KR20170053319A - Mobility Management Entity, Serving Gateway, Packet Data Network Gateway, and System - Google Patents

Abstract

According to an embodiment of the present invention, a mobility management entity (MME) constituting an evolved packet core (EPC) receives a downlink data notification (DDN) message according to reception of a transmission control protocol (TCP) packet to be transmitted to user equipment (UE), from a serving gateway (S-GW) when information on a subscriber of the UE, which is stored in the MME, is deleted in an idle state, and then generates a message indicating that the information on the subscriber is deleted in a response to the DDN message to transmit the same to the S-GW. The present invention provides an MME, an S-GW, a packet data network gateway (P-GW), and a system, which are capable of reducing unnecessary traffic occurring when information on a subscriber is deleted due to failure in an EPC.

Description

MME, S-GW, P-GW and system {Mobility Management Entity, Serving Gateway, Packet Data Network Gateway, and System}

The present invention relates to an MME, an S-GW, a P-GW and a system, and more particularly, to an MME, an S-GW, a P-GW and a system that can reduce unnecessary traffic.

The LTE (Long Term Evolution) network is divided into the LTE (E-UTRAN) related technologies and the EPC (Enhanced Packet Core) . Since the LTE network is an E2E all-IP network, all traffic flows from a wireless link that a user terminal connects to a base station to a packet data network (PDN) that connects to a final service provider operate on an IP basis.

When a user who has purchased an LTE terminal subscribes to a mobile communication service provider (hereinafter referred to as "carrier") network, a service type and a fee type are selected, and the subscriber configures a subscription profile based on the subscription information Control the subscriber's use of the service.

The LTE terminal accesses the LTE network, acquires an IP (Internet Protocol) address, establishes a TCP (Transmission Control Protocol) session, and can access the Internet. At this time, the LTE terminal remains in a state in which the TCP session is not terminated even after downloading the app or viewing the moving picture by accessing the server.

In this state, when the battery of the LTE terminal is exchanged and the subscriber information is deleted due to the change of the terminal's IP address or the failure in the EPC by accessing the LTE network, the server keeps the TCP session, And unnecessary traffic is generated until the TCP session is deleted in the future.

3GPP TS 24.301 (V13.3.0) 3GPP TS 29.274 (V13.3.0) 3GPP TS 29.281 (V12.0.0)

The present invention is to provide an MME, an S-GW, a P-GW, and a system capable of reducing unnecessary traffic generated when subscriber information is deleted due to a failure in the EPC.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

According to an aspect of the present invention, there is provided an MME (Mobility Management Entity) constituting an EPC (Evolved Packet Core) according to an embodiment of the present invention includes a UE (User Equipment) stored in the MME in an idle state, (Downlink Data Notification) message according to the reception of a TCP (Transmission Control Protocol) packet to be transmitted to the UE from the S-GW (Serving Gateway) when the subscriber information of the DDN message is deleted, A message indicating that the subscriber information has been deleted may be generated and transmitted to the S-GW.

According to an embodiment, the message indicating that the subscriber information has been deleted is a DDN ACK message.

According to the embodiment, the DDN ACK message may indicate 'Context Not Found' as the Cause information.

According to an embodiment, the deleted subscriber information may be at least one of an International Mobile Subscriber Identity (IMSI), an Internet Protocol (IP) address of the UE, a Globally Unique Temporary Identifier (GUTI), and a Tracking Area Identity (TAI).

The S-GW (Serving Gateway) constituting the EPC (Evolved Packet Core) according to an embodiment of the present invention is configured such that when the subscriber information of UE (User Equipment) stored in the S-GW is deleted in an idle state , And upon receiving a TCP (Transmission Control Protocol) packet to be transmitted to the UE, transmits a message to the Packet Data Network Gateway (P-GW) to inform the bearer of the error.

According to an embodiment, the message may be an " Error Indication " message.

According to an embodiment, if the bearer on which the TCP packet is received is a default bearer, the message may control to delete subscriber information stored in the P-GW.

According to an embodiment, the deleted subscriber information may be at least one of IMSI and TAI.

The Packet Data Network Gateway (P-GW) constituting the EPC (Evolved Packet Core) according to an embodiment of the present invention deletes subscriber information of UE (User Equipment) stored in the P-GW in an idle state , When a TCP (Transmission Control Protocol) packet to be transmitted to the UE is received, the TCP packet is regarded as an invalid request, and a TCP reset can be requested to a PDN (Packet Data Network).

