Future of VoDSL relies on convergence

The ultimate convergence of next-generation voice and data networks will be driven firstly by the adoption of DSL (digital subscriber line) technology, Anthony Cesta, of Brampton, Ont.’s Nortel Networks’ Business Development, Emerging Services Division, told a packed crowd of attendees at last month’s Network World Live! conference in Toronto.

Cesta said the vision of a network based on the Internet model, “where bits are bits,” will only begin to come about after businesses and residential customers attain a wideband access connection to the network.

The next step of four that Cesta described involves the development of class- or quality-of-service standards, which will allow for service differentiation in the network. The third step involves developing the network to have intelligence at the edge, while the fourth and final step is convergence – where all communications become packets at the network entry point.

According to Cesta, the race to decide which technology will provide the wideband access customers need is already decided, at least in the sense that it will ultimately leverage the telephone companies’ existing and ubiquitous copper network.

Though fibre can provide significantly more bandwidth, less than five per cent of businesses operate in buildings with fibre access. To Cesta, then, the only quibble left is whether companies will end up deploying T-1 and T-3 connections or some sort of DSL-based solution over the copper network.

He said the fact that T-1 connections are usually fixed with 960Kbps dedicated to voice and 584Kbps to data is a major drawback to these connections. And price will prevent people from wanting to jump to a T-3 connection, he said.

DSL technology, which dramatically increases the digital capacity of ordinary telephone lines, has two significant advantages over T-1 and T-3, Cesta said. The first is that it uses dynamic bandwidth allocation, which allows data to “burst” rather than be relegated to using only a fixed amount of bandwidth. The second is the potential for Voice over DSL, which Cesta described as the “killer application” that will ensure the technology’s successful acceptance by customers.

Cesta said many companies have been trialing VoDSL this year, and he expects to see explosive growth in the technology’s implementation in 2001.

“The United States will be ahead of Canada” in implementing VoDSL, Cesta said. “In the U.S., there have been DSL wholesale models for some time, which we’re only now seeing in Canada.”

A bonus of VoDSL is that companies can keep their existing PBX phone sets, unlike Voice over, IP which requires IP phones, he added.

Not all agreed with Cesta’s endorsement of DSL, however.

Bill St. Arnaud, a director at Canarie, Canada’s advanced Internet development organization in Kanata, Ont., said he finds it hard to believe VoDSL will be the “killer app” that will guarantee widespread adoption of DSL.

“Look what’s driving the consumption of DSL. It’s not voice, it’s Internet,” he explained.

St. Arnaud, a big proponent of fibre deployment, said DSL connections are also affected by a customer’s distance from the telephone company’s central office.

“It’s nominally about 1.5Mbps downstream, and 400Kbps upstream,” he said of the typical asymmetrical DSL throughput speeds. “But if you’re at maximum range – 18,000 ft. – that can drop down to, you know, less than 100Kbps.”

St. Arnaud said he believes the incumbent carriers, which Nortel often supplies with equipment, are intent on pushing DSL in an effort to save money on building fibre networks.

He said that has left it up to Canada’s governments – municipal, provincial and federal – to announce their own plans to build out a broadband network. In Alberta, for example, the provincial government recently announced plans to connect every school with at least a 10-Mbps Internet connection. That capacity can only be accomplished with fibre, St. Arnaud noted.

“If you put fibre to every school, you now have fibre to every 250 homes,” he added. Using those schools as nodes, carriers can then go with high speed wireless, DSL, or fibre directly to the home or business, at speeds much higher than can be achieved by running DSL from the central office.

Mark Quigley, a telecommunications analyst with The Yankee Group in Canada in Brockville, Ont., said St. Arnaud’s vision is likely how high-speed networks will play out across Canada.

“Regardless of how you look at it, whether it’s fibre to the home or fibre directly into the business, or it’s some kind of DSL-based solution, I think at the end of the day it means fibre is going to be driven further into the network,” Quigley said.

Quigley added that he expects the incumbent carriers to eventually drive fibre all the way to their remote locations in neighbourhoods, rather than merely relying on the fibre connections between central offices.