Fundamentals

🔹 Layer 7 – Application:  
Interfaces directly with user applications, enabling them to send/receive data over a network.

🔹 Layer 6 – Presentation:  
Translates data between application and network formats; handles encryption, compression, and formatting.

🔹 Layer 5 – Session:  
Establishes, manages, and terminates communication sessions between devices, ensuring data streams stay distinct.

🔹 Layer 4 – Transport:  
Manages end-to-end delivery of data using protocols like TCP (reliable) or UDP (fast). Splits data into segments/datagrams.

🔹 Layer 3 – Network:  
Handles logical addressing (IP addresses) and routes data across networks to its destination.

🔹 Layer 2 – Data Link:  
Adds physical (MAC) addressing, formats data for transmission, and performs error checking on received data.

🔹 Layer 1 – Physical:  
Deals with actual hardware transmission—sending and receiving raw binary data as electrical or optical signals.