On-Demand State Migration Protocol for Elastic IMS Cloud Components

In the context of Network Functions Virtualisation one of the key feature we have to deal with is elasticity, namely the capability of a Virtualised Network Function to be designed so as to work in dynamic clusters. Usually, to balance the incoming load, a load-balancer is put in front of the cluster; however, because most components embed stateful logic, we need mech- anisms to track state in order to preserve functionalities. Many solutions to this problem have been proposed; in particular, for IP Multimedia Subsystem deployments, various designs that employ stateless components along with elastic Database solutions. In the following we show how this kind of solution could impact performance, and present a different approach, namely by using an application-aware, stateful load-balancer along with a simple state migration protocol, so that we transfer state records from one component's instance to another on-demand while preserving functionalities without failures.