traffic-control: Allow to disable flow control for devices supporting it

src/csma/helper/csma-helper.cc

@@ -44,6 +44,7 @@ CsmaHelper::CsmaHelper ()
   m_queueFactory.SetTypeId ("ns3::DropTailQueue<Packet>");
   m_deviceFactory.SetTypeId ("ns3::CsmaNetDevice");
   m_channelFactory.SetTypeId ("ns3::CsmaChannel");
+  m_enableFlowControl = true;
 }
 
 void 
@@ -74,6 +75,12 @@ CsmaHelper::SetChannelAttribute (std::string n1, const AttributeValue &v1)
   m_channelFactory.Set (n1, v1);
 }
 
+void
+CsmaHelper::DisableFlowControl (void)
+{
+  m_enableFlowControl = false;
+}
+
 void 
 CsmaHelper::EnablePcapInternal (std::string prefix, Ptr<NetDevice> nd, bool promiscuous, bool explicitFilename)
 {
@@ -310,11 +317,13 @@ CsmaHelper::InstallPriv (Ptr<Node> node, Ptr<CsmaChannel> channel) const
   Ptr<Queue<Packet> > queue = m_queueFactory.Create<Queue<Packet> > ();
   device->SetQueue (queue);
   device->Attach (channel);
-  // Aggregate a NetDeviceQueueInterface object
-  Ptr<NetDeviceQueueInterface> ndqi = CreateObject<NetDeviceQueueInterface> ();
-  ndqi->GetTxQueue (0)->ConnectQueueTraces (queue);
-  device->AggregateObject (ndqi);
-
+  if (m_enableFlowControl)
+    {
+      // Aggregate a NetDeviceQueueInterface object
+      Ptr<NetDeviceQueueInterface> ndqi = CreateObject<NetDeviceQueueInterface> ();
+      ndqi->GetTxQueue (0)->ConnectQueueTraces (queue);
+      device->AggregateObject (ndqi);
+    }
   return device;
 }
 

src/csma/helper/csma-helper.h

@@ -90,6 +90,16 @@ public:
    */
   void SetChannelAttribute (std::string n1, const AttributeValue &v1);
 
+  /**
+   * Disable flow control only if you know what you are doing. By disabling
+   * flow control, this NetDevice will be sent packets even if there is no
+   * room for them (such packets will be likely dropped by this NetDevice).
+   * Also, any queue disc installed on this NetDevice will have no effect,
+   * as every packet enqueued to the traffic control layer queue disc will
+   * be immediately dequeued.
+   */
+  void DisableFlowControl (void);
+
   /**
    * This method creates an ns3::CsmaChannel with the attributes configured by
    * CsmaHelper::SetChannelAttribute, an ns3::CsmaNetDevice with the attributes
@@ -250,6 +260,7 @@ private:
   ObjectFactory m_queueFactory;   //!< factory for the queues
   ObjectFactory m_deviceFactory;  //!< factory for the NetDevices
   ObjectFactory m_channelFactory; //!< factory for the channel
+  bool m_enableFlowControl;       //!< whether to enable flow control
 };
 
 } // namespace ns3

src/network/helper/simple-net-device-helper.cc

@@ -46,6 +46,7 @@ SimpleNetDeviceHelper::SimpleNetDeviceHelper ()
   m_deviceFactory.SetTypeId ("ns3::SimpleNetDevice");
   m_channelFactory.SetTypeId ("ns3::SimpleChannel");
   m_pointToPointMode = false;
+  m_enableFlowControl = true;
 }
 
 void 
@@ -96,6 +97,12 @@ SimpleNetDeviceHelper::SetNetDevicePointToPointMode (bool pointToPointMode)
   m_pointToPointMode = pointToPointMode;
 }
 
+void
+SimpleNetDeviceHelper::DisableFlowControl (void)
+{
+  m_enableFlowControl = false;
+}
+
 NetDeviceContainer
 SimpleNetDeviceHelper::Install (Ptr<Node> node) const
 {
@@ -141,10 +148,13 @@ SimpleNetDeviceHelper::InstallPriv (Ptr<Node> node, Ptr<SimpleChannel> channel)
   Ptr<Queue<Packet> > queue = m_queueFactory.Create<Queue<Packet> > ();
   device->SetQueue (queue);
   NS_ASSERT_MSG (!m_pointToPointMode || (channel->GetNDevices () <= 2), "Device set to PointToPoint and more than 2 devices on the channel.");
-  // Aggregate a NetDeviceQueueInterface object
-  Ptr<NetDeviceQueueInterface> ndqi = CreateObject<NetDeviceQueueInterface> ();
-  ndqi->GetTxQueue (0)->ConnectQueueTraces (queue);
-  device->AggregateObject (ndqi);
+  if (m_enableFlowControl)
+    {
+      // Aggregate a NetDeviceQueueInterface object
+      Ptr<NetDeviceQueueInterface> ndqi = CreateObject<NetDeviceQueueInterface> ();
+      ndqi->GetTxQueue (0)->ConnectQueueTraces (queue);
+      device->AggregateObject (ndqi);
+    }
   return device;
 }
 

src/network/helper/simple-net-device-helper.h

@@ -120,6 +120,16 @@ public:
    */
   void SetNetDevicePointToPointMode (bool pointToPointMode);
 
