NetFlow — Network Packet Simulator

NetFlow is a high-performance, console-based Java application that simulates real-time data packet routing across a network of virtual routers. Built entirely from scratch without external libraries or Java's built-in collections framework, this project demonstrates the practical application of core Data Structures and Algorithms (DSA) in solving fundamental networking challenges like buffer management, packet encapsulation, routing efficiency, and path tracking.

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🚀 Key Features

• Custom Data Structures: Implements all 5 foundational data structures completely from scratch.
• Autonomous Packet Generation: Simulates realistic network traffic via a background Java Thread.
• Smart Rerouting: Employs recursive backtracking to dynamically reroute packets when primary router buffers are full.
• Bidirectional Event Logging: Captures all simulation activities in a custom Doubly Linked List for chronological or reverse inspection.
• Performance Benchmarking: Includes a terminal report measuring $O(1)$ HashMap routing tables against $O(n)$ linear searches using System.nanoTime().
• CSV Reporting: Automatically exports detailed packet-level performance logs to a simulation_log.csv file upon completion.

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🛠️ Data Structures Architecture

Data Structure	Implementation Class	Role in NetFlow Simulation
Queue	RouterQueue.java	Acts as the router buffer. Implemented via a circular array with index wrapping (%) to manage packet waiting lines (Max capacity: 5).
Stack	HeaderStack.java	Models OSI layer packet encapsulation. Router IDs are pushed (++top) during transit and popped (top--) in LIFO order upon delivery.
HashMap	Network.java	Functions as the routing table for instant $O(1)$ next-hop lookups mapped to destination keys.
Singly Linked List	PacketPath.java	Bound to individual packets to record their dynamic traversal path node-by-node (Router-A -> Router-B).
Doubly Linked List	EventLog.java	Maintains the global simulation diary. Supports bidirectional traversal (next/prev) to view logs forward or backward.

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🧠 Algorithms Implemented

1. Recursive Routing (sendPacket)

Moves data packets hop-by-hop toward their destinations. Each recursive call represents a single network hop. It includes a depth guard ($depth > 10$) to handle base cases safely and avoid infinite routing loops.

2. Backtracking (Alternate Path Selection)

Triggered instantly when a preferred router's buffer (RouterQueue) is full. The algorithm tracks visited routers and backtracks through a looping mechanism to locate an available alternative path rather than dropping the packet prematurely.

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💻 How to Setup and Run

Prerequisites

• Java JDK 11 or above (JDK 23 recommended)
• IntelliJ IDEA (Community or Ultimate Edition)

Step-by-Step Installation

1. Clone this repository to your local machine:

   git clone [https://github.com/mohsin1782005/Netflow.git)