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Queueing

When the transaction leaves the Sampler, it flows down the arc to the FIFO Queue. It is important to note that the movement of the transaction down the arc does not advance the simulation clock. On transaction arrival at the FIFO Queue, the queue broadcasts messages down arcs asking nodes downstream if they are busy. The responses depend on the types of components that are connected to the queue and the state of the simulation when the message is received. (Details are given in the next chapter.) It is important to note that broadcasting and evaluation of these messages does not advance the simulation clock. If the queue gets a response that there is a nonbusy node, then it sends the transaction down the arc leading to that node. Otherwise, the transaction remains in the queue. When the simulation is first started, the Server is empty; when it gets the message "are you busy" from the queue, it responds "no." As a result, the queue routes the transaction down the arc to the Server.