Hierarchical Fair Queueing

In this paper, we present a new queueing algorithm for networks, called Hierarchical Fair Queueing (HFQ). This shares the bandwidth between classes of users, and (within each class) between subclasses. HFQ provides a guaranteed share of bandwidth to each class, but bandwidth is not wasted when a class is inactive. Unlike the Link Sharing scheme of Floyd-Jacobsen, HFQ is provably fair, in that throughput is a close approximation to the ideal sharing scheme for an infinitely divisible resource. HFQ extends the techniques of Fair Queueing of Demers-Keshav-Shenker, to deal with a hierarchy of classes. HFQ also provides bounded delays for real time traffic. We implemented HFQ as part of a real IP gateway, and performed a number of tests which demonstrate its fairness.