A new report from Infonetics Research reveals that half of companies it surveyed use SIP trunking today, with that number increasing to 78 percent by 2016.

The biggest drivers for the increase are to have centralized trunking, improved reliability, and speedier deployment/service changes. Barriers to adoption aren’t related directly to the service itself; some survey respondents are satisfied with their existing voice services, their service contracts aren’t up for renewal, or SIP trunks aren’t offered at their desired locations.

And while the use of T1s is declining, the older technology isn’t going away just yet.

“Businesses continue to migrate to VoIP and unified communications on their premises, but when it comes to connecting to the PSTN, legacy technologies have not disappeared,” said Diane Myers, principal analyst for VoIP, UC and IMS at Infonetics Research. “T1 lines are still the most commonly used trunking service today, though they will come down by 2016 as the use of SIP trunking grows.”

Infonetics says Cisco leads the list of installed PBX and UC manufacturers at respondents’ businesses, followed by, in alphabetical order, AT&T, Avaya, IBM, and Microsoft.

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