IMPROVED MAC PROTOCOL FOR CAMBRIDGE FAST RING : A SIMULATION -STUDY

Abstract

The Cambridge Fast Ring is a high speed slotted ring. The features that make it suitable for use at large transmission rates are the synchronous transmission, the simplicity of the protocol and the possibility of immediate retransmission of erroneous packets. The CFR medium access control (MAC) protocol allows for only one slot at a time to be used by each station. This scheme does not ensure efficient utilization of the ring, because after a ring rotation the slot has to travel empty at least upto next downstream station. If the slots are allowed to be used by the station exhaustively to increase utilization, then there arises the problem of unfair sharing of the transmission medium. Here an improved MAC protocol has been proposed which not only ensures fair sharing of the transmission medium but also improves delay and ring utilization. Finally a variant of the CFR MAC protocol (in which a station can use many slots) has been studied.