How to Start Content Delivery Networks Projects Using NS2

To start a Content Delivery Network (CDN) project using Network Simulator 2 (NS2) which encompasses to replicate the distributed system that are created to distribute the content efficiently like web pages, videos, or software to end-users, it is frequently leveraging a servers network which is located in diverse geographical positions purposefully. While NS2 is a robust tool to replicate the diverse networking scenarios, to replicate a CDN within NS2 environment that needs to design numerous modules with content servers, edge caches, clients, and traffic distribution procedures.

Here’s a detailed technique to get started a CDN project using NS2.

Steps to Start CDN Projects in NS2

Step 1: Understand the Basics of CDNs

A Content Delivery Network (CDN) is created for minimizing latency and enhancing the content delivery performance by means of storing copies of content at diverse edge servers are placed near by end-users. CDNs utilise some methods like:

  • Caching: Caching content on servers nearby user for minimizing load times.
  • Load Balancing: To deliver the user demands over numerous servers for enhancing the performance and reducing congestion.
  • Geographic Distribution: Servers are positioned in various areas to make sure that content is distributed to users effectively.

We make a network topology in NS2, to replicate a CDN:

  • Content Servers (Origin Servers): Hosts to cache the original content.
  • Edge Servers (Cache Servers): Servers close end-users to save the cached content.
  • Clients (End Users): Nodes, which demand the content for clients.

Step 2: Set Up NS2

Initially, we can install NS2 on the system. Unless, we should adhere to the official NS2 installation instruction based on the OS like Linux, macOS, or Windows.

Step 3: Design Your CDN Topology

Following is key components of CDN topology:

  • Multiple Edge Servers: To denote the cache servers, which cache the copies of content.
  • One or More Content Servers: To specify the source servers those hold the original content.
  • Clients: Denoting the end-users who demand the content.

We can replicate content delivery’s various features like:

  • Observe how clients demand the content from cache servers or source servers.
  • Focus on how content is stored or functioned from the edge servers.
  • The load balancing or request routing logic for selecting the optimal server to distribute the content.

Step 4: Create a Basic CDN Simulation

Below is a simple NS2 script, which mimics a CDN including several edge servers and one content server. In this example, from edge servers clients demand the content and if the content is not obtainable then the edge server obtains it from the source content server.

Example NS2 Script for CDN Simulation:

# Create the simulator

set ns [new Simulator]

# Create nodes (clients, edge servers, and content servers)

set content_server [$ns node]     ;# Origin content server

set edge_server1 [$ns node]       ;# Edge cache server 1

set edge_server2 [$ns node]       ;# Edge cache server 2

set client1 [$ns node]            ;# Client 1

set client2 [$ns node]            ;# Client 2

set client3 [$ns node]            ;# Client 3

# Create links between nodes (using Ethernet links)

$ns duplex-link $content_server $edge_server1 1Mb 10ms DropTail

$ns duplex-link $content_server $edge_server2 1Mb 10ms DropTail

$ns duplex-link $edge_server1 $client1 1Mb 10ms DropTail

$ns duplex-link $edge_server1 $client2 1Mb 10ms DropTail

$ns duplex-link $edge_server2 $client3 1Mb 10ms DropTail

# Set up UDP traffic from clients to edge servers (requesting content)

set udp1 [new Agent/UDP]

set udp2 [new Agent/UDP]

set udp3 [new Agent/UDP]

$ns attach-agent $client1 $udp1

$ns attach-agent $client2 $udp2

$ns attach-agent $client3 $udp3

# Set up Null agents to simulate the content request behavior

set null1 [new Agent/Null]        ;# Null agent simulates request handling at edge server

set null2 [new Agent/Null]

$ns attach-agent $edge_server1 $null1

$ns attach-agent $edge_server2 $null2

$ns connect $udp1 $null1         ;# Client 1 sends requests to Edge Server 1

$ns connect $udp2 $null1         ;# Client 2 sends requests to Edge Server 1

$ns connect $udp3 $null2         ;# Client 3 sends requests to Edge Server 2

# Set up CBR application to simulate content requests

set cbr1 [new Application/Traffic/CBR]

set cbr2 [new Application/Traffic/CBR]

set cbr3 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

$cbr2 attach-agent $udp2

$cbr3 attach-agent $udp3

# Set the traffic parameters

$cbr1 set packetSize_ 512

$cbr1 set interval_ 0.1

$cbr2 set packetSize_ 512

$cbr2 set interval_ 0.1

$cbr3 set packetSize_ 512

$cbr3 set interval_ 0.1

# Start the traffic (content requests from clients)

$ns at 0.5 “$cbr1 start”

