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NETWORK SIMULATION MASTERY NS3 GNS3

In the real world, testing a new routing protocol or a 5G handover algorithm on live hardware is catastrophic. Network simulation is the wind tunnel for internet engineering.

Learn Network Simulation: From Zero to Simulation Master

Goal: Deeply understand the mechanics of network simulation and emulation—how to model complex topologies, analyze the physics of packet flow, and verify protocol convergence in virtual environments using NS-3 and GNS3. You will move from simple link modeling to architecting massive, multi-vendor simulated infrastructures that mirror real-world performance.

Why Network Simulation Matters

In the real world, testing a new routing protocol or a 5G handover algorithm on live hardware is catastrophic. Network simulation is the “wind tunnel” for internet engineering.

Historical Context: Before simulators like NS-2 and NS-3, researchers had to rely on mathematical models that often failed to capture the “chaos” of real-world collisions and congestion.
Real-World Impact: Every major network hardware release (Cisco, Juniper, Nokia) and every new protocol (QUIC, 5G, Wi-Fi 7) is validated in high-fidelity simulations before a single cable is plugged in.
Why it remains relevant: As networks move toward SDN (Software Defined Networking) and 5G/6G, the complexity makes manual prediction impossible. Simulation is the only way to “see” the bottleneck before it happens.
What understanding this unlocks: You gain the ability to predict system behavior, debug global-scale outages in a safe environment, and prove architectural theories with hard data.

Core Concept Analysis

1. Simulation vs. Emulation: The Fundamental Divide

Understanding the difference between NS-3 (Simulation) and GNS3 (Emulation) is the first step toward mastery.

      NETWORK SIMULATION (NS-3)              NETWORK EMULATION (GNS3)
    ┌───────────────────────────┐          ┌───────────────────────────┐
    │  Mathematical Models      │          │  Real Operating Systems   │
    │  (Discrete Event)         │          │  (IOS, Junos, Linux)      │
    ├───────────────────────────┤          ├───────────────────────────┤
    │ Abstract, fast, scalable  │          │ Heavy, high-fidelity      │
    ├───────────────────────────┤          ├───────────────────────────┤
    │ "At time T, send packet"  │          │ "Run actual .bin file"    │
    └─────────────┬─────────────┘          └─────────────┬─────────────┘
                  │                                      │
           Focus: Performance                     Focus: Configuration
           Protocol Design                        Network Operations

2. Discrete Event Simulation (DES)

Most network simulators use DES. Unlike a video game that updates 60 times a second, a DES only “ticks” when something happens (an event).

The Event Scheduler Flow:

Time 0.0:  Event A (Node 1 sends Packet)
           - Process Event A
           - Schedule Event B (Packet arrives at Node 2) at Time 0.05
Time 0.05: Event B (Node 2 receives Packet)
           - Process Event B
           - Schedule Event C (Node 2 sends ACK) at Time 0.06
... [Simulator skips the dead time between 0.0 and 0.05] ...

3. The ISO/OSI Mapping in Code

In a simulator, “layers” are just objects and callbacks.

NetDevice: The virtual NIC.
Channel: The virtual wire/air (calculates propagation delay and loss).
Node: The container for stacks and applications.

The Simulation Stack: How it Fits Together

   [ Application Layer ] -> OnOffApplication, BulkSend
            ↓
   [ Transport Layer ]   -> TCP (Reno, Cubic), UDP
            ↓
   [ Network Layer ]     -> IPv4, IPv6, OSPF, BGP
            ↓
   [ Link/MAC Layer ]    -> Point-to-Point, CSMA (Ethernet), 802.11 (Wi-Fi)
            ↓
   [ Physical Layer ]    -> ErrorModels, Propagation Loss

Concept Summary Table

Concept Cluster	What You Need to Internalize
Discrete Event Engine	Time is non-linear. The simulation jumps from event to event, and everything is a timestamped callback.
Propagation & Loss Models	Signal strength isn’t binary. You must understand how distance, frequency, and interference affect packet success.
Topology Abstraction	Nodes, Channels, and NetDevices are the “Legos”. You build complex worlds by connecting these primitives.
Trace-Driven Analysis	The simulator’s job is to produce data (pcap, ASCII traces). Your job is to parse it to find the truth.
Convergence Dynamics	Routers don’t just “work”. They exchange state over time. You must observe the “settling period” of a protocol.

