Open Source VoIP on Campus, Part 2 (TechNewsWorld.com)

Along with the basic call flow architecture, perhaps the most important aspect to consider when implementing Voice over Internet Protocol telephony on a college campus is security. One standard approach to VoIP security involves limiting the full use of IP telephony to the enterprise campus, behind perimeter firewalls, with connectivity to the outside world taking place only through PSTN gateways.

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