Abstract
We consider traffic scheduling in performance guaranteed switches with optical fabrics to
ensure 100% throughput and bounded packet delay. Each switch reconfiguration consumes a
constant period of time called reconfiguration overhead, during which no packet can be
transmitted across the switch. To minimize the packet delay bound for an arbitrary traffic
matrix, the number of switch configurations in the schedule should be no larger than the
switch size $N$. This is called minimum delay scheduling, where the ideal minimum packet
delay bound is determined solely by the total overhead of the $N$ switch reconfigurations. A speedup in the switch determines the actual packet delay
bound, which decreases toward the ideal bound as the speedup increases. Our objective is to
minimize the required speedup $S_{\rm schedule}$ under a given actual packet delay bound. We propose a novel minimum delay
scheduling algorithm quasi largest-entry-first (QLEF) to solve this problem. Compared with the
existing minimum delay scheduling algorithms MIN and $\alpha^{i}$-SCALE, QLEF dramatically cuts down the required $S_{\rm schedule}$ bound. For example, QLEF only requires $S_{\rm schedule}=17.89$ for $N=450$, whereas MIN and $\alpha^{i}$-SCALE require $S_{\rm schedule}=37.13$ and 27.82, respectively. This gives a significant performance gain of 52% over MIN
and 36% over $\alpha^{i}$-SCALE.
© 2009 IEEE
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