Generating Tokens When a Queue Becomes Empty
============================================

The :ned:`QueueBasedTokenGenerator` module generates tokens into a token-based server when an observed queue becomes empty.
The module can be used by applications to create traffic that completely utilizes a network interface,
for example.

In this example network, packets are generated by a passive packet source (:ned:`PassivePacketSource`).
A token-based server (:ned:`TokenBasedServer`) pops packets from the source when it has enough tokens.
Then it pushes packets into the connected queue (:ned:`PacketQueue`). Packets are collected from the queue
by an active packet sink (:ned:`ActivePacketSink`). Tokens are generated by a :ned:`QueueBasedTokenGenerator`,
which observes the queue, and generates a token whenever the queue is empty.

.. figure:: media/QueueBasedTokenGenerator.png
   :width: 80%
   :align: center

.. literalinclude:: ../QueueingTutorial.ned
   :start-at: network QueueBasedTokenGenerator
   :end-before: //----
   :language: ned

.. literalinclude:: ../omnetpp.ini
   :start-at: Config QueueBasedTokenGenerator
   :end-at: collectionInterval
   :language: ini