An interview with Alan Percy, AudioCodes

Telecom Reseller: What is SIP trunking?

Alan Percy: Most businesses today have traditional TDM trunks that interface between their in-house telephone system (PBX) and the public switched telephone network (PSTN).   SIP trunking replaces expensive TDM trunks with newer IP-based services that use the customer’s IP connectivity and the SIP protocol to perform the same function, connecting their telephone system to the public network.

TR: What is “SIP Trunking As You Are”?

AP: The strategy allows business that are currently using Avaya or legacy Nortel PBXs to enjoy the benefits of SIP trunking with their existing equipment and investments without having to upgrade or replace them.  The objective is to implement SIP trunking now and enjoy the cost-savings immediately.  Meanwhile, the PBX can remain in place while the company goes through the evaluation process to select a new system, work out a migration plan and execute a cutover.

TR: What are the technical challenges when connecting SIP trunking to legacy PBXs?

AP: The biggest one is integrating SIP trunks with the existing TDM telephone system.  As an IP service, communications flowing through SIP trunks must be converted to a TDM format that is compatible with the specific in-house PBX or key system.  Successful conversion allows the TDM circuits from the telephone system to be moved to the SIP trunks with little or no adjustment.

TR: What equipment is needed for SIP trunking with a TDM PBX?

AP: Media gateways provide the interface between SIP trunks and legacy TDM PBXs, converting SIP signaling to TDM formats that are compatible with most legacy TDM PBXs.  The AudioCodes Mediant 1000 is an example of a modular and scalable media gateway that converts SIP to a wide range of TDM protocols and physical interfaces.  For larger installations, the Mediant 3000 is a useful choice, with scalability supporting up to 83 T1s or 3 DS3 circuits.

TR: What happens once the PBX is upgraded or replaced to fully support SIP?

AP: The Mediant media gateway continues to play an important role and can be re-purposed to provide continued connectivity to analog phones, fax machines, E911 calling or back-up TDM trunks.  The gateways can also be upgraded to an Enterprise Session Border Controller (E-SBC) via a software key installation. The E-SBC remains on premise, providing call security and interoperability between a new IP-PBX/UC system and the SIP trunks which often use dissimilar SIP formats.

Contact Alan at Alan.percy@audiocodes.com.

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