All Office Communications Server 2007 topologies support Enterprise Voice. Enterprise Voice is an implementation of IP telephony that uses Session Initiation Protocol (SIP) for signaling and Realtime Transport Protocol (RTP) for voice messaging. SIP is an industry standard, application layer signaling protocol for starting, controlling, and ending communication sessions in an IP-based network. SIP is formally described in the International Engineering Task Force (IETF) reference specification RFC 3261.

In Office Communications Server 2007, SIP is used for IM, conferencing, presence subscriptions, video, and voice messaging. SIP enables Enterprise Voice clients to provide a common user experience across all these communication modes. Enterprise Voice uses RTP for media. Like SIP, RTP is an IETF standard. It defines a packet format for carrying audio and video over IP networks.

When a user places a call from an Enterprise Voice client to a Public Switched Telephone Network (PSTN) destination, the call moves through the Enterprise Voice infrastructure as follows:

1. The user places a call from an Enterprise Voice client by dialing the number or by clicking the name of a contact in Office Communicator or Microsoft Office Outlook.
   
   
2. The Office Communications Server 2007 server normalizes the telephone number to E.164 format, and then uses the routing rules that are based on location profile and user policy to direct the call to the correct Mediation Server.
   
   
3. The Office Communications Server 2007 Mediation Server performs any necessary media translation and routes the call to the IP gateway.
   
   
4. The IP gateway applies local dialing rules or Private Branch eXchange (PBX) dialing rules and passes the call to the PSTN, PBX, or IP PBX.
   
   

The following figure illustrates a simple Unified Messaging and Office Communications Server 2007 topology.

Exchange 2007 Unified Messaging and Office Communications Server 2007 Simple Topology

Office Communications Server 2007 Enterprise Voice takes advantage of the Unified Messaging infrastructure to provide voice mail, subscriber access, call notification, and auto attendant services. These include the following:

• Phone number normalization   Phone number normalization translates number strings that are entered in various formats into a single standard format. Normalization rules specify how to convert telephone numbers that are dialed in various formats to standard E.164 format.
  
  
• Location profiles   A location profile is a named set of normalization rules that translates telephone numbers for a location to a single standard (E.164) format for telephone authorization and call routing. The name of each location profile must match the Fully Qualified Domain Name (FQDN) of its corresponding Exchange 2007 UM dial plan.
  
  
• Phone usage records   Phone usage records provide a quick, easy way to assign call permissions to users. To enable phone usage records to function correctly, you must assign a voice policy for the call to be correctly routed to the voice user.
  
  
• Voice policies   Enterprise Voice policies are collections of phone usage records that are assigned to one or more users. Most organizations will have multiple voice policies. Typically, organizations have a global policy that applies to all users and special policies that are applied on a per-user basis.
  
  
• Call routing    The core routing components for Office Communications Server 2007 are the Inbound and Outbound Routing Components, as follows:
  
  
  • Inbound Routing Component   The Inbound Routing Component handles incoming calls largely according to preferences that are specified by users on their Enterprise Voice clients. Users specify whether unanswered calls are to be forwarded or logged for notification.
    
    
  • Outbound Routing Component   The Outbound Routing Component handles calls that are placed by Enterprise Voice users either to telephone numbers that are owned and managed by the enterprise or to telephone numbers on the PSTN or mobile networks. When an enterprise user places a call, the Outbound Routing Component looks up the target number in the Realtime Communication (RTC) database. If the dialed number matches a SIP Uniform Resource Identifier (URI) for an enterprise user, the call is routed through all SIP endpoints for that user.
    
    
• Services   The setup routing for Office Communications Server 2007 installs services that provide support for voice messaging with Exchange 2007 Unified Messaging, including the following:
  
  
  • Translation Service   The Translation service is the application that is responsible for translating the dialed number into an E.164 number based on the normalization rules that are defined by the administrator.
    
    
  • Enterprise Services   Enterprise Services performs reverse number lookup on the target telephone number of each incoming call, matches that number to the SIP URI of the destination user, and sends the call to that user’s SIP endpoints.
    
