Many architecture-based software reliability models have been proposed in the past without any attempt to establish a relationship among them. The aim of this paper is to fill this gap. First, the unifying structural properties of the models are exhibited and the theoretical relationship is established. Then, the estimates provided by the models are compared using an empirical case study. The program chosen for the case study consists of almost 10,000 lines of C code divided into several components. The faulty version of the program was obtained by reinserting the faults discovered during integration testing and operational usage and the correct version was use as an oracle. A set of test cases was generated randomly accordingly to the known operational profile. The results show that 1) all models give reasonably accurate estimations compared to the actual reliability and 2) faults present in the components influence both components reliabilities and the way components interact.