Sliding Window Protocol

Summary

In this lecture, the instructor explores the differences between the stop-and-wait ARQ protocol and the sliding window protocol. The session begins by addressing the drawbacks of the stop-and-wait ARQ protocol, such as poor bandwidth utilization and performance. Then, the sliding window protocol is introduced as a solution, allowing multiple frames to be sent before expecting an acknowledgment. The working of the sliding window protocol is explained in detail, highlighting how the sender and receiver manage frames and acknowledgments based on the window size. The session concludes with an overview of the key takeaways and the importance of sliding window protocols in improving communication efficiency.

Takeaways

• 😀 The Stop-and-Wait ARQ protocol sends one frame at a time, waiting for an acknowledgment before sending the next.
• 😀 If an acknowledgment is not received within a certain time, the sender times out and retransmits the frame.
• 😀 One major drawback of the Stop-and-Wait ARQ protocol is poor bandwidth utilization, especially with high-bandwidth channels.
• 😀 The Stop-and-Wait ARQ protocol leads to poor performance because it doesn't efficiently use the available bandwidth.
• 😀 The Sliding Window protocol allows sending multiple frames at a time, improving efficiency compared to Stop-and-Wait.
• 😀 The number of frames that can be sent at a time in the Sliding Window protocol is determined by the 'window size.'
• 😀 In the Sliding Window protocol, frames are numbered, and each frame is sent until the window size is exhausted or acknowledged.
• 😀 As the sender receives acknowledgments, the sliding window moves, allowing the transmission of the next frames.
• 😀 The Sliding Window protocol improves performance by enabling multiple frames to be transmitted before waiting for acknowledgments.
• 😀 The receiver acknowledges frames, and the sender proceeds to send the next frame once an acknowledgment is received.
• 😀 The Sliding Window protocol helps achieve better bandwidth utilization and reduces the transmission delay compared to Stop-and-Wait.

Q & A

What is the main concept behind the Stop-and-Wait ARQ protocol?

The Stop-and-Wait ARQ protocol allows the sender to send one frame at a time. After sending a frame, the sender waits for an acknowledgment before sending the next frame.

What are the major drawbacks of the Stop-and-Wait ARQ protocol?

The major drawbacks are poor bandwidth utilization, as only one frame is sent at a time, and poor performance when the bandwidth is underutilized, especially in high-speed networks.

How does the Sliding Window protocol improve upon the Stop-and-Wait ARQ protocol?

The Sliding Window protocol allows multiple frames to be sent before waiting for an acknowledgment. The number of frames that can be sent at once is determined by the window size, thus improving bandwidth utilization and performance.

What determines how many frames can be sent at once in the Sliding Window protocol?

The number of frames that can be sent at once is determined by a parameter called the 'window size'. The sender can transmit as many frames as the window size allows before needing acknowledgment.

What happens when the sender receives an acknowledgment for a frame in the Sliding Window protocol?

When the sender receives an acknowledgment for a frame, the window slides to include the next unacknowledged frame, allowing the sender to transmit the next frame in the buffer.

In the Sliding Window protocol, how does the sender handle multiple frames?

The sender sends multiple frames based on the window size without waiting for acknowledgment after each one. The sender waits for acknowledgment before sending additional frames, sliding the window accordingly.

Why is the Sliding Window protocol more efficient than Stop-and-Wait?

The Sliding Window protocol is more efficient because it allows multiple frames to be sent at once, reducing idle time and better utilizing available bandwidth, leading to improved overall performance.

What does the 'window size' refer to in the context of the Sliding Window protocol?

The 'window size' refers to the number of frames that can be sent before waiting for acknowledgment. It is a key parameter that defines how many frames the sender can transmit before needing to receive confirmation for earlier frames.

In the Sliding Window protocol, what happens when a frame is acknowledged?

When a frame is acknowledged, the sliding window moves forward, and the sender can send the next unacknowledged frame, keeping the process continuous and efficient.

Can the sender send frames with numbers greater than the window size in the Sliding Window protocol?

No, the sender cannot send frames with numbers greater than the current window size. The window limits how many frames can be sent at a time, and any frame beyond that is held back until the window slides to accommodate it.