Network nodes and methods therein for enhanced connection restoration, computer-readable storage medium and computer program product

Abstract

The present disclosure provides a method (200) in a first network function for mobility management. The method (200) includes: participating (210) in restoration of at least one Packet Data Network, PDN, connection including a first PDN connection associated with a User Equipment, UE; receiving (220), before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management; and transmitting (230), to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored.

Description

[0001] Applicant’s Ref: Pl 11865WO02

[0002] NETWORK NODESAND METHODS THEREIN FOR ENHANCED CONNECTION RESTORATION

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to communication technology, and more particularly, to network nodes and methods therein for enhanced connection restoration.

[0005] BACKGROUND

[0006] The 3rdGeneration Partnership Project (3GPP) Technical Specification (TS) 23.007, V18.5.0, which is incorporated herein by reference in its entirety, specifies Packet Data Network (PDN) connection restoration procedures, including Mobility Management Entity (MME) triggered PDN connection restoration and PDN Gateway (PGW) triggered PDN connection restoration.

[0007] Figure 1A

[0008] Fig. 1 A shows a procedure of MME triggered PDN connection restoration. An MME may trigger a PDN connection restoration to move a PDN connection to a different PDN Gateway Control plane (PGW-C) I Session Management Function (SMF) (referred to as PGW-C / SMF, SMF+PGW-C, or combined PGW-C and SMF) in the same PGW- C / SMF Set, e.g., when detecting that the PGW-C / SMF currently serving the PDN connection is not reachable. The MME may trigger this procedure for a specific PDN connection, e.g., upon receiving a Modify Bearer Response message for this PDN connection with the cause code set to "Remote peer not responding", or for all PDN connections served by a PGW-C / SMF, e.g., when receiving a PGW Restart Notification from the SGW with the cause "PGW not responding" or when the MME determines that the PGW-C / SMF has failed. As shown in Fig. 1 A, the procedure may include the following steps.

[0009] Step 1 . The PGW-C / SMF fails without restart from the PGW-C / SMF set.

[0010] Steps 2a-2b. The MME sends a Modify Bearer Request message to the SGW, e.g., to report a User Location Information change, the Serving Gateway (SGW) shall respond with the Modify Bearer Response message with the cause code set to "Remote peer not responding" when the SGW detects that the PGW-C / SMF is not responding.

[0011] Step 2c. When detecting that the PGW-C / SMF has failed, the SGW-C shall send a PGW Restart Notification to the MME. When detecting that a PGW-C / SMF has failed, the SGW-C and MME shall maintain the contexts of the PDN connections served by that PGW-C / SMF for which this procedure is supported. Applicant’s Ref: Pl 11865WO02

[0012] Step 3. The MME should select an alternative PGW-C / SMF using the PGW Change Info received earlier from the PGW-C / SMF for the PDN connection (for the scenario described as step 2a-2b) or for all PDN connections associated with the failed PGW (for the scenario described as step 2c).

[0013] Step 4. The MME shall send a Create Session Request including a PGW Change Indication and without setting the Operation Indication to "1" towards the newly selected PGW-C / SMF, via the same or a different SGW. The MME may defer doing so until it needs to send signalling to the SGW or PGW-C. The MME should reuse the same SGW if possible, since the PDN connection restoration remains then transparent to the eNodeB. The PGW Change Indication tells the SGW and PGW-C / SMF that this is a request to move an existing PDN connection to the new PGW-C / SMF.

[0014] Step 5. The new PGW-C / SMF shall identify the PDN connection context using the User Equipment (UE) 's identity and the Linked EPS Bearer Identity received in the Create Session Request. If it can take over the PDN connection, it shall return a Create Session Response towards the SGW and MME, including (among others) the new S5 / S8 PGW Fully Qualified Tunnel Endpoint Identifier (F-TEID) for control plane, its PGW node name, the S5 / S8-U PGW F- TEID for the default bearer and S5 / S8 PGW F-TEIDs for dedicated bearers (if any). The SGW and MME shall update their PDN connection context with the information received from the PGW-C / SMF. If the MME reselected a different SGW, the MME shall update the eNB with the new SGW's S1-U F-TEID using the MME triggered Serving GW relocation procedure.

[0015] Step 6. The MME shall update the PGW identity in the Home Subscriber Server (HSS).

[0016] Step 7. The HSS shall respond the Notify Request.

[0017] Figure IB

[0018] Fig. 1B shows a procedure of PGW triggered PDN connection restoration. A PGW-C / SMF currently supporting a PDN connection, or a new PGW-C / SMF from the same PGW-C / SMF set, may trigger a PDN connection restoration to move the PDN connection to a different PGW-C / SMF. This may happen e.g. when a PGW-C / SMF is deinstantiated (scale-in operation), or when a new PGW-C / SMF from the same PGW-C / SMF set is reselected for the PDN connection upon a request from the Policy Control Function (PCF) or the PGW - User Plane (PGW-U) I User Plane Function (UPF) and, more generally, when the PGW-C / SMF supporting a PDN connection is no longer available and a new PGW-C / SMF of the same PGW-C / SMF set needs to send signalling to the SGW or MME, before the MME has triggered a PDN connection restoration. As shown in Fig. 1 B, the procedure may include the following steps. Applicant’s Ref: Pl 11865WO02

[0019] Step 1 . The PGW-C / SMF currently supporting the PDN connection or another PGW-C / SMF from the same PGW- C / SMF set determines that the PDN connection needs to be moved to a different PGW-C / SMF, e.g. during a PGW- C / SMF set scale-in operation, or e.g. due to PCF or PGW-U / UPF reselecting an alternative PGW-C / SMF from the same PGW-C / SMF set due to the PGW-C / SMF serving the PDN connection being unavailable and this triggers bearer signalling towards the MME.

[0020] Step 2 or 3. The PGW-C / SMF currently supporting the PDN connection or the new PGW-C / SMF taking over the PDN connection may send an Update Bearer Request for the default bearer towards the SGW immediately or send Create Bearer Request (or a Update Bearer Request or a Delete Bearer Request) when the PGW-C / SMF needs to send this signalling towards the SGW and MME, including the PGW Change Info Information Element (IE). The SGW shall relay transparently the PGW Change Info IE towards the MME. The PGW Change Info IE shall contain the new S5 / S8 PGW Internet Protocol (IP) address for control plane. The PGW-C / SMF may also include the Sender F-TEID for Control Plane IE containing a new S5 / S8 PGW F-TEID for control plane. The Create / Update / Delete Bearer Response message shall be sent over S5 / S8 using the S5 / S8 PGW TEID for control plane received in the Sender F-TEID for Control Plane IE, if any, otherwise using the S5 / S8 PGW TEID for control plane earlier assigned to the PDN connection.

[0021] Step 4. Same as step 4 of Fig. 1 A, with the MME including in the Create Session Request the new S5 / S8 PGW- C / SMF IP address received in the PGW Change Info.

[0022] Steps 5-7. Same as steps 5-7 of Fig. 1 A.

[0023] SUMMARY

[0024] During the PGW triggered PDN connections restoration procedure, the MME may be requested to move a number of PDN connections associated with the PGW-C / SMF Fully Qualified PDN Connection Set Identifier(s) (FQ-CSID(s)), group ld(s) or PGW Control Plane IP Address(es) to another PGW.

[0025] It takes time to restore a large number of PDN connections in the serving MME. During such restoration procedure, affected UEs may move so that an inter-MME mobility may take place. In such case, the PDN connection restoration for that UE / PDN connection may be suspended in the source MME (the current serving MME) and the mobility procedure may be prioritized. That is, the source MME may include an MME / SGSN (Serving GPRS Support Node) / AMF (Access and Mobility Management Function) UE EPS (Evolved Packet System) PDN Connections IE that is still associated with the original PGW-C / SMF. The target MME / AMF may experience a failure when communicating with the original PGW-C / SMF (if it has failed) or the original PGW-C / SMF is NOT expected to receive Applicant’s Ref: Pl 11865WO02 any PDN connection modification for this PDN connection (since it has determined to move the PDN connection to another PGW-C / SMF).

[0026] Similarly, in the MME triggered PDN restoration procedure triggered by a PGW Restart Notification with the cause "PGW not responding” from the SGW, the MME will identify all affected PDNs which are associated with the failed PGW-C / SMF and perform the restoration procedure for all these PDN connections. During the restoration procedures, the affected UEs may perform inter-MME mobility procedures, and the target MME may fail to contact the original PGW-C / SMF for the same reason as described above.

[0027] Even when the restoration of PDN connection is for a single UE only, in a PGW or MME triggered PDN restoration procedure, the source MME may have sent out a Create Session Request to the new PGW, and then an inter-MME mobility may happen while the MME is waiting for the response message. In this case, the source MME still keeps the PDN as served by the original PGW-C, which will lead to the same problem as described above.

[0028] It is an object of the present disclosure to provide network nodes and methods therein, capable of solving the above problem.

[0029] According to a first aspect of the present disclosure, a method in a first network function for mobility management is provided. The method includes participating in restoration of at least one PDN connection including a first a PDN connection associated with a UE. The method further includes receiving, before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management. The method further includes transmitting, to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored.

