This Recommendation belongs to a series of Recommendations which provide a set of facilities to aid the construction of OSI Upper Layer protocols which support the provision of security services. This Recommendation defines the following: a) general models of security exchange protocol functions and security transformations, b) a set of notational tools to support the specification of selective field protection requirements in an abstract syntax specification, and to support the specification of security exchanges and security transformations, c) a set of informative guidelines as to the application of the generic upper layer security facilities covered by this series of Recommendations.