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Theory

OSI Model

The Open Systems Interconnection (OSI) model is a classic seven-layer conceptual framework used for teaching network architecture, ordered from physical signaling at the bottom to end-user software at the top:

  1. Physical Layer: Handles transmission of raw signals over physical cables, radio frequencies, and voltages.
  2. Data Link Layer: Manages point-to-point data transfer between directly connected devices using hardware MAC addresses.
  3. Network Layer: Routes data packets across multiple interconnected networks using IP addresses.
  4. Transport Layer: Coordinates end-to-end delivery of messages between running programs using protocols such as TCP and UDP.
  5. Session Layer: Establishes and manages ongoing communication sessions between applications.
  6. Presentation Layer: Handles data formatting, translation, and encryption.
  7. Application Layer: Interfaces directly with user-facing software, such as web browsers and email clients.

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Updated 2026-09-10

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Prep Sessions

Network Architecture and Data Flow: From Packets to Protocols @ University of Michigan - Ann Arbor

Ch.1 Network Foundations and Models - Network Architecture and Data Flow: From Packets to Protocols @ University of Michigan - Ann Arbor

The OSI and TCP/IP Layered Models - Network Architecture and Data Flow: From Packets to Protocols @ University of Michigan - Ann Arbor