Media Gateways

If Direct SIP is not an option because the PBX does not support the feature or has no IP PBX capabilities, a third-party device called a media gateway can be used to complete the integration. Media gateways act as an intermediary between the PBX and Lync Server to help translate traditional PBX protocols to SIP traffic, which Lync Server understands. Media gateways are produced by many vendors today and provide a wide array of integration options for businesses looking to implement the voice features of Lync Server. They typically have traditional telephony connections for T1/E1 systems on the PBX side along with network adapters to communicate with Lync Server. This type of scenario is depicted in Figure 17.7.

Figure 17.7 PBX Integration with Media Gateway

Also, as when configuring a Direct SIP trunk link, configuration of the old PBX is necessary so that it knows to route calls for specific extensions to the media gateway, which delivers the calls to Lync Server.

Depending on the media gateway and business requirements, it might be necessary to place the media gateway in front of the old PBX. This can potentially have a bigger impact on the organization, but can greatly simplify some of the routing configuration.

Some gateway vendors have software that can detect whether a user’s extension is Enterprise Voice or a legacy phone by reading specific Active Directory attributes. This might not seem like a big advantage up front, but as users are migrated to Enterprise Voice it becomes advantageous not to have to constantly change routing rules on the PBX to indicate where an extension exists. This type of integration scenario is shown in Figure 17.8 where the media gateway becomes the link to the PSTN.

Figure 17.8 Media Gateway in Front of PBX

No matter where the media gateway is located, it can provide a great deal of flexibility for organizations looking to move to or test Lync Server Enterprise Voice.