[0030] In an embodiment, the second message may further include a second indication of an IP address or a node name of a combined PGW-C and SMF, towards which the first PDN connection is to be restored.

[0031] In an embodiment, the mobility event may include Tracking Area Update (TAU), and the second message may include a Context Response.

[0032] In an embodiment, the mobility event may include handover and the second message may include a Forward Relocation Request. Applicant’s Ref: Pl 11865WO02

[0033] In an embodiment, the first indication may be included in the second message when the restoration of the at least one PDN connection has been initiated but the restoration of the first PDN connection has not started yet, or when the restoration of the first PDN connection has started but is interrupted due to the mobility event.

[0034] In an embodiment, the second indication may be included in the second message when the combined PGW-C and SMF has been determined, or when the first network function for mobility management has transmitted a request for restoration of the first PDN connection to the combined PGW-C and SMF but has not received a response from the combined PGW-C and SMF.

[0035] In an embodiment, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMF.

[0036] According to a second aspect of the present disclosure, a method in a second network function for mobility management is provided. The method includes receiving, from a first network function for mobility management, a message including a first indication that a PDN connection is to be restored. The method further includes participating in restoration of the PDN connection based on the indication.

[0037] In an embodiment, the message may further include a second indication of an IP address or a node name of a combined PGW-C and SMF, towards which the PDN connection is to be restored.

[0038] In an embodiment, the operation of participating in restoration of the PDN connection may include restoring the PDN connection towards the combined PGW-C and SMF using the IP address or node name.

[0039] In an embodiment, the message may be a Context Response or a Forward Relocation Request.

[0040] In an embodiment, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMF.

[0041] According to a third aspect of the present disclosure, a network node is provided. The network node includes a communication interface, a processor, and a memory. The memory contains instructions executable by the processor whereby the network node is operative to, when implementing a first network function for mobility management, perform the method according to the above first aspect, or when implementing a second network function for mobility management, perform the method according to the above second aspect. Applicant’s Ref: Pl 11865WO02

[0042] According to a fourth aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer-readable instructions stored thereon. The computer-readable instructions, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to the above first aspect, or when implementing a second network function for mobility management, perform the method according to the above second aspect.

[0043] According to a fifth aspect of the present disclosure, a computer program product is provided. The computer program product includes computer-readable instructions which, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to the above first aspect, or when implementing a second network function for mobility management, perform the method according to the above second aspect.

[0044] With certain embodiments of the present disclosure, when a mobility event occurs before pending restoration of a PDN connection is completed, an indication that the PDN connection is to be restored can be transmitted from a first network function for mobility management to a second network function for mobility management, such that the second network function for mobility management can restore the PDN connection towards a new combined PGW-C and SMF, instead of communicating with the old one which may have failed. In this way, unnecessary signaling towards the old combined PGW-C and SMF can be avoided, which would otherwise lead to increased latency in the mobility procedure.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages will be more apparent from the following description of embodiments with reference to the figures, in which:

[0047] Figs. 1 A and 1 B are schematic diagrams each showing a procedure of PDN connection restoration;

[0048] Fig. 2 is a flowchart illustrating a method in a first network function for mobility management according to an embodiment of the present disclosure;

[0049] Fig. 3 is a flowchart illustrating a method in a second network function for mobility management according to an embodiment of the present disclosure;

[0050] Fig. 4 is a schematic diagram showing a procedure of PDN connection restoration according to an embodiment of the present disclosure;

[0051] Fig. 5 is a schematic diagram showing a procedure of PDN connection restoration according to another embodiment of the present disclosure; and

[0052] Fig. 6 is a block diagram of a network node according to an embodiment of the present disclosure. Applicant’s Ref: Pl 11865WO02

[0053] DETAILED DESCRIPTION

[0054] In the present disclosure, a network function, or NF, can 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. The term "network node” refers to any physical or virtual node configured to implement a network function.

[0055] References in the specification to "one embodiment," "an embodiment," "an example embodiment," and the like 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. Moreover, such phrases are not necessarily referring to the same embodiment. 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 affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0056] It shall be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. 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 etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0058] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0059] Figure 2

[0060] Fig. 2 is a flowchart illustrating a method 200 according to an embodiment of the present disclosure. The method 200 can be performed by a first network function for mobility management, e.g., an MME. Applicant’s Ref: Pl 11865WO02

[0061] At block 210, the first network function for mobility management participates in restoration of at least one PDN connection including a first PDN connection associated with a UE. Here, the restoration may be MME triggered (as shown in Fig. 1A) or PGW triggered (as shown in Fig. 1 B). Moreover, the restoration may be for a plurality of PDN connections, e.g., associated with a PGW-C / SMF, or the restoration may be for a single UE only.

[0062] At block 220, the first network function for mobility management receives, before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management. Here, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMF in the mobility event.

[0063] In an example, the mobility event may be TAU, and the first message may be a Context Request.

[0064] In another example, the mobility event may be handover, and the first message may be a Handover Required message.

[0065] At block 230, the first network function for mobility management transmits, to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored. Here, the second message may be a Context Response, e.g., in the mobility event of TAU, or a Forward Relocation Request, e.g., in the mobility event of handover.

[0066] In an example, the first indication may be included in the second message when the restoration of the at least one PDN connection has been initiated but the restoration of the first PDN has not started yet, or when the restoration of the first PDN connection has started but is interrupted due to the mobility event.

[0067] In an example, the second message may further include a second indication of an IP address or a node name (e.g., Fully Qualified Domain Name (FQDN)) of a combined PGW-C and SMF, towards which the first PDN connection is to be restored. For example, the second indication may be included in the second message when the combined PGW- C and SMF has been determined, or when the first network function for mobility management has transmitted a request for restoration of the first PDN connection to the combined PGW-C and SMF but has not received a response from the combined PGW-C and SMF.

[0068] In an example, the first indication may be a Pending PDN Restoration Indication Flag, and / or the second indication may be a New PGW-C / SMF IP Address Information Element (IE) and / or a New PGW Node Name IE, as shown in Table 1 and Table 2 below. Applicant’s Ref: Pl 11865WO02

[0069] Table 1 : MME / SGSN / AMF UE EPS PDN Connections within Forward Relocation Request

[0070] Table 2: MME / SGSN / AMF UE EPS PDN Connections within Context Response Applicant’s Ref: Pl 11865WO02

[0071] For other details of the Forward Relocation Request and Context Response, reference can be made to the 3GPP TS 29.274, VI 8.7.0, which is incorporated herein by reference in its entirety.

[0072] Figure 3

[0073] Fig. 3 is a flowchart illustrating a method 300 according to an embodiment of the present disclosure. The method 300 can be performed by a second network function for mobility management, e.g., an MME or AMR

[0074] At block 310, the second network function for mobility management receives, from a first network function for mobility management, a message including a first indication that a PDN connection is to be restored. Here, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMF in a mobility event (e.g., TAU or handover of a UE).

[0075] In an example, the message may be a Context Response, e.g., in a mobility event of TAU, or a Forward Relocation Request, e.g., in a mobility event of handover.

[0076] At block 320, the second network function for mobility management participates in restoration of the PDN connection based on the indication.

[0077] In an example, the message may further include a second indication of an IP address or a node name (FQDN) of a combined PGW-C and SMF, towards which the PDN connection is to be restored. Accordingly, in the block 320, the second network function for mobility management may restore the PDN connection towards the combined PGW-C and SMF using the IP address or node name.

[0078] In an example, the first indication may be a Pending PDN Restoration Indication Flag, and / or the second indication may be a New PGW-C / SMF IP Address Information Element (IE) and / or a New PGW Node Name IE, referring to Table 1 and Table 2 above.

[0079] The methods 200 and 300 will be further explained with reference to Figs. 4 and 5 below.

[0080] Figure 4

[0081] Fig. 4 shows a procedure of PDN connection restoration according to an embodiment of the present disclosure. As shown, the procedure includes the following steps.

[0082] Step 1. If PGW triggered PDN connection restoration in an old (source) MME has started after the old (source) MME received a Create / Update / Delete Bearer Request message with PGW Change Info where it is requested to move, Applicant’s Ref: Pl 11865WO02 i.e. , to reestablish, one or more PDN connections in an alternative (new) PGW-C / SMF which impacts one or more devices having those affected PDN connections, a PDN connection (as part of the PDN connections to be reestablished) is pending to start the restoration. Alternatively, if the old MME receives a PGW Restart Notification with the cause "PGW Not Responding”, the old MME starts a PDN connection restoration procedure for those PDN connections associated with the failed PGW-C / SMF, a PDN connection (as part of the PDN connections to be reestablished) is pending to start the restoration.

[0083] Step 2a. If a UE has TAU to a new (target) MME / AMF before the restoration of the PDN connection to which the UE pertains is started, the old MME marks the PDN connection as "to be restored”.

[0084] Step 2b. The old MME receives a Context Request from the new MME / AMF.

