There are quite a few threads, comments dealing with
silverlight applications for developers, but many of them lack important information about webphone devices and background support
related to SL. I found the http://www.voip-sip-sdk.com/p_85-web-to-web-video-calls-silverlight-voip.html
link and think it's instructive enough to start a business application with
webphone based on an sdk. After testing Ozeki VoIP SIP SDK in Visual Studio 2010, but I think in VB it can also be done, I went on
using it. It sounds a bit like sticking to this sdk, but I have experinced that
the support team is really good: they
have helped me significantly in my work.