PF round robin load balancing

["Gustavo V. G. C. Rios" <gustavo_(_dot_)_rios_(_at_)_terra_(_dot_)_com_(_dot_)_br>]

I wonder what's the criteria for load balacing (outgoing)with round
robin?

Is it based on :

0) The number of packets outgone
1) The number of octet outgone
2) The number of packets outgone + income
3) The number of octets outgone + income

Thanks ?