ISO 22663:2015 defines the Data Link Layer (Framing, Medium Access Control, Data Services, and Input/Output [I/O] Sublayers). The specifications for the protocol data units, framing, media access control, expedited and sequenced-controlled data transfer, timing service, I/O control, and the procedures for establishing and terminating a session between a caller and responder are defined in this document. The Coding and Synchronization Sublayer is defined in the separate CCSDS Recommended Standard entitled, Proximity-1 Space Link Protocol?Coding and Synchronization Sublayer (reference [5]). The Physical Layer is defined in the separate CCSDS Recommended Standard entitled, Proximity-1 Space Link Protocol?Physical Layer (reference [6]).

ISO 22663:2015 does not specify a) individual implementations or products, b) implementation of service interfaces within real systems, c) the methods or technologies required to perform the procedures, or d) the management activities required to configure and control the protocol.