Modular Redundancy for Cloud based IMS Robustness

IMS (IP Multimedia Subsystem) is an emerging architectural framework that delivers a number of multimedia services -- ranging from voice/video over LTE, interactive gaming and many more -- in operational LTE network. Network operators are embracing cloud-based IMS to meet increasing multimedia traffic demand. They can easily and cost-efficiently implement multimedia applications while ensuring superior end-user experiences through always-on services and real-time engagement. In this paper, we reveal that cloud-based IMS cannot provide session-level resilience under faults and becomes the bottleneck to high service availability. The root cause lies upon the weak failure recovery mechanisms at both IMS protocol and cloud platform that terminate the on-going IMS control-plane procedure. To address this, we propose a design that provides fault-tolerance to IMS control-plane operations. Our design provides modular redundancy to perform real time failure recovery. As the system operates, the control-plane operations are logged at redundant IMS NFs modules. These logs are replayed from the failed operation to resume IMS working after failure. We build our system prototype of open source IMS over cloud platform. Our results show that we can achieve session-level resilience by performing fail-over procedure within tens of milliseconds under different combinations of IMS control-plane operations failures.