Non-Blocking and Blocking network

In Non-blocking networks, route from a free input node to another free output node can forever be provided. Crossbar is an illustration of non-blocking network. In a Blocking network concurrent route establishment between a pair of nodes may or may not be probable. There may be circumstances where blocking can happen. Blocking indicates to the situation where one switch is needed to set up more than one connection concurrently and end-to-end path can't be established even if input nodes and output nodes are free.  The illustration of this is a blocking multistage network.