WO2018127455A1

WO2018127455A1 - Optimization of gateway relocation in a mobile system

Info

Publication number: WO2018127455A1
Application number: PCT/EP2017/084793
Authority: WO
Inventors: Bruno Landais; William STOECKLIN; Laurent Thiebaut; Nicolas Drevon
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2017-01-09
Filing date: 2017-12-29
Publication date: 2018-07-12
Anticipated expiration: 2019-07-09
Also published as: EP3346759A1; ES2974041T3; EP3346759B1

Abstract

Embodiments of the invention include a mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions, said mobile network entity configured to: - send to a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, a request to initiate the release of an established connectivity for a User Equipment UE when no service that breaks (or that makes user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

Description

OPTIMIZATION OF GATEWAY RELOCATION IN A MOBILE SYSTEM

The present invention generally relates to mobile communication networks and systems.

Detailed descriptions of mobile communication networks and systems can be found in the literature, such as in particular in Technical Specifications published by standardization bodies such as for example 3GPP (3^rd Generation Partnership Project).

In general, in a mobile system, a User Equipment (UE) has access to various services (such as IP services) in an external network (such as IP network) via a mobile network providing connectivity (such as IP connectivity). A mobile network generally comprises a Core Network accessed via an access network, such as a Radio Access Network. Procedures are defined in such networks and systems for managing (establishing, releasing, ...) the connectivity between the UE and a Gateway associated with the external network.

An example of mobile system is Evolved Packet System (EPS), also referred to as 4G system, specified in particular in 3GPP TS 23.401. In EPS, an external network is called Packet Data Network (PDN), a Gateway is called PDN Gateway (PGW), and connectivity between UE and PGW is represented by a PDN connection.

Another example of mobile system is Next Generation (Next Gen) system, also referred to as 5G system, current being specified by 3GPP, such as in 3GPP TR 23.799. In a Next Generation system, an external network is called Data Network (DN), a Gateway is split into two functions: control plane functions provided by a Session Management Function (SMF) and user plane functions provided by a User Plane Function (UPF), and connectivity between UE and Data Network via UPF is represented by a PDU session.

A function called Selected IP Traffic Offload (SIPTO) has been specified in particular in 3GPP TS 23.401. The SIPTO function enables an operator to offload certain types of traffic at a network node close to the UE's point of attachment to the access network.

As currently specified in clause 4.3.15 of 3GPP TS 23.401:

"For SIPTO above RAN, as a result of UE mobility (e.g. detected by the MME at TAU or SGSN at RAU or movement from GERAN), the target MME may wish to redirect a PDN connection towards a different GW that is more appropriate for the UE's current location, e.g. MME may know whether the UE's new location is served by the same GW as the old one. When the MME decides upon the need for GW relocation, the MME deactivates the impacted PDN connections indicating "reactivation requested" as specified in clause 5.10.3."

As currently specified in clause 5.10.3 of 3GPP TS 23.401:

"The UE requested PDN disconnection procedure is also used as part of the SIPTO function when the MME determines that GW relocation is desirable. In this situation the MME deactivates the PDN connection(s) relevant to SIPTO- allowed APN(s) using the "reactivation requested" cause value, and the UE should then re-establish those PDN connection(s).

It shall be possible to configure the MME to deactivate a PDN connection, for PDN GW relocation due to SIPTO above RAN, only when UE is in ECM-IDLE mode or during a Tracking Area Update procedure without established RAB(s)".

As recognized by the inventors and as will be discussed later with more detail, there is a need, in particular with the introduction in EPS of a new feature called "Light Connection", to enhance a function such as the SIPTO function, such that a PDN connection can be deactivated not only when the UE is seen as in idle mode by the core network, but also (and without negative impact to the user's experience) when the UE is seen as in connected mode by the core network. More generally, there is a need to optimize functions such as Gateway relocation in such networks and systems.

Embodiments of the present invention in particular address such needs.

