What is three-bit sliding window protocol?

Sliding window protocol is a transmission control protocol used for reliable data communication. Both sender and receiver maintain finite buffers to hold outgoing and incoming packets, with every packet requiring acknowledgment from the receiver.

The sender maintains a timer for every packet sent, and any unacknowledged packet within a certain time is retransmitted. The sender can transmit a complete window of packets before receiving acknowledgment for the first packet, leading to higher transfer rates as multiple packets are sent without waiting for individual acknowledgments.

The receiver advertises a window size that tells the sender how much data it can receive, preventing buffer overflow at the receiver side.

3-bit Sliding Window Protocol

The 3-bit sliding window protocol is a packet-based data transmission protocol used in the Transmission Control Protocol (TCP) and at the Data Link Layer. It allows transmission of up to 3 frames simultaneously before requiring acknowledgment.

How It Works

Step 1: The sender transmits three frames (1, 2, 3) simultaneously within the sliding window of size 3.

Step 2: After receiving frames from the sender, the receiver sends an acknowledgment (ACK) that includes the sequence number of the next expected frame.

Step 3: Upon receiving ACK 4 (confirming frames 1, 2, 3 were received), the sender's window slides forward, allowing transmission of frames 4, 5, and 6.

Step 4: If the receiver encounters an error while receiving a frame, no ACK is sent back. The sender maintains a timeout for each frame to handle such situations.

Step 5: If the timeout expires without receiving an ACK, the sender retransmits the frame. The receiver accepts the frame if not already received, otherwise ignores the duplicate.

Step 6: When an ACK is lost during transmission from receiver to sender, the same timeout mechanism handles this error condition.

Advantages

• Higher throughput − Multiple frames can be transmitted without waiting for individual acknowledgments

• Efficient bandwidth utilization − Reduces idle time between frame transmissions

• Error recovery − Built-in timeout and retransmission mechanisms ensure reliable delivery

Conclusion

The 3-bit sliding window protocol enables efficient data transmission by allowing up to three frames to be sent simultaneously before requiring acknowledgment. This approach significantly improves network throughput while maintaining reliability through timeout and retransmission mechanisms for error handling.