---
# System prepended metadata

title: Computer Networks Overview
tags: [computer network]

---

# Computer Networks Overview
###### tags: `computer network`
## What is Computer Network
A network is a collection of end-host (i.e. computer) connected with each other to transfer and receive information
## Network Architecture
A computer nework atchitecture is composed of different components, including host, hub, router, subnet, regional network, global network
![](https://i.imgur.com/gMZ3j3W.png)

With the architecture in mind, how could we transfer the data? The following section would answer the question.
## Two Types of Tranferring Data
### Circuit Switched
#### how it works
Circuit switching would create a dedicated path for transferring the data. The detailed process is as the following:
1. Establish an end-to-end circuit
2. send information
3. close out the connection

This type of tranferring data could guarantee the performance (since it takes up the whole path just for one connection), and it also have low complexity in managing exchanging data.

However, it is not efficient engough for large data exchange since an end-to-end connection would take up the all path. The efficiency is not good.

#### Implementation
* TDM
* FDM

### Packet Switched
#### how it works
Divide the information into chunk of data, and pass those chunk of data to destination with the help of router or switch. 
* see [here](https://www.cdw.com/content/cdw/en/articles/networking/ethernet-switch-vs-hub-vs-router.html#:~:text=While%20a%20network%20switch%20can,allows%20for%20connections%20between%20networks.) for difference between router and switch
* an easy difference is switch use for building network and router use for connect network
#### delay
![](https://i.imgur.com/YXrXo0Z.png)
* Process delay: the time to process a packet
* Queueing delay: the time to wait in queue
* Transmission delay: the time to transfer packet from queue to link
* Propagation: the time for passing the packet from one end point to the other
### Compare and Constract of Two method


|                    | Circuit          | Packeting            |
|:------------------ | ---------------- |:-------------------- |
| Delay              | Text             | Text                 |
| Order              | In-Order Passing | Out of Order Passing |
| Use of Bandwidth   | Not efficient    | Efficient            |
| Routing Complexity | Low              | High                 |
| Quality            | All of nothing   | Migh loss small chunk of overall data                     |

## TCP / IP Model



| Application |  Skype, SMPTP, HTTP
| ----------- |  ----
| Transport   |  TCP, UDP
| Network     |  IP
| Link        |  ARP