[0085] Step 2c. The old MME sends a Context Response to the new MME / AMF, including a "Pending PDN Connection Restoration Indication” flag set to 1 and optionally a new IP address or node name of a new PGW-C / SMF, for the PDN connection marked as "to be restored”.

[0086] Steps 3a and 3b are alternatives to Steps 2a-2c.

[0087] Step 3a. If a Handover is initiated to a new (target) MME / AMF before the restoration of the PDN connection is started, the old MME receives a Handover Required message from the evolved NodeB (eNB).

[0088] Step 3b. The old MME sends a Forward Relocation Request to the new MME / AMF, including a "Pending PDN Connection Restoration Indication” flag set to 1 and optionally a new IP address or node name (e.g., FQDN) of a new PGW-C / SMF, for the PDN connection marked as "to be restored”.

[0089] Step 4. The new MME / AMF starts PDN connection restoration procedure for the PDN connection in response to the "Pending PDN Connection Restoration Indication” flag set to 1 . If the new IP address or node name is provided, the new MME / AMF then restores the PDN connection using the new IP address / node name towards the new PGW- C / SMF. Otherwise, the new MME / AMF can select a new PGW-C / SMF based on PGW Change Info.

[0090] Step 5. The TAU or handover procedure continues. Applicant’s Ref: Pl 11865WO02

[0091] Figure 5

[0092] Fig. 5 shows a procedure of PDN connection restoration according to another embodiment of the present disclosure.

[0093] As shown, the procedure includes the following steps.

[0094] Step 1 . An old MME sends a Create Session Request to a new PGW-C / SMF for PDN Restoration, and is waiting for a Create Session Response.

[0095] Step 2a. If a UE has TAU to a new (target) MME / AMF while the old MME is still waiting for the Create Session Response, the old MME marks the PDN connection as "to be restored”.

[0096] Step 2b. The old MME receives a Context Request from the new MME / AMF.

[0097] Step 2c. The old MME sends a Context Response to the new MME / AMF, including a "Pending PDN Connection Restoration Indication” flag set to 1 and optionally a new IP address or node name of a new PGW-C / SMF, for the PDN connection marked as "to be restored”.

[0098] Steps 3a and 3b are alternatives to Steps 2a-2c.

[0099] Step 3a. If a Handover is initiated to a new (target) MME / AMF while the old MME is still waiting for the Create Session Response, the old MME receives a Handover Required message from the evolved NodeB (eNB).

[0100] Step 3b. The old MME sends a Forward Relocation Request to the new MME / AMF, including a "Pending PDN Connection Restoration Indication” flag set to 1 and optionally a new IP address or node name (e.g., FQDN) of a new PGW-C / SMF, for the PDN connection marked as "to be restored”.

[0101] Step 4. The new MME / AMF starts PDN connection restoration procedure for the PDN connection in response to the "Pending PDN Connection Restoration Indication” flag set to 1 . If the new IP address or node name is provided, the new MME / AMF then restores the PDN connection using the new IP address / node name towards the new PGW- C / SMF. Otherwise, the new MME / AMF can select a new PGW-C / SMF based on PGW Change Info.

[0102] Step 5. The TAU or handover procedure continues.

[0103] Figure 6

[0104] Fig. 6 is a block diagram of a network node 600 according to an embodiment of the present disclosure. Applicant’s Ref: Pl 11865WO02

[0105] The network node 600 includes a communication interface 610, a processor 620 and a memory 630.

[0106] The memory 630 may contain instructions executable by the processor 620 whereby the network node 600 is operative to, when implementing a first network function for mobility management, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 2. Particularly, the memory 630 may contain instructions executable by the processor 620 whereby the network node 600 is operative to, when implementing a first network function for mobility management: participate in restoration of at least one PDN connection including a first PDN connection associated with a UE; receive, before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management; and transmit, to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored.

[0107] In an embodiment, the second message may further include a second indication of an IP address or a node name of a combined PGW-C and SMF, towards which the first PDN connection is to be restored.

[0108] In an embodiment, the mobility event may include Tracking Area Update (TAU), and the second message may include a Context Response.

[0109] In an embodiment, the mobility event may include handover and the second message may include a Forward Relocation Request.

[0110] In an embodiment, the first indication may be included in the second message when the restoration of the at least one PDN connection has been initiated but the restoration of the first PDN connection has not started yet, or when the restoration of the first PDN connection has started but is interrupted due to the mobility event.

[0111] In an embodiment, the second indication may be included in the second message when the combined PGW-C and SMF has been determined, or when the first network function for mobility management has transmitted a request for restoration of the first PDN connection to the combined PGW-C and SMF but has not received a response from the combined PGW-C and SMF.

[0112] In an embodiment, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMR

[0113] Alternatively, the memory 630 may contain instructions executable by the processor 620 whereby the network node 600 is operative to, when implementing a second network function for mobility management, perform the actions, Applicant’s Ref: Pl 11865WO02 e.g., of the procedure described earlier in conjunction with Fig. 3. Particularly, the memory 630 may contain instructions executable by the processor 620 whereby the network node 600 is operative to, when implementing a second network function for mobility management: receive, from a first network function for mobility management, a message including a first indication that a PDN connection is to be restored. The method further includes participating in restoration of the PDN connection based on the indication.

[0114] In an embodiment, the message may further include a second indication of an IP address or a node name of a combined PGW-C and SMF, towards which the PDN connection is to be restored.

[0115] In an embodiment, the operation of participating in restoration of the PDN connection may include restoring the PDN connection towards the combined PGW-C and SMF using the IP address or node name.

[0116] In an embodiment, the message may be a Context Response or a Forward Relocation Request.

[0117] In an embodiment, the first network function for mobility management may be an old or source MME, and the second network function for mobility management may be a new or target MME or AMR

[0118] The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, e.g., a non-transitory computer readable storage medium, an Electrically Erasable Programmable Read- Only Memory (EEPROM), a flash memory and a hard drive. The computer program product includes a computer program. The computer program includes: code / computer readable instructions, which when executed by the processor 620 causes the network node 600 to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 2 or 3.

[0119] The computer program product may be configured as a computer program code structured in computer program modules. The computer program modules could essentially perform the actions of the flow illustrated in Fig. 2 or 3.

[0120] The processor may be a single CPU (Central Processing Unit), but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and / or related chips sets and / or special purpose microprocessors such as Application Specific Integrated Circuits (ASICs). The processor may also comprise board memory for caching purposes. The computer program may be carried in a computer program product connected to the processor. The computer program product may comprise a non- transitory computer readable storage medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random Access Memory (RAM), a Read-Only Memory (ROM), or an Applicant’s Ref: Pl 11865WO02

[0121] EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories.

[0122] The disclosure has been described above with reference to embodiments thereof. It should be understood that various modifications, alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the disclosure. Therefore, the scope of the disclosure is not limited to the above particular embodiments but only defined by the claims as attached.

[0123] Summary of Some Embodiments

[0124] Some of the embodiments that have been described above may be summarized in the following manner:

[0125] 1. A method (200) in a first network function for mobility management, comprising: participating (210) in restoration of at least one Packet Data Network, PDN, connection including a first PDN connection associated with a User Equipment, UE; receiving (220), before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management; and transmitting (230), to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored.

[0126] 2. The method (200) of embodiment 1 , wherein the second message further includes a second indication of an Internet Protocol, IP, address or a node name of a combined PDN Gateway Control plane, PGW-C, and Session Management Function, SMF, towards which the first PDN connection is to be restored.

[0127] 3. The method (200) of embodiment 1 or 2, wherein the mobility event comprises Tracking Area Update, TAU, and the second message comprises a Context Response.

[0128] 4. The method (200) of embodiment 1 or 2, wherein the mobility event comprises handover and the second message comprises a Forward Relocation Request.

[0129] 5. The method (200) of any of embodiment 1-4, wherein the first indication is included in the second message when the restoration of the at least one PDN connection has been initiated but the restoration of the first PDN connection has not started yet, or when the restoration of the first PDN connection has started but is interrupted due to the mobility event. Applicant’s Ref: Pl 11865WO02

[0130] 6. The method (200) of embodiment 2, wherein the second indication is included in the second message when the combined PGW-C and SMF has been determined, or when the first network function for mobility management has transmitted a request for restoration of the first PDN connection to the combined PGW-C and SMF but has not received a response from the combined PGW-C and SMF.

[0131] 7. The method (200) of any of embodiment 1-6, wherein the first network function for mobility management is an old or source Mobility Management Entity, MME, and the second network function for mobility management is a new or target MME or Access and Mobility Management Function, AMF.

[0132] 8. A method (300) in a second network function for mobility management, comprising: receiving (310), from a first network function for mobility management, a message including a first indication that a Packet Data Network, PDN, connection is to be restored; and participating (320) in restoration of the PDN connection based on the indication.

[0133] 9. The method (300) of embodiment 8, wherein the message further includes a second indication of an Internet Protocol, IP, address or a node name of a combined PDN Gateway Control plane, PGW-C, and Session Management Function, SMF, towards which the PDN connection is to be restored.