Embodiments of the present invention apply not only to EPS (or 4G) systems, for which the SIPTO function is currently specified in particular in 3GPP TS 23.401, but also to other systems, such as in particular NextGen (or 5G) systems, in which a mode referred to as SSC mode 2 (including releasing an initial PDU session connectivity before setting up a new PDU session connectivity) is currently being specified. These and other objects are achieved, in one aspect, by a mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions, said mobile network entity configured to:

- send to a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, a request to initiate the release of an established

connectivity for a User Equipment UE when no service that breaks (or that makes user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

These and other objects are achieved, in another aspect, by a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, configured to:

- receive a request or detect the need to initiate the release of an established connectivity for a User Equipment UE when no service that breaks (or that makes user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

These and other objects are achieved, in another aspect, by a mobile network entity such as PCRF or PCF providing policy control functions, configured to:

- receive from a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, at least one of:

- information about a request to initiate release an established connectivity for a User Equipment UE when no service, referred to as sensitive service, that breaks (or that makes user's experience unacceptable) at IP address change of the UE, is ongoing on said established connectivity,

- an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including said initiation of release of said connectivity, by said network, when no sensitive service is on-going. These and other objects are achieved, in another aspect, by a mobile network entity such as TDF providing traffic detection functions, configured to perform at least one of:

- receive from a mobile network entity such as PCRF providing policy control functions, a request to detect absence of on-going service that breaks (or that makes user's experience unacceptable) at IP address change of a User

Equipment UE, referred to as sensitive service, on an established connectivity,

- monitor the user plane traffic over said connectivity for detecting the absence of on-going sensitive service,

- inform said mobile network entity such as PCRF, of a detected absence of on-going sensitive service for said connectivity.

These and other objects are achieved, in another aspect, by a User

Equipment, UE, configured to:

- send towards a mobile network entity, such as SMF providing session management functions, such as at establishment of a connectivity for said UE, an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including initiation of release of said connectivity, by said network, when no service that breaks (or that makes user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is ongoing on said established connectivity.

These and other objects are achieved, in one aspect, by a method for optimization of Gateway relocation in a mobile system, said method including at least one step performed by at least one of the thus configured entities: a mobile network entity such as MME/SGSN or AMF, a mobile network entity such as PGW or SMF, a mobile network entity such as PCRF or PCF, a mobile network entity such as TDF, a User Equipment UE. Some embodiments of apparatus and/or methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings, in which:

- Figure 1 is intended to illustrate in a simplified way a first example of a sequence of flows according to embodiments of the invention,

- Figure 2 is intended to illustrate in a simplified way a second example of a sequence of flows according to embodiments of the invention,

- Figure 3 is intended to illustrate in a simplified way a third example of a sequence of flows according to embodiments of the invention,

- Figure 4 is intended to illustrate in a simplified way a fourth example of a sequence of flows according to embodiments of the invention.

Abbreviations

AMF Access and Mobility Function

EPS Evolved Packet System

MME Mobility Management Entity

PCRF Policy and Charging Rules Function

PCF Policy Control Function

PDN Packet Data Network

PGW PDN Gateway

SGSN Serving GPRS Support Node

SMF Session Management Function

SGW Serving Gateway

TDF Traffic Detection Function

UE User Equipment

UPF User Plane Function

Description of various aspects and/or embodiments of the invention

In the following, embodiments of the invention will be mainly described, by way of example only, for the case of EPS (4G) system. However, as indicated above, embodiments of the invention are not limited to such example. In particular, embodiments of the invention also apply to Next Generation (5G) system. SIPTO (Selected IP Traffic Offload) enables an operator to offload certain types of traffic (e.g. Internet) at a network node (PGW) close to the UE's point of attachment to the access network. See 3GPP TS 23.401 subclause 4.3.15.

Corresponding procedures have been specified in 3GPP for the MME/SGSN to select an SGW and PGW based on the current user location (e.g. Tracking Area Identity, Cell ID, eNB ID) and to re-allocate a different PGW upon UE's mobility.

Re-allocating a PGW implies, per existing procedures, to tear down the existing PDN connection between the UE and the PGW and to request the UE to reestablish a new PDN connection. As this entails a change of the IP address assigned to the UE and the potential loss of the on-going services of the UE, the MME/SGSN is required currently to re-allocate a PGW to the UE when the UE is in idle mode or performing a mobility procedure (without data radio bearers) such as a Tracking Area Update.

However today, smartphones can remain in connected mode (with data radio bearers) over a long period of time, e.g. due to the user's traffