Computer Networks

NS

Features

Event driven simulator– developed at UC Berkeley

Network Topologies– nodes (connectivity), links (bandwidth, delay)

Transport Protocols– UDP, TCP (flavors)

Applications– Web, FTP, CBR ...

Router Queue Management– Drop-Tail, RED, CBQ ...

Overview

Write TCL scripts Run, get NS tracefile and NAM tracefile Visualize NAM tracefile Analyze NS tracefile

Running

On shiraz.wpi.edu (Linux box)– need passwords

In: /usr/local/ns-allinone-2.1b5/bin– add to path

Running:– ns dooda.tcl

Output:– dooda.nam and dooda.tr

Visualization

nam dooda.nam Right-click to get

loss and utilization

Analysis

Scripts/Programs in Perl, C, Shell– see stats.pl

Experiments

Fairness and congestion TCP vs. TCP Robust TCP vs. Fragile

TCP TCP vs. UDP Drop-Tail vs. RED (FRED vs. RED)