diff --git a/src/clients/iterative-query-controller.hpp b/src/clients/iterative-query-controller.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014, Regents of the University of California.
+ *
+ * This file is part of NDNS (Named Data Networking Domain Name Service).
+ * See AUTHORS.md for complete list of NDNS authors and contributors.
+ *
+ * NDNS is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NDNS 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
+ * NDNS, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NDNS_CLIENTS_ITERATIVE_QUERY_CONTROLLER_HPP
+#define NDNS_CLIENTS_ITERATIVE_QUERY_CONTROLLER_HPP
+
+#include "ndns-enum.hpp"
+#include "query.hpp"
+#include "response.hpp"
+#include "query-controller.hpp"
+#include "config.hpp"
+#include "common.hpp"
+
+#include <ndn-cxx/common.hpp>
+#include <ndn-cxx/data.hpp>
+#include <ndn-cxx/interest.hpp>
+#include <ndn-cxx/name.hpp>
+
+namespace ndn {
+namespace ndns {
+
+/**
+ * @brief controller which iteratively query a target label
+ */
+class IterativeQueryController : public QueryController
+{
+public:
+  /**
+   * @brief indicates a step in an iterative query process.
+   * Iterative Query contains multiple steps which are listed here
+   */
+  enum QueryStep {
+    QUERY_STEP_QUERY_NS = 1, ///< to query the naming server, before querying NS & waiting for Data
+    QUERY_STEP_QUERY_RR, ///< to query RR, before querying RR & waiting for it Data
+    QUERY_STEP_ANSWER_STUB, ///< to answer to stub resolver, after getting final Response,
+                            ///< or NACK or timeout
+    QUERY_STEP_ABORT, ///< to abort the resolver process, if unexpected behavior happens
+    QUERY_STEP_UNKNOWN = 255
+  };
+
+public:
+  explicit
+  IterativeQueryController(const Name& dstLabel, const name::Component& rrType,
+                           const time::milliseconds& interestLifetime,
+                           const QuerySucceedCallback& onSucceed, const QueryFailCallback& onFail,
+                           Face& face);
+
+  virtual void
+  start();
+
+  /**
+   * @brief return false if the current status is not QUEYR_STEP_QUERY_NS
+   * or QUERY_STEP_QUERY_RR
+   */
+  virtual bool
+  hasEnded();
+
+NDNS_PUBLIC_WITH_TESTS_ELSE_PRIVATE:
+  void
+  onData(const ndn::Interest& interest, const Data& data);
+
+  /**
+   * @brief change the Controller state according to timeout. For current,
+   * abort the query when timeout
+   */
+  void
+  onTimeout(const Interest& interest);
+
+  void
+  abort();
+
+  /**
+   * @brief get the Interest according to current Controller state.
+   * Only be valid on State QueryNS & QueryRR, or throw exception
+   */
+  const Interest
+  makeLatestInterest();
+
+  const Response
+  parseFinalResponse(const Data& data);
+
+  void
+  express(const Interest& interest);
+
+  void
+  setNFinishedComps(size_t finished)
+  {
+    m_nFinishedComps = finished;
+  }
+
+public:
+  QueryStep
+  getStep() const
+  {
+    return m_step;
+  }
+
+  size_t
+  getNFinishedComps() const
+  {
+    return m_nFinishedComps;
+  }
+
+  size_t
+  getNTryComps() const
+  {
+    return m_nTryComps;
+  }
+
+protected:
+  /**
+   * @brief current query step
+   */
+  QueryStep m_step;
+
+  /*
+   * the number of label that has been resolved successfully
+   * This also define the next AuthZone prefix
+   * AuthZone = m_query.getRrLabel().getPrefix(m_nFinishedComps)
+   */
+  size_t m_nFinishedComps;
+
+  /*
+   * used when query the KSK (key signing key), e.g., /net/ndnsim/ksk-1
+   */
+  size_t m_nTryComps;
+};
+
+std::ostream&
+operator<<(std::ostream& os, const IterativeQueryController& iq);
+
+std::ostream&
+operator<<(std::ostream& os, const IterativeQueryController::QueryStep step);
+
+} // namespace ndns
+} // namespace ndn
+
+#endif // NDNS_CLIENTS_ITERATIVE_QUERY_HPP