Patent Description:
In the architecture of 3rd generation partnership project (3GPP) release <NUM> (R16), the core network has been split into control plane and user plane. <FIG> illustrates the architecture reference model with control and user plane separation (CUPS) for non-roaming and roaming scenarios in evolved packet system (EPC). As shown, the control plane of the EPC may include serving gateway control plane (SGW-C) and packet data network (PDN) gateway control plane (PGW-C). The user plane of the EPC may include SGW user plane (SGW-U) and PGW user plane (PGW-U). <FIG> illustrates an exemplary architecture of 5th generation core (5GC). As shown, the control plane of the 5GC may include session management function (SMF) and the user plane of the 5GC may include user plane function (UPF).

The user plane interacts with the control plane through Sx/N4 interface and reports the corresponding traffic usage to the control plane. Then the control plane collects all the essential information and generates charging data record (CDR) or sends charging information to surround nodes such as charging function (CHF), charging gateway (CG) and online charging system (OCS).

<CIT> discloses a system and methods for session management.

One of the objects of the disclosure is to provide an improved solution for control of packet data connection. In particular, one of the problems to be solved by the disclosure is that when at least part of a packet data connection is deleted, there may be subscriber charging inconsistencies between multiple user plane entities connected in series in the existing solution. The invention is defined in the appended independent claims.

According to the current 3GPP protocol, for the Detach/Deactivation procedures in CUPS, there is Sx modification procedure before Sx termination procedure for the purpose of stop counting and stop forwarding packets. When there is UE/MME/SGSN/HSS-initiated Detach procedure or UE/MME requested PDN disconnection, there is Sx modification message before Sx termination message. The term SGSN refers to serving GPRS support node and the term GPRS refers to general packet radio service. SGW-C will send an Sx Session Modification Request to SGW-U to indicate SGW-U to stop counting for the affected bearer(s). SGW-C shall also indicate the SGW-U to discard downlink packets received from PGW-U for the affected bearer(s), and discard uplink packets received from evolved node B (eNodeB) for the affected bearer(s).

When there is PDN gateway (GW) initiated bearer deactivation or MME initiated Dedicated Bearer Deactivation, PGW-C will send an Sx Session Modification Request to PGW-U to indicate PGW-U to stop counting and stop forwarding both uplink and downlink packets for the affected bearer(s).

For UE/MME/SGSN/HSS-initiated Detach procedure or UE/MME requested PDN disconnection procedure, if SGW-C indicates SGW-U to stop counting and stop forwarding packets for both uplink and downlink, PGW-U can still forward the downlink packets to SGW-U and recording those packets to CDR for charging, which means there will be subscriber charging inconsistencies between PGW-U and SGW-U for downlink packets.

For PDN GW initiated bearer deactivation or MME initiated Dedicated Bearer Deactivation, if PGW-C indicate PGW-U to stop counting and stop forwarding both uplink and downlink packets for the affected bearer(s), SGW-U can still forward uplink packets to PGW-U and recording those packets to CDR. This will cause subscriber charging inconsistencies between PGW-U and SGW-U for uplink packets.

The situation is similar in the 5GC architecture. In 5GC, if there are multiple UPFs associated with a PDU Session, all UPF resources that are used by the PDU Session will be released immediately during PDU Session Release procedure, therefore each UPF drops both uplink and downlink packets simultaneously.

As shown in <FIG>, if UPFs (N3 termination) are released before the UPFs (PSAs) being released, the UPFs (PSAs) can still forward downlink packets and count those packets in charging. However, those packets will be discarded by the UPFs (N3 termination). This will cause the subscriber's downlink charging inconsistencies between multiple UPFs, which turns out overcharging in UPFs (PSAs).

As shown in <FIG>, if UPFs (PSAs) are released before the UPFs (N3 termination) being released, the UPFs (N3 termination) can still forward uplink packets and count those packets in charging. However, those packets will be discarded by the UPFs (PSAs). This will cause the subscriber's uplink charging inconsistencies between multiple UPFs, which turns out overcharging in UPFs (PSAs).

