Method for establishing plurality of PDN connections by means of CSIPTO

1. A method for establishing a plurality of Packet Data Network (PDN) connections due to Co-ordinated Selected IP Traffic Offload (CSIPTO), the method performed by a user equipment (UE) and comprising:

receiving, by the UE, from a network entity responsible for a control plane, an indication of reallocation of a gateway due to the CSIPTO;

determining, by the UE, whether to maintain or release a previously established first PDN connection based on the indication;

establishing, by the UE, a second PDN connection based on the indication;

marking, by the UE, the first PDN connection as a sub-optimal PDN connection into a first context for the first PDN connection, when the previously established first PDN connection is maintained;

marking, by the UE, the second PDN connection as an optimal PDN connection into a second context for the second PDN connection,

wherein the first context includes all of:

first information indicating that the first PDN connection is the sub-optimal PDN connection,

second information indicating whether to deactivate or release the first PDN connection when a service using the first PDN connection is finished,

third information indicating whether to deactivate or release the first PDN connection when the first PDN connection becomes unnecessary,

fourth information indicating that the first PDN connection is related to a CSIPTO, and

fifth information including an access point name (APN) and a default bearer ID of the second PDN connection;

receiving, by the UE, a request message for releasing the second PDN connection from the network entity;

releasing, by the UE, the second PDN connection, which has been marked as the optimal PDN connection, in response to the received request message; and

deleting, by the UE, the marking of the first PDN connection as the sub-optimal PDN connection.

2. The method of claim 1 , further comprising:

determining whether data associated with a service is to be transmitted to the second PDN connection, based on a type of the service being performed after establishing the second PDN connection.

3. The method of claim 1 , further comprising:

not transmitting a request message for deactivating or releasing the first PDN connection to the network entity when it is determined to maintain the previously established first PDN connection.

4. The method of claim 3 , wherein when the request message for deactivating or releasing the first PDN connection is not transmitted, the network entity marks the first PDN connection as a sub-optimal PDN connection.

5. The method of claim 1 , wherein the indication is received during or after a handover process.

6. The method of claim 1 , wherein the network entity is a Mobility Management Entity (MME), and the gateway is a PDN gateway (P-GW).

7. A user equipment (UE) for establishing a plurality of Packet Data Network (PDN) connections due to Co-ordinated Selected IP Traffic Offload (CSIPTO), the UE comprising:

a transceiver that receives, from a network entity responsible for a control plane, an indication of reallocation of a gateway due to the CSIPTO; and

a processor that determines whether to maintain or release a previously established first PDN connection based on the indication and to establish a new second PDN connection based on the indication,

wherein when the previously established first PDN connection is maintained, the processor further:

marks the first PDN connection as a sub-optimal PDN connection into a first context for the first PDN connection, and

marks the second PDN connection as an optimal PDN connection into a second context for the second PDN connection,

wherein the first context includes all of:

first information indicating that the first PDN connection is the sub-optimal PDN connection,

second information indicating whether to deactivate or release the first PDN connection when a service using the first PDN connection is finished,

third information indicating whether to deactivate or release the first PDN connection when the first PDN connection becomes unnecessary,

fourth information indicating that the first PDN connection is related to a CSIPTO, and

fifth information including an access point name (APN) and a default bearer ID of the second PDN connection;

wherein when a request message for releasing the second PDN connection is received from the network entity, the processor further:

releases the second PDN connection, which has been marked as the optimal PDN connection, and

deleting the marking of the first PDN connection as the sub-optimal PDN connection.

8. The UE of claim 7 , wherein the processor determines whether data associated with a service is to be transmitted to the second PDN connection, based on a type of the service being performed after establishing the second PDN connection.

9. The UE of claim 7 ,

wherein the processor does not control the transceiver to transmit a request message for deactivating or releasing the first PDN connection to the network entity when it is determined to maintain the previously established first PDN connection.

10. The UE of claim 9 , wherein when the request message for deactivating or releasing the first PDN connection is not transmitted, the network entity marks the first PDN connection as a sub-optimal PDN connection.

11. The UE of claim 7 , wherein the indication is received during or after a handover process.

12. The UE of claim 7 , wherein the network entity is a Mobility Management Entity (MME), and the gateway is a PDN gateway (P-GW).