Don't IP packets have field for the security classification and compartment of the data? I was taught that one is not permitted to mix different security level

Don't IP packets have field for the security classification and compartment of the data? I was taught that one is not permitted to mix different security levels in a single computer; that is one may not have both top secret and secret. The problems the government is facing with information security the last few years were largely a solved problem in 1989. Who dropped the ball?