yahara, "Survey of Switching Techniques in High-Speed Networks and Their Performance," Proceedings of IEEE INFOCOM '90 (June 1990): 1242-1251. 9. F.A. Tobagi, T. Kwok, and F. Chiussi, "Architecture, Performance, and Implementation of a Tandem Banyan Fast Packet Switch," IEEE Journal on Selected Areas in Communication 9 (October 1991): 1173-1193. 10. X. Chen and J. F. Hayes, "Call Scheduling in Multicast Packet Switching," Proceedings IEEE ICC '92 (1992): 895-899. 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 283 Input-Buffered and Output-Buffered Switches We refer to input-buffered (or input-queued) switches when packets are buffered before the actual switching occurs. In Figure 14.5, these buffers are assumed to be implemented on the line cards. type of switch fabric suffers from HOL blocking because if any internal- or output-blocking situation arises, the single blocked packet at the head of the corresponding input queue will block all of packets that are following right behind it. In input-buffered switches, packets can only enter the fab- ric core under conditions that depend on the actual design. An arbitration module must be used in many cases to decide which one among the conflicting packets will be scheduled to traverse the fab- ric core at each time and from which input buffer. We say "in many cases" because self-routing fabrics do not need an arbitration scheme. Self-rout- ing is a very important property that some switch fabrics possess in their architectural design, such as the crossbar shown in Figure 14.3(b), where the switching element at each junction can switch to the appropriate output state based on the content of the specific cell that it receives at its input. In such a case, the routing of a specific cell to the output does not require any extra knowledge from the switch- ing element abo