The present disclosure proposes an improved solution for control of packet data connection. The basic idea is that in the Sx modification procedure of EPC, the SGW-C indicates the SGW-U to only stop counting and stop forwarding uplink packets. The PGW-C indicates the PGW-U to only stop counting and stop forwarding downlink packets. In the 5GC, the UPFs (N3 termination) shall drop any remaining uplink packets of the PDU Session before the UPFs (PSAs) being released. The UPFs (PSAs) shall drop any remaining downlink packets of the PDU Session before the UPFs (N3 termination) being released.

As an exemplary example, the solution may be applied to the architectures shown in <FIG>. Details of the architecture of <FIG> can be obtained from 3GPP technical specification (TS) <NUM> V16. <NUM> and details of the architecture of <FIG> can be obtained from 3GPP TS <NUM> V16. Both are incorporated herein by reference in their entirety.

Note that within the context of this disclosure, the term UE or terminal device used herein may also be referred to as, for example, access terminal, mobile station, mobile unit, subscriber station, or the like. It may refer to any (stationary or mobile) end device that can access a wireless communication network and receive services therefrom. By way of example and not limitation, the UE may include a portable computer, an image capture terminal device such as a digital camera, a gaming terminal device, a music storage and playback appliance, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA), an integrated or embedded wireless card, an externally plugged in wireless card, or the like.

In an Internet of things (IoT) scenario, a UE or terminal device may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE or terminal device and/or a network equipment. In this case, the UE or terminal device may be a machine-to-machine (M2M) device, which may, in a 3GPP context, be referred to as a machine-type communication (MTC) device. Particular examples of such machines or devices may include sensors, metering devices such as power meters, industrial machineries, bikes, vehicles, or home or personal appliances, e.g. refrigerators, televisions, personal wearables such as watches, and so on.

As used herein, the term "communication system" refers to a system following any suitable communication standards, such as the first generation (<NUM>), <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> communication protocols, and/or any other protocols either currently known or to be developed in the future. Furthermore, the communications between a terminal device and a network node in the communication system may be performed according to any suitable generation communication protocols, including, but not limited to, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> communication protocols, and/or any other protocols either currently known or to be developed in the future. In addition, the specific terms used herein do not limit the present disclosure only to the communication system related to the specific terms, which however can be more generally applied to other communication systems.

Hereinafter, the solution will be described in detail with reference to <FIG>. <FIG> is a flowchart illustrating a method performed by a user plane entity according to an embodiment of the disclosure. Note that the network entity or function mentioned in this document may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g. on a cloud infrastructure. At block <NUM>, the user plane entity receives, from a control plane entity, a request for modifying parameters related to a packet data connection at least part of which is to be deleted. Upon receipt of the request, the user plane entity stops, at block <NUM>, forwarding and counting of packets in only one of downlink and uplink directions for the at least part of the packet data connection to be deleted. In this way, subscriber charging consistencies can be ensured thereby avoiding overcharging.

For example, the user plane entity and another user plane entity may be associated with the same packet data connection. The only one of downlink and uplink directions may be depending on the relative position between the two user plane entities. If the user plane entity (e.g. SGW-U or N3 termination UPF) is downstream of the another user plane entity (e.g. PGW-U or PSA UPF) and closest to RAN side, the only one of downlink and uplink directions is the uplink direction. On the other hand, if the user plane entity (e.g. PGW-U or PSA UPF) is upstream of the another user plane entity (e.g. SGW-U or N3 termination UPF) and closest to Data Network side, the only one of downlink and uplink directions is the downlink direction.

As a first option, the user plane entity may be an SGW-U and the control plane entity may be an SGW-C. For this option, forwarding and counting of packets in only uplink direction is stopped for the packet data connection (a PDN connection) to be deleted. For example, the request may be received in response to one of: a UE initiated detach procedure; an MME or SGSN initiated detach procedure; an HSS initiated detach procedure; a UE requested PDN disconnection procedure; and an MME requested PDN disconnection procedure.