    
  • User Replicator   The User Replicator extracts user telephone numbers from the Active Directory directory service and writes them to tables in the RTC database, where they are available to Enterprise Services and the Address Book Service.
    
    
  • Address Book Service   The Address Book Service normalizes enterprise user telephone numbers that are written to the RTC database to E.164 format to provision user Contacts in Communicator 2007.
    
    

To download the reference and Help documentation for Office Communications Server 2007, see Office Communications Server and Client Documentation Rollup.

The Unified Messaging server role is one of several Exchange Server 2007 server roles that you can install and configure on a computer that is running Exchange 2007. For Enterprise Voice users, Unified Messaging (UM) combines voice messaging and e-mail messaging into a single store that can be accessed from a telephone or a computer. Unified Messaging and Office Communications Server 2007 work together to provide voice mail, subscriber access, and auto attendant services to Enterprise Voice deployments, including the following:

• Voice mail   Voice mail includes answering an incoming call on behalf of a user, playing a personal greeting, recording a message, and submitting it for delivery to the user’s Inbox as an e-mail message. Notification of unanswered calls is sent to the user's Outlook and Microsoft Outlook Web Access Inboxes. The subject and priority of calls can be displayed in a way that resembles the way they are displayed for e-mail.
  
  
• Subscriber access   A subscriber is an internal business user or network user who is enabled for Exchange 2007 Unified Messaging. Subscriber access is used by users to access their individual mailboxes to retrieve e-mail, voice messages, contacts, and calendaring information. Outlook Voice Access is the new Exchange 2007 Unified Messaging feature that lets subscribers access their Exchange 2007 mailbox. Subscriber access enables an Enterprise Voice user to access voice mail, calendar, and contacts from a telephony interface. A subscriber access number is configured by the Exchange 2007 administrator on a Unified Messaging dial plan. For more information about Outlook Voice Access, see Understanding Unified Messaging Subscriber Access.
  
  
• Auto attendant   In telephony or Unified Messaging environments, an automated attendant or auto attendant menu system transfers callers to the extension of a user or department without the intervention of a receptionist or an operator. In many auto attendant systems, a receptionist or operator can be reached by pressing or saying zero. The automated attendant is a feature in most modern PBXs and Unified Messaging solutions. For more information about auto attendants in Exchange 2007 Unified Messaging, see Understanding Unified Messaging Auto Attendants.
  
  

For more information about Exchange 2007 Unified Messaging, see Unified Messaging.

There are four user scenarios in which Office Communications Server 2007 and Exchange 2007 Unified Messaging can be used together. These are:

• Call notification   User 1 calls User 2. User 2 does not answer the call. User 1 hangs up. User 2 receives an e-mail message in their Exchange 2007 mailbox that User 1 called. Call notifications are also sent when an inbound call is forwarded. User 1 calls User 2. User 2 sets call forwarding to User 3. User 1 calls User 2. The call is forwarded to User 3, and User 2 receives a call notification that the call was forwarded.
  
  
• Leave a voice mail message   User 1 calls User 2. User 2 does not answer the call. Because User 2 has not configured call forwarding to another telephone number, the call from User 1 is diverted to the voice mail for User 2. User 1 is invited to leave a voice message for User 2. The voice mail greeting that was previously recorded by User 2 is played, inviting User 1 to leave a voice message for User 2. User 2 receives a voice mail message recorded by User 1.
  
  
• Subscriber access   User 2 dials in to a subscriber access number and accesses their Exchange 2007 mailbox to check for voice messages. User 2 can listen to their e-mail or voice mail messages or access their calendar. After listening to the voice message from User 1, User 2 decides to return the call from User 1. User 2 accesses the options menu and uses the call back option to place a call to User 1.
  
  
• Auto attendant   User 1 does not know the extension number for User 2. User 1 dials in to a telephone number that is configured on a UM auto attendant. The welcome greeting and prompts that are configured on the auto attendant are played to User 1. User 1 uses the directory search feature to locate User 2 in the directory and places a call to the extension number for User 2.
  
