US Patent 8234702 Cross network layer correlation-based firewalls

Lower layer traffic such as RTP streams or UDP packets that typically are not allowed through a firewall are permitted through the firewall by correlating the traffic with higher level communications already established, or messages exchanged, at a higher level layer such as for SIP sessions. Communication information and policies can be made available to the firewall, such that the firewall can allow through any packets for an active communication between authorized addresses through an authorized port. Such an approach can allow data such as streamed data and VoIP data to be passed through a firewall without weakening firewall policies.