+  /**
+   * Disable flow control only if you know what you are doing. By disabling
+   * flow control, this NetDevice will be sent packets even if there is no
+   * room for them (such packets will be likely dropped by this NetDevice).
+   * Also, any queue disc installed on this NetDevice will have no effect,
+   * as every packet enqueued to the traffic control layer queue disc will
+   * be immediately dequeued.
+   */
+  void DisableFlowControl (void);
+
   /**
    * This method creates an ns3::SimpleChannel with the attributes configured by
    * SimpleNetDeviceHelper::SetChannelAttribute, an ns3::SimpleNetDevice with the attributes
@@ -182,7 +192,7 @@ private:
   ObjectFactory m_deviceFactory; //!< NetDevice factory
   ObjectFactory m_channelFactory; //!< Channel factory
   bool m_pointToPointMode; //!< Install PointToPoint SimpleNetDevice or Broadcast ones
-
+  bool m_enableFlowControl; //!< whether to enable flow control
 };
 
 } // namespace ns3

src/point-to-point/helper/point-to-point-helper.cc

@@ -47,6 +47,7 @@ PointToPointHelper::PointToPointHelper ()
   m_queueFactory.SetTypeId ("ns3::DropTailQueue<Packet>");
   m_deviceFactory.SetTypeId ("ns3::PointToPointNetDevice");
   m_channelFactory.SetTypeId ("ns3::PointToPointChannel");
+  m_enableFlowControl = true;
 }
 
 void 
@@ -77,6 +78,12 @@ PointToPointHelper::SetChannelAttribute (std::string n1, const AttributeValue &v
   m_channelFactory.Set (n1, v1);
 }
 
+void
+PointToPointHelper::DisableFlowControl (void)
+{
+  m_enableFlowControl = false;
+}
+
 void 
 PointToPointHelper::EnablePcapInternal (std::string prefix, Ptr<NetDevice> nd, bool promiscuous, bool explicitFilename)
 {
@@ -240,13 +247,16 @@ PointToPointHelper::Install (Ptr<Node> a, Ptr<Node> b)
   b->AddDevice (devB);
   Ptr<Queue<Packet> > queueB = m_queueFactory.Create<Queue<Packet> > ();
   devB->SetQueue (queueB);
-  // Aggregate NetDeviceQueueInterface objects
-  Ptr<NetDeviceQueueInterface> ndqiA = CreateObject<NetDeviceQueueInterface> ();
-  ndqiA->GetTxQueue (0)->ConnectQueueTraces (queueA);
-  devA->AggregateObject (ndqiA);
-  Ptr<NetDeviceQueueInterface> ndqiB = CreateObject<NetDeviceQueueInterface> ();
-  ndqiB->GetTxQueue (0)->ConnectQueueTraces (queueB);
-  devB->AggregateObject (ndqiB);
+  if (m_enableFlowControl)
+    {
+      // Aggregate NetDeviceQueueInterface objects
+      Ptr<NetDeviceQueueInterface> ndqiA = CreateObject<NetDeviceQueueInterface> ();
+      ndqiA->GetTxQueue (0)->ConnectQueueTraces (queueA);
+      devA->AggregateObject (ndqiA);
+      Ptr<NetDeviceQueueInterface> ndqiB = CreateObject<NetDeviceQueueInterface> ();
+      ndqiB->GetTxQueue (0)->ConnectQueueTraces (queueB);
+      devB->AggregateObject (ndqiB);
+    }
 
   Ptr<PointToPointChannel> channel = 0;
 

src/point-to-point/helper/point-to-point-helper.h

@@ -99,6 +99,16 @@ public:
    */
   void SetChannelAttribute (std::string name, const AttributeValue &value);
 
+  /**
+   * Disable flow control only if you know what you are doing. By disabling
+   * flow control, this NetDevice will be sent packets even if there is no
+   * room for them (such packets will be likely dropped by this NetDevice).
+   * Also, any queue disc installed on this NetDevice will have no effect,
+   * as every packet enqueued to the traffic control layer queue disc will
+   * be immediately dequeued.
+   */
+  void DisableFlowControl (void);
+
   /**
    * \param c a set of nodes
    * \return a NetDeviceContainer for nodes
@@ -184,6 +194,7 @@ private:
   ObjectFactory m_queueFactory;         //!< Queue Factory
   ObjectFactory m_channelFactory;       //!< Channel Factory
   ObjectFactory m_deviceFactory;        //!< Device Factory
+  bool m_enableFlowControl;             //!< whether to enable flow control
 };
 
 } // namespace ns3

src/traffic-control/doc/queue-discs.rst

@@ -187,6 +187,20 @@ Uninstall method of the TrafficControlHelper C++ class, and then installing a di
 queue disc on the device.  By uninstalling without adding a new queue disc, it is also possible
 to have no queue disc installed on a device.
 
