Link-heterogeneity vs. node-heterogeneity in clusters

Heterogeneity in resources pervades all modern computing platforms. How do the effects of heterogeneity depend on which resources differ among computers in a platform? Some answers are derived within a formal framework, by comparing heterogeneity in computing power (node-heterogeneity) with heterogeneity in communication speed (link-heterogeneity). The former genre of heterogeneity seems much easier to understand than the latter.