That's nearly 1,000 individual voice tunnels, to be exact, so that GST's sites could place calls directly to one another without forcing the calls to be routed through the data center. GST considered writing a script that would create router configurations for each site dynamically, but that never got off the ground because GST's lower-end Cisco 1760 routers didn't have the horsepower to support all the tunnel interfaces, Smith says. And Cisco's DMVPN (Dynamic Multipoint VPN) feature in its routers, for building the meshed VPN, doesn't yet work with Cisco V3PN. Cisco's CallManager currently supports only a hub-and-spoke environment, though Cisco plans to add support for meshed networks, too.
"Until that's complete, companies can't take full advantage of having calls sent directly between two sites for fear of oversubscribing the real-time, low-latency queue with voice calls," Smith says.
The trade-off with this approach is a bandwidth drain at the hub site, where the calls are routed initially. And the Cisco 7206 VPN routers have to decrypt, re-encrypt and then send out the voice packets arriving at the hub site. For now, though, the DS-3 pipe at headquarters is plenty, Smith says, so there's no performance problem. Still, GST would like to get its voice network fully meshed to eliminate a single point of failure.
The existing architecture is ideal for GST's data traffic, however. "The spokes are prevented from communicating with each other, so network-aware viruses can't spread rapidly throughout the company," Smith says.
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