Explanation:

In the OSI (Open Systems Interconnection) model, there are 7 layers, each with specific responsibilities. The Transport layer, which is Layer 4, plays a key role in ensuring that data is delivered from the source to the destination across the network reliably and in the correct order.

Here's how it works:

• When a large message (like a file or a video) needs to be sent over the network, the Transport layer breaks it into smaller chunks called segments.
• Each segment is given a sequence number, so the receiver can reassemble them in the correct order.
• It also provides error checking and retransmission in case any segment gets lost or corrupted (using protocols like TCP).
• This layer ensures that the entire message is delivered correctly from one end to another, not just from one router to another (which is the job of the Network layer).

So, the Transport layer is responsible for end-to-end communication, which includes:

• Segmenting and reassembling data
• Ensuring reliable data transfer
• Flow and error control