[0134] 10. The method (300) of embodiment 9, wherein said participating (320) in restoration of the PDN connection comprises: restoring the PDN connection towards the combined PGW-C and SMF using the IP address or node name.

[0135] 11 . The method (300) of any of embodiment 8-10, wherein the message is a Context Response or a Forward Relocation Request.

[0136] 12. The method (300) of any of embodiment 8-11, wherein the first network function for mobility management is an old or source Mobility Management Entity, MME, and the second network function for mobility management is a new or target MME or Access and Mobility Management Function, AMF.

[0137] 13. A network node (600), comprising a communication interface (610), a processor (620), and a memory (630), the memory (630) comprising instructions executable by the processor (620) whereby the network node (600) is operative to, when implementing a first network function for mobility management, perform the method according to any of embodiment 1-7, or when implementing a second network function for mobility management, perform the method according to any of embodiment 8-12. Applicant’s Ref: Pl 11865WO02

[0138] 14. A computer-readable storage medium having computer-readable instructions stored thereon, the computer- readable instructions, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to any of embodiment 1-7, or when implementing a second network function for mobility management, perform the method according to any of embodiment 8-12.

[0139] 15. A computer program product, comprising computer-readable instructions which, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to any of embodiment 1-7, or when implementing a second network function for mobility management, perform the method according to any of embodiment 8-12.

[0140] Applicant’s Ref: Pl 11865WO02

[0141] The present disclosure may further include possible changes to the current 3GPP TS 23.007, V18.5.0, as described below in the Appendix A, and possible changes to the current 3GPP TS 29.274, V18.7.0, as described below in the Appendix B, where strikethroughs indicate deleted text and underlines indicate added text. Appendix A

[0142] 3GPP TSG-CT WG4 Meeting #124 C4-243abc

[0143] Maastricht, Netherlands; 19th- 23rdAugust 2024

[0144] For HELP on using this form: comprehensive instructions can be found at http: / / www.3gpp. org / Change-Reguests.

[0145] Proposed change affects: UICC apps| | ME| | Radio Access Network! I Core Network|~x]

[0146] Reason for change: During a PGW triggered PDN connections restoration procedure, the

[0147] MME / ePDG may be requested to move a number of PDN connections associated with the PGW-C / SMF FQ-CSID(s), group ld(s) or PGW Control Plane IP Address(es) to another PGW (as highlighted below), i.e. to restore a large number PDN connections towards the requested PGW.

[0148] Table 7.2.15-5: PGW Change Info within Update Bearer Request Applicant’s Ref: Pl 11865WO02

[0149] Restoring such amount of PDN connections takes time in the serving MME. During such restoration procedures, affected UEs may move so that an inter-MME mobility may take place; in such case, the PDN connection restoration for that UE / PDN connection will be suspended in the source MME (the current serving MME) and prioritize the mobility procedure, i.e. the source MME will include the MME / SGSN / AMF UE EPS PDN Applicant’s Ref: Pl 11865WO02

[0150] Applicant’s Ref: Pl 11865WO02

[0151] 31.5 Inter-MME or AMF-MME mobility

[0152] During inter-MME mobility, the source MME shall transfer the PGW Change Info to the target MME, if available.

[0153] If the source MME has started the PDN connection restoration procedure for one or more PDN connections, which is either as part of the PGW triggered PDN connection restoration specified in clause 31,4, or as part of the MME triggered PDN connection restoration specified in clause 31,3, and if the PDN connection(s) of the UE concerning the inter MME mobility is pending to be restored at the new PGW-C / SMF, the source MME shall set the Pending PDN connection Restoration Indication in the MME / SGSN / AMF UE EPS PDN Connections IE to "1" to request the target MME to perform the PDN connection restoration instead of contacting the PGW-C / SMF as identified in the "PGW S5 / S8 IP Address for Control Plane or PMIP" IE, In addition, the source MME shall include the New PGW-C / SMF IP Address and the New PGW Node Name IES when available, e.g. when the PDN connection was requested to be moved to a specific new PGW-C / SMF during a PGW triggered PDN connection restoration procedure, or when the source MME has selected an alternative PGW-C / SMF and sent the Create Session request message to the new PGW-C / SMF to restore the PDN connection but it had not received the Create Session Response vet.

[0154] During a 5GS to EPS mobility procedure (See also clauses 4.11.1.2.1 and 4.11.1.3.2 of 3GPP TS 23.502

[0046] ), the PGW Change Info shall be populated as part of the MME / SGSN / AMF UE EPS PDN Connections IE from the source AMF to the target MME, if available. For a Home-routed PDU session or a PDU session with an I-SMF, the (H-)SMF may pass the PGW Change Info in the EpsPdnCnxInfo to the V / I-SMF prior to the 5GS to EPS mobility procedure, to enable the V / I-SMF to include the PGW Change Info in the EpsPdnCnxContainer as part of the SmContextRetrievedData. For a non-roaming PDU session without I-SMF, the PGW-C / SMF may include the PGW Change Info directly in the EpsPdnCnxContainer.

[0155] NOTE: Passing the PGW Change Info from the SMF / AMF to the MME during an 5GS to EPS mobility enables the target MME to reselect an alternative PGW-C / SMF if the anchor PGW-C / SMF handling the PDU session fails before or during the handover. Requirements specified in clause 31.2 allow the target MME to reselect an alternative PGW-C / SMF if the anchor PGW-C / SMF handling the PDU session fails after the handover execution.

[0156] Applicant’s Ref: Pl 11865WO02

[0157] Appendix B

[0158] 3GPP TSG-CT WG4 Meeting #124 C4-243abc

[0159] Maastricht, Netherlands; 19th- 23rdAugust 2024

[0160] For HELP on using this form: comprehensive instructions can be found at http: / / www.3gpp. org / Change-Reguests.

[0161] Proposed change affects: UICC apps| | ME| | Radio Access Network! I Core Network|~x]

[0162] Reason for change: During a PGW triggered PDN connections restoration procedure, the

[0163] MME / ePDG may be requested to move a number of PDN connections associated with the PGW-C / SMF FQ-CSID(s), group ld(s) or PGW Control Plane IP Address(es) to another PGW (as highlighted below), i.e. to restore a large number PDN connections towards the requested PGW.

[0164] Table 7.2.15-5: PGW Change Info within Update Bearer Request Applicant’s Ref: Pl 11865WO02

[0165] Restoring such amount of PDN connections takes time in the serving MME. During such restoration procedures, affected UEs may move so that an inter-MME mobility may take place; in such case, the PDN connection restoration for that UE / PDN connection will be suspended in the source MME (the current serving MME) and prioritize the mobility procedure, i.e. the source MME will include the MME / SGSN / AMF UE EPS PDN Connections IE which is still associated with the original PGW-C / SMF. The target MME / AMF will likely experience a failure when communicate to the original PGW-C / SMF (if it has failed) or the original PGW-C / SMF is NOT expected to receive any PDN connection modification for this PDN connection (since it has determined to move the PDN connection to another PGW-C / SMF), such failure should be avoided. Applicant’s Ref: Pl 11865WO02

[0166] Similarily, in MME triggered PDN restoration procedure, which may be triggered by receiving a PGW Restart Notification with the cause “PGW not responding” from the SGW, in such scenario, the MME will identify all affected PDNs which are associated with the failed PGW-C / SMF and perform the restoration procedure for all these PDN connections. So, it is the same, during those restoration procedures, the UEs may perform an inter MME mobility procedure, and the target MME may fail to contact the original PGW-C / SMF.

[0167] Even the restoration of a PDN connection is only for a single UE, in a PGW or MME triggered PDN restoration procedure, when the MME has sent out Create Session Request to the new PGW while waiting for the response message, and if an inter-MME mobility happens, the source MME still keep the PDN as served by the original PGW-C, this will leads the same issue.

[0168] Summary of change: It is proposed that, during inter MME mobility procedure, the source MME includes an indication to indicate the target MME / AMF that the PDN connection is pending to be restored, together with a new PGW-C / SMF IP address (if available), to avoid the signalling failure towards the original PGW-C / SMF.

[0169] Consequences if not Extra signalling towards the original PGW-C / SMF which is deemed failed, approved: and such signalling failure will increase siganlling latency for handover procedure.

[0170] Applicant’s Ref: Pl 11865WO02

[0171] 7.3.1 F orward Relocation Request

[0172] A Forward Relocation Request message shall be sent from:

[0173] - the source MME to the target MME over the S 10 interface as part of an SI -based handover relocation procedure;

[0174] - the source MME to the target SGSN, or from the source SGSN to the target MME over the S3 interface as part of an Inter RAT handover and combined hard handover and SRNS relocation procedures;

[0175] - the source SGSN to the target SGSN over the S16 interface as part of an SRNS Relocation and PS handover procedures;

[0176] - the source MME to the target SGSN over the S3 interface as part of an SRVCC from E-UTRAN to UTRAN or GERAN with DTM HO support procedures and from the source SGSN to the target SGSN over the S16 interface as part of SRVCC from UTRAN (HSPA) to UTRAN or GERAN with DTM HO support;

[0177] - the source MME to the target AMF, or from the source AMF to the target MME over the N26 interface as part of the EPS to 5GS handover and 5GS to EPS handover procedures.

