diff -r 88debdc5d29d src/internet-stack/pending-data.cc
--- a/src/internet-stack/pending-data.cc	Mon Mar 01 14:36:41 2010 +0000
+++ b/src/internet-stack/pending-data.cc	Wed Mar 03 15:45:24 2010 +0000
@@ -102,6 +102,7 @@
 {
   data.push_back(p);
   size += p->GetSize();
+  //std::cout << this << ": pending data size: " << size << " (" << int(data.size ()) << " packets)" << std::endl;
 }
 
 uint32_t PendingData::SizeFromSeq (const SequenceNumber& f, const SequenceNumber& o)
diff -r 88debdc5d29d src/internet-stack/tcp-socket-impl.cc
--- a/src/internet-stack/tcp-socket-impl.cc	Mon Mar 01 14:36:41 2010 +0000
+++ b/src/internet-stack/tcp-socket-impl.cc	Wed Mar 03 15:45:24 2010 +0000
@@ -1387,7 +1387,7 @@
     }
   // See if all pending ack'ed; if so we can delete the data
   if (m_pendingData)
-    { // Data exists, see if can be deleted
+    { // Data exists, see if can be entirely deleted
       if (m_pendingData->SizeFromSeq (m_firstPendingSequence, m_highestRxAck) == 0)
         { // All pending acked, can be deleted
           m_pendingData->Clear ();
@@ -1399,6 +1399,34 @@
                         Simulator::GetDelayLeft (m_retxEvent)).GetSeconds());
           m_retxEvent.Cancel ();
         }
+      else // else delete just a portion
+        {
+          // std::cout << "begin delete portion of pending data;"
+          //           << " m_firstPendingSequence=" << m_firstPendingSequence
+          //           << "; m_highestRxAck=" << m_highestRxAck
+          //           << "; size=" << m_pendingData->size << std::endl;
+          
+          for (std::vector< Ptr<Packet> >::iterator dataI = m_pendingData->data.begin ();
+               dataI != m_pendingData->data.end ();)
+            {
+              Ptr<Packet> data = *dataI;
+              // std::cout << "pending packet of size " << data->GetSize () << std::endl;
+              if (m_firstPendingSequence + SequenceNumber (data->GetSize ()) <= m_highestRxAck)
+                {
+                  dataI = m_pendingData->data.erase (dataI);
+                  m_pendingData->size -= data->GetSize ();
+                  m_firstPendingSequence += data->GetSize ();
+                }
+              else
+                {
+                  break;
+                }
+            }
+          // std::cout << "  end delete portion of pending data;"
+          //           << " m_firstPendingSequence=" << m_firstPendingSequence
+          //           << "; m_highestRxAck=" << m_highestRxAck
+          //           << "; size=" << m_pendingData->size << std::endl;
+        }
     }
   // Try to send more data
   SendPendingData (m_connected);