As a second option, the user plane entity may be a PGW-U and the control plane entity may be a PGW-C. For this option, forwarding and counting of packets in only downlink direction is stopped for one or more bearers to be deleted in the packet data connection (a PDN connection). For example, the request may be received in response to one of: an MME initiated dedicated bearer deactivation procedure; and a PGW initiated bearer deactivation procedure. In the above first and second options, the request may be an Sx Session Modification Request.

As a third option, the user plane entity may be a UPF acting as N3 termination (such as uplink classifier, branching point, intermediate UPF, etc.), and the control plane entity may be an SMF. For this option, forwarding and counting of packets in only uplink direction is stopped for the packet data connection (a PDU session) to be deleted. For example, the request may be received in response to one of: a UE requested PDU session release procedure for non-roaming; a UE requested PDU session release procedure for roaming with local breakout; a UE requested PDU session release procedure for home-routed roaming; a serving network or access network requested PDU session release procedure for non-roaming; a serving network or access network requested PDU session release procedure for roaming with local breakout; and a serving network or access network requested PDU session release procedure for home-routed roaming. In addition, the UPF acting as N3 termination may delete the packet data connection after one or more other UPFs acting as PSAs delete the packet data connection.

As a fourth option, the user plane entity may be a UPF acting as a PSA and the control plane entity is an SMF. For this option, forwarding and counting of packets in only downlink direction is stopped for the packet data connection (a PDU session) to be deleted. For example, the request may be received in response to one of: a PCF or SMF requested PDU session release procedure for non-roaming; a PCF or SMF requested PDU session release procedure for roaming with local breakout; and a PCF or SMF requested PDU session release procedure for home-routed roaming. In addition, the UPF acting as the PSA may delete the packet data connection after one or more UPFs acting as N3 termination delete the packet data connection. In the above third and fourth options, the request may be an N4 Session Modification Request.

Note that in the above examples for implementing blocks <NUM> and <NUM>, the modification request received at block <NUM> may be the same as the existing modification request and the user plane entity may be configured to perform block <NUM> in response to receiving the modification request. Alternatively, it is also possible that the existing modification request is modified to explicitly indicate to stop forwarding and counting of packets in only one of downlink and uplink directions for the at least part of the packet data connection to be deleted.

<FIG> is a flowchart illustrating a method performed by an SMF according to an embodiment of the disclosure. At block <NUM>, in response to a UE or serving network or access network requested PDU session release procedure, the SMF sends, to one or more first UPFs acting as N3 termination, one or more first requests for modifying parameters related to the PDU session to be deleted. For example, the first request may be an N4 Session Modification Request. At block <NUM>, the SMF sends, to one or more second UPFs acting as PSAs, one or more second requests for deleting the PDU session. At block <NUM>, upon the one or more second UPFs have deleted the PDU session, the SMF sends, to the one or more first UPFs, one or more third requests for deleting the PDU session. For example, the second or third request may be an N4 Session Release Request. With the method of <FIG>, subscriber charging consistencies can be ensured thereby avoiding overcharging.

<FIG> is a flowchart illustrating a method performed by an SMF according to an embodiment of the disclosure. At block <NUM>, in response to a PCF or the SMF requested PDU session release procedure, the SMF sends, to one or more first UPFs acting as PSAs, one or more first requests for modifying parameters related to the PDU session to be deleted. For example, the first request may be an N4 Session Modification Request. At block <NUM>, the SMF sends, to one or more second UPFs acting as N3 termination, one or more second requests for deleting the PDU session. At block <NUM>, upon the one or more second UPFs have deleted the PDU session, the SMF sends, to the one or more first UPFs, one or more third requests for deleting the PDU session. For example, the second or third request may be an N4 Session Release Request. With the method of <FIG>, subscriber charging consistencies can be ensured thereby avoiding overcharging.

