Some notes about computer networking, won’t go too deep.

References

IPv4

ClassStartEndMaskCIDR
Class A0.0.0.0127.255.255.255255.0.0.0/8
Class B128.0.0.0191.255.255.255255.255.0.0/16
Class C192.0.0.0223.255.255.255255.255.255.0/24
Class D224.0.0.0239.255.255.255-/4
Class E240.0.0.0255.255.255.255--

Private addresses

DescStartEndBlock
Single class A10.0.0.010.255.255.25510.0.0.0/8
16 cont. class B172.16.0.0172.31.255.255172.16.0.0/12
256 cont. class C192.168.0.0192.168.255.255192.168.0.0/16
  • Host route: Specific host, 255.255.255.255 (/32)
  • Subnet: Variable Length Subnet Masks (VLSM) are permitted.
  • Summary: …
  • Major network: …
  • Supernet: …
  • Default route: route of last resort. 0.0.0.0

OSI Model

OSI

7. Application Layer

Data generated by and usable by software applications (eg: API calls).

Protocols: HTTP and SMTP.

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.

Protocols: TCP, UDP.

3. Network Layer

Handles the routing and sending of data between different networks.

Protocols: IP and ICMP.

Router (Gateway)

Device that forwards packets to a destination other than the local network

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).