Difference between NAS level congestion control and APN based congestion control ?

Question

when to use what ?

Answer 1

NAS Level Congestion Control
Ø When the network detects EMM signalling congestion, it may perform NAS level congestion control. The NAS level congestion control consists of general NAS level mobility managementcontrol and subscribed APN based congestion control
Ø Under general overload conditions the network may reject mobility management signalling requests from UEs. The network should not reject requests for emergency bearer services and requests from high priority users
Ø When general NAS level mobility management control is active, the network may prioritize rejecting messages that has the NAS signalling low priority indicator before rejecting messages without the NAS signalling low priority indicator
Ø When the NAS level congestion control is active in mobility management, the network may include a value for the back-off timer (T3346) in the reject messages
Ø If the UE enters a new PLMN which is not in the list of equivalent PLMNs, it shall stop timerT3346 when initiating mobility management procedures in the new PLMN
Ø When subscribed APN based congestion control is active for a particular APN, the network may reject attach request from UEs with a subscription to this APN
Ø A UE configured for NAS signalling low priority indicates this by including the Device propertiesIE in the appropriate NAS message and setting the low priority indicator to "MS is configured for NAS signalling low priority"
Ø The UE shall set the low priority indicator to "MS is not configured for NAS signalling low priority" for the following cases
· The UE has a PDN connection for emergency bearer services established or is establishing a PDN connection for emergency bearer services
· The UE is accessing the network with access class 11 – 15
· The UE responds to paging
Reference: 3GPP TS 24.301