Based on the above description, one aspect of the disclosure provides a method implemented in a communication system including a control plane entity and a user plane entity. The method may comprise, at the control plane entity, sending, to the user plane entity, a request for modifying parameters related to a packet data connection at least part of which is to be deleted. The method may further comprise, at the user plane entity, receiving, from the control plane entity, the request for modifying parameters related to the packet data connection. The method may further comprise, at the user plane entity, upon receipt of the request, stopping forwarding and counting of packets in only one of downlink and uplink directions for the at least part of the packet data connection to be deleted.

In addition, another aspect of the disclosure provides a communication system comprising a control plane entity and a user plane entity. The control plane entity may be configured to send, to a user plane entity, a request for modifying parameters related to a packet data connection at least part of which is to be deleted. The user plane entity may be configured to: receive, from the control plane entity, the request for modifying parameters related to the packet data connection; and upon receipt of the request, stop forwarding and counting of packets in only one of downlink and uplink directions for the at least part of the packet data connection to be deleted.

<FIG> is a flowchart illustrating an exemplary process in EPC according to an embodiment of the disclosure. At step <NUM>, the UE/MME/SGSN/HSS initiates Detach procedure or UE/MME requests PDN disconnection, in which the SGW-C marks the connection to be deleted. At steps 2a and 2b, the SGW-C indicates the SGW-U to stop counting and stop forwarding uplink packets for the affected bearer(s). At step <NUM>, the SGW-C sends Delete Session Request message to the PGW-C. At steps 4a and 4b, the PGW-C sends an Sx Session Termination Request to the PGW-U to release the Sx session. At step <NUM>, the PGW-C sends Delete Session Response message to the SGW-C. At steps 6a and 6b, the SGW-C sends an Sx Session Termination Request to the SGW-U to release the Sx session.

<FIG> is a flowchart illustrating an exemplary process in EPC according to an embodiment of the disclosure. At step <NUM>, the MME or PDN GW initiates bearer deactivation, in which the PGW-C marks the bearer to be deleted. At steps 2a and 2b, the PGW-C indicates the PGW-U to stop counting and stop forwarding downlink packets for the affected bearer(s). At step <NUM>, the PGW-C sends a Delete Bearer Request message to the SGW-C. At steps 4a and 4b, the SGW-C indicates the SGW-U to stop counting and stop forwarding uplink packets for the affected bearer(s). At steps 5a and 5b, the SGW-C sends a Delete Bearer Request message to the MME. At steps 6a and 6b, the SGW-C indicates the SGW-U to remove the packet detection rule(s) (PDR(s)) for the affected bearer(s). At step <NUM>, the SGW-C sends Delete Bearer Response to the PGW-C. At steps 8a and 8b, the PGW-C indicates the PGW-U to remove the PDR(s) for the affected bearer(s).

<FIG> is a flowchart illustrating an exemplary process in 5GC according to an embodiment of the disclosure. At step <NUM>, the UE or Serving network or (R)AN or AMF requests PDU Session Release for non-roaming and roaming with local breakout. At steps 2a and 2b, the SMF sends an N4 modification request to indicate UPF (N3 termination) to drop any remaining uplink packets of the PDU Session. The symbol "×" in the figure means that any further forwarding of the packets is stopped. At steps 3a-3d, the SMF sends an N4 release request to indicate the UPFs (PSAs) to drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session. At steps 4a and 4b, the SMF send an N4 release request to the remaining UPFs to drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session. At step <NUM>, the remaining PDU Release Procedures are performed.

<FIG> is a flowchart illustrating an exemplary process in 5GC according to an embodiment of the disclosure. At step <NUM>, the PCF/H-SMF requests PDU Session Release Procedures for home-routed roaming. At steps 2a and 2b, the H-SMF sends an N4 modification request to indicate H-UPF (PSA1) to drop any remaining downlink packets of the PDU Session. At step <NUM>, the H-SMF prepares the SM Release PDU Session Command message and initiates the PDU Session Release towards the UE by invoking the Nsmf_PDUSession_Update Request service operation towards the V-SMF. At steps 4a and 4b, the V-SMF sends an N4 modification request to indicate V-UPF (PSA2) to drop any remaining downlink packets of the PDU Session. At steps 5a and 5b, the V-SMF sends an N4 release request to indicate the UPF (N3 termination) to drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session. At steps 6a and 6b, the V-SMF sends an N4 release request to the remaining UPFs to drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session. At step <NUM>, the N1/N2 Resource Release is performed. At step <NUM>, the V-SMF responds to the Nsmf_PDUSession_Update Request invoked at step <NUM> and confirms the PDU Session Release. At steps 9a and 9b, the H-SMF send an N4 release request to the remaining UPFs to drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session. At step <NUM>, the remaining PDU Release Procedures are performed.

