A Measurement-based Analysis of Expedited Forwarding PHB Mechanisms

The differentiated services (diffserv) architecture defines a new framework for the support of quality of service (QoS) in IP-based networks. In this paper, we focus on the mechanisms used to implement the Expedited Forwarding (EF) Per-Hop Behavior (PHB). We analyze these mechanisms with respect to two main QoS parameters: Delay and delay variation. Within a diffserv node we study the impact of buffering and we compare the effectiveness of several different scheduling algorithms for the treatment of EF traffic. Tests are carried out in different network configurations under a range of different parameters and traffic conditions for the analysis of classification, metering, packet marking, policing and scheduling (WFQ and Priority Queuing). Our study has as its goal to explore quantitatively and in detail the operation of several different router mechanisms used to implement the EF PHB in production-class routers.