$ns at 0.5 “$cbr2 start”

$ns at 0.5 “$cbr3 start”

$ns at 4.5 “$cbr1 stop”

$ns at 4.5 “$cbr2 stop”

$ns at 4.5 “$cbr3 stop”

# Set finish time for simulation

$ns at 5.0 “finish”

# Finish simulation and clean up

proc finish {} {

global ns

$ns flush-trace

exit 0

}

# Run the simulation

$ns run

Explanation of the Script:

  1. Simulator Setup:
    • set ns [new Simulator]: It makes the NS2 simulator entity.
  2. Node Creation:
    • set content_server [$ns node]: It helps to make the content server (origin server), which stores the original content.
    • set edge_server1, set edge_server2: Generates two edge servers that perform like cache servers.
    • set client1, set client2, set client3: These supports to make three clients, which will be demanded the content.
  3. Link Creation:
    • duplex-link: It makes bidirectional connection among the nodes. The edge servers are associated to the clients and the content server is linked to the edge servers.
  4. UDP Traffic Setup:
    • Agent/UDP: Denotes the UDP protocol which is leveraged to transmit the content demands among the clients and edge servers.
    • Agent/Null: A Null agent replicates the acquiring edge server behavior (no response is retransmitted to the client).
    • Application/Traffic/CBR: Constant Bit Rate (CBR) is utilised for making reliable packet traffic (requests).
  5. Traffic Simulation:
    • $cbr1 start, $cbr2 start, $cbr3 start: For the clients, it begins the content request generation.
    • $cbr1 stop, $cbr2 stop, $cbr3 stop: After 4.5 seconds, it ends the traffic.
  6. Finish Simulation:
    • End the simulation is known as finish simulation which ends after 5 seconds and clear the trace files.

Step 5: Running the Simulation

To execute the simulation:

  1. We need to store the script like cdn_simulation.tcl.
  2. Then, execute the simulation to utilise below command:

ns cdn_simulation.tcl

Step 6: Analyzing Results

NS2 environment will be utilised a trace file (e.g., *.tr) with in-depth data regarding network events like packet arrival times, packet loss, delays, and so on. Also, we will want to examine these outcomes with the support of Xgraph or AWK.

To visualize results with Xgraph:

xgraph tracefile.tr

To utilise AWK scripts, obtain certain data like packet loss or throughput:

awk ‘{ if ($1 == “r”) print $0 }’ tracefile.tr > received_packets.txt

Step 7: Experimenting with CDN Scenarios

After basic simulation is executed then we need to test with diverse scenarios of CDN:

  1. Content Caching Behavior: Replicate how content is stored at edge servers. We should design the cache hit/miss behavior and then launch cache expiration strategies.
  2. Request Routing and Load Balancing: Mimic a routing algorithm for choosing the nearby or well-performing edge server. Execute the load balancing policies according to the client demands.
  3. Geographical Distribution: Integrate additional edge servers for replicating a larger geographical distribution and experiment how CDN enhances the effectiveness with additional servers.
  4. Traffic Types: Design video streaming, file downloads, or real-time applications such as VoIP to utilise diverse kinds of traffic.

Step 8: Advanced CDN Concepts in NS2

To discover more advanced concepts of CDN simulations in NS, we can:

  1. Content Prefetching: Design how content is prefetching to caches depends on the predicted request.
  2. Adaptive Streaming: Mimic adaptive streaming mechanisms in which video quality modifies according to the network situations.
  3. Dynamic Content Updates: Replicate how content modernizes from the source server to edge servers that are occurring in real-time.

Step 9: Documentation and Reporting

It provides detailed documentation or report including:

  1. Network Topology: Define the CDN structure as volume of edge servers, content servers, clients.
  2. Traffic Model: Describe the type of traffic to be mimicked the traffic patterns like CBR, video, file download.
  3. Simulation Results: It supports to examine the simulation outcomes on metrics like throughput, delay, cache hit/miss ratio, and packet loss.
  4. Conclusion: Sum up the performance of CDN relies on the simulation.

We had provided the complete details about how to simulate and test the Content Delivery Networks in diverse scenarios using the NS2 tool. We plan to elaborate the details about the CRN projects in upcoming guide.