To simulate a Tree Topology in NS2, we can make a hierarchical network in which each node is associated to a central or root node, and nodes are systematized in a parent-child relationship same to a tree structure.
Here is a detailed guide to simulate Tree Topology projects in NS2.
Steps to Simulate Tree Topology Projects in NS2
- Set up NS2 Environment:
Make certain that NS2 is properly installed and set up on the system. The simulation will be written utilizing a TCL script to describe the tree topology, node connections, and traffic patterns.
- Understanding Tree Topology:
- In a Tree Topology, nodes are organized hierarchically. There is a central root node, which associates to intermediate nodes, and the intermediate nodes are connect to leaf nodes.
- This topology is generally utilized for structured networks in which data flows from the child nodes to parent nodes or vice versa.
- Create a TCL Script for Tree Topology:
Following is an instance of a simple Tree Topology simulation 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 $nf
# Create nodes for the tree structure
set root [$ns node] ;# Root node (level 0)
set n1 [$ns node] ;# Level 1
set n2 [$ns node] ;# Level 1
set n3 [$ns node] ;# Level 2
set n4 [$ns node] ;# Level 2
set n5 [$ns node] ;# Level 2
set n6 [$ns node] ;# Level 2
# Create duplex links to form the tree topology
$ns duplex-link $root $n1 10Mb 10ms DropTail
$ns duplex-link $root $n2 10Mb 10ms DropTail
$ns duplex-link $n1 $n3 10Mb 10ms DropTail
$ns duplex-link $n1 $n4 10Mb 10ms DropTail
$ns duplex-link $n2 $n5 10Mb 10ms DropTail
$ns duplex-link $n2 $n6 10Mb 10ms DropTail
# Set up UDP agents to generate traffic
set udp0 [new Agent/UDP]
$ns attach-agent $n3 $udp0
set udp1 [new Agent/UDP]
$ns attach-agent $n5 $udp1
# Set up Null agents to receive traffic at the root node
set null0 [new Agent/Null]
$ns attach-agent $root $null0
set null1 [new Agent/Null]
$ns attach-agent $root $null1
# Connect traffic sources to the root node (UDP to Null)
$ns connect $udp0 $null0
$ns connect $udp1 $null1
# Create CBR (Constant Bit Rate) traffic for each UDP agent
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
# Schedule the traffic to start and stop
$ns at 1.0 “$cbr0 start”
$ns at 1.5 “$cbr1 start”
$ns at 5.0 “$cbr0 stop”
$ns at 5.5 “$cbr1 stop”
# End the simulation after a specific time
$ns at 6.0 “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: The script makes 7 nodes that are 1 root node, 2 level-1 intermediate nodes, and 4 level-2 leaf nodes. The structure forms a tree including the root node at the top, two intermediate nodes, and four leaf nodes.
- Links: Duplex links relate the nodes to form the tree topology. For example, the root node associates to n1 and n2, and those intermediate nodes are connecting to their corresponding leaf nodes.
- Traffic Setup: UDP agents are connected to the nodes n3 and n5 (leaf nodes). Traffic is transmitted from these leaf nodes to the root node utilizing CBR (Constant Bit Rate) traffic. Null agents at the root node that receive the data.
- Timing: The traffic begins at 1.0 seconds and 1.5 seconds, and ends at 5.0 and 5.5 seconds, correspondingly. The simulation stops at 6 seconds.
- Run the Simulation:
- We need to save the script as tree_topology.tcl.
- We can open a terminal and traverse to the folder containing the script.
- Run the simulation using the below command:
ns tree_topology.tcl
- The simulation will make a .nam file (out.nam), which can be opened in Network Animator (NAM) for visualization.
- Visualization in NAM:
- After the simulation runs, the Network Animator (NAM) tool will indicate the tree structure. We should observe the hierarchical arrangement of nodes, including data being transmitted from the leaf nodes to the root.
- Customization:
- Add More Levels: We can insert more nodes and make extra levels with the tree. For instance, if we require a 3-level tree then we would insert a level of nodes and link them to the second level.
- Use TCP: Rather than using UDP agents, we can be used TCP agents for reliable traffic simulation.
- Vary Traffic: We can test with distinct traffic parameters (packet size, data rate) or utilize diverse traffic types (TCP, FTP, etc.).
- Advanced Tree Topology Simulation:
If we require replicating more complex scenarios (like failures, QoS, etc.) then we can insert more advanced aspects like:
- Link Failures: Replicate failures by disabling links or nodes to observe how the tree manages faults.
- Quality of Service (QoS): Insert QoS metrics by executing distinct traffic types or priority-based queuing mechanisms.
We shown in this process, it will support you to know tree topology concepts and simulation approach on how to simulate and analyse the Tree Topology projects using NS2 platform. If needed more insights, we can help you with another approach.
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