diff -r 447453a55597 src/core/callback-trace-source.h
--- a/src/core/callback-trace-source.h	Fri Jan 11 12:58:21 2008 +0000
+++ b/src/core/callback-trace-source.h	Fri Jan 11 19:09:18 2008 +0000
@@ -23,12 +23,19 @@
 #define CALLBACK_TRACE_H
 
 #include <list>
+#include <typeinfo>
 #include "callback.h"
 #include "fatal-error.h"
 #include "trace-context.h"
 #include "trace-source.h"
 
 namespace ns3 {
+
+class CallbackTraceSourceBase : public TraceSource
+{
+public:
+  virtual const std::type_info& GetCallbackType () const = 0;
+};
 
 /**
  * \brief log arbitrary number of parameters to a matching ns3::Callback
@@ -39,12 +46,18 @@ namespace ns3 {
  */
 template<typename T1 = empty, typename T2 = empty, 
          typename T3 = empty, typename T4 = empty>
-class CallbackTraceSource : public TraceSource {
+class CallbackTraceSource : public CallbackTraceSourceBase {
 public:
+
+  typedef Callback<void,TraceContext const &,T1,T2,T3,T4> CallbackType;
+
   CallbackTraceSource ();
   virtual void AddCallback (CallbackBase const & callback, TraceContext const & context);
   virtual void RemoveCallback (CallbackBase const & callback);
   virtual void ConnectPrinter (std::ostream &os, const TraceContext &context);
+  virtual const std::type_info& GetCallbackType () const {
+    return typeid (CallbackType);
+  }
   void operator() (void) const;
   void operator() (T1 a1) const;
   void operator() (T1 a1, T2 a2) const;
@@ -52,7 +65,7 @@ public:
   void operator() (T1 a1, T2 a2, T3 a3, T4 a4) const;
 
 private:
-  typedef std::list<Callback<void,TraceContext const &,T1,T2,T3,T4> > CallbackList;
+  typedef std::list<CallbackType> CallbackList;
   TraceContext m_context;
   CallbackList m_callbackList;
 };
diff -r 447453a55597 src/core/composite-trace-resolver.cc
--- a/src/core/composite-trace-resolver.cc	Fri Jan 11 12:58:21 2008 +0000
+++ b/src/core/composite-trace-resolver.cc	Fri Jan 11 19:09:18 2008 +0000
@@ -105,7 +105,7 @@ CompositeTraceResolver::DoAddSource (std
       path.append (this->name);
       TraceContext ctx = context;
       ctx.Union (this->context);
-      collection->AddUnique (path, ctx, this->doc);
+      collection->AddUnique (path, ctx, this->doc, GetCallbackType ());
     }
     virtual void TraceAll (std::ostream &os, const TraceContext &context)
     {
@@ -115,6 +115,20 @@ CompositeTraceResolver::DoAddSource (std
     }
     TraceSource *trace;
     TraceDoc doc;
+
+    const std::type_info* GetCallbackType ()
+    {
+      const CallbackTraceSourceBase *callbackSource =
+        dynamic_cast<const CallbackTraceSourceBase *> (trace);
+      if (callbackSource == NULL)
+        {
+          return NULL;
+        }
+      else
+        {
+          return &callbackSource->GetCallbackType ();
+        }
+    }
   } *item = new SourceResolveItem ();
   item->name = name;
   item->context = context;
@@ -438,7 +452,7 @@ bool
 bool 
 CompositeTraceResolverTest::RunTests (void)
 {
-  bool ok = true;
+  bool result = true;
 
   CallbackTraceSource<double> traceDoubleA;
   CallbackTraceSource<double> traceDoubleB;
@@ -453,19 +467,37 @@ CompositeTraceResolverTest::RunTests (vo
 
   resolver.Connect ("/*", MakeCallback (&CompositeTraceResolverTest::TraceDouble, this), TraceContext ());
 
+  {
+    TraceResolver::SourceCollection collection;
+    resolver.CollectSources ("/*", context, &collection);
+
+    int numSources = 0;
+    for (TraceResolver::SourceCollection::Iterator source = collection.Begin ();
+         source != collection.End (); source++)
+      {
+        NS_TEST_ASSERT (source->callbackType != NULL);
+        if (source->callbackType != NULL)
+          {
+            numSources++;
+            NS_TEST_ASSERT (*source->callbackType == typeid (Callback<void, TraceContext const &, double>));
+          }
+      }
+    NS_TEST_ASSERT (numSources > 0);
+  }
+
   m_gotDoubleA = false;
   m_gotDoubleB = false;
   traceDoubleA (0);
   if (!m_gotDoubleA || m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
   m_gotDoubleA = false;
   traceDoubleA (0);
   traceDoubleB (0);
   if (!m_gotDoubleA || !m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
   m_gotDoubleA = false;
   m_gotDoubleB = false;
@@ -478,7 +510,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (m_gotDoubleA || m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
 
