This SAE Information Report is a summary comparison of existing protocols found in manufacturing, automotive, aviation, military, and computer applications which provide background or may be applicable for Class C application. The intent of this report is to present a summary of each protocol, not an evaluation. This is not intended to be a comprehensive review of all applicable protocols. The form for evaluation of a protocol exists in this paper and new protocols can be submitted on this form to the committee for consideration in future revisions of this report. This report contains a table which provides a side-by-side comparison of each protocol considered. The subsequent section provides a more detailed examination of the protocol attributes. Many of the protocols do not specify a method for one or more of the criteria. In these circumstances 'under defined' or 'not specified' will appear under the heading.