1. A dynamically scalable switching fabric comprising: N first switch fabric element (FE) interfaces, each of which is configured to receive a first FE in a manner which enables said first FE to route data packets from a first input port of the first FE to a first output port of the first FE, wherein from 1 to N of said N first switch fabric element interfaces are populated with a respective first FE; M second switch FE interfaces, each of which is configured to receive a second FE in a manner which enables said second FE to route data packets from a second input port of the second FE to a second output port of the second FE, wherein from zero to M of said M second FE interfaces are populated with a respective second FE; and a reconfigurable crossbar element, connected to said N first switch FE interfaces and to said M second switch FE interfaces, which reconfigurable crossbar element is configurable to interconnect populated first and second FE interfaces.