--- a/src/internet-stack/tcp-socket-impl.cc	Wed Dec 03 17:47:03 2008 -0800
+++ b/src/internet-stack/tcp-socket-impl.cc	Wed Dec 03 21:08:44 2008 -0500
@@ -1266,7 +1266,10 @@
   }
   else
   {
-    m_delAckEvent = Simulator::Schedule (m_delAckTimeout, &TcpSocketImpl::DelAckTimeout, this);
+    if (m_delAckEvent.IsExpired())
+    {
+      m_delAckEvent = Simulator::Schedule (m_delAckTimeout, &TcpSocketImpl::DelAckTimeout, this);
+    }
   }
 }