Using VPN (IP-Sec) is a completely different way to provide a secure VoIP solution. Using already well-established encryption tunnel technologies, a secure tunnel is created between the remote phone and the IP‑PBX.
In this example, the IP‑PBX resides behind a typical network firewall. The firewall is the border element between the Internet and LAN. The remote phone is located on a remote network across the Internet and the remote phone is establishing a VPN (IPSec) tunnel to the IP‑PBX. VPN (IPSec) is a network protocol suite that authenticates and encrypts the packets of data sent over the network. The firewall is relaying the VPN (IPSec) tunnel from the remote phone to the IP‑PBX.
In this example, the IP‑PBX resides behind a firewall, the firewall is the border element between Internet (or untrusted network zones) and Local Area Networks (or trusted zones). The firewall is a network security device and will forward the VPN (IPSec) traffic from the remote phone to the IP‑PBX.
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