Application-layer mobility support for streaming real-time media

This paper presents an UDP-based socket extension called the resilient mobile socket (RMS), which provides application-layer mobility support by encapsulating other sockets into a new aggregated socket abstraction. Encapsulated sockets can then be added or removed without disturbing running applications. RMS also provides a method for soft handovers where several encapsulated sockets are used simultaneously during a handover. As a proof of concept, a working prototype has been built by integrating RMS with Marratech Pro, a commercially available e-meeting application. This prototype has been used to evaluate RMS and to investigate how GSM audio quality is affected by handovers. The result from the investigation shows that soft handovers can be executed without loosing packets or causing extra latency, while a hard handover in average took around 200 ms to complete. This indicates that proactive handovers and redundancy are important, but that more work must he done to predict disconnections.