How to Implement Logical Topology in ns2

To implement the Logical Topology within a network simulator NS2 which means to the arrangement of the devices and how they communicate with each other regardless of the physical layout of the network. It is typically described according to how data flows over the network, also it can vary considerably from the physical topology. For specimen, the physical topology may be a bus, star, or ring. However, the logical topology can be a point-to-point, transmission, or a peer-to-peer network. In the NS2 (Network Simulator 2) that executing a logical topology encompasses describing the logical connections among the nodes on top of an existing physical topology. Get project ideas from ns2project.com we guide you in completing your research. The nodes communicate based on the logical links that may not correspond directly to the physical links. We provide the simple approach to perform this topology in NS2:

Steps to Implement Logical Topology in NS2:

  1. Set Up the Physical Topology:
  • To make a physical nodes and physical links among them, representative the underlying physical structure.
  1. Define the Logical Topology:
    • Generate a logical links among the logical nodes that can be mapped to physical nodes. The logical links signify the virtual communication paths among the nodes which do not essentially reflect the underlying physical connections.
  2. Simulate Traffic Flow:
    • Create the traffic among logical nodes that may be routed via several physical nodes according to the logical topology.

Example of Logical Topology Implementation in NS2:

The following is an instance of how to configure a logical topology on top of a physical network in the simulation tool NS2. In this situation, the physical network contains of the 6 nodes, and the logical topology attaches a subset of those nodes directly, while they may be manually associated via the intermediate nodes.

# Create a new simulator

set ns [new Simulator]

# Open trace file for output

set tracefile [open out.tr w]

$ns trace-all $tracefile

# ======= PHYSICAL TOPOLOGY =======

# Define physical nodes

set p0 [$ns node]  ;# Physical node 0

set p1 [$ns node]  ;# Physical node 1

set p2 [$ns node]  ;# Physical node 2

set p3 [$ns node]  ;# Physical node 3

set p4 [$ns node]  ;# Physical node 4

set p5 [$ns node]  ;# Physical node 5

# Create duplex links for the physical network

$ns duplex-link $p0 $p1 1Mb 10ms DropTail  ;# Link between p0 and p1

$ns duplex-link $p1 $p2 1Mb 10ms DropTail  ;# Link between p1 and p2

$ns duplex-link $p2 $p3 1Mb 10ms DropTail  ;# Link between p2 and p3

$ns duplex-link $p3 $p4 1Mb 10ms DropTail  ;# Link between p3 and p4

$ns duplex-link $p4 $p5 1Mb 10ms DropTail  ;# Link between p4 and p5

$ns duplex-link $p0 $p5 1Mb 10ms DropTail  ;# Link between p0 and p5

# ======= LOGICAL TOPOLOGY =======

# Define logical nodes

set l0 [$ns node]  ;# Logical node 0 (maps to physical node 0)

set l1 [$ns node]  ;# Logical node 1 (maps to physical node 1)

set l2 [$ns node]  ;# Logical node 2 (maps to physical node 4)

set l3 [$ns node]  ;# Logical node 3 (maps to physical node 5)

# ======= MAP LOGICAL NODES TO PHYSICAL NODES =======

# Logical node 0 is mapped to physical node 0

$l0 set X_ [$p0 set X_]

$l0 set Y_ [$p0 set Y_]

# Logical node 1 is mapped to physical node 1

$l1 set X_ [$p1 set X_]

$l1 set Y_ [$p1 set Y_]

# Logical node 2 is mapped to physical node 4

$l2 set X_ [$p4 set X_]

$l2 set Y_ [$p4 set Y_]

# Logical node 3 is mapped to physical node 5

$l3 set X_ [$p5 set X_]

$l3 set Y_ [$p5 set Y_]

# ======= CREATE LOGICAL LINKS =======

# These are logical links representing virtual connections between the logical nodes

$ns duplex-link $l0 $l1 1Mb 10ms DropTail  ;# Logical link between l0 and l1

$ns duplex-link $l1 $l2 1Mb 10ms DropTail  ;# Logical link between l1 and l2

$ns duplex-link $l2 $l3 1Mb 10ms DropTail  ;# Logical link between l2 and l3

# ======= TRAFFIC SIMULATION =======

# Define TCP agents for communication between logical nodes

# Traffic from logical node l0 to logical node l3

set tcp0 [new Agent/TCP]

set sink0 [new Agent/TCPSink]

$ns attach-agent $l0 $tcp0

$ns attach-agent $l3 $sink0

$ns connect $tcp0 $sink0

# Simulate FTP traffic from l0 to l3

set ftp0 [new Application/FTP]

$ftp0 attach-agent $tcp0

$ns at 1.0 “$ftp0 start”   ;# Start traffic at 1 second

# End the simulation after 10 seconds

$ns at 10.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

Explanation of the Script:

  1. Physical Topology:
    • The physical nodes are p0, p1, p2, p3, p4, and p5 that form the underlying physical network.
    • Duplex links are made among the physical nodes that forming the physical connections that data may traverse in the network.
  2. Logical Nodes:
    • The logical nodes are l0, l1, l2, and l3 are logical that built the logical topology. This logical nodes are mapped to physical nodes, however they might communicate through the logical links which are independent of the physical layout.
  3. Mapping Logical Nodes to Physical Nodes:
    • Logical nodes are mapped to particular physical nodes by connecting their coordinates like X_ and Y_ including those of the physical nodes.
  4. Logical Links:
    • Duplex links among the logical nodes form a logical topology that demonstrating virtual connections among the logical nodes such as l0 to l1, l1 to l2, and so on.
  5. Traffic Simulation:
    • TCP agents are replicate the communication among logical nodes.
    • FTP (File Transfer Protocol) makes a traffic that mimicking file transfers among the logical nodes. For instance, traffic flows from l0 to l3 via the logical links.
  6. Simulation Duration:
    • For 10 seconds, the simulation runs which permitting the traffic to flow over the logical topology.

Post-Simulation Analysis:

  1. Trace File Analysis:
    • Now, open the trace file (out.tr) to monitor how packets are sent among the logical nodes. We can estimate the flow of data via the physical network based on the logical topology.
  2. NAM Visualization:
    • We can use the NAM (Network Animator) to envision both the physical and logical topologies. The logical nodes and links will be showed that are presenting how traffic flows logically even if it navigates the physical nodes.
  3. Performance Metrics:
    • Calculate the network performance metrics like delay, throughput, and packet loss to estimate how successfully the logical topology acts across the physical network.

Enhancing the Simulation:

  1. Adding More Logical Nodes:
    • Append more logical nodes are mapped to other physical nodes that forming a more difficult logical topology across the physical infrastructure.
  2. Simulating Different Traffic Patterns:
    • Configure extra traffic flows among various logical nodes to replicate more difficult communication patterns.
  3. Simulating Link Failures:
    • To replicate the failures in the physical or logical links to monitor how the network adjust to varies and also how logical paths may be rerouted via various physical nodes.
  4. Varying Link Parameters:
    • Examine with various link parameters like bandwidth, latency, and queue type such as DropTail or RED to learn how network performance alters under various conditions.
  5. Simulating Mobility:
    • We can be replicated the mobility for logical nodes by actively modifying their mapping to various physical nodes across the time.

Through this set up, we offered stepwise approach regarding the Logical Topology which is executed in ns2 environment. We also deliver the analysing steps, physical node setups of it that help you understand the process. We will provide more details relevant to this topology, if you required.