I've recently been presenting at the "It's Time to Deploy! Microsoft Unified Communications" roadshow series sponsored by Microsoft and Windows IT Pro. The roadshow highlights the practical considerations of deploying Microsoft's unified communications (UC) technologies, including Exchange Server 2007 unified messaging (UM) and Office Communications Server (OCS) 2007. One deployment consideration is simple yet daunting: How will you connect all this software-powered goodness to the outside world? The answer depends on which PBX you have, what version of software it's running, and a host of other questions.
However, the real question on the minds of many roadshow attendees' is even simpler: What's the least expensive way for me to get started playing with this stuff? Fortunately, there are several options, depending on what you're actually trying to do. First, let's deal with the software.
To effectively test or start a pilot of Exchange 2007 UM and OCS 2007, you'll obviously need those products. Microsoft makes try-before-you-buy versions of Exchange 2007 available in three ways. First, you can download a Virtual Hard Disk (VHD) image that contains a prebuilt Exchange infrastructure that you can adapt and customize. Second, Microsoft offers a trial account hosted by Unisys that you can use to experiment without having to deploy anything yourself. Third, you can download a trial version of Exchange 2007 itself, in either the 32- or 64-bit flavor, to install on your own physical or virtual servers. If you want to build a UC test bed, this third option is your best bet, so your first step should be to build an Exchange 2007 server with the Mailbox, Hub Transport, Client Access, and UM server roles, then download and install the beta version of Exchange 2007 SP1.
Actually that's your second step—first you'll need to build a toy Active Directory (AD) infrastructure. You should, of course, use a completely independent forest for your testing, although in some environments you might be able to use a resource forest with appropriate trusts to your production forest.
Now, what about connecting Exchange to the phone system? If you already have a PBX that uses Session Initiation Protocol (SIP) over TCP, it might directly interoperate with Exchange. For example, the Mitel 3300 IP Communications Platform and Nortel's Communication Server 1000 can do this out of the box, and there are probably other systems that can as well. However, with an inexpensive FXO/FXS gateway, you can bypass the problem of how (or whether) to connect to the PBX. A Foreign Exchange Office (FXO) gateway turns regular Public Switched Telephone Network (PSTN) lines into VoIP streams, and a Foreign Exchange Station (FXS) gateway does just the opposite. These two functions are almost always combined in one device, giving you a magic box that converts ordinary analog phone lines into streams of SIP data that Exchange and OCS can use. These gateways aren't PBX systems, however, so they don't provide PBX-level features. For example, you can program them to accept calls on the analog ports and route them to Exchange or OCS, but you can't transfer calls between extensions, and your ability to redirect calls will be limited.
There are several FXO/FXS gateways on the market, as the partial list of vendors at voip-info.org shows. I say it's a partial list because it contains one popular brand that supports Microsoft UC products, AudioCodes, but omits at least two others, Dialogic and Quintum Technologies. I use an 8-port Dialogic gateway, the DMG1008. However, if you're looking for the least expensive solution, your best bet is probably a smaller unit such as the AudioCodes MP114 or the Dialogic 1004. Watch out for two-line units such as the AudioCodes MP112 that only provide FXS functionality (although you can still use them for outbound call routing with OCS 2007).
Speaking of OCS 2007, so far I've only covered the Exchange UM side of a UC test bed deployment. Next week, I'll tell you what you need to get started testing OCS 2007, but here's a hint: If you get your Exchange 2007 UM deployment up and working, you're more than halfway home!