An effective access control method for high-speed local area networks and metropolitan area networks

This paper proposes an access protocol with a high throughput for the ultrahigh-speed local area network (LAN) and metropolitan area network (MAN) with the transmission capacity exceeding 100 Mbps. The slotted-ring configuration is suited to the access method for the ultrahigh-speed LAN/MAN. Several protocols have been proposed, such as DQDB and ATMR, which, however, have problems in that the throughput in DQDB cannot reach the transmission capacity and the throughput in ATMR decreases when the traffic is nonuniform. In the proposed protocol, the reset signal circulates the ring and the fairness of the access is ensured by limiting the number of slots to be sent by each node by the window size. The number of slots to be sent is not limited if none of the downstream nodes has data to be sent. This helps to realize a high throughput independently of the traffic situation. As the result of performance evaluation, it is verified that the proposed protocol is useful in the following two points: (1) approximately 1.8 times higher throughput is realized compared to the existing protocols when the traffic concentrates to a particular node; and (2) the delay time is suppressed to a low value for burst traffic such as video.