The UE is RRC connected.
During the HO:
The radio link is released from the eNodeB 1 and re-established on the
eNodeB 2
The Control plane is switched to the eNodeB 2 and the MME
The User plane is switched to the eNodeB 2 and the S-GW
The Intra-e-UTRAN-Access Mobility Support for UEs in ECM-CONNECTED handles all necessary steps for relocation/handover procedures, like processes that precede the final HO decision on the source network side (control and evaluation of UE and eNB measurements taking into account certain UE specific area restrictions), preparation of resources on the target network side, commanding the UE to the new radio resources and finally releasing resources on the (old) source network side.
It contains mechanisms to transfer context data between evolved nodes, and to update node relations on C-plane and U-plane.