diff --git a/utils/detail/multi-policy-container.h b/utils/detail/multi-policy-container.h
index 9fcc061..0fa07b3 100644
--- a/utils/detail/multi-policy-container.h
+++ b/utils/detail/multi-policy-container.h
@@ -77,6 +77,13 @@
     Value::value_.erase (item);
     Super::erase (item);
   }  
+
+  void
+  clear ()
+  {
+    Value::value_.clear ();
+    Super::clear ();
+  }
 };
 
 template< class Base >
@@ -88,6 +95,7 @@
   bool insert (typename Base::iterator item) { return true; }
   void lookup (typename Base::iterator item) {}
   void erase (typename Base::iterator item) {}
+  void clear () {}
 };
 
 template< class Base, class Vector >
diff --git a/utils/empty-policy.h b/utils/empty-policy.h
index 0fe43f8..c5f324c 100644
--- a/utils/empty-policy.h
+++ b/utils/empty-policy.h
@@ -26,21 +26,24 @@
 
 struct empty_policy_traits
 {
-  typedef void policy_hook_type;
+  typedef void* policy_hook_type;
 
-  template<class Container> struct container_hook { typedef void type; }
+  template<class Container> struct container_hook { typedef void* type; };
 
   template<class Base,
            class Container,
            class Hook>
   struct policy 
   {
-    class type
+    struct type
     {
-      inline void update (typename parent_trie::iterator) { }
-      inline bool insert (typename parent_trie::iterator) { return true; }
-      inline void  lookup (typename parent_trie::iterator item) { }
-      inline void erase (typename parent_trie::iterator item) { }
+      inline type (Base &base) {}
+      
+      inline void update (typename Container::iterator) { }
+      inline bool insert (typename Container::iterator) { return true; }
+      inline void lookup (typename Container::iterator item) { }
+      inline void erase (typename Container::iterator item) { }
+      inline void clear () { }
     };
   };
 };
diff --git a/utils/fifo-policy.h b/utils/fifo-policy.h
index 9f215fc..2dccbe4 100644
--- a/utils/fifo-policy.h
+++ b/utils/fifo-policy.h
@@ -90,6 +90,12 @@
       }
 
       inline void
+      clear ()
+      {
+        policy_container::clear ();
+      }
+
+      inline void
       set_max_size (size_t max_size)
       {
         max_size_ = max_size;
diff --git a/utils/lru-policy.h b/utils/lru-policy.h
index bf03fa8..077d602 100644
--- a/utils/lru-policy.h
+++ b/utils/lru-policy.h
@@ -95,6 +95,12 @@
       }
 
       inline void
+      clear ()
+      {
+        policy_container::clear ();
+      }
+
+      inline void
       set_max_size (size_t max_size)
       {
         max_size_ = max_size;
diff --git a/utils/multi-policy.h b/utils/multi-policy.h
index fd126ae..f5cf682 100644
--- a/utils/multi-policy.h
+++ b/utils/multi-policy.h
@@ -115,6 +115,12 @@
       {
         policy_container::erase (item);
       }
+      
+      inline void
+      clear ()
+      {
+        policy_container::clear ();
+      }
     };
   };
 };
diff --git a/utils/random-policy.h b/utils/random-policy.h
index 705bcf3..7a96712 100644
--- a/utils/random-policy.h
+++ b/utils/random-policy.h
@@ -127,6 +127,12 @@
       }
 
       inline void
+      clear ()
+      {
+        policy_container::clear ();
+      }
+
+      inline void
       set_max_size (size_t max_size)
       {
         max_size_ = max_size;
diff --git a/utils/trie-with-policy.h b/utils/trie-with-policy.h
index c674ef2..79480da 100644
--- a/utils/trie-with-policy.h
+++ b/utils/trie-with-policy.h
@@ -53,7 +53,7 @@
   }
 
   inline std::pair< iterator, bool >
-  insert (const FullKey &key, typename PayloadTraits::const_pointer_type payload)
+  insert (const FullKey &key, typename PayloadTraits::pointer_type payload)
   {
     std::pair<iterator, bool> item =
       trie_.insert (key, payload);
@@ -69,14 +69,26 @@
       }
     else
       {
-        item.first->set_payload (payload);
-        policy_.update (s_iterator_to (item.first));
+        return std::make_pair (s_iterator_to (item.first), false);
       }
 
     return item;
   }
 
   inline void
+  erase (const FullKey &key)
+  {
+    iterator foundItem, lastItem;
+    bool reachLast;
+    boost::tie (foundItem, reachLast, lastItem) = trie_.find (key);
+    
+    if (!reachLast || lastItem->payload () == PayloadTraits::empty_payload)
+      return; // nothing to invalidate
+
+    erase (lastItem);
+  }
+
+  inline void
   erase (iterator node)
   {
     if (node == end ()) return;
@@ -85,18 +97,39 @@
     node->erase (); // will do cleanup here
   }
 
