The Open System Interconnection (OSI) Model provides an abstract description of the network communication process. International Organization for Standard (ISO) develops it to provide a road map for non-proprietary protocol development. The OSI model is just a reference model and many of OSI protocols are no longer in use. There are seven layers in OSI Model. Those are as follows:
Layer 7 - Application
Performs services for the application used by the end users.
Layer 6 - Presentation
Provides data format information to the application.
Layer 5 - Session
Manages session between users.
Layer 4 - Transport
Defines data segments and numbers them at the source, transfers the data, and reassembles the data at the destination.
Layer 3 - Network
Creates and addresses packets for end-to-end delivery through intermediary devices in other network.
Layer 2 - Data Link
Creates and addresses frames for host-to-host delivery on the local LANs and between WAN devices.
Layer 1 - Physical
Transmits binary data over media between devices. Physical layer protocols define media specifications.
TCP / IP is an open standard. The rules and implementation of the TCP/IP model were cooperatively developed by members of the industry using Request for Comments (RFC) documents. There are four layers in TCP/IP Model. Those are as follows:
Layer 4 - Application
Represents application data to the user.
Layer 3 - Transport
Supports communication between devices and performs error correction.
Layer 2 - Internet
Finds the best path through the network.
Layer 1 - Network access
Controls hardware devices and media.
Comparison of OSI and TCP / IP Model
|7. Application||4. Application|
| 6. Presentation
| 5. Session
| 4. Transport
|3. Network|| 2. Internet
|2. Data Link|| 1. Network Access