hatever is the order of the requests. In other words, whatever the switch state is, a connection between a free input port and a free output port can always be established without the need of rerout- ing existing connections. Rearrangeable nonblocking: In this switch fabric, only removable block events are possible, whatever pattern of requests is presented to the switch fabric and in whatever order the requests are presented. In other words, whatever the switch state is, a connection between a free input port and a free output port can be estab- lished, but sometimes there is the need of rerouting existing connections. Switching Systems: Architecture and Performances Blocking: In this switch fabric, absolute blocking events can occur; this means that there are statuses of the switch fabric in which a free input port cannot be con- nected to a free output port due to the absence of a free path connecting input and output. Moreover, there is no way to move the already established connections to free the resources to create the wanted route. Considering traffic patterns, the ability to manage multicast connections is another char- acteristic of a switch fabric. In order to implement multicasting, the elementary node of the switch fabric must have the ability to send the incoming signal to more than one output port. This multicast ability can be present in all the switch fabric building blocks or only in a few of them. A switch fabric can be defined strictly nonblocking or rearrangeable nonblocking versus multicast traffic if, in the corresponding definitions, a unicast connection request is substi- tuted by multicast connection request, that is, a request to send the signal incoming from a free input port to a set of free output ports. Another important property that a switch fabric could have is the property of maintaining the state if the power feed is switched off; in this case, the switch fabric is called latching. This means that in case of power blackout, due to either a local fault or some other rea- son, tr