Enhanced throughput in slotted rings employing spatial slot reuse

A cell based MAC protocol provides both efficient bandwidth utilisation and easy interfacing with the emerging ATM technology. Therefore the slotted approach is being favoured for data transmission and admission control in distributed LANs operating at data rates of more than one Gbit/s. Spatial slot reuse through destination release has been found to be the most effective way towards improving system throughput. That basic mechanism, however, is unfair by giving preference to stations positioned upstream in the ring circulation direction. The paper discusses approaches for an asynchronous media access control in slotted rings. After a general overview of system throughput obtained by an analytical model, the feasibility of various MAC proposals called ATMR, CRMA-II, Distributor, and MetaRing are compared based on simulation results. Differences in the mechanisms are analysed with a particular respect to the tradeoff between high throughput and the guarantee of bounded packet delays. It is shown, that all approaches are generally suitable to meet the requirements of the new LAN generation