An IP-based VTC system implementing a single CODEC supporting conferences on multiple networks having different classification levels (i.e., unclassified, SECRET, TOP SECRET, TS-SCI) must support Periods Processing by connecting the CODEC to one network at a time, matching the classification level of the session to the classification level of the network.

Connecting to networks of different classifications simultaneously incurs the risk of data from a higher classification being released to a network of a lower classification, referred to as a "spill". It is imperative that networks of differing classification levels or with differing handling caveats not be interconnected at any time. Separation in a multinetwork VTC system is maintained by the use of an A/B, A/B/C, or A/B/C/D switch that meets requirements for channel isolation, or by manual connection of the CODEC to one network at a time.