Method and apparatus for supporting call according to plurality of modes

A method for supporting, by a call server, switching between a plurality of modes for a call, the method comprising:

• performing a capability negotiation for a call between a first terminal and a second terminal;
• and
• establishing a first connection between the first terminal and the call server according to a first mode among the plurality of modes for the call between the first terminal and the second terminal after performing the capability negotiation,
• wherein the performing of the capability negotiation comprises receiving a first message comprising information indicating a media attribute for each of two or more modes among the plurality of modes from the first terminal.

A first terminal for supporting switching between a plurality of modes for a call, the first terminal comprising:

• a transceiver;
• and
• at least one processor coupled to the transceiver,
• wherein the at least one processor is configured to:
• perform a capability negotiation for a call with a second terminal,
• establish a first connection between the first terminal and a call server according to a first mode among the plurality of modes for the call with the second terminal after performing the capability negotiation, and
• transmit a first message comprising information indicating a media attribute of each of two or more modes of the plurality of modes to the call server in order to perform the capability negotiation.

A call server for supporting switching between a plurality of modes for a call, the call server comprising:

• a transceiver;
• and
• at least one processor coupled to the transceiver,
• wherein the at least one processor is configured to:
• perform a capability negotiation for a call between a first terminal and a second terminal,
• establish a first connection between the first terminal and the call server according to a first mode among the plurality of modes for the call between the first terminal and the second terminal after performing the capability negotiation, and
• receive a first message comprising information indicating a media attribute for each of two or more modes among the plurality of modes from the first terminal in order to perform the capability negotiation.