Abstract   Switching networks of the type used in telephone exchanges are studied, with emphasis on a particular class of networks possessing great structural symmetry. This class contains rearrangeable networks carrying N calls with roughly 6N log 3  N contacts, and non-blocking networks with roughly 16 N (log 5  N)2 contacts; these results are the best obtainable by the methods used. We also show, by an impractical argument, that there are non-blocking networks with roughly 90N log 3  N contacts.
['Nicholas Pippenger']
On Rearrangeable and Non-Blocking Switching Networks