To simulate Content Delivery Networks (CDNs) using NS2, which encompasses modeling a network in which content (such as web pages, videos, or files) is distributed through several geographically dispersed servers (also known as edge servers or cache servers) to enhance availability, minimize latency, and balance network traffic. The key components of a CDN contain clients, cache servers (distributed across different locations), and an origin server in which the content is hosted.
The aim of a CDN is to distribute content from the server closest to the client, reducing latency and enhancing bandwidth. The simulation environment NS2 permits to replicate a CDN architecture, learn traffic patterns, and examine network performance.
We work on simulation based on your project, send us all your details we will help you further with detailed explanation.
The following is a step-by-step instruction to replicate Content Delivery Networks (CDNs) using NS2.
Steps to Simulate Content Delivery Networks Using NS2
- Install NS2:
Make sure that NS2 is installed and running on the system. We can download it from the NS2 official website. NS2 can be utilized to replicate CDN-like networks using its built-in capabilities to model clients, cache servers, and routing behaviours.
- Define the CDN Network Topology:
A CDN normally encompasses:
- Clients: End users who request content.
- Cache servers (edge servers): These servers are placed near clients and serve cached content.
- Origin server: The original content source that serves content when it’s not obtainable in the cache.
- Routers and links: To connect clients, edge servers, and the origin server.
Example of defining a basic CDN topology with multiple cache servers:
set ns [new Simulator]
# Create nodes: clients, cache servers, origin server, and routers
set client1 [$ns node]
set client2 [$ns node]
set cache1 [$ns node]
set cache2 [$ns node]
set originServer [$ns node]
set router1 [$ns node]
set router2 [$ns node]
set router3 [$ns node]
# Define links between clients, routers, and cache/origin servers
$ns duplex-link $client1 $router1 10Mb 10ms DropTail
$ns duplex-link $client2 $router2 10Mb 20ms DropTail
$ns duplex-link $router1 $cache1 100Mb 5ms DropTail
$ns duplex-link $router2 $cache2 100Mb 5ms DropTail
$ns duplex-link $router3 $originServer 1Gb 30ms DropTail
In this example:
- client1 and client2 are end users who request content.
- cache1 and cache2 are edge cache servers placed closer to the clients.
- originServer is the central server in which the original content resides.
- router1, router2, and router3 are utilized to route traffic among the clients and cache/origin servers.
- Links are described with distinct bandwidths and delays to reflect real-world WAN and LAN characteristics.
- Configure TCP or UDP Agents:
TCP is normally utilized in CDN projects since content delivery frequently includes reliable data transmission (e.g., web pages, files, or video streaming). We can configure TCP agents on both the clients and servers to replicate data requests and responses.
Example of setting up TCP agents:
# Create TCP agents for communication between client1 and cache1
set tcpClient1 [new Agent/TCP]
set sinkCache1 [new Agent/TCPSink]
$ns attach-agent $client1 $tcpClient1
$ns attach-agent $cache1 $sinkCache1
$ns connect $tcpClient1 $sinkCache1
Repeat the similar configure for other clients and servers.
- Simulate Content Requests and Cache Hits/Misses:
In a CDN, a client may either:
- Hit the cache: The requested content is discovered on a neighbouring cache server.
- Miss the cache: The content is fetched from the origin server.
We can be replicated cache hits and misses by directing a few traffic to the cache servers and others directly to the origin server, based on whether the requested content is cached.
Example of handling a cache hit:
# Simulate a file transfer from cache1 to client1 (cache hit)
set ftpClient1 [new Application/FTP]
$ftpClient1 attach-agent $tcpClient1
Example of handling a cache miss (fetching from the origin server):
# Simulate a file transfer from the origin server to cache1 (cache miss)
set tcpCacheOrigin [new Agent/TCP]
set sinkOrigin [new Agent/TCPSink]
$ns attach-agent $cache1 $tcpCacheOrigin
$ns attach-agent $originServer $sinkOrigin
$ns connect $tcpCacheOrigin $sinkOrigin
set ftpCacheOrigin [new Application/FTP]
$ftpCacheOrigin attach-agent $tcpCacheOrigin
We can also replicate random access patterns by creating a few requests go to the cache server, even though others go directly to the source server.
