almost nothing will be reported of Switching Systems: Architecture and Performances the important mathematical aspects of the interconnection networks topological study. A Few elements of switch fabric performance evaluation will be introduced in Appendix E. This topic has been delayed to an appendix since, even if it is fundamental for the assessment of switching machine performances, it is not needed to understand their architecture. For a deeper understanding of these topics, a much wider review of different architec- tures for space division switch fabrics with a few elements of performance evaluation can be found in [3,4], while a mathematically oriented analysis of the interconnection theory can be found in [5,6]. A space diversity switch fabric is a subsystem having N input ports and N output ports, an internal interconnection network allowing the connection of the input ports with the output ports and a control processor that can configure the fabric to realize the required mapping among the input and the output ports. A switch fabric can work in a static or in a dynamic fashion [7]. Static working is real- ized when the traffic is offered to the switch fabric in terms of semi-static connections, that is, connection with a very long duration and that has to be established without particular time constraint. In the case of semi-static working, the configuration of the switch fabric is a part of a complex connection setup process, and live traffic travels through the established connec- tion only after the completion of the whole setup process, generally closed by a functional verification of the newly established connection. Examples of such semi-static switch fabrics are those inside equipment performing cir- cuit switching, for example, at the optical transport network (OTN) layer. Dynamic working is characterized by the fact that the switch fabric continuously fol- lows a process of setup and teardown of internal connections acting in real time to satisfy streams of external requests. A typical example 