diff -r 01d2fe958492 src/contrib/flow-monitor/ipv4-flow-probe.cc
--- a/src/contrib/flow-monitor/ipv4-flow-probe.cc	Mon Apr 26 15:11:39 2010 +0800
+++ b/src/contrib/flow-monitor/ipv4-flow-probe.cc	Mon Apr 26 15:14:40 2010 +0800
@@ -27,7 +27,6 @@
 #include "ns3/pointer.h"
 #include "ns3/config.h"
 #include "ns3/flow-id-tag.h"
-#include <sstream>
 
 namespace ns3 {
 
@@ -36,10 +35,10 @@
 NS_LOG_COMPONENT_DEFINE ("Ipv4FlowProbe");
 
             //////////////////////////////////////
-            // FlowProbeTag class implementation //
+            // Ipv4FlowProbeTag class implementation //
             //////////////////////////////////////
 
-class FlowProbeTag : public Tag
+class Ipv4FlowProbeTag : public Tag
 {
 public:
   static TypeId GetTypeId (void);
@@ -48,8 +47,8 @@
   virtual void Serialize (TagBuffer buf) const;
   virtual void Deserialize (TagBuffer buf);
   virtual void Print (std::ostream &os) const;
-  FlowProbeTag ();
-  FlowProbeTag (uint32_t flowId, uint32_t packetId, uint32_t packetSize);
+  Ipv4FlowProbeTag ();
+  Ipv4FlowProbeTag (uint32_t flowId, uint32_t packetId, uint32_t packetSize);
   void SetFlowId (uint32_t flowId);
   void SetPacketId (uint32_t packetId);
   void SetPacketSize (uint32_t packetSize);
@@ -64,80 +63,80 @@
 };
 
 TypeId 
-FlowProbeTag::GetTypeId (void)
+Ipv4FlowProbeTag::GetTypeId (void)
 {
-  static TypeId tid = TypeId ("ns3::FlowProbeTag")
+  static TypeId tid = TypeId ("ns3::Ipv4FlowProbeTag")
     .SetParent<Tag> ()
-    .AddConstructor<FlowProbeTag> ()
+    .AddConstructor<Ipv4FlowProbeTag> ()
     ;
   return tid;
 }
 TypeId 
-FlowProbeTag::GetInstanceTypeId (void) const
+Ipv4FlowProbeTag::GetInstanceTypeId (void) const
 {
   return GetTypeId ();
 }
 uint32_t 
-FlowProbeTag::GetSerializedSize (void) const
+Ipv4FlowProbeTag::GetSerializedSize (void) const
 {
   return 4 + 4 + 4;
 }
 void 
-FlowProbeTag::Serialize (TagBuffer buf) const
+Ipv4FlowProbeTag::Serialize (TagBuffer buf) const
 {
   buf.WriteU32 (m_flowId);
   buf.WriteU32 (m_packetId);
   buf.WriteU32 (m_packetSize);
 }
 void 
-FlowProbeTag::Deserialize (TagBuffer buf)
+Ipv4FlowProbeTag::Deserialize (TagBuffer buf)
 {
   m_flowId = buf.ReadU32 ();
   m_packetId = buf.ReadU32 ();
   m_packetSize = buf.ReadU32 ();
 }
 void 
-FlowProbeTag::Print (std::ostream &os) const
+Ipv4FlowProbeTag::Print (std::ostream &os) const
 {
   os << "FlowId=" << m_flowId;
   os << "PacketId=" << m_packetId;
   os << "PacketSize=" << m_packetSize;
 }
-FlowProbeTag::FlowProbeTag ()
+Ipv4FlowProbeTag::Ipv4FlowProbeTag ()
   : Tag () 
 {}
 