  

  Note:

  Both subscriber access and those auto attendant services offered by Exchange 2007 Unified Messaging require users to dial specific telephone numbers. These numbers must be routable by Enterprise Voice. This means that each number must be mapped to a SIP address. Office Communications Server 2007 can route the SIP address to an address that is configured on the server that has the Exchange 2007 Unified Messaging server role installed.

Exchange 2007 Unified Messaging Active Directory Objects

Exchange Unified Messaging Active Directory objects enable Exchange 2007 Unified Messaging to integrate with the Office Communications Server 2007 Enterprise Voice infrastructure. To successfully deploy Exchange 2007 Unified Messaging in your organization, you must fully understand the relationship between each of following UM Active Directory objects and their counterparts in Enterprise Voice:

• Unified Messaging Dial Plan object   A UM Dial Plan object is the basic unit of configuration in Exchange Unified Messaging. A UM dial plan can be of the following types: Telephone Extension, SIP URI, or E.164. When Exchange Unified Messaging is deployed with Office Communications Server 2007, the dial plan type is always SIP URI. Users in a UM dial plan reach all other users in the plan by using SIP URIs or SIP addresses. Each SIP address must be unique within a given SIP URI dial plan. Each dial plan must correspond to an Enterprise Voice location profile. The name of each location profile must match the forest FQDN of the SIP URI dial plan.
  
  
• Unified Messaging IP Gateway object   A Unified Messaging IP Gateway object is a logical representation of a physical IP gateway or SIP-enabled IP PBX. The UM IP gateway object logically represents each Office Communications Server 2007 pool and front end server as if it were a physical IP gateway. Each UM IP Gateway object encapsulates configuration elements that are related to the corresponding pool or server. After a UM IP Gateway object is created, it is associated with one or more UM hunt groups.
  
  
• Unified Messaging Hunt Group object   The UM Hunt Group object associates a UM IP gateway with a UM dial plan. By creating multiple UM Hunt Group objects you can associate a single UM IP gateway with multiple UM dial plans and, therefore, with multiple Enterprise Voice location profiles.
  
  

For more information about the Active Directory objects that are included in Exchange 2007 Unified Messaging, see Overview of Unified Messaging Active Directory Objects.

The following figure illustrates the relationships between Exchange 2007 Unified Messaging objects and Office Communications Server 2007 objects.

Unified Messaging and Office Communications Server 2007 objects and their relationships

Exchange 2007 Unified Messaging (UM) combines voice messaging and e-mail messaging into a single messaging infrastructure. Office Communications Server 2007 Enterprise Voice takes advantage of the Unified Messaging infrastructure to provide voice mail, subscriber access, call notification, auto attendant services and other enhanced features that include voice messaging, Instant Messaging (IM), enhanced presence, audio-video conferencing, and e-mail into an integrated communication experience for users in your organization. Implementing these services requires integrating Unified Messaging and Office Communications Server 2007 in a shared Active Directory topology. For more information about the configuration steps that are required to correctly deploy and integrate Exchange 2007 Unified Messaging and Office Communications Server 2007, see Configuring Unified Messaging and Office Communications Server 2007.

Important:
Users who are associated with a SIP URI dial plan cannot receive incoming faxes. This is because incoming voice and fax calls are routed through a Mediation Server computer and faxing is not supported when you are using a Mediation Server.

To download the reference and Help documentation for Office Communications Server 2007, see Office Communications Server and Client Documentation Rollup.

• For more information about how to configure Unified Messaging and Office Communications Server 2007 integration, see Configuring Unified Messaging and Office Communications Server 2007.
  
  
• For more information about Unified Messaging dial plans, see Understanding Unified Messaging Dial Plans.
  
  
• For more information about Unified Messaging IP gateways, see Understanding Unified Messaging IP Gateways.
  
  
• For more information about Unified Messaging hunt groups, see Understanding Unified Messaging Hunt Groups.