End-to-end availability analysis of IMS-based networks: Simplex and redundant systems

Various methods and models have recently been proposed and applied for evaluating IP Multimedia Subsystem (IMS) in terms of reliability, availability and performance. End-to-end availability is one of the key factors that can improve the quality of service (QoS) and increase the reliability of Next Generation Networks (NGNs). In this paper, an end-to-end availability model is proposed and evaluated using a combination of Reliability Block Diagrams (RBD) and a proposed five-state Markov model. The overall availability for intra and inter domain communication in IMS is analyzed, and the state-of-the-art models are compared with the proposed novel Markov-based reliability modeling for both simplex and redundant systems. The proposed model is proved to efficiently represent the system behaviors. The effect of the end-to-end availability model when applying redundancy in the IMS core system is investigated and numerical results are included.