ansiting connections are not affected. Moreover, and perhaps even more important, if the fabric does not need power feeding to remain in the current status, the power consumption in semi-static applications is due only to the switching events being smaller. On the contrary, if power feeding is needed to maintain the current status, then the overall power consumption of the fabric is an impor- tant parameter since it conditions all the designs of the equipment (see Chapters 2 and 3). In dynamic switching applications, the switching fabric is continuously involved in a fast series of state changes, never remaining in the same state for a long time. In this case the first performance parameter is the power consumption that can be on the order of several hundred watts or even kilowatts for large fabrics in datagram-oriented routers (e.g., IP routers). The switch fabric real estate is an important parameter in any application, and several times this is one of the elements that suggest the adoption of an architecture instead of another. Another quality element of a switch fabric, intimately related to its structure, is the fabric modularity. Generally, a switch fabric is designed to switch signals at a certain layer of the network; for example, an OXC is designed to switch optical channels, that is, signals at the OCh layer within the sublayering of the physical layer. On the contrary, an IP router is designed to switch IP packets, that is, layer 3 signals. Let us imagine that our switch is designed to switch layer n signals: the fabric is said to be layer k modular, with k n, if adding at the switch fabric input an aggregation of layer n signals representing a layer k signal, it can be scaled to accept the new inputs by only add- ing new elements, without the need of changing already existing elements. For example, let us consider an OXC switch fabric: it can be fiber modular (that would be optical multiplex layer modular) and wavelength modular (which means optical channel layer modular) [10,11]. The fabric is fiber 