diff --git a/src/node/application.cc b/src/node/application.cc
index 4cdb8d6fa..ce98cb5ae 100644
--- a/src/node/application.cc
+++ b/src/node/application.cc
@@ -37,8 +37,10 @@ namespace ns3 {
 // Application Methods
 
 // \brief Application Constructor
-  Application::Application(const Node& n) : m_startVar(nil), m_stopVar(nil),
-                               m_start(false), m_stop(false)
+  Application::Application(const Node& n) 
+    : m_node (0),
+      m_startVar(nil), m_stopVar(nil),
+      m_start(false), m_stop(false)
 {
   SetNode(n);
 }
diff --git a/src/node/arp-cache.cc b/src/node/arp-cache.cc
index d1d477b5c..6a6f71bc9 100644
--- a/src/node/arp-cache.cc
+++ b/src/node/arp-cache.cc
@@ -34,15 +34,18 @@ ArpCache::ArpCache (NetDevice *device, Ipv4Interface *interface)
     m_aliveTimeout (Seconds (120)),
     m_deadTimeout (Seconds (100)),
     m_waitReplyTimeout (Seconds (1))
-{}
+{
+  m_device->Ref ();
+}
 
 ArpCache::~ArpCache ()
 {
+  m_device->Unref ();
   Flush ();
 }
 
 NetDevice *
-ArpCache::GetDevice (void) const
+ArpCache::PeekDevice (void) const
 {
   return m_device;
 }
diff --git a/src/node/arp-cache.h b/src/node/arp-cache.h
index f71e9ce9a..ddee3b840 100644
--- a/src/node/arp-cache.h
+++ b/src/node/arp-cache.h
@@ -24,6 +24,7 @@
 #include <stdint.h>
 #include "ns3/packet.h"
 #include "ns3/nstime.h"
+#include "net-device.h"
 #include "ipv4-address.h"
 #include "mac-address.h"
 #include "sgi-hashmap.h"
@@ -40,7 +41,7 @@ public:
   ArpCache (NetDevice *device, Ipv4Interface *interface);
   ~ArpCache ();
 
-  NetDevice *GetDevice (void) const;
+  NetDevice *PeekDevice (void) const;
   Ipv4Interface *GetInterface (void) const;
 
   void SetAliveTimeout (Time aliveTimeout);
diff --git a/src/node/arp-ipv4-interface.cc b/src/node/arp-ipv4-interface.cc
index 00e8554e6..9c7ce8215 100644
--- a/src/node/arp-ipv4-interface.cc
+++ b/src/node/arp-ipv4-interface.cc
@@ -42,10 +42,10 @@ TraceResolver *
 ArpIpv4Interface::DoCreateTraceResolver (TraceContext const &context)
 {
   CompositeTraceResolver *resolver = new CompositeTraceResolver (context);
-  if (GetDevice () != 0)
+  if (PeekDevice () != 0)
     {
       resolver->Add ("netdevice",
-                     MakeCallback (&NetDevice::CreateTraceResolver, GetDevice ()),
+                     MakeCallback (&NetDevice::CreateTraceResolver, PeekDevice ()),
                      ArpIpv4Interface::NETDEVICE);
     }
   
@@ -55,20 +55,20 @@ ArpIpv4Interface::DoCreateTraceResolver (TraceContext const &context)
 void 
 ArpIpv4Interface::SendTo (Packet p, Ipv4Address dest)
 {
-  NS_ASSERT (GetDevice () != 0);
-  if (GetDevice ()->NeedsArp ())
+  NS_ASSERT (PeekDevice () != 0);
+  if (PeekDevice ()->NeedsArp ())
     {
       Arp * arp = m_node->GetArp ();
       MacAddress hardwareDestination;
-      bool found = arp->Lookup (p, dest, GetDevice (), &hardwareDestination);
+      bool found = arp->Lookup (p, dest, PeekDevice (), &hardwareDestination);
       if (found)
         {
-          GetDevice ()->Send (p, hardwareDestination, Ipv4::PROT_NUMBER);
+          PeekDevice ()->Send (p, hardwareDestination, Ipv4::PROT_NUMBER);
         }
     }
   else
     {
-      GetDevice ()->Send (p, GetDevice ()->GetBroadcast (), Ipv4::PROT_NUMBER);
+      PeekDevice ()->Send (p, PeekDevice ()->GetBroadcast (), Ipv4::PROT_NUMBER);
     }
 }
 
diff --git a/src/node/arp.cc b/src/node/arp.cc
index 3f4c50c06..c3918fafb 100644
--- a/src/node/arp.cc
+++ b/src/node/arp.cc
@@ -65,7 +65,7 @@ Arp::FindCache (NetDevice *device)
 {
   for (CacheList::const_iterator i = m_cacheList.begin (); i != m_cacheList.end (); i++)
     {
-      if ((*i)->GetDevice () == device)
+      if ((*i)->PeekDevice () == device)
 	{
 	  return *i;
 	}
@@ -79,9 +79,9 @@ Arp::FindCache (NetDevice *device)
 }
 
