May 27, 2010

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This weeks issue of Knowledge Base is written by Dialogic.
Author: Vince Connors, Product Line Manager, Dialogic


SIP Trunking with Legacy PBXs


SIP Trunking has been a hot topic for a while now. Many of the analysts are predicting rapid growth over the next several years. I was recently at the VoiceCon event in Orlando and they had an entire panel discussion on SIP Trunking. In talking with people at VoiceCon and other recent industry events it appears that SIP Trunking is moving beyond analyst projections and into actual deployments. Most of the SIP Trunking focus to this point has been on connecting the SIP Trunks to on-premise SIP equipment. While this is the most logical deployment scenario from a compatibility point of view, a high percentage of the installed base does not have SIP trunk ready communications architecture. The majority of premises have legacy PBXs with traditional TDM or hybrid-IP architectures, and given the state of the economy, these companies are not likely to throw away equipment that is in fine working order.

So how does a company take advantage of the benefits of SIP Trunking without an expensive PBX replacement or upgrade? The answer is a gateway function is required to convert the SIP stream from the SIP Trunk to a TDM stream for connection to the legacy PBX. Specifically, the gateway needs to convert the packet based VoIP media stream to traditional TDM circuit switched channels. The gateway also needs to convert the SIP signaling to a TDM protocol which is compatible with the PBX; therefore, a wide variety of protocol support is desirable to achieve interoperability with the widest variety of installed PBXs.

In addition to the gateway function, it is highly desirable to have SBC functionality to secure the enterprise edge for the connection of the SIP Trunk. Ideally these two functions, the gateway function and the SBC function, are delivered in a single easy to deploy package.

There are many devices that provide these two functions in a single box; unfortunately, in most cases these devices provide very good functionality in one area and only limited functionality in the other area. For example, an enterprise gateway is enhanced with some security features or a session border controller is enhanced with some gateway features.

What is required is a full enterprise gateway function and a full enterprise session border control function. Dialogic is in the process of developing just the product to meet these needs. Dialogic has been selling enterprise media gateways for a number of years. Dialogic has recently licensed enterprise session border control  functionality from Ingate, and Dialogic is in the final phase of development of a new enterprise border element product that combines the full functionality of the Dialogic enterprise media gateways and the Ingate enterprise session border controllers. This new product will allow companies to realize the benefits of SIP Trunking without the cost of replacing or upgrading their existing PBX.


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