Packet-delay invariance to scheduling under congestion

摘要

Class-of-Service enabled networking relies on non-FIFO schedulers in order to achieve differentiated performance, e.g. delay, for different traffic classes. The delay performance of all stable packet schedulers is characterised by a Dominant Decay Rate (DDR) in the presence of bursty traffic. Poisson traffic only results in a “classical”, or Short Buffer Decay Rate (SBDR) which is not the same as the DDR. This paper presents novel experimental results which indicate that, for widely different FIFO and non-FIFO schedulers, the low delay SBDRs are very dissimilar yet the DDRs are virtually identical. We also analytically predict the “knee-point” where the DDR takes over from the SBDR: this is the point at which schedulers become equivalent.