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diff --git a/src/bin/perfdhcp/rate_control.h b/src/bin/perfdhcp/rate_control.h
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+// Copyright (C) 2013-2019 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef RATE_CONTROL_H
+#define RATE_CONTROL_H
+
+#include <boost/date_time/posix_time/posix_time.hpp>
+
+namespace isc {
+namespace perfdhcp {
+
+/// \brief A message sending rate control class for perfdhcp.
+///
+/// This class provides the means to control the rate at which messages
+/// of the specific type are sent by perfdhcp. Each message type,
+/// for which the desired rate can be specified, has a corresponding
+/// \c RateControl object. So, the perfdhcp is using up to three objects
+/// of this type at the same time, to control the rate of the following
+/// messages being sent:
+/// - Discover(DHCPv4) or Solicit (DHCPv6)
+/// - Renew (DHCPv6) or Request (DHCPv4) to renew leases.
+/// - Release
+///
+/// The purpose of the RateControl class is to track the due time for
+/// sending next message (or bunch of messages) to keep outbound rate
+/// of particular messages at the desired level. The due time is calculated
+/// using the desired rate value and the timestamp when the last message of
+/// the particular type has been sent. That puts the responsibility on the
+/// \c TestControl class to invoke the \c RateControl::updateSendDue, every
+/// time the message is sent.
+///
+/// The \c RateControl object returns the number of messages to be sent at
+/// the time. The number returned is 0, if perfdhcp shouldn't send any messages
+/// yet, or 1 (sometimes more) if the send due time has been reached.
+class RateControl {
+public:
+
+    /// \brief Default constructor.
+    RateControl();
+
+    /// \brief Constructor which sets desired rate.
+    ///
+    /// \param rate A desired rate.
+    RateControl(const unsigned int rate);
+
+    /// \brief Returns number of messages to be sent "now".
+    ///
+    /// This function calculates how many messages of the given type should
+    /// be sent immediately when the call to the function returns, to catch
+    /// up with the desired message rate.
+    ///
+    /// The value returned depends on the due time calculated with the
+    /// \c RateControl::updateSendDue function and the current time. If
+    /// the due time has been hit, the non-zero number of messages is returned.
+    /// If the due time hasn't been hit, the number returned is 0.
+    ///
+    /// If the rate is non-zero, the number of messages to be sent is calculated
+    /// as follows:
+    /// \code
+    ///          num = duration * rate
+    /// \endcode
+    /// where <b>duration</b> is a time period between the due time to send
+    /// next set of messages and current time. The duration is expressed in
+    /// seconds with the fractional part having 6 or 9 digits (depending on
+    /// the timer resolution). If the calculated value is equal to 0, it is
+    /// rounded to 1, so as at least one message is sent.
+    ///
+    /// \return A number of messages to be sent immediately.
+    uint64_t getOutboundMessageCount(bool const waiting_to_exit = false);
+
+    /// \brief Returns the rate.
+    unsigned int getRate() const {
+        return (rate_);
+    }
+
+    /// \brief Sets the new rate.
+    ///
+    /// \param rate A new value of rate. This value must not be negative.
+    /// \throw isc::BadValue if new rate is negative.
+    void setRate(const int rate);
+
+protected:
+
+    /// \brief Convenience function returning current time.
+    ///
+    /// \return current time.
+    boost::posix_time::ptime currentTime();
+
+    /// \brief Holds a desired rate value.
+    unsigned int rate_;
+
+    /// \brief Holds number of packets send from the beginning.
+
+    /// It is used to calculate current request rate. Then this is used
+    /// to estimate number of packets to send in current cycle.
+    uint64_t total_pkts_sent_count_;
+
+    /// \brief Holds time of start of testing.
+
+    /// It is used to calculate current request rate. Then this is used
+    /// to estimate number of packets to send in current cycle.
+    boost::posix_time::ptime start_time_;
+};
+
+}
+}
+
+#endif