What do BACnet Interoperability Building Blocks (BIBBs) describe?

BACnet Interoperability Building Blocks (BIBBs) are fundamental components that define the specific services and communication capabilities between BACnet devices in a building automation system. They illustrate how different devices can work together regardless of the manufacturer, offering a clear framework for interoperability. BIBBs specify the functional requirements and types of interactions that can occur, ensuring that devices can communicate effectively to fulfill application demands.

This means that choice B precisely captures the essence of BIBBs by highlighting their role in outlining the inter-operational capabilities that a BACnet device offers. This includes defining how devices can share and exchange information, which is essential in complex building management systems where various devices need to collaborate to optimize performance and efficiency.

The other options focus on aspects that, while relevant to building automation, do not encapsulate what BIBBs specifically describe. For instance, options about physical connections, routing functions, or resource limitations pertain more to underlying infrastructure or specific technical considerations rather than the interoperability and communication protocols defined by BIBBs. Thus, the emphasis on inter-operational capabilities makes choice B the most relevant answer.