How to Implement on Classless Protocol in NS2
To implement the classless routing protocols within NS2 (Network Simulator 2) has needs to encompass setup the network simulation to assist the protocols which use Classless Inter-Domain Routing (CIDR). This routing permits for further flexible IP address allocation and routing by using variable-length subnet masks (VLSM). Whereas, NS2 does not have specific built-in support for difficult classless protocols such as OSPF or BGP, then we can simulate the classless routing by setup the IP addresses and subnet masks properly. The following is a method on how we can execute a basic classless routing scenario in NS2:
Step-by-Step Guide to Implement Classless Protocols in NS2
Step 1: Install NS2
Make certain that NS2 is installed on the computer. We can download it from the NS2 webpage and we follow the installation instructions exact to the operating system.
Step 2: Understand Classless Routing
Classless routing, different classful routing, that permits IP addresses to be split into the subnets of changing the sizes which is not limited to the old classes like A, B, C. It is attained using CIDR in which an IP address is accompanied by a subnet mask that implies the number of significant bits in the network portion.
Step 3: Create a Simulation Script
To make a Tcl script to setup the network and mimic classless routing.
Example: Implementing Classless Routing in NS2
- Create a new Tcl script: Here, open a text editor and make a new file, for instance, classless_example.tcl.
- Set up the simulation environment: Describe the simulator, set up the network topology, and configure the metrics particular to the simulation.
# Create a simulator object
set ns [new Simulator]
# Define options for the simulation
set val(chan) Channel/WirelessChannel ;# Channel type
set val(prop) Propagation/TwoRayGround ;# 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 type
set val(ifqlen) 50 ;# Max packet in ifq
set val(nn) 4 ;# Number of nodes
set val(x) 500 ;# X dimension of topography
set val(y) 500 ;# Y dimension of topography
set val(stop) 10.0 ;# Simulation time
# Initialize the topology object
set topo [new Topography]
$topo load_flatgrid $val(x) $val(y)
# Create the God object
create-god $val(nn)
# Configure the nodes
$ns node-config -llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON \
-macTrace ON \
-movementTrace ON
# Create nodes
for {set i 0} {$i < $val(nn)} {incr i} {
set node_($i) [$ns node]
$node_($i) random-motion 0
}
# Manually assign IP addresses with subnet masks
$node_(0) set-address “192.168.1.1/24”
$node_(1) set-address “192.168.1.2/24”
$node_(2) set-address “192.168.2.1/24”
$node_(3) set-address “192.168.2.2/24”
- Setup Routing:
As we are dealing with a classless network, we can manually configure the routes if required:
# Add static routes if necessary (optional)
$node_(0) add-route “192.168.2.0/24” $node_(2)
$node_(1) add-route “192.168.2.0/24” $node_(3)
- Setup traffic sources:
# Setup a TCP agent and attach it to node 0
set tcp [new Agent/TCP]
$ns attach-agent $node_(0) $tcp
# Setup a TCP Sink agent and attach it to node 3
set sink [new Agent/TCPSink]
$ns attach-agent $node_(3) $sink
# Connect the agents
$ns connect $tcp $sink
# Setup an FTP application over the TCP agent
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp start
- Setup simulation end:
# Define simulation end time
$ns at $val(stop) “stop”
$ns at $val(stop) “$ns nam-end-wireless $val(stop)”
$ns at $val(stop) “exit 0”
proc stop {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
}
# Run the simulation
$ns run
Step 4: Run the Simulation
- We save the Tcl script such as classless_example.tcl.
- Open a terminal and navigate to the directory in which we can saved the Tcl script.
- Run the simulation using the below command:
ns classless_example.tcl
The above command will make trace files and optionally a network animation file if permitted in the script.
Step 5: Analyse the Results
We can use the trace files and network animator (NAM) to evaluate the performance of the classless routing scenario, concentrating on parameters like packet delivery ratio, delay, and network overhead.
Step 6: Visualize the Results (Optional)
If we have allowed the network animator (NAM) in the script, then we can visualize the simulation:
nam classless_example.nam
It will open the NAM window in which we observe the network topology and the performance of the classless routing scenario during the simulation.
Additional Considerations
- CIDR Blocks: Make certain that know how CIDR blocks work to appropriately allocate IP addresses and the subnet masks.
- Routing Protocols: For more difficult routing scenarios, we want to execute or mimic a routing protocol which supports CIDR, like OSPF or BGP, however it would need significant customization in the NS2.
- Static Routing: In the nonappearance of furthered routing protocols, we can use the static routing to replicate a classless routing environment.
Extending the Implementation
If we want to mimic more furthered classless routing protocols such as OSPF or BGP, we may require to expand the simulator NS2 by writing custom C++ modules or using an external simulator which better supports these protocols, like NS3 or a dedicated the simulator BGP/OSPF.
In this module, we understood the execution process, sample snippets were given to enforce the Classless protocol with the help of ns2. We also provide further significant details about this protocol.
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