ReplicationMode::SinceLastSend doesn't work in all situations

[cBournhonesque]

There are 2 modes of replication:

• SinceLastAck: we keep sending updates for a component if the component changed since the last tick that was acked.
  • This means that we will consistently send too many updates.
  • For example: tick 1 = C1A-update. tick 2 = C1A send. tick 3 = C1A send. tick 4 = receive ack, stop sending C1A.
• SinceLastSend: we send updates for a component if the component changed since the last tick that we sent. Since packet loss is low (<1%), most of the times that's valid
  • For example: Tick 1 = C1A-update. send_tick = 1. Tick 2: stop sending C1A.

If a packet is loss, the send_tick goes back to the ack_tick for the replication group, so we send all component updates since the last ack.

However let's consider this scenario in mode SinceLastSend:

• tick 1= C1A-update. send_tick = 1
• tick 2 = C1B-update. send_tick = 2 -> this packet gets lost
• tick 3 = C2-insert. send_tick = 3
• tick 5: receive ACK1. ack_tick = 1
• tick 6: receive ACK3. ack_tick = 3
• tick 10: receive NACK2. send_tick = ack_tick = 3

This is not what we want, we would like C1 on the receiver to have the value C1B, but it will stay at C1A.

Solution:

• keep the send_tick/ack_tick per entity/component?