VoIP is hot. The Gartner Group predicts that by 2008, VoIP-enabled systems will account for some 97% of all systems sold. But all that heat can raise some issues. We resolve to answer some of the more pressing questions you might be facing.

· Can I trust Microsoft with VoIP?

· What really happens when I dial 911?

· Is VoIP safe?

· Do I need a $1,000 IP phone?

· Will SIP ever be ready for the desktop?

· How do I run my business on Skype?

1. Can I trust Microsoft with VoIP?

There is plenty of uncertainty in the corporate VoIP arena, as reflected in a recent rash of consolidations and private-equity buyouts in the market. One thing users can be plenty sure of is Microsoft's intent to become a large player in corporate IP telephony and messaging.

However, some users and industry observers question whether Microsoft server technology has the mettle for handling the real-time load and reliability requirements of corporate telephony traffic and applications. Others say the move will help accelerate the use of converged messaging and productivity applications such as presence, Web conferencing and chat.

Well known by now, the centerpiece to Microsoft's VoIP bid is Office Communications Server 2007, a real-time collaboration server which has elicited much buzz and controversy in the industry, for a product not even available for purchase yet. (The server, which is the successor to Live Communication Server 2005, is in a public beta, and is expected for general release later this year.)

"We believe, over time, [enterprise voice networks] can be totally based on Office Communications Server," said Gurdeep Singh Pall, corporate vice president of Microsoft's Unified Communications Group, in an interview earlier this year at the VoiceCon show, where Microsoft launched OCS 2007's public beta. "For now, we also want to help customers . . . who are saying, 'can I trust my voice [network] entirely to Microsoft?'"

OCS, under the hood

As with any commercial VoIP systems, such Avaya, Cisco, Nortel or Siemens, customers will be buying into proprietary Microsoft protocols and technologies if plans are made to rely heavily OCS 2007.

Microsoft is deviating from the industry standard practice of using ITU codecs for voice traffic compression and transmission — mainly, the G.711, G.722 and G.729 codecs.

"We've made several investments in our own audio and video codecs," says Paul Duffy, group product manager at Microsoft for OCS 2007.

Microsoft says part of the value in its own codecs is the ability to compensate for congested or low-bandwidth connections — such as teleworkers' dial-up lines, or broadband links without QoS. Duffy says the OCS VoIP codecs include technology that can repair poor-quality VoIP transmissions. This is done with software that compensates for packetized bits that may be lost from one end to the other during a VoIP conversation. The Microsoft codecs, working with client software on either end, injects signals and tones into the voice stream, which make the calls sound better than standard VoIP calls made over jittery links, the company says.

Additionally, Microsoft uses extensions to standard Session Initiation Protocol (SIP), which allows for more flexibility in the types of connections that clients can make among each other. (OCS supports voice, video, IM and presence across an array of devices, such as IP phones, and Microsoft Office Communicator software on PCs, cell phones and PDAs.)

OCS will also require a separate layer of server infrastructure, called Mediation Servers, in order to communicate with VoIP endpoints using ITU-standard codecs and IETF-standard SIP. These servers act as translators between an OCS 2007 server and the endpoints, as well as a gateway between an OCS server and other VoIP/public switched telephone network (PSTN) gateway hardware. Users considering a centralized deployment of OCS to support remote sites would have to install a Mediation Server in each location in order to support standard endpoints and for making PSTN calls. Microsoft recommends a full Windows 2003 server (minimum of dual-3.2GHz processors with 2GB memory) for running the Mediation Server software, as well as SQL Server 2005.