If you missed the first article in this series please read Implementing Outlook Voice Access with Exchange Server 2007 (Part 1).
UM Architecture
Exchange Server 2007 Outlook Voice Access relies on two important services:
- Microsoft Exchange Unified Messaging service (UMservice.exe)
- Microsoft Exchange Speech Engine service (SpeechService.exe)
The Exchange Unified Messaging service allows storage of voice and fax messages in an Exchange Server 2007 mailbox. In addition it gives users voice access to e-mails, voice-mails, calendar and contract items. If this service is not running, UM features are unavailable for all users in your organization. The Microsoft Exchange Speech Engine service relies on Microsoft Exchange Unified Messaging services. This service is responsible for:
- Dual Tone Multi-Frequency (DTMF)
- Automatic Speech Recognition (ASR)
- Text-to-Speech (TTS)
This service is essential to make Outlook Voice Access work properly. An overview of how all the services interact with each other can be found on Microsoft Technet.
Figure 1: Architecture of Exchange Server 2007 Unified Messaging (Source: Microsoft)
When taking a look at the ports required for UM functionality we will see that the Microsoft Exchange Unified Messaging service listens on TCP port 5060 in unsecured mode and TCP port 5061 when Mutual Transport Layer Security (MTLS) is used. Each UM worker process that is created listens on TCP port 5065 and 5066. When an IP-Gateway is involved and sends Real-time Transport Protocol (RTP) traffic to the Speech Engine service worker process, it or the IP PBX will use a valid higher UDP port. With Exchange Server 2007 Service Pack 1, which should be released in the last quarter of calendar year 2007, this changes a little bit: the Exchange Unified Messaging Service will listen on the TCP ports 5060 and 5061 at the same time; each UM .NET worker process will listen on port 5065 and 5067. If you configure secure communications only, it will use Port 5066 and 5068. So if you use Exchange Unified Messaging over firewalls, you should make sure that these ports are open.
Exchange Unified Messaging Processes
If you have a look at the figure below, you will see how Outlook Voice Access message flow works:
Figure 2: Outlook Voice Access Message Flow (Source: Microsoft)
Exchange Unified Messaging Connectivity
Now we have understood how the services itself interacts, the next step then will be connecting it to an SIP-Gateway.
Although there are lots of officially supported VoIP or PBX devices that Exchange Server 2007 is able to work with (Telephony Advisor for Exchange Server 2007), a lot of companies are having trouble with this implementation. Therefore, quite a few good products have been published to make things easier. In this article we will take a closer look at some of them:
- DIVA SIP Control
- Ferrari Office Master Gateway for Unified Messaging
- Asterisk Software
- Microsoft Partner UM Starter Kit
Dialogic SIP Control and Dialogic Media Gateways
A lot of companies may have still have an ISDN Server Adapter from Dialogic. This ISDN adapter may solve your problem. The software module Diva SIPControl allows you to create an 8 channel PSTN/IP Gateway (further channels are possible but you need a valid license. SIPControl translates the Call-Control-Information of the DIVA adapter into SIP messages based on RFC 3261. You can download DIVA SIP Control Software here. Here is a PDF of supported devices.
The procedure of how to deploy the DIVA SIP Control software is quite easy. After having done this, the only thing left is to connect your Exchange Unified Messaging Configuration with your DIVA SIP Control Solution.
If you are running Exchange Server 2007 Unified Messaging in virtual environments (which is completely unsupported from Microsoft at present), this solution may not help you, because you cannot directly connect your DIVA adapter to your virtual machine.
Another option is to use the “Dialogic Media Gateway for Microsoft Communications”. For more information you should check this website. This “black box” is a Linux Software based solution which can be configured quite easily and you can connect it to every virtual installation of Exchange Server 2007.
Ferrari Office Master Gateway for Unified Messaging
Ferrari Office Master Gateway is a solution from Ferrari Electronic that can be easily compared with the Dialogic Media Gateway for Microsoft Communications. It is Linux based too, and has a web interface for configuration. More information can be found here.
3CX Phone System
3CX provides a software based SIP Gateway solution. The enterprise Edition of this software provides Exchange Server 2007 Unified Messaging connectivity. It can be installed on a Windows 2000/2003/XP and Vista machines and is quite easy to configure. More information on the 3CX Phone System can be found here.
Asterisk VoIP Gateway Software
If you have a good knowledge of Linux software solutions, you can configure Asterisk VoIP. A free VMWare based installation of Asterisk can be found at Trixbox, but the configuration itself is more complex. You can find a brief description of it here.
After a successful installation of Asterisk you will be able to configure it through the Web Interface.
Figure 3: Asterisk SIPXConfig
Microsoft Partner UM Starter Kit
Another way to use Exchange Unified Messaging may be to use the VoIP Specialist Partner offer known as “UM for $1000 Starter Trial Kit”. This solution contains a compatible VoIP gateway solution and two hours of telephone assistance for the setup. For more information please check the Microsoft Exchange Team Blog.
In addition to these solutions, there are a lot more, but these ones have been well tested and work properly.
Conclusion
As you have seen in the information above, you have lots of possible ways of connecting your Exchange Server 2007 Unified Messaging Environment to your PSTN or already existing VoIP-Solution. Exchange Server itself works like a simple VoIP device; it does not contain a VoIP Gateway solution. If you do not have a PBX solution that offers this interface, you will have to choose whether you want to run a hardware-based “Black-Box” solution or a software based one using tools like Asterisk, Dialogic SIPControl, or 3CX Phone System for Windows. If you need further information, please do not hesitate to contact me.
If you missed the first part in this article series please read Implementing Outlook Voice Access with Exchange Server 2007 (Part 1)
