Its is getting increasingly difficult for me to understand various scenarios of Detaches. Here is (what I call) HSS initiated detach for strictly my reference.
CLR is can be sent with 4 (?) causes.
Case 1. "Subscription Withdrawal" if the subscriber’s subscription is withdrawn by the operator
Case 2. "MME Update Procedure" if the UE moved to a new MME area
Case 3. "SGSN Update Procedure" if the UE moved to a new SGSN area
Case 4. "Initial Attach Procedure" if the cancel location is initiated due to an Initial Attach from the UE.
Case 1. is when an operator (like vodafone) withdraws the subscription. If the UE is in EMM-REGISTERED and ECM-IDLE, we page the UE and then flunk him off the network.
Case 2 and Case 3 happens when the UE is offloaded (?) to another MME/SGSN. We do not page the UE.
Case 4 is when UE request for INITIAL ATTACH. From this blog, The E-UTRAN Initial Attach procedure is used for Emergency Attach by UEs that need to perform emergency service but cannot gain normal services from the network.(Refer 3GPP TS 23.122) . here also we do not page the UE.
A case where MME would receive a cancel location with type as initial Attach and UE is (ECM)connected would be a very fatal error in the network. For some reason ENB would not release the connection towards old MME but still accepting it to create a new one, so that can not be seen as a valid scenario.
Update:
We do not send Disconnect to MSC-VLR if the UE is in (what I call) combined attach mode (This means when UE is attached to both 4G and 3G networks, say for example fall-back to 3G for voice when a data transfer session is on-going)
Note to self:
Some more info has to be added.
CLR is can be sent with 4 (?) causes.
Case 1. "Subscription Withdrawal" if the subscriber’s subscription is withdrawn by the operator
Case 2. "MME Update Procedure" if the UE moved to a new MME area
Case 3. "SGSN Update Procedure" if the UE moved to a new SGSN area
Case 4. "Initial Attach Procedure" if the cancel location is initiated due to an Initial Attach from the UE.
Case 1. is when an operator (like vodafone) withdraws the subscription. If the UE is in EMM-REGISTERED and ECM-IDLE, we page the UE and then flunk him off the network.
Case 2 and Case 3 happens when the UE is offloaded (?) to another MME/SGSN. We do not page the UE.
Case 4 is when UE request for INITIAL ATTACH. From this blog, The E-UTRAN Initial Attach procedure is used for Emergency Attach by UEs that need to perform emergency service but cannot gain normal services from the network.(Refer 3GPP TS 23.122) . here also we do not page the UE.
Additionanl Notes:
Subscription Withdrawal is the only case when MME should send detach indication to the subscriber. In other cases it shall be an implicit detach in MME and towards GW.A case where MME would receive a cancel location with type as initial Attach and UE is (ECM)connected would be a very fatal error in the network. For some reason ENB would not release the connection towards old MME but still accepting it to create a new one, so that can not be seen as a valid scenario.
Update:
We do not send Disconnect to MSC-VLR if the UE is in (what I call) combined attach mode (This means when UE is attached to both 4G and 3G networks, say for example fall-back to 3G for voice when a data transfer session is on-going)
Note to self:
Some more info has to be added.
