Virtual Network Function Allocation to Maximize Continuous Available Time of Service Function Chains

This paper proposes an optimization model to derive a virtual network function (VNF) allocation for time slots in sequence aiming to maximize the continuous available time of service function chains (SFCs) in a network. The proposed model suppresses service interruptions due to the unavailability of nodes and the reallocation of VNFs. Compared with conventional models, the proposed model computes the VNF allocation in a series of time slots based on the network node availability schedule, which provides information on whether each network node is available at each time slot. We formulate the proposed model as an integer linear programming problem with the goal of maximizing the minimum number of longest continuous available time slots in each SFC. The numerical results show that the proposed model improves the continuous available time of SFCs compared with existing models.