+  inline void
+  clear ()
+  {
+    policy_.clear ();
+    trie_.clear ();
+  }
+
+  template<typename Modifier>
+  bool
+  modify (iterator position, Modifier mod)
+  {
+    if (position == end ()) return false;
+    if (position->payload () == PayloadTraits::empty_payload) return false;
+
+    mod (*position->payload ());
+    policy_.update (position);
+    return true;
+  }
+  
   /**
    * @brief Find a node that has the longest common prefix with key (FIB/PIT lookup)
    */
   inline iterator
   longest_prefix_match (const FullKey &key)
   {
-    boost::tuple< iterator, bool, iterator > item = trie_.find (key);
-    if (item.template get<0> () != trie_.end ())
+    iterator foundItem, lastItem;
+    bool reachLast;
+    boost::tie (foundItem, reachLast, lastItem) = trie_.find (key);
+    if (foundItem != trie_.end ())
       {
-        policy_.lookup (s_iterator_to (item.template get<0> ()));
+        policy_.lookup (s_iterator_to (foundItem));
       }
-    return item.template get<0> ();
+    return foundItem;
   }
 
   /**
@@ -159,7 +192,7 @@
       }
   }
 
-  iterator end ()
+  iterator end () const
   {
     return 0;
   }
@@ -190,4 +223,3 @@
 } // ndnSIM
 
 #endif // TRIE_WITH_POLICY_H_
-
diff --git a/utils/trie.h b/utils/trie.h
index 47e62e5..86ca01f 100644
--- a/utils/trie.h
+++ b/utils/trie.h
@@ -29,6 +29,7 @@
 #include <boost/functional/hash.hpp>
 #include <boost/interprocess/smart_ptr/unique_ptr.hpp>
 #include <boost/tuple/tuple.hpp>
+#include <boost/foreach.hpp>
 
 namespace ndnSIM
 {
@@ -43,11 +44,11 @@
   typedef Payload*        pointer_type;
   typedef const Payload*  const_pointer_type;
 
-  static const Payload* empty_payload;
+  static Payload* empty_payload;
 };
 
 template<typename Payload>
-const Payload*
+Payload*
 pointer_payload_traits<Payload>::empty_payload = 0;
 
 template<typename Payload>
@@ -57,11 +58,11 @@
   typedef ns3::Ptr<Payload>       pointer_type;
   typedef ns3::Ptr<const Payload> const_pointer_type;
   
-  static const ns3::Ptr<const Payload> empty_payload;
+  static ns3::Ptr<Payload> empty_payload;
 };
 
 template<typename Payload>
-const ns3::Ptr<const Payload>
+ns3::Ptr<Payload>
 smart_pointer_payload_traits<Payload>::empty_payload = 0;
 
 
@@ -109,6 +110,12 @@
 
   inline
   ~trie ();
+
+  void
+  clear ()
+  {
+    children_.clear_and_dispose (trie_delete_disposer ());
+  }
   
   // actual entry
   friend bool
@@ -120,7 +127,7 @@
 
   inline std::pair<iterator, bool>
   insert (const FullKey &key,
-          typename PayloadTraits::const_pointer_type payload);
+          typename PayloadTraits::pointer_type payload);
 
   /**
    * @brief Removes payload (if it exists) and if there are no children, prunes parents trie
@@ -134,6 +141,12 @@
   inline void
   prune ();
 
+  inline boost::tuple<const iterator, bool, const iterator>
+  find (const FullKey &key) const
+  {
+    return const_cast<trie*> (this)->find (key);
+  }
+
   /**
    * @brief Perform the longest prefix match
    * @param key the key for which to perform the longest prefix match
@@ -175,8 +188,14 @@
     return payload_;
   }
 
+  typename PayloadTraits::pointer_type
+  payload ()
+  {
+    return payload_;
+  }
+
   void
-  set_payload (typename PayloadTraits::const_pointer_type payload)
+  set_payload (typename PayloadTraits::pointer_type payload)
   {
     payload_ = payload;
   }
@@ -237,7 +256,7 @@
   buckets_array buckets_;
   unordered_set children_;
   
-  typename PayloadTraits::const_pointer_type payload_;
+  typename PayloadTraits::pointer_type payload_;
   trie *parent_; // to make cleaning effective
 };
 
@@ -267,7 +286,7 @@
 inline
 std::pair<typename trie<FullKey, Payload, PayloadTraits, PolicyHook>::iterator, bool>
 trie<FullKey, Payload, PayloadTraits, PolicyHook>
-::insert (const FullKey &key, typename PayloadTraits::const_pointer_type payload)
+::insert (const FullKey &key, typename PayloadTraits::pointer_type payload)
 {
   trie *trieNode = this;