
Model a Packet Switch
5-19
The queue uses a FIFO queuing discipline, which does not take into account the
destination of each packet. Note that such a model can suffer from “head-of-queue
blocking,” which occurs when a packet not at the head of the queue is forced to wait even
when its destination is available, just because the packet at the head of the queue is
aiming for an unavailable destination.
Rout Packets to Their Destinations
A core block in the packet switch example is the Output Switch block. This block sorts
arriving entities so that they depart at the appropriate entity output port based on the
entities' Destination attribute.
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