ABSTRACT
The Head-of-Line (HoL) blocking problem, which occurs in input-buffered service systems, degrades their performance, especially in “hot-spot” traffic conditions. In this paper, we study a variation of the FIFO queues, called “Retreat FIFOs” or “FIFOs with Retreat” (RFIFOs), which significantly improves the performance of plain FIFOs, with respect to the HoL blocking problem. We simulate and compare three FIFO types; a typical FIFO, an RFIFO and a “FIFO with Overflow” (VFIFO). RFIFOs are simulated with a variable number of “retreat steps” (a variation referred to as “RFIFO-S”). Our simulation results indicate that the performance of the RFIFO is significantly better compared to plain FIFOs, and VFIFOs, especially for hot-spot traffic. Furthermore, the RFIFO-S has improved throughput over the RFIFO in congested conditions.
