Extending WF^2 Q+ to Support a Dynamic Traffic Mix

WF
²
Q+ is a packet scheduler providing optimal QoS guarantees at a low computational complexity. It allows a fraction of the total link capacity to be reserved to each packet flow to transmit, and it guarantees to each flow the minimum possible deviation with respect to its reserved service over any time interval. WF
²
Q+ has been defined assuming that the set of the packet flows to transmit is fixed and known at system design time. Unfortunately, such assumption is widely violated in many systems, such as Web servers or Internet routers. In this paper we propose a general scheme for extending WF
²
Q+ to support also the case where the set of packet flows to transmit is unknown beforehand and varies over time. The scheme preserves the service guarantees provided by WF
²
Q+, and allows different tradeoffs to be realized between computational complexity and system responsiveness to changing traffic mixes. After investigating the pros and cons of the possible solutions based on such general scheme, we present a simple and efficient algorithm for enabling WF
²
Q+ to support a dynamic traffic mix