Some results/thoughts/conjectures on stability of FIFO multi-class
 queueing networks


 Karl Sigman
 Columbia University, Dept. Industrial Engineering and Operations Research
 New York City, USA


 We discuss stability of a FIFO two-station queueing network of the
 type introduced by Bramson (1994), in which the "usual" traffic
 conditions do not ensure stability. We present further results and
 simulations showing how stability can be effected by the probability
 distributions of components involved; expected values (e.g., rates)
 alone are not enough to determine stability. Whereas as this
 compliments some results of Dai, Hasenbein and Vande Vate (2001), our
 FIFO examples offer an opposite kind of result: higher variability
 can make the stability region larger (as opposed to smaller). Some
 conjectures are given too.