Constrained Switch Scheduling


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.


Towles, Brian and Dally, William J., "Guaranteed Scheduling for Switches with Configuration Overhead", INFOCOM 2002, New York, NY, June 2002.

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Last updated: May 01, 2002.