To simulate a Ring Topology using NS2, we can follow these steps:
Steps to Simulate Ring Topology Projects in NS2
- Set up NS2 Environment:
Make sure that NS2 is installed and functioning appropriately on the computer. We will write a TCL script to describe the Ring Topology and replicate traffic patterns.
- Understanding Ring Topology:
- In a Ring Topology, each node is associated to exactly two other nodes that forming a unique continuous path for signals via each node. Data passes through each node until it attains its destination.
- We can mimic it within NS2 by making a set of nodes and linking them in a circular (ring) fashion.
- Create a TCL Script for Ring Topology:
Below is a simple instance of how to make a Ring Topology in NS2:
# Create a new simulator instance
set ns [new Simulator]
# Open a NAM file for visualization
set nf [open out.nam w]
$ns namtrace-all $nf
# Create nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
# Create links to form a ring topology
$ns duplex-link $n0 $n1 10Mb 10ms DropTail
$ns duplex-link $n1 $n2 10Mb 10ms DropTail
$ns duplex-link $n2 $n3 10Mb 10ms DropTail
$ns duplex-link $n3 $n4 10Mb 10ms DropTail
$ns duplex-link $n4 $n0 10Mb 10ms DropTail
# Define traffic sources and destinations
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
set udp1 [new Agent/UDP]
$ns attach-agent $n1 $udp1
set udp2 [new Agent/UDP]
$ns attach-agent $n2 $udp2
# Null agents to receive data
set null0 [new Agent/Null]
$ns attach-agent $n3 $null0
set null1 [new Agent/Null]
$ns attach-agent $n4 $null1
set null2 [new Agent/Null]
$ns attach-agent $n0 $null2
# Connect agents to simulate traffic across the ring
$ns connect $udp0 $null0
$ns connect $udp1 $null1
$ns connect $udp2 $null2
# Define traffic patterns using CBR (Constant Bit Rate) sources
set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0
$cbr0 set packetSize_ 512
$cbr0 set rate_ 100Kb
set cbr1 [new Application/Traffic/CBR]
$cbr1 attach-agent $udp1
$cbr1 set packetSize_ 512
$cbr1 set rate_ 100Kb
set cbr2 [new Application/Traffic/CBR]
$cbr2 attach-agent $udp2
$cbr2 set packetSize_ 512
$cbr2 set rate_ 100Kb
# Schedule traffic
$ns at 1.0 “$cbr0 start”
$ns at 1.5 “$cbr1 start”
$ns at 2.0 “$cbr2 start”
# Stop traffic
$ns at 5.0 “$cbr0 stop”
$ns at 5.5 “$cbr1 stop”
$ns at 6.0 “$cbr2 stop”
# Finish simulation
$ns at 7.0 “finish”
proc finish {} {
global ns nf
$ns flush-trace
close $nf
exec nam out.nam &
exit 0
}
# Run the simulation
$ns run
- Explanation of the Code:
- Nodes: Five nodes (n0, n1, n2, n3, n4) are made that denoting the devices in the ring topology.
- Links: Each node is associated to two other nodes within a circular fashion, which forming a ring. For instance, node n0 is related to both n1 and n4, and node n4 is connected back to n0.
- UDP Traffic: Each node makes UDP traffic utilizing a CBR (Constant Bit Rate) application and the traffic flows among the nodes.
- Traffic Timing: Traffic from diverse nodes begins at slightly distinct times (1.0s, 1.5s, and 2.0s) and ends among 5.0s and 6.0s.
- NAM Trace: The simulation outcomes are saved in a out.nam file that can be viewed in the NAM (Network Animator) tool.
- Run the Simulation:
- We need to save the above TCL script to a file, for example, ring_topology.tcl.
- We can open a terminal and traverse to the folder in which the script is saved.
- We execute the simulation by running the following command:
ns ring_topology.tcl
- It will make a NAM file (out.nam) that can be opened to envision the ring topology using NAM.
- Enhancements and Customization:
- More Nodes: We can insert more nodes to the ring by simply making more nodes and links.
- Change Traffic Patterns: We can modify traffic metrics, like packet size, data rate, or traffic type (e.g., use TCP instead of UDP).
- Failure Scenarios: We can replicate the failure of a node or link in the ring and monitor how the data flow change.
In the above procedure, we have exhibited the simplified steps for Ring Topology projects, simulated with the help of NS2 simulation environment with instances. If you have any doubts regarding this, we will help you out.
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