Bandwidth for High Speed Networks

Csfq with this punishment extension may be seen as a

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Unformatted text preview: to have network provide explicit per ow feedback to ingress nodes and have edge nodes police the tra c on a per ow basis. We assume this is a too heavyweight a mechanism for the Internet. CSFQ with this punishment extension may be seen as a marriage of the allocation and identi cation approaches; the di erence between 8 and our approach is largely one of the relative importance of identi cation and allocation. We start with allocation as fundamental, and then do identi cation only when necessary; 8 starts with identi cation, and then considers allocation only in the context of managing the bandwidth of identi ed ows. 5 Summary This paper presents an architecture for achieving reasonably fair bandwidth allocations while not requiring per- ow state in core routers. Edge routers estimate ow rates and insert them into the packet labels. Core routers merely perform probabilistic dropping on input based on these labels and an estimate of the fair share rate, the computation of which requires only aggregate measurements. Packet labels are rewritten by the core routers to re ect output rates, so this approach can handle multihop situations. We tested CSFQ, and several other algorithms, on a wide variety of conditions. We nd that CSFQ achieve a signi cant degree of fairness in all of these circumstances. While not matching the fairness benchmark of DRR, it is comparable or superior to FRED, and vastly better than the baseline cases of RED and FIFO. We know of no other approach that can achieve comparable levels of fairness without any perow operations in the core routers. The main thrust of CSFQ is to use rate estimation at the edge routers and packet labels to carry rate estimates to core routers. The details of our proposal, such as the estimation algorithms, are still very much the subject of active research. However, the results of our initial experiments with a rather untuned algorithm are quite encouraging. One open question is the e ect of large latencies. The logical extreme of the CSFQ approach would be to do rate estimation at the entrance to the network at the customer ISP boundary, and then consider everything else the core. This introduces signi cant latencies between the point of estimation and the points of congestion; wh...
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