Linial, London and Rabinovich and Aumann and Rabani proved that the min-cut max-flow ratio for general maximum concurrent flow problems (when there are $k$ commodities) is $O(\log k)$. Here we attempt to derive a more general theory of Steiner cut and flow problems, and we prove bounds that are poly-logarithmic in $k$ for a much broader class ofâ€¦Â (More)