code: private void processAckExpected(ControlAckExpected ackExpMsg)
                      throws SIResourceException
      {
  
          // This is called by a PubSubOutputHandler when it finds Unknown
          // ticks in it's own stream and need the InputStream to resend them
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(tc, "processAckExpected", ackExpMsg);
  
          // The upstream cellule for this stream is stored in the originStreamMap
          // unless we were the originator.
          SIBUuid12 streamID = ackExpMsg.getGuaranteedStreamUUID();
          int priority = ackExpMsg.getPriority().intValue();
          Reliability reliability = ackExpMsg.getReliability();
  
          if (_internalInputStreamManager.hasStream(streamID, priority, reliability))
          {
              _internalInputStreamManager.processAckExpected(ackExpMsg);
          }
          else
          {
              _targetStreamManager.handleAckExpectedMessage(ackExpMsg);
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "processAckExpected");
  
      }
docs: Process an AckExpected message.
  
  @param ackExpMsg The AckExpected message