4. SCENARIO AND DEMONSTRATION
The demonstration software of the Collaborative Research
Centre 1053 illustrates the rising need for efficient, selfadaptive distributed systems, using the case-study of video
delivery to mobile devices. It offers a toy model including
the central video streaming server represented by a laptop,
the wireless network depicted by the WiFi Access Point and
five Nexus 7 tablets accessing video from the central server.
The central, resource-limited video streaming server offers
a continuous video stream. Depending on the interest in
the content nodes join the system to watch the stream. The
first clients joining the streaming system retrieve the video
in a continuously high quality. As more and more nodes
are joining the network, the available resources (uplink capacity of the server) are depleted. The system as explained
in Section 2 is designed to replace whole mechanisms and
streaming approaches without interfering with the application layer – in this case the video playback. As the system
is centrally monitored, it can identify a resource bottleneck.
When detecting such a bottleneck, it selects an appropriate
mechanism for highly scalable video streaming - in this case
a P2P overlay - and switches to the new mechanism. During this switch, continuous playback is ensured even though
the underlying streaming mechanism is replaced. In one
demonstration setting the automatic execution of transitions
is disabled initially. Based on a toggle button users can enor disable the automatic execution of transitions. If the transition capabilities are disabled, the user will see reoccurring
stalling as the central server’s upload capacities are limited.
A central visualization as depicted in Figure 1b illustrates