Section: 4.2A Handling of NAS signalling low priority indication
Content: A UE configured for NAS signalling low priority (see 3GPP TS 24.368[ Non-Access Stratum (NAS) configuration Management Object (MO) ]  [15A], 3GPP TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [17]) indicates this by including the Device properties IE in the appropriate NAS message and setting the low priority indicator to "MS is configured for NAS signalling low priority", except for the following cases in which the UE shall set the low priority indicator to "MS is not configured for NAS signalling low priority": - the UE is performing an attach for emergency bearer services; - the UE has a PDN connection for emergency bearer services established and is performing EPS mobility management procedures, or is establishing a PDN connection for emergency bearer services; - the UE configured for dual priority is requested by the upper layers to establish a PDN connection with the low priority indicator set to "MS is not configured for NAS signalling low priority"; - the UE configured for dual priority is performing EPS session management procedures related to the PDN connection established with low priority indicator set to "MS is not configured for NAS signalling low priority"; - the UE configured for dual priority has a PDN connection established by setting the low priority indicator to "MS is not configured for NAS signalling low priority" and is performing EPS mobility management procedures; - the UE is performing a service request procedure for a CS fallback emergency call or 1xCS fallback emergency call; - the UE is a UE configured to use AC11 – 15 in selected PLMN; or - the UE is responding to paging. The network may use the NAS signalling low priority indication for NAS level mobility management congestion control and APN based congestion control. If the NAS signalling low priority indication is provided in a PDN CONNECTIVITY REQUEST message, the MME stores the NAS signalling low priority indication within the default EPS bearer context activated due to the PDN connectivity request procedure.