Method and apparatus for session management

1 . A A method at a control plane function, comprising:

determining that a user plane function has been restarted and restoration of an existing communication session with the user plane function is required; and

sending a first session establishment request to the user plane function, wherein the first session establishment request includes a restoration flag that is set to indicate restoring of the existing communication session instead of establishing a new communication session and wherein the restoration flag is comprised in an information element Packet Forwarding Control Protocol Session Establishment Request (PFCPSEReg)-Flags.

2 . The method according to claim 1 , further comprising:

receiving a heartbeat message including a new recovery time stamp from the user plane function, wherein determining that the user plane function has been restarted and restoration of the existing communication session with the user plane function is required is in response to receiving the heartbeat message including the new recovery time stamp.

3 . The method according to claim 1 , further comprising:

sending a second session establishment request to the user plane function, wherein the second session establishment request includes a wildcarded packet detection rule to instruct the user plane function to forward a packet which does not match any other packet detection rules to the control plane function.

4 . The method according to claim 3 , further comprising:

receiving a packet forwarded by the user plane function, wherein the packet does not match said any other packet detection rules,

wherein determining that the user plane function has been restarted and restoration of the existing communication session with the user plane function is required is in response to receiving the packet forwarded by the user plane function.

5 . The method according to claim 3 , wherein the second session establishment request is a PFCPSEReq.

6 . The method according to claim 1 further comprising:

sending session information to the user plane function.

7 . The method according to claim 6 , wherein the session information includes at least one of:

a fully qualified tunnel endpoint identifier of a general packet radio service tunneling protocol user plane tunnel (F-TEID-u) information element and user equipment Internet Protocol (IP) address information element in Packet Detection Information (PDI); and

F-TEID-u information element and user equipment IP address information element in Create Traffic Endpoint.

8 . The method according to claim 1 , wherein the first session establishment request is a PFCPSEReq.

9 . The method according to claim 1 , wherein the control plane function is one of packet data network (PDN) gateway control plane function (PGW-C), serving gateway control plane function (SGW-C), traffic detection function control plane function (TDF-C), and session management function (SMF), and the user plane function is one of PDN gateway user plane function (PGW-U), serving gateway user plane function (SGW-U), traffic detection function user plane function (TDF-U), user plane function (UPF), and packet data unit session anchor user plane function (PSA UPF).

10 . A method at a user plane function, comprising:

restarting the user plane function;

receiving a first session establishment request from a control plane function, wherein the first session establishment request includes a restoration flag that is set to indicate restoring of an existing communication session instead of establishing a new communication session and wherein the restoration flag is comprised in an information element Packet Forwarding Control Protocol Session Establishment Request (PFCPSEReq)-Flags; and

processing the first session establishment request by restoring the existing communication session instead of establishing a new communication session.

11 . The method according to claim 10 , further comprising:

sending a heartbeat message including a new recovery time stamp to the control plane function, wherein receiving the first session establishment request is in response to sending the heartbeat message including the new recovery time stamp.

12 . The method according to claim 11 , further comprising:

receiving a second session establishment request from the control plane function, wherein the second session establishment request includes a wildcarded packet detection rule to instruct the user plane function to forward a packet which does not match any other packet detection rules to the control plane function.

13 . The method according to claim 12 , further comprising:

sending a packet to the control plane function, wherein the packet does not match said any other packet detection rules,

wherein receiving the first session establishment request is in response to sending the packet to the control plane function.

14 . The method according to claim 12 , wherein the second session establishment request is a PFCPSEReq.

15 . The method according to claim 10 further comprising:

receiving session information from the control plane function.

16 . The method according to claim 15 , wherein the session information includes at least one of:

a fully qualified tunnel endpoint identifier of a general packet radio service tunneling Protocol user plane tunnel (F-TEID-u) information element and user equipment Internet Protocol (IP) address information element in Packet Detection Information (PDI); and

F-TEID-u information element and user equipment IP address information element in Create Traffic Endpoint.

17 . An apparatus implemented in a control plane function, comprising:

a processor; and

a memory coupled to the processor, said memory containing instructions which, when executed by said processor, cause said apparatus to:

determine that a user plane function has been restarted and restoration of an existing communication session with the user plane function is required; and

send a first session establishment request to the user plane function, wherein the first session establishment request includes a restoration flag that is set to indicate restoring of the existing communication session instead of establishing a new communication session and wherein the restoration flag is comprised in an information element Packet Forwarding Control Protocol Session Establishment Request (PFCPSEReq)-Flags.

18 . An apparatus implemented in a user plane function, comprising:

a processor; and

a memory coupled to the processor, said memory containing instructions which, when executed by said processor, cause said apparatus to:

restart the user plane function;

receive a first session establishment request from a control plane function, wherein the first session establishment request includes a restoration flag that is set to indicate restoring of an existing communication session instead of establishing a new communication session and wherein the restoration flag is comprised in an information element Packet Forwarding Control Protocol Session Establishment Request (PFCPSEReq)-Flags; and

process the first session establishment request by restoring the existing communication session instead of establishing a new communication session.