I. Introduction
Network function virtualization (NFV) techniques enable us to implement the softwarized functions of network equipment, known as virtual network functions (VNFs), on generic servers [1]. A service function (SF) chain contains a series of VNFs, such as load balancer, firewall, intrusion detection system (IDS), and contents server [2]. If the SF chains are created manually according to a legacy VNF construction procedure, it may take approximately two weeks for the successful construction of an SFC, from receiving a construction request to providing the service to the customer [3]. To continue satisfying the diverse quality-of-service (QoS) requirements despite time-varying network user behaviors and traffic volumes, the automation of SFC management is essential to shorten the network configuration/reconfiguration time and quickly rolling out a new service. The automation of the deployment and periodical adjustments of the computational resources for each network function (NF), in particular, would help in realizing efficient and stable service provisioning to customers in time-varying network conditions (e.g., resource utilization and failure occurrences).