The 3-stage Clos network C(n,m,r) is considered as the most basic and popular multistage interconnection network which has been widely employed for data communications and parallel computing systems.Quite a lot of e orts has been put on the research of the 3-stage Clos network.Unfortunately,very little is known for the multirate multicast Clos network which is the most complicated case.Firstly a su cient condition for 1-rate multicast networks to be SNB is given,from which a result for 2-rate multicast networks to be WSNB can easily be gotten.Furthermore,by using a reservation-scheme routing,more specific result for 2-rate multicast networks to be WSNB can be obtained for the case of one of them exceeding 1/2.
