4.Example of OSI layer?
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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