Timing issue with datagrams

[bigjosh]

@BGA

If there is a datagram pending, send it instead UNLESS a datagram was sent the previous iteration. In this case send a face value. This will at least prevent starvation if someone tries to just do a datagram storm to try to get them to be delivered.

I think this kind of flow control can only properly be done on the RX side since the sender could send a “forced” face value but it could get dropped - and in life the only thing that matters is what it received not what is sent.

I think the (admittedly ugly & awkward) way to handle this is to use the face values to control the datagrams. That is, you send a datagram and then you wait until either (1) you get an ACK via face value or (2) you timeout out. This way there is never more than 1 datagram pending and you also leverage the speed and auto repeat of the face values system.