An end-user who wants to participate in group communication on the Internet must first resolve the session information including the contents type, data source and destination addresses. An effective session directory system is therefore the necessary component for the delivery of the maximum group communication value to a large number of world-wide users. In this paper, we formalize a distributed session directory system called "Channel Reflector (CR)." The advantage of CR is that, while an end-user can retrieve interesting session information from CR through a regular web interface, there is no contradiction to the dynamic nature of the session announcement scheme and the scoping technique in this architecture. For the deployment purpose, we show the actual implementation and the measurement results on the session synchronization delay given by the PlanetLab overlay network testbed.