Solution

The correct answer is Option 4.

Key Points

• The sliding window protocol for flow control involves the following stages:
  • B. Sender sends a window of frames.
  • C. Receiver acknowledges the received frames.
  • A. Sender moves the window to the next set of frames.
  • D. If acknowledgment is not received, Sender retransmits the frame.
• Therefore, the correct sequence is Option 1: B, C, A,  D.

Additional Information

• In the sliding window protocol, the sender can send multiple frames before needing an acknowledgment for the first frame.
• The window size determines the number of frames the sender can send without receiving an acknowledgment.
• This protocol helps in efficient use of network bandwidth and reduces the waiting time for acknowledgments.