The difference between actual bit rate, measured bit rate for a real-time flow and measured bit rate for a non-real-time flow. 

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... C is the link capacity [bit/s] at the user/network interface. The proper value for parameter α depends on the buffer capacity reserved for the service class used by the connection. With real-time services (with small delay variation) the buffer should be small, and thus the value of α must be quite high. On the contrary, when using a non-real-time service the user may want to send bursts of cells without high cell loss ratio. As a consequence α must be much smaller (or the averaging period should be much longer). The difference between actual and measured bit rates is illustrated in Fig. 3. The key issue in the implementation of the SIMA service in a high capacity core network is the packet or cell discarding system before the actual buffering shown in Fig. 4. At any instant there is an accepted level of priority (PL a ): if an incoming packet or cell has the same or higher priority, it is accepted, otherwise it is discarded. The calculation of PL a is based on the buffer occupancy levels of the real-time buffer (M rt ) and non-real-time buffer (M nrt ). In practice, the calculation of PL a can be based on the use of a pre-calculated table (and therefore, there is no significant real-time processing effort). All the packets or cells which have been accepted in the scheduling unit are situated either in the real-time or non-real-time buffer (the scheduling algorithm can guarantee that there is no cell loss in actual buffers). Both buffers may apply the First In First Out (FIFO) principle. In order to obtain a small delay and delay variation, the real-time buffer should be relatively small (e.g., 10 kbyte). All packets (or cells) in the real- time buffer shall be transmitted before any packet (or cell) in the non-real-time buffer. It should be emphasised that the delay priority of real-time flows has no effect on the packet loss ratios. The ...