3.4 Network hardware

## Network interface card (NIC)
this is a component in a device that enables it to connect to a network
## Router
a device that forwards packets to their correct destinations in a network
- The router examining the packet looks for the packet header,  looking for the IP address of destination
- The packet being sent toward its correct destination by the fastest route // decides which route it takes
- Router is shown connecting devices/networks
- Router is shown assigning an IP address to a device

![image.png](https://doc.lie.ee:33101/media/202509/ae1336990f914e0d875f6e41e152a87d2332.png)

## Firewall // proxy-server
this can be hardware or software based and filters traffic coming into and out of a network
#### Media Access Control (MAC) address
this address is assigned by the manufacturer and is used to uniquely identify the device
- Media access control
- Unique address given to each device
- It is assigned by the manufacturer
- It can be used to identify a device
- Does not (usually) change // static

##### Structure:

- Uses hexadecimal values
- Normally 48/64 bits in length (accept any other reasonable value)
- First half is manufacturer number/code/ID
- Second half is serial number

#### IP address
this address is assigned by the network and used to identify a device on a network
- Gives each device on a network an identifier // IP address used to locate a device on a network
- Each address is unique within the network 
- Allows a device/gateway/node to send data to the correct destination / a specific device/gateway/node

| Static IP address                                                                                             | Dynamic IP address                                                                       |
| ------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| A fixed, unchanging network identifier assigned to a device,                                                  | It can change each time the device is connected to the network                           |
| Static IP addresses are useful when websites need to remember a device for a long time. Eg) VPNs whitelisting | Dynamic IP address is relatively more secure, hence used where data privacy is important |
| Faster upload/download speeds                                                                                 | Maintaining cost of dynamic IP address is lesser                                         |

##### IPv4:

- Four groups of denary or Hexadecimal integers separated by dots
- Numbers between 0 and 255 / 0 and FF
- Each stored in 1 byte / 8 bits // the whole is stored in 32 bits / 4 bytes
- Eg: 123.234.5.35

##### IPv6:

- 128-bits/16bytes address format
- Eight groups of hexadecimal digits separated by colons
- Each stored in 2 bytes/16bits
- Eg: 3ffe:1900:4545:3a7b:200a:f8ff:fe2i:67cf

#### IPv6 Compression:

Step1: Remove Leading Zeros
```
67A1:0045:0010:0052:0001:0012:8000 => 67A1:45:10:52:1:12:8000
```
Step 2:Remove Inline Zeros
```
67A1:0000:0000:0000:0001:0012:8000 => 67A1::1:12:8000
```
**This can be used anywhere in an address, start, middle or end
However this::can only be used once in one address
```
eg: 8055:F2F2:0000:0000:FFF1:0000:0000:DD04
=> 8055:F2F2::FFF1:0000:0000:DD04
OR => 8055:F2F2:0000:0000:FFF1::DD04
```

|             | iipv4                                                                                                                                                                                                                         | ipv6                                                     |
| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------- |
| Similarity  | They can both be used to identify a device (on a network)<br>They can both be static / dynamic<br>They are both unique (to a device on a network)<br>They can both be assigned by a router<br>They can both be public/private |                                                          |
| Differences | usually written as denary                                                                                                                                                                                                     | usually written as hexadecimal                           |
|             | is separated using dots                                                                                                                                                                                                       | is separated using colons                                |
|             | is 32-bit                                                                                                                                                                                                                     | is 128-bit                                               |
|             | is 4 groups of digits                                                                                                                                                                                                         | is 8 groups of digits                                    |
|             | digits are between 0 and 255                                                                                                                                                                                                  | digits are between 0000 and FFFF                         |
|             | all 0s are displayed                                                                                                                                                                                                          | can use double colons to replace repeated groups of 0000 |
|             | has fewer available unique addresses                                                                                                                                                                                          | has more available unique addresses                      |
## Domain name server // DNS
the system that stores a database of uniform resource locators (URLs) and their corresponding IP addresses
## Web browser
the software that sends a request to the IP address to obtain the web page data