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The OSI Model: Layers 7, 6, and 5 (Application, Presentation, Session)

CCNA: 0 to Hero - Comprehensive Network Engineering Bootcamp

Lesson 3: The OSI Model: Layers 7, 6, and 5

The Open Systems Interconnection (OSI) Model is a conceptual framework used to understand how different networking technologies and protocols interact. It divides communication into seven distinct layers.

Layer 7: Application Layer

  • Purpose: Interface between the network and the user applications. This is where users interact with the network.
  • Protocols: HTTP, HTTPS, FTP, SMTP, POP3, DNS.
  • Data Unit: Data.

Layer 6: Presentation Layer

  • Purpose: Ensures that data is readable by the receiving application. Handles data formatting, encryption, and compression.
  • Protocols/Standards: JPEG, MPEG, ASCII, TLS/SSL (handling encryption/decryption).
  • Data Unit: Data.

Layer 5: Session Layer

  • Purpose: Manages the communication session between applications. Sets up, coordinates, and terminates conversations (sessions).
  • Functions: Dialog control (who talks when) and synchronization (inserting checkpoints in data streams).
  • Data Unit: Data.