Systems that do not support mandatory access control processing can participate in a multilevel secure network, if they are physically managed to guarantee that all information on the system has the same single security label and all users of the system are permitted to that security label. These systems are referred to as single-level security or managed systems in this information. This management requires both physical control of the systems and careful management of the network. Managed systems must be prevented from communicating with other managed systems that do not have equivalent security labels.
Systems that support mandatory access control and are configured to implicitly associate the correct security label with each managed system can also communicate with managed systems. The systems that perform mandatory access control are responsible for ensuring that only information from applications with an equivalent security label is sent to a managed system, and that information received from a managed system is given only to applications with an equivalent security label.