--- ns-allinone-3.23/ns-3.23/src/internet/model/tcp-socket-base.cc	2015-05-13 14:05:27.000000000 -0400
+++ ns-patched-3.23/ns-3.23/src/internet/model/tcp-socket-base.cc	2015-06-19 07:37:17.855146362 -0400
@@ -2065,9 +2065,9 @@
     }
 
   // Notify the application of the data being sent unless this is a retransmit
-  if (seq == m_highTxMark)
+  if (m_highTxMark >= seq && m_highTxMark < (seq + sz))
     {
-      Simulator::ScheduleNow (&TcpSocketBase::NotifyDataSent, this, sz);
+      Simulator::ScheduleNow (&TcpSocketBase::NotifyDataSent, this, (seq + sz - m_highTxMark.Get ()));
     }
   // Update highTxMark
   m_highTxMark = std::max (seq + sz, m_highTxMark.Get ());