Cross-border business need to expense large IDD fee on either local customer or internal staff members. Regardless of branches in countries or dialing extension to oversea staff, Voice over IP (VoIP) gateway is the definite solution to reduce the cost and supplement the inadequacy from traditional telephone system. The solution can make use of existing PBX system, telephone set, fax machine and key telephone system even the PSTN line can be directly connected to the VoIP gateway. The benefit of VoIP can be obtained immediately without additional software or complex configuration required.