 void 
-Arp::Receive(Packet& packet, NetDevice &device)
+Arp::Receive(Packet& packet, NetDevice *device)
 {
-  ArpCache *cache = FindCache (&device);
+  ArpCache *cache = FindCache (device);
   ArpHeader arp;
   packet.RemoveHeader (arp);
   if (arp.IsRequest () && 
@@ -94,7 +94,7 @@ Arp::Receive(Packet& packet, NetDevice &device)
     } 
   else if (arp.IsReply () &&
            arp.GetDestinationIpv4Address ().IsEqual (cache->GetInterface ()->GetAddress ()) &&
-           arp.GetDestinationHardwareAddress ().IsEqual (device.GetAddress ())) 
+           arp.GetDestinationHardwareAddress ().IsEqual (device->GetAddress ())) 
     {
       Ipv4Address from = arp.GetSourceIpv4Address ();
       ArpCache::Entry *entry = cache->Lookup (from);
@@ -200,25 +200,25 @@ void
 Arp::SendArpRequest (ArpCache const *cache, Ipv4Address to)
 {
   ArpHeader arp;
-  arp.SetRequest (cache->GetDevice ()->GetAddress (),
+  arp.SetRequest (cache->PeekDevice ()->GetAddress (),
 		  cache->GetInterface ()->GetAddress (), 
-                  cache->GetDevice ()->GetBroadcast (),
+                  cache->PeekDevice ()->GetBroadcast (),
                   to);
   Packet packet;
   packet.AddHeader (arp);
-  cache->GetDevice ()->Send (packet, cache->GetDevice ()->GetBroadcast (), PROT_NUMBER);
+  cache->PeekDevice ()->Send (packet, cache->PeekDevice ()->GetBroadcast (), PROT_NUMBER);
 }
 
 void
 Arp::SendArpReply (ArpCache const *cache, Ipv4Address toIp, MacAddress toMac)
 {
   ArpHeader arp;
-  arp.SetReply (cache->GetDevice ()->GetAddress (),
+  arp.SetReply (cache->PeekDevice ()->GetAddress (),
                 cache->GetInterface ()->GetAddress (),
                 toMac, toIp);
   Packet packet;
   packet.AddHeader (arp);
-  cache->GetDevice ()->Send (packet, toMac, PROT_NUMBER);
+  cache->PeekDevice ()->Send (packet, toMac, PROT_NUMBER);
 }
 
 }//namespace ns3
diff --git a/src/node/arp.h b/src/node/arp.h
index c940de43f..80aa68623 100644
--- a/src/node/arp.h
+++ b/src/node/arp.h
@@ -46,7 +46,7 @@ public:
 
   virtual TraceResolver *CreateTraceResolver (TraceContext const &context);
 
-  virtual void Receive(Packet& p, NetDevice &device);
+  virtual void Receive(Packet& p, NetDevice *device);
   bool Lookup (Packet &p, Ipv4Address destination, 
 	       NetDevice *device,
 	       MacAddress *hardwareDestination);
diff --git a/src/node/internet-node.cc b/src/node/internet-node.cc
index 1f58a35cd..af6adfcff 100644
--- a/src/node/internet-node.cc
+++ b/src/node/internet-node.cc
@@ -160,7 +160,7 @@ InternetNode::ReceiveFromDevice (NetDevice *device, const Packet &p, uint16_t pr
   if (target != 0) 
     {
       Packet packet = p;
-      target->Receive(packet, *device);
+      target->Receive(packet, device);
       return true;
     }
   return false;
diff --git a/src/node/ipv4-interface.cc b/src/node/ipv4-interface.cc
index 98311a2ae..6fc5aacbe 100644
--- a/src/node/ipv4-interface.cc
+++ b/src/node/ipv4-interface.cc
@@ -34,13 +34,23 @@ namespace ns3 {
 Ipv4Interface::Ipv4Interface (NetDevice *nd) 
   : m_netdevice (nd), 
     m_ifup(false)
-{}
+{
+  if (m_netdevice != 0)
+    {
+      m_netdevice->Ref ();
+    }
+}
 
 Ipv4Interface::~Ipv4Interface ()
-{}
+{
+  if (m_netdevice != 0)
+    {
+      m_netdevice->Unref ();
+    }
+}
 
 NetDevice*
-Ipv4Interface::GetDevice (void) const
+Ipv4Interface::PeekDevice (void) const
 {
   return m_netdevice;
 }
diff --git a/src/node/ipv4-interface.h b/src/node/ipv4-interface.h
index 173fc0f69..31948f247 100644
--- a/src/node/ipv4-interface.h
+++ b/src/node/ipv4-interface.h
@@ -87,7 +87,7 @@ public:
    * \returns the underlying NetDevice. This method can return
    *          zero if this interface has no associated NetDevice.
    */
-  NetDevice *GetDevice (void) const;
+  NetDevice *PeekDevice (void) const;
 
