VX is a service for providing RTP bridging, Audio and Video transcoding, Audio reflecting and UMTP remulticasting. It is interfaced via SOAP and is intended to be used from AccessGrid client services/shared applications.
I currently use VB/VX to participate in AccessGrid sessions over a NATed 256/64 ADSL connection. Care is still required to prevent saturation of the low bandwidth link, e.g. I transcode all the video that I'm interested in down to a single H.261 video stream at 10 frames/s and all the audio down to GSM at 8kHz which typically uses less than 200kbit/s. I then send audio as GSM at 8kHz and don't send any video. If saturation of the link does occur, VX automatically kills off services that haven't been accessed for a period of time (5 minutes in the sample configuration file).