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Understanding the OSI Model Layers
Sep 14, 2024
OSI Model (Open System Interconnection Model)
Introduction
The OSI Model defines how data is transferred between computers in a network.
It facilitates communication between different architectures (e.g., Windows and MacOS).
Introduced by the International Organization for Standardization (ISO) in 1984.
Structure of the OSI Model
The OSI Model consists of
7 Layers
:
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Each layer has its own set of protocols.
Layer Descriptions
1. Application Layer
Used by network applications (e.g., Google Chrome, Outlook, Skype).
Functions include:
File transfer (FTP)
Web surfing (HTTP/HTTPS)
Email (SMTP)
Virtual terminals (Telnet)
2. Presentation Layer
Converts data into a machine-readable format (e.g., ASCII to FCD).
Functions include:
Translation
: Converts character formats.
Compression
: Reduces file size (lossy or lossless).
Encryption/Decryption
: Uses SSL for secure data transmission.
3. Session Layer
Manages connections between applications.
Functions include:
Session Management
: Tracks files being downloaded.
Authentication
: Verifies user identity (username/password).
Authorization
: Checks user permissions.
4. Transport Layer
Ensures reliable communication via:
Segmentation
: Divides data into smaller segments.
Flow Control
: Adjusts data transmission rate to prevent overload.
Error Control
: Resends lost or corrupted data using checksums.
Protocols: TCP (Connection Oriented) and UDP (Connectionless).
5. Network Layer
Transmits data packets between different networks.
Functions include:
Logical Addressing
: Assigns unique IP addresses.
Routing
: Determines the best path for data packets.
Path Determination
: Chooses optimal delivery routes.
6. Data Link Layer
Receives data packets and adds physical addresses (MAC addresses).
Functions include:
Framing
: Converts packets to frames for transmission.
Media Access Control
: Manages how devices access shared media.
Error Detection
: Identifies transmission errors.
7. Physical Layer
Converts binary data into electrical, light, or radio signals for transmission.
Receives and converts signals back to bits for higher layers.
Conclusion
The OSI model underpins the functioning of the internet by facilitating communication between devices across different networks.
Each layer plays a crucial role in ensuring reliable data transmission.
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