Based on the above description, the following changes are proposed to be made to 3GPP TS <NUM><NUM>. <NUM>, where the changes are highlighted with underlines.

In addition, the following first change is proposed to be made to 3GPP TS <NUM> V16. <NUM>, where <FIG> is Figure <NUM>. <NUM>-<NUM> after the first change and the following text is the text after the first change.

This procedure is used in the case of non-roaming and roaming with local breakout scenarios.

Figure <NUM>. <NUM>-<NUM> captures UE, Serving network or (R)AN Requested PDU Session Release procedure. The procedure allows the UE, the Serving network or the (R)AN to initiate the release of a PDU.

Figure <NUM>. <NUM>-<NUM> captures PCF or SMF requested PDU Session Release procedure. The procedure allows the PCF or the SMF to initiate the release of a PDU Session. In the case of LBO, the procedure is as in the case of non-roaming with the difference that the AMF, the SMF, the UPF and the PCF are located in the visited network.

This clause defines PDU Session Release for Non-Roaming and Roaming with Local Breakout during the following procedures:.

Figure <NUM>. <NUM>-<NUM>: UE, Serving network or (R)AN requested PDU Session Release for non-roaming and roaming with local breakout.

If the UPF included APN Rate Control Status and/or Small Data Rate Control Status in step <NUM> then the SMF includes APN Rate Control and/or Small Data Rate Control Status and the AMF stores the Small Data Rate Control Status and/or the APN Rate Control Status in the UE context in AMF.

The AMF and SMF shall remove all contexts (including the PDU Session ID) associated with the PDU Session which are indicated as released at the UE. The SMF shall remove any event subscriptions on the AMF by the SMF that becomes no more needed due to the PDU Session Release. The steps <NUM> to <NUM> are skipped.

If the message received from the SMF in step <NUM> does not include N2 SM Resource Release request, the AMF transmits the NAS message (PDU Session ID, N1 SM container) to the UE and the steps <NUM>, <NUM> are skipped.

If the PDU Session is Control Plane CIoT 5GS Optimisation enabled, the SMF shall not include N2 SM Resource Release request in the message sent to the AMF, the AMF transmits the NAS message (PDU Session ID, N1 SM container) to the UE and the steps <NUM>, <NUM> are skipped.

If the UE is in CM-CONNECTED state and the received message from the SMF in step <NUM> includes N2 SM Resource Release request, the AMF transfers the SM information received from the SMF in step <NUM> (N2 SM Resource Release request, N1 SM container) to the (R)AN.

If the message from the SMF includes Small Data Rate Control Status then the AMF stores it in the UE Context in AMF.

The SMF invokes Nsmf_PDUSession_SMContextStatusNotify to notify AMF that the SM context for this PDU Session is released. If the UPF included Small Data Rate Control Status and/or APN Rate Control Status in step <NUM> then the SMF includes Small Data Rate Control Status and/or APN Rate Control Status in its request to the AMF in this step. The AMF releases the association between the SMF ID and the PDU Session ID, DNN, as well as S-NSSAI and stores the Small Data Rate Control Status and/or the APN Rate Control Status in the UE context in AMF. The SMF shall remove any event subscriptions on the AMF that becomes no more needed due to the PDU Session Release.

NOTE <NUM>: The UE and the 5GC will get synchronized about the status of the (released) PDU Session at the next Service Request or Registration procedure.

The following second change is proposed to be made to 3GPP TS <NUM> V16. <NUM>, where <FIG> is Figure <NUM>. <NUM>-<NUM> after the second change and the following text is the text after the second change.

