MCQ Detailed View

The Transport Layer (Layer 4 of the OSI model) is mainly responsible for reliable data delivery between devices and controlling the flow of data. It ensures that messages are delivered accurately and in the correct order, even if they are split into smaller pieces (segments).

This layer handles segmentation, error checking, retransmission if necessary, and flow control to avoid congestion. It uses protocols like TCP (Transmission Control Protocol) for reliable communication and UDP (User Datagram Protocol) for faster, connectionless communication.

Main responsibilities of the Transport Layer:

• Ensures complete and correct delivery of data.


• Breaks data into segments and reassembles them at the receiver’s end.


• Controls the rate of data flow to avoid overload (flow control).


• Handles retransmission if data is lost or corrupted (error recovery).

Other options explained:

• Physical signal transmission is done by the Physical Layer.


• Error correction on frames is the role of the Data Link Layer.


• Routing of packets is handled by the Network Layer.

Conclusion: The correct answer is Reliable data delivery and flow control, which is the key function of the Transport Layer in the OSI model.