On LLR routing in circuit-switched networks

In the circuit-switching literature, the Least Loaded Path Routing (LLR) concept has been shown to be very simple and efficient. However, it seems that there is no unique definition for the "least busy" path, i.e., how to measure the degree of "busy" of a path. In this paper, we examine six ways of defining the least busy path and a random policy. The performance of these policies is evaluated via both simulation and analysis. Our numerical results show that all policies, include the random policy, have almost the same performance under most of the network configurations. Only under extremely low traffic load conditions, the difference between the policies becomes significant. However, the magnitude of the difference is still very small (about 0.001). Therefore, we conclude that how to select the alternate path does not affect the performance of LLR-based routing algorithms significantly when the call blocking probability is not too small. Instead, we found that the trunk reservation level affects the performance of LLR-based routing algorithms significantly.