Design and control of next generation distribution frames

Today, the permutation of circuits in the Main Distribution Frames (MDF), which connect the subscriber lines to POTS and to DSLAMs, is still operated manually. However, new market regulations, allowing subscribers to change network operator frequently, and the new schemes to concentrate active ADSL users into few DSLAMs during off-peak hours, adopted by network operators to reduce the energy consumption in the access network (and the related operational costs), require more advanced, reliable and faster mechanisms than human operations. Indeed, Automated MDFs (AMDF) have recently become available on the market to provide cheap and almost real-time circuit switching. Even if grounded on more than 50 years of research activities on architectures for circuit switching, the considered scenario is quite peculiar and offers new interesting technical challenges, since classical multistage strictly non-blocking networks are too expensive for the number of required ports (sometimes very large, exceeding 100,000), and rearrangeable multistage networks can interrupt temporarily active circuits, affecting in a indefinite way the performance of ADSL lines. For these reasons, we propose the design of AMDFs based on recently proposed non-interruptive rearrangeable (NIR) networks and show how to optimize the routing control to minimize the setup time of a circuit. Finally, our findings are relevant both for the theory of multistage interconnection networks, and for those companies producing, engineering and operating large AMDFs.