diff --git a/tools/ping/client/statistics-collector.hpp b/tools/ping/client/statistics-collector.hpp
index 2ced820..ee67f80 100644
--- a/tools/ping/client/statistics-collector.hpp
+++ b/tools/ping/client/statistics-collector.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2015,  Arizona Board of Regents.
+ * Copyright (c) 2015-2016,  Arizona Board of Regents.
  *
  * This file is part of ndn-tools (Named Data Networking Essential Tools).
  * See AUTHORS.md for complete list of ndn-tools authors and contributors.
@@ -18,6 +18,7 @@
  *
  * @author: Eric Newberry <enewberry@email.arizona.edu>
  * @author: Jerald Paul Abraham <jeraldabraham@email.arizona.edu>
+ * @author: Teng Liang <philoliang@email.arizona.edu>
  */
 
 #ifndef NDN_TOOLS_PING_CLIENT_STATISTICS_COLLECTOR_HPP
@@ -39,10 +40,12 @@
   Name prefix;                                  //!< prefix pinged
   int nSent;                                    //!< number of pings sent
   int nReceived;                                //!< number of pings received
+  int nNacked;                                  //!< number of nacks received
   time::steady_clock::TimePoint pingStartTime;  //!< time pings started
   double minRtt;                                //!< minimum round trip time
   double maxRtt;                                //!< maximum round trip time
   double packetLossRate;                        //!< packet loss rate
+  double packetNackedRate;                      //!< packet nacked rate
   double sumRtt;                                //!< sum of round trip times
   double avgRtt;                                //!< average round trip time
   double stdDevRtt;                             //!< std dev of round trip time
@@ -71,12 +74,18 @@
 
 PUBLIC_WITH_TESTS_ELSE_PRIVATE:
   /**
-   * @brief Called on ping response received
+   * @brief Called when a Data packet is received
    *
    * @param rtt round trip time
    */
   void
-  recordResponse(Rtt rtt);
+  recordData(Rtt rtt);
+
+  /**
+   * @brief Called when a Nack is received
+   */
+  void
+  recordNack();
 
   /**
    * @brief Called on ping timeout
@@ -89,6 +98,7 @@
   const Options& m_options;
   int m_nSent;
   int m_nReceived;
+  int m_nNacked;
   time::steady_clock::TimePoint m_pingStartTime;
   double m_minRtt;
   double m_maxRtt;