- Simulate Traffic Load (CBR, FTP, or HTTP Requests):
Traffic load in a CDN can be mimicked utilizing CBR (Constant Bit Rate) for continuous streaming traffic or FTP/HTTP for web traffic. For more realistic CDN traffic, we can model HTTP requests in which clients request small files (e.g., web pages or video chunks).
Example of generating FTP traffic (representing a file download):
# Simulate a file download from cache1 to client1
set ftpTraffic1 [new Application/FTP]
$ftpTraffic1 attach-agent $tcpClient1
For continuous video streaming (simulated by CBR):
# Simulate continuous video streaming (CBR traffic) from cache1 to client1
set cbrTraffic1 [new Application/Traffic/CBR]
$cbrTraffic1 set packetSize_ 1024 ;# Packet size in bytes
$cbrTraffic1 set interval_ 0.01 ;# Packet interval (send one packet every 10 ms)
$cbrTraffic1 attach-agent $tcpClient1
# Start traffic at 1 second
$ns at 1.0 “$cbrTraffic1 start”
- Simulate Cache Management and Redirection (Optional):
In real CDNs, if a cache misses then the content is fetched from the source server and stored in the cache for future requests. We can replicate it by having the cache server recover content from the origin server upon a cache miss and then redirect subsequent client requests to the cache.
Example of simulating cache redirection:
# First, client1’s request goes to the origin server (cache miss)
$ns at 2.0 “$ftpCacheOrigin start”
# Then, client1’s subsequent request is served from cache1 (cache hit)
$ns at 5.0 “$ftpClient1 start”
This sequence models a cache miss followed by a cache hit.
- Simulate Content Placement Strategies (Optional):
CDNs frequently utilize content placement strategies in which content is distributed across distinct cache servers according to the proximity, popularity, or other policies. We can mimic distinct strategies by pre-placing content on particular cache servers or by actively modifying the content placement in the course of the simulation.
Example of simulating static content placement:
# Pre-place content on cache1 to serve client1 (simulate static content placement)
set ftpCache1 [new Application/FTP]
$ftpCache1 attach-agent $tcpClient1
Also, we can dynamically decide which server should serve content according to the network conditions, replicating a more advanced CDN with adaptive content placement.
- Run the Simulation:
After configuring the topology, traffic, and cache mechanisms then we can run the simulation using NS2.
Example of running the simulation:
ns cdn_simulation.tcl
We can also envision the CDN traffic utilizing NAM (Network Animator) to monitor how content requests are routed via the cache and origin servers:
nam cdn_simulation.nam
- Analyze Results:
After running the simulation then we can examine the trace file to extract performance parameters like:
- Throughput: Calculate how much data was delivered to clients.
- Latency: Estimate the time taken to deliver content from cache or origin servers.
- Cache Hit/Miss Ratio: Compute the percentage of cache hits against cache misses.
- Network Load: Investigate the load on distinct links and servers to know how content delivery is enhanced.
Example of analyzing traffic using AWK:
awk ‘{if ($1==”r” && $4==”AGT” && $7==”TCP”) print $0}’ cdn_trace.tr
It will show all TCP packet receptions in the simulation that can be utilized to assess throughput and latency.
- Advanced CDN Features (Optional):
- Content Replication: Replicate content replication strategies in which popular content is simulated across several cache servers.
- Load Balancing: Execute load balancing strategies in which traffic is distributed across cache servers according to the load or proximity.
- Content Replacement Policies: Mimic distinct content replacement policies, like LRU (Least Recently Used) or LFU (Least Frequently Used), to model cache eviction behaviour.
We established simulation steps to replicate and analyse the Content Delivery Networks projects utilizing NS2 platform. We can dive deeper into subject and share thorough illustrations, if asked.
