A study on traffic shaping, policing and conformance deterioration for QoS contracted networks

Based on the framework of shaping the traffic at the source node and policing or reshaping the traffic at further node(s), the objective of this paper is to better understand conformance consistency in QoS contracted networks. It has been pointed out in Guerin et al. (2001) that an originally conformant packet may become non-conformant at the egress in the presence of variable packet length, even though the packet is transmitted at a constant bitrate. We refer to this phenomenon by using a terminology conformance deterioration in this paper, and further analyze the probability of conformance deterioration relating to link speed and token rate. We demonstrate that the conformance deterioration could reach up to 11% in the worst case. In order to eliminate conformance deterioration, two measures, enlarging bucket size or reshaping at the policing node, are investigated by simulation. Conformance deterioration for aggregated traffic flows is also studied and compared with the results from an individual traffic flow. Both analytical and simulation results are presented in this paper.