According to an embodiment, the TCP reset can control the PDN to delete TCP session information corresponding to the TCP packet.

According to an embodiment, the deleted subscriber information may be at least one of an IMSI, an IP address of the UE, and a TAI.

A system including an MME (Mobility Management Entity), an S-GW (Serving Gateway) and a P-GW (Packet Data Network Gateway) according to an embodiment of the present invention, GW, and P-GW, if the subscriber information of a User Equipment (UE) stored in at least one of the P-GW and the P-GW is deleted, upon receipt of a TCP (Transmission Control Protocol) packet to be transmitted to the UE, It is possible to request a TCP reset using a PDN (Packet Data Network).

According to the MME, the S-GW, and the P-GW and the system according to an embodiment of the present invention, the subscriber information maintained by the MME, the S-GW, or the P- It is possible to reduce unnecessary traffic and signaling by lowering the buffer usage rate in the EPC by deleting all the session information.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

1 is a configuration diagram of an LTE network according to the present invention.
FIG. 2 is a view for explaining traffic flows on an LTE network for facilitating understanding of the present invention. FIG.
3 is a flowchart illustrating a method of operating an LTE network according to an embodiment of the present invention.
4 is a flowchart illustrating an operation method of an LTE network according to another embodiment of the present invention.
5 is a flowchart illustrating a method of operating an LTE network according to another embodiment of the present invention.

Hereinafter, at least one embodiment related to the present invention will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

1 is a configuration diagram of an LTE network according to the present invention.

1, an LTE network includes a UE (User Equipment) 10, an Evolved Node B (eNB) 20, an S-GW (Serving Gateway) 30, a Packet Data Network Gateway , 40, an MME (Mobility Management Entity) 50, and an HSS (Home Subscriber Server) 60.

 The UE 10 is an LTE user terminal and is connected to the eNB 20 via the LTE-Uu interface 15. Here, the LTE Uu interface 15 defines a control plane for transmitting and receiving a control message as a wireless interface and a user plane for providing user data.

The eNB 20 provides a radio interface to the UE 10 and provides radio resource management functions such as radio bearer control, radio admission control, dynamic radio resource allocation, load balancing and inter-cell interference control do.

The S-GW 30 is an end point of an evolved universal terrestrial radio access network (E-UTRAN) and an evolved packet core (EPC), and an anchor point at handover between the eNB 20 and the 3GPP system do. The E-UTRAN includes at least one eNB 20 and the EPC 100 includes an S-GW 30, a P-GW 40, an MME 50, and an HSS 60.

The P-GW 40 connects the UE 10 to an external PDN (Packet Data Network) 110 and performs a packet filtering function. In addition, the P-GW 40 assigns an IP address to the UE 10 and operates as a mobility anchoring point when performing handover between the 3GPP system and the non-3GPP system. In particular, the P-GW 40 receives the Policy and Charging Control (PCC) rules from the Policy and Charging Rule Function (PCRF), applies it to the corresponding service flow, Billing function. The PCRF provides policy control decisions and billing control functions as entities that perform policy and billing control.

The HSS 60 is a central database for storing a subscriber profile, and provides the MME 50 with user authentication information and a user profile.

Hereinafter, the interface between the elements constituting the LTE network 1 will be briefly described.

The LTE-Uu 15 provides a control plane and a user plane with a radio interface between the UE 10 and the eNB 20. [

The S1-U 25 is an interface between the eNB 20 and the S-GW 30, and provides a user plane. At this time, GTP (GPRS Tunneling Protocol) tunneling (GTP-U) for each bearer is provided.

X2 26 is an interface between the two eNBs 20, providing a control plane and a user plane. The X2-AP protocol is used in the control plane and GTP tunneling per bearer for data forwarding in the X2 handover in the user plane.

S5 35 is an interface between the S-GW 30 and the P-GW 40, providing a control plane and a user plane. At this time, the user plane provides bearer-specific GTP tunneling (GTP-U), and the control plane provides GTP tunnel management (GTP-C).

SGi 45 defines a user plane and a control plane as an interface between the P-GW 40 and the PDN 110. In the user plane, IETF based IP packet forwarding protocol is used, and in the control plane, protocols such as DHCP and RADIUS / Diameter are used.

S11 55 defines a control plane as an interface between the MME 50 and the S-GW 30, and GTP tunneling for each bearer is provided.

