To simulate an OLSR (Optimized Link State Routing) protocol project using NS2, we will require to follow a sequential steps, which contain writing a TCL script, allowing the OLSR protocol within NS2, and running the simulation. OLSR is a proactive routing protocol created for mobile ad-hoc networks (MANETs), and NS2 supports this protocol out of the box.
The following is a step-by-step instruction on how to simulate OLSR protocol in NS2:
Steps to Simulate OLSR Protocol Projects in NS2
- Install NS2 (Network Simulator 2)
Make sure NS2 is installed on the computer. Unless, we can install it using the below command on Linux:
sudo apt-get install ns2
For Windows, we can utilize Cygwin or download precompiled binaries.
- Create a TCL Simulation Script
Write a TCL script to describe simulation that containing the topology, node movement, traffic patterns, and the OLSR protocol.
Example TCL Script for OLSR Simulation
# Define simulator object
set ns [new Simulator]
# Open trace file for writing
set tracefile [open olsr.tr w]
$ns trace-all $tracefile
# Open NAM file for visualizing the simulation
set namfile [open olsr.nam w]
$ns namtrace-all $namfile
# Define the topology
set topo [new Topography]
$topo load_flatgrid 500 500
# Define the node parameters
set val(nn) 10 ;# Number of nodes
set val(stop) 100.0 ;# Simulation end time
set val(adhocRouting) OLSR ;# Use OLSR routing protocol
set val(x) 500 ;# Topology X dimension
set val(y) 500 ;# Topology Y dimension
# Create the nodes
for {set i 0} {$i < $val(nn)} {incr i} {
set node_($i) [$ns node]
}
# Define the channel, propagation model, MAC type, and antenna
set val(chan) Channel/WirelessChannel ;# Channel type
set val(prop) Propagation/TwoRayGround ;# Radio-propagation model
set val(netif) Phy/WirelessPhy ;# Network interface type
set val(mac) Mac/802_11 ;# MAC type
set val(ifq) Queue/DropTail/PriQueue ;# Interface queue type
set val(ll) LL ;# Link layer type
set val(ant) Antenna/OmniAntenna ;# Antenna model
set val(ifqlen) 50 ;# Max packet in ifq
# Create the network using OLSR
$ns rtproto $val(adhocRouting)
# Set node positions and mobility
for {set i 0} {$i < $val(nn)} {incr i} {
$node_($i) set X_ [expr rand()*$val(x)]
$node_($i) set Y_ [expr rand()*$val(y)]
$node_($i) set Z_ 0.0
$ns at 0.0 “$node_($i) start”
}
# Attach agents (UDP) to nodes
set udp0 [new Agent/UDP]
$ns attach-agent $node_(0) $udp0
set udp1 [new Agent/UDP]
$ns attach-agent $node_(1) $udp1
# Create traffic between nodes
set null0 [new Agent/Null]
$ns attach-agent $node_(2) $null0
set null1 [new Agent/Null]
$ns attach-agent $node_(3) $null1
$ns connect $udp0 $null0
$ns connect $udp1 $null1
# Create a traffic pattern (CBR)
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0
set cbr1 [new Application/Traffic/CBR]
$cbr1 set packetSize_ 512
$cbr1 set interval_ 0.005
$cbr1 attach-agent $udp1
$ns at 1.0 “$cbr0 start”
$ns at 2.0 “$cbr1 start”
# Define the simulation end
$ns at $val(stop) “finish”
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam olsr.nam &
exit 0
}
# Run the simulation
$ns run
- Explanation of the Script
- Simulator Object: The simulator object ($ns) is made to manage the simulation.
- Node Creation: A set of nodes ($node_) are made according to the defined by val(nn).
- Routing Protocol: The OLSR protocol is triggered with $ns rtproto OLSR.
- Traffic Pattern: Traffic is generated among the nodes utilizing UDP agents, and data is transmitted through CBR (Constant Bit Rate) sources.
- Mobility and Topology: Nodes are located randomly in the described topology, and we can insert mobility models to replicate real-world scenarios.
- End Simulation: The simulation runs until the specified time (val(stop)), after which the trace and NAM files are closed and the Network Animator (NAM) is introduced to envision the simulation.
- Run the TCL Script in NS2
We can save TCL script (e.g., olsr_simulation.tcl) and then run it in NS2 using the below command:
ns olsr_simulation.tcl
- Visualize the Simulation
To visualize the simulation, we can utilize NAM (Network Animator):
nam olsr.nam
It will open a graphical interface in which we can monitor the nodes, packet exchanges, and routing activity utilizing OLSR.
- Analyze the Trace File
The trace file (olsr.tr) encompasses detailed records of packet transmission, reception, drops, and other network events. We can process this file using tools such as AWK, Python, or other parsing tools to examine performance parameters such as:
- Throughput: The total amount of data effectively delivered over the network.
- Packet Delivery Ratio: The ratio of packets successfully delivered to the destination.
- End-to-End Delay: The average time it takes for a packet to travel from the origin to the destination.
- Packet Loss: The amount of packets, which were dropped or lost within the network.
- Customize the Simulation
We can extend the simple OLSR simulation by:
- Adjusting Mobility Models: Insert random mobility or other mobility models to replicate node movement.
- Increasing Node Density: Change the amount of nodes and link parameters (e.g., bandwidth, delay) to replicate larger or more complex networks.
- Changing Traffic Types: Replicate TCP traffic or other application layer protocols such as HTTP or FTP.
- Performance Metrics: Compute particular performance parameters like throughput, delay, jitter, and so on.
- Enhance the Project
We can insert distinct scenarios or extensions to this simulation like:
- QoS Support: Execute and calculate Quality of Service (QoS) in OLSR networks.
- Security Extensions: Replicate security mechanisms for OLSR, like avoiding malicious nodes from disrupting the network.
- Performance Comparison: Compare OLSR performance with other MANET routing protocols such as AODV or DSR under distinct conditions (e.g., node mobility, density, traffic load).
From this manual, we comprehensively know the core concepts and replication procedure on how to simulate and enhance the OLSR projects within NS2 simulation environment. We are equipped to offer more insights related to this protocol in upcoming manual.
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