 Communication 15, no. 5 (June 1997): 830-843. 21. H. J. Chao and Park, "Architecture Design of a Large-Capacity Abacus ATM Switch," Proceedings of IEEE GLOBECOM (November 1998). 22. .N. Giacopelli, W. 1 D. Sincoskie, and M. Littlewood, "Sunshine: A High-Performance Self-Routing Broadband Packet Switch Architecture," Proceedings of the International Switching Symposium (June 1990). Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. SWITCH FABRICS SWITCH FABRICS 291 Sunshine switch of an NXN configuration with k parallel Banyan networks, k parallel paths are avail- able for each N output. The idea is that if more than k packets/cells need access to an output during a time slot, then some of these excess cells (say, L) will be recirculated through a shared queue feedback loop of L parallel recirculating paths. They will be resubmitted to the switch at L specially dedicated input ports among the N input ports. In order to synchronize the recirculated packets with the ones that freshly arrive into the switch, an appropriate delay block is inserted into the recircula- tion feedback loop paths. In terms of its operation, a Batcher network sorts the arriving packets based on their destination address and priority. Then a trap network resolves output port contention by select- ing the k highest priority cells for each output port destination address. Finally, the k parallel Banyan networks ensure that each output port can receive up to k cells in each time slot. If more than k cells are competing for the output, the excessive ones will need to be recirculated. Another interesting approach is the helix switch design.² A hub-and-spoke topology is used in the helix switch. This speeds up the switching time by minimizing the distances over which signals must propagate. The helix switch works by sending packets forward by one segment of the ring with every 