How to Implement Network Service Discovery in NS2

To implement Network Service Discovery in NS2 has needs to model a system in which nodes in a network can enthusiastically determine available services without previous knowledge of where those services are located. This can be helpful in dynamic networks like an ad-hoc or mobile networks, in which nodes need to identify available resources, like printers, file servers, or media streams.

Here’s a step-by-step procedure to implement Network Service Discovery in NS2:

Step-by-Step Guide to Implement Network Service Discovery in NS2

  1. Set Up the Basic Network Topology:
  • Initiate by configuring a simple network topology with multiple nodes that will offer and discover services. The topology can denote a wired or wireless network relaying on scenario.

Example OTcl script to set up the basic network topology:

set ns [new Simulator]

set nf [open out.tr w]

$ns trace-all $nf

set namfile [open out.nam w]

$ns namtrace-all $namfile

# Create nodes (Node0 will act as a service provider)

set node0 [$ns node]   ;# Service provider node

set node1 [$ns node]   ;# Service requester node 1

set node2 [$ns node]   ;# Service requester node 2

# Create duplex links between nodes (wired topology)

$ns duplex-link $node0 $node1 1Mb 10ms DropTail

$ns duplex-link $node0 $node2 1Mb 10ms DropTail

# Run the simulation

$ns at 6.0 “finish”

proc finish {} {

global ns nf namfile

$ns flush-trace

close $nf

close $namfile

exec nam out.nam &

exit 0

}

$ns run

  • This describes a simple three-node network in which node0 will offer a service, and node1 and node2 will attempt to discover this service.
  1. Define Services and Announce Their Availability:
  • Describe the services delivered by particular nodes such as node0 and broadcast this information via the network. The simplest approaches for service discovery are to utilize a broadcast or multicast mechanism, in which a node intermittently announces the services it offers.

Example OTcl script for service announcement:

# Define a service at node0 (e.g., “File Server”)

set service_type “FileServer”

set service_port 8080

# Broadcast the service announcement

proc announce_service {node service_type service_port} {

puts “Node $node is announcing service $service_type on port $service_port”

# Here you would use a broadcast or multicast packet (not shown for simplicity)

}

# Schedule periodic service announcements from node0

$ns at 1.0 “announce_service $node0 $service_type $service_port”

$ns at 2.0 “announce_service $node0 $service_type $service_port”

  • This script mimics a basic service announcement in which node0 broadcasts the availability of a file server on port 8080.
  1. Implement Service Discovery at Requester Nodes:
  • The requester nodes such as node1 and node2 listen for service announcements and decide either to connect to the service according to their needs. A service discovery protocol like Service Location Protocol (SLP) or a custom broadcast-based protocol can be utilized.

Example OTcl script to discover services:

# Node1 listens for service announcements

proc discover_service {node service_type service_port} {

global service_type_discovered

set service_type_discovered $service_type

if { $service_type == “FileServer” } {

puts “Node $node discovered service $service_type on port $service_port”

request_service $node $service_port

}

}

# Node1 requests the service after discovery

proc request_service {node service_port} {

puts “Node $node requesting service on port $service_port”

# Simulate service request and response (details would depend on the service type)

}

# Set up service discovery at node1 and node2

$ns at 1.5 “discover_service $node1 $service_type $service_port”

$ns at 2.5 “discover_service $node2 $service_type $service_port”

  • This script enable the node1 and node2 to discover and request the service when they receive an announcement. If node1 hears about a “FileServer,” it requests the service on port 8080.
  1. Simulate Service Requests and Responses:
  • After discovering the service, the requester node can transfer a request for the service, and the deliver node can respond consequently. In the case of a file server, this could mean requesting file data over a connection.

Example OTcl script for handling service requests and responses:

# Node0 (the service provider) responds to service requests

proc respond_to_service_request {node request_port} {

puts “Node $node responding to service request on port $request_port”

# Simulate data transfer or interaction with the service (e.g., file download)

}

# Simulate service request from node1 to node0

$ns at 3.0 “respond_to_service_request $node0 $service_port”

  • This script mimics a response from node0 (the service provider) to a request from node1 (the requester).
  1. Implement Multicast or Broadcast for Service Discovery (Optional):
  • In larger or more dynamic networks, service announcements are usually completed using multicast or broadcast messages to effectively acquaint multiple nodes of the available services.

Example OTcl script for multicast-based service discovery:

# Enable multicast support

$ns multicast

# Set up multicast group for service announcements

set mcast_group 224.0.0.1   ;# Multicast group IP address

$node0 join-group $mcast_group

$node1 join-group $mcast_group

$node2 join-group $mcast_group

# Node0 sends multicast service announcements

proc multicast_service_announcement {node group service_type service_port} {

puts “Node $node sending multicast service announcement for $service_type”

# Simulate sending multicast message to group (details depend on service)

}

# Set up periodic multicast service announcements from node0

$ns at 1.0 “multicast_service_announcement $node0 $mcast_group $service_type $service_port”

$ns at 2.0 “multicast_service_announcement $node0 $mcast_group $service_type $service_port”

  • This script configures multicast-based service announcements in which all nodes in the multicast group receive service advertisements from node0.
  1. Monitor and Log Service Discovery:
  • We can log service discovery events, that has which nodes discover that services and when. This supports in evaluating on how well the service discovery mechanism acts as in the network.

Example OTcl script to log service discovery:

# Log the service discovery event

proc log_service_discovery {node service_type service_port time} {

puts “At $time: Node $node discovered service $service_type on port $service_port”

}

# Call log_service_discovery when a service is discovered

$ns at 1.5 “log_service_discovery $node1 $service_type $service_port 1.5”

$ns at 2.5 “log_service_discovery $node2 $service_type $service_port 2.5”

  • These logs the time when a node discovers a service and that service was discovered.
  1. Run the Simulation and Analyse Results:
  • Execution the simulation to see how the nodes announce discovers, and request services in the network.

To run the simulation:

ns your_script.tcl

  • The trace file (out.tr) will includes events that relevant to service discovery, announcements, and requests. We can evaluate this file to see how services were discovered and used.
  1. Visualize Service Discovery in NAM:
  • Use NAM (Network Animator) to envision how the nodes interact and discover services in the network.

nam out.nam

  • In NAM, we can monitor on service announcements, requests, and responses as they happen in the network.

In this demonstration, we completely know how to implement the basic setup simulation and to know how to execute the Network Service Discovery in ns2 simulator tool. If you have any query regarding this process we also help to clarify it.

For any type of Network Service Discovery implementation using the NS2 tool, please feel free to share all relevant details with us via email, and we will provide guidance to achieve optimal results. Our team specializes in ad-hoc and mobile networks, and we can assist you with performance analysis for your projects.