N-user

n -user: In the ISO Open Systems Interconnection--Reference Model (OSI--RM), an n +1 entity that uses the services of the n-layer, and below, to communicate with another n +1 entity.

Note: If n identifies a specific or a reference level, the n +1 layer is the layer above the n layer and the n-1 layer is the layer below the n layer. Thus, the n +2 layer is two layers above the n layer.

Source: from Federal Standard 1037C