VBR Video over ATM: Reducing Network Resource Requirements through Endsystem Traffic Shaping

Transmission of variable-bitrate (VBR) video over ATM is a challenge because it combines the requirement for on-time data delivery with a bursty traffic characteristic. We focus on the role of ATM endsystems in the transmission of VBR video and examine how traffic shaping in the sender reduces the burstiness of the video stream and therefore the network resource requirements, both for video encoded in real-time and stored video. Shapers based on multiple leaky buckets are popular because they are particularly simple to implement. We present basic results on their buffer requirements and provide new, tighter bounds for their output traffic, enable efficient resource allocation as well as a significant reduction in the number of leaky buckets required. We extend the basic shaping mechanism to provide efficient shaping for stored video. Finally we compare empirically the performance of multiple leaky bucket shaping with an optimal algorithm for MPEG-1 encoded video and find under realistic conditions near-optimal performance with very few leaky buckets.