Hello I wan´t to know when is necessary to use connection marks, I´m using just packet marks without connection marks and I can´t see why I should use connection marks (What is the difference in using them?). Thanks

IF you use connection marks before packet marks, it reduces CPU load.

Connection mark help you keep track of the return traffic which are then marked with the same connection mark.

Skillful is correct. Additionally, when using Masq-NAT, you need the connection marks to be able to mark all the packets properly.