release jitter of tasks
there is a distinction between the real activation request and the actual activation instant of a task.
release jitter of packets
The maximum difference in the latency between two packets within a flow.
Low jitter is often a requirement for video streams or other real time data for which the regularity of data arrival is important.
The jitter times gives a lower bound on the size of buffer required.
For example, in a video playback system, the size of the buffer required to hold packets before playback is determined by the jitter, not the average latency.
release jitter J_i denotes the maximum deviation of successive packets released from its period.
If a packet from f_i is generated at time a (real activation), then it will be released for transmission by time a+J_i (actual activation)
and have global deadline a + D_i, and local deadline a+J_i + D_i.