Convergence between voice and data networks is happening far slower than expected, according to a senior executive at Siemens, which has itself made a high-profile entry into the voice over IP market.

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Volker Jung, member of the corporate executive committee of Siemens AG, told an audience of chief executives at a Wall Street Journal seminar in London today that currently just 0.5 per cent of voice traffic is flowing over IP networks.

He said this figure stands in stark contrast to expectations made three years ago that 50 per cent of voice traffic would be carried over data networks. Jung blamed data networking players, such as Cisco, which he said had failed to understand the market.

"It was predicted that voice would be eaten by data but this ignores that fact that people want to speak over the phone," he said.

Jung conceded that convergence would happen, but argued it would only be possible when the security, availability and quality of service functions delivered by data networking products improves. This is something he argued that telecoms equipment suppliers - rather than data networking players - are best positioned to supply.

"It is easier to take a reliable system and deliver it in a less reliable form," he said. "Data systems are generally 10 times less reliable than voice systems and quality of service standards are generally too low."

Last month at Networld Interop in Las Vegas, Siemens unveiled a number of products designed to take its current telephone-line based enterprise private branch exchange (PBX) systems into the internet Protocol (IP) world.

The launch included the HiPath 5000 family of IP PBX systems, which Siemens has now renamed communication servers; the HiPath AllServe device, which enables multiple offices to share network applications; and a MobileOffice suite aimed at teleworkers and remote call centre agents.

Stan Schatt, research director at Giga Information Group, agreed that convergence technology needs to improve, particularly in its ability to deliver quality of service, before companies will commit to it.

"Convergence doesn't make commercial sense for large organisations yet because they are able to negotiate good deals with their telecommunications provider," said Schatt.

"The technology does not scale to very large enterprises. There is use within SMEs (small and medium-sized enterprises) and a lot of experimentation, but nothing on a grand scale."