Sliding Window Protocols
To study and analyze the performance of various flow control protocols: Stop & Wait, Go-Back-N, and Selective Repeat.
Theory
Sliding Window Protocols are data link layer protocols used for reliable and sequential delivery of data frames. They provide Flow Control to ensure a fast sender doesn't overwhelm a slow receiver.
Stop & Wait ARQ
The sender sends one frame and waits for an acknowledgment (ACK) before sending the next. It is simple but inefficient due to high waiting time.
Go-Back-N (GBN)
Sender can send multiple frames (up to window size 'N') without waiting for ACKs. If a frame is lost, the sender retransmits ALL frames from the lost one onwards. Uses Cumulative ACKs.
Selective Repeat (SR)
Similar to GBN, but ONLY the lost frame is retransmitted. The receiver buffers out-of-order frames. It is more efficient but requires more complex logic at both ends.
Procedure
- Select the Protocol: Stop & Wait, GBN, or Selective Repeat.
- Set the Window Size and Timeout values.
- Start the simulation and observe the sequence numbers of transmitted packets.
- Use the Manual Error Injection buttons to simulate a "Lost Packet" or "Lost ACK".
- Observe the retransmission behavior (Does it resend one packet or the whole window?).
- Analyze the Efficiency and Throughput graphs to compare the three methods.