How to Implement Content Delivery Networks in ns2

To implement a Content Delivery Network (CDN) within NS2 has encompasses mimicking a network of the distributed servers which the deliver content to users based on its geographical location and network conditions. Whereas the simulation tool NS2 doesn’t have built-in aid for CDNs, We can emulate the performance of a CDN by making several servers (nodes) and routing client requests to the closest or least-loaded server. For best simulation results you can  connect with us. Given below is an approach how we can execute a simple CDN within NS2:

Step-by-Step Implementations:

  1. Set Up the NS2 Environment:
  • Make sure NS2 is installed on the system.
  • Acquaint ourselves including the TCL scripting, as NS2 simulations are controlled through the TCL.
  1. Define the Network Topology:
  • Make a network topology including the clients and various servers signifying the CDN edge servers.

# Define the simulator

set ns [new Simulator]

# Create a trace file for analysis

set tracefile [open out.tr w]

$ns trace-all $tracefile

# Create a NAM file for animation

set namfile [open out.nam w]

$ns namtrace-all $namfile

# Define nodes: clients and CDN servers

set client1 [$ns node]

set client2 [$ns node]

set client3 [$ns node]

set server1 [$ns node]  ;# CDN server 1

set server2 [$ns node]  ;# CDN server 2

set server3 [$ns node]  ;# CDN server 3

  1. Set Up Links Between Nodes:
  • Ascertain links among the clients and servers, mimicking various network conditions like changing bandwidths and delays.

# Create duplex links between clients and servers

$ns duplex-link $client1 $server1 10Mb 20ms DropTail

$ns duplex-link $client1 $server2 10Mb 40ms DropTail

$ns duplex-link $client2 $server1 10Mb 15ms DropTail

$ns duplex-link $client2 $server3 10Mb 25ms DropTail

$ns duplex-link $client3 $server2 10Mb 30ms DropTail

$ns duplex-link $client3 $server3 10Mb 10ms DropTail

  1. Simulate Client Requests and CDN Response:
  • We can attach the UDP or TCP agents to the clients and servers to emulate the transfer of content. We can be used traffic generators such as FTP or CBR (Constant Bit Rate) to denote content delivery.

# Client 1 sends a request to the nearest server (server1)

set tcp_client1 [new Agent/TCP]

$ns attach-agent $client1 $tcp_client1

set tcp_server1 [new Agent/TCPSink]

$ns attach-agent $server1 $tcp_server1

$ns connect $tcp_client1 $tcp_server1

# Client 2 sends a request to the nearest server (server3)

set tcp_client2 [new Agent/TCP]

$ns attach-agent $client2 $tcp_client2

set tcp_server3 [new Agent/TCPSink]

$ns attach-agent $server3 $tcp_server3

$ns connect $tcp_client2 $tcp_server3

# Client 3 sends a request to the nearest server (server3)

set tcp_client3 [new Agent/TCP]

$ns attach-agent $client3 $tcp_client

set tcp_server3_2 [new Agent/TCPSink]

$ns attach-agent $server3 $tcp_server3_2

$ns connect $tcp_client3 $tcp_server3_2

  1. Configure Traffic Sources:
  • We can use the FTP or CBR applications to mimic the delivery of content from the servers to the clients.

# Create FTP applications to simulate content delivery

set ftp1 [new Application/FTP]

$ftp1 attach-agent $tcp_client1

$ns at 0.5 “$ftp1 start”

set ftp2 [new Application/FTP]

$ftp2 attach-agent $tcp_client2

$ns at 1.0 “$ftp2 start”

set ftp3 [new Application/FTP]

$ftp3 attach-agent $tcp_client3

$ns at 1.5 “$ftp3 start”

  1. Simulate CDN Routing Logic:
  • To implement a basic routing logic to direct client requests to the closest or least-loaded CDN server. It can be complete physically by setting up connections such as exposed overhead, or we can write a custom procedure that dynamically chooses the server based on the network conditions.

# Example of simple routing logic based on predefined conditions

proc route_request {client server1 server2 server3} {

# Logic to choose the server based on network conditions (e.g., delay, load)

# For simplicity, manually direct the request to the closest server

global ns

set tcp_client [new Agent/TCP]

$ns attach-agent $client $tcp_client

# Choose the nearest server (this is just a basic example)

set tcp_server [new Agent/TCPSink]

if {$client == “client1”} {

$ns attach-agent $server1 $tcp_server

} elseif {$client == “client2”} {

$ns attach-agent $server3 $tcp_server

} elseif {$client == “client3”} {

$ns attach-agent $server3 $tcp_server

}

$ns connect $tcp_client $tcp_server

# Start the FTP application to simulate content delivery

set ftp [new Application/FTP]

$ftp attach-agent $tcp_client

$ns at 2.0 “$ftp start”

}

# Call the routing logic for each client

route_request $client1 $server1 $server2 $server3

route_request $client2 $server1 $server2 $server3

route_request $client3 $server1 $server2 $server3

  1. Run the Simulation:
  • We can describe while the simulation would end and then run it. The end process will close the trace files and introduce the NAM for visualization.

# Define the finish procedure

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam out.nam &

exit 0

}

# Schedule the finish procedure at 10 seconds

$ns at 10.0 “finish”

# Run the simulation

$ns run

  1. Analyse the Results:
  • We can use the trace file (out.tr) to evaluate the packet delivery, delays, throughput, and other performance parameters.
  • We open the NAM file (out.nam) to visualize the network operations and traffic flow.
  1. Customize and Extend:
  • We can modify the simulation by:
    • Fine-tuning the network conditions such as link bandwidth, delays.
    • To executing more difficult routing logic to enthusiastically choose the right CDN server based on the present network load and conditions.
    • To launching the load balancing, caching mechanisms, or various traffic patterns to denote real-world CDN performances.
    • We appending more clients and servers to mimic a larger CDN network.

Example Summary:

This instance sets up a simple CDN simulation in the simulation tool NS2. The clients are send the requests to the closest CDN server, and the servers react by delivering content. The emulation uses TCP for reliable data transfer, and the content delivery is emulated using the FTP applications.

Advanced Considerations:

  • For more exact CDN simulations, we deliberate incorporating the more characteristics such as content caching, dynamic load balancing, and real-time network condition observing.
  • If we want to emulate further complex CDN behaviours, like multi-tier CDNs or edge computing, and we may essential to expand the NS2 with custom code or scripts.

Debugging and Optimization:

  • We can use the trace-all command to debug the emulation and investigate packet flows.
  • To improve the simulation by tuning TCP parameters, modifying link properties, and refining the routing logic.

Hence, the step-by-step procedure was applied to the Content Delivery Networks, with the implementation and analysis performed through the simulation tool ns2. We will offer additional insights on this topic based on your needs.