In queueing theory, a loss network is a stochastic model of a telephony network in which calls are routed around a network between nodes. The links between nodes have finite capacity and thus some calls arriving may find no route available to their destination. These calls are lost from the network, hence the name loss networks. The loss network was first studied by Erlang for a single telephone link. Frank Kelly was awarded the Frederick W. Lanchester Prize for his 1991 paper Loss Networks where he demonstrated the behaviour of loss networks can exhibit hysteresis.