This paper presents a method to analyze the timing behavior of an event-based real-time protocol composition framework. The framework, called RT-Appia, allows the development and implementation of configurable real-time protocol stacks. The method performs the schedulability analysis for events flowing in a real-time channel and is based on the holistic theory for distributed real-time systems. To illustrate the use of the model, a stack of modular reliable group communication protocols for the CAN field-bus is analyzed and the collected results are compared with previous work.