Dual forking (or PBX integration) is a Voice over Internet Protocol (VoIP) scenario that enables the user to use both the PBX phone as well as Office Communicator softphone at the same time. The organization is not required to rip and replace the existing PBX system. Users can keep the same PBX phone number as before. Incoming calls to the PBX phone ring both the PBX phone as well as Office Communicator. The user has the option to answer the call from either endpoint. Outgoing calls can be placed using the PBX phone or using Office Communicator. The experience for end users is similar to providing an additional phone line from anywhere Office Communicator is available.

Dual forking enables administrators to leverage existing investments in the PBX architecture and at the same time deploy new telephony capabilities that Office Communications Server supports. Users get the benefit of outside voice without having virtual private network (VPN), click to call from Microsoft Office (Outlook, SharePoint, Word, and so on), conferencing features, and various other benefits provided by Office Communications Server’s VoIP capabilities, as described in Chapter 11.

Although dual forking leverages the existing PBX infrastructure investments, it does not provide the full capabilities of Office Communications Server that an Enterprise Voice user has, as described in Chapter 11. Some scenarios, such as call forwarding or conferencing, will not provide optimal experiences. These differences are highlighted in the rest of the chapter.