Piloting SIP Trunks in the Enterprise: Just Add a New Trunk Group

Where is the low hanging fruit in the enterprise SIP trunking market? Enterprise telecom and IT managers, while eager to find ways to reduce costs, are not eager to risk security and service levels for their communications network. Trying to convince one to switch a major site entirely to a SIP trunk service offering from a competitive Internet telephony service provider is a real challenge. Sure there’s a service cost reduction, but what if the QoS is not equivalent to their PSTN service? What if there’s an outage from the ITSP, or an outage from the broadband ISP that provides the physical transport for the SIP trunk?

A pilot approach is a tried and true strategy for adopting new technology, and SIP trunking service lends itself perfectly to this approach, since one of its core value props is remote provisioning and scalability with few if any truck rolls. An enterprise can start with just about any quantity of SIP trunk channels (or sessions), and have the provider turnup more as the service proves its worth without much incremental provisioning cost.

A great way to get an enterprise started is to propose a pilot SIP “trunk group,” which is configured as a separate trunk group on the PBX (News - Alert) dial plan, and used as a least cost-routing option in the dial plan. That way the telecom manager can control which users test the SIP trunk service and for which calling patterns. It also provides a transparent failover option if the trunk group becomes unavailable for any of the previously stated conditions.

Of course the installed base of PBX systems is not always SIP trunk-ready (including many non-SIP based IP-PBXs and hybrids deployed between 2000 and 2006). That can be a significant cost hurdle for running a pilot. There’s also the issue of network edge security, NAT traversal and SIP interop that must be addressed. But these issues can be addressed with cost-effective enterprise session border controllers and enterprise media gateways. The SBC handles the network edge issues while the media gateway converts the SIP trunk traffic to a PSTN trunk emulation – essentially a drop-and-insert approach that minimizes the impact to the PBX itself. The SIP trunks are routed into the PBX through standard T1/E1 trunk ports, and PBX configuration sets up the new trunk groups.

As the SIP trunks prove their worth and reliability over time, more channels can be added, while legacy T1/E1 PSTN circuits can be retired. Whether a legacy PBX is upgraded to support a direct SIP trunk interface over time is an ROI exercise based on the cost of the upgrade vs. the cost to scale up the media gateway (and available PSTN trunk ports on the PBX). In most cases, the enterprise SBC is needed regardless of how the service is supported once inside the corporate network. Sound fruitful? IT

Bud Walder (News - Alert) is a marketing manager at Dialogic Corp. (www.dialogic.com) and is responsible for the company’s enterprise media gateway products and unified communications solutions.

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