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Voice over IP meets VPN

What's the buzz at VPNcon in Alexandria, Va.? Well, there's plenty of noise about voice over IP (VoIP) VPNs.

ALEXANDRIA, Va. -- IP telephony is a topic that comes up wherever network equipment vendors congregate, and the VPNcon here is no exception. And service providers are getting into the act as well, touting new voice over IP (VoIP) technology over -- you guessed it -- IP VPNs.

Xavier Wartelle of NetCentrex, a company that provides network services to service providers like Genuity and France Telecom, described the VoIP VPN as "part of the multi-service VPN offering. It is a natural and logical service in the evolution of data networks toward next-generation networks."

Describing telephony VPNs (TVPNs) as "2001's killer app," Susan Rudd, president of Acorn Communications, a network design firm, explained the benefits of VoIP on VPN. The top issue is cost, she said, citing the cost savings associated with combining data and voice services, especially for smaller businesses. NetCentrex has published a savings figure of more than $50,000 per year, based on an office with 100 employees.

Rudd also described the capability for VPNs to be designed for isochronous traffic. "VPNs can now keep traffic separate by application, so asynchronous applications like packet data and image transfer will not interfere with isochronous applications like voice, streaming audio, or streaming media," she explained. With this traffic separation, VPN operators can manage quality of service to meet requirements for voice, said Rudd.

The possibilities sound exciting, but they can only be accomplished over a VPN that incorporates a private backbone. "Even using MPLS (Multiprotocol Label Switching), the public backbone will not provide toll quality voice," said Anil Chandan of Nortel Networks. Added his colleague, William Herry, "The Internet may be viable for VoIP if it is not business-critical. But for business, the public Internet surely is not adequate because of latency, jitter and loss issues."

VoIP VPNs may be a logical next step, but for now they are still an unproven technology. "It's challenging enough just doing VoIP," said Nortel's Herry. "When you implement it over a VPN, you introduce all sorts of issues that make it even more challenging. It remains to be seen how successful it will be."


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