On deciding stability of multiclass queueing networks under buffer priority scheduling policies

TL;DR

This paper proves that determining the stability of multiclass queueing networks under buffer priority scheduling policies is an undecidable problem, highlighting fundamental limits in analyzing such systems.

Contribution

It establishes the undecidability of stability characterization for these networks under specific scheduling policies, a significant theoretical advancement.

Findings

Stability determination is algorithmically undecidable for certain queueing networks.

No constructive method exists for stability analysis under the studied policies.

The result applies to networks with finite/infinite buffers and zero service times.

Abstract

One of the basic properties of a queueing network is stability. Roughly speaking, it is the property that the total number of jobs in the network remains bounded as a function of time. One of the key questions related to the stability issue is how to determine the exact conditions under which a given queueing network operating under a given scheduling policy remains stable. While there was much initial progress in addressing this question, most of the results obtained were partial at best and so the complete characterization of stable queueing networks is still lacking. In this paper, we resolve this open problem, albeit in a somewhat unexpected way. We show that characterizing stable queueing networks is an algorithmically undecidable problem for the case of nonpreemptive static buffer priority scheduling policies and deterministic interarrival and service times. Thus, no constructive characterization of stable queueing networks operating under this class of policies is possible. The result is established for queueing networks with finite and infinite buffer sizes and possibly zero service times, although we conjecture that it also holds in the case of models with only infinite buffers and nonzero service times. Our approach extends an earlier related work [Math. Oper. Res. 27 (2002) 272--293] and uses the so-called counter machine device as a reduction tool.