In this paper we introduce a new concept in faulttolerance, namely the global fault-tolerance of interconnection networks. We pose the problem of characterizing the fault-tolerance of an interconnection network, modelled as an undirected unweighted graph, by a scalar, in a global manner. This can be achieved by defining an adequate metric. In this paper we propose such a metric and we apply it on two comparative analysis: for three infinite families of minimum broadcast graphs (hypercubes, recursive circulants, and Kn?odel graphs), and for five families of hypercubic graphs (butterfly, wrapped butterfly, shuffle exchange, de Bruijn, and cube connected cycles). keywords: fault-tolerance, global fault-tolerance, faulttolerance of minimum broadcast graphs.