Pushout with global thresholds buffer control scheme in a shared buffer ATM switch

In this paper, a buffer management scheme called pushout with global thresholds (PGT) is proposed for a shared buffer ATM switch. The PGT can be viewed as the combination of the per-port basis pushout and the global threshold schemes. The key idea of the global threshold scheme is to separate the output ports into active and inactive output ports according to whether their queue lengths are larger than the fair buffer allocation factor or not When the remained buffer size is larger than a certain threshold value, all arrival cells are accepted. Otherwise, only the cells destined for inactive output ports are admitted to enter the shared buffer. The simulation study of the global threshold scheme is applied to a shared buffer ATM switch under the per-port basis pushout mechanism. Unlike the selective pushout (SP) scheme, the PGT scheme is simple to implement and easy to maintain. Computer simulation shows that PGT control is very robust and efficient to support much better fairness among different output queues, lower overall cell loss probability, with near loss probability of high priority cells than SP control.