diff -r dfa8958e616e src/internet-stack/tcp-socket-impl.cc
--- a/src/internet-stack/tcp-socket-impl.cc	Sat Mar 20 21:58:06 2010 +0100
+++ b/src/internet-stack/tcp-socket-impl.cc	Thu Mar 25 11:01:50 2010 -0400
@@ -79,6 +79,7 @@
     m_closeRequestNotified (false),
     m_closeOnEmpty (false),
     m_pendingClose (false),
+    m_finAckRcvd (false),
     m_nextTxSequence (0),
     m_highTxMark (0),
     m_highestRxAck (0),
@@ -116,6 +117,7 @@
     m_closeRequestNotified (sock.m_closeRequestNotified),
     m_closeOnEmpty (sock.m_closeOnEmpty),
     m_pendingClose (sock.m_pendingClose),
+    m_finAckRcvd (sock.m_finAckRcvd),
     m_nextTxSequence (sock.m_nextTxSequence),
     m_highTxMark (sock.m_highTxMark),
     m_highestRxAck (sock.m_highestRxAck),
@@ -700,6 +702,15 @@
   m_rxWindowSize = tcpHeader.GetWindowSize (); //update the flow control window
 
   Events_t event = SimulationSingleton<TcpStateMachine>::Get ()->FlagsEvent (tcpHeader.GetFlags () );
+
+  if ((m_state == FIN_WAIT_1 || m_state == LAST_ACK) && event == ACK_RX)
+    {
+      if (tcpHeader.GetSequenceNumber () == m_nextRxSequence)
+        {
+          m_finAckRcvd = true;
+        }
+    }
+
   Actions_t action = ProcessEvent (event); //updates the state
   NS_LOG_DEBUG("Socket " << this << 
                " processing pkt action, " << action <<
@@ -719,7 +730,24 @@
 
   bool needCloseNotify = (stateAction.state == CLOSED && m_state != CLOSED 
     && e != TIMEOUT);
-  m_state = stateAction.state;
+  if (m_state == FIN_WAIT_1 && stateAction.state == FIN_WAIT_2)
+    {
+      if (m_finAckRcvd == true)
+        {
+          m_state = stateAction.state;
+        }
+    }
+  else if (m_state == LAST_ACK && stateAction.state == CLOSED)
+    {
+      if (m_finAckRcvd == true)
+        {
+          m_state = stateAction.state;
+        }
+    }
+  else
+    {
+      m_state = stateAction.state;
+    }
   NS_LOG_LOGIC ("TcpSocketImpl " << this << " moved from state " << saveState 
     << " to state " <<m_state);
   NS_LOG_LOGIC ("TcpSocketImpl " << this << " pendingData " << m_pendingData);
@@ -1640,7 +1668,7 @@
 void TcpSocketImpl::Retransmit ()
 {
   NS_LOG_FUNCTION (this);
-  uint8_t flags = TcpHeader::NONE;
+  uint8_t flags = TcpHeader::ACK;
   if (m_state == SYN_SENT) 
     {
       if (m_cnCount > 0) 
diff -r dfa8958e616e src/internet-stack/tcp-socket-impl.h
--- a/src/internet-stack/tcp-socket-impl.h	Sat Mar 20 21:58:06 2010 +0100
+++ b/src/internet-stack/tcp-socket-impl.h	Thu Mar 25 11:01:50 2010 -0400
@@ -191,6 +191,7 @@
   bool m_closeRequestNotified;
   bool m_closeOnEmpty;
   bool m_pendingClose;
+  bool m_finAckRcvd;
 
   
   //sequence info, sender side