Emerging optical switch technologies
offer the potential for extremely high-bandwidth data switches, while
overcoming the scalability issues associated with electrical switches.
However, unlike traditional electrical switching elements, reconfiguring a set
of optical switches has a significant overhead. That is, switch
inputs become unavailable for a non-negligible amount of time when their output
is changed. For a typical cell time of 50ns (64 bytes at 10Gb/s), current
optical switch configuration times range from 0.2 to 20,000 cell times.
We refer to switches with configuration overhead as constrained switches.
In this work, we develop an architecture
and scheduling algorithms so that a constrained switch can exactly emulate a
corresponding unconstrained switch plus a fixed delay. We explore the
natural tradeoff between this fixed delay and the amount of internal speedup
required by the switch. This approach allows traditional unconstrained
switch scheduling algorithms to be applied, without modification, to a
constrained switch.
Publications:
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Towles, Brian and Dally, William J., "Guaranteed Scheduling for Switches with Configuration Overhead", INFOCOM 2002, New York, NY, June 2002. |