To simulate classless routing protocols within NS2 (Network Simulator 2), we need to encompass setting up a network to support protocols, which utilize Classless Inter-Domain Routing (CIDR) that permitting for more efficient IP address management. General instances of classless routing protocols contain RIP v2, OSPF, and BGP that all support variable-length subnet masking (VLSM).
Even though NS2 does not directly offer built-in implementations of these classless protocols then we can replicate their behaviour by configuring network topologies including custom routing tables, subnets, and inter-router communication to simulate classless routing. Here’s a guide for classless routing protocols that can be simulated using NS2:
Steps to Simulate Classless Protocols in NS2
- Ensure NS2 Installation
If NS2 is not installed then we install it on the Linux system using the below command:
sudo apt-get install ns2
- Understanding Classless Protocols
Classless protocols support CIDR that permits routers to utilize IP addresses without being confined by class-based address boundaries (Class A, B, and C). We can be replicated the behaviour of protocols such as RIP v2, OSPF, or BGP by manually setting up subnets, routing tables, also describing how the routers swap routing data.
- Create a Tcl Simulation Script
Following is an example Tcl script that replicating a basic classless routing environment. This script described a network with routers and subnets utilizing custom routing tables, which support VLSM (variable-length subnet masking).
# Create a new simulator object
set ns [new Simulator]
# Open the trace file
set tracefile [open out.tr w]
$ns trace-all $tracefile
# Define a network topology with classless subnets
set n0 [$ns node] ;# Router 1 (Subnet 192.168.1.0/24)
set n1 [$ns node] ;# Router 2 (Subnet 192.168.2.0/24)
set n2 [$ns node] ;# Router 3 (Subnet 192.168.3.0/28)
set n3 [$ns node] ;# Router 4 (Subnet 192.168.4.0/26)
# Create duplex links between routers
$ns duplex-link $n0 $n1 10Mb 10ms DropTail
$ns duplex-link $n1 $n2 10Mb 20ms DropTail
$ns duplex-link $n2 $n3 10Mb 30ms DropTail
# Assign classless IP addresses (subnet /24, /28, /26)
$n0 set address 192.168.1.1
$n1 set address 192.168.2.1
$n2 set address 192.168.3.1
$n3 set address 192.168.4.1
# Define traffic flow from Router 1 to Router 4
set tcp [new Agent/TCP]
set sink [new Agent/TCPSink]
$ns attach-agent $n0 $tcp
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns at 1.0 “$ftp start”
# Simulation end time
$ns at 10.0 “finish”
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exec nam out.nam &
exit 0
}
# Run the simulation
$ns run
Explanation of the Script
- Subnetting: The IP addresses are split into subnets with diverse subnet masks (/24, /28, /26), which replicating classless routing.
- Router Links: The duplex links among the routers to mimic the connections between distinct subnets.
- Traffic Generation: A TCP connection is established among the nodes on distinct subnets that mimicking traffic between them.
- Run the Tcl Script
We can save the script as classless_routing.tcl. To execute the simulation, utilize the following command:
ns classless_routing.tcl
It will make trace files (out.tr) and a NAM (Network Animator) file (out.nam) that we can utilize to envision the simulation.
- Visualize with NAM
We can be utilized the Network Animator (NAM) to envision how the traffic flows among the subnets. Execute the below command to open the NAM:
nam out.nam
In the NAM window, we will observe the routers, links, and the packets being transmitted among the subnets.
- Simulating Classless Protocol Behavior
Since NS2 does not directly support classless protocols such as RIP v2, OSPF, or BGP, we can simulate their behaviour by:
- Manually configuring subnets: Utilize IP addresses with distinct subnet masks (like /24, /28, /26) to replicate classless addressing.
- Custom routing tables: Describe custom routing tables for each node to mimic how classless routing protocols update routing data.
- Simulating CIDR in Routing Tables
We need to set up each router with a routing table, which supports CIDR by manually describing routes. Here’s how we can mimic CIDR-based routing in NS2:
# Create routing tables for each node to simulate CIDR
# Define routing table for n0 (Router 1)
$n0 add-route 192.168.2.0/24 $n1
$n0 add-route 192.168.3.0/28 $n1
$n0 add-route 192.168.4.0/26 $n1
# Define routing table for n1 (Router 2)
$n1 add-route 192.168.1.0/24 $n0
$n1 add-route 192.168.3.0/28 $n2
$n1 add-route 192.168.4.0/26 $n2
# Define routing table for n2 (Router 3)
$n2 add-route 192.168.1.0/24 $n1
$n2 add-route 192.168.2.0/24 $n1
$n2 add-route 192.168.4.0/26 $n3
# Define routing table for n3 (Router 4)
$n3 add-route 192.168.1.0/24 $n2
$n3 add-route 192.168.2.0/24 $n2
$n3 add-route 192.168.3.0/28 $n2
In this instance, each router has a custom routing table including CIDR routes to other subnets that replicating the behaviour of classless routing protocols.
- Analyzing the Trace File
The out.tr trace file encompasses detailed packet-level data. We can be investigated the trace file to learn parameters like:
- Throughput
- Packet Delivery Ratio (PDR)
- Latency
For instance, to compute the throughput of the network:
awk ‘($1 == “r” && $4 == “tcp”) {sum += $5} END {print “Throughput: ” sum/10.0 ” kbps”}’ out.tr
- Additional Modifications
To simulate classless protocols in detail:
- Varying bandwidth and delays: Change the duplex links to replicate distinct network conditions.
- Traffic generation: Replicate several traffic types (FTP, CBR, and UDP) to monitor how classless routing manages different traffic.
- Router failure: Implement router failure by disabling a node and evaluating how the network responds, same to real-world protocol behaviour (e.g., RIP or OSPF convergence).
We exposed the step-by-step process containing from how to install NS2 to how to analyse the outcomes for Classless Protocol Projects through NS2 simulation tool. We are ready to provide additional specific insights and detailed analysis on this projects, if required.
Check out phdprime.com for insights on classless routing protocols like RIP v2, OSPF, and BGP. We also offer detailed, step-by-step guides to help you recreate Classless Protocol Projects with NS2, customized just for you.
