CN

Sliding Window Protocols

Hard
EST. TIME: 45 min

Sliding Window Protocols

To visualize Sliding Window Protocols (Stop & Wait, Go-Back-N, Selective Repeat).

Theory & Concepts

Click to collapse detailed explanation

1. Introduction

Flow control protocols enable reliable data transfer between a sender and receiver. They ensure the sender does not overwhelm the receiver and that lost frames are retransmitted.

2. Protocol Types

Stop-and-Wait ARQ

Sender sends one frame, stops, and waits for ACK. Very inefficient for long distances (high propagation delay).

Go-Back-N (GBN)

Sender sends up to N frames (Window Size). If Frame X is lost, Receiver discards all subsequent frames. Sender retransmits everything from X.

Selective Repeat (SR)

Receiver accepts out-of-order frames and buffers them. Sender **only** retransmits the lost Frame X. Most efficient but complex.

3. Mathematical Efficiency

Efficiency (η) = N / (1 + 2a)

Where N is Window Size and a is (Propagation Time / Transmission Time). GBN and SR utilize the bandwidth much better than Stop-and-Wait because multiple frames are in flight simultaneously.

Procedure

1

Configure Window

Set Window Size (N=4). Select Protocol (e.g., GBN).

2

Inject Error

While simulation runs, click "Kill Packet 2".

3

Observe Recovery

See GBN resend 2, 3, 4. Then switch to Selective Repeat and see it resend ONLY 2.

Learning Resources

Animated Lecture

Sliding Window Protocols

Reference Notes

Protocol Comparison

Self Quiz

Sliding Window Quiz

Ready to Start?

Launch the virtual simulator to visualize the network layers and verify protocols.

Lab Status

Active Simulation

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