Office Communications Server 2007 R2 can work with existing telephony infrastructure. With Office Communications Server 2007 R2, users can not only send and receive calls with the Public Switched Telephone Network (PSTN), but can integrate with a company's Private Branch Exchange (PBX) system.
Office Communications Server 2007 R2 also combines VoIP with open standards to make the telephone menu-based part of the unified communications strategy. This extends the integration features that bridge the VoIP standards supported by Office Communications Server 2007 R2 with implementations that use older standards.
At the center of this integration is the Mediation Server role of Office Communications Server 2007 R2. It provides a single interface and uses open-standard SIP for signaling interoperability. Mediation Server takes calls from third-party IP-PBX systems or SIP/PSTN Gateways and moves them onto the network using the adaptive codec, remote user, and security models that are the basis for call setup and media with Office Communications Server 2007 R2.
The following two configurations are common Office Communications Server 2007 R2 call scenarios.
Standalone Users in an organization replace
their legacy phones with Office Communicator 2007 R2 or an Office
Communications Server 2007 IP phone. This way, users who are
configured to use Office Communications Server 2007 R2 will make
and receive calls with Office Communicator 2007 R2, and users
configured to use the PBX will make and receive calls using the
PBX. Each group continues to have a smooth calling experience,
including extension-based dialing capability. This scenario works
especially well for mobile employees. The standalone scenario can
be implemented by using either a SIP/PSTN gateway, or a direct SIP
connection to the PBX.
Co-existence An incoming call is forked
between the PBX phone and the user's logged-in Office Communicator
2007 R2 endpoints. Both the PBX phone and Office Communicator 2007
R2 co-exist on the user's desktop. The co-existence scenario is
implemented by using a specification called Dual Forking, and can
be deployed with or without remote call control (RCC).
This section covers three scenarios for calling as follows: