Protocols or part of protocols are frequently reused through projects if they are sufficiently generic. For instance, the Contract Net protocol can be used verbatim or in other protocols such as the supply chain management. This reusability might be difficult to do due to the lack of reusability in current interaction protocol formalisms. In this paper, we present a new approach based on a modular architecture. A protocol is no longer monolithic but a composition of modules called micro-protocols. This approach improves modularity and reusability in interaction protocol engineering. We apply this idea to the example of supply chain management.