Functions of Each layer

Provides network services directly to the user.

📌 This is the layer where users interact with the network.

• 🌐 Web access

• 📧 Email services

• 📂 File transfer

• 🧑‍💻 Remote login

• HTTP / HTTPS

• FTP

• SMTP

• DNS

Opening a website using a browser like Chrome.

📌 Application layer provides network services to end users.

Ensures that data sent by the sender is understood by the receiver.

📌 Acts as a translator 🗣️.

• 🔄 Data translation (format conversion)

• 🔐 Encryption

• 🔓 Decryption

• 📦 Data compression

• HTTPS encrypting data

• ZIP file compression

📌 Presentation layer handles data formatting, encryption, and compression.

Manages sessions (connections) between two devices.

📌 Controls start, maintain, and end of communication.

• Session establishment

• Session maintenance

• Session termination

• Synchronization (checkpoints)

Zoom meeting session:

• Join meeting

• Stay connected

• Leave meeting

📌 Session layer establishes, manages, and terminates sessions.

Ensures end-to-end delivery of data reliably and efficiently.

📌 One of the most important layers.

• ✂️ Segmentation & reassembly

• ❌ Error control

• 🚦 Flow control

• 🔢 Port addressing

• TCP (Reliable)

• UDP (Fast)

Courier service delivering parcels safely to the correct address.

📌 Transport layer ensures reliable end-to-end data delivery.

Handles routing and logical addressing.

📌 Decides best path for data to travel.

• IP addressing

• Packet routing

• Path selection

• Packet forwarding

• IP

• ICMP

• Routing protocols (RIP, OSPF)

Google Maps choosing the best route.

📌 Network layer determines the best path for data delivery.

Provides node-to-node delivery within the same network.

📌 Ensures data reaches the correct physical device.

• Framing

• MAC addressing

• Error detection

• Flow control

• Access control (MAC)

• Switch

• Bridge

Delivering a parcel to the correct house on a street.

📌 Data Link layer ensures error-free transmission between adjacent nodes.

Handles actual physical transmission of bits (0s and 1s).

📌 Lowest layer of OSI model.

• Bit transmission

• Voltage levels

• Cable specifications

• Data rates

• Physical topology

• Cables

• Hub

• Repeater

• NIC (physical aspect)

Roads that allow vehicles to move.

📌 Physical layer transmits raw bits over a physical medium.