ISO 18202:2015 defines, in an abstract manner, the MAL in terms of:

a) the concepts that it builds upon;

b) the basic types it provides;

c) the message headers required by the layer;

d) the relationship between, and the valid sequence of, the messages and resulting behaviours.

It does not specify:

a) individual implementations or products;

b) the implementation of entities or interfaces within real systems;

c) the methods or technologies required for communications.