This TS defines the principal architecture of layer 3 and its sublayers on the GSM Um
interface, i.e. the interface between Mobile Station (MS) and network; for the CM sublayer, the description is restricted to paradigmatic examples, call control, supplementary services, and short message services for non-GPRS services. It also defines the basic message format and error handling applied by the layer 3 protocols.
For non-GPRS services the communication between sublayers and adjacent layers and the services provided by the
sublayers are distributed by use of abstract service primitives. But only externally observable behaviour resulting from the description is normatively prescribed by the present document.
For GPRS services in addition the local information transfer and stimuli sent between sublayers is informatively
included within Annex C
of in the present document.
This document also defines the principal architecture of the EPS NAS layer 3 protocol and its sublayers, including the message format applied by layer 3.