Comparing KNXnet/IP forwarding rules in congestion conditions

KNX is an European and International communication standard for home and building automation; it has been recently updated by the definition of KNXnet/IP system, which allows integration of different KNX networks through an IP network used as fast backbone. Integration is realised by a particular device called KNXnet/IP Router. Due to the very limited transmission speeds foreseen for the KNX networks, the KNXnet/IP Router may represent a bottleneck in routing telegrams coming from the IP network whose destination is a KNX device located in the relevant KNX network; congestion in the KNXnet/IP Router may occur when it is unable to forward all or part of the telegrams coming from IP toward the KNX network. The KNXnet/IP specification has defined two forwarding rules the Router can implement. The aim of the paper is to analyse the effect of these two forwarding rules on the congestion of the KNXnet/IP Router. Congestion analysis has been carried on by modelling and simulation of the KNXnet/IP communication system.