layer is what highest-level, whatever service is being provided to the user. | ||
==TCP/IP== | ===TCP/IP=== | ||
{{main | Wikipedia: Internet protocol suite}} | {{main | Wikipedia: Internet protocol suite}} | ||
TCP/IP has | TCP/IP has four layers: | ||
<ol | <ol reversed> | ||
<li | <li>Application layer</li> | ||
<li | <li>Transport layer</li> | ||
<li | <li>Internet layer</li> | ||
<li | <li>Link layer</li> | ||
</ol> | </ol> | ||
==Routing== | ==Link Layer== | ||
===Distance Vector=== | ===Hardware=== | ||
* Hub - A hub connects multiple devices and will pass around data frames to every single connection. It has no logic and is equivalent to wiring all the cables together. | |||
* Repeater - A repeater is used to boost signals. It will read the pattern (e.g. voltage representing bits) and repeat it on another wire. | |||
* Bridge or Switch - A switch connects multiple devices and does routing at this layer using mac addresses. | |||
* Router - Routers work at the network layer to route packets across different networks (e.g. across VLANS or LAN to WAN). | |||
==Network Layer== | |||
===Routing=== | |||
====Distance Vector==== | |||
In Distance Vector routing, or Bell-ford Algorithm, each node incrementally builds up it's own routing table to identify the next hop to reach each destination. | In Distance Vector routing, or Bell-ford Algorithm, each node incrementally builds up it's own routing table to identify the next hop to reach each destination. | ||
== | ===Internet=== | ||
====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 | |||