OSI model

Partitioning the whole network structures into the abstract layers ISO established a 7 layered architecture named as :-------

7. Application  Network process to application
6. Presentation Data representation, encryption and decryption, convert machine dependent data to machine independent data
5. Session -    Interhost communication, managing sessions between applications
4. Transport     Reliable delivery of packets between points on a network.
3. Network     Addressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.
2. Data link     A reliable direct point-to-point data connection.
1. Physical     A (not necessarily reliable) direct point-to-point data connection.