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 management control 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 timer T3346 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 properties IE 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
Hi Kumar,
ReplyDeleteReally interesting and it helped me to better understand LAPI.
1/ Do you know the difference between T3246 and T3346 ? You mentionned T3346 is at MM, so i understand that T3246 is at RRC (LAPI mechanism also takes place at RRC level)?
2/ I also understood T3246 and T3346 are both optional, ie in REJECT msg, network may not populate those values. I suppose there is a default value that is set up in the UE ? Is my understanding right ?
3/ If so, is this default value advertised by the UE to the network. If yes, then all makes sense to me. If not, then In understand module shall reconnect after this time-out but it may also break the rule and try to re-attach before the time-out and network can't do anything against it.