[0178] - the source AMF to the target MME SRVCC over the N26 interface as part of the 5G-SRVCC from NG- RAN to UTRAN procedure.

[0179] A source MME / SGSN which supports CIoT knows whether the target MME / SGSN pool or target AMF (5GS) supports some CIoT optimisations either by using DNS procedures enhanced for DCNs or by local configuration, as specified in clause 5.9 of 3 GPP TS 29.303

[0032] , A source AMF knows whether the target MME pool supports SGi Non-IP or Ethernet PDN connections either by using DNS procedures enhanced for DCNs or by local configuration, as specified in clause 5.9 and 5.13 of 3GPP TS 29.303

[0032] , The target MME / SGSN may forward the Forward Relocation Request to another MME / SGSN in the target MME / SGSN pool which is more suitable to serve the UE, based on the information received in the Forward Relocation Request message, e.g. required CIoT EPS optimisation(s) applicable to the given UE's attachment.

[0180] NOTE 1 : The source MME / SGSN / AMF does not need to know each individual CIoT feature the target MME / SGSN pool or target AMF (5GS) supports. The source MME / SGSN / AMF can behave as if the target MME / SGSN / AMF pool supports all CIoT features when the target MME / SGSN pool is known to support CIoT; the source MME / SGSN / AMF determines then which bearer contexts were successfully transferred as specified in sunclause 7.3.2.

[0181] NOTE 2: Among the CIoT optimization features, only the support of SCEF Non-IP PDN connection and the support of SGi Non-IP PDN connection are applicable to a SGSN.

[0182] NOTE 3 : 5GS supports Attach without PDU session. 5GS can also support Unstructured and Ethernet PDU session types, which are assimilated to "SGi Non-IP PDN connections" over N26.

[0183] Forward Relocation procedure across S10 interface (when KASME is taken into use) shall be performed according to the Rules on Concurrent Running of Security Procedures, which are specified in 3GPP TS 33.401

[0012] ,

[0184] When the source MME / SGSN supports one or more of the CIoT optimization features as specified in clause 8.125, the source MME / SGSN shall transfer EPS bearer context(s) for SGi Non-IP PDN connections or for PDN connections to a SCEF only if the target serving node is known to support SGi Non-IP PDN connections or SCEF Non-IP PDN connections respectively, as specified in clause 5.5.1.2.1 and 5.5.2 of 3GPP TS 23.401 [3], Likewise, a source AMF shall transfer EPS bearer context(s) for SGi Non-IP PDN connections only if the target MME is known to support SGi Non-IP PDN connections. The source MME / SGSN / AMF shall not proceed with the Forward Relocation Request procedure if the UE does not have any EPS bearer context(s) for SGi IP or Non- IP PDN connections that can be transferred to the target serving node, i.e. under the following conditions: Applicant’s Ref: Pl 11865WO02

[0185] - If the UE is attached to the source MME / SGSN with only the PDN connection(s) of PDN type "non-IP" through the SGW and the PGW, with or without SCEF PDN connections, and the target serving node is known to not support S Gi Non-IP PDN Connection (as specified in clause 4.3.17.8.3.3 of

[0186] 3GPP TS 23.401 [3] and in clause 5.3.13.8 of 3GPP TS 23 060

[0035] ); or - If the UE is attached to the source AMF (5GS) with only PDU session(s) of type "Ethernet" or

[0187] "Unstructured", and the target MME is known to not support SGi Non-IP and Ethernet PDN Connection.

[0188] The source MME shall transfer the EPS bearer context(s) for the Ethernet PDN connection only if the target serving node is known to support the Ethernet PDN connection, as specified in clause 5.3.3.1 of 3GPP TS 23.401 [3], The source MME shall not proceed with the Forward Relocation Request procedure if the UE does not have any EPS bearer context(s) that can be transferred to the target serving node, i.e. under the following conditions:

[0189] - If the UE is attached to the source MME with only the PDN connection(s) of PDN type "Ethernet" through the SGW and the PGW, and the target serving node is known to not support the Ethernet PDN connection.

[0190] Table 7.3.1-1 specifies the presence requirements and conditions of the IES in the message. Table 7.3.1 -1 : Information Elements in a Forward Relocation Request Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0191] The PDN Connection grouped IE shall be coded as depicted in Table 7.3.1-2.

[0192] Table 7.3.1 -2: MME / SGSN / AMF UE EPS PDN Connections within Forward Relocation Request Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0193] The Bearer Context grouped IE shall be coded as depicted in Table 7.3.1-3. Table 7.3.1 -3: Bearer Context within MME / SGSN / AMF UE EPS PDN Connections within Forward

[0194] Relocation Request

[0195] Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0196] Table 7.3.1 -4: Remote UE Context Connected within MME / SGSN UE EPS PDN Connections within Forward Relocation Request Table 7.3.1-5: MME UE SCEF PDN Connections within Forward Relocation Request

[0197] Applicant’s Ref: Pl 11865WO02

[0198] Table 7.3.1 -6: Subscribed V2X Information within Forward Relocation Request

[0199] Table 7.3.1 -7: PC5 QoS Parameters within Forward Relocation Request

[0200] Applicant’s Ref: Pl 11865WO02

[0201] Table 7.3.1 -8: PGW Change Info with Forward Relocation Request

[0202] 7.3.6 Context Response A Context Response message shall be sent as a response to a previous Context Request message, in the scenarios identified in clause 7.3.5.

[0203] Possible Cause values are specified in Table 8.4-1. Message specific cause values are: - "IMSI / IMEI not known"

[0204] - "P-TMSI Signature mismatch"

[0205] - "User authentication failed"

[0206] - "Target access restricted for the subscriber"

[0207] Based on the subscription profile, when the access to the target RAT is prohibited for the subscriber, the old MME / SGSN / AMF may reject the Context Request message with the cause "Target access restricted for the subscriber".

[0208] When the source MME / SGSN / AMF supports one or more of the CIoT optimization features as indicated through Applicant’s Ref: Pl 11865WO02 the CIoT Optimizations Support Indication IE specified in clause 8.125, and if the target node is a MME and the target MME has not set the AWOPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125, the source MME / SGSN / AMF shall reject the Context Request with a cause value of "Request Rejected" under the following conditions (conditions are mutually exclusive):

[0209] - If the UE is attached to the source MME / SGSN without any PDN connection through the SGW and PGW and without any SCEF PDN connection;

[0210] - if the UE is attached to the source MME / SGSN with only the PDN connection(s) of PDN type "non-IP", through the SGW and the PGW but the UE has not activated any SCEF PDN connection and the target MME / AMF has not set the SGNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125;

[0211] - if the UE is attached to the the source MME / SGSN with only the SCEF PDN connection(s) but the UE has not activated any PDN connection through the SGW and PGW and the target MME has not set the SCNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125;

[0212] - if the UE is attached to the source MME / SGSN with only PDN connection(s) of PDN type "non-IP", through the SGW and the PGW and at least one SCEF PDN connection and the target MME has neither set the SGNIPDN bit nor the SCNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125;

[0213] - if the UE is registered to the source AMF without any PDU session;

[0214] - if the UE is registered to the source AMF with only PDU session(s) of type "Unstructured" or "Ethernet", and the target MME has not set the SGNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125.

[0215] NOTE 2: Among the CIoT optimization features, only the support of SCEF Non-IP PDN connection and the support of SGi Non-IP PDN connection are applicable to a SGSN.

[0216] NOTE 3 : 5GS supports Attach without PDU session. 5GS can also support Unstructured and Ethernet PDU session types, which are assimilated to "SGi Non-IP PDN connections" over N26 if Ethernet PDN connection type in EPC is not supported; otherwise, the Ethernet PDU session in 5GS can move to EPC seamlessly.

[0217] If the target node is a MME and the target MME has not set the ETHPDN bit in the Indication IE to 1 in the Context Request message as specified in clause 8.12, or the target node is a SGSN, the source MME shall reject the Context Request with a cause value of "Request Rejected" if the UE is attached to the source MME with only PDN connection(s) of PDN type "Ethernet".

[0218] Table 7.3.6-1 specifies the presence requirements and conditions of the IES in the message.

[0219] Table 7.3.6-1 : Information Elements in a Context Response Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0220] Table 7.3.6-2: MME / SGSN / AMF UE EPS PDN Connections within Context Response Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0221] The Bearer Context shall be coded as depicted in Table 7.3.6-3.

[0222] Table 7.3.6-3: Bearer Context within MME / SGSN / AMF UE EPS PDN Connections within Context Response Applicant’s Ref: Pl 11865WO02 Applicant’s Ref: Pl 11865WO02

[0223] Table 7.3.6-4: Remote UE Context Connected within MME / SGSN UE EPS PDN Connections within Context Response

[0224] Table 7.3.6-5: MME / SGSN UE SCEF PDN Connections within Context Response

[0225] Table 7.3.6-6: PGW Change Info with Context Response Applicant’s Ref: Pl 11865WO02

[0226] 8.12 Indication

[0227] Indication is coded as depicted in Figure 8.12-1.

