SIP-trunking services have been around for a while, but their pervasiveness among enterprises has been hampered by interoperability concerns. Early results from Nemertes' Advanced Communications Services research show 65% of organizations are using or plan to use SIP-trunking services somewhere in their network. I expect that penetration to increase with a new the SIP Forum's ratification of Version 1.0 of the SIPconnect standard.

The standard defines interoperability between IP telephony systems and service-provider SIP systems.

This improvement will help organizations more effectively operate their branch office infrastructure. As they implement IP telephony in their locations, they can use SIP trunking to help communicate with non-IP locations.

SIP-trunking services provide hosted gateways between IP telephony systems and the public-switched telephone system. The services offer features that are appealing to the distributed enterprise.

For example, they can reduce costs by eliminating PSTN trunks. They can dynamically allocate bandwidth without needing to reserve individual 56Kbps channels for each voice call.

Additionally, they can leverage a distributed staff by enabling dynamic call routing. IT managers can set policies that route calls based on location, time of day, or expertise. They can do this today, of course, but by moving the routing logic to the carrier network, they reduce their internal call-routing management.

Finally, they can expand their virtual presence by creating “virtual” local phone numbers. This feature is particularly useful for small and midsize businesses that want to expand their global “presence” by providing local access numbers in non-local cities. For example, a business with offices in New York can establish local numbers in other cities around the globe. When someone calls the remote locations, they are routed to the carrier’s network via its PSTN gateway and then sent to the customer’s internal phone system for termination.

As IT staffs develop their network architecture, SIP trunking is becoming a more viable option.

Robin Gareiss is executive vice president and senior founding partner of Nemertes Research. Click  here for the newsletter archive.