* Why clearer calls could be had if VPNs carried VoIP traffic
A reader says he has set up an IP PBX at his headquarters and wants to link it to VoIP phones in two remote offices via a VPN.
The VPN serves dual-duty to both grant access to data servers at the main site and to tunnel the VoIP traffic through firewalls without having to reconfigure them. This can reduce the risk of leaving ports open by misconfiguring the firewall.
The tunnels will also deal with network address translation (NAT) between the public IP address of the gateway and the private IP addresses of the phones. NAT is a potential barrier to VoIP that can be dealt with readily in this way. Without a VPN, a proxy will be needed to intercept signaling traffic and get it through the firewall successfully. This can be a time-consuming project.
He also wants to use VPN gear that imposes QoS on the VPN traffic and to give priority to the voice. That is key for voice quality, although much of the quality will depend on how good the Internet connection is between the branch offices and headquarters.
These are all practical reasons for combining VPN technology with VoIP, but the blend also imposes security on the VoIP signaling and the packets carrying the voice packets themselves.
If this reader chooses to use a VPN, he may actually gain in voice quality, according to testing done by Network World. Although it might seem that encryption of calls would introduce latency and possibly cause problems, the opposite proves to be true.
So he should go ahead with this plan to make his life simpler and to make for clearer calls.
