End-to-end availability considerations for services over IMS

Lucent IP Multimedia Subsystem (IMS) architecture provides an open framework for multimedia applications that support blended text, voice, and video services. Providing objectives for service downtime and failure rates, which reflect the end customer perspective, can be used to drive corrective and preventive action that better satisfy end customer expectations. However, the frameworks and techniques to do this on an end-to-end basis for network solutions of the complexity and size of IMS are not well established. In this paper we address the questions of specifying, estimating, and verifying the end-to-end availability for services over IMS. The purpose of this paper is to present a framework for establishing availability requirements and service failure rate metrics, and for performing "end-to-end" service downtime analysis. The framework can be used to guide network design and evaluate end-to-end performance in the field. (c) 2006 Lucent Technologies Inc.