A system and method are provided for extending a communication protocol by constructing a top level message, constructing a first level extension message, and embedding the first level extension message in a data component of the top level message. Also, a system and method are provided for extending a communication protocol by receiving a top level message from a communication medium, determining whether a first level extension message is included within the top level message, and extracting the first level extension message from the top level message. Further, a system and method are provided for extending a communication protocol by using a processor to embed a first level extension packet within a top level packet. At least one of the top level packet and the first level extension packet include a message for use in an HVAC system.