When a mobile station moves from one MSC area to another during a call, a handover procedure has to be performed in order to continue the communication. For that purpose the MSC servers have to exchange data to initiate and then to realise the operation.
After the handover operation has been completed, the MSC servers will exchange information to transfer A- or
Iu- interface signalling as defined in TS 23.009.
When a short message is to be transferred between a Mobile Station and Short Message Service Centre (SC), in either direction, this interface is used to transfer the message between the MSC server serving the Mobile Station and the MSC server which acts as the interface to the SC.
Signalling on this interface uses MAP (TS 29.002).