Deep Dive Reading by Concept

This section maps each concept to specific book chapters for deeper understanding. Read these before or alongside the projects.

Simulation Foundations

Concept	Book & Chapter
Discrete Event Principles	“Simulation Modeling and Analysis” by Averill M. Law — Ch. 1: “Basic Simulation Modeling”
Randomness in Networks	“Discrete-Event System Simulation” by Jerry Banks — Ch. 7: “Random-Number Generation”
NS-3 Architecture	“Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti — Ch. 2: “ns-3 Architecture”

Protocol & Topology Mastery

Concept	Book & Chapter
GNS3 Setup & Basics	“The Book of GNS3” by Jason C. Neumann — Ch. 2: “Installing GNS3”
Routing Convergence	“TCP/IP Illustrated, Vol 1” by W. Richard Stevens — Ch. 18: “Routing”
Wi-Fi Modeling	“Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti — Ch. 5: “Wireless Networks”

Essential Reading Order

Foundation (Week 1):
- Simulation Modeling and Analysis Ch. 1 (To understand the DES loop)
- Advanced Network Simulations Simplified Ch. 1-2 (To get NS-3 running)
The “Networking” in Simulation (Week 2):
Project 1: The OSPF Triangle (Emulation Mastery)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: Cisco IOS (CLI) / GNS3
Alternative Programming Languages: VyOS, Arista EOS
Coolness Level: Level 2: Practical but Forgettable
Business Potential: 1. The “Resume Gold”
Difficulty: Level 1: Beginner
Knowledge Area: Routing Protocols / Network Emulation
Software or Tool: GNS3, Wireshark, Cisco IOS Images
Main Book: “The Book of GNS3” by Jason C. Neumann

What you’ll build: A triangle topology of three Cisco routers running OSPF. You will observe how the network “discovers” itself and how traffic reroutes when a link is manually “cut”.

Why it teaches Routing Convergence: This project makes the “magic” of OSPF visible. You aren’t just reading about Hello packets and LSAs; you’re watching them appear in Wireshark and seeing the routing table update in real-time.

Core challenges you’ll face:

Configuring GNS3 VM and IOS Images → maps to understanding hypervisors and virtualization
Synchronizing OSPF Neighbors → maps to understanding OSPF states (Init, 2-Way, ExStart, Full)
Capturing the “Convergence Event” → maps to analyzing packet timing and reconvergence speed

Key Concepts:

OSPF Hello Protocol: “TCP/IP Illustrated, Vol 1” Ch. 18 - W. Richard Stevens
GNS3 Packet Capture: “The Book of GNS3” Ch. 6 - Jason C. Neumann

Difficulty: Beginner Time estimate: Weekend Prerequisites: Basic understanding of IP addressing and Command Line.

Real World Outcome

You’ll have a running GNS3 lab where three routers form a triangle. You will prove convergence by shutting down an interface and watching the ping continue via the alternate path with minimal loss.

Example Output:

# On Router A, pinging Router C
R1# ping 192.168.3.1 repeat 1000
Sending 1000, 100-byte ICMP Echos to 192.168.3.1, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!U.!!U.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
# (The 'U' and '.' show the brief moment of convergence when a link failed)

# Wireshark trace will show:
# Time: 12.001 -> OSPF LS Update (Link State ID: 192.168.1.0)
# Time: 12.005 -> SPF Calculation started

The Core Question You’re Answering

“How does a network ‘know’ there is a better path, and how fast can it find it?”

Before you write any code, sit with this question. If a fiber optic cable is cut in the Atlantic, how do packets from London to NY reroute through a satellite? It’s not magic; it’s a distributed database synchronization.

Concepts You Must Understand First

Stop and research these before coding:

OSPF Link State Advertisements (LSAs)
- What is the difference between an LSA Type 1 and Type 2?
- How does a router know it has the “latest” version of a map?
- Book Reference: “TCP/IP Illustrated” Ch. 18
GNS3 Cloud/NAT Nodes
- How do you connect a virtual router to your physical computer’s internet?
- Book Reference: “The Book of GNS3” Ch. 4

Questions to Guide Your Design

Before implementing, think through these:

Topology
- If all links have the same cost, which path will OSPF take?
- How do you “break” a link in GNS3 without deleting it?
Monitoring
- What happens to the OSPF ‘Dead Timer’ when you stop a link?
- How can you visualize the shortest path tree (SPF)?

