First-fit scheduling for multi-stage packet switching networks

A distributed algorithm for input scheduling through a single stage or 3-stage Clos network is proposed. Similar to other scheduling algorithms, full loading is achievable, while randomization of input selection is replaced by the use of arrival timing. This distributed algorithm applies to both cases of fixed versus variable length packets. We simulated the performance for both cases. A case is made that for multigigabit per second link speed, variable length packets should be used to simplify scheduling and avoid fragmentation, with acceptable increase in delay.