To simulate Content-Centric Networking (CCN) or Named Data Networking (NDN) projects utilizing NS2 that needs setting up a network architecture in which the attention is on content retrieval by name insert of by the host IP address. Even though NS2 does not natively support CCN/NDN, we can prolong its functionality to replicate these kinds of networks. It can be done by changing the existing network layers or utilizing add-on libraries like NDNSim (an NDN simulator built on top of NS3).
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But, to replicate simple CCN/NDN concepts in NS2, follow this instructions:
Steps to Simulate Content Centric Network Projects in NS2
- Understand Content-Centric Networking (CCN) in NS2
- Interest and Data Packets: CCN/NDN works by clients transmitting “Interest” packets to request data, and nodes or servers reacting with “Data” packets.
- Caching: Nodes along the path can cache data to minimize retrieval time for future requests.
- Names instead of IPs: Rather than using IP addresses, content is fetched by names (content names or data identifiers).
- Install NS2
- We can download and install NS2 from the official NS2 website.
- Make certain that we have all essential libraries (e.g., Tcl/Tk) to run NS2 simulations.
- Extend NS2 to Support CCN/NDN Features
- Since NS2 does not natively support CCN/NDN, we will want to expand NS2’s functionality. Change the routing and application layers to replicate the exchange of Interest and Data packets.
- We will likely require to expand the core NS2 C++ modules (e.g., agent.cc, packet.h, etc.) to launch new packet types for Interest and Data.
- Define Interest and Data Packets
- Make a custom packet headers for the CCN/NDN Interest and Data packets by prolonging NS2’s Packet class. Each packet will encompass the content name (instead of IP addresses).
Example of Packet Header for Interest and Data Packets:
class CCNInterestHeader {
char contentName[100]; // Name of the content being requested
double timestamp; // Time of the request
};
class CCNDataHeader {
char contentName[100]; // Name of the content being returned
int dataSize; // Size of the data
};
Insert these packet types to packet.h and register them in NS2 utilizing the PacketHeaderManager class.
- Modify Routing to Support CCN/NDN
- In CCN, routing is done by name prefix matching instead of IP address lookup. We can change or prolong NS2’s routing protocols (like AODV or DSR) to execute name-based routing tables.
- We will also be required to execute a Pending Interest Table (PIT) and a Forwarding Information Base (FIB) that will help nodes route Interest packets rely on content names.
Example OTcl Code to Create Routing for CCN:
# Define a simple topology for CCN/NDN
set ns [new Simulator]
set topo [new Topography]
$topo load_flatgrid 1000 1000
# Create nodes (clients, routers, and servers)
for {set i 0} {$i < 6} {incr i} {
set node($i) [$ns node]
}
# Set up links between nodes
$ns simplex-link $node(0) $node(1) 1Mb 10ms DropTail
$ns simplex-link $node(1) $node(2) 1Mb 10ms DropTail
$ns simplex-link $node(2) $node(3) 1Mb 10ms DropTail
$ns simplex-link $node(3) $node(4) 1Mb 10ms DropTail
$ns simplex-link $node(4) $node(5) 1Mb 10ms DropTail
# Routing Table setup for CCN
$node(0) add-fib-entry “/content1” $node(1)
$node(1) add-fib-entry “/content1” $node(2)
$node(2) add-fib-entry “/content1” $node(3)
# Simulate Content-Centric Interest request from node 0
$ns at 1.0 “$node(0) send-interest /content1”
In this instance, the FIB is configure manually, connecting content names with next-hop nodes.
- Implement Content Caching
- Each node should have the ability to cache Data packets, which traverse it. It helps to minimize future Interest requests for the similar content.
- We can execute a basic caching mechanism using an array or linked list to store currently fetched content.
Example Caching Mechanism:
class Cache {
map<string, DataPacket> contentCache;
void storeContent(string contentName, DataPacket data) {
contentCache[contentName] = data;
}
DataPacket retrieveContent(string contentName) {
if (contentCache.find(contentName) != contentCache.end()) {
return contentCache[contentName];
}
return NULL; // If content is not in the cache
}
};
Prolong the node class to contain this caching functionality and then change the Interest processing logic to initially verify the cache before sending the Interest packet.
