What would be the functional difference between implicit and explicit detach procedure?

Question

In case of hub-and-spoke topology, X2 messaging can travel all the way back to an aggregation point, which may be co-located with EPC. In such scenario both X2 and S1 traverses same physical path (a.k.a X2 over S1). Please consider both Intra-MME and Inter-MME handover scenarios. Would X2 based handover in such a case yield advantage over S1 based handover. Thanks.

Answer 1

Implicit -> When the detach procedure is initiated by the network(MME).

MME informs the UE with an EMM message (Service Reject/ TAU Reject) with EMM cause as "implicitly detached" only when the UE initiates any EMM procedure.

It then initiates the detach procedure by sending a DETACH REQUEST message to the UE
Detach type IE can either be "re-attach required" or "IMSI detach". For both of them there is a separate approach, i.e. how & why the bearer contexts are retained & how they are reestablished,etc.

Explicit -> When the UE initiates the detach procedure by sending a DETACH REQUEST message.

Again the detach type can be either ‘EPS detach’ / ‘IMSI detach’ / ‘Combined EPS/IMSI detach’.