How to implement WAN protocols in ns2

To implement Wide Area Network (WAN) protocols in NS2 has several steps that have to emulate the protocols and scenarios in which the wide-area networks used, which span large geographical areas. WANs is usually includes a various protocols, that has routing protocols such as OSPF, BGP, and MPLS, as well as lower-layer protocols that make sure reliable data transmission over long distances. The given below is the procedure to implement and simulate WAN protocols in NS2:

Step-by-Step Implementation:

Step 1: Define Your WAN Scenario

Before executing particular protocols that need to describe on in which WAN looks like. Consider:

  • Topology: Describe the number of nodes (routers, switches, etc.), how they are associated, and the geographical distribution.
  • Protocols: Adopt that WAN-specific protocols that need to implement like OSPF for internal routing, BGP for inter-AS routing, MPLS for traffic engineering.
  • Traffic: State the kinds of traffic that will traverse the WAN like file transfers, streaming, VoIP.

Step 2: Set Up NS2

Make sure NS2 is installed on the system. If we need to execute the particular protocols not natively supported by NS2 such as MPLS or BGP, we need to expand NS2 with additional modules or write custom code.

Step 3: Create a Basic WAN Simulation Script

Let’s start by generating a simple WAN topology using OSPF that commonly used in WAN scenarios for internal routing within an autonomous system.

Example: Implementing OSPF in a WAN Simulation

  1. Create a New Tcl Script: Open a text editor and generate a new file, for instance, wan_example.tcl.
  2. Set Up the Simulation Environment: Describe the simulator, network topology, and basic parameters.

# Create a simulator object

set ns [new Simulator]

# Define the topology

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)     5                          ;# Number of nodes (routers)

set val(x)      1000                       ;# X dimension of topography

set val(y)      1000                       ;# Y dimension of topography

set val(stop)   20.0                       ;# 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 (routers)

$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 (routers)

for {set i 0} {$i < $val(nn)} {incr i} {

set node_($i) [$ns node]

}

# Define node positions to simulate WAN spread

$node_(0) set X_ 100.0; $node_(0) set Y_ 100.0

$node_(1) set X_ 300.0; $node_(1) set Y_ 100.0

$node_(2) set X_ 500.0; $node_(2) set Y_ 100.0

$node_(3) set X_ 700.0; $node_(3) set Y_ 100.0

$node_(4) set X_ 900.0; $node_(4) set Y_ 100.0

# Setup links between routers to form a WAN topology

$ns duplex-link $node_(0) $node_(1) 1Mb 10ms DropTail

$ns duplex-link $node_(1) $node_(2) 1Mb 20ms DropTail

$ns duplex-link $node_(2) $node_(3) 1Mb 30ms DropTail

$ns duplex-link $node_(3) $node_(4) 1Mb 40ms DropTail

Step 4: Implement WAN Protocol Logic

Implementing OSPF

To execute OSPF, we would usually configure the routing agents on each node. Nevertheless, NS2 does not directly support OSPF. We might essential to emulate the OSPF behaviour using static routing or expand NS2 with a custom OSPF module.

If we are simulating simpler behavior:

# Simulate OSPF-like behavior by configuring static routes

# Example: Node 0 to Node 4 via intermediate nodes

$node_(0) add-route “10.0.0.0/8” $node_(1)

$node_(1) add-route “10.0.0.0/8” $node_(2)

$node_(2) add-route “10.0.0.0/8” $node_(3)

$node_(3) add-route “10.0.0.0/8” $node_(4)

Step 5: Set Up Traffic Sources

Describe the communication among nodes like data transfers across the WAN.

# Setup a TCP agent and attach it to the first node

set tcp [new Agent/TCP]

$ns attach-agent $node_(0) $tcp

# Setup an FTP application to generate traffic

set ftp [new Application/FTP]

$ftp attach-agent $tcp

$ftp start

# Setup a Null agent (sink) on the last node

set null [new Agent/Null]

$ns attach-agent $node_(4) $null

# Connect the agents

$ns connect $tcp $null

Step 6: Define 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 7: Run the Simulation

  1. Save the Tcl script (wan_example.tcl).
  2. Open a terminal and route to the directory in which we saved the Tcl script.
  3. Execute the simulation using the following command:

ns wan_example.tcl

This command will make a trace files and optionally a network animation file (if enabled in script).

Step 8: Analyse the Results

Use trace files and the network animator (NAM) to evaluate the performance of the WAN protocols that concentrates on metrics like packet delivery ratio, end-to-end delay, routing efficiency, and network overhead.

Step 9: Extend to Other WAN Protocols

If we need to mimic other WAN protocols such as BGP or MPLS:

  • BGP: To mimic inter-domain routing by executing BGP-like behaviour among diverse ASes.
  • MPLS: Execute label-based forwarding to enhance routing in large-scale WANs.

Additional Considerations

  • Complexity: WAN protocols can be complex, particularly when dealing with inter-domain routing or traffic engineering.
  • NS3: If NS2 is too limiting for the needs, that deliberately using NS3, that has better support for modern WAN protocols and networking characteristics.
  • Custom Modules: We need to write custom C++ code for more advanced WAN protocols not natively supported by NS2.

In this demonstration, we completely know how to implement the basic setup simulation and to know how to execute the Wide Area Network in ns2 simulator tool. If you have any query regarding this process we also help to clarify it. For the implementation of WAN protocols in NS2, you may contact ns2project.com. Our team specializes in routing protocols including OSPF, BGP, and MPLS, and we are ready to assist you with your projects.