Rainbow fair queueing: fair bandwidth sharing without per-flow state
Zhiruo Cao, Zheng Wang, Ellen Witte Zegura · 2002
Fair bandwidth sharing at routers has several advantages, including protection of well-behaved flows and possible simplification of end-to-end congestion control mechanisms. Traditional mechanisms to achieve fair sharing (e.g., weighted fair queueing, flow random early discard) require per-flow state to determine which packets to drop under congestion, and therefore are complex to implement at the interior of a high-speed network. In recent work, Stoica et al., (1998), have proposed core-stateless fair queueing (CSFQ), a scheme to approximate fair bandwidth sharing without per-flow state in the interior routers. In this paper, we also achieve approximate fair sharing without per-flow state, however our mechanism differs from CSFQ. Specifically, we divide each flow into a set of layers, based on rate. The packets in a flow are marked at an edge router with a layer label (or "color"). A core router maintains a color threshold and drops layers whose color exceeds the threshold. Using simulations, we show that the performance of our rainbow fair queueing (RFQ) scheme is comparable to CSFQ when the application data does not contain any preferential structure. RFQ outperforms CSFQ in goodput when the application takes advantage of the coloring to encode preferences.