Link re-establishment method, apparatus, and system

A communication method carried out by a target radio access node (RAN), comprising:

• receiving, from a user equipment (UE), a re-establishment request message that comprises a second message authentication code (MAC) generation parameter and a MAC of the UE, wherein the second MAC generation parameter comprises:
• an identifier of the UE, and
• a non-access stratum (NAS) parameter;
• determining, according to the identifier of the UE, a control plane (CP) functional entity to serve the UE;
• sending, to the CP functional entity, a first message that comprises the NAS parameter and the MAC of the UE;
• receiving a non-access stratum packet (NAS) packet data unit (PDU) of the UE from the CP functional entity in accordance with successfully verifying the MAC at the CP functional entity;
• and
• sending the NAS PDU to the UE.

A communication apparatus comprising:

• a transceiver;
• at least one processor;
• and
• one or more memories coupled to the at least one processor and storing programming instructions for execution by the at least one processor to cause the communication apparatus to carry out a method comprising:
• receiving, from a target radio access node (RAN), a first message that comprises a non-access stratum (NAS) parameter and a message authentication code (MAC);
• verifying the MAC based on the NAS parameter;
• and
• sending, in accordance with successfully verifying the MAC, a second message to a source RAN,
• wherein the second message is used to request the source RAN to send an undelivered NAS packet data unit (PDU) of a user equipment (UE) to the CP functional entity.

A communication apparatus, comprising:

• a transceiver;
• at least one processor;
• and
• one or more memories coupled to the at least one processor and storing programming instructions for execution by the at least one processor to cause the communication apparatus to carry out a method comprising:
• receiving, from a user equipment (UE), a re-establishment request message that comprises a second message authentication code (MAC) generation parameter and a MAC of the UE, wherein the second MAC generation parameter comprises:
• an identifier of the UE, and
• a non-access stratum (NAS) parameter;
• determining, according to the identifier of the UE, a control plane (CP) functional entity to serve the UE;
• sending, to the CP functional entity, a first message that comprises the NAS parameter and the MAC of the UE;
• receiving a non-access stratum packet (NAS) packet data unit (PDU) of the UE from the CP functional entity in accordance with successfully verifying the MAC at the CP functional entity;
• and
• sending the NAS PDU to the UE.