# Out of order arrival in LCFS scenario

with LCFS, which packet/process will be serviced first in case of out-of-order arrival: the recently arrived but stale, or the previously arrived but fresh packet? E.g. at $$t = 5$$, a comparatively fresh packet generated at $$t=3$$ is waiting in the queue when a stale packet generated at $$t = 1$$ arrives. As per LCFS, we always service the most recently arrived one (here the packet generated at $$t=3$$). However, that increases the age of the system $$(5-1 = 4)$$. If we had processed the $$t = 5$$ packet, our system would have been fresher $$(5-3 = 2)$$ Here the source is the same, so as long as we have the recent information, we can discard the old information.