1. A method for transmitting data comprising:determining, by a core network control entity, after receiving a first message sent by user equipment, whether first indication information is set,
wherein the first indication information indicates that a server buffers downlink data to be sent to the user equipment,
wherein the first indication information is associated with a validity period of the downlink data, and
wherein the first message is a tracking area update (TAU) message or a routing area update (RAU) message; and
in response to determining the first indication information is to be set in the core network control entity, establishing, by the core network control entity, a user plane bearer or a packet data protocol (PDP) context, and triggering the server that buffers the downlink data to send the downlink data to the user equipment through the user plane bearer or the PDP context, wherein establishing the user plane bearer comprises:
establishing radio bearers between the user equipment and an eNodeB that are associated with all activated bearers of the user equipment, and
establishing user plane connections between a serving gateway and the eNodeB that are associated with all activated bearers of the user equipment.