Comments on ´Two-stage nonblocking bidirectional switch networks´

Raby and Banks have considered two-stage nonblocking bidirectional switching networks (see ibid., vol.24, no.6, p.362, 1988). This kind of switching network and the conditions under which such networks are strictly nonblocking were previously considered by Clos (1953). The authors have calculated in their letter the number of switches in the second stage which makes this network rearrangeably nonblocking.