| OSI Layers | |
Layer |
Function |
| 7. Application | Provides access to the OSI environment for users and also provides distributed information services; electronic mail, file transfers, and other user services |
| 6. Presentation | Provides independence to the application processes from differences in data representation (syntax); Translates data formats, encrypts and decrypts data |
| 5. Session | Provides control structure for communications between applications; establishes, manages, and terminates connections (sessions) between cooperating applications; Synchronizes communications users, and recover from errors. |
| 4. Transport | provides reliable, transparent transfer of data between end points; provides end-to-end error recovery and flow control; Determine network, may assemble and reassemble packets |
| 3. Network | provides upper layers with independence from the data transmission and switching technologies used to connect systems; responsible for establishing, maintaining, and terminating connections; Determine routes; Manages billing information |
| 2. Data Link | provides for the reliable transfer of information across the physical link; sends blocks of data (frames) with the necessary synchronization, error control, and flow control. |
| 1. Physical | concerned with transmission of unstructured bit stream over physical medium; deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium. |