The S6a 65 is provided with a control plane as an interface between the HSS 60 and the MME 50, a Diameter protocol is used, and is used to exchange UE subscription information and authentication information.

The S1-MME 75 is an interface between the eNB 20 and the MME 50, and a control plane is defined, and the S1-AP protocol is used.

FIG. 2 is a view for explaining traffic flows on an LTE network for facilitating understanding of the present invention. FIG.

Referring to FIG. 2, an Internet traffic flow in the user plane of the LTE network reference model is shown. Reference numeral 200a denotes a traffic flow from the UE 10 to the Internet, hereinafter referred to as "uplink traffic flow", 200b denotes a traffic flow from the Internet to the UE 10, hereinafter referred to as " Business card.

IP packets are transmitted over the GTP tunnel on the S1-U (25) and S5 (35) interfaces, respectively. Here, the GTP tunnel is set for each EPS bearer through control signaling when the UE 10 initially connects to the LTE network.

Since a plurality of EPS bearers are set on one of the S1-U 25 and the S5 (35) interfaces, a tunnel endpoint identifier (TEID) is allocated upwardly and downwardly in each GTP tunnel establishment to distinguish them. When a GTP tunnel is set in the S1-U (25) interface, a TEID (UL S1-TEID) having an end point is allocated to the S-GW 20 upward and a TEID (DL S1-TEID) having an end point is allocated to the eNB 20 -TEID). Similarly, when a GTP tunnel is established in the S5 (35) interface, a TEID (UL S5-TEID) having an end point in the P-GW 40 and a TEID (DL S5-TEID) having an end point in the S- S5-TEID).

The eNB 20, the S-GW 30 and the P-GW 40 transmit a GTP tunnel header to the GTP packet header when the user IP packet is transmitted through the GTP tunnel on the S1-U 25 and the S5 The TEID that is allocated at the time of generation is inserted and transmitted. The S-GW 30 must have mapping information between the UL S1-TEID and the UL S5-TEID in order to terminate the S1-GTP tunnel in the upward direction and to transmit the user IP packet to the S5-GTP tunnel. Likewise, in the downlink, mapping information between DL S5-TEID and DL S1-TEID must be maintained.

Hereinafter, referring to FIG. 2, a procedure for each entity to process uplink and downlink Internet traffic flows will be described in detail.

First, in the uplink, the UE 10 transmits internally generated user IP packets to the eNB 20 via the LTE-Uu 15 interface. The eNB 20 adds the IP address of the S-GW 30 to the destination IP address, the source IP address of the eNB 20, the S1 GTP header having the UL S1-TEID set to the TEID, To the S-GW 30 via the GTP tunnel.

When receiving the user IP packet through the S1 GTP tunnel, the S-GW 30 sets the IP address of the P-GW 40 as the destination address, the IP address of the S-GW 30 as the originating address, and the UL S5-TEID as the TEID Configure the configured S5 GTP header. Then, the S5 GTP header is added to the user IP packet and transmitted to the P-GW 40 through the S5 GTP tunnel.

Subsequently, the P-GW 40 controls the S5 GTP header to extract user IP packets, and then transmits them to the Internet through IP routing.

Referring to the downlink traffic flow, the P-GW 40 receives a TCP packet directed to the UE 10 via the Internet. The P-GW 40 adds the S5 GTP header including the IP address of the S-GW 30 as the destination address, the IP address of the P-GW 40 as the source address and the DL S5-TEID as the TEID to the TCP packet, Packet, and transmits the packet to the S-GW 30 through the S5-GTP tunnel.

The S-GW 30 transmits the IP address of the eNB 20 as the destination address, the IP address of the S-GW 30 as the originating address, and the DL S1-TEID as the S1 GTP And transmits the header to the eNB 20 through the S1 GTP tunnel.

The eNB 20 transmits the user IP packet from which the S1 GTP header has been removed to the UE 10 via a data radio bearer (DRB), which is a bearer on the radio link.

It should be noted that the GTP tunnel of FIG. 2 is a user plane GTP tunnel for delivering user IP packets, hereinafter referred to as a "GTP-U tunnel ".

3 is a flowchart illustrating a method of operating an LTE network according to an embodiment of the present invention.