[0228] For each message the applicable flags of the Indication IE shall be clearly specified in the individual message clause. The remaining flags of the Indication IE not so indicated shall be discarded by the receiver.

[0229] The receiver shall consider the value of the applicable flags as "0", if the Indication IE is applicable for the message but not included in the message by the sender.

[0230] The following bits within Octet 5 shall indicate:

[0231] Bit 8 - DAF (Dual Address Bearer Flag): This bit shall be set when the PDN Type, determined based on UE request and subscription record, is set to IPv4v6 and all SGSNs which the UE may be handed over to are Release 8 or above supporting dual addressing, which is determined based on node pre-configuration by the operator..

[0232] Bit 7 - DTF (Direct Tunnel Flag): This bit shall be set when the UE is in UTRAN and Direct Tunnel is selected

[0233] Bit 6 - HI (Handover Indication): If this bit is set to 1 over S 11 / S4 and S5 / S8 interfaces, it shall indicate a UE handover attach. This bit is applicable during the Handover from Trusted or Untrusted Non-3GPP IP Access to E-UTRAN or a Handover from Trusted or Untrusted Non-3GPP IP Access to UTRAN / GERAN procedures (see clauses 8.2, 8.6 and 16.11 of 3GPP TS 23.402

[0045] ), or a 5GS to EPS handover without the N26 interface (see clause 4.11.2.2 of 3GPP TS 23.502

[0083] ). If this bit is set to 1 over GTP based S2a interface, it shall indicate a UE handover from 3GPP access to Trusted Non-3GPP access and UE requested IP address preservation. If this bit is set to 1 over GTP based S2b interface, it shall indicate a UE handover from 3 GPP access to Untrusted Non-3GPP Access and UE requested IP address preservation.

[0234] Bit 5 - DFI (Direct Forwarding Indication): If this bit is set to 1, it shall indicate that direct data forwarding applies between the source RAN and the target RAN during an SI based handover procedure or during an intersystem handover between 5GS and EPS. Applicant’s Ref: Pl 11865WO02

[0235] Bit 4 - 01 (Operation Indication):

[0236] [1] - If this bit is set to 1, it shall denote that the receiving SGW of a "Create Session Request" shall send a Modify Bearer Request immediately to the PGW. This allows the SGW to differentiate if the "Create Session Request" received on S4 / S11 interface belongs to a TAU / RAU with an SGW relocation (OI = 1), or X2 -based handover with SGW relocation (OI = 1) or Enhanced SRNS Relocation with SGW relocation (01=1) or MME triggered Serving GW relocation (OI = 1) or S 1-based handover with SGW relocation (OI = 0).

[0237] [2] - It shall be set to 1 on S4 / S11 interface if the SGW needs to forward the Delete Session Request message to PGW.

[0238] Bit 3 - ISRSI (Idle mode Signalling Reduction Supported Indication): If this is set to 1, it shall indicate that the old / source SGSN / MME and the associated SGW are capable to activate ISR.

[0239] Bit 2 - ISRAI (Idle mode Signalling Reduction Activation Indication): If this bit is set to 1, it shall indicate that the ISR is established between the MME and the S4 SGSN during a TAU / RAU without an SGW change procedure or during an Inter RAT handover without an SGW change procedure. The SGW shall retain the resources for the other CN node that has its bearer resources on the SGW reserved. The old / source SGSN / MME shall maintain the UE's contexts and activate ISR.

[0240] Bit 1 - SGWCI (SGW Change Indication):

[0241] [3] - If this bit is set to 1, it shall indicate that the target MME / SGSN has selected a new SGW during a TAU / RAU or handover with an SGW change procedure.

[0242] [4] - It shall be set to 1 by the target AMF during the EPS to 5GS handover / Idle mode Mobility using N26 interface.

[0243] The following bits within Octet 6 shall indicate:

[0244] Bit 8 - SQCI (Subscribed QoS Change Indication): If this bit is set to 1, it indicates that the subscribed QoS profile of the related PDN connection has changed in the old MME / SGSN when the UE is in ECM-IDLE state and ISR is activated. The new MME / SGSN shall trigger the Subscribed QoS Modification procedure. See 3GPP TS 23.401 [3], clause 5.3.9.2.

[0245] Bit 7 - UIMSI (Unauthenticated IMSI): If this bit is set to 1, it indicates that the IMSI present in the message is not authenticated and is for emergency or RLOS attached UE.

[0246] Bit 6 - CFSI (Change F-TEID support indication): if this bit is set to 1, it indicates that the SGW can change the assigned GTP-U F-TEID in the current procedure. If the SGW needs to modify the GTP-U F-TEfD and the CFSf flag is set to f in the corresponding request message, the SGW shall include the new F-TEID in the Modify Bearer Response / Modify Access Bearers Response message.

[0247] Bit 5 - CRSf (Change Reporting support indication): if this bit is set to f, it indicates that the MME / S4 SGSN supports Location Change Reporting mechanism for the corresponding session.

[0248] Bit 4 - PS (Piggybacking Supported). This bit denotes whether the MME / SGW support piggybacking feature as described in Annex F of 3GPP TS 23.40f [3], if set to i, it indicates that the node is capable of processing two different GTP-C messages appearing back to back in a single UDP payload.

[0249] Bit 3 - PT (S5 / S8 Protocol Type) If this bit set to 1, it shall indicate that the protocol type for the S5 / S8 interface is PMIP; this bit is set to 0 to indicate that the protocol type for the S5 / S8 interface is GTP.

[0250] Bit 2 - SI (Scope Indication): If this bit is set to 1, it indicates that all bearer resources of the UE shall be released by the SGW. This flag is set in messages during TAU / RAU / Handover with SGW change / SRNS Relocation Cancel Using S4 with SGW change / Inter RAT handover Cancel procedure with SGW change / Sl Based handover Cancel procedure with SGW change.

[0251] Bit 1 - MSV (MS Validated): If this bit is set to 1, it shall indicate that the new MME / SGSN has successfully authenticated the UE.

[0252] The following bits within Octet 7shall indicate: Applicant’s Ref: Pl 11865WO02

[0253] Bit 8 - RetLoc (Retrieve Location Indication Flag): if this bit is set to 1, it indicates that the PGW requests the MME / SGSN or TWAN / ePDG to provide the User Location Information.

[0254] Bit 7 - PBIC (Propagate BBAI Information Change): if this bit is set to 1, it indicates a change in the H(e)NB local IP address and / or UDP port number, i.e. the UE moves from an (e)NB to a H(e)NB, or from one H(e)NB to another H(e)NB with the fixed network backhaul changed, or the UE moves from a H(e)NB to a (e)NB.

[0255] Bit 6 - SRNI (SGW Restoration Needed Indication): if this bit is set to 1, it indicates that the source MME / S4-SGSN has not performed the SGW relocation procedure after the source SGW has failed with or without restart, when the source and target MME / S4-SGSN support the MME / S4-SGSN triggered SGW restoration procedure as specified in 3GPP TS 23.007

[0017] ,

[0256] Bit 5 - S6AF (Static IPv6 Address Flag): if this bit is set to 1, it indicates that PDP / PDN IPv6 address is static.

[0257] Bit 4 - S4AF (Static IPv4 Address Flag): if this bit is set to 1, it indicates that PDP / PDN IPv4 address is static.

[0258] Bit 3 - MBMDT (Management Based MDT allowed flag): if this bit is set to 1, it indicates that management based MDT is allowed.

[0259] Bit 2 - ISRAU (ISR is activated for the UE): if this bit is set to 1, it indicates that ISR is activated for the UE before the UE moving to the new SGSN / MME.

[0260] Bit 1 - CCRSI (CSG Change Reporting support indication): if this bit is set to 1, it indicates that the MME / S4 SGSN supports CSG Information Change Reporting mechanism for the corresponding session. The following bits within Octet 8 shall indicate:

[0261] Bit 8 - CPRAI (Change of Presence Reporting Area information Indication): when ISR is active if this bit is set to 1, it indicates that the Presence Reporting Area information, which is provided as a part of the Presence Reporting Area Information IE, has changed since last reported by the MME / S4-SGSN. The SGW shall ignore this flag when ISR is not active.

[0262] Bit 7 - ARRL (Abnormal Release of Radio Link): if this bit is set to 1 by the MME, it indicates to the SGW that the access bearers are released due to an abnormal release of the radio link. Based on operator policy, this indication may be used by the SGW in subsequent decisions to trigger PDN charging pause if the PGW Pause of Charging feature has been enabled on that PDN connection.

[0263] Bit 6 - PPOFF (PDN Pause Off Indication): if this bit is set to 1 by the SGW, it indicates to the PGW that the charging for the PDN connection shall be unpaused.

[0264] Bit 5 - PPON (PDN Pause On Indication) / PPEI (PDN Pause Enabled Indication): if this bit is set to 1 by the SGW, it indicates to the PGW that the charging for the PDN connection shall be paused; if it is set to 1 by the PGW, it indicates that PGW enables the SGW to use the PGW Pause of Charging procedure for the PDN connection.

