Telephony servers now emerging are set to transform enterprise phone systems into just one more service provided through the corporate data center.InfoWorld (Telecom): Siemens moves to merge telephony, data center
This InfoWorld article was actually prompted by Siemens' release of its HiPath 8000 softswitch, but does a good job talking a little bit about the convergence of IP communications, XML, and web services. Siemens also talks about being more open than the offerings from other vendors in the past, certifying solutions other than its own to run on the platform.
Not surprising, since the platform is a pair of IBM XSeries 345/346 servers running SuSE Linux. And yet, pricing at $300/user for 12,000 users?! Granted, voice platforms are more complicated than let's say a webserver, but I have to think that open source systems could be lower cost than this.
With the sweeping realization that voice is "just bits", large corporations are moving more of their infrastructure into their data centers, and it looks like there will be both open and proprietary systems there to meet them.