ABR SERVICE ENGINE IN PACKET SWITCHING SYSTEM

摘要

An ABR (Available Bit Rate) service engine in a packet switching system. A forward cell processing unit generates a first start signal and extracts CCR (Current Cell Rate) and MCR (Minimum Cell Rate) from a forward RM (Resource Management) cell, upon receipt of the forward RM cell. A locally bottlenecked virtual circuit number (|Q|) estimation unit determines whether (CCR-MCR) is less than ER (Explicit Rate) upon receipt of the first start signal, considers that the received RM cell contributes to |Q| if (CCR-MCR) is less than ER, accumulates the degree of contribution, and calculates |Q|. An ER engine calculates the ER upon receipt of a third start signal. A backward cell processing unit determines whether the ER calculated by the ER engine is less than the sum of ER and MCR extracted from a backward RM cell upon receipt of the backward RM cell, and writes the calculated ER in the backward RM cell if the calculated ER is less than the sum of ER and MCR. A timer feeds the second start signal to the |Q| estimation unit every first period and the third start signal to the ER engine every second period.