Fault-tolerant Controller Placement Model based on Load-dependent Sojourn Time in Software-defined Network

Abstract

This paper proposes a controller placement model that takes into account the load-dependent sojourn time at each controller while considering controller failures. The sojourn time is expressed by the queuing theory. The sojourn time varies depending on the amount of load arriving at each controller in the proposed model. The proposed model is formulated as a mixed integer second-order cone programming problem. The proposed model is compared with two baseline models presented in the previous research. In the baseline models, the sojourn time does not depend on the amount of load arriving at each controller. Numerical results show that the number of placed controllers becomes smaller in the proposed model than in the baseline models. This indicates that, since the sojourn time in the proposed model varies according to the amount of load at a controller, the effect of the load-dependent sojourn time at a controller tends not to become dominant over that of the propagation delay, which enables a switch to connect to more distant controller than that in the baseline models.