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VoiceCon case studies demonstrate SIP trunking benefits

SIP trunking was a hot topic at VoiceCon this year as companies look for ways to reduce the costs and data center footprint of their voice infrastructure. A case study panel at the conference demonstrated SIP trunking benefits and challenges.

SIP trunking is gaining popularity among enterprises for its ability to reduce telephony connectivity costs and enable data center equipment consolidation, according to people who attended VoiceCon this week.    

Senior voice engineer Larry Riba recently converted his contact center outsourcing firm, Alpine Express, SIP trunking, primarily to reduce costs. With clients all over the country handing off customer service calls to his firm, he needed low-cost local numbers in multiple markets and affordable toll-free numbers in markets where he couldn't get local numbers. Riba, who sat on a SIP trunking case study panel at VoiceCon this week, said SIP trunking reduced his connectivity costs by 30%.


He also wanted to reduce his data center footprint because his company rents data center space by the rack and pays for power on top of that. SIP trunking requires much less physical equipment, since the SBCs that replace legacy media gateways can handle a much higher call volume.

"SIP trunking allows you to reduce the data center footprint," Riba said. "One rack-unit session border controller can easily handle 2,000 voice calls. You would need two full racks of [Avaya G650 Media Gateways attached to T1 lines] to handle that same volume."

What is SIP trunking?

SIP (Session Initiation Protocol) trunking is a method of connecting voice, video and other communications through an enterprise PBX to the IP backbone of a service provider. It replaces the traditional method of connecting an enterprise PBX to a carrier's PSTN network via primary rate interface (PRI) or analog circuits. SIP trunking requires an appliance, usually a session border controller (SBC) that sits between the PBX and the carrier network. An SBC governs each call or "SIP session" from beginning to end.

The University of Pennsylvania is also converting to SIP trunking, according to senior network engineer Steve Blair, who also sat on the VoiceCon panel. Blair said he has completed about 20% of a project to convert 25,000 analog Verizon Centrex lines over to a VoIP environment connected via SIP trunking. On the 5,025 lines that have been converted so far, he's seen a 40% reduction in connectivity costs.

In addition to cost savings, Blair's project was driven in part by a desire for better service reliability and operational efficiency. He said the legacy in-ground cabling infrastructure in and around the university's campus ranged from 25 to 75 years old, and cable failures were becoming more common and more expensive to repair. With students coming and going every year, moves, adds and changes (MACs) were also expensive on the legacy system, costing the school between $125,000 and $375,000 per year.

Choice of service providers is also going to be an advantage of SIP trunking at the school, Blair said. For instance, the school can have multiple carriers contributing to the trunk, but during times of low volume, it can choose to route calls over the lowest-cost provider's network.

"We want to be able to pick and choose who we get connectivity from," he said. "We're at a point where we can pick other carriers to add more capacity, and we will have the ability to pick and choose how calls are routed."

Challenges of SIP trunking

Riba, whose company uses multiple SIP trunking carriers, said most of his circuits have never had an outage, but one carrier had multiple outages early on. "We're hoping they've solved it by now, but the other circuits have been more reliable than the old TDM circuits."

He has also discovered that SIP trunks tend to time out long calls that are redirected from one employee to another and calls that are not promptly answered. He said the SIP circuit sometimes decides that the call is not active and terminates.

Blair said signaling requirements amongst his SIP carriers tends to vary in terms of how they handle addressing, adding some complexity. The billing methods and contract terminology for SIP trunking also differ from legacy services, and this requires some careful attention to detail during negotiations with carriers.

Staffing is also a major issue for Blair with SIP trunking. The university hasn't added any new staff since the project began, so in-house people are trying to learn new skills in order to help with the project. He said it has been difficult even to find contractors with the skills necessary for the project.

"Our biggest shortage is in developers," he said. "Whenever we need a feature like a bridge line appearance, that's where we spend most of our time and energy."

SIP trunking options are growing

SIP trunking services are still relatively immature, but the days of enterprises struggling with limited service provider options are starting to fade away.

Acme Packet, a leading SBC vendor, recently surveyed its customers to determine how many are actually offering SIP trunking services to enterprises. More than 134 service providers are offering the services, including 98 of the top 100 providers in the world, according to Michael Leo, Acme Packet's director of enterprise solutions marketing. Of course, these results don't say how broadly the service providers are offering services globally, but clearly they are all seeing the merits of it, despite some reluctance.

"I think there are some service providers who aren't moving as quickly," Leo said. "They see this as something that might impact their current cash flows. But, ultimately, the competition will force them to come out and offer these types of solutions to enterprises [that] are demanding the solution."

More on SIP trunking benefits

This SIP trunking primer gives you all the asics on this technology. 

This technical tip reviews the ROI of SIP trunking.

Site expert Carrie Higbie reviews what you need to know about SIP trunking benefits.

This SIP tutorial tells you everything you need to know about the protocol.

North American carriers are moving most aggressively toward offering SIP trunking, he said, driven in part by the large number of Tier 2 and Tier 3 carriers that are offering the services and pushing the Tier 1 carriers to keep up.

"The industry has come quite a ways, but it still has a ways to go," said Sorrel Slaymaker, communications architect with consultancy Unified IT Systems. "If you look at where IP telephony was 10 years ago, when the technology first came out and started making sense, companies started putting them into new offices and then slowly migrated the rest over. I see the same thing happening with SIP trunking. They're starting to do it in places where it makes more sense; and, over time, they are migrating the rest."

Let us know what you think about the story; email: Shamus McGillicuddy, News Editor

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