There are few environments, especially at an Enterprise scale, that do not have a multitude of vendors supplying solutions. And, quite often, these solutions may not work together, or inter-operate, without either vendors working on the issue or the team finding a third-party solution. Figure 14-6 depicts the current telephony infrastructure in the Chicago site at Litware, Inc.

Figure 14-6. Current PBX telephony system at Litware, Inc.’s Chicago location

Consultation with the PBX vendor may prove that the Office Communications Server can be configured to communicate directly with the PBX by using direct SIP, but will require an upgrade of the hardware to be IP-enabled as well as configuration changes to the upgraded IP PBX. This leaves Litware with two options for enabling Enterprise Voice at the Chicago site.

In the first option, Litware could decide to keep the existing PBX system and enable interoperability with Office Communications Server using Remote Call Control or dual forking. This configuration requires deploying a media gateway that bridges between the PBX and a Mediation Server, as shown in Figure 14-7. This does add additional costs but would introduce the telephony team and the server administration team to the components that they may ultimately be responsible for. Users would also be able to benefit from the new telephony experience that Office Communications Server offers while maintaining the comfort of their existing PBX phone.

Figure 14-7. Integration of Office Communications Server to the existing PBXs using media gateways and Mediation Servers

In the second option, Litware would upgrade the existing PBXs to IP PBXs, allowing the upgraded IP PBXs to connect directly with Office Communications Server. This would eliminate the need for the media gateway. However, the Mediation Server will still be required. Figure 14-8 shows the configuration of the proposed upgrade to IP PBXs, and Office Communications Server would appear logically.

Figure 14-8. Conceptual view of the upgraded IP PBXs with Office Communications Server 2007 R2 Mediation Servers and potential clients

After discussions with the stakeholders, project management decided that the existing PBXs should be upgraded to IP PBXs and connected to Office Communications Server using Direct SIP. The PBX vendor is currently not ready to ship the IP PBX solution. Litware, Inc. will continue to use the PBXs as they currently are, implement Option 1, and move to implement the IP PBX upgrade once the product is released.

Both options are actionable and are valid for use in Litware’s environment. Once the proof of concept is completed in Chicago with 5 percent of the site population, the rest of the site will be upgraded; and the other locations will be upgraded as well. The important discovery that Litware has made is that they actually have two paths for delivering a comparable service. Either option can be implemented in any of Litware’s sites, lowering costs and maximizing effectiveness for users and enhancing the overall experience for all.