Number of packets in transit as a function of source load and routing

We study how network performance in delivering packets to their destinations is affected by routing algorithm coupled with volume of incoming traffic. We focus our study on the number of packets in transit (NPT) that is an aggregate measure of a network quality of service (QoS) performance. The NPT network performance indicator measures directly the number of packets in the network on their routes to their destinations. We carry out our study using a time-discrete simulation model that is an abstraction of the Network Layer of the ISO OSI Reference Model. This model focuses on packets and their routing. We consider a static routing and two different types of dynamic routings and different volumes of incoming traffic in the network free flow state. Our study shows that the efficiency of performance of a routing measured as an average value of the NPT time series and as a variability of this series, changes with the volume of incoming traffic among the considered routings. Thus, depending on the volume of incoming traffic it is preferable to use one type of routing over the other ones if the objective is to maintain the lowest number of packets in transit and their variability, i.e. the highest QoS network performance