📶 DiffServ QoS Evaluation in ns-3

Overview

This directory contains a simple PFIFO + DiffServ (Differentiated Services) network scenario to evaluate the QoS performance of three traffic classes:

• EF (Expedited Forwarding) – VoIP
• AF41 (Assured Forwarding) – Video Streaming
• BE (Best Effort) – FTP/File Transfer

The goal is to analyze how PFIFO queue sizes affect performance metrics like delay, jitter, throughput, and packet loss under different priority classes.

Network topology

[Client EF]   [Client AF]   [Client BE]
     |             |              |
     +-------------+--------------+
                   |
             [Edge Router]
                   |
           (bottleneck link)
                   |
             [Core Router]
             /     |     \
   [Server EF] [Server AF] [Server BE]

Usage

Run the simulation with custom queue sizes (optional):

./ns3 run "network_topology --ef=100 --af=400 --be=500"

Alternatively run with default queue length values:

./ns3 run network_topology

Results

This section shows how DiffServ traffic classes behave as network load increases. The x-axis indicates the number of packets generated for each traffic class.

Throughput

Average delay

Packet loss