[noonat]

A common solution is to have the server track which state frames that the clients have acknowledged receiving. The server can then delta compress from that client’s frame, for each client. It’s a bit more costly on the server side, as it means you need to maintain state frames back to the oldest acknowledged frame across all clients, but it guarantees you will be sending a packet a client can understand. Usually this is combined with some sort of limit which kicks a client off as timed out if its acknowledged frame strays too far from the most recent one.