The probability distribution of the number of lost packets within a block o
f consecutive packet arrivals into a finite buffer is an important quantity
in various networking problems. In a recent paper, Cidon, Khamisy, and Sid
i introduced a recursive scheme to derive this distribution. In this paper,
we derive explicit expressions for this distribution using various version
s of the powerful Ballot Theorem. The expressions are derived for a single
source M/M/1/K queue.