InformationWeek
Defining The Business Value Of Technology
January 3, 2000
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When the quality yardstick is a circuit-switched call (with delays of 50 to 70 milliseconds), it's hard for IP to measure up unless it's routed over a private IP backbone using gateways that are instructed not to buffer traffic, Elliot says. That's why the first voice-over-IP services to emerge will use service providers' private IP backbones, which is how GTE Internetworking and Level 3 are delivering wholesale service. By over-engineering their networks--making sure there's more than enough capacity--they're able to offer quality guarantees. "We're running an end-to-end, privately managed backbone, and that lets us offer quality of service," Elliot says. "Users can't tell their call is running over an IP network."
PSINet has delivered a business voice-over-IP service for a year, also using a private IP backbone. The managed service is offered only as an add-on to its virtual private network service. "There hasn't been a firestorm of users for the service," says Philip Hedlund, director of communications products at PSINet. "But we expect the uptake to start in 2000."
PSINet is able to ensure quality by running IP voice and data traffic over a frame relay backbone. "Voice traffic is carried on separate permanent virtual circuits," Hedlund says. "Prioritization isn't necessary, and quality is toll quality."
Qwest also says IP VPN customers are the logical first takers for voice over IP. "IP VPNs will enable voice over IP to take off rapidly," says Vab Goel, VP of emerging technology at Qwest. "The first service we offer to business customers will be that kind of managed service."
But companies won't realize the true potential of voice over IP unless they also can make toll-quality calls off-network. Businesses eventually will want to communicate with their customers and suppliers using IP technology. That makes life more difficult for service providers because they can't control quality outside their own networks.
When AT&T delivers its business voice-over-IP service later this year, it will allow off-network calling, says Cliff Radziewicz, general manager of global IP telephony services at AT&T. "We will transport the traffic on our IP network as far as possible, but then it will go off-net," he says. Once that happens, AT&T loses control of the call.
That's why quality of service is so important, Radziewicz says. "We can throw bandwidth out in the network," he says. "That hides the quality sins in a voice-over-IP network. But that's not what we want."
What AT&T and other service providers really need is some way to control quality across router-based networks. Vendors such as Cisco Systems had promised that quality-of-service tools--such as differentiated services and multiprotocol label switching, which allow prioritization of packets carrying voice traffic--would be available in 1999, but delivery dates were pushed out to the second quarter this year, says John Stritzinger, director of voice and customer premises equipment services for Broadlink. "The vendors have added quality-of-service capabilities to routers, but they haven't given us the tools to manage the features," he says. Once quality-of-service features are available, vendors must make the gear interoperate, which could take several more months.
Without quality-of-service standards, there can't be any service-level agreements beyond the borders of a single carrier's network. That's going to stand in the way of widespread adoption of voice over IP by businesses, MCI Worldcom's McMurtrie says.
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Illustration by Dave Plunkett
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