- Handle Interest and Data Packet Exchange
- Once a node receives an Interest packet then it verifies its cache. If the content is not in the cache then the Interest is sent to the next node rely on the FIB.
- When a node (or server) has the requested data then it transmits a Data packet back to the source of the Interest, caching the content along the path.
Example of Interest/Data Processing Logic:
void Node::handleInterest(InterestPacket interest) {
DataPacket cachedData = cache.retrieveContent(interest.contentName);
if (cachedData != NULL) {
// Respond with cached data
sendDataPacket(cachedData, interest.originNode);
} else {
// Forward Interest to next hop based on FIB
forwardInterest(interest);
}
}
void Node::handleData(DataPacket data) {
cache.storeContent(data.contentName, data); // Cache the data
// Forward Data back to the origin node
forwardData(data);
}
- Traffic and Application Models
- We can utilize UDP to replicate lightweight Interest and Data packet exchange, or make a custom traffic generator for more complex CCN applications.
Example Traffic Model:
# Create an application to send Interest packets
set udp [new Agent/UDP]
$ns attach-agent $node(0) $udp
set null [new Agent/Null]
$ns attach-agent $node(1) $null
$ns connect $udp $null
set interestTraffic [new Application/Traffic/CBR]
$interestTraffic set packetSize_ 512
$interestTraffic set rate_ 100kb
$interestTraffic attach-agent $udp
$ns at 1.0 “$interestTraffic start”
- Simulation Execution
- We can run the CCN/NDN simulation using the set up OTcl script.
ns ccn_simulation.tcl
- Analyze the Results
- We can utilize the generated trace files to investigate the performance of the CCN simulation. We can be assessed the latency, throughput, and cache hit ratio.
- Extract informations from trace files using awk, Perl, or Python scripts.
Example Trace Analysis (Using Awk):
awk -f trace_analysis.awk output.tr
- Visualization
- We can be used NS2’s Network Animator (NAM) to envision the communication among the nodes that indicating Interest and Data packet flows.
nam ccn_simulation.nam
Example Simulation Script Outline for CCN/NDN
# Simulation script for CCN/NDN in NS2
set ns [new Simulator]
set topo [new Topography]
$topo load_flatgrid 500 500 ;# Smaller topology for short-range communication
# Create CCN/NDN nodes
for {set i 0} {$i < 5} {incr i} {
set node($i) [$ns node]
}
# Create links between nodes (simulating CCN/NDN network)
$ns simplex-link $node(0) $node(1) 10Mb 10ms DropTail
$ns simplex-link $node(1) $node(2) 10Mb 10ms DropTail
$ns simplex-link $node(2) $node(3) 10Mb 10ms DropTail
$ns simplex-link $node(3) $node(4) 10Mb 10ms DropTail
# Interest and Data Traffic
set udp [new Agent/UDP]
$ns attach-agent $node(0) $udp
set null [new Agent/Null]
$ns attach-agent $node(1) $null
$ns connect $udp $null
set interestTraffic [new Application/Traffic/CBR]
$interestTraffic set packetSize_ 512
$interestTraffic set rate_ 500Kb
$interestTraffic attach-agent $udp
$ns at 1.0 “$interestTraffic start”
# Define end of the simulation
$ns at 10.0 “finish”
Key Points
- Interest and Data Packets: Launch new packet types for CCN/NDN Interest and Data packets.
- Name-Based Routing: Alter the routing protocols to work with name prefixes instead of IP addresses.
- Caching: Execute in-network caching to improve content retrieval efficiency.
- Analysis: Extract parameters like cache hit ratio, latency, and throughput from trace files.
We outlined simulation steps to model and evaluate the Content Centric network project with the help of NS2 simulator. We are prepared to distribute detailed insights and further data upon your request.