Thinking Exercise

The Cost of a Link

Imagine the triangle:

Link A-B: Cost 10
Link B-C: Cost 10
Link A-C: Cost 100

Scenario: R1 (A) wants to talk to R3 (C).

Path 1: A -> C (Cost 100)
Path 2: A -> B -> C (Cost 10 + 10 = 20)

Questions:

Which path will OSPF take?
If link A-B breaks, what is the new total cost to reach C?
How long does it take for A to realize B is gone?

The Interview Questions They’ll Ask

Prepare to answer these:

“Explain the OSPF neighbor state machine from ‘Down’ to ‘Full’.”
“What is an OSPF ‘Area’ and why do we use Area 0?”
“How does OSPF calculate the cost of a link by default?”
“What is the purpose of a Designated Router (DR) in OSPF?”
“What happens if two routers have the same Router ID?”

Hints in Layers

Hint 1: Setup Start by getting one router to ping another. Don’t add the third until you’ve mastered the first link.

Hint 2: OSPF Config Remember to use the network command under the OSPF process. E.g., network 192.168.1.0 0.0.0.255 area 0.

Hint 3: Wireshark Right-click a link in GNS3 and select “Start Capture”. Look specifically for “Hello” packets (Multicast 224.0.0.5).

Hint 4: Debugging Use show ip ospf neighbor and show ip route on the Cisco CLI to see the internal state.

Books That Will Help

Topic	Book	Chapter
OSPF Internals	“TCP/IP Illustrated, Vol 1” by Stevens	Ch. 18
GNS3 Lab Building	“The Book of GNS3” by Neumann	Ch. 5-6

Project 2: Packet Physics (Discrete Event Mastery)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: C++ (NS-3)
Alternative Programming Languages: Python (via ns3-pybind), C
Coolness Level: Level 3: Genuinely Clever
Business Potential: 1. The “Resume Gold”
Difficulty: Level 2: Intermediate
Knowledge Area: Network Simulation / Performance Analysis
Software or Tool: NS-3, Gnuplot, NetAnim
Main Book: “Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti

What you’ll build: A script in NS-3 that simulates two nodes connected by a point-to-point link. You will vary the bandwidth (Mbps) and propagation delay (ms) and plot the resulting throughput of a TCP Bulk transfer.

Why it teaches Network Simulation: This project moves you from “configuring” to “modeling”. You will see how increasing delay (e.g., a satellite link) kills TCP throughput even if bandwidth is high—this is the “Long Fat Pipe” problem.

Core challenges you’ll face:

Compiling NS-3 with Waf/CMake → maps to handling complex C++ build systems
Creating a PointToPointHelper → maps to defining physical link properties in code
Using FlowMonitor to collect data → maps to instrumenting simulations for analysis

Key Concepts:

Bandwidth-Delay Product (BDP): “TCP/IP Illustrated, Vol 1” Ch. 13
NS-3 Trace Sources: NS-3 Tutorial (nsnam.org)

Difficulty: Intermediate Time estimate: 1 week Prerequisites: C++ basics (objects, pointers), basic understanding of throughput vs. goodput.

Real World Outcome

A set of graphs (using Gnuplot) showing how Throughput drops as Delay increases. You will also have a .pcap file you can open in Wireshark to see exactly how TCP windows behave under delay.

Example Output:

# Running the simulation
$ ./ns3 run scratch/my-tcp-sim --delay=100ms --bandwidth=10Mbps

# Data extracted:
Time: 1.0s, Bytes: 1024000, Throughput: 8.192 Mbps
Time: 2.0s, Bytes: 2048000, Throughput: 8.192 Mbps
...
# Final Report:
Average Throughput: 7.4 Mbps
Packet Loss: 0.02%

The Core Question You’re Answering

“Why is my 1Gbps fiber internet slow when I connect to a server in Australia?”

Before you write any code, sit with this question. Bandwidth is the width of the pipe; Delay is the length. This project proves why “speed” isn’t just about bits-per-second.

