aling relationships with the multi-party paradigm. Examining both aspects separately, concepts and technologies are around for serving all needs. Group communication is enabled by multicast session management by SIP, which has a base stan- dard [1] that already defines a minimal interplay with IP-layer multicast. However, to arrive at conferencing solutions of full functionality and comfort, further efforts of integration are needed. This section provides an overview of the main service models and their technological primitives on the SIP and distribution layer within the framework of group conference management. 6.2.1 Common Service Models for Conferencing Group conferencing must be considered a generic term for a wide variety of meanings in different contexts. Generally, it should be understood as an instance or realization of a multi-party conversation and may consist of one or several SIP sessions, each of which combines SIP dialogs as required for com- munication between participants. Such multi-party conversation space may include human and non-human users, e.g., tone-generating robots or record- ing monitors, which may be active and noticeable or hidden. Conferencing may be essentially realized by the three following service models of multi- party communication [5, 17]. 6.2.1.1 Loose Coupling Within conferences following a loosely coupled model, no signaling relation- ship is maintained between conference participants. This considerably light- weight approach is exceptionally scalable, easy to implement, but does not provide any SDP offer/answer dialog. Also, no standard way of authentica- tion, policy execution, or conference coordination is provided. There is no single instance of control nor a conference server or focus. Instead, participa- tion may be gradually learned by RTCP [18] control streams. Its realization requires an any-source multicast distribution layer for media streams. A con- ference can be entered by simply joining a multicast group, while addresses and media information may be pre-shar