# User:OSI Model

## Open System Interconnection (OSI) Model

Objectives
 1. It is a layered frame work for design of network systems that allows for communication across all types of computers systems. 2. An Open System is a model that allows any two different computers or systems to communicate regardless of their underlying architecture. 3. The OSI model is not a protocol. 4. It is a model for understanding and designing a network architecture that is flexible, robust and interoperable. 5. The OSI model acts as a baseline for creating and comparing networking protocols. 6. The goal of this model is to break down the task of data communication into simple steps, these steps are called layers. 7. The OSI model consists of seven distinct layers namely Physical layer, Datalink layer, Network layer, Transport layer, Session layer, Presentation layer and Application Layer and each layer has certain responsibilities.

Key points
 The benefits of the OSI model are as follows: 1.Any hardware or software that meets the OSI standard will be able to communicate with any other hardware or software that also meets the standard. 2.Hardware or software from any manufacturer will work together. 3.The Protocols for OSI are defined at each stage. 4.Any errors that occur are handled in each layer. 5.The different layers can operate automatically.

Definition
 Upper layers convert and format the information into data and send it to the Transport Layer.The Transport layer turns the data into segments and adds headers then sends them to the Network layer.The Network layer receives the segments and converts them into packets and adds header information (logical addressing) and sends them to the Data Link Layer.The Data Link layer receives the packets and converts them into frames and adds header information (physical source and destination addresses) and sends the frames to the Physical Layer.The Physical layer receives the frames and converts them into bits to be put on the network medium.In Summary  Data >> Segments >> Packets >> Frames >> Bits