Concepts You Must Understand First

Stop and research these before coding:

The TCP Window and BDP
- What is the Bandwidth-Delay Product?
- How does a large BDP affect the TCP Send Window?
- Book Reference: “TCP/IP Illustrated” Ch. 13
NS-3 NodeContainer and DeviceContainer
- How does NS-3 handle the abstraction of a “hardware” device?
- Book Reference: “Advanced Network Simulations Simplified” Ch. 2

Questions to Guide Your Design

Before implementing, think through these:

Simulation Setup
- What is the difference between Seconds(1.0) and MilliSeconds(1000) in the NS-3 scheduler?
- How do you ensure the simulation stops after the data is transferred?
Data Collection
- Should you measure throughput at the sender or the receiver?
- How do you export the results to a CSV file for plotting?

Thinking Exercise

The Satellite Scenario

You have two links:

Fiber: 100 Mbps, 5ms delay.
Satellite: 100 Mbps, 600ms delay.

Questions:

If you send a 1GB file, which link is faster?
If you use UDP, does the delay affect the throughput?
If you use TCP with a 64KB window, what is the maximum possible throughput on the Satellite link? (Hint: Throughput = WindowSize / RTT)

The Interview Questions They’ll Ask

Prepare to answer these:

“What is the ‘Long Fat Pipe’ problem in TCP?”
“Explain how NS-3’s FlowMonitor works internally.”
“How does propagation delay differ from transmission delay?”
“Why would a simulation produce different results than a real-world test?”
“How do you handle random number seeds in NS-3 to ensure reproducibility?”

Hints in Layers

Hint 1: Scaffolding Start with the examples/tutorial/first.cc file. It already creates two nodes and a point-to-point link.

Hint 2: Bandwidth/Delay Look for pointToPoint.SetDeviceAttribute ("DataRate", StringValue ("5Mbps")); and pointToPoint.SetChannelAttribute ("Delay", StringValue ("2ms"));.

Hint 3: Bulk Send Use the BulkSendHelper to saturate the link. It’s designed to send as much data as possible as fast as possible.

Hint 4: Plotting Use std::ofstream to write your results to a .dat file. Then run gnuplot to generate the image.

Books That Will Help

Topic	Book	Chapter
TCP Performance	“TCP/IP Illustrated, Vol 1” by Stevens	Ch. 13-15
NS-3 Practical Coding	“Advanced Network Simulations Simplified”	Ch. 3

Project 3: BGP Multihoming & The Edge (Emulation Mastery)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: BGP (CLI) / GNS3
Alternative Programming Languages: GoBGP, FRRouting
Coolness Level: Level 3: Genuinely Clever
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 3: Advanced
Knowledge Area: Exterior Gateway Protocols / Network Reliability
Software or Tool: GNS3, Cisco IOS/VyOS, Linux VM
Main Book: “The Book of GNS3” by Jason C. Neumann

What you’ll build: A multihomed enterprise edge. Your “Company AS” connects to two different “ISP AS” nodes. You will implement BGP path selection to prefer ISP A for web traffic and ISP B for mail traffic, and verify failover.

Why it teaches Protocol Convergence: BGP is the “glue” of the internet. This project teaches you how large networks negotiate paths and how “Local Preference” and “AS-Path” attributes actually control the world’s traffic.

Core challenges you’ll face:

Setting up eBGP peering between different AS numbers → maps to understanding administrative boundaries
Influencing outbound traffic via Local Preference → maps to controlling egress routing policy
Simulating a full ISP routing table (partial) → maps to handling route scaling in emulation

Key Concepts:

BGP Best Path Selection: RFC 4271
BGP Attributes (MED, LocalPref, AS-Path): “TCP/IP Illustrated, Vol 1” Ch. 18

Difficulty: Advanced Time estimate: 2 weeks

Real World Outcome

You’ll have a fully functional BGP environment where you can trace the path of a packet from your “Internal Network” to the “Internet”. When you “pull the plug” on ISP A, you’ll see BGP withdraw the routes and switch to ISP B in under 60 seconds.

Example Output:

# On Enterprise Router
Enterprise# show ip bgp
     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0/0        10.1.1.1 (ISP_A)               200      0 100 i
 *                    10.2.2.1 (ISP_B)               100      0 200 i

# After shutting Serial 0/0 (ISP_A)
Enterprise# show ip bgp
     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0/0        10.2.2.1 (ISP_B)               100      0 200 i

The Core Question You’re Answering

“How does a company ensure its website stays online even if their internet provider goes bankrupt?”

BGP is the only protocol that handles policy. In this project, you’ll learn that “shortest path” is often less important than “cheapest path” or “most reliable path”.

