Letter to the Editor—Priority Traffic with at Most One Queuing Class

Load-service relations are derived for three types of preemptive priority traffic, in which a call of any class displaces a call of a lower class (the lowest one present, if any) with the single exception in (b) below. These may be briefly characterized as follows (a) calls of all classes are cleared when blocked, (b) calls of the highest class queue, calls of all other classes are cleared, and calls of the second highest class are not displaced by preemption, and (c) calls of the highest class queue and those of all lower classes are cleared. [Doctrine (b) without its last condition ]