M|G|1 priority scheduling with discrete pre-emption points:: on the impacts of fragmentation on IP QoS

Closed form solutions for the M\G\1 queuing system with priority scheduling are known from current theory. These comprise of non-preemptive and pre-emptive systems. However, a number of systems exist that cannot be described with sufficient precision by the models mentioned above. Among these are systems that offer reduced pre-emption capabilities that allow for pre-emption only at a number of discrete interruption points in time. Such systems occur in communication networks, if priority queuing with link level fragmentation is used. In this paper we extend the two known models by a more general M\G\1 queuing model with priority scheduling and pre-emption at discrete interruption points. This model also covers the two special cases of pre-emptive, and non-pre-emptive priority scheduling. A closed form analytical solution is provided for the mean waiting time, the mean service completion interval, and the mean response time. Results are given on the impacts of link level fragmentation on Internet Quality of Service. (C) 2004 Elsevier B.V. All rights reserved.