snapshot token receives a message that does not bear the snapshot token, this process will forward that message to the observer process. This message was obviously sent before the snapshot “cut off” (as it does not bear a snapshot token and thus must have come from before the snapshot token was sent out) and needs to be included in the snapshot. From this, the observer builds up a complete snapshot: a saved state for each process and all messages “in the ether” are saved. References Distributed algorithms