Defining Exchange Unified Messaging architecture
In this excerpt from "Microsoft Exchange Server 2007: The Complete Reference," you'll get an introduction to the Unified Messaging for Exchange 2007 architecture and learn about its three major components: the Unified Messaging Service, Unified Messaging Worker Process, and the Speech Engine Services. You'll also read about two executable files that are responsible for voice and fax message access and DTMF, ASR, and TTS, respectively.
Exchange Unified Messaging architecture
The Exchange Unified Messaging architecture is quite different from the legacy voicemail systems. There are three major components in the architecture: Microsoft Exchange Unified Messaging Service, Unified Messaging Worker Process, and the Speech Engine Services. Figure 3 details the architecture.
Figure 3 Exchange 2007 Unified Messaging architecture
In terms of running processes on the UM server, the architecture is based on two executables: UMservice.exe and SpeechService.exe. The executable UMService.exe spawns UMWorkerProcess.exe and is responsible for voice and fax message access and storage in the Exchange 2007 mailbox store.
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SP1: Service Pack 1 improves the security of the UM architecture by extending support for secure connections. |
Microsoft Unified Messaging cannot communicate directly with a legacy PBX. It is necessary to use an IP gateway device between the Unified Messaging server and the legacy PBX. However, if an organization has deployed an IP PBX, there is a chance an IP gateway is unnecessary if the IP PBX is compatible with the Exchange 2007 Unified Messaging server. Figure 4 shows how the Exchange Unified Messaging server integrates with both types of PBXs. Note that the connection from the IP PBX to an IP gateway device is necessary if Exchange 2007 does not support the IP PBX.
Figure 4 Exchange 2007 Unified Messaging PBX integration
The "Inbound call handling" and "Retrieving messages with OVA" sections illustrate how the IP PBX and the legacy PBX integrate with the Exchange 2007 Unified Messaging server.
Inbound call handling
The inbound call handling steps performed by the UM server role are as follows:
- An external caller dials a UM user's phone number on the PSTN.
- The UM user's office phone rings for a preset number of times.
- The legacy PBX routes the call to the IP gateway or the IP PBX establishes a direct VoIP connection to UM server.
- The IP gateway identifies an available UM server. Once the UM server is determined, the voice input is converted to VoIP: SIP and RTP.
- The UM server queries AD to determine the mailbox server of the recipient by filtering for a user with the extension specified by the caller.
- The UM server plays the user's greeting, encodes the voice message, and attaches it to an email.
- The UM server sends the message to a Hub Transport server.
- The Hub Transport server in the same Active Directory site as the user's mailbox server submits the voicemail/email to the database where the user's mailbox data is stored.
Retrieving messages with OVA
The process to retrieve a voice mail from the UM server role is as follows:
- The UM user dials a preconfigured OVA call-in number from the PSTN.
- The legacy PBX routes the call to the IP gateway or the IP PBX establishes a direct VoIP connection to UM server.
- OVA requests the user's extension number and PIN.
- OVA queries AD to determine which mailbox database belongs to the UM user and to validate the PIN.
- The UM server waits for input from the user. When a request for a message is made, the appropriate menu of options is presented.
- If the user requests that the message is read, the Text-To-Speech engine will read the mail header and content (it cannot read the attachments to the email).
- The UM server retrieves the message from the Mailbox server role and plays the voice message.
For more details on PBXs, see "PBX and IP Gateways vs. IP PBXs" later in this excerpt.
Microsoft Exchange Server 2007 Unified Messaging for administrators
Home: Introduction to Unified Messaging on Exchange 2007
Part 1An intro to voice systems for Exchange administrators
Part 2: Unified Messaging features in Exchange Server 2007
Part 3: Defining Exchange Unified Messaging architecture
Part 4Deploying Unified Messaging servers on Exchange Server 2007
Part 5: Comparing VoIP PBX solutions for Unified Messaging
Part 6Integrating Unified Messaging servers with a VoIP solution
Part 7: Creating a Unified Messaging Dial Plan
Part 8: Configuring a Unified Messaging IP gateway
Part 9: Mailbox policy configuration for Unified Messaging
Part 10: Creating and assigning a Unified Messaging hunt group
Part 11: Dialing rules and restrictions for Unified Messaging users
Part 12: Assigning Unified Messaging dialing rules to a mailbox policy
Part 13: Executing Unified Messaging grammar generation
Part 14: Enabling Unified Messaging mailboxes and users
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This chapter excerpt from Microsoft Exchange Server 2007: The Complete Reference, by Richard Luckett, William Lefkovics and Bharat Suneja, is printed with permission from McGraw-Hill Osborne Media, Copyright 2008. Click here for the chapter download or purchase the book here. |