An SLA-Aware Network Function Selection Algorithm for SFCs

5G is expected to support diverse services with different service requirements. Network Slicing (NS) is a new paradigm which aims to assign different services to a logically dedicated network. A network slice can host multiple services of similar requirements. The traffic flows belonging to a service are processed by a sequence of Virtual Network Functions (VNFs) which form a Service Function Chain (SFC). To utilize the resources efficiently, an operator can share the same VNF instance for multiple SFCs. The CPU utilization of a VNF instance can increase when new flows are accepted. This may increase the VNF delay which can result in the violation of SLA requirements of the existing flows. Therefore, an efficient VNF selection to form SFCs while meeting the SLA requirements is an important aspect that needs to be addressed. In this paper, we address the VNF selection problem for an SFC with the goal of supporting more number of SFCs by considering the dynamic variation of VNF delay. We develop a heuristic algorithm namely PENDANT which considers the effect of CPU utilization on VNF delay and migrates flows to other VNF instances to avoid SLA violations.