Figure <NUM>. <NUM>-<NUM>: PCF or SMF requested PDU Session Release for non-roaming and roaming with local breakout.

The SMF creates an N1 SM including PDU Session Release Command message (PDU Session ID, Cause). The Cause may indicate a trigger to establish a new PDU Session with the same characteristics (e.g. when procedures related with SSC mode <NUM> are invoked).

If the User Plane connection of the PDU Session is activated, the message sent by the SMF to the AMF shall include N2 SM Resource Release request (PDU Session ID) in the Namf_Communication_N1N2MessageTransfer, to release the (R)AN resources associated with the PDU Session. If the User Plane connection of the PDU Session is not activated, the message sent by the SMF to the AMF shall not include N2 SM Resource Release request. NOTE <NUM>: SSC modes are defined in TS <NUM> [<NUM>] clause <NUM>.

The SMF invokes the Namf_Communication_N1N2MessageTransfer service operation (N1 SM container (PDU Session Release Command), skip indicator).

The "skip indicator" tells the AMF whether it may skip sending the N1 SM container to the UE (e.g. when the UE is in CM-IDLE state). SMF includes the "skip indicator" in the Namf_Communication_N1N2MessageTransfer except when the procedure is triggered to change PDU Session Anchor of a PDU Session with SSC mode <NUM>.

If the UE is in CM-IDLE state and "skip indicator" is included in the Namf_Communication_N1N2MessageTransfer service operation, the AMF acknowledges this step by sending an Namf_Communication_N1N2MessageTransfer Response message ("N1 SM.

Message Not Transferred") to SMF and steps <NUM> to <NUM> are skipped.

The SMF waits until it has received replies to the N1 and N2 information provided in step <NUM>, as needed.

The SMF invokes Nsmf_PDUSession_ SMContextStatusNotify to notify AMF that the SM context for this PDU Session is released. If the UPF included Small Data Rate Control Status and/or APN Rate Control Status in step <NUM> then the SMF includes Small Data Rate Control Status and/or APN Rate Control Status in its request to the AMF in this step. The AMF releases the association between the SMF ID and the PDU Session ID, DNN, as well as S-NSSAI and stores the Small Data Rate Control Status and/or the APN Rate Control Status in the UE context in AMF. The SMF shall remove any event subscriptions on the AMF that becomes no more needed due to the PDU Session Release. NOTE <NUM>: The UE and the 5GC will get synchronized about the status of the (released) PDU Session at the next Service Request or Registration procedure.

(PDU Session Release initiated by the SMF) If Dynamic PCC applied to this session the SMF invokes an SM Policy Association Termination procedure as defined in clause <NUM>. <NUM> to delete the PDU Session.

The following third change is proposed to be made to 3GPP TS <NUM> V16. <NUM>, where <FIG> is Figure <NUM>. <NUM>-<NUM> after the third change and the following text is the text after the third change.

This procedure is used in the case of home-routed roaming scenarios.

This clause defines PDU Session Release for Home-routed Roaming during the following procedures:.

Figure <NUM>. <NUM>-<NUM>: UE, Serving network or (R)AN requested PDU Session Release for home-routed roaming.

The following fourth change is proposed to be made to 3GPP TS <NUM> V16. <NUM>, where <FIG> is Figure <NUM>. <NUM>-<NUM> after the fourth change and the following text is the text after the fourth change.

<FIG> is a block diagram showing an apparatus suitable for use in practicing some embodiments of the disclosure. For example, any one of the user plane entity and the SMF described above may be implemented through the apparatus <NUM>. As shown, the apparatus <NUM> may include a processor <NUM>, a memory <NUM> that stores a program, and optionally a communication interface <NUM> for communicating data with other external devices through wired and/or wireless communication.

The memory <NUM> may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memories, magnetic memory devices and systems, optical memory devices and systems, fixed memories and removable memories. The processor <NUM> may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non-limiting examples.

