A communication system, comprising a target mobility management network element and a target control plane gateway; wherein the target control plane gateway being configured to: receive location information of a user equipment from the target mobility management network element; select a first user plane gateway for the user equipment according to the location information of the user equipment; and establish a data forwarding tunnel passing through a source user plane gateway serving the user equipment, the first user plane gateway, and a target base station serving the user equipment, wherein the data forwarding tunnel is used for transmitting downlink user plane data of the user equipment; wherein the target mobility management network element being configured to: receive (S503, S603, 901) a forwarding relocation request from a source mobility management network element serving a user equipment, wherein the forwarding relocation request comprises the location information of the user equipment; select (S504, S604, 902) the target control plane gateway of the user equipment according to the location information of the user equipment; send (S509, S609, 903) the location information of the user equipment to the target control plane gateway; send (S514, S616, 904) a data forwarding tunnel establishment request to the target control plane gateway to request establishment of the data forwarding tunnel. wherein the target control plane gateway being configured to: receive location information of a user equipment from the target mobility management network element; select a first user plane gateway for the user equipment according to the location information of the user equipment; and establish a data forwarding tunnel passing through a source user plane gateway serving the user equipment, the first user plane gateway, and a target base station serving the user equipment, wherein the data forwarding tunnel is used for transmitting downlink user plane data of the user equipment; receive location information of a user equipment from the target mobility management network element; select a first user plane gateway for the user equipment according to the location information of the user equipment; and establish a data forwarding tunnel passing through a source user plane gateway serving the user equipment, the first user plane gateway, and a target base station serving the user equipment, wherein the data forwarding tunnel is used for transmitting downlink user plane data of the user equipment; wherein the target mobility management network element being configured to: receive (S503, S603, 901) a forwarding relocation request from a source mobility management network element serving a user equipment, wherein the forwarding relocation request comprises the location information of the user equipment; select (S504, S604, 902) the target control plane gateway of the user equipment according to the location information of the user equipment; send (S509, S609, 903) the location information of the user equipment to the target control plane gateway; send (S514, S616, 904) a data forwarding tunnel establishment request to the target control plane gateway to request establishment of the data forwarding tunnel. receive (S503, S603, 901) a forwarding relocation request from a source mobility management network element serving a user equipment, wherein the forwarding relocation request comprises the location information of the user equipment; select (S504, S604, 902) the target control plane gateway of the user equipment according to the location information of the user equipment; send (S509, S609, 903) the location information of the user equipment to the target control plane gateway; send (S514, S616, 904) a data forwarding tunnel establishment request to the target control plane gateway to request establishment of the data forwarding tunnel.