Enterprise Voice

Power, Network, or Telephone Service Outages

If there is an outage, disruption, or other degradation of the power, network, or telephone services at your location, the voice, instant messaging, presence, and other features of Office Communications Server 2007 and any device connected to Office Communications Server 2007 may not work properly.

Enterprise Voice Depends on Server Availability and Voice Client and Hardware Operability

Voice communications via Office Communications Server 2007 depend upon the availability of the server software and the proper functioning of the voice clients or the hardware phone devices connecting to the server software.

Alternative Means of Accessing Emergency Services

For those locations where you install a voice client (e.g., a PC running Office Communicator 2007 or an Office Communicator Phone Edition device), it is recommended that you maintain a backup option for users to call emergency services (911, 999, etc.) in case of a power failure, network connectivity degradation, telephone service outage, or other problem that may inhibit operation of Office Communications Server 2007, Office Communicator 2007, or the Phone Edition devices. Such alternative options could include a telephone connected to a standard PSTN line or a cell phone.

Emergency Calls and Multi-Line Telephone Systems

Please note that the use of a multi-line telephone system (MLTS) may be subject to U.S. (state and/or federal) and foreign MLTS laws that require the MLTS to provide a callers telephone number, extension, and/or physical location to applicable emergency services when a caller makes a call to emergency services (e.g., when dialing an emergency access number such as 911 or 999). Neither Office Communications Server 2007, Office Communicator 2007, nor Office Communicator Phone Edition Devices provide the callers physical location to emergency services when a caller dials emergency services. Compliance with such MLTS laws is the sole responsibility of the purchaser of Office Communications Server 2007, Office Communicator 2007, and Office Communicator Phone Edition devices.

Native IP-PBX Integration

Native IP-PBX integration refers to full coexistence between Communications Server and a PBX that natively supports SIP and IP media in a format that is interoperable with Microsoft Enterprise Voice. With native PBX integration, all users in an organization can make and receive phone calls using their existing desktop PBX phone or Office Communicator 2007.

A call is anchored on the system that originates the call. Calls from the PSTN or internal PBX phones are anchored on the PBX. Calls initiated in Office Communicator are anchored on Office Communications Server. The system anchoring a call is configured to distribute the call to the other system in addition to ringing its own endpoints. All signaling and media is terminated and normalized on the Mediation Server, which mediates both signaling and media between the two systems.

The following diagram shows a typical topology for PBX integration.

Figure 1. Native IP-PBX integration deployment option

PBX integration is possible only with an IP PBX that natively supports SIP and Internet protocol media in a form that is interoperable with Office Communications Server.

Only the latest IP-PBX models support native PBX integration and even then it is likely that a software upgrade needs to be provided by the PBX vendor. These next-generation IP PBXs are being developed by several third-party vendors (for a list of vendors, see https://r.office.microsoft.com/r/rlidOCS?clid=1033&p1=IPpbxVend) and should be available soon, if they are not already. For information about the availability and functionality, consult each vendor directly.

The following simple call scenarios demonstrate how PBX integration works.

Outside Call to Internal User

Bob calls Alice from the PSTN. The call is routed by the PSTN service provider to the enterprise PBX, which rings Alice's desktop PBX phone and also distributes the call to Office Communications Server. The PBX distributes the call by translating the incoming call alert to a SIP INVITE transaction and passing this request to the Mediation Server that connects it with Office Communications Server. In turn, Office Communications Server performs reverse number lookup on the called number to obtain all of Alice's registered SIP endpoints and, after finding them, rings all the endpoints. Alice has the choice of answering the call on whichever endpoint device is most convenient. When Alice answers the call on one of her endpoints, all other endpoints stop ringing.

Ann, a mobile worker, calls Alice from her laptop by clicking Alice's name in her Office Communicator Contacts list. The call takes the form of a SIP INVITE request. Office Communications Server performs reverse number lookup on the called number and rings all of Alice's SIP endpoints. Office Communications Server also distributes the call to the PBX, which understands SIP and therefore uses the TEL URI to ring Alice's desktop PBX phone. Once again, Alice has the option of answering the call on whichever device is most convenient.

