One disclosure of the present specification provides a method for operating in relay user equipment (UE). The method may comprise the steps of: receiving a communication request message directly from a first remote UE; performing a procedure for establishing an access and mobility management function (AMF) entity and a protocol data unit (PDU) session; and storing mapping information between an identifier of a PC5 link with the first remote UE and an identifier of the PDU session on the basis of the PDU session being established for an unstructured PDU session type for unstructured traffic.