In the context of distributed multimedia applications involving multicast to a large number of users, a single quality of service level may not be appropriate for all participants. It is necessary to distribute part of the QoS management process and allow each user process to make certain QoS decisions based on its local context. In order to allow for different QoS options, we assume that each source provides, for each logical multimedia stream, several different stream variants, representing different choices of user-level QoS parameters. The paper presents the design of a teleteaching system which uses this paradigm for QoS negotiation, and explains how the Delivery Multimedia Integration Framework (DMIF) of MPEG-4 can be adapted as a session protocol for such an application. In fact, it appears that this DMIF protocol, which is now being extended by ISO (DMIF Version 2) to the context of multicasting, provides some general session management functions which are quite useful for many...