The worldwide IP telephony carrier market declined sequentially in the first quarter of 2007, new research reported today.

The market drop off is characteristic of seasonal softness which follows robust year-end spending by service providers, according to the newly published report by Dell'Oro Group.

However, the study goes on to add that the market continues to enjoy double-digit year-over-year growth as service providers transition their networks to voice-over-IP technology.

"Subscriber services have emerged as the market growth driver with subscriber licence shipments climbing 36 per cent compared to the same period last year," said Steve Raab, director of IP telephony carrier research at Dell'Oro Group.

"Cable and DSL service providers bundling VoIP services with broadband, and the use of soft switches to expand traditional telephone service, all contribute to a broad-based demand for soft switches."

Raab added that Siemens and Italtel performed particularly well this quarter.

The report also reveals that equipment sales for core trunk networks continues to climb, albeit at a slower pace than the expansion now occurring at the subscriber edge of the network.