How to limit pps without drop?

Question

iptables

I have a SIP server, which, of course, gets a lot of INVITEs. Due to the specifics of clients, packets arrive in a bunch, and then "silence" on the air. Those. 30 INVITEs arrived at once, then silence.
So here's how you can over-limit the number. INVITEs up to 5/sec, and the rest are NOT dropped, but delivered with a delay. Those. the same 30 INVITEs, but not for 1 sec, but for 6 sec with a rate of 5 pps.