For many years, those of us in the analyst community had been talking about the coming migration to VOIP. While we touted the benefits, virtually everyone acknowledged that the price we would pay would be to say goodbye to the vaunted "five nines" of 99.999 percent uptime. But innovations achieved during the current VOIP revolution illustrate that VOIP systems can be demonstrably more survivable and reliable than their predecessors.
In the days of the legacy PBX, every element of the system was tightly controlled by the system vendor. A proprietary operating system running on proprietary hardware was the base for the proprietary PBX code, which drove -- well, you get the picture. Because everything was under the iron grip of the PBX vendor, software and hardware could be integrated in such a way as to maximize uptime.
At the same time the march to VOIP began, the proprietary PBX began to be deconstructed and rebuilt using system components. The way that some vendors were doing this is what led many of us to worry about the demise of reliability. Here are my observations from a Network World story, "Stay ahead of IP Telephony hype," published almost six years ago (www.networkworld.com, DocFinder: 1344):
"Vendors are deconstructing the black-box PBXs and re-implementing the features almost helter-skelter across varying combinations of open and closed hardware and software platforms. Network managers immediately need to understand the critical elements that comprise modular open PBX systems and begin understanding the finer points of each.
"For example, you'll find three vendors that refer to their systems as NT-based. While that statement would lead one to believe that the systems are directly comparable, that is hardly the case.
"One might have all the phone system hardware and call-processing logic built into a stand-alone (proprietary) box and simply use NT for system configuration and user administration. The next might have the phone hardware implemented as PCI boards that slot into the NT server and all call-processing functions implemented as NT services. A third might have all its phone hardware and processing logic built into a PCI board that simply resides in an NT Server and draws power from the bus -- not relying at all on NT for any services.
"Each of these can technically be called NT-based, but each will have radically different dependencies on NT. More importantly, the fault tolerance (or lack thereof) of NT has a dramatically different effect on each."
Times have changed. For one thing, a stable, customizable Linux core is worlds apart from using Windows NT as a platform. And even for vendors using Windows XP/2003 servers, stability is dramatically better than the "blue screen baby" that was NT.
In addition to using an IP transport for communications among PBX elements, one of the biggest changes is in untethering handsets. Here, too, is an uptime benefit. Where previously each was hardwired to a PBX port, that "wiring" is now virtual. Thus, when a primary VOIP controller becomes unavailable it is possible for a system to allow a handset to register itself elsewhere and remain functional.
However, just because these survivability and availability elements can exist, doesn't mean that they exist in every VOIP PBX. Make sure that you ask the tough questions.