Referring to FIG. 3, the UE 10 attempts initial attach to the mobile communication network after the power is turned on. That is, the UE 10 synchronizes with a specific eNB 20 through a public land mobile network (PLMN) and a cell search process, and then transmits an "Attach Request" message to the MME 50. Thereafter, when mutual authentication between the UE 10 and the MME 50 is successful, the MME 50 downloads the subscriber profile from the HSS 60 and creates an EPS session and a default EPS bearer.

In the process of generating the default EPS bearer, the EPC 100 allocates an ID to be used for network connection or registration to the user. The P-GW 40 allocates an IP address of the UE 10, and the MME 50 transmits a GUTI Unique Temporary Identifier) and a TAI (Tracking Area Identifier) list. This information (IP address, GUTI, TAI list) is transmitted from the MME 50 to the UE 10 via the "Attach Accept" message.

The state in which the initial access procedure has been successfully performed can be defined as an "Attached" state as shown in FIG. 3, and the UE 10 can use the service (Internet, etc.) through the network.

If the UE 10 is using the service after the initial connection is successfully completed and the service is not used for a certain period of time, the S1 bearer and the S1 signaling connection are released and the UE 10 is in an idle state .

In the idle state, resources allocated by the radio access network (E-UTRAN or eNB 20) are released, and resources allocated by the EPC 100 are maintained.

That is, even if the UE 10 enters the idle state, the subscriber information (IP address, GUTI, TAI list, etc.) stored in the MME 50, the S-GW 30 and the P- The information used to connect to the eNB 20 to transmit and receive traffic is released.

Specifically, in the MME 50, the S1AP UE ID (the ID of the UE 10 used in the S1 signaling connection), the ECGI (the cell information to which the UE 10 is connected), the S1 TEID / DL The International Mobile Subscriber Identity (IMSI) excluding the TEID information, the IP address of the UE 10, the GUTI, and the TAI.

In the S-GW 30, information such as IMSI and TAI excluding the ECGI and the S1 TEID / DL are held.

In the P-GW 40, information such as the IMSI excluding the ECGI, the IP address of the UE 10, TAI and the like are held.

Hereinafter, information related to the UE 10 held in each of the MME 50, the S-GW 30 and the P-GW 40 in the idle state is defined as subscriber information, and the subscriber information is down- And corresponds to the essential information for transmitting the downlink traffic to the UE 10 when the traffic is generated.

It is assumed that the subscriber information maintained by the MME 50 in the idle state has been deleted due to a failure on the EPC 100 system. Therefore, the TCP packet to be transmitted to the UE 10 can not be normally transmitted to the UE 10 due to the absence of the subscriber information. The deleted subscriber information may be at least one of an IMSI, an IP address of the UE 10, a GUTI, and a TAI.

However, the PDN 110, which can not recognize this state, transmits a TCP packet to be transmitted to the UE 10 to the P-GW 40 (S10).

The P-GW 40 transmits the TCP packet to the corresponding S-GW 30 through the S5-GTP tunnel using the held subscriber information (S11).

The S-GW 30 can not transmit the downlink S1 bearer to the eNB 20 since the downlink S1 bearer is released (S1 TEID / DL is deleted), buffering the received TCP packet, ). Then, the S-GW 30 transmits a DDN (Downlink Data Notification) message to the MME 50 to notify the UE 10 that a signaling connection and a bearer setup are required (S12).

The MME 50 transmits a DDN ACK message to the S-GW 30 in response to the DDN message. The DDN ACK message may indicate that the subscriber information has been deleted (e.g., the Cause information is " Context Not Found ") (S13). "Context Not Found" indicates that the MME 50 does not hold the corresponding subscriber information, and the MME 50 may not perform a paging operation for at least one TAL corresponding to the DDN message.

Upon receiving the DDN ACK message, the S-GW 30 transmits a Delete Session Request to the P-GW 40 for requesting deletion of subscriber information of the P-GW 40 in response to the DDN ACK message. , And can delete the held subscriber information (S14).

In step S15, the P-GW 40 deletes the subscriber information held in response to the session deletion request, and transmits a session deletion response to the S-GW 30 in response to the session deletion request in step S16. .

Thereafter, the PDN 110 transmits the TCP packet to be transmitted to the UE 10 to the P-GW 40 again (S17). At this time, the TCP packet may be the same as or different from the TCP packet transmitted in step S10.

Since the P-GW 40 has deleted the subscriber information of the UE 10, the P-GW 40 considers the TCP packet as an invalid request and requests a TCP reset (S18).

