Some policies for circuit allocation and their packet capacity in hybrid switching systems like FDDI-II

The authors present some circuit allocation policies for hybrid switching systems. The policies are based on the same framing structure as in FDDI-II (fiber distributed data interface II) and QPSX (queued packet and synchronous switch). Under the first-fit (FF) policy considered in QPSX, it is shown that sets of empty octets no smaller than a packet length are frequently observed with isochronous slots. The wasted capacity from these sets can be efficiently recovered by proposals called FFO (first fit with optimal repacking) and FFSA (first fit with state adaptive repacking). In particular, FFSA aims at maximizing the packet switching capacity under a user-defined constraint of processing cost. Some numerical results on capacity and the additional processing rate are given