Data transmission method and apparatus, and service switching method and apparatus

A data transmission method, comprising:

• acquiring, by a first terminal, first information of quality of service (QOS) of a to- be-transmitted data packet on a sidelink;
• establishing, by the first terminal, a sidelink bearer;
• and
• mapping, by the first terminal and according to the first information, the to-be-transmitted data packet to the sidelink bearer for transmission to a second terminal;
• wherein the first information comprises second information and fourth information, wherein the second information comprises a fifth-generation mobile system quality of service identifier (5QI) and a transmission range corresponding to the to-be- transmitted data packet, and the fourth information comprises sidelink QoS rules;
• wherein establishing the sidelink bearer comprises:
• receiving, by the first terminal from a base station, sidelink bearer configuration information;
• and establishing, by the first terminal, the sidelink bearer according to the sidelink bearer configuration information, wherein the sidelink bearer configuration information comprises a bearer identifier and a service data adaptation protocol (SDAP) configuration which comprises a list of QoS flows mapped to the sidelink bearer;
• wherein mapping, by the first terminal according to the first information, the to-be-transmitted data packet to the sidelink bearer for the transmission comprises:
• mapping, by the first terminal and according to the sidelink QoS rules and the sidelink bearer configuration information, the to-be-transmitted data packet to the sidelink bearer for the transmission.