How to Calculate Network Stalling in Ns3

To calculate stalling in ns3, we have to track instances when the buffer runs out of data, causing playback interruptions in streaming applications. For evaluating the performance of streaming applications, Stalling events are critical metrics. Here is the interesting guide on calculating stalling in ns3.

Steps for calculation

1. Set up your ns3 :

• Make sure that ns3 is installed in the computer. If not, install it.

2. Create a new ns3 script :

• In the scratch directory of ns3, create a new script.

3. Include necessary libraries :

• In your script, include the necessary libraries.

4. Define network topology :

• For your network topology, create multiple nodes.

5. Implement buffer management :

• To simulate buffering at the receiving node, use the PacketSink application. To track buffer occupancy and stalling events, implement the logic.

Example for calculating stalling in ns3

Here is the example for the calculation of stalling :

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/applications-module.h”

#include “ns3/packet-sink.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“StallingCalculationExample”);

uint32_t bufferOccupancy = 0;

uint32_t stallingEvents = 0;

double lastEventTime = 0.0;

void CalculateStalling(Ptr<PacketSink> sink, Time interval, Time playbackRate, uint32_t bufferThreshold)

{

static uint64_t lastTotalRx = 0;

uint64_t totalRx = sink->GetTotalRx();

uint64_t rxBytes = totalRx – lastTotalRx;

lastTotalRx = totalRx;

bufferOccupancy += rxBytes;

// Simulate buffer consumption

bufferOccupancy = (bufferOccupancy >= playbackRate.GetNanoSeconds()) ? bufferOccupancy – playbackRate.GetNanoSeconds() : 0;

// Check for stalling

if (bufferOccupancy < bufferThreshold)

{

if (Simulator::Now().GetSeconds() – lastEventTime > 1.0) // Assuming at least 1 second between stall events

{

stallingEvents++;

lastEventTime = Simulator::Now().GetSeconds();

std::cout << “Stalling event at ” << Simulator::Now().GetSeconds() << “s, total stalling events: ” << stallingEvents << std::endl;

}

}

Simulator::Schedule(interval, &CalculateStalling, sink, interval, playbackRate, bufferThreshold); // Schedule next calculation

}

int main(int argc, char *argv[])

{

uint32_t nNodes = 2; // Number of nodes

double simulationTime = 60.0; // Total simulation time in seconds

Time calculationInterval = Seconds(1.0); // Interval to calculate stalling

Time playbackRate = MilliSeconds(500); // Rate at which buffer is consumed (e.g., 500ms per second of playback)

uint32_t bufferThreshold = 1024; // Threshold for buffer to consider stalling (in bytes)

CommandLine cmd;

cmd.AddValue(“nNodes”, “Number of nodes”, nNodes);

cmd.AddValue(“simulationTime”, “Total simulation time”, simulationTime);

cmd.AddValue(“calculationInterval”, “Interval to calculate stalling”, calculationInterval);

cmd.AddValue(“playbackRate”, “Rate at which buffer is consumed”, playbackRate);

cmd.AddValue(“bufferThreshold”, “Threshold for buffer to consider stalling”, bufferThreshold);

cmd.Parse(argc, argv);

NodeContainer nodes;

nodes.Create(nNodes);

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute(“DataRate”, StringValue(“5Mbps”));

pointToPoint.SetChannelAttribute(“Delay”, StringValue(“2ms”));

NetDeviceContainer devices;

devices = pointToPoint.Install(nodes);

InternetStackHelper stack;

stack.Install(nodes);

Ipv4AddressHelper address;

address.SetBase(“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces = address.Assign(devices);

uint16_t port = 9;

Address sinkAddress(InetSocketAddress(interfaces.GetAddress(1), port));

PacketSinkHelper packetSinkHelper(“ns3::UdpSocketFactory”, sinkAddress);

ApplicationContainer sinkApps = packetSinkHelper.Install(nodes.Get(1));

sinkApps.Start(Seconds(0.0));

sinkApps.Stop(Seconds(simulationTime));

Ptr<Socket> sourceSocket = Socket::CreateSocket(nodes.Get(0), TypeId::LookupByName(“ns3::UdpSocketFactory”));

sourceSocket->Connect(sinkAddress);

// Simulate sending data

Ptr<UniformRandomVariable> var = CreateObject<UniformRandomVariable>();

Simulator::ScheduleWithContext(sourceSocket->GetNode()->GetId(), Seconds(1.0), &GenerateTraffic, sourceSocket, var, 1024, 1000);

Simulator::Schedule(calculationInterval, &CalculateStalling, DynamicCast<PacketSink>(sinkApps.Get(0)), calculationInterval, playbackRate, bufferThreshold);

Simulator::Stop(Seconds(simulationTime));

Simulator::Run();

Simulator::Destroy();

std::cout << “Total stalling events: ” << stallingEvents << std::endl;

return 0;

}

void GenerateTraffic(Ptr<Socket> socket, Ptr<UniformRandomVariable> var, uint32_t pktSize, uint32_t pktCount)

{

if (pktCount > 0)

{

socket->Send(Create<Packet>(pktSize));

Simulator::Schedule(Seconds(var->GetValue(0.05, 0.1)), &GenerateTraffic, socket, var, pktSize, pktCount – 1);

}

}

Explanation

1. Nodes and links :

Nodes are created. Point-to-point links between nodes are configured.

2. Applications :

On one node, a PacketSink is installed to simulate buffering at the receiving node. and On another node, sockets are created to send packets.

3. Buffer rate calculation :

To calculate the buffer rate by measuring the amount of data received over time, CalculateBufferRate is implemented. Scheduled the buffer rate calculation at regular intervals using the Simulator::Schedule function.

4. Traffic generation :

To to simulate sending data from the source node to the sink node,  GenerateTraffic is implemented. Scheduled the stalling calculation at regular intervals using the Simulator::Schedule function.

5. Running the Simulation :

The simulation runs by sending and receiving the packets.

We had successfully calculated stalling in ns3 by tracking instances when the buffer runs out of data, causing playback interruptions in streaming applications.

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