In this paper we study the asymptotic behavior of the tail of the stationar
y backlog distribution in a single server queue with constant service capac
ity c, fed by the so-called M/G/infinity input process or Cox input process
. Asymptotic lower bounds are obtained for any distribution G and asymptoti
c upper bounds are derived when G is a subexponential distribution. We find
the bounds to be tight in some instances, e.g. when G corresponds to eithe
r the Pareto or lognormal distribution and c - rho < 1, where rho is the ar
rival rate at the buffer.