diff --git a/apps/ndn-app.h b/apps/ndn-app.h
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+++ b/apps/ndn-app.h
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+/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2011 University of California, Los Angeles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#ifndef NDN_APP_H
+#define NDN_APP_H
+
+#include "ns3/application.h"
+#include "ns3/ptr.h"
+#include "ns3/callback.h"
+#include "ns3/traced-callback.h"
+
+namespace ns3 
+{
+
+class Packet;
+class NdnInterestHeader;
+class NdnContentObjectHeader;
+class NdnFace;
+
+/**
+ * @ingroup ndn
+ * @brief Base class that all Ndn applications should be derived from.
+ * 
+ * The class implements virtual calls onInterest, onNack, and onContentObject
+ */
+class NdnApp: public Application
+{
+public:
+  /**
+   * @brief A callback to pass packets to underlying Ndn protocol
+   */
+  typedef Callback<bool, const Ptr<const Packet>&> ProtocolHandler;
+  
+  static TypeId GetTypeId ();
+
+  /**
+   * @brief Default constructor
+   */
+  NdnApp ();
+  virtual ~NdnApp ();
+
+  /**
+   * @brief Register lower layer callback (to send interests from the application)
+   */
+  void
+  RegisterProtocolHandler (ProtocolHandler handler);
+  
+  /**
+   * @brief Method that will be called every time new Interest arrives
+   * @param interest Interest header
+   * @param packet   "Payload" of the interests packet. The actual payload should be zero, but packet itself
+   *                 may be useful to get packet tags
+   */
+  virtual void
+  OnInterest (const Ptr<const NdnInterestHeader> &interest, Ptr<Packet> packet);
+
+  /**
+   * @brief Method that will be called every time new NACK arrives
+   * @param interest Interest header
+   */
+  virtual void
+  OnNack (const Ptr<const NdnInterestHeader> &interest, Ptr<Packet> packet);
+  
+  /**
+   * @brief Method that will be called every time new ContentObject arrives
+   * @param contentObject ContentObject header
+   * @param payload payload (potentially virtual) of the ContentObject packet (may include packet tags of original packet)
+   */
+  virtual void
+  OnContentObject (const Ptr<const NdnContentObjectHeader> &contentObject,
+                   Ptr<Packet> payload);
+        
+protected:
+  /**
+   * @brief Do cleanup when application is destroyed
+   */
+  virtual void
+  DoDispose ();
+
+  // inherited from Application base class. Originally they were private
+  virtual void
+  StartApplication ();    ///< @brief Called at time specified by Start
+
+  virtual void
+  StopApplication ();     ///< @brief Called at time specified by Stop
+
+protected:
+  ProtocolHandler m_protocolHandler; ///< @brief A callback to pass packets to underlying Ndn protocol
+  bool m_active;  ///< @brief Flag to indicate that application is active (set by StartApplication and StopApplication)
+  Ptr<NdnFace> m_face;   ///< @brief automatically created application face through which application communicates
+
+  TracedCallback<Ptr<const NdnInterestHeader>,
+                 Ptr<NdnApp>, Ptr<NdnFace> > m_receivedInterests; ///< @brief App-level trace of received Interests
+
+  TracedCallback<Ptr<const NdnInterestHeader>,
+                 Ptr<NdnApp>, Ptr<NdnFace> > m_receivedNacks; ///< @brief App-level trace of received NACKs
+
+  TracedCallback<Ptr<const NdnContentObjectHeader>, Ptr<const Packet>,
+                 Ptr<NdnApp>, Ptr<NdnFace> > m_receivedContentObjects; ///< @brief App-level trace of received Data
+
+
+  TracedCallback<Ptr<const NdnInterestHeader>,
+                 Ptr<NdnApp>, Ptr<NdnFace> > m_transmittedInterests; ///< @brief App-level trace of transmitted Interests
+
+  TracedCallback<Ptr<const NdnContentObjectHeader>, Ptr<const Packet>,
+                 Ptr<NdnApp>, Ptr<NdnFace> > m_transmittedContentObjects; ///< @brief App-level trace of transmitted Data
+};
+
+} // namespace ns3
+
+#endif // NDN_APP_H