ISO 18445:2016 Practice defines extensions to the SLE API in terms of:
a) the CLTU-specific functionality provided by API components,
b) the CLTU-specific interfaces provided by API components, and
c) the externally visible behavior associated with the CLTU interfaces exported by the components.
It does not specify
a) individual implementations or products,
b) the internal design of the components, and
c) the technology used for communications.
ISO 18445:2016 defines only interfaces and behavior that must be provided by implementations supporting the forward CLTU service in addition to the specification in reference [5].