-FlowProbeTag::FlowProbeTag (uint32_t flowId, uint32_t packetId, uint32_t packetSize)
+Ipv4FlowProbeTag::Ipv4FlowProbeTag (uint32_t flowId, uint32_t packetId, uint32_t packetSize)
   : Tag (), m_flowId (flowId), m_packetId (packetId), m_packetSize (packetSize)
 {}
 
 void
-FlowProbeTag::SetFlowId (uint32_t id)
+Ipv4FlowProbeTag::SetFlowId (uint32_t id)
 {
   m_flowId = id;
 }
 void
-FlowProbeTag::SetPacketId (uint32_t id)
+Ipv4FlowProbeTag::SetPacketId (uint32_t id)
 {
   m_packetId = id;
 }
 void
-FlowProbeTag::SetPacketSize (uint32_t size)
+Ipv4FlowProbeTag::SetPacketSize (uint32_t size)
 {
   m_packetSize = size;
 }
 uint32_t
-FlowProbeTag::GetFlowId (void) const
+Ipv4FlowProbeTag::GetFlowId (void) const
 {
   return m_flowId;
 }  
 uint32_t
-FlowProbeTag::GetPacketId (void) const
+Ipv4FlowProbeTag::GetPacketId (void) const
 {
   return m_packetId;
 } 
 uint32_t
-FlowProbeTag::GetPacketSize (void) const
+Ipv4FlowProbeTag::GetPacketSize (void) const
 {
   return m_packetSize;
 } 
@@ -199,7 +240,8 @@
 
       // tag the packet with the flow id and packet id, so that the packet can be identified even
       // when Ipv4Header is not accessible at some non-IPv4 protocol layer
-      FlowProbeTag fTag (flowId, packetId, size);
+      Ipv4FlowProbeTag fTag (flowId, packetId, size);
+      NS_ASSERT_MSG (!ConstCast<Packet> (ipPayload)->RemovePacketTag (fTag), "There alrady exists a FlowProbeTag with the packet " << *ipPayload << " Uid=" << ipPayload->GetUid ());
       ipPayload->AddPacketTag (fTag);
     }
 }
@@ -228,9 +270,9 @@
   if (m_classifier->Classify (ipHeader, ipPayload, &flowId, &packetId))
     {
       // remove the tags that are added by Ipv4FlowProbe::SendOutgoingLogger ()
-      FlowProbeTag fTag;
+      Ipv4FlowProbeTag fTag;
       bool tagFound = ConstCast<Packet> (ipPayload)->RemovePacketTag (fTag);
-      NS_ASSERT_MSG (tagFound, "FlowProbeTag is missing");
+      NS_ASSERT_MSG (tagFound, "Ipv4FlowProbeTag is missing");
 
       uint32_t size = (ipPayload->GetSize () + ipHeader.GetSerializedSize ());
       NS_LOG_DEBUG ("ReportLastRx ("<<this<<", "<<flowId<<", "<<packetId<<", "<<size<<");");
@@ -266,9 +308,9 @@
   if (m_classifier->Classify (ipHeader, ipPayload, &flowId, &packetId))
     {
       // remove the tags that are added by Ipv4FlowProbe::SendOutgoingLogger ()
-      FlowProbeTag fTag;
+      Ipv4FlowProbeTag fTag;
       bool tagFound = ConstCast<Packet> (ipPayload)->RemovePacketTag (fTag);
-      NS_ASSERT_MSG (tagFound, "FlowProbeTag is missing");
+      NS_ASSERT_MSG (tagFound, "Ipv4FlowProbeTag is missing");
 
       uint32_t size = (ipPayload->GetSize () + ipHeader.GetSerializedSize ());
       NS_LOG_DEBUG ("Drop ("<<this<<", "<<flowId<<", "<<packetId<<", "<<size<<", " << reason 
@@ -305,8 +347,9 @@
 Ipv4FlowProbe::QueueDropLogger (Ptr<const Packet> ipPayload)
 {
   // remove the tags that are added by Ipv4FlowProbe::SendOutgoingLogger ()
-  FlowProbeTag fTag;
+  Ipv4FlowProbeTag fTag;
   bool tagFound = ConstCast<Packet> (ipPayload)->RemovePacketTag (fTag);
+  NS_ASSERT_MSG (tagFound, "FlowProbeTag is missing");
   
   if (tagFound)
   {