Using Flow Monitor to generate statistics about real Tap Bridge data flows

[Rafael Fernandes Lopes]

Hi,

I am conducting a research related to the evaluation of some real implemented protocols considering some scenarios (easily configured in the NS-3). As a starting point, I am adapting the tap-wifi-virtual-machine example in order to verify the statistics generated by the Flow Monitor. However, when I run the example, the NS-3 returns a SIGSEGV exactly when I interact with the monitor object. Someone has experimented do something like this?

The error:

Checking for lost packets...

Command ['/usr/local/ns-allinone-3.22/ns-3.22/build/src/tap-bridge/examples/ns3.22-tap-wifi-virtual-machine-debug'] terminated with signal SIGSEGV. Run it under a debugger to get more information (./waf --run <program> --command-template="gdb --args %s <args>").

The code:

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  ...... // same code of the tap-wifi-machine example

  TapBridgeHelper tapBridge;

  tapBridge.SetAttribute ("Mode", StringValue ("UseLocal"));

  tapBridge.SetAttribute ("DeviceName", StringValue ("tap-left"));

  tapBridge.Install (nodes.Get (0), devices.Get (0));

  tapBridge.SetAttribute ("DeviceName", StringValue ("tap-right"));

  tapBridge.Install (nodes.Get (1), devices.Get (1));

  // Install FlowMonitor on all nodes

  FlowMonitorHelper flowmon;

  Ptr<FlowMonitor> monitor = flowmon.InstallAll();

  Simulator::Stop (Seconds (30.)); // 600.

  Simulator::Run ();

  NS_LOG_UNCOND("Checking for lost packets...");

  monitor->CheckForLostPackets ();

  NS_LOG_UNCOND("Getting flows...");

  

  Ptr<Ipv4FlowClassifier> classifier = DynamicCast<Ipv4FlowClassifier> (flowmon.GetClassifier ());

  std::map<FlowId, FlowMonitor::FlowStats> stats = monitor->GetFlowStats ();

  NS_LOG_UNCOND("Checking flows...");

  

  for (std::map<FlowId, FlowMonitor::FlowStats>::const_iterator iter = stats.begin (); iter != stats.end (); ++iter)

    {

      Ipv4FlowClassifier::FiveTuple t = classifier->FindFlow (iter->first);

      const uint16_t port = 4324;

      

      if (t.sourcePort == port || t.destinationPort == port) {

        NS_LOG_UNCOND("Flow ID: " << iter->first << " Src Addr " << t.sourceAddress << " Dst Addr " << t.destinationAddress << " Protocol " << t.protocol);

        NS_LOG_UNCOND("Tx Packets = " << iter->second.txPackets);

        NS_LOG_UNCOND("Rx Packets = " << iter->second.rxPackets);

        NS_LOG_UNCOND("Throughput: " << iter->second.rxBytes * 8.0 / (iter->second.timeLastRxPacket.GetSeconds()-iter->second.timeFirstTxPacket.GetSeconds()) / 1024  << " Kbps");

      }

    }

  Simulator::Destroy ();

 }

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Best regards,

Rafael

[Tommaso Pecorella]

Hi,

thanks for the bug report.

It's a bug indeed, as the script should have given a meaningful error message instead of a segmentation fault.

The problem is that we didn't foresee the case where a user would want to install FlowMonitor over a set of nodes that doesn't have any IP stack.

No IP, no FlowMonitor, no statistics, the "monitor" pointer is null, crash.

And now... you are lucky that I figured it out just by thinking to it. Next time attach the full code and a meaningful debugger backtrace. 

Have fun,

T.

[Rafael Fernandes Lopes]

Thanks for the response. Do you have some idea how to calculate the statistics in this case (using the Tap Bridge system)?

Thanks.

Best regards,

Rafael

[Tommaso Pecorella]

Hi,

FlowMonitor will only help you if the flows are from/to ns-3 nodes.

In your case it depends on the protocol. For a general network test I'd use iperf, but it depends on the protocol.

T.

[Rafael Fernandes Lopes]

I see... I am evaluating a protocol derived from UDP. I have two applications (one on each VM) transferring a file a number of times. I don't know if iperf can help in this problem.

Anyway, thank you for your time and support.

Best regards,

Rafael. 

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--

Rafael Fernandes Lopes
CV Lattes: http://lattes.cnpq.br/1972734433460838
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Professor Adjunto

Departamento Acadêmico de Informática - DAI
Instituto Federal de Educação, Ciência e Tecnologia do Maranhão - IFMA
http://www.dai.ifma.edu.br

Pesquisador Associado
Instituto de Estudos Avançados em Comunicações - Iecom
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