It is an indicative measure of the point carrying capacity of a network. It is distinct as the total number of messages the network can transmit per unit time. To approximate the throughput, the capacity of the network and the messages number of really carried by the network are calculated. Essentially the throughput is only a fraction of its capacity.
In interconnection network the traffic flow among nodes may be nonuniform and it may be feasible that a certain pair of nodes handles a disproportionately huge amount of traffic. These are called "hot spot." The hot spot can act as a bottleneck and can decrease the performance of the entire network.