Simplifying the OSI Model for Beginners

List of all layers in OSI layers

Tip to remember all layers - All People Should Try New Domino's Pizza

• Application layer

  The Application Layer is the topmost layer where users interact directly with network applications. Examples include web browsers like Chrome or email clients. This layer handles various service

  • File Transfer: Managed by protocols like FTP (File Transfer Protocol)

  • Web Surfing: Handled by HTTP/HTTPS.

  • Email: Managed by SMTP (Simple Mail Transfer Protocol).

  • Virtual Terminal: Facilitated by Telnet.

• Presentation layer

  Responsible for translating, compressing, and encrypting data, ensuring it’s properly formatted for the Application Layer or the network

  • Translation: Converts data from the Application Layer into a machine-readable format.

  • Data Compression: Reduces the size of data to enable faster transmission. This can be either lossy or lossless.

  • Encryption/Decryption: Ensures secure data transmission using protocols like SSL (Secure Socket Layer).

• Session layer

  The Session Layer manages the connection between two devices, handling the setup, maintenance, and termination of communication sessions.

  • Session Management: Establishes and manages the connection between client and server.

  • Authentication and Authorization: Verifies and authorizes the user or device before establishing a session.

  • Data Management: Handles the flow of data packets (images, text, etc.) to ensure they are delivered to the Application Layer.

• Transport layer

  The Transport Layer ensures the reliable transmission of data across a network by handling segmentation, flow control, and error control.

  • Segmentation: Divides data from the Session Layer into segments, each tagged with a port number and sequence number.

  • Flow Control: Manages the data transmission rate, accommodating differences in transfer speeds between the client and server.

  • Error Control: Uses checksums to detect and recover corrupted data.

    • TCP (Transmission Control Protocol): Connection-oriented and ensures reliable data transmission.

    • UDP (User Datagram Protocol): Connectionless and faster, though it may result in some data loss, which is acceptable for certain applications.

• Network layer

  The Network Layer is responsible for logical addressing, path determination, and routing of data across the network.

  • Logical Addressing: Assigns unique IP addresses (IPv4 or IPv6) to devices in a network.

  • Path Determination: Identifies the best route for data to travel from source to destination, even when multiple paths are available.

  • Routing: Managed by routers, which direct packets along the optimal path.

• Data link layer

  The Data Link Layer handles the access to the physical media, managing how data is placed on and received from the network.

  • Media Access Control: Manages the framing of data by attaching the MAC addresses of both sender and receiver to create a frame.

  • Data Placement: Controls how data is placed on the media and retrieved, ensuring it is properly transmitted over the physical network.

• Physical layer

  The Physical Layer is the lowest layer of the OSI model and is responsible for the actual physical connection between devices. It deals with the hardware aspects of data transmission, including the cables, switches, and other physical components.

  • Data Transmission: Converts data into electrical, optical, or radio signals that can be transmitted over a network medium.

  • Media Types: Defines the types of media (e.g., copper wires, fiber optics, wireless) used for transmission.

  • Signal Encoding: Determines how bits are encoded into signals for transmission.

  • Bit Rate Control: Manages the rate at which data is transmitted over the network.

  • Physical Topology: Defines the layout and arrangement of devices on the network, such as star, ring, or mesh typologies.