If you're planning an upgrade to Windows XP or are buying a PC equipped with the new OS, you'll find that Microsoft has included two conferencing platforms: Microsoft NetMeeting 3.01 and Windows Messenger. Windows Messenger brings instant-messaging, file transfer, application-sharing, and voice- and videoconferencing capabilities under a common set of technologies and standards within one application, thereby simplifying the conferencing process for end users. As part of that effort, Microsoft has chosen to support the Internet Engineering Task Force's (IETF's) Session Initiation Protocol (SIP) conferencing standard rather than the International Telecommunication Union (ITU) H.323 telephony and videoconferencing standard that it used in NetMeeting. Microsoft is positioning Windows Messenger as an ultimate replacement for NetMeeting.

Unfortunately, the new protocol uses a session-setup mechanism that's incompatible with NetMeeting's H.323 protocol suite, which makes integrating an XP audio- or videoconference with NetMeeting impossible. Thus, Microsoft still includes NetMeeting with XP. However, Microsoft feels that the new protocol offers advantages that will make it a new de facto industry standard and ultimately enable a broader range of conferencing options. First, SIP works well with other Web service protocols and technologies such as XML that, combined with the API that Microsoft is making available, will make it easier for developers to integrate the voice-, data-, and videoconferencing experience into other applications. Second, third parties will also be able to develop complementary products, such as Multipoint Control Units (MCUs) and compatible clients, for other Windows versions. (At the time of writing, Microsoft reported that the company is unlikely to offer Windows Messenger separately.) Finally, unlike H.323, SIP has low resource requirements, which makes it attractive to cell phone and PDA manufacturers. This feature will become more important as high-speed wireless services emerge this year that let mobile users videoconference with office-bound associates.

For end users, the most immediate benefits come from XP itself. Microsoft has added a new audio compressor/decompressor (codec) licensed from PictureTel that delivers better audio quality with fast Internet connections than the current NetMeeting codecs can. During a conference, XP can select between the new codec's two modes or choose another audio codec as network conditions change. Microsoft has also licensed PictureTel's acoustic echo-cancellation technology, which eliminates the retransmission of received audio and doesn't require conference participants to wear headphones.

Another problem that has plagued PC-based videoconferencing is audio latency, which results in poor audio/video (A/V) synchronization at the receiving end. Some of this synchronization loss is the result of network bottlenecks, especially with low-speed Internet connections. But audio processing, particularly at the receiving end, also contributes to the problem. Although Microsoft can't do much about network latency, the company claims to have optimized the audio-processing routines in XP, thereby reducing PC-induced latency by about half.

Unfortunately, these improvements in XP won't provide benefits when you're using NetMeeting (as you might when you're conferencing with someone who's using earlier versions of Windows) because Microsoft hasn't done the NetMeeting development work to take advantage of these enhancements. Something else to consider is that Windows Messenger's video codecs support only the 176 x 144 pixel resolution, and when Microsoft will offer versions tuned for 352 x 288 pixels is unclear. NetMeeting's codecs support both resolutions.

When I tested Windows Messenger, audio quality during videoconferences was noticeably better than with NetMeeting, and the echo-cancellation technology worked extremely well. Audio synchronization was also good on my high-speed Internet connection, and I appreciated using one application rather than two to initiate the conference. Windows Messenger's application-sharing and whiteboard features worked similarly to those features in NetMeeting.

If Windows Messenger's videoconferencing capabilities interest you, verify that your computer's sound hardware has been tested with XP's echo-cancellation algorithms. Microsoft says this information will be posted on its Web site, but no specific URL was available at the time of writing.