Access delay in LonTalk MAC protocol

The study deals with the analysis of latency introduced by the media access control algorithm of LonTalk protocol registered as ANSI/CEA-709.1 standard and used in LonWorks control networking technology. The LonTalk protocol provides multicast communication which is a distinctive feature among control network protocols. The predictive p-persistent CSMA protocol built in the MAC sublayer uses the memoryless backoff, additive increase/additive decrease contention window adjustments, provides collision avoidance and optional collision detection.The behavior of the LonTalk MAC protocol, unlike of the other CSMA schemes, is forced not only by the traffic rate but also by the structure of the workload transmitted through the channel. Therefore, the predictive p-persistent CSMA performance depends on the load scenario defined as the specification of the input traffic generated to the network. In the study, a unified method of load scenario definition integrating various addressing and message service types, is used. The contribution of the paper is the adaptation of the analytical approach based on Markov chains to the evaluation of mean access delay of LonTalk protocol for any load scenario.