The Layers:

Application Layer: Provides net working services to applications.

Transport Layer:

• Sets up communications between 2 devices.
• Splits data into packets.
• Checks packets are correctly sent and delivered.

Network Layer:

• Adds IP addresses to data packets.
• Directs data packets between devices.
• Handles traffic between data packets.

Link Layer:

• Passes the data over the network.
• Responsible for how data is sent as electrical signals over cables, wireless etc.

Application Layer

HTTP:

• Hyper Text Transfer Protocol.
• Used by web browsers to access websites and communicate with web servers.

HTTPS:

• Hyper Text Transfer Protocol Secure.
• A more secure version of HTTP.
• Encrypts all of the information sent and recieved.

FTP:

• File Transfer Protocol.
• Accesses, edits and moves files between devices on a network.

IMAP:

• Internet Message Access Protocol.
• Retrieves emails from a server.

SMTP:

• Simple Mail Transfer Protocol.
• Sends emails between servers.

Transport Layer

There are two main protocols in the transport layer:

1. TCP
2. UDP

TCP:

• Transmission Control Protocol.
• Establishes a connection between the sending and recieveing devices.
• Splits the data into NUMBERED packets that can be reassembled once at its location.
• The sending device gets a CONFIRMATION when the transfer is complete.

UDP:

• User Datagram Protocol.
• Splits the data into UNNUMBERED packets.
• It only sends the packets once without checking if they were sent correctly or at all.

When each of them would be used:

• UDP: Applications that need fast and efficient transmission like videostreaming.
• TCP: Applications that need reliable transmission is needed like when downloading text files.

Network Layer

IP (Internet Protocol) is the most common protocol in the network layer.

IP's are responsible for allocating unique addresses to every device on the internet.

IP gets data from one device to another one.

There are 2 types of IP's:

• IPv4
• IPv6

IPv4 VS IPv6:

• IPv4 uses a 32-bit address which allows approximatley 4 billion devices.
• IPv6 uses a 128-bit address allows exactly: 340,282,366,920,938,463, 463,374,607,431, 768,211,456 devices at once.

Link Layer

The most common link layer protocols are:

• WiFi
• Ethernet

Difference:

• WiFi is a family of protocols that get network packets from one device to another via radio waves.
• Ethernet is a family of protocols that get network packets from one device to another via a cable.