THE 7 LAYERS OF THE OSI MODEL

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 devicesDefines optical, electrical and mechanical characteristics