SDN Packet Drop Simulator using Mininet and Ryu

Problem Statement

This project implements a Software Defined Networking (SDN) solution using Mininet and a Ryu OpenFlow controller to simulate and analyze packet dropping behavior between hosts.

The objective is to demonstrate:

• Controller–switch interaction
• Flow rule design (match–action)
• Network behavior observation under different conditions

As required in the assignment :contentReference[oaicite:1]{index=1}, the system showcases forwarding, filtering, monitoring, and performance analysis.

---

Project Overview

The system consists of:

• A Mininet topology (tree topology with 4 hosts, 3 switches)
• A Ryu controller implementing:
  • Learning switch behavior
  • Selective packet drop rules
  • REST APIs for control and monitoring
• A measurement script for packet loss evaluation

---

Network Topology

 [Controller]
      |
    [s1]
   /     \
[s2]     [s3]
/ \       / \
h1   h2  h3   h4

• Hosts: h1–h4 (10.0.0.1 – 10.0.0.4)
• Switches: OpenFlow 1.3
• Controller: Ryu (remote)

---

Features Implemented

1. Learning Switch (Forwarding)

• MAC learning using packet_in
• Dynamic flow installation
• Reduces controller overhead

2. Packet Drop Simulation

• Selective drop rules using OpenFlow
• Match fields:
  • IP (src/dst)
  • MAC (optional)
  • Protocol (TCP/UDP/ICMP)

3. REST APIs

Endpoint	Description
POST /drop_rules	Install drop rule
DELETE /drop_rules	Remove drop rules
GET /event_log	View packet logs
GET /metrics	Per-flow packet loss

4. Per-Flow Packet Loss Measurement

• Uses OpenFlow flow statistics
• Computes: loss % = dropped / (dropped + forwarded)
• Provides structured output per connection

5. Event Logging

• Logs all packet_in events
• Includes MAC, IP, timestamp

---

Workflow

Step 1: Start Controller

ryu-manager packet_drop_controller.py

Step 2: Start Mininet

sudo python3 topology.py

Step 3: Baseline Test

mininet> pingall

Step 4: Apply Drop Rule

curl -X POST http://localhost:8080/drop_rules -d '{"src_ip":"10.0.0.1","dst_ip":"10.0.0.2"}'

Step 5: Test Packet Loss

mininet> h1 ping h2

Step 6: Measure Metrics

curl http://localhost:8080/metrics

---

Output

Running RYU controller :

Running Toplogy.py :

Base connectivity:

Applying Drop rule:

After Applying Drop Rule:

Flow tables:

Metrics :

Clearring the drop rules

After clearing drop rules:

Auntomated measurement script

Test Scenarios

🔹 Scenario 1: Normal Operation No drop rules Expected: 0% packet loss

🔹 Scenario 2: Packet Drop Drop rule applied Expected: 100% packet loss

🔹 Scenario 3: Recovery Drop rules removed Expected: Network restored

Regression Testing

The system verifies:

Drop rules are correctly installed

Drop rules are removed precisely

Forwarding rules remain unaffected

Apply drop → Verify loss → Remove drop → Verify recovery

Key Design Decisions

Reactive learning switch (simpler + realistic SDN)

Priority-based rule control:

Drop: 200

Forward: 100

REST-based control for flexibility

Flow stats used for analytics

Challenges Faced

Flow matching conflicts (MAC vs IP)

Drop rules not triggering due to existing flows

OpenFlow counters not updating for drop rules

Synchronization delays in stats collection

Technologies Used

Python 3

Ryu Controller

Mininet

OpenFlow 1.3

cURL (API testing)

Project Structure

SDN/

├── packet_drop_controller.py

├── topology.py

├── measure1.sh

├── README.md

📸 Proof of Execution

Conclusion

This project successfully demonstrates:

SDN-based traffic control

Flow rule design and enforcement

Real-time packet loss analysis

Automated evaluation and validation

References

Ryu Documentation

Mininet Documentation

OpenFlow Specification

---