Network Simulator for Reliable Data Transmission

This project implements a network simulator for two fundamental reliable data transfer protocols: Stop-and-Wait and Go-Back-N. The simulator introduces packet loss and corruption to mimic real-world network behavior and tests how these protocols handle retransmissions and acknowledgments.

Quickstart Guide

Running the Simulator

1. Copy all the contents from this repository.
2. Open a terminal and navigate to the folder containing network_simulator.py.
3. Run the program using:

   python network_simulator.py

4. You will be prompted to select a protocol:
   • Enter 1 for Stop-and-Wait
   • Enter 2 for Go-Back-N

How It Works

• Stop-and-Wait Protocol: Sends one packet at a time and waits for an acknowledgment before sending the next.
• Go-Back-N Protocol: Uses a sliding window to send multiple packets before requiring an acknowledgment.

Core Concepts

• Packet Loss & Corruption: Randomly simulated to test protocol robustness.
• Timeout Handling: Ensures retransmissions if packets are lost.
• Acknowledgments (ACKs) and Negative Acknowledgments (NACKs): Used for communication between sender and receiver.

Preview of Protocol Behavior

Stop-and-Wait

• Sends a packet and waits for an acknowledgment.
• Retransmits if an acknowledgment is lost or corrupted.
• Uses a simple 0/1 sequence number system.

Go-Back-N

• Uses a window size to send multiple packets before requiring an acknowledgment.
• If an error occurs, the sender retransmits the entire window.

Notes:

• This simulator is useful for understanding reliable data transfer in networking.
• The implementation can be extended to Selective Repeat or TCP-like mechanisms.

Example Usage

Select the protocol to test:
1. Stop-and-Wait
2. Go-Back-N
Enter 1 or 2: 1
=== Testing Stop-and-Wait Protocol ===
[Sender][Stop-and-Wait] Sending: Packet(seq=0, data=Message 1)
[Receiver][Stop-and-Wait] Received expected packet: Packet(seq=0, data=Message 1). Sending ACK.
[Sender][Stop-and-Wait] Received ACK: ACK(0). Moving to next packet.
...

Future Enhancements

• Implement Selective Repeat for better error handling.
• Add Graphical Visualization to illustrate packet flow.
• Integrate real network sockets for client-server testing.