OSI Model

Transport Layer

Responsible for breaking large messages into smaller segments and ensuring they are reassembled correctly at the destination.

Router

Operates at the Network layer.

Presentation Layer

Responsible for managing encryption and decryption.

Session Layer

Manages active connections between two computers for a long period.

Switch

Forwards data based on MAC addresses and operates at the Data Link layer.

Network Layer

Responsible for logical addressing and packet forwarding across different networks.

HTTPS

Uses the Presentation layer to handle encryption when visiting a secure website.

Reliable Data Transfer

Ensured by the Transport layer, which includes error detection and flow control.

Email Protocols

Operate at the Application layer, including SMTP, IMAP, and POP3.

Physical Layer

Affected when a network cable is damaged and causing signal loss.

OSI Model

A conceptual framework with 7 layers that standardizes network communication.

Physical Layer (Layer 1)

The layer that transmits raw data bits over cables, fiber optics, or wireless signals. It handles hardware, voltages, and transmission speeds.

Examples of Physical Layer

Ethernet cables, fiber optics, Wi-Fi signals, network adapters, hubs, repeaters.

Troubleshooting Physical Layer

Check for damaged cables, weak Wi-Fi signals, or broken hardware.

Data Link Layer (Layer 2)

Manages MAC addresses, error detection, and switching. Ensures data is sent to the correct device in a local network.

Examples of Data Link Layer

Switches, MAC addresses, Wi-Fi connections, VLANs.

Troubleshooting Data Link Layer

Check MAC addresses, VLAN configurations, and switch connections.

Network Layer (Layer 3)

Responsible for routing data between networks using IP addresses. Determines the best path for data transmission.

Examples of Network Layer

Routers, IP addressing, ICMP (ping), OSPF, BGP.

Troubleshooting Network Layer

Check IP addresses, subnet masks, gateways, and routing tables.

Transport Layer (Layer 4)

Ensures data is delivered reliably and in the correct order. Uses TCP for reliability and UDP for speed.

Examples of Transport Layer

TCP (reliable data delivery), UDP (fast but no error correction), port numbers.

Troubleshooting Transport Layer

Check for blocked ports, firewall settings, or network congestion.

Session Layer (Layer 5)

Manages and maintains active connections between devices. Handles authentication and reconnections.

Examples of Session Layer

Logging into a website, remote desktop connections, NetBIOS.

Troubleshooting Session Layer

If you keep getting logged out, there may be an issue with session management.

Presentation Layer (Layer 6)

Handles data formatting, encryption, and compression. Ensures data is readable by the receiving device.

Examples of Presentation Layer

SSL/TLS encryption, JPEG image processing, MP3 audio compression.

Troubleshooting Presentation Layer

Check if encryption settings (SSL/TLS) are correct or if files are corrupted.

Application Layer (Layer 7)

The layer where users interact with network applications like web browsers, email, and file transfers.

Examples of Application Layer

HTTP/HTTPS (web browsing), FTP (file transfer), SMTP/IMAP/POP3 (email), DNS.

Troubleshooting Application Layer

If a website or app isn't loading, check network settings, DNS, or server issues.