... two VLAN tags¨ Provide NAT/Bridge forwarding route PSTN line¨ One PSTN line port VoIP Protocol Stacks¨ SIP/MGCP/H.323 signaling ... Networks¨ Multiple ways to access the Internet, such as asymmetric digital subscriber line (ADSL), digital data network (DDN), cable Modem, LAN, and WAN¨ Two ...