In 1970, the International Organization for Standardization (ISO) has developed a seven-layer model, LAN architectures. In parallel, the ISO has developed a protocol to fit the model. Since then, other models such as the five-layer TCP / IP model was developed, but the OSI model is still used to map and categorize protocols because of the clear and unambiguous manner representative network functions. The OSI model contain 7 layers
• To allow access to network resources.
• Enables the user either human or software to access the network.
• It provides user interface and support for the services such as Electronic mail, Remote File se Management and other services.
• To translate, encrypt, and compress data.
• This layer is connected with Semantic and syntax of info exchange between two systems.
• Function of presentation Layer are
4) Transport Layer
• To provide reliable end-to-end message delivery and error recovery.
• Responsible for source to destination delivery for entire message.
• Network layer oversees source-to-destination delivery of the entire packets but it does not recognize any relationship b/w those packets.
• Responsible for source –to-destination.
• Dl Layer oversees the delivery of data between 2 systems on the same network.
• Network Layer ensures that each packet gets from its point of origin to its final destination.
2) Data link layer
• Coordinates the functions required to transmit a bit stream over a physical medium.
• Deals with electronic and mechanical specification.
• Also defines and function that physical devices and interfaces need to perform for TX.