+Note that if no queue disc is installed on an underlying device, the traffic
+control layer will still respect flow control signals provided by the device, if
+any.  Specifically, if no queue disc is installed on a device, and the device is
+stopped, then any packet for that device will be dropped in the traffic control
+layer, and the device's drop trace will not record the drop -- instead, the TcDrop
+drop trace in the traffic control layer will record the drop.
+
+Flow control can be disabled for the devices that support it by using the
+``DisableFlowControl`` method of their helpers.  If there is no queue disc
+installed on the device, and the device is not performing flow control, then
+packets will immediately transit the traffic control layer and be sent to the
+device, regardless or not of whether the device's internal queue can accept it,
+and the traffic control layer's TcDrop trace will not be called.
+
 Helpers
 =======
 

src/traffic-control/helper/traffic-control-helper.h

@@ -273,6 +273,12 @@ public:
    *
    * This method removes the root queue discs (and associated filters, classes
    * and queues) installed on the given devices.
+   * Note that the traffic control layer will continue to perform flow control
+   * if the device has an aggregated NetDeviceQueueInterface. If you really
+   * want that the Traffic Control layer forwards packets down to the NetDevice
+   * even if there is no room for them in the NetDevice queue(s), then disable
+   * the flow control by using the DisableFlowControl method of the NetDevice
+   * helper.
    */
   void Uninstall (NetDeviceContainer c);
 
@@ -281,6 +287,12 @@ public:
    *
    * This method removes the root queue disc (and associated filters, classes
    * and queues) installed on the given device.
+   * Note that the traffic control layer will continue to perform flow control
+   * if the device has an aggregated NetDeviceQueueInterface. If you really
+   * want that the Traffic Control layer forwards packets down to the NetDevice
+   * even if there is no room for them in the NetDevice queue(s), then disable
+   * the flow control by using the DisableFlowControl method of the NetDevice
+   * helper.
    */
   void Uninstall (Ptr<NetDevice> d);
 

src/wifi/helper/wifi-helper.cc

@@ -712,7 +712,8 @@ WifiHelper::~WifiHelper ()
 
 WifiHelper::WifiHelper ()
   : m_standard (WIFI_STANDARD_80211a),
-    m_selectQueueCallback (&SelectQueueByDSField)
+    m_selectQueueCallback (&SelectQueueByDSField),
+    m_enableFlowControl (true)
 {
   SetRemoteStationManager ("ns3::ArfWifiManager");
 }
@@ -769,6 +770,12 @@ WifiHelper::SetStandard (WifiStandard standard)
   m_standard = standard;
 }
 
+void
+WifiHelper::DisableFlowControl (void)
+{
+  m_enableFlowControl = false;
+}
+
 void
 WifiHelper::SetSelectQueueCallback (SelectQueueCallback f)
 {
@@ -825,7 +832,7 @@ WifiHelper::Install (const WifiPhyHelper &phyHelper,
       NS_LOG_DEBUG ("node=" << node << ", mob=" << node->GetObject<MobilityModel> ());
       // Aggregate a NetDeviceQueueInterface object if a RegularWifiMac is installed
       Ptr<RegularWifiMac> rmac = DynamicCast<RegularWifiMac> (mac);
-      if (rmac)
+      if (rmac && m_enableFlowControl)
         {
           Ptr<NetDeviceQueueInterface> ndqi;
           BooleanValue qosSupported;

src/wifi/helper/wifi-helper.h

@@ -408,6 +408,17 @@ public:
    * to the WifiNetDevice, in case RegularWifiMac with QoS enabled is used
    */
   void SetSelectQueueCallback (SelectQueueCallback f);
+
+  /**
+   * Disable flow control only if you know what you are doing. By disabling
+   * flow control, this NetDevice will be sent packets even if there is no
+   * room for them (such packets will be likely dropped by this NetDevice).
+   * Also, any queue disc installed on this NetDevice will have no effect,
+   * as every packet enqueued to the traffic control layer queue disc will
+   * be immediately dequeued.
+   */
+  void DisableFlowControl (void);
+
   /**
    * \param phy the PHY helper to create PHY objects
    * \param mac the MAC helper to create MAC objects
@@ -498,6 +509,7 @@ protected:
   WifiStandard m_standard;                   ///< wifi standard
   SelectQueueCallback m_selectQueueCallback; ///< select queue callback
   ObjectFactory m_obssPdAlgorithm;           ///< OBSS_PD algorithm
+  bool m_enableFlowControl;                  //!< whether to enable flow control
 };
 
 } //namespace ns3