Internet Protocol (IP)-based services offer greater flexibility and ease of management. As a result, IP phones find accelerated adoption among enterprises.

Recently Infonetics Research (News - Alert) revealed that global service provider revenue from business and residential/SOHO VoIP services totaled nearly $58 billion in 2011, up 16 percent from the previous year.

The number of residential and SOHO VoIP subscribers grew 14 percent in 2011, reaching 178 million worldwide, as more households opt for no fixed-line voice connection. 

“The revenue that service providers derive from their residential and SOHO VoIP subscribers still eclipses what they get from businesses, but the business segment is growing about twice as fast, due in large part to the surging popularity of SIP trunking and hosted VoIP and UC services,” said Diane Myers, directing analyst for VoIP and IMS at Infonetics Research, in a statement.

“Adoption of VoIP services across both the residential and business segments continues to grow, and we expect strong global growth in VoIP service revenue over at least the next five years,” Myers added.

Considering the rapid adoption of hosted business VoIP and unified communications services, Infonetics Research predicts these services will more than double between 2012 and 2016 in terms of the number of seats. The growing demand for cloud-based services helped push hosted PBX and UC service revenue up 33 percent and seats up 44 percent in 2011.

Among the VoIP vendors, NTT (News - Alert) retains its leadership as the world's largest VoIP service provider in 2011, with close to 7 percent of global residential and SOHO subscribers, followed by Comcast (News - Alert) and France Télécom.

Infonetics Research, however, notes that while VoIP continues to gain popularity, legacy technologies are not going to disappear any time soon. Based on the research, Infonetics Research found that T1 lines are still the most commonly used trunking service today, and will be in 2014.

 SIP trunking is growing, according to Infonetics’ survey. Of the North American enterprises participating in Infonetics’ survey, a third use SIP trunks today, and a total of 42 percent plan to do it by 2014.

Apart from offering increased flexibility offered by IP phones, SIP trunking allows centralization of resources and cost effective voice connectivity. As a result, SIP trunking service revenue jumped 128 percent in 2011 from the previous year.

The market for SIP trunking is open to new entrants. There is no single provider dominating the landscape today, according to Infonetics.

Though incumbent providers such as AT&T and Verizon have more users currently, IP phone service providers such as RingCentral, Comcast, Bandtel, Charter, 8x8, CenturyLink, and Sprint (News - Alert) are among the many providers that enterprise evaluate for these services in the near future.

IP phone services offer lucrative opportunity for providers. Recently IP phone provider snom announced it is expanding the sales of IP phone systems to Australia and New Zealand. The company has selected Alloy Computer Products as its Gold and Platinum Partner for 2012 to supply IP phones in these regions.