PacketCable Delays Help TollBridge


TollBridge Technologies Inc.-a company that began as a supplier of voice-over-DSL solutions-believes delays in the development of PacketCable technology have opened an opportunity for its products in cable.

The Santa Clara, Calif.-based company has entered into an agreement with chip-supplier Broadcom Corp. for development and standards promotion of equipment that can combine the TollBridge packet-voice system with version 1.1 of the cable industry's Data Over Cable Service Interface Specification.

"This will give our systems partners and their cable-operator customers greater flexibility in delivering broadband telephony with improved time to market," said Ross Mitchell, vice president of packet telephony at Broadcom.

Like other suppliers of voice-over-digital-subscriber-line technology, TollBridge uses interfaces with the Telcordia Technologies Inc. "GR-303" standard to deliver the call-setup and feature-provisioning capabilities of class-5 circuit switches into the packet-voice domain. GR-303 is the digital-signaling protocol telcos use to extend the reach of their switches into remote locations over digital-loop carriers.

But TollBridge employs a customized version of IP (Internet protocol) packets for its voice payloads, unlike its competitors, which format their call packets to conform to the 53-byte uniform-cell parameters of ATM (asynchronous transfer mode).

By using an advanced version of frame-relay layer two, rather than IP technology, to provide support for the quality-of-service requirements of voice service, TollBridge avoids the traffic-flow problems of basic IP, while preserving the use of IP as the voice-payload format, vice president of marketing Agnes Imregh said.

"This allows us to offer a platform that addresses immediate deployment needs that are compatible with DOCSIS, while establishing a migration path to full PacketCable capabilities in the future," she added.

TollBridge is working with one unidentified MSO in preparation for a trial that's slated to begin this summer, and it has been invited for talks with several others after responding to cable RFPs (requests for proposals) on voice technology, director of product marketing Greg Hutterer said. "You'll see full commercial deployments of our platform over cable networks starting in the first quarter," he added.

While many cable companies are testing IP-voice systems designed to PacketCable specifications, many observers including Hutterer believe the technology is not ready for primetime. "You won't see commercial launches of PacketCable systems this year," he said.

TollBridge believes its solution is a better interim step to IP telephony than proprietary circuit-switch-based cable-phone systems, which is why it has made the move into cable, Hutterer said.

"Instead of spending millions of dollars for headend units that are based on the public-switched network system, operators can invest $100,000 in the TollBridge system on day one and pay as they grow after that," he added.

A single 17-inch rack-mounted TollBridge "TB200 Local Exchange Gateway" can serve 25,000 lines. A full seven-foot rack loaded with TB200 units can accommodate about 125,000 telephone lines, Hutterer noted.

Along with supporting the GR-303 interface, the platform is designed to accommodate various IP-voice-standard interfaces, including the call-control system used in PacketCable, which is designed to supplant class-5-based intelligent-network functions.

TollBridge is partnering with various manufacturers of "soft switches" to ensure tight coupling of IP-voice feature-provisioning capabilities with its gateway as the new control technologies become viable, Imregh said.

While voice-over-DSL rollouts have moved slower than some analysts anticipated, an exception is the effort involving use of the TollBridge system by Mpower Communications Corp., formerly MGC Communications Inc., which is delivering multiple-line packet-voice services to DSL business customers in five states.

"We have three more customers that are deploying the technology now," Imregh noted, adding that they aren't ready to go public with their plans.

Mpower has plans to be in 10 states by year's end, with as many as 60 cities targeted for its VoDSL service.

"From a technical standpoint, we chose the TollBridge solution because we believe it integrates smoothly with our existing and future network elements, while providing efficient end-to-end IP connectivity," Mpower vice chairman Nield Montgomery said.

TollBridge's cost model suggests that competitive local-exchange carriers can deliver eight lines of voice, together with high-speed data, over DSL to small-business customers for $300 per month, versus the $600 or more per month it costs for a similar number of voice lines and dial-up service.

But the residential market-where cable has 64 million customers-is the biggest opportunity for TollBridge, Imregh said.