Blocking and Non-Blocking network

In non-blocking networks the route from any free input node to any free output node can always be offered. Crossbar is an best example of non-blocking network. In a blocking network instantaneous route establishment among a pair of nodes may not be possible. There may be condition where blocking can occur. Blocking refers to the condition where one switch is necessary to establish more than one connection concurrently and end-to-end path cannot be established even if the input nodes and output nodes are free. Example of this is a blocking multistage network.