Jitter control in QoS networks

Abstract

We study jitter control in networks guaranteeing quality of service (QoS). Jitter measures variability of delivery times in packet streams. We propose on-line algorithms that control jitter and compare their performance to the best possible (by an off-line algorithm) for any given arrival sequence. For delay jitter, where the goal is to minimize the difference between delay times of different packets, we give an on-line algorithm using buffer size of 2B which guarantees the same delay-jitter as an off-line algorithm using buffer space B. We show that 2B space is the minimum space required by any on-line algorithm to provide delay-jitter related to the best possible delay-jitter using B buffer space. We also show that the guarantees made by our online algorithm hold even for distributed implementations, where the total buffer space is distributed along the path of the connection, provided that the input stream satisfies a certain simple property. For rate jitter, where the goal is to minimize the difference between inter-arrival times, we develop an on-line algorithm using a buffer of size 2B+h for any h/spl ges/1, and compare its jitter to the jitter of an optimal off-line algorithm using buffer size B. Our algorithm guarantees that the difference is bounded by a term proportional to B/h. We also prove that 2B space is necessary for on-line algorithms with non trivial guarantees for rate-jitter control.