The fourth layer of the osi reference model is transport layer. It is responsible for the reliable delivery of the data or information.
The transport layer is responsible for setting up actual mechanics, maintaining and tearing down a connection for providing a reliable and unreliable data delivery. For reliable connections, the transport layer is responsible for error detection and correction. When an error is detected, the transport layer will resend the data.
For unreliable connections, the transport layer provides only error detection that is error correction is left up to one of the higher layers. This layer ensures that the message arrives error free, intact and in order with flow control. For security, the layer may create connection between two end nodes.
This layer provides multiplexing by providing multiple process of the computer to communicate. So the layer4 data header should have address for the process in the computer. The main role of the layer 4 is to provide the communication services directly to the application processes running on different hosts.
Functions of transport layer
- Provides reliable and unreliable delivery of data across the connection.
- Segmenting data into smaller and more manageable sizes.
- Allowing multiplexing connections and multiple applications to send and receive data simultaneously.
- Layer4 uses some standard protocols such as TCP, UDP, DCCP etc to enhance its functionalities.
- This layer treats each packet independently because each packet belongs to a different message.
- The layer 4 ensures that each message should reach its destination completely.
- All layer 4 protocols provide multiplexing/demultiplexing service.