   resolver.Connect ("/trace-double-a", 
@@ -489,7 +521,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (!m_gotDoubleA || m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
   resolver.Disconnect ("/trace-double-a", 
 		       MakeCallback (&CompositeTraceResolverTest::TraceDouble, this));
@@ -502,7 +534,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (!m_gotDoubleA || m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
   resolver.Disconnect ("/trace-double-a", 
 		       MakeCallback (&CompositeTraceResolverTest::TraceDouble, this));
@@ -515,7 +547,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (!m_gotDoubleA || !m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
   resolver.Disconnect ("/trace-double-a", 
 		       MakeCallback (&CompositeTraceResolverTest::TraceDouble, this));
@@ -525,7 +557,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (m_gotDoubleA || !m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
 
 
@@ -537,7 +569,7 @@ CompositeTraceResolverTest::RunTests (vo
   traceDoubleB (0);
   if (m_gotDoubleA || m_gotDoubleB)
     {
-      ok = false;
+      result = false;
     }
 
   resolver.Add ("subresolver", 
@@ -549,7 +581,7 @@ CompositeTraceResolverTest::RunTests (vo
   m_traceInt (1);
   if (!m_gotInt)
     {
-      ok = false;
+      result = false;
     }
 
   resolver.Disconnect ("/subresolver/trace-int", 
@@ -558,7 +590,7 @@ CompositeTraceResolverTest::RunTests (vo
   m_traceInt (1);
   if (m_gotInt)
     {
-      ok = false;
+      result = false;
     }
 
   resolver.Connect ("/*/trace-int", 
@@ -567,7 +599,7 @@ CompositeTraceResolverTest::RunTests (vo
   m_traceInt (1);
   if (!m_gotInt)
     {
-      ok = false;
+      result = false;
     }
 
   resolver.Disconnect ("/subresolver/trace-int", 
@@ -576,7 +608,7 @@ CompositeTraceResolverTest::RunTests (vo
   m_traceInt (1);
   if (m_gotInt)
     {
-      ok = false;
+      result = false;
     }
 
   SVTraceSource<uint16_t> source;
@@ -584,7 +616,7 @@ CompositeTraceResolverTest::RunTests (vo
   resolver.AddSource ("uint16_t", TraceDoc ("test source"), source, TraceSourceTest (TraceSourceTest::UINT16_T));
   
 
-  return ok;
+  return result;
 }
 
 static CompositeTraceResolverTest g_compositeTraceResolverTest;
diff -r 447453a55597 src/core/trace-resolver.cc
--- a/src/core/trace-resolver.cc	Fri Jan 11 12:58:21 2008 +0000
+++ b/src/core/trace-resolver.cc	Fri Jan 11 19:09:18 2008 +0000
@@ -78,7 +78,8 @@ void
 void 
 TraceResolver::SourceCollection::AddUnique (std::string path, 
                                             const TraceContext &context,
-                                            const TraceDoc &doc)
+                                            const TraceDoc &doc,
+                                            const std::type_info *callbackType)
 {
   for (SourceVector::const_iterator i = m_sources.begin (); i != m_sources.end (); i++)
     {
@@ -92,6 +93,7 @@ TraceResolver::SourceCollection::AddUniq
   source.path = path;
   source.context = context;
   source.doc = doc;
+  source.callbackType = callbackType;
   m_sources.push_back (source);
 }
 TraceResolver::SourceCollection::Iterator
diff -r 447453a55597 src/core/trace-resolver.h
--- a/src/core/trace-resolver.h	Fri Jan 11 12:58:21 2008 +0000
+++ b/src/core/trace-resolver.h	Fri Jan 11 19:09:18 2008 +0000
@@ -23,6 +23,7 @@
 
 #include <string>
 #include <list>
+#include <typeinfo>
 #include "trace-context.h"
 #include "trace-doc.h"
 
@@ -93,11 +94,16 @@ public:
        * Document the signature of this trace source
        */
       TraceDoc doc;
+      /**
+       * Type info of the Callback, or NULL if it's not a callback source
+       */
+      const std::type_info *callbackType;
     };
     typedef std::vector<struct Source>::const_iterator Iterator;
     void AddUnique (std::string path, 
                     const TraceContext &context,
-                    const TraceDoc &doc);
+                    const TraceDoc &doc,
+                    const std::type_info *callbackType);
 
     /**
      * \returns an iterator which points to the first element of the set of