OSI Network Architecture 7 Layers Model - Simplified

Layer 7: Application Layer
• Defines interface to user processes for communication and data
transfer in network
• Provides standardized services such as virtual terminal, file and job
transfer and operations
Layer 6: Presentation Layer
• Masks the differences of data formats between dissimilar systems
• Specifies architecture-independent data transfer format
• Encodes and decodes data; encrypts and decrypts data; compresses
and decompresses data
Layer 5: Session Layer
• Manages user sessions and dialogues
• Controls establishment and termination of logic links between users
• Reports upper layer errors
Layer 4: Transport Layer

Manages end-to-end message delivery in network
• Provides reliable and sequential packet delivery through
error recovery and flow control mechanisms
• Provides connectionless oriented packet delivery

Layer 3: Network Layer
• Determines how data are transferred between network
devices
• Routes packets according to unique network device addresses
• Provides flow and congestion control to prevent network
resource depletion
Layer 2: Data Link Layer
• Defines procedures for operating the communication
links
• Frames packets
• Detects and corrects packets transmit errors
Layer 1: Physical Layer
• Defines physical means of sending data over network
devices
• Interfaces between network medium and devices
• Defines optical, electrical and mechanical characteristics