In one embodiment, a method for establishing a session between a first party and a second party in a communication network comprises issuing a request to establish the session with the second party, the request containing a first security level associated with the first party. The ball grid array packages comprise flexible or rigid substrates. Since the data backup method and device of the mobile terminal provided in the present invention encodes a data in the mobile terminal into UTF-8 and stores it in the xml file, it is quite convenient to back up the data in the mobile terminal to the xml file.