“IP PBX to VoIP Network” Interface Specified

Business VoIP service provider Cbeyond Communications Inc. and several vendors have unveiled a draft document that proposes a series of best practices to optimize the interconnection and interoperability between IP PBXs and VoIP service provider networks.

The purpose of the document, called SIPconnect Interface Specification, is to set out a series of implementation rules that will make the disparate IP PBXs on the market work optimally with service provider SIP networks.

Joining Cbeyond in the effort are Avaya Inc., BroadSoft Inc., Centrepoint Technologies Inc., Cisco Systems Inc. and Mitel Networks Corp.

This issue is how VoIP service providers, especially those using SIP, can work with IP PBXs, all of whom use signaling that is, to some extent, proprietary, particularly for very advanced features and applications. Also, in VoIP there are options, such as what codec to use to compress voice. “What all this creates is inconsistency that makes it hard to have a standard product offering,” says Chris Gatch, chief technology officer, Cbeyond.

Today, 90 percent of Cbeyond customers use PBXs rather than hosted services. Also there is an accelerating migration to IP PBXs in enterprises. “In 2005, the majority of PBXs sold will be IP PBXs,” Gatch says, citing analyst predictions.

The new SIPconnect is a guideline for how to implement SIP, “but it goes further, because we talk about specific ways to populate SIP headers, so, for example, the user’s identity can be conveyed consistently from the PBX to the service provider.”

One effect of this is that a service provider can identify not only the enterprise customer, but each employee and what services and features the employee gets, as well as what the employee is authorized to do. Only certain employees may be authorized to make longdistance calls, for example.

Also, as enterprises migrate to IP PBXs, a standard implementation by the service provider can allow those PBXs to talk to each other more directly, SIP to SIP, over the service provider’s infrastructure. Voice calls would be of superior quality and advanced featured could be shared, particularly if customers have the same IP PBX vendor. Some features may not work if customers do not have the same IP PBX vendors, but “if we start to connect the PBXs then customers will demand that transparency,” becoming a force for standardization.

Cbeyond intends to take the SIPconnect Interface Specification to standards bodies for their adoption, as well as to the rest of the industry. “Our intention is to work with other service providers to evangelize as a standard,” says Gatch. “We need to get to the same level of consistency in VoIP as circuit-switched telephony has with PRIs.”

One of the members of the group, BroadSoft, already has developed a version of its hosted PBX software using this specification. The new version allows the features of the BroadSoft application suite, such as its CommPilot communication portal, to be used by employees who are behind a PBX.


Avaya Inc.
BroadSoft Inc.
Cbeyond Communications Inc.
Centrepoint Technologies Inc.
Cisco Systems Inc.
Mitel Networks Corp.

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