Interfaces may be regarded as the implementations of TMN reference points. Whereas reference points may generally be compared with underlying services, interfaces may be compared with the protocol stacks that implement these services.

In most cases reference points and interfaces have a one to one mapping. However, no interfaces exist for those reference points that:

The naming of interfaces is also straightforward: an interface gets the same name (this time written in upper case) as the related reference point. Figure 17 shows all possible mappings.