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The 7 OSI layers - Coggle Diagram
The 7 OSI layers
Physical Layer
Function
It transmits raw bits over a physical medium (like cables or wireless signals) and defines hardware specifications, including electrical signals, cable specifications, and network interface cards.
Definition
The Physical Layer is the lowest layer of the OSI model, responsible for the physical connection between devices.
Examples
Ethernet cables, fiber optics, Bluetooth, and network interface cards (NICs).
Network layer
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Function
It manages logical addressing (IP addresses) and determines the best path for data to travel from the source to the destination, enabling communication between devices on different networks.
Examples
IP (Internet Protocol), routers, and Layer 3 switches.
Presentation Layer
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Function
It formats and encrypts data for the application layer, handles data compression and conversion, and ensures that data is in a usable format for the receiving application, enabling interoperability between different systems.
Examples
SSL/TLS for encryption, data format conversions like JPEG, MPEG, or ASCII.
Transport Layer
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Function
It segments data into packets for transmission, provides error recovery and flow control, and maintains the order of packets. It uses protocols like TCP for reliable communication and UDP for faster, less reliable communication.
Examples
TCP (Transmission Control Protocol), UDP (User Datagram Protocol).
Session Layer
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Function
It establishes, maintains, and terminates connections, synchronizes data exchange, and provides control mechanisms for dialog between applications, ensuring organized and effective communication.
Examples
Remote procedure call (RPC), Session Initiation Protocol (SIP).
Application Layer
Definition
The Application Layer is the topmost layer that provides network services directly to user applications.
Function
It includes protocols that enable software applications to communicate over the network, facilitating user interaction and providing services like file transfers, email, and web browsing.
Examples
HTTP (web browsing), FTP (file transfer), SMTP (email), and DNS (domain name resolution).
Data Link
Function
It organizes data into frames, addresses these frames for correct delivery on the local network, and manages access to the physical medium, ensuring reliable communication between directly connected devices.
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Examples
Ethernet (MAC addressing), Wi-Fi (802.11 protocols), and switches.