Setting Maximum queue size in a CsmaNetDevice

[Dani Camps]

Dear all,

I am struggling with configuring a DropTailQueue of a certain size in
a CsmaNetDevice, and would appreciate any help. I have tried different
methods:

1- Config::SetDefault ("ns3::DropTailQueue::MaxPackets", UintegerValue
(50));
CsmaHelper csma;
NetDeviceContainer devices = csma.Install (nodes);

Expecting that by default a DropTailQueue of 50 packets would be
installed in the devices. However, the previous does not work.

2- I tried with the SetQueue method of the CsmaHelper class.
CsmaHelper csma;

csma.SetQueue(std::string("DropTailQueue"),std::string("MaxPackets"),IntegerValue(50));
NetDeviceContainer devices = csma.Install (nodes);

However, the previous does not work either, I get compilation errors
complaining about an incorrect TypeID, basically I do not seem to be
able to pass the correct parameters to the method SetQueue() and I
have not found any example in the existing code.

3- I try to set the queues manually:
NetDeviceContainer devices = csma.Install (nodes);
Ptr<CsmaNetDevice> csma_device_aux = devices.Get(0)-
>GetObject<CsmaNetDevice> ();
csma_device_aux->SetQueue (CreateObject<DropTailQueue> ());
Ptr<DropTailQueue> dtq = csma_device_aux->GetQueue()-
>GetObject<DropTailQueue> ();
dtq->SetAttribute("MaxPackets", UintegerValue (60));

The previous does compile, but when I run my experiment I see that the
queue is not yet limited to 50 packets. Actually, th experiment I run
seems to have unbounded queues (?).

The way I capture the queue size is by tracing the Enqueue and Dequeue
events defined in the Queue class:
QueueMonitor QMon;
Ptr<CsmaNetDevice> csma_device = devices.Get(0)-
>GetObject<CsmaNetDevice> ();
csma_device->GetQueue()->TraceConnectWithoutContext ("Enqueue",
MakeCallback(&QueueMonitor::TraceEnqueue, &QMon));
csma_device->GetQueue()->TraceConnectWithoutContext ("Dequeue",
MakeCallback(&QueueMonitor::TraceDequeue, &QMon));

It could also be that I am making a mistake there.

Thanks in advance for your advice!

Best Regadrs

Daniel

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[Craig Dowell]

> I am struggling with configuring a DropTailQueue of a certain size in
> a CsmaNetDevice, and would appreciate any help. I have tried different
> methods:
>
> 1- Config::SetDefault ("ns3::DropTailQueue::MaxPackets", UintegerValue
> (50));
> CsmaHelper csma;
> NetDeviceContainer devices = csma.Install (nodes);
>
> Expecting that by default a DropTailQueue of 50 packets would be
> installed in the devices. However, the previous does not work.

This works for me. Try doing

NS_LOG=DropTailQueue

and see what is printed with respect to queue occupancy. I took
examples/csma/csma-bridge.cc, added the line,

Config::SetDefault("ns3::DropTailQueue::MaxPackets", UintegerValue
(1));

and changed the datarate to 5 kbps to slow everything down

csma.SetChannelAttribute ("DataRate", DataRateValue (5000));

and got the expected drops.

> 2- I tried with the SetQueue method of the CsmaHelper class.
> CsmaHelper csma;
>
> csma.SetQueue(std::string("DropTailQueue"),std::string("MaxPackets"),IntegerValue(50));
> NetDeviceContainer devices = csma.Install (nodes);
>
> However, the previous does not work either, I get compilation errors
> complaining about an incorrect TypeID, basically I do not seem to be
> able to pass the correct parameters to the method SetQueue() and I
> have not found any example in the existing code.

I also tried the following code in csma-bridge.cc and got the same
expected results:

csma.SetQueue ("ns3::DropTailQueue", "MaxPackets", UintegerValue(1));

Note the parameter is a UintegerValue not an Integervalue.

> 3- I try to set the queues manually:
> NetDeviceContainer devices = csma.Install (nodes);
> Ptr<CsmaNetDevice> csma_device_aux = devices.Get(0)-
> >GetObject<CsmaNetDevice> ();
> csma_device_aux->SetQueue (CreateObject<DropTailQueue> ());
> Ptr<DropTailQueue> dtq = csma_device_aux->GetQueue()-
> >GetObject<DropTailQueue> ();
> dtq->SetAttribute("MaxPackets", UintegerValue (60));
>
> The previous does compile, but when I run my experiment I see that the
> queue is not yet limited to 50 packets. Actually, th experiment I run
> seems to have unbounded queues (?).

I tried to set the queue size manually (in a long one-liner):

link.Get (j)->GetObject<CsmaNetDevice> ()->GetQueue
()->GetObject<DropTailQueue> ()->SetAttribute ("MaxPackets", Uinteger\
Value (1));

And it works as expected.

> The way I capture the queue size is by tracing the Enqueue and Dequeue
> events defined in the Queue class:
> QueueMonitor QMon;
> Ptr<CsmaNetDevice> csma_device = devices.Get(0)-
> >GetObject<CsmaNetDevice> ();
> csma_device->GetQueue()->TraceConnectWithoutContext ("Enqueue",
> MakeCallback(&QueueMonitor::TraceEnqueue, &QMon));
> csma_device->GetQueue()->TraceConnectWithoutContext ("Dequeue",
> MakeCallback(&QueueMonitor::TraceDequeue, &QMon));
>
> It could also be that I am making a mistake there.

Pick any of the approaches you have above. I would then use
NS_LOG=DropTailQueue to watch the queue occupancy change directly:

xx.xxxs DropTailQueue:DoEnqueue(): Number packets 1

[Dani Camps]

Dear Craig,

Thanks again for your accurate response. I checked your method and it works, the problem must be related with my traces.

Best Regards

Daniel

Which would be the easiest way to trace the queue