Service Access Point

A Service Access Point (SAP) is an identifying label for network endpoints used in Open Systems Interconnection (OSI) networking.

The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. As an example, PD-SAP or PLME-SAP in IEEE 802.15.4 can be mentioned, where the Media Access Control (MAC) layer requests certain services from the Physical Layer. Service access points are also used in IEEE 802.2 Logical Link Control in Ethernet and similar Data Link Layer protocols.