| Layer |
Function |
| Layer 7 | Application |
| Layer 7 | provides network services to application processes (such as e-mail, file transfer & terminal emulation) |
| Layer 7 | the interface that allows the application (program) to communicate |
| Layer 6 | Presentation |
| Layer 6 | Like an interpreter |
| Layer 6 | Data representation |
| Layer 6 | ensure that data is readable by the receiving system |
| Layer 6 | format of data |
| Layer 6 | data structures |
| Layer 6 | negotiates data transfer syntax for application layer |
| Layer 5 | Session |
| Layer 5 | interhost communication |
| Layer 5 | establishes, manages, and terminates sessions between application |
| Layer 4 | Transport |
| Layer 4 | end-to-end connection reliability |
| Layer 4 | ensures integrity of data |
| Layer 4 | concerned with data transport issues between hosts |
| Layer 4 | data transport reliability |
| Layer 4 | establish, maintain, terminate virtual circuits |
| Layer 4 | fault detection and recovery |
| Layer 4 | information flow control |
| Layer 4 | TCP: Transmission Control Protocol |
| Layer 3 | Network |
| Layer 3 | Addresses & best path |
| Layer 3 | provides connectivity and path selection between two end systems |
| Layer 3 | domain of routing |
| Layer 3 | IP: Internet Protocol |
| Layer 3 | Logical Addresses |
| Layer 2 | Data Link |
| Layer 2 | Access to media |
| Layer 2 | provides reliable transfer of data across media |
| Layer 2 | physical address, network topology, error notification, flow control |
| Layer 2 | physical address: MAC address (Media Access Control) |
| Layers 2 & 3 | only layers concerned with addressing |
| Layer 2 | Protocol: Ethernet |
| Layer 2 | Protocol: Frame Relay |
| Layer 1 | Physical |
| Layer 1 | binary transmission |
| Layer 1 | wires, connectors, voltages, data rates |
