A Framework for Group Integrity Management in Multimedia Multicasting

Multicast research has so far been focused on routing and network-level group management. Conditions on the composition of multicast groups have however been kept simple, with little efforts to specify requirements in terms of membership, member roles and group organization. Integrity conditions on multicast groups have been largely neglected despite the fact that it is often desirable to express who should be admissible as a member, with what role and privileges, what relation a group should have to other groups, etc. Furthermore, the traditional multicasting model has been flat, with no finer granularity than a group, and without inter-group relationships. In this paper, we address both issues that we see as shortcomings of current models. We introduce a framework that allows us to sub-divide multicast groups into subgroups, e.g. for low and high quality versions of a media stream, and, on the other hand, to form and manage meta groups from groups, thus integrating "multi" media groups. On all three levels, our framework provides for specification of various integrity conditions as part of a comprehensive policy framework, including integrity on state and state transition as well as action and transition policies for group management.