AT&T and WorldCom dive into voice over IP

By Denise Pappalardo, Network World |  Networking

AT&T is supporting its new services via gateways that hand off voice calls between its data and circuit-switched nets. While the carrier wouldn't detail how many gateways it has rolled out, Giga Information Group analyst Lisa Pierce says AT&T has 28 H.323 voice-over-IP gateways overseas and 10 in the U.S.

AT&T's voice-over-IP technology of choice is H.323, but Earley says the carrier will upgrade to Session Initiated Protocol (SIP) "when the standard is more fully accepted." That means the company's adoption of the technology could be 12 to 18 months away.

SIP and H.323 are used to send and receive voice calls between the PSTN and data networks. SIP is widely touted as the better technology because it sets up and tears down these sessions with less delay.

SIP is also the technology of choice for WorldCom, which, as expected, aired plans for its IP Communications service at the show (www.nwfusion. com, DocFinder: 2856).

IP Communications is a fully managed service that will be available to WorldCom IP VPN customers. The service will let users send domestic voice calls over WorldCom's IP network and the PSTN.

WorldCom is using SIP-enabled Cisco gateways for its new offering, but says it will support other vendors' gear in the future.

WorldCom says future editions of its service will enable customers to forego buying new and costly PBXs -- a strategy that fits with telecom service reseller AmeriVision's plans.

"We anticipate a time when we may have SIP phones and standard PBX phones on our desktops, but we'd gladly give up our PBX to converge both voice and data onto a single network," says Henry Liverpool, director of network operations at the Oklahoma City company, which is testing WorldCom's service across three sites.

WorldCom says customers will pay a flat fee per site for on-net calls and a per-second usage-based fee for off-net calls, but declined to be specific. The service is slated to roll out between March and July.

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