A key enabler of the recently popularized, assembly-centric development approach for distributed real-time software systems is QoS-enabled middleware, which provides reusable building blocks in the form of design patterns that codify solutions to commonly recurring problems. These patterns can be customized by choosing an appropriate set of configuration parameters. The configuration options of the patterns exert a strong influence on system performance, which is of paramount importance in many distributed software systems. Despite this considerable influence, currently there is a lack of significant research to analyze performance of middleware at design time, where performance issues can be resolved at a much earlier stage of the application life cycle and with substantially less costs. The present project seeks to develop a performance analysis methodology for design-time performance analysis for distributed software systems implemented using middleware patterns and their compositions. The methodology is illustrated on a producer/consumer system implemented using the active object (AO) pattern in middleware. Finally, broader impacts of the methodology for middleware specialization are also described.