Methods and apparatus are provided for the RRC message segmentation. In one novel aspect, the UE obtains the size Z of the RRC message and the size limit L of the underlying transmission at layer S of the UE protocol stack, wherein the layer S either the RRC layer, the PDCP layer, or a sublayer between an RRC layer and a PDCP layer. The UE triggers RRC message segmentation upon detecting Z is greater than L. In another embodiment, the layer R of the protocol stack of the UE receives, in order, a sequence of chunks of an RRC message, reassembles of the RRC message, wherein the layer R is selected from a same layer as the layer S and a layer higher than the layer S. In one novel aspect, the size limitation L is either predefined or obtained through network notification or UE inquiry.