Feedback rate control with congestion prediction by edge nodes in ATM-WAN

This paper proposes a new adaptive remote rate control based on extrapolation called AREX. AREX does not require a high-speed switching node to have high calculation load. Consequently, transit switches with high-speed interface do not always need to have high calculation power. As a result rate control can be implemented easily in a WAN. AREX reduces the major problems of feedback rate control, inaccuracy of feedback information and large necessary buffer space caused by long propagation delay. In AREX, a high-speed transit switching node only observes the link utilization ratio of the output VP and notifies it to upstream nodes. Local switching nodes with spare calculation power calculate and control the output rate of each VC. Because the admissible cell rate of each VC is calculated by local switches, ABR service can be emulated there. This paper describes the mechanisms of AREX and discusses the function form that determines its characteristics. AREX tries to converge utilization to the target value. The relationship between target value and overload probability is clarified for network management. The performance of ABR emulated by APEX is evaluated by computer simulation. The results show that AREX provides high throughput and requires less buffer capacity even in a network with long propagation delay.