Concepts You Must Understand First

Stop and research these before coding:

BGP Path Vector Logic
- Why doesn’t BGP use “cost” like OSPF?
- What is the difference between iBGP and eBGP?
- Book Reference: “TCP/IP Illustrated” Ch. 18
Route Maps and Prefix Lists
- How do you tell a router to “only tell ISP A about these networks”?

Questions to Guide Your Design

Inbound Traffic Control
- If you want people to find your website via ISP A, but ISP A is failing, how do you tell the world to use ISP B? (Hint: AS-Path Prepending)
Reliability
- What happens to your BGP session if the physical link stays up but the ISP’s internal network crashes? (Hint: BGP Keepalives vs. BFD)

Thinking Exercise

The Flapping ISP

Imagine ISP A’s link goes up and down every 5 seconds.

How would this affect the global internet?
What mechanism prevents this “flap” from crashing the world’s routers? (Research: Route Dampening)

The Interview Questions They’ll Ask

“Walk me through the BGP best path selection algorithm.”
“What is the ‘Synchronization Rule’ in BGP?”
“How do you prevent a multihomed AS from becoming a Transit AS?”
“What is the purpose of the BGP ‘Weight’ attribute (Cisco specific)?”
“Explain the difference between Hard Reset and Soft Reset in BGP.”

Hints in Layers

Hint 1: Peering Establish eBGP peering first. Verify with show ip bgp summary.

Hint 2: Advertising You must use the network command or redistribute routes for BGP to actually tell the ISPs about your internal IPs.

Hint 3: Policy Use route-map to set local-preference. Apply it in from the neighbor.

Hint 4: Verification Use traceroute from an internal PC to a simulated internet address (e.g., 8.8.8.8) to see the path change.

Books That Will Help

Topic	Book	Chapter
BGP Theory	“TCP/IP Illustrated, Vol 1”	Ch. 18
BGP Configuration	“The Book of GNS3”	Ch. 8

Project 4: The Wi-Fi Collision Lab (802.11 Analysis)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: C++ / NS-3
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 5. The “Industry Disruptor”
Difficulty: Level 3: Advanced
Knowledge Area: Wireless Communications / MAC Protocols
Software or Tool: NS-3, NetAnim, MATLAB (optional for analysis)
Main Book: “Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti

What you’ll build: A simulation of an office environment with 50 Wi-Fi devices trying to use the same Access Point. You will model the CSMA/CA protocol and analyze how “Hidden Terminals” cause massive packet loss.

Why it teaches Packet Analysis: Unlike wired links, wireless is a shared, invisible medium. This project forces you to understand collision avoidance, backoff timers, and why Wi-Fi gets slower as more people join the network.

Project 5: The ISP Core (MPLS L3VPN)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: MPLS/CLI / GNS3
Alternative Programming Languages: SR-MPLS
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 4. The “Open Core” Infrastructure
Difficulty: Level 4: Expert
Knowledge Area: Service Provider Architecture
Software or Tool: GNS3, Cisco IOS-XR or VyOS
Main Book: “The Book of GNS3” by Jason C. Neumann

What you’ll build: A Service Provider core using MPLS (Multi-Protocol Label Switching). You will create a “Virtual Private Network” for a customer with two branches, ensuring their traffic is completely isolated from other customers over the same core.

Why it teaches Tagging & Isolation: This project explains how the modern internet scales. You’ll learn the difference between “Routing” (IP-based) and “Switching” (Label-based) and how VRFs (Virtual Routing and Forwarding) create private “islands” in a public network.

Project 6: TCP Battle (Reno vs. BBR)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: Python (NS-3 Bindings)
Coolness Level: Level 5: Pure Magic
Business Potential: 1. The “Resume Gold”
Difficulty: Level 4: Expert
Knowledge Area: Congestion Control Algorithms
Software or Tool: NS-3, Python (Matplotlib), Wireshark
Main Book: “Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti

What you’ll build: A competitive simulation where two TCP flows (one using standard ‘Reno’ and one using Google’s ‘BBR’) fight for the same 10Mbps link. You will prove why BBR is superior in high-loss environments.

Why it teaches Congestion Control: You will see the “Sawtooth” pattern of TCP Reno and how BBR attempts to “probe” the bandwidth without causing packet loss. This is the cutting edge of network performance engineering.

