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




Layer 2: Data Link Layer
Defines procedures for operating the communication links
Frames packets
Detects and corrects packets transmit errors


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 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 5: Session Layer
Manages user sessions and dialogues
Controls establishment and termination of logic links between users
Reports upper layer errors


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 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