diff --git a/src/simulator/watchdog.cc b/src/simulator/watchdog.cc
new file mode 100644
index 000000000..c12743e34
--- /dev/null
+++ b/src/simulator/watchdog.cc
@@ -0,0 +1,60 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2007 INRIA
+ *
+ * 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
+ */
+#include "watchdog.h"
+
+namespace ns3 {
+
+Watchdog::Watchdog ()
+  : m_impl (0),
+    m_event (),
+    m_end (MicroSeconds (0))
+{}
+
+Watchdog::~Watchdog ()
+{
+  delete m_impl;
+}
+
+void 
+Watchdog::Ping (Time delay)
+{
+  Time end = Simulator::Now () + delay;
+  m_end = std::max (m_end, end);
+  if (m_event.IsRunning ())
+    {
+      return;
+    }
+  m_event = Simulator::Schedule (m_end - Now (), &Watchdog::Expire, this);
+}
+
+void
+Watchdog::Expire (void)
+{
+  if (m_end == Simulator::Now ())
+    {
+      m_impl->Invoke ();
+    }
+  else
+    {
+      m_event = Simulator::Schedule (m_end - Now (), &Watchdog::Expire, this);
+    }
+}
+
+} // namespace ns3
diff --git a/src/simulator/watchdog.h b/src/simulator/watchdog.h
new file mode 100644
index 000000000..3bb37a9b4
--- /dev/null
+++ b/src/simulator/watchdog.h
@@ -0,0 +1,217 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2007 INRIA
+ *
+ * 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
+ */
+#ifndef WATCHDOG_H
+#define WATCHDOG_H
+
+#include "nstime.h"
+#include "event-id.h"
+
+namespace ns3 {
+
+class TimerImpl;
+
+class Watchdog 
+{
+public:
+  Watchdog ();
+  ~Watchdog ();
+
+  void Ping (Time delay);
+
+  /**
+   * \param fn the function
+   *
+   * Store this function in this Timer for later use by Timer::Schedule.
+   */
+  template <typename FN>
+  void SetFunction (FN fn);
+
+  /**
+   * \param memPtr the member function pointer
+   * \param objPtr the pointer to object
+   *
+   * Store this function and object in this Timer for later use by Timer::Schedule.
+   */
+  template <typename MEM_PTR, typename OBJ_PTR>
+  void SetFunction (MEM_PTR memPtr, OBJ_PTR objPtr);
+
+
+  /**
+   * \param a1 the first argument
+   *
+   * Store this argument in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1>
+  void SetArguments (T1 a1);
+  /**
+   * \param a1 the first argument
+   * \param a2 the second argument
+   *
+   * Store these arguments in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1, typename T2>
+  void SetArguments (T1 a1, T2 a2);
+  /**
+   * \param a1 the first argument
+   * \param a2 the second argument
+   * \param a3 the third argument
+   *
+   * Store these arguments in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1, typename T2, typename T3>
+  void SetArguments (T1 a1, T2 a2, T3 a3);
+  /**
+   * \param a1 the first argument
+   * \param a2 the second argument
+   * \param a3 the third argument
+   * \param a4 the fourth argument
+   *
+   * Store these arguments in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1, typename T2, typename T3, typename T4>
+  void SetArguments (T1 a1, T2 a2, T3 a3, T4 a4);
+  /**
+   * \param a1 the first argument
+   * \param a2 the second argument
+   * \param a3 the third argument
+   * \param a4 the fourth argument
+   * \param a5 the fifth argument
+   *
+   * Store these arguments in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1, typename T2, typename T3, typename T4, typename T5>
+  void SetArguments (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5);
+  /**
+   * \param a1 the first argument
+   * \param a2 the second argument
+   * \param a3 the third argument
+   * \param a4 the fourth argument
+   * \param a5 the fifth argument
+   * \param a6 the sixth argument
+   *
+   * Store these arguments in this Timer for later use by Timer::Schedule.
+   */
+  template <typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
+  void SetArguments (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5, T6 a6);
+
+private:
+  void Expire (void);
+  TimerImpl *m_impl;
+  EventId m_event;
+  Time m_end;
+};
+
+} // namespace ns3
+
+#include "timer-impl.h"
+
+namespace ns3 {
+
+
+template <typename FN>
+void 
+Watchdog::SetFunction (FN fn)
+{
+  delete m_impl;
+  m_impl = MakeTimerImpl (fn);
+}
+template <typename MEM_PTR, typename OBJ_PTR>
+void 
+Watchdog::SetFunction (MEM_PTR memPtr, OBJ_PTR objPtr)
+{
+  delete m_impl;
+  m_impl = MakeTimerImpl (memPtr, objPtr);
+}
+
+template <typename T1>
+void 
+Watchdog::SetArguments (T1 a1)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1);
+}
+template <typename T1, typename T2>
+void 
+Watchdog::SetArguments (T1 a1, T2 a2)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1, a2);
+}
+
+template <typename T1, typename T2, typename T3>
+void 
+Watchdog::SetArguments (T1 a1, T2 a2, T3 a3)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1, a2, a3);
+}
+
+template <typename T1, typename T2, typename T3, typename T4>
+void 
+Watchdog::SetArguments (T1 a1, T2 a2, T3 a3, T4 a4)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1, a2, a3, a4);
+}
+
+template <typename T1, typename T2, typename T3, typename T4, typename T5>
+void 
+Watchdog::SetArguments (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1, a2, a3, a4, a5);
+}
+
+template <typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
+void 
+Watchdog::SetArguments (T1 a1, T2 a2, T3 a3, T4 a4, T5 a5, T6 a6)
+{
+  if (m_impl == 0)
+    {
+      NS_FATAL_ERROR ("You cannot set the arguments of a Watchdog before setting its function.");
+      return;
+    }
+  m_impl->SetArgs (a1, a2, a3, a4, a5, a6);
+}
+
+} // namespace ns3
+
+
+#endif /* WATCHDOG_H */
diff --git a/src/simulator/wscript b/src/simulator/wscript
index d0a0817a7..09da776f3 100644
--- a/src/simulator/wscript
+++ b/src/simulator/wscript
@@ -62,6 +62,7 @@ def build(bld):
         'time-default-value.cc',
         'timer.cc',
         'event-garbage-collector.cc',
+        'watchdog.cc',
         ]
 
     headers = bld.create_obj('ns3header')