In this article we propose exact analysis of the data network node using two transmission channels with different bit transmission rates. The inter arrival time of data packets and the transmission times of each channel are generally distributed. Heterogeneous transmission channels often occur in the data network when channels are working in parallel. Research is in progress to develop exact analytical and simulation models for such data packets transmission system. Using our proposed models we can easily evaluate asymmetric data node performance measures. The results of some performance measures are taken when different strategies for selecting a free channel are applied. An asymmetric data network node simulation is based on Moore and Mealy automata. The analytical system model, that based on continuous time Markov chains, was created in comparison to the simulation model results.