Architecture of an open local area network for audio service support between users of partitioned domains

A system to allow exchange of data between a first security domain having a first security level and a second security domain having a second security level, wherein the first security level is higher than the second security level, wherein the first security domain comprises a first network transporting audio streams using at least one of IP and VoIP Internet protocols, wherein the system comprises:

• an insertion circuit to insert a security-level marker into audio streams as a function of the security level of the audio streams, by use of terminals in communication with the first network, the insertion circuit replacing predetermined bits of audio data in the audio streams with corresponding bits of the security-level marker;
• a filter circuit to filter the audio streams by use of a first and second filtering gateway, said filtering gateways being in communication with the first network, said filtering gateways being adapted to transform a communication protocol of the audio streams into another communication protocol;
• a detector circuit to detect the presence of a security-level marker in the audio stream arising from the first network, to produce a detected security-level marker;
• and
• a monitoring circuit to monitor consistency between the detected security-level marker and the security-level marker inserted into the audio streams.