Upon receiving the TCP reset, the PDN 110 may delete the TCP session associated with the TCP packet (S19). Therefore, the PDN 110 does not transmit the TCP packet to the P-GW 40 even if the downlink traffic to the UE 10 occurs thereafter.

That is, according to the EPC 100 according to the embodiment of the present invention, when the subscriber information held by the MME 50 is deleted due to a failure in the EPC 100 system, It is possible to reduce the buffer utilization rate in the mobile station 100 and prevent unnecessary traffic and signaling from occurring.

4 is a flowchart illustrating an operation method of an LTE network according to another embodiment of the present invention.

3 and 4, it is assumed that the subscriber information maintained by the S-GW 30 in the "Attached" state and the "Idel" state described in FIG. 3 has been deleted due to a failure on the EPC 100 system . Therefore, the TCP packet to be transmitted to the UE 10 can not be normally transmitted to the UE 10 due to the absence of the subscriber information. The deleted subscriber information may be at least one of IMSI and TAI.

However, the PDN 110, which can not recognize such a state, transmits a TCP packet to be transmitted to the UE 10 to the P-GW 40 (S20).

The P-GW 40 transmits the TCP packet to the corresponding S-GW 30 through the S5-GTP tunnel using the held subscriber information (S21).

The S-GW 30 transmits the "Error Indication" message to the P-GW 40 to notify the error of the corresponding bearer of the S5-GTP tunnel without transmitting the DDN message because the subscriber information is deleted ( S22).

Upon receiving the message " Error Indication ", the P-GW 40 deletes the corresponding bearer information. If the bearer is the default bearer, the P-GW 40 deletes the subscriber information for the UE 10 (S23) .

On the other hand, if the corresponding bearer is not the default bearer, the corresponding bearer information is deleted. However, due to the generation of the repeated TCP packets, the above operations are repeated so that only the default bearer remains in the S5- The subscriber information may be deleted.

Thereafter, the PDN 110 transmits the TCP packet to be transmitted to the UE 10 to the P-GW 40 again (S24). At this time, the TCP packet may be the same as or different from the TCP packet transmitted in step S20.

Since the P-GW 40 has deleted the subscriber information of the UE 10, the P-GW 40 considers the TCP packet as an invalid request and requests a TCP reset (S25).

Upon receiving the TCP reset, the PDN 110 may delete the TCP session associated with the TCP packet (S26). Therefore, the PDN 110 does not transmit the TCP packet to the P-GW 40 even if the downlink traffic to the UE 10 occurs thereafter.

That is, according to the EPC 100 according to the embodiment of the present invention, when the subscriber information held by the S-GW 30 is deleted due to a failure in the EPC 100 system, , The buffer utilization rate in the EPC 100 may be lowered so that unnecessary traffic and signaling can be prevented.

5 is a flowchart illustrating a method of operating an LTE network according to another embodiment of the present invention.

3 and 5, it is assumed that the subscriber information maintained by the P-GW 40 in the "Attached" state and the "Idel" state described in FIG. 3 has been deleted due to a failure on the EPC 100 system . Therefore, the TCP packet to be transmitted to the UE 10 can not be normally transmitted to the UE 10 due to the absence of the subscriber information. The deleted subscriber information may be at least one of an IMSI, an IP address of the UE 10, and a TAI.

However, the PDN 110, which can not recognize this state, transmits a TCP packet to be transmitted to the UE 10 to the P-GW 40 (S30).

The P-GW 40 does not transmit the TCP packet to the S-GW 30 as it is, and regards the TCP packet as an invalid request because the subscriber information of the UE 10 is deleted, (S31).

Upon receiving the TCP reset, the PDN 110 may delete the TCP session information corresponding to the TCP packet (S32). Therefore, the PDN 110 does not transmit the TCP packet to the P-GW 40 even if the downlink traffic to the UE 10 occurs thereafter.

That is, according to the EPC 100 according to the embodiment of the present invention, when the subscriber information held by the P-GW 30 is deleted due to a failure in the EPC 100 system, , The buffer utilization rate in the EPC 100 may be lowered so that unnecessary traffic and signaling can be prevented.

The operation method of the EPC 100 described above can be implemented as a computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording media storing data that can be decoded by a computer system. For example, it may be a ROM (Read Only Memory), a RAM (Random Access Memory), a magnetic tape, a magnetic disk, a flash memory, an optical data storage device, or the like. In addition, the computer-readable recording medium may be distributed and executed in a computer system connected to a computer network, and may be stored and executed as a code readable in a distributed manner.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that various modifications and changes may be made.

