The present invention provides a traction device for a terrain engaging element. When the latching module engages the main body, the cover is closed and fixed to the main body. A user terminal calls a home server, which issues a connection request to an Internet service provider. The Policy and Charging Rules Function node determines a PDN GW IP address to be used for establishing the session based on policies for the first user equipment and transmits the PDN GW IP address through the direct MMES4-SGSN-PCRF interface to the MMES4-SGSN.