Session transfer method and method for supporting session continuity

A method for supporting session continuity for a terminal in a server, the method comprising:

• sending, by a server, a session continuity operator policy to a first terminal which is engaged in an ongoing session with a second terminal, wherein the session continuity operator policy includes a parameter indicating a preferred network for a transfer of the ongoing session, and session continuity level information including one of a first level indicating that the first terminal starts a session transfer to the preferred network and a second level indicating that starting of the session transfer is performed based on a decision of the first terminal;
• receiving, by the server, a first session invite message from the first terminal via a target network within the preferred network, unless the session continuity level information of the session continuity operator policy is the second level and the first terminal decides not to start the session transfer;
• and
• sending, by the server, a second session invite message to the second terminal to achieve session continuity to the target network after receiving the first session invite message from the first terminal.