EVALUATION OF POLICING MECHANISMS FOR ATM NETWORKS

To realize Broadband ISDN,which provides multi-media services, ATM (As ynchronous Transfer Mode) has been standardized by CCITT and the devel opment of the system is accelerating towards the 21st century. The pac ket-oriented information transfer based on fixed size blocks called ce lls provides a very flexible allocation of transmission capacity to di fferent connections. On the other hand, to ensure the QoS (Quality of Service) for all established connections it is necessary to monitor an d regulate the input traffic from each user based on usage parameters which are negotiated between user and network at connection set-up, i. e., a policing function is required. In this paper some requirements f or a policing function will be given. Accuracy of the policing decisio n for violating and well-behaving sources, tolerance with respect to c ell delay Variation (CDV) which is caused by multiplexing functions be tween the source terminal and the policing device, lime to detect arri ving violating cells, implementation complexity, and amount, i.e., cos t effectiveness, are discussed mainly. We present simulation results f or five policing mechanisms, Leaky Bucket (LB), Jumping Window (JW), a nd Moving Window (MW) which have been already well-known, Pseudo Jumpi ng Window (PJW), and Pseudo Moving Window (PMW) which are proposed mec hanisms. PJM and PMW mechanisms required a pseudo cell buffer with fin ite queueing capacity to the corresponding JW and MW mechanisms, respe ctively. These two mechanisms can be expected as advanced methods from view points of the accuracy of the policing for long-term fluctuated compliant source, fast reaction ability and restrictness to long burst traffic comparing with the above existing methods. We compare the fiv e mechanisms based on the above requirements and show that the PJW and the LB are the most effective mechanisms for mean rate policing in AT M networks.