[0265] Bit 4 - PPSI (PDN Pause Support Indication): if this bit is set to 1 by the SGW, it indicates that the SGW supports the PGW Pause of Charging procedure; if it is set to 1 by the PGW, it indicates that the PGW supports the PGW Pause of Charging procedure.

[0266] Bit 3 - CSFBI (CSFB Indication): if this bit is set to 1, it indicates that the UE has been subject to CSFB.

[0267] Bit 2 - CLII (Change of Location Information Indication): when ISR is active if this bit is set to 1, it indicates that the location information, which is provided as a part of ULI IE, has changed since last reported by the MME / S4-SGSN. The SGW shall ignore this flag when ISR is not active.

[0268] Bit 1 - CPSR (CS to PS SRVCC indication): if this bit is set to 1, it indicates that a UTRAN / GERAN to E- UTRAN / UTRAN (HSPA) SRVCC procedure is underway and the associated message, i.e. Modify Bearer Request shall be forwarded to the PGW from the SGW as specified in 3GPP TS 23.216

[0043] , The following bits within Octet 9 shall indicate: Applicant’s Ref: Pl 11865WO02

[0269] Bit 8 - NSI (NBIFOM Support Indication): if this bit is set to 1, it indicates to the PGW that the NBIFOM is supported (see clause 5.10 of 3GPP TS 23.161

[0071] ).

[0270] Bit 7 - UASI (UE Available for Signaling Indication): if this bit is set to 1, it indicates that the UE is available for end to end signalling and that the PGW should re-attempt the pending network initiated procedure.

[0271] Bit 6 - DTCI (Delay Tolerant Connection Indication): if this bit is set to 1, it indicates that the PDN connection is delay tolerant according to the local policies in the PGW, e.g. per APN.For this PDN connection the PGW supports receiving the rejection cause "UE is temporarily not reachable due to power saving" from the MME / SGSN via the SGW during a network initiated procedure and holding the network initiated procedure, until the PGW receives the subsequent Modify Bearer Request message with the UASI flag indicating that the UE is available for end to end signalling.

[0272] Bit 5 - BDWI (Buffered DL Data Waiting Indication): if this bit is set to 1, it indicates that there is DL data buffered in the (old) SGW or (V-)SMFZUPF, i.e. that the new MME / SGSN shall invoke data forwarding if there is an SGW change as specified in clause 5.3.3.1 A of 3GPP TS 23.401 [3] or upon idle mode mobility between 5GS and EPS with data forwarding as specified in clauses 4.11.1.3.2A, 4.11.1.3.3A, 4.23.12.2a and 4.23.12.3a of 3GPP TS 23.502

[0083] , and that it shall setup the user plane in conjunction with the TAU / RAU procedure for delivery of the buffered DL data to the UE.

[0273] Bit 4 - PSCI (Pending Subscription Change Indication): If this bit is set to 1, it indicates that there is a pending report of the changed subscribed QoS profile of the related PDN connection in the old MME, so that the new MME / SGSN shall trigger the HSS Initiated Subscribed QoS Modification procedure towards the PGW. See clause 5.3.9.2 of 3GPP TS 23.401 [3],

[0274] Bit 3 - PCRf (P-CSCF Restoration Indication): if this bit is set to 1, it indicates a request to trigger a P- CSCF restoration for the corresponding user (see 3 GPP TS 23.380

[0061] ).

[0275] Bit 2 - AOSI (Associate OCI with SGW node's Identity): if this bit is set to 1, it indicates that the SGW provided "SGW's Overload Control Information" which shall be associated with the node identity (i.e. FQDN or the IP address received from the DNS during the SGW selection) of the serving SGW.

[0276] Bit 1 - AOPI (Associate OCI with PGW node's Identity): if this bit is set to 1, it indicates that the PGW provided "PGW's Overload Control Information" which shall be associated with the node identity (i.e. FQDN or the IP address received from the HSS or DNS during the PGW selection) of the serving PGW.

[0277] The following bits within Octet 10 shall indicate:

[0278] Bit 8 - ROAAI (Release Over Any Access Indication): If this bit is set to 1, it indicates to the PGW that, if this is an NB-IFOM PDN connection, the PGW shall initiate the release of the corresponding PDN connection over the non-3GPP access over the S2a / S2b interface with the cause "Local release".

[0279] Bit 7 - EPCOSI (Extended PCO Support Indication): If this bit is set to 1, it indicates to the receiver that the Extended PCO is supported, e.g. when the PGW is the receiver, it indicates that the UE, the MME and the SGW support Extended PCO; when the target MME is the receiver, during an inter-MME mobility, it indicates that UE and the source MME support Extended PCO.

[0280] Bit 6 - CPOPCI (Control Plane Only PDN Connection Indication): If this bit is set to 1, it indicates that the PDN Connection is set to Control Plane Only, i.e. the user data pertaining to this PDN connection can only be transferred in NAS PDUs via the control plane.

[0281] Bit 5 - PMTSMI (Pending MT Short Message Indication): If this bit is set to 1, it indicates to the target MME / S4-SGSN that there is one (or more) pending MT Short Message(s) in the SMS-GMSC, i.e. that the target MME / S4-SGSN shall provide its E.164 address and Diameter Identity if available to receive the MT Short message and maintain the signalling connection with the UE for a longer time to enable the retransmission of the Short Message.

[0282] Bit 4 - S 11 -U Tunnel Flag (SI 1TF) : This flag shall be set to 1 on the S 11 interface if user data is transported in NAS signalling. Applicant’s Ref: Pl 11865WO02

[0283] Bit 3 - PNSI (Pending Network Initiated PDN Connection Signalling Indication): if this bit is set to 1, it indicates to the target MME / SGSN that there is pending network initiated PDN connection signalling for the PDN connection, i.e. the target MME / SGSN shall set UASI flag in the Create Session Request or Modify Bearer Request message to indicate to the PGW that the UE is available for end to end signalling.

[0284] Bit 2 - UNACCSI (UE Not Authorised Cause Code Support Indication): If this bit is set to 1, it indicates that the Cause Code for "UE not authorized by OCS or external AAA Server" is supported by the S4-SGSN / MME.

[0285] Bit 1 - WLCP PDN Connection Modification Support Indication (WPMSI): if this bit is set to 1, it indicates that the TWAN supports the WLCP PDN Connection Modification procedure. This indication is used by the P- CSCF restoration extension procedure for TWAN access (see 3GPP TS 23.380

[0061] ).

[0286] The following bits within Octet 11 shall indicate:

[0287] Bit 8 - 5GSNN26 (5GS Interworking without N26 Indication): if this bit is set to 1 and the 5GS Interworking Indication (5GSIWKI) is set to 1, it indicates to the PGW-C+SMF that 5GS Interworking is supported without the N26 interface. If this bit is set to 0 and the 5GSIWKI (5GS Interworking Indication) is set to 1, it indicates to the PGW-C+SMF that 5GS Interworking is supported with the N26 interface.

[0288] Bit 7 - REPREFI (Return Preferred Indication): This flag shall be set to 1 to indicate a preferred return of the UE to the last used EPS or 5GS PLMN at a later access change to an EPS or 5GS shared network.

[0289] Bit 6 -5GSIWKI (5GS Interworking Indication): This flag shall be set to 1 for UEs supporting N1 mode and not restricted from interworking with 5GS by user subscription (see "5GC" bit within Core-Network- Restrictions AVP and Interworking-5GS-Indicator AVP specified in 3GPP TS 29.272

[0070] and 3GPP TS 29.273

[0068] ).

[0290] Bit 5 -EEVRSI (Extended EBI Value Range Support Indication): if this bit is set to 1, it indicates that the sending GTPv2 entity supports the 15 EPS Bearers, i.e. it supports to use EPS Bearer ID with a value between T' and '15'.

[0291] Bit 4 -LTEMUI (LTE-M UE Indication): if this bit is set to 1, it indicates that the UE is a LTE-M UE (see 3GPP TS 23.401 [3]); this bit shall only be applicable to the Forward Relocation Request and Context Response messages; it should be set to "0" by the sender and it shall be ignored by the receiver in other messages.

[0292] Bit 3 - LTEMPI (LTE-M RAT Type reporting to PGW Indication): if this bit is set to 1, it indicates to the SGW to forward the LTE-M RAT type to the PGW;

[0293] Bit 2 - ENBCRSI (eNB Change Reporting Support Indication): if this bit is set to 1, it indicates that the MME supports Macro eNodeB Change Reporting mechanism for the corresponding session.

[0294] Bit 1 -TSPCMI (Triggering SGSN initiated PDP Context Creation / Modification Indication): if this bit is set to 1, it indicates to the S4-SGSN that in the UE initiated PDP Context Modification procedure, when the NBIFOM container is included, the S4-SGSN accepts the UE initiated PDP Context Modification procedure and initiates SGSN initiated PDP Context Creation / modification procedures respectively towards UE to transfer the NBIFOM container received from the PGW either in Create Bearer Request or Update Bearer Request message as specified in 3GPP TS 23.161

[0071] ,

[0295] The following bits within Octet 12 shall indicate:

[0296] Bit 8 - CSRMFI (Create Session Request Message Forwarded Indication): if this bit is set to 1, it indicates that the Create Session Request message has been forwarded by a PGW, and the receiving PGW shall include its PGW FQDN in the Create Session Response message if the creation of the PDN connection is accepted.

