Conformance deterioration in QoS networks: Phenomenon, analysis and elimination

To verify conformance consistency of a previously regulated flow in QoS networks, two token buckets with identical token rate (r) and bucket size (b) are employed at the ingress and the egress nodes as the traffic shaper and policer respectively. In the presence of variable packet length, it has been found that an originally conformant packet may become non-conformant even transmitted at a constant speed. This non-intuitive phenomenon is referred to as conformance deterioration. After illustrating how conformance deterioration happens, the paper analyzes the probability of conformance deterioration for the single-hop case, both in general and for a special case. The analytical results are enriched by discussions and examples. To further understand the phenomenon, a set of simulations is carried out based on a generic multi-hop network model, for both individual and aggregated traffic flows. Finally, measures to eliminate conformance deterioration are also studied and compared in the paper.