| Layer | Functions | Facilities |
| 7 - Application | Interface to the Host O/S, User Accounting and Security, O/S Services | Services, Control and Accounting |
| 6 - Presentation | Compression/Decompression, Encryption/Decryption, ASCII/EBCDIC Translations, Data Reformating |
| 5 - Session | Multiplexing, Initiation, Management and Termination of Sessions | Logical Connection |
| 4 - Transport | Data Handling, End-to-End Reliability |
| 3 - Network | Packets: Addressing, Subnet Accounting |
| 2 - Data Link | Frames: Node-to-Node Reliability | Physical Connection |
| 1 - Physical | Bits: Connector, Voltages, Pins |
