In this paper we present a framework for engineering Ethernet DQDB interconnections for messaging mode. Very simple and accurate relations are developed for evaluating bus access delay and jitter in terms of the DQDB traffic behavior and an upper bound of the probability of loss due to access queue overflow. The performance evaluation shows that DQDB offers the possibility of interconnecting Ethernets with a very good quality of service, that means small delay jitter and very rare overflow of the access queue.