If you've tried to listen to any of the radio stations now broadcasting on the net, perhaps using RealAudio, you'll have discovered one of the main drawbacks of today's Internet. It is not designed to transmit real-time live broadcasts, or time-sensitive data. The Internet is good at getting the data to you somehow, perhaps with parts slightly delayed or out of order, and is very good at piecing together that data. But if the aim is to get a stream of data to you without skips or jumps and in the correct sequence, then it can fail. Quality of Service (QoS) tries to address this by prioritising real-time traffic over less time-dependent data. This still doesn't guarantee against congestion, but it can speed important data through the bottlenecks. QoS is still at the experimental stage, but may become standard as the Internet evolves.