Partitioning Communication System is a computer and communications security architecture based on an information flow separation policy. The PCS extends the four foundational security policies of a MILS (Multiple Independent Levels of Security) software architecture to the network: * End-to-end Information Flow * End-to-end Data Isolation * End-to-end Periods Processing * End-to-end Damage Limitation * Non-bypassable * Evaluatable * Always-invoked * Tamper-proof The PCS was invented by OIS. OIS collaborated extensively on the requirements for the PCS with: