Gapfilling Mode
There should be a receive_gapfilling(..., fill_value) mode with the following traits:
- If an expiry date approaches and the data is not there, a "zero" packet is delivered.
- The filling pattern (e.g. "zero" should be configurable on the receive call).
ToDo:
- Think about how to predict an "expiry" of a packet that has not been sent or recovered.