Traffic Shaping in Aggregate-Based Networks: Implementation and Analysis

The Differentiated Services architecture allows providing scalable Quality of Service by means of aggregating flows to a small number of traffic classes. Among these classes a Premium Service is defined, for which end-to-end delay guarantees are of particular interest. However, in aggregate scheduling networks such delay bounds suffer significantly from effects that are due to multiplexing of flows to aggregates. A way to minimize the impacts of interfering flows is to shape incoming traffic, so that bursts are smoothed. Doing so reduces the queuing delay within the core of the domain, whereas an additional shaping delay at the edge is introduced. This paper addresses the issue of traffic shaping analytically by extending known Network Calculus. An equation that allows computing tight per-flow output bounds in aggregate scheduling networks is derived and a solution for shaped interfering flows is provided. We then give an overview on the shaping capabilities of current legacy routers, showing deviations of actual implementations compared to the idealized view. Finally, the evolved analytical framework is applied to an example scenario and the results are compared to corresponding measurements