Can ABR service replace VBR service in ATM networks

The new Available Bit Rate (ABR) service with explicit rate flow control and a minimum rate guarantee (MCR) provides such a powerful service option that it may well be more effective for video and voice than the Variable Bit Rate (VBR) service currently defined for real time use. An MPEG compressed video signal can encode at any rate the network requests down to a defined minimum. If we set the Minimum Cell Rate (MCR) to the lowest rate, and adjust the coding rate dynamically to the network feedback, the resultant video is extremely high quality and the channel is used at over 95% utilization. On the other hand, if VBR service is used, the codec runs at its own rate and the network must allocate far more bandwidth than the average used due to the possibility of many such signals peaking at once. With VBR, the utilization for MPEG video is from 30-60%. Thus, ABR may be considerably less expensive for video with little or no loss in quality.