IP Multimedia Subsystem (IMS) is an evolving architecture designed to create standardized, simple, and scalable networks for deploying rich multimedia applications. The ultimate goal of the architecture is to define a model that separates the services offered by fixed-line (traditional telcos), mobile (traditional cellular), and converged service providers (cable companies and others who provide triple-play services, i.e., voice, video, and data) from the access networks used to receive those services.