— The telecom and the internet world is converging towards all-IP network architecture and the operators are keen to provide innovative multimedia services coupled with advanced features such as seamless mobility across heterogeneous access networks to the users. Session Initiation Protocol (SIP) provides ired application-level abstraction to enable advanced mobility and session management for multimedia services across heterogeneous access networks. However, sip-based handoff procedures suffer from delay and packet losses that hamper the user experience for delay-sensitive multimedia applications. In this paper we have attempted to perform a reality-check on the performance of such sip-based multimedia applications across the existing heterogeneous access network technologies by measuring delay, mean opinion score (MOS) and throughputs experienced, thus evaluating the user-experience. The paper presents the performance results obtained on a test-setup connected to a live operator ne...