<FIG> is a block diagram showing an apparatus implementing a user plane entity according to an embodiment of the disclosure. As shown, the apparatus <NUM> comprises a reception module <NUM> and a control module <NUM>. The reception module <NUM> may be configured to receive, from a control plane entity, a request for modifying parameters related to a packet data connection at least part of which is to be deleted, as described above with respect to block <NUM>. The control module may be configured to, upon receipt of the request, stop forwarding and counting of packets in only one of downlink and uplink directions for the at least part of the packet data connection to be deleted, as described above with respect to block <NUM>.

<FIG> is a block diagram showing an apparatus implementing an SMF according to an embodiment of the disclosure. As shown, the apparatus <NUM> comprises a modification module <NUM>, a first deletion module <NUM> and a second deletion module <NUM>. The modification module <NUM> may be configured to, in response to a UE or serving network or access network requested PDU session release procedure, send, to one or more first UPFs acting as N3 termination, one or more first requests for modifying parameters related to the PDU session to be deleted, as described above with respect to block <NUM>. The first deletion module <NUM> may be configured to send, to one or more second UPFs acting as PSAs, one or more second requests for deleting the PDU session, as described above with respect to block <NUM>. The second deletion module <NUM> may be configured to, upon the one or more second UPFs have deleted the PDU session, send, to the one or more first UPFs, one or more third requests for deleting the PDU session, as described above with respect to block <NUM>.

<FIG> is a block diagram showing an apparatus implementing an SMF according to an embodiment of the disclosure. As shown, the apparatus <NUM> comprises a modification module <NUM>, a first deletion module <NUM> and a second deletion module <NUM>. The modification module <NUM> may be configured to, in response to a PCF or the SMF requested PDU session release procedure, send, to one or more first UPFs acting as PSAs, one or more first requests for modifying parameters related to the PDU session to be deleted, as described above with respect to block <NUM>. The first deletion module <NUM> may be configured to send, to one or more second UPFs acting as N3 termination, one or more second requests for deleting the PDU session, as described above with respect to block <NUM>. The second deletion module may be configured to, upon the one or more second UPFs have deleted the PDU session, send, to the one or more first UPFs, one or more third requests for deleting the PDU session, as described above with respect to block <NUM>. The modules described above may be implemented by hardware, or software, or a combination of both.

It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, RAM, etc. As will be appreciated by one skilled in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like.

References in the present disclosure to "one embodiment", "an embodiment" and so on, indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It should be noted that two blocks shown in succession in the figures may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. It will be further understood that the terms "comprises", "comprising", "has", "having", "includes" and/or "including", when used herein, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components and/ or combinations thereof. The terms "connect", "connects", "connecting" and/or "connected" used herein cover the direct and/or indirect connection between two elements.

Claim 1:
A method performed by a user plane entity being a User Plane Function, UPF, the method comprising:
receiving (<NUM>, 2a), from a control plane entity being a Session Management Function, SMF, and as part of a protocol data unit, PDU, session release procedure for home routed roaming , a request for modifying parameters related to a PDU session at least part of which is to be deleted, wherein the request is a N4 Session Modification Request,
wherein when the SMF is a Home SMF, H-SMF, and the UPF is a Home UPF, H-UPF, then the N4 Session Modification Request indicates that the H-UPF stops forwarding traffic and also stops taking into account the traffic for usage monitoring in downlink direction, or
wherein when the SMF is a Visited SMF, V-SMF, and the UPF is a Visited UPF, V-UPF, then the N4 Session Modification Request indicates that the V-UPF stops forwarding traffic and also stops taking into account the traffic for usage monitoring in uplink direction;
sending (2b) a N4 Session Modification Response to the control plane entity;
upon receipt of the request, stopping (<NUM>) forwarding traffic and also stopping taking into account the traffic for usage monitoring in only one of downlink and uplink directions for the at least part of the PDU session to be deleted;
receiving, from the control plane entity, a N4 Session Release Request message to drop any remaining packets of the PDU Session and release all tunnel resources and contexts associated with the N4 Session; and
sending, to the control plane entity, a N4 Session Release Response message in response to the N4 Session Release Request message.