This paper considers nonhomogeneous M(t)/M(t)/1 queues which ran model
systems such as communications networks. For such systems, bounds on
moment-generating functions and on the tail distribution of the queue
process ore obtained, These bounds are useful for characterizing the q
uality of service a system run provide to its users. An approach utili
zing the theory of differential equations is adopted. The bounds given
in this paper are tighter than those previously available. In fact, t
he bounds can he made arbitrarily tight given sufficient computational
effort.