Internal Calls Among Users

Because all internal users are enabled for both PBX and VoIP calls, the device each user chooses to place a call determines which system handles the routing. If Alice uses her PBX phone to call Dan's extension, the call is routed to Dan's desktop phone by the PBX. But the PBX also distributes the call to Office Communications Server, which routes the call to all Dan's SIP endpoints.

If Alice uses Office Communicator or a SIP phone to make the call, the SIP INVITE is sent to Office Communications Server, which routes the INVITE to all Dan's SIP endpoints and forwards it to the PBX, which rings Dan's desktop PBX phone.

Internal Call to Outside User

The routing of calls to external numbers depends on routing rules that are configured on both the PBX and Office Communications Server. Routing rules can be configure on Office Communications Server to route calls to phone numbers to the PBX or to a media gateway, if deployed.

Voice Mail

Users who are enabled for PBX integration, do not have access to Office Communications Server voice mail. Therefore, when deploying PBX integration, you should plan to keep the voice mail system on your PBX. If you eventually retire the voice mail system on your PBX, you can then disable PBX integration and reconfigure voice mail on Exchange Unified Messaging, as described in this guide.

Call Forwarding

Call forwarding can be configured on Office Communicator, the PBX phone, or both. If both are configured, both should point to the same destination.

Conferencing

Conference calls are established on the system that initiates the conference. If Office Communicator establishes a conference on the Office Communications Server A/V Conferencing Server, PBX telephones are enrolled in the conference by means of "dial out" as an outbound call leg. If a PBX user initiates a PBX conference, an Enterprise Voice user can join or be "dialed in" to the conference as a normal inbound or outbound call leg.

RCC

Remote call control (RCC) allows users to use Office Communicator to monitor and control their PBX phones. This feature is disabled for Enterprise Voice, but it remains available with PBX integration. If you have previously implemented RCC for your Office Communications Server users, there is no need to change that setting when you enable them for PBX integration.

TDM-PBX Integration Through a Media Gateway

In order to enable the coexistence scenario, in the event you have TDM-PBX infrastructure that supports forking of calls, an alternative approach is to deploy a Microsoft-certified media gateway or gateway/Mediation Server combination between Office Communications Server and the PBX. A number of these media gateways are available within the Microsoft Unified Communications Media Gateway partner program (for the current list, see https://r.office.microsoft.com/r/rlidOCS?clid=1033&p1=IPpbxVend). These media gateways interoperate with the Office Communications Server Mediation Server by means of SIP and IP media and with the PBX by means of various telephony protocols.

Figure 2 TDM-PBX integration through a media gateway

Departmental Deployment

In this scenario, Office Communications Server is deployed as the sole telephony solution for individual teams or departments, while the rest of the users in an organization continue using a PBX. This incremental deployment strategy provides one way to introduce IP telephony into your enterprise through controlled pilot programs. Workgroups whose communication needs are best served by Microsoft Unified Communications are moved to Enterprise Voice, while other users remain on the existing PBX. Additional workgroups can be migrated to VoIP as needed.

The departmental option is recommended for clearly defined user groups that share communication requirements in common and lend themselves to centralized management. This option is also attractive for teams or departments that are spread over wide geographic areas, where the savings in long-distance charges can be significant. In fact, this option is useful for creating virtual teams whose members might be scattered across the globe. Such teams can be created, amended, or disbanded in rapid response to shifting business requirements.

The following figure shows the generic topology for deployment of Enterprise Voice behind a PBX. This is the recommended topology for departmental deployment.

