Describe the sliding window flow control mechanism used in TCP.

What will be an ideal response?

Flow control is about preventing overrunning the receiver with information. Therefore, the receiver sends flow control information to the sender and sender reduces its amount of sending information. This is implemented by the sliding window control:
1. The window closes as the left edge advances to the right. This happens when data is
sent and acknowledge.
2. The window opens when the right edge moves to the right, allowing more data to be sent. This happens when the receiving process on the other end reads acknowledged data, freeing up space in its TCP receive buffer.
3. The window shrinks when the right edge moves to the left. The Host Requirements RFC strongly discourages this, but TCP must be able to cope with a peer that does this.