In recent trends, the Architecture Analysis and Design Language (AADL) has received increasing attention from safety-critical software development industries. Specific about the AADL is its strong syntactic and semantic support for the description of both hardware and software architectures. Considering the existing range of software architectures, we study the support AADL offers for the description of software architecture. As a case study we use an implementation of a UDP/IP protocol stack. Based on our experiences, our position is that a number of concepts, e.g. a generic component concept, are missing in the AADL to make it well-suited for the highlevel description of software architecture.1