A communication method, comprising: in a procedure where a RRC connection between a first radio terminal (100-1) and a first base station (200-1) is temporarily suspended, the first base station (200-1) transmitting to a first radio terminal (100-1) a first resumption identifier associated with context information of the first radio terminal (100-1), the first resumption identifier comprising a first predetermined identifier and a first additional identifier, wherein the first predetermined identifier indicating a first predetermined information; and when a RRC connection between a second radio terminal (100-2) and a second base station (200-2) is temporarily suspended, receiving at the first base station (100-1), from a second radio terminal (100-2), a RRC connection resumption request containing a second resumption identifier of a different length than the first resumption identifier, associated with context information of the second radio terminal (100-2), wherein the second resumption identifier comprises a second predetermined identifier of a different length than the first predetermined identifier and a second additional identifier of a different length than the first additional identifier, wherein the second predetermined identifier indicating a second predetermined information; the first base station (200-1) grasping the length of the second resumption identifier by identifying the length of the second additional identifier; wherein the first predetermined information comprises information for identifying the first base station (200-1) and the second predetermined information comprises information for identifying the second base station (200-2). in a procedure where a RRC connection between a first radio terminal (100-1) and a first base station (200-1) is temporarily suspended, the first base station (200-1) transmitting to a first radio terminal (100-1) a first resumption identifier associated with context information of the first radio terminal (100-1), the first resumption identifier comprising a first predetermined identifier and a first additional identifier, wherein the first predetermined identifier indicating a first predetermined information; and when a RRC connection between a second radio terminal (100-2) and a second base station (200-2) is temporarily suspended, receiving at the first base station (100-1), from a second radio terminal (100-2), a RRC connection resumption request containing a second resumption identifier of a different length than the first resumption identifier, associated with context information of the second radio terminal (100-2), wherein the second resumption identifier comprises a second predetermined identifier of a different length than the first predetermined identifier and a second additional identifier of a different length than the first additional identifier, wherein the second predetermined identifier indicating a second predetermined information; the first base station (200-1) grasping the length of the second resumption identifier by identifying the length of the second additional identifier; wherein the first predetermined information comprises information for identifying the first base station (200-1) and the second predetermined information comprises information for identifying the second base station (200-2). <EOS>