OSI Model

Protocol 

A set of rules that govern how something works.

Within a computer science:

• A communication protocol is a system of digital rules for data exchange within or between computers
• When data is exchanged through a computer network, the rules system is called a network protocol 

Logical Protocol (SMTP) - It is how emails are sent

• HTTPS - Browsing through the net 
• 
  
• TSP

Physical

• Bluetooth
• Wifi

Lowest layer is logical and the highest is physical.

Physical layer = Describes electrical and physical specifications for devices: Cable, connectors, hubs.

Data link layer = Provides connections between hosts on the same network: Ethernet 

Network layer =  Provides connection between hosts on different networks :IPv4 and IPv6. Routing of packets.

Transport = Provides transport of data: TCP and UDP. End to end connections.

Session =  establishing a connection. Controls the dialogs between computers (handshake). Also controls duplexing termination and restarts. 

Presentation = compressing the data.  Provides a context for communication between layers 

ASCII Characters, Encryption and decryption. Compression.

Application = HTTPS, where we find network application eg mail, browser 

• All
• People
• Studying
• This 
• Needs
• Drastic
• Psychotherapy

It hands communication between computers across networks.