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16 plots the probability of the number of candidate clients contacted (i.e., the candidate patch servers contacted during the patch recovery, or the candidate base stream servers contacted during the base stream recovery) before a client can successfully recover from the failures. The left column of Fig. 16 is for the patch recovery; and the right column is for the base stream recovery. Since a client can be disrupted more than once, we collect the accumulated number of candidate clients contacted in recovery. The top two plots in Fig. 16 are for a threshold equal to 10% of the video length; and the bottom two plots are for a threshold equal to 30% of the video length. We assume that a client departs early with a probability of 0.1, and an early departing client is equally likely to depart at any point during the playback. Most clients (0.996 for threshold 10% and 0.983 for threshold 30) will not be disrupted at all during the playback of a patch stream in our example. Patch delivery is disrupted only if the patch server departs while serving the patch. Since the length of patch is usually short, the chance that a patch gets disrupted is small. Furthermore, the probability that a client has to contact more than 5 candidate clients during patch recovery is less than 0.0003 and 0.0019, respectively, for the threshold of 10% and 30%. Thus if we can delay the playback for a short period and let the buffer build up a bit, say by delaying the playback to the time to contact 5 clients, the continuous playback of the patch stream can be provided with high probability.
Next: Disruption effect on continuous Up: Failure Recovery - Providing Previous: Failure Recovery - Providing Yang Guo 2003-03-27