This Recommendation defines the general concepts for OSI conformance testing methodology and framework for protocol Recommendations. It provides general principles for conformance testing which can make possible wide acceptance and confidence of conformance test results. It describes the definition of terms, test methods and test suites of OSI protocol conformance testing. The text was developed jointly with ISO/IEC JTC1 and the main intent of this revision is to reflect the changes as a result of the work on Protocol Profile Testing Methodology(PPTM) and on Multi-Party Testing Methodology(MPyTM).