AbstractPerformance studies on LAN/MAN‐BISDN interworking have mainly focused on the requirements of isochronous and connectionless services. In this paper we extend performance results to cover also the case of non‐isochronous connection oriented (CO) services supported by the queued arbitrated (QA) mode of access of the DQDB protocol. Using this case we stress the more general issue of service integration impact on the interworking unit (IWU) architecture design in terms of protocol stacks and expected performance. We herein evaluate the performance of IWU architectures tailored to relay information in the lowest possible layer while implementing several service priority schemes and buffer management policies towards QoS objectives. The conditions under which the IWU design is efficient regarding performance, protocol complexity and implementation cost in this integrated services environment are identif