A method for reestablishing a Radio Resource Control, RRC, connection due to Radio Link Failure, RLF, comprising: determining , by a terminal, a Packet Data Convergence Protocol, PDCP, for initiating an RRC connection reestablishment procedure, based on knowledge of the PDCP supported by a base station, wherein the PDCP is a first PDCP or a second PDCP, and wherein the first PDCP is Long Term Evolution, LTE, PDCP, and wherein the second PDCP is New Radio, NR, PDCP; and initiating , by the terminal, the RRC connection reestablishment procedure to the base station, based on the first PDCP or the second PDCP; characterized in that initiating , by the terminal, the RRC connection reestablishment procedure to the base station, based on the first PDCP or the second PDCP comprises: when the terminal knows that the base station supports the second PDCP, transmitting, by the terminal, an RRC connection reestablishment request message to the base station, based on the second PDCP, to start the RRC connection reestablishment procedure between the terminal and the base station based on the second PDCP; and when the terminal does not know that the base station does not support the second PDCP, transmitting, by the terminal, the RRC connection reestablishment request message to the base station based on the first PDCP and resuming, by the terminal, RRC connection with the base station, by using the RRC connection reestablishment request message based on the first PDCP. determining , by a terminal, a Packet Data Convergence Protocol, PDCP, for initiating an RRC connection reestablishment procedure, based on knowledge of the PDCP supported by a base station, wherein the PDCP is a first PDCP or a second PDCP, and wherein the first PDCP is Long Term Evolution, LTE, PDCP, and wherein the second PDCP is New Radio, NR, PDCP; and initiating , by the terminal, the RRC connection reestablishment procedure to the base station, based on the first PDCP or the second PDCP; characterized in that initiating , by the terminal, the RRC connection reestablishment procedure to the base station, based on the first PDCP or the second PDCP comprises: when the terminal knows that the base station supports the second PDCP, transmitting, by the terminal, an RRC connection reestablishment request message to the base station, based on the second PDCP, to start the RRC connection reestablishment procedure between the terminal and the base station based on the second PDCP; and when the terminal does not know that the base station does not support the second PDCP, transmitting, by the terminal, the RRC connection reestablishment request message to the base station based on the first PDCP and resuming, by the terminal, RRC connection with the base station, by using the RRC connection reestablishment request message based on the first PDCP. when the terminal knows that the base station supports the second PDCP, transmitting, by the terminal, an RRC connection reestablishment request message to the base station, based on the second PDCP, to start the RRC connection reestablishment procedure between the terminal and the base station based on the second PDCP; and when the terminal does not know that the base station does not support the second PDCP, transmitting, by the terminal, the RRC connection reestablishment request message to the base station based on the first PDCP and resuming, by the terminal, RRC connection with the base station, by using the RRC connection reestablishment request message based on the first PDCP. <EOS>