Figure 3. Departmental migration option

In this topology, selected departments or workgroups are enabled for VoIP. A media gateway links the VoIP-enabled workgroup to the PBX. Users enabled for VoIP, including remote workers, communicate across the IP network. Calls by VoIP users to the PSTN and to coworkers who are not enabled for VoIP are routed to the appropriate media gateway. Calls from colleagues who are still on the PBX system, or from callers on the PSTN, are routed to the media gateway, which forwards them to Office Communications Server 2007 for routing.

There are two recommended topologies for connecting Enterprise Voice with an existing PBX infrastructure for interoperability:

• Enterprise Voice behind the PBX. In this topology, all calls from the PSTN arrive at the PBX, which routes calls to Enterprise Voice users to a media gateway and calls to PBX users in the usual way. Table 1 shows the advantages and disadvantages of this topology.

  Table 1. Advantages and Disadvantages of Deploying Enterprise Voice Behind PBX

  Advantages	Disadvantages
  The PBX still serves users not enabled for Enterprise Voice.	If necessary, tie line board in the PBX must be added for gateway connection.
  The PBX handles all legacy devices.	The PBX must be configured to route Enterprise Voice numbers to the gateway.
  Users can keep the same phone numbers.

• Enterprise Voice in front of the PBX. In this topology, all calls arrive at the media gateway, which routes calls for Enterprise Voice users to Communications Server and calls for PBX users to the PBX. Calls to the PSTN from both Enterprise Voice and PBX users are routed over the IP network to the most cost-efficient media gateway. Table 2 shows the advantages and disadvantages of this topology.

  Table 2. Advantages and Disadvantages of Deploying Enterprise Voice in Front of PBX

  Advantages	Disadvantages
  The PBX still serves users not enabled for Enterprise Voice.	Existing gateways might not support desired features or capacity.
  The PBX handles all legacy devices.	It might be necessary to reset trunks from the local exchange carrier to point to the media gateway.
  Enterprise Voice users keep the same phone numbers.

  The departmental option assumes that you have an existing PBX infrastructure and intend to introduce Enterprise Voice incrementally to smaller groups or teams within your organization. The greenfield option assumes that you are considering deploying Enterprise Voice at a site without traditional telephony infrastructure.

Greenfield Deployment

Enterprise Voice provides new businesses or even new office sites for existing businesses with the opportunity to implement a full-featured VoIP solution without having to worry about PBX integration or incurring the substantial deployment and maintenance costs of an IP-PBX infrastructure. This solution supports both onsite and remote workers.

In this scenario, all calls are routed over the IP network. Calls to the PSTN are routed to the appropriate media gateway. Office Communicator serves as a softphone. RCC is unavailable in this scenario because Office Communicator Phone Edition, like Office Communicator, provides click-to-call capability. Voice mail and auto-attendant services are available through the optional deployment of Exchange Unified Messaging.

The following figure shows a typical topology for a greenfield deployment.

Figure 4. Greenfield deployment option

Call Answering

Call answering is the taking of voice messages on behalf of users whose extensions are busy or are not answered. It includes playing a personal greeting, recording a message, and submitting the message to the Exchange Hub Transport Server to be queued up for eventual delivery to the users mailbox, which is stored on the Exchange mailbox server.

If a caller leaves a message, the message shows up in the users inbox. If a caller chooses not to leave a message, a missed call notification is stored in the users mailbox. Users can then access their inbox by using the Microsoft Outlook messaging and collaboration client, Outlook Web Access, Exchange ActiveSync®, or Outlook Voice Access. The subject and priority of calls can be displayed like those of e-mail messages.

Outlook Voice Access

Outlook Voice Access enables an Enterprise Voice user to access not just voice mail, but the Exchange inbox including e-mail, voice messages, calendar, and contacts from a telephony interface. The subscriber access number is assigned by an Exchange UM administrator.

Auto-Attendant

An auto-attendant is a feature of Exchange 2007 UM that can be used to configure a phone number that outside users can dial to reach company representatives. In particular, it provides a series of voice prompts that assist an external caller in navigating a menu system. The list of available options is configured on the Exchange UM server by the administrator.