diff -r 46bb9407bd72 src/internet/model/tcp-newreno.cc
--- a/src/internet/model/tcp-newreno.cc	Fri Feb 21 11:50:18 2014 -0500
+++ b/src/internet/model/tcp-newreno.cc	Fri Feb 21 10:29:09 2014 -0800
@@ -128,8 +128,9 @@
       m_cWnd -= seq - m_txBuffer.HeadSequence ();
       m_cWnd += m_segmentSize;  // increase cwnd
       NS_LOG_INFO ("Partial ACK in fast recovery: cwnd set to " << m_cWnd);
+      m_txBuffer.DiscardUpTo(seq); // Bug 1850:  retransmit before NewAck()
+      DoRetransmit (); // Assume the next seq is lost. Retransmit lost packet
       TcpSocketBase::NewAck (seq); // update m_nextTxSequence and send new data if allowed by window
-      DoRetransmit (); // Assume the next seq is lost. Retransmit lost packet
       return;
     }
   else if (m_inFastRec && seq >= m_recover)