service user

In OSI terminology, the service user is always the higher layer that uses the services of the lower layer, that of the service provider, to complete its own tasks. Each layer is the service provider for the service user of the layer above it. The only layer that cannot access any layer below it is the physical layer, and it is the only one that is a service provider only. The service is handed over from the service provider to the service user at the service access point.