ed implementations based on H.323 are now superseded by peer-centric personal systems with SIP. Lightweight videoconferencing software today smoothly integrates desk- top video of high quality with thin clients on mobile phones [11] like the daViKo system4. In concordance with communication capabilities, video coding techniques have evolved as well. The latest standard for video coding H.264/AVC [12], although designed as a generic standard, is predestined for applications like mobile video communications. Besides enhanced compression efficiency, it also delivers network-friendly video representation for interactive (video telephony) and non-interactive applications like broadcast, streaming, storage, and video on demand. H.264/AVC provides gains in compression efficiency of up to 50% over a wide range of bit rates and video resolutions compared to previous stan- dards. While H.264/AVC decoding software has been successfully deployed on handhelds, its high computational complexity still challenges current mobile devices when implemented as pure software encoders, however, fast hardware implementations are available. Next generation codecs like Scalable Video Coding (SVC) are already approved [13]. The main new feature, scalability, addresses schemes for delivery of video to diverse clients over heterogeneous networks, particularly in scenarios where the downstream conditions are not known in advance. The basic idea is that one encoded stream can serve net- works with varying bandwidths or clients with different display resolutions or systems with different storage resources. This not only enables media mixers tsee http://www.daviko.com C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security or conference bridges to simultaneously serve streams of different resolution without transcoding, but is an obvious advantage in heterogeneous networks prevalent in mobile applications, as well. 6.1.3 Gaming Multiplayer games fall into the realm of SIP conferencing services for two reasons. At