ed in Section 6.2.2. Charlie is also able to submit feedback after registering with the conference, potentially under a basic floor control mechanism [9] smoothly embedded in SIP addressing. 6.1.2 The Application Domain for SIP-Managed Group Conferencing 6.1.2.1 Audio Conferences The primary dedication of SIP lies in a standardized signaling for transparent voice-over IP services. SIP thereby simultaneously targets campus solutions the range of Private Branch Exchanges (PBXs) or the ITU H.323 [10] VoIP © 2009 by Taylor & Francis Group, LLC Group Conference Management with SIP architecture, and global call handling based on Internet routing or, possibly in parts, on the public switched telephone network. For the sake of competitive- ness, core voice conferencing functionality as offered by the digital telephone infrastructure or available through in-house conference control units must be part of the service spectrum of SIP. Traditional voice conference calls allow for easy media mixing, consist of limited group sizes, and SIP-initiated Inter- net telephony solutions can easily cope with underlying demands. Obviously, such characteristics likewise hold for simpler or supplementary group applica- tions as chat or whiteboards. However, as a flexible signaling protocol suitable for decentralized relaying architectures, SIP may give rise to a multitude additional services, unknown in traditional telephone networks. 6.1.2.2 Videoconferencing over IP The idea of augmenting voice conferences by video has been around for sev- eral decades, but only the flexibility of the Internet generated a noticeable deployment. As compared to audio, video processing places significantly higher demands on end system and network transmission capabilities. The rapid evolution of networks and processors have paved the way for realistic group conferences conducted at standard personal computers, combining about a dozen visual streams of Half-Quarter Video Graphics Array (QVGA) (240 X 160 pixel @ 15-25 fps) resolution. Thus, initial centraliz