In my other job here at Network World, I cover IP telephony, but the buzz at the VoiceCon conference this week seemed to be very much about Linux.That's because several vendors, such as Alcatel and Siemens, announced they are delivering, or will deliver, their IP PBX platforms on Linux servers. Last year at this same conference, PBX maker and Lucent spinoff Avaya made a similar announcement.\u00a0While the telecom managers attending this show probably don't deal with Linux as closely as a Web, e-mail or database server administrator would, they seem to be enthusiastic about Linux for its perceived reliability. At more than one session, users questioned the use of Microsoft servers as platforms for telephony, citing what they say is the systems' inability to stay up all the time and noting the many viruses and worms targeted at Microsoft servers.Most vendors of IP telephony gear, or IP PBXs, originally released server products based on Windows platforms, but many now offer their products on Linux and Microsoft platforms. Other users at the conference said that Windows can act as a fine telephony platform - if it is deployed only as an IP PBX without other services running on the box, such as e-mail or Web servers. Windows-based telephony servers also can interact better with Active Directory and Microsoft Outlook to create applications that converge voice and data.Linux is not currently the dominant platform among IP PBXs shipped, as the market leaders use Windows and proprietary real-time Unix software. But whichever platform winds up the tops in IP telephony, the surge in Linux popularity in this market seems to be a boon for Linux in general as a real-time, mission-critical operating system.