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Notations and performance metrics

We denote by $\lambda$, $L$, and $T$ as the average arrival rate of clients, the length of the video, and the threshold value, respectively. We use the following performance metrics in our evaluation: (1) Rejection probability ($p$) - the probability that a client cannot be admitted and served; (2) Normalized workload ($W$) - the product of average client arrival rate and video length, $W = \lambda L$; (3) Effective normalized workload ($W_e) $ - the admitted normalized workload, $W_e = W (1-p)$; (4) Average workload placed on the network/Network usage ($U$) - the sum of all link usage, $U = \sum_i u_i$, where the link usage of link $i$, $u_i$, is the product of link utilization and its capacity. Hence network usage represents the average workload placed on a network; (5) Server stress ($S$) - the average amount of bandwidth used at the server; (6) Startup delay ($d$) - the time that clients have to wait before actually receiving the video and playing it back. In the following simulation we assume that the video length is 100 minutes.

Yang Guo 2003-03-27