Abstract: A system and method for traversing a firewall for a voice-over-IP session or other communication session uses four main components: a relay agent, and NAT 30A gent, a SIP proxy and a application server. The SIP proxy is located in the public network and SIP signaling messages are routed through the SIP proxy. The sever opens ports in the firewall for signaling between the SIP proxy and the relay agent behind the firewall. The application server also opens ports in the firewall for media traffic. The NAT 30A gent disposed in the path from the firewall to the Internet filters media packets and changes the public source address of the media packets to a predetermined address associated with the open media port.

Abstract: A FoIP server mediating fax communication between gateways and enterprise backend systems. The gateways are VoIP capable, connected to the PSTN and the enterprise network, and mediate between the PSTN fax call and fax over IP calls. The FoIP Server mediates between the FoIP calls and enterprise backend systems, such as message transfer agent (MTA), Customer Relationship Management CRM, document management, web services, mainframe, or a specialized application requiring faxing capabilities.