   /**
    * \param a set the ipv4 address of this interface.
diff --git a/src/node/ipv4-loopback-interface.cc b/src/node/ipv4-loopback-interface.cc
index 3700e6178..6c0ec5f53 100644
--- a/src/node/ipv4-loopback-interface.cc
+++ b/src/node/ipv4-loopback-interface.cc
@@ -33,9 +33,7 @@ Ipv4LoopbackInterface::Ipv4LoopbackInterface (Node *node)
 {
 }
 Ipv4LoopbackInterface::~Ipv4LoopbackInterface ()
-{
-  delete GetDevice ();
-}
+{}
 
 Node *
 Ipv4LoopbackInterface::GetNode (void) const
@@ -52,7 +50,7 @@ Ipv4LoopbackInterface::DoCreateTraceResolver (TraceContext const &context)
 void 
 Ipv4LoopbackInterface::SendTo (Packet packet, Ipv4Address dest)
 {
-  m_node->GetIpv4 ()->Receive (packet, *(this->GetDevice ()));
+  m_node->GetIpv4 ()->Receive (packet, PeekDevice ());
 }
 
 }//namespace ns3
diff --git a/src/node/ipv4.cc b/src/node/ipv4.cc
index 05d22e96b..8b8c2516b 100644
--- a/src/node/ipv4.cc
+++ b/src/node/ipv4.cc
@@ -338,7 +338,7 @@ Ipv4::FindInterfaceForDevice (NetDevice const*device)
 {
   for (Ipv4InterfaceList::const_iterator i = m_interfaces.begin (); i != m_interfaces.end (); i++)
     {
-      if ((*i)->GetDevice () == device)
+      if ((*i)->PeekDevice () == device)
         {
           return *i;
         }
@@ -354,12 +354,12 @@ Ipv4::Copy(Node *node) const
   return ipv4;
 }
 void 
-Ipv4::Receive(Packet& packet, NetDevice &device)
+Ipv4::Receive(Packet& packet, NetDevice *device)
 {
   uint32_t index = 0;
   for (Ipv4InterfaceList::const_iterator i = m_interfaces.begin (); i != m_interfaces.end (); i++)
     {
-      if ((*i)->GetDevice () == &device)
+      if ((*i)->PeekDevice () == device)
         {
           m_rxTrace (packet, index);
           break;
@@ -439,7 +439,7 @@ Ipv4::SendRealOut (Packet const &p, Ipv4Header const &ip, Ipv4Route const &route
 
 
 bool
-Ipv4::Forwarding (Packet const &packet, Ipv4Header &ipHeader, NetDevice &device)
+Ipv4::Forwarding (Packet const &packet, Ipv4Header &ipHeader, NetDevice *device)
 {
   for (Ipv4InterfaceList::const_iterator i = m_interfaces.begin ();
        i != m_interfaces.end (); i++) 
@@ -455,7 +455,7 @@ Ipv4::Forwarding (Packet const &packet, Ipv4Header &ipHeader, NetDevice &device)
        i != m_interfaces.end (); i++) 
     {
       Ipv4Interface *interface = *i;
-      if (interface->GetDevice () == &device)
+      if (interface->PeekDevice () == device)
 	{
 	  if (ipHeader.GetDestination ().IsEqual (interface->GetBroadcast ())) 
 	    {
diff --git a/src/node/ipv4.h b/src/node/ipv4.h
index d0c52d694..cda60fa64 100644
--- a/src/node/ipv4.h
+++ b/src/node/ipv4.h
@@ -193,7 +193,7 @@ public:
    *    - implement a per-NetDevice ARP cache
    *    - send back arp replies on the right device
    */
-  virtual void Receive(Packet& p, NetDevice &device);
+  virtual void Receive(Packet& p, NetDevice *device);
 
   /**
    * \param packet packet to send
@@ -219,7 +219,7 @@ public:
 
  private:
   void SendRealOut (Packet const &packet, Ipv4Header const &ip, Ipv4Route const &route);
-  bool Forwarding (Packet const &packet, Ipv4Header &ipHeader, NetDevice &device);
+  bool Forwarding (Packet const &packet, Ipv4Header &ipHeader, NetDevice *device);
   void ForwardUp (Packet p, Ipv4Header const&ip);
   uint32_t AddIpv4Interface (Ipv4Interface *interface);
   void SetupLoopback (void);
diff --git a/src/node/l3-protocol.h b/src/node/l3-protocol.h
index 59b41e8f2..2d690792f 100644
--- a/src/node/l3-protocol.h
+++ b/src/node/l3-protocol.h
@@ -54,7 +54,7 @@ public:
    *    - implement a per-NetDevice ARP cache
    *    - send back arp replies on the right device
    */
-  virtual void Receive(Packet& p, NetDevice &device) = 0;
+  virtual void Receive(Packet& p, NetDevice *device) = 0;
 
  private:
   int m_protocolNumber;
diff --git a/src/node/node.cc b/src/node/node.cc
index 35170df38..a85fbc714 100644
--- a/src/node/node.cc
+++ b/src/node/node.cc
@@ -72,6 +72,7 @@ Node::SetSystemId(uint32_t s )
 uint32_t 
 Node::AddDevice (NetDevice *device)
 {
+  device->Ref ();
   uint32_t index = m_devices.size ();
   m_devices.push_back (device);
   DoAddDevice (device);