1. A system for providing multi-level security systems, comprising: a unique source address defined for each of a plurality of different security classifications to be used by a first multi-level security (“MLS”) system when sending outbound packets to a second MLS system; and means for processing each of the outbound packets sent from the first MLS system to the second MLS system, further comprising: means for determining, by the first MLS system, a particular one of the security classifications that applies to the outbound packet; means for locating, by the first MLS system, the unique source address defined for the determined particular one; means for replacing, by the first MLS system, a source address in a packet header of the outbound packet with the located unique source address thereby conveying the security classification that applies to the outbound packet through the source address in the packet header; and means for sending, by the first MLS system responsive to operation of the means for replacing, the outbound packet to the second MLS system.