Some notes about computer networking, won’t go too deep.
References
DNS
IPv4
Address classes
| Class | Start | End | Mask | CIDR |
|---|---|---|---|---|
| Class A | 0.0.0.0 | 127.255.255.255 | 255.0.0.0 | /8 |
| Class B | 128.0.0.0 | 191.255.255.255 | 255.255.0.0 | /16 |
| Class C | 192.0.0.0 | 223.255.255.255 | 255.255.255.0 | /24 |
| Class D | 224.0.0.0 | 239.255.255.255 | - | /4 |
| Class E | 240.0.0.0 | 255.255.255.255 | - | - |
Private addresses
| Desc | Start | End | CIDR |
|---|---|---|---|
| class A (1) | 10.0.0.0 | 10.255.255.255 | 10.0.0.0/8 |
| class B (16) | 172.16.0.0 | 172.31.255.255 | 172.16.0.0/12 |
| class C (256) | 192.168.0.0 | 192.168.255.255 | 192.168.0.0/16 |
CIDR Notation
198.51.100.0/24
Subnet. The first 24 bits (198.51.100) define the network portion, and the remaining 8 bits are for individual devices (hosts) within that network. This subnet can contain a total of 256 (2^8) IP addresses, but two are reserved (network address - 198.51.100.0 and broadcast address - 198.51.100.255).
- 198.51.100.14/24
198.51.100.14 is a specific IP address within the subnet defined by 198.51.100.0/24. The “/24” still refers to the subnet mask, but in this case, it clarifies that this particular IP (198.51.100.14) belongs to the network 198.51.100.0/24.
OSI Model
7. Application Layer
Data generated by and usable by software applications (eg: API calls).
6. Presentation Layer
Responsible for translation, encryption, and compression of data.
Protocols: HTTPS??
5. Session Layer
This is the layer responsible for opening and closing communication between the two devices.
Usually handled by TCP.
4. Transport Layer
This includes taking data from the session layer and breaking it up into chunks called segments before sending it to layer 3.
3. Network Layer
Handles the routing and sending of data between different networks.
Router (Gateway)
Device that forwards packets to a destination other than the local network
2. Data Link Layer
Facilitates data transfer between two devices on the same network.
Ethernet Switches
Forwarding based on MAC addresses, maintains a mapping of MAC -> PORT (physical).
Address Resolution Protocol (ARP)
https://en.wikipedia.org/wiki/Address_Resolution_Protocol#Example
1. Physical Layer
Includes the physical equipment involved in the data transfe (cables and switches). Data gets converted into a bit stream (1s and 0s).