Network Traffic Simulator (Discrete Event Simulator)

Course: CS 2336 - Computer Science II
Semester: Spring 2024
Project: Network Simulation - Host Pinging
Language: Java

Overview

This project implements a discrete-event network simulator that models single-hop network traffic in a star topology. Hosts communicate by sending ping requests and ping responses, and the simulator computes round-trip time (RTT) for each ping using a Future Event List (FEL). The simulation is event-driven and processes events strictly in time order, closely resembling how real-world network simulators operate.

Key Features

Discrete Event Simulation

• Uses a custom FutureEventList implemented as a doubly-linked list
• Events are processed in increasing simulation time order

Network Messaging

• Supports ping requests and ping responses
• Calculates and reports RTT for each completed ping

Star Topology

• One central host connected to multiple neighboring hosts
• Communication is always between neighbors

Extensible Design

• Built using abstract classes and interfaces
• Designed to mirror real-world simulation frameworks

Project Components

Class	Description
LinkedEventList	Doubly Linked List implementation of the FutureEventList interface
EventNode	Node class for the linked list
Message	Represents a network message (ping request or response)
SimpleHost	Concrete implementation of a network host
EventException	Custom unchecked exception for event-related errors
Main	Entry point that loads input and runs the simulation

Network Model

• Topology: Star
• Message Delay: 1 unit of distance = 1 unit of simulation time
• RTT Calculation: RTT = time received - time sent
• Assumptions:
  • Host only pings one destination
  • Ping interval is always greater than RTT
  • Input file is complete and valid
  • Event processing order is time based

How the Simulation Works

• Read input file
• Create hosts and neighbor relationships
• Bootstrap ping events
• Run simulation loop
  • Pop next event from the FutureEventList
  • Call handle() on the event
  • Continue until no events remain

Sample Input

5
6 2
7 3
-1
5 7 10 28

• First number is the central host address
• Following lines are of the format: <neighbor address> <distance>
• -1 terminates list of neighbors
• Following lines are of the format: <source> <destination> <interval> <duration>

Sample Output

[10ts] Host 5: Sent ping to host 7
[13ts] Host 7: Ping request from host 5
[16ts] Host 5: Ping response from host 7 (RTT = 6ts)
[20ts] Host 5: Sent ping to host 7
[23ts] Host 7: Ping request from host 5
[26ts] Host 5: Ping response from host 7 (RTT = 6ts)
[28ts] Host 5: Stopped sending pings

• ts= simulation time units
• Output ordering may differ when multiple events occur at the same time

How to Run

• Place simulation.txt in the project root directory.
• Compile: javac *.java
• Run: java Main

Possible Extensions

• Multi-hop routing
• Packet loss and retransmissions
• Visualization of network traffic
• Support for additional message types