Dynamic VNF Placement to Manage User Traffic Flow in Software-Defined Wireless Networks

In a Software-Defined Wireless Network (SDWN), Network Function Virtualization (NFV) technology enables implementation of network services using software. These softwarized network services running on NFV nodes, i.e., commercial servers with NFV capability, as virtual machines are called Virtual Network Functions (VNFs). To provide services to users several different VNFs can be configured into one logical chain referred to as a Service Function Chain (SFC). While receiving services from a specific VNF located at an NFV node, a mobile user may change its location. This user may continue to receive service from an associated VNF by routing flows through a new NFV node that is closest to its current location. This may introduce an inefficient routing path which may degrade the network performance. Therefore, it is feasible to relocate the VNFs associated with the service chain of the user to other NFV nodes. To relocate VNFs optimally, we need a new optimal routing path. However, if some NFV nodes on this new path are overloaded, placing these VNFs on overloaded NFV nodes affects the performance of the service chain. To solve this problem, this paper proposes an efficient method for dynamically relocating VNFs by considering changes of a user's location and the resources currently available at the NFV nodes. The performance of the proposed scheme is evaluated using simulations and an experimental testbed for multiple scenarios under three different network topologies. Results indicate that the proposed scheme balances the load on NFV nodes, reduces SFC blocking rates, and improves the network throughput.