Project 7: Building “Tiny-Sim” (The First Principles Wizard)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: Python
Alternative Programming Languages: C, Rust
Coolness Level: Level 5: Pure Magic
Business Potential: 1. The “Resume Gold”
Difficulty: Level 5: Master
Knowledge Area: Simulation Engine Design
Software or Tool: Python Standard Library
Main Book: “Simulation Modeling and Analysis” by Averill M. Law

What you’ll build: A from-scratch Discrete Event Simulation engine. You will implement the Event Queue (Priority Queue), the Simulation Clock, and a simple “Node” class that can send and receive timestamped packets.

Why it teaches Simulation Internals: You will realize that NS-3 is just a very complex version of this. Building the scheduler teaches you why “Simulation Time” is independent of “Wall Clock Time” and how causality is maintained in virtual worlds.

Project 8: The Swarm (Mobile Ad-hoc Networks)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: C++ / NS-3
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 5. The “Industry Disruptor”
Difficulty: Level 3: Advanced
Knowledge Area: Wireless Mobility / MANET
Software or Tool: NS-3, NetAnim (for visualization)
Main Book: “Advanced Network Simulations Simplified” by Dr. Anil Kumar Rangisetti

What you’ll build: A simulation of 20 drones (nodes) moving in a “Random Walk” pattern. The drones must maintain a multi-hop mesh network using AODV (Ad-hoc On-demand Distance Vector) routing as they move in and out of range of each other.

Why it teaches Dynamic Routing: In Project 1, your routers were stationary. Here, the topology changes every second. This project teaches you how “Proactive” vs. “Reactive” routing protocols handle chaos.

Project 9: The Fortress (GNS3 Security Lab)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: Firewall CLI (pfSense/ASA)
Alternative Programming Languages: iptables/NFTables
Coolness Level: Level 3: Genuinely Clever
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 2: Intermediate
Knowledge Area: Network Security / Firewalls
Software or Tool: GNS3, pfSense (ISO), Kali Linux
Main Book: “The Book of GNS3” by Jason C. Neumann

What you’ll build: A DMZ (Demilitarized Zone) architecture. You will isolate a public-facing Web Server from an Internal Database using a virtual firewall, and attempt to “hack” the database from the outside to verify your rules.

Why it teaches Traffic Inspection: You’ll learn the difference between “Stateless” and “Stateful” inspection by observing how a firewall allows a response back only if the request was initiated from the inside.

Project 10: Math vs. Machine (Queueing Theory)

File: NETWORK_SIMULATION_MASTERY_NS3_GNS3.md
Main Programming Language: C++ / NS-3
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 1. The “Resume Gold”
Difficulty: Level 3: Advanced
Knowledge Area: Performance Modeling / Queueing Theory
Software or Tool: NS-3, Python (for data verification)
Main Book: “Simulation Modeling and Analysis” by Averill M. Law

What you’ll build: A simulation of a single router interface with a specific buffer size. You will generate traffic with a Poisson distribution and measure the “Average Waiting Time” in the queue, comparing your simulation results to the theoretical M/M/1 queue formula.

Why it teaches Statistical Verification: This is how you prove your simulation is accurate. If your simulation results match the mathematical formula, you’ve mastered the configuration of random variables and event processing.

Project Comparison Table

Project	Difficulty	Time	Depth of Understanding	Fun Factor
1. OSPF Triangle	Level 1	Weekend	Configuration Basics	3/5
2. Packet Physics	Level 2	1 Week	Mathematical Modeling	4/5
3. BGP Multihoming	Level 3	2 Weeks	Policy & Internet Flow	4/5
4. Wi-Fi Collision	Level 3	2 Weeks	Wireless Physics	3/5
5. ISP MPLS Core	Level 4	2 Weeks	Service Provider Logic	5/5
6. TCP Battle	Level 4	1 Month	Protocol Engineering	5/5
7. Tiny-Sim	Level 5	1 Month	CS First Principles	5/5
8. Drone Mesh	Level 3	2 Weeks	Dynamic Mobility	4/5
9. DMZ Fortress	Level 2	Weekend	Practical Security	3/5
10. Math vs. Mach	Level 3	1 Week	Statistical Analysis	2/5

Recommendation

For Networking Professionals: Start with Project 1 (OSPF) and Project 3 (BGP) in GNS3. These provide immediate, high-value skills for real-world router configuration.

