OSI Model and Communication Layers

This flashcard set covers the OSI (Open Systems Interconnection) model — a foundational concept in computer and industrial networks. Each card explains one of the seven OSI layers, their functions, and examples of protocols used in automation and industrial communication.

What does OSI stand for?

Open Systems Interconnection — a 7-layer model that standardizes how network communication occurs.

What is Layer 1 of the OSI Model?

Physical Layer — Transmits raw bits through physical media like cables, voltage, or radio signals. Examples: Ethernet cable, RS-232, RS-485.

What is Layer 2 of the OSI Model?

Data Link Layer — Handles data frames, MAC addressing, and error detection between directly connected nodes. Examples: Ethernet, Modbus RTU.

What is Layer 3 of the OSI Model?

Network Layer — Routes packets using logical addressing (IP). Examples: IP, ICMP.

What is Layer 4 of the OSI Model?

Transport Layer — Ensures reliable or fast delivery of data between hosts. Examples: TCP, UDP.

What is Layer 5 of the OSI Model?

Session Layer — Establishes, manages, and terminates communication sessions. Examples: RPC, NetBIOS.

What is Layer 6 of the OSI Model?

Presentation Layer — Translates, encrypts, or compresses data for the application layer. Examples: SSL/TLS, ASCII, JPEG.

What is Layer 7 of the OSI Model?

Application Layer — Provides network services and interfaces for end-user applications. Examples: HTTP, FTP, Modbus TCP, PROFINET.

What is the easiest way to remember the OSI layers?

"Please Do Not Throw Sausage Pizza Away" — Physical, Data Link, Network, Transport, Session, Presentation, Application.