IPFW | Too many dynamic rules?

[Jos Chrispijn]

Just ran into this matter (never experienced it until now):

"Cannot allocate dynamic state, consider increasing net.inet.ip.fw.dyn_max"

- What can be the cause of this sudden incident?
- Look like ipfw is suddenly processing too many rules?

Do I have to increase that in /etc/sysctl.conf and with what numbers can 
I do that best (depending on my BSD configuration or what is the usual 
formule on this)?

Thanks, Jos