📌 Overview

This project implements a TCP-like protocol over UDP with reliability and congestion control mechanisms at the application layer.
It was developed as part of the COL334/672 (Computer Networks) course assignment at IIT Delhi.

The system extends raw UDP with:

• Reliable transmission (ACKs, retransmissions, fast recovery, cumulative ACKs).
• Congestion control (TCP Reno & TCP CUBIC).
• Performance analysis (loss, delay, fairness) using Mininet and Ryu controller.

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🗂 Assignment Parts

1. Reliability over UDP

   • Packet sequencing, ACKs, retransmissions.
   • Fast retransmit & recovery.
   • Timeout estimation for packet loss recovery.
   • Performance evaluation under varying loss/delay.

2. Congestion Control (TCP Reno)

   • Slow start, congestion avoidance.
   • Fast recovery & timeout handling.
   • Throughput and fairness analysis using dumbbell topology.

3. Bonus: TCP CUBIC

   • Cubic window growth function.
   • Comparative analysis vs TCP Reno for efficiency & fairness.

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⚙️ Implementation Details

• Language: Python 3
• Topology Simulation: Mininet with Ryu SDN controller
• Packet Serialization: JSON format
• Protocols Implemented:
  • Reliability (ACKs, retransmissions, fast recovery)
  • TCP Reno congestion control
  • TCP CUBIC congestion control

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🧪 Experiments & Results

• Loss vs Transmission Time: Effect of fast recovery under 0–5% loss.
• Delay vs Transmission Time: Performance with 0–200 ms delay.
• Throughput Analysis: TCP Reno throughput under varying loss/delay.
• Fairness: Jain’s fairness index for Reno/Reno and Reno/CUBIC competition.

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▶️ How to Run

Part 1: Reliability

Run server:

python3 p1_server.py <SERVER_IP> <SERVER_PORT> <FAST_RECOVERY_BOOL>
Run client:

bash
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python3 p1_client.py <SERVER_IP> <SERVER_PORT>
Part 2: Congestion Control (TCP Reno)
Run server:

bash
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python3 p2_server.py <SERVER_IP> <SERVER_PORT>
Run client:

bash
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python3 p2_client.py <SERVER_IP> <SERVER_PORT> --pref_outfile <PREFIX>
Part 3: TCP CUBIC
Similar usage as Part 2 with congestion control flag set to CUBIC.