code: private void sendAck()
     {
       if (tc.isEntryEnabled())
         SibTr.entry(tc, "sendAck");
       
       try
       {
         upControl.sendAckMessage(null, null, null, iack, priority, reliability, streamID, false);
       }
       catch (SIException e)
       {
         // FFDC
         FFDCFilter.processException(
           e,
           "com.ibm.ws.sib.processor.gd.InternalInputStream.sendAck",
           "1:161:1.42",
           this);
           
         SibTr.exception(tc, e);
  
         //TODO don't know what to do here - rethrow?!
       } 
       
       if (tc.isEntryEnabled())
         SibTr.exit(tc, "sendAck");
     }
docs: /*
  Utility method to send Ack up to ackPrefix