Claims (20)

In an MME (Mobility Management Entity) constituting an EPC (Evolved Packet Core)
When a subscriber information of a user equipment (UE) stored in the MME is deleted in an idle state, a DDN (Downlink Data Notification) message according to reception of a TCP (Transmission Control Protocol) packet to be transmitted to the UE is transmitted to an S- (Serving Gateway)
Generates a message indicating that the subscriber information has been deleted in response to the DDN message, and transmits the generated message to the S-GW. The method according to claim 1,
The message indicating that the subscriber information has been deleted is a DDN ACK message MME. 3. The method of claim 2,
The DDN ACK message indicates that the Cause information indicates " Context Not Found ". The method according to claim 1,
Wherein the deleted subscriber information is at least one of an International Mobile Subscriber Identity (IMSI), an Internet Protocol (IP) address of the UE, a Globally Unique Temporary Identifier (GUTI), and a Tracking Area Identity (TAI). In an S-GW (Serving Gateway) constituting an EPC (Evolved Packet Core)
(UE) subscriber information stored in the S-GW in an idle state is deleted, when a TCP (Transmission Control Protocol) packet to be transmitted to the UE is received,
And an S-GW for transmitting a message for notifying an error of the bearer corresponding to the TCP packet to a Packet Data Network Gateway (P-GW). 6. The method of claim 5,
The message is an " Error Indication " message, S-GW. 6. The method of claim 5,
And the S-GW controls to delete subscriber information stored in the P-GW if the bearer on which the TCP packet is received is a default bearer. 6. The method of claim 5,
The deleted subscriber information is at least one of IMSI and TAI. In a P-GW (Packet Data Network Gateway) constituting an EPC (Evolved Packet Core)
When a subscriber information of a UE stored in the P-GW is deleted in an idle state, when receiving a TCP (Transmission Control Protocol) packet to be transmitted to the UE,
A P-GW that considers the TCP packet as an invalid request and requests a TCP reset with a PDN (Packet Data Network). 10. The method of claim 9,
Wherein the TCP reset controls the PDN to delete TCP session information corresponding to the TCP packet. 10. The method of claim 9,
The deleted subscriber information is at least one of an IMSI, an IP address of the UE, and a TAI. 1. A system including a Mobility Management Entity (MME), a Serving Gateway (S-GW), and a Packet Data Network Gateway (P-GW)
(Transmission Control Protocol) packet to be transmitted to the UE when the subscriber information of the User Equipment (UE) stored in at least one of the MME, the S-GW, and the P-GW is deleted in an idle state Upon receipt,
The TCP packet is regarded as an invalid request, and a TCP reset is requested by a PDN (Packet Data Network). 13. The method of claim 12,
When the subscriber information of the UE stored in the MME is deleted, when the MME receives the DDN message according to the reception of the TCP packet from the S-GW,
Generates a message indicating that the subscriber information has been deleted in response to the DDN message, and transmits the message to the S-GW. 14. The method of claim 13,
Wherein the S-GW transmits a Delete Session Request to the P-GW in response to a message indicating that the subscriber information has been deleted, for requesting deletion of subscriber information of the P-GW. 15. The method of claim 14,
The P-GW deletes the subscriber information according to the session deletion request, and when receiving the TCP packet to be transmitted to the UE, the P-GW considers the TCP packet as an invalid request and requests the TCP reset to the PDN system. 14. The method of claim 13,
Wherein the message indicating that the subscriber information has been deleted is a DDN ACK message in which the Cause information indicates " Context Not Found ". 13. The method of claim 12,
When the subscriber information of the UE stored in the S-GW is deleted, the S-GW receives the TCP packet and transmits a message to the P-GW to inform the bearer of the error corresponding to the TCP packet . 18. The method of claim 17,
And wherein if the bearer on which the TCP packet is received is a default bearer, the message controls to delete subscriber information stored in the P-GW. 13. The method of claim 12,
When the subscriber information of the UE stored in the P-GW is deleted, when the P-GW receives the TCP packet, the P-GW regards the TCP packet as an invalid request and requests the TCP reset to the PDN. 13. The method of claim 12,
Wherein the TCP reset controls the PDN to delete TCP session information corresponding to the TCP packet.

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