In network communications, as in many fields of engineering, it is a fact that "one size does not fit all." Engineering design is about making the right set of trade-offs, and these trade-offs must balance conflicting requirements such as simplicity, generality, ease of use, richness of features, performance, memory size and usage, scalability, determinism, and robustness. These trade-offs must be made in light of the types of information flow (e.g. periodic, one-to-many, request-reply, events), and the constraints imposed by the application and execution platforms. The Type 15 fieldbus provides two major communication mechanisms that complement each others to satisfy communication requirements in the field of automation: the Client/Server and the Publish/Subscribe paradigms. They can be used concurrently on the same device.