Definition and evaluation of cold migration policies for the minimization of the energy consumption in NFV architectures

In the Network Function Virtualization (NFV) paradigm any service is represented by a Service Function Chain (SFC) that is a set of Virtual Network Functions (VNF) to be executed according to a given order. The running of VNFs needs the instantiation of VNF Instances (VNFIs) that are software modules executed on Virtual Machines. In this paper we cope with the migration problem of the VNFIs needed in the low traffic periods to switch off servers and consequently to save energy consumption. The consolidation has also negative effects as the energy consumption needed for moving the memories associated to the VNFI to be migrated. We focus on cold migration in redundant architecture in which virtual machines are suspended before performing migration and energy consumption required for transfer of virtual machine memory is the main concern. We propose migration policies that determine when and how to migrate VNFI in response to changes to SFC request intensity and location. The objective is to minimize the total energy consumption given by the sum of the consolidation and migration energies. The obtained results show how the policies allows for a lower energy consumption with respect to the traditional policies that consolidate resources as much as possible.