What do we call a system used for passing messages between components in a distributed system?

In the context of distributed systems, a communication protocol is indeed a fundamental system used for passing messages between various components. Communication protocols define the rules and conventions for data exchange, ensuring that messages are formatted, transmitted, and interpreted correctly among the parts of the distributed architecture.

Protocols can encompass aspects such as how connections are established, how data is structured and encoded, and how errors are handled in message transmission. This ensures that even if different components are developed in various programming languages or run on different platforms, they can still effectively communicate with one another.

While other terms like "data bus," "message queue," and "message passing system" are related to communication in computing, they refer to more specific concepts. A data bus is typically a physical connection that transfers data between components inside a computer. A message queue is a particular technique for managing messages sent between programs, allowing them to communicate asynchronously. A message passing system generally refers to the overall methodology or framework for exchanging messages but does not define the underlying rules of communication. Thus, focusing on the communication protocol reflects the broader, foundational aspect necessary for ensuring successful inter-component interactions in distributed systems.