For CS Researchers/Developers: Start with Project 2 (NS-3 Basics) and then Project 7 (Tiny-Sim). Understanding the “engine” is more important than knowing specific router commands.

Final Overall Project: The Global ISP Simulation

What you’ll build: A hybrid simulation-emulation monster. You will model a global network consisting of:

A Core Network (MPLS): Emulated in GNS3 with 10+ routers.
Wireless Edge (Wi-Fi/5G): Simulated in NS-3, connected to the GNS3 core via “Tap Bridges”.
Real Applications: Run a real video streaming server (Plex/Jellyfin) on one end and a client on the other.
Chaos Engineering: Introduce link failures and high latency in the core and measure the impact on the video stream’s “Quality of Experience” (QoE).

Why it makes you a Master: This project forces you to integrate every concept. You’ll deal with real OS kernels, mathematical wireless models, and actual application data simultaneously. You will have built a “Digital Twin” of a small ISP.

Summary

This learning path covers Network Simulation and Emulation through 10 hands-on projects. Here’s the complete list:

#	Project Name	Main Language	Difficulty	Time Estimate
1	The OSPF Triangle	Cisco IOS	Beginner	Weekend
2	Packet Physics	C++ (NS-3)	Intermediate	1 Week
3	BGP Multihoming	BGP (CLI)	Advanced	2 Weeks
4	Wi-Fi Collision	C++ (NS-3)	Advanced	2 Weeks
5	ISP MPLS Core	MPLS (CLI)	Expert	2 Weeks
6	TCP Battle	Python (NS-3)	Expert	1 Month
7	Tiny-Sim	Python	Master	1 Month
8	The Swarm (MANET)	C++ (NS-3)	Advanced	2 Weeks
9	The Fortress (DMZ)	Firewall CLI	Intermediate	Weekend
10	Math vs. Machine	C++ (NS-3)	Advanced	1 Week

Recommended Learning Path

For beginners: Start with projects #1, #2, and #9. For intermediate: Jump to projects #3, #4, and #8. For advanced: Focus on projects #5, #6, and #7.

Expected Outcomes

After completing these projects, you will:

Master the difference between Emulation (Real OS) and Simulation (Math Models).
Be able to simulate high-fidelity wireless and wired performance using NS-3.
Design and verify massive routing topologies using GNS3.
Understand the internal mechanics of Discrete Event Simulation engines.
Be able to prove architectural theories with statistical data and packet traces.

You’ll have built 10 working projects that demonstrate deep understanding of Network Simulation from first principles.

Learn Network Simulation: From Zero to Simulation Master

Why Network Simulation Matters

Core Concept Analysis

1. Simulation vs. Emulation: The Fundamental Divide

2. Discrete Event Simulation (DES)

3. The ISO/OSI Mapping in Code

The Simulation Stack: How it Fits Together

Concept Summary Table

Deep Dive Reading by Concept

Simulation Foundations

Protocol & Topology Mastery

Essential Reading Order

Project 1: The OSPF Triangle (Emulation Mastery)

Real World Outcome

The Core Question You’re Answering

Concepts You Must Understand First

Questions to Guide Your Design

Thinking Exercise

The Cost of a Link

The Interview Questions They’ll Ask

Hints in Layers

Books That Will Help

Project 2: Packet Physics (Discrete Event Mastery)

Real World Outcome

The Core Question You’re Answering

Concepts You Must Understand First

Questions to Guide Your Design

Thinking Exercise

The Satellite Scenario

The Interview Questions They’ll Ask

Hints in Layers

Books That Will Help

Project 3: BGP Multihoming & The Edge (Emulation Mastery)

Real World Outcome

The Core Question You’re Answering

Concepts You Must Understand First

Questions to Guide Your Design

Thinking Exercise

The Flapping ISP

The Interview Questions They’ll Ask

Hints in Layers

Books That Will Help

Project 4: The Wi-Fi Collision Lab (802.11 Analysis)

Project 5: The ISP Core (MPLS L3VPN)

Project 6: TCP Battle (Reno vs. BBR)

Project 7: Building “Tiny-Sim” (The First Principles Wizard)

Project 8: The Swarm (Mobile Ad-hoc Networks)

Project 9: The Fortress (GNS3 Security Lab)

Project 10: Math vs. Machine (Queueing Theory)

Project Comparison Table

Recommendation

Final Overall Project: The Global ISP Simulation

Summary

Recommended Learning Path

Expected Outcomes