Logical isolation is also called protocol isolation, and the national standard defines logical isolation as follows: Refers to the network in different security domains are physically connected, through the means of protocol conversion to ensure that the protected information is logically isolated, only the system requires transmission, content limited information can pass (GB17859-1999 and GB\/T20271-2006 established terms). The core of logical isolation is the protocol, which can define the transmission direction and be monitored. The direction of transmission is controllable one-way transmission, which can be two-way. But all transmissions are monitored, non-closed or encrypted protocols. The data transfer between the protected end and the public end can be monitored.
Logical isolation is mainly achieved through a logical isolator, which is an isolation component between different networks. The two ends of the isolation still have a physical data channel connection, but there is no data channel on the two ends of the isolation through technical means.