[0297] Bit 7 - MTEDTN (MT-EDT Not Applicable): if this bit is set to 1, it indicates that MT-EDT is not applicable for the PDN connection.

[0298] Bit 6 - MTEDTA (MT-EDT Applicable): if this bit is set to 1, it indicates that MT-EDT is applicable for the PDN connection.

[0299] Bit 5 - N5GNMI (No 5GS N26 Mobility Indication): if this bit is set to 1, it indicates that the PDN connection cannot be moved to 5GS via N26. Applicant’s Ref: Pl 11865WO02

[0300] Bit 4 -5GCNRS (5GC Not Restricted Support): if this bit is set to 1, this indicates to the PGW-C+SMF that the sending node (i.e. MME or ePDG) supports setting the 5GCNRI flag. An MME or an ePDG compliant with this version of the specification shall support setting the 5GCNRI flag.

[0301] Bit 3 -5GCNRI (5GC Not Restricted Indication): if this bit is set to 1, this indicates to the PGW-C+SMF that access to the 5GC is not restricted for the PDN connection. If the 5GCNRS bit is set to 1 and the 5GCNRI bit is set to 0, this indicates that access to the 5GC is restricted for the PDN connection. The 5GCNRI flag shall be ignored by the PGW-C+SMF if the 5GSIWKI flag is set to 1 (i.e. 5GS Interworking is supported), except for the case noted in Note 27 in Table 7.2.1-1.

[0302] Bit 2 - 5SRHOI (5G-SRVCC HO Indication): if this bit is set to 1, it indicates the HO is used for 5G- SRVCC as specified in 3GPP TS 23.216

[0043] ,

[0303] Bit 1 - ETHPDN (Ethernet PDN Support Indication): if this bit is set to 1, it indicates the support of Ethernet PDN Connection.

[0304] The following bits within Octet 13 shall indicate:

[0305] Bit 8 - NSPUSI (Notify Start Pause of charging via User plane Support Indication): if this bit is set to 1, it indicates that the PGW-C and PGW-U support Notify Start Pause of Charging via user plane feature as specified in clause 5.30 of 3GPP TS 29.244

[0080] ,

[0306] Bit 7 - PGWRNSI (PGW Redirection due to mismatch with Network Slice subscribed by UE Support Indication): if this bit is set to 1, it indicates that the MME supports receiving a Create Session rejection response with the cause "PGW redirection due to mismatch with network slice subscribed by the UE" and to establish the PDN connection towards the Alternative PGW-C / SMF indicated in the Create Session rejection response.

[0307] Bit 6 - RPPCSI (Restoration of PDN connections after an PGW-C / SMF Change Support Indication): if this bit is set to 1, it indicates that the sending GTPv2 entity, i.e. the MME / ePDG and / or the SGW, supports the Restoration of PDN connections after an PGW-C / SMF Change procedure as specified in clause 31 of 3GPP TS 23.007

[0017] ,

[0308] Bit 5 - PGWCHI (PGW CHange Indication): if this bit is set to 1, it indicates that the Create Session Request is triggered to move an existing PDN connection to the new PGW-C / SMF as specified in clauses 31.3 and 31.3A of 3GPP TS 23.007

[0017] ,

[0309] Bit 4 - SISSME (Same IWK-SCEF Selected for Monitoring Event Indication): if this bit is set to 1, it indicates that same IWK-SCEF is selected by target MME / SGSN for Monitoring Event.

[0310] Bit 3 - NSENBI (Notify Source eNodeB fndication): if this bit is set to f, it indicates that the source MME shall send a Handover Success to the source eNodeB (see clause 5.5.1.2.2a of 3GPP TS 23.401 [3]).

[0311] Bit 2 - IDFUPF (Indirect Data Forwarding with UPF Indication): if this bit is set to 1, it indicates that indirect data forwarding is required for user plane routes from / to a UPF.

[0312] Bit 1 - EMCI (Emergency PDU Session Indication): if this bit is set to 1, it indicates the UE has emergency PDU session, as specified in 3GPP TS 23.216

[0043] , The following bits within Octet 14 shall indicate:

[0313] Bits 6 to 8: Spare, for future use and set to 0.

[0314] Bit 5 - PPRI (Pending PDN connection Restoration Indication): if this bit is set to 1, it indicates that the PDN connection restoration to be performed in the target MME / AMF, e.g„ when the PDN connection restoration is suspended or interrupted in the source MME,

[0315] Bits 4 -LAPCOSI (Large Additionl Protocol Configuration Options Support Indication): If this bit is set to 1 by the ePDG, it indicates that the ePDG supports receiving an APCO IE with the APCO field larger than 253 octets;

[0316] Bit 3 -LTEMSAI (LTE-M Satellite Access Indication): if this bit is set to 1, it indicates that the LTE-M UE is accessing Satellite E-UTRAN (see 3GPP TS 23.401 [3]); Applicant’s Ref: Pl 11865WO02

[0317] Bit 2 -SRTPI (Satellite RAT Type reporting to PGW Indication): if this bit is set to 1, it indicates to the SGW to forward the Satellite related RAT type to the PGW;

[0318] Bit 1 - UPIPSI (User Plane Integrity Protection Support Indication): if this bit is set to 1, it indicates that the UE, MME and E-UTRAN supports User Plane Integrity Protection with EPS as specified in clause 4.11.0a.5 of 3GPP TS 23.502

[0083] ,

Claims

Applicant’s Ref: P111865WO02CLAIMS1 . A method (200) in a first network function for mobility management, comprising: participating (210) in restoration of at least one Packet Data Network, PDN, connection including a first PDN connection associated with a User Equipment, UE; receiving (220), before the restoration of the first PDN connection is completed, a first message associated with a mobility event of the UE towards a second network function for mobility management; and transmitting (230), to the second network function for mobility management, a second message including a first indication that the first PDN connection is to be restored.

2. The method (200) of claim 1 , wherein the second message further includes a second indication of an Internet Protocol, IP, address or a node name of a combined PDN Gateway Control plane, PGW-C, and Session Management Function, SMF, towards which the first PDN connection is to be restored.

3. The method (200) of claim 1 or 2, wherein the mobility event comprises Tracking Area Update, TAU, and the second message comprises a Context Response.

4. The method (200) of claim 1 or 2, wherein the mobility event comprises handover and the second message comprises a Forward Relocation Request.

5. The method (200) of any of claims 1 -4, wherein the first indication is included in the second message when the restoration of the at least one PDN connection has been initiated but the restoration of the first PDN connection has not started yet, or when the restoration of the first PDN connection has started but is interrupted due to the mobility event.

6. The method (200) of claim 2, wherein the second indication is included in the second message when the combined PGW-C and SMF has been determined, or when the first network function for mobility management has transmitted a request for restoration of the first PDN connection to the combined PGW-C and SMF but has not received a response from the combined PGW-C and SMF.

7. The method (200) of any of claims 1 -6, wherein the first network function for mobility management is an old or source Mobility Management Entity, MME, and the second network function for mobility management is a new or target MME or Access and Mobility Management Function, AMR8. A method (300) in a second network function for mobility management, comprising:58Applicant’s Ref: P111865WO02 receiving (310), from a first network function for mobility management, a message including a first indication that a Packet Data Network, PDN, connection is to be restored; and participating (320) in restoration of the PDN connection based on the indication.

9. The method (300) of claim 8, wherein the message further includes a second indication of an Internet Protocol, IP, address or a node name of a combined PDN Gateway Control plane, PGW-C, and Session Management Function, SMF, towards which the PDN connection is to be restored.

10. The method (300) of claim 9, wherein said participating (320) in restoration of the PDN connection comprises: restoring the PDN connection towards the combined PGW-C and SMF using the IP address or node name.11 . The method (300) of any of claims 8-10, wherein the message is a Context Response or a Forward Relocation Request.

12. The method (300) of any of claims 8-11, wherein the first network function for mobility management is an old or source Mobility Management Entity, MME, and the second network function for mobility management is a new or target MME or Access and Mobility Management Function, AMR13. A network node (600), comprising a communication interface (610), a processor (620), and a memory (630), the memory (630) comprising instructions executable by the processor (620) whereby the network node (600) is operative to, when implementing a first network function for mobility management, perform the method according to any of claims 1-7, or when implementing a second network function for mobility management, perform the method according to any of claims 8-12.

14. A computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to any of claims 1-7, or when implementing a second network function for mobility management, perform the method according to any of claims 8-12.

15. A computer program product, comprising computer-readable instructions which, when executed by a processor of a network node, configure the network node to, when implementing a first network function for mobility management, perform the method according to any of claims 1-7, or when implementing a second network function for mobility management, perform the method according to any of claims 8-12.59

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