User Manual V2IU 4350 Converged Network Appliance
VoIP Configuration
The 4350 provides a VoIP application layer gateway (ALG) for the SIP, MGCP, and H.323 protocols. The ALG proxies the connection between the VoIP softswitch, IP PBX or gatekeeper and voice and video devices such as IP phones, IADs or softphones. By acting as a proxy the 4350 is able to provide several important functions for IP based voice and video:
•Provide NAT/PAT services for voice and video traffic. NAT/PAT for VoIP enables you to use a single public IP address on the WAN interface of the 4350 to represent multiple private IP addresses assigned to voice or video devices on the LAN. The NAT function maps both IP address and IP port number between the public and private addresses so that all signaling and VoIP media packets are translated. A single public IP address can support up to 253 voice and video devices.
•Provide security services for voice and video traffic.
—NAT/PAT services hide enterprise LAN topology from hackers.
—The ALG acts as a “voice and video aware” firewall and ensures only authenticated voice traffic enters the enterprise LAN. This is accomplished by the dynamic provisioning of signaling and media ports for authenticated voice devices. The implementation is stateful and open ports are closed automatically when no longer required to support the voice or video call.
•Enable mobility in the enterprise LAN for voice devices. This is useful, for example, when using WiFi or moving office locations. In these instances the IP address of the voice and video device may be changed.
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