By generalizing a recent result of Hong, Liu and Lai on characterizing the degree-
sequences of simple strongly connected directed graphs, a characterization is provided for
degree-sequences of simple k-node-connected digraphs. More generally, we solve the
directed node-connectivity augmentation problem when the augmented digraph is degree-
specified and simple. As for edge-connectivity augmentation, we solve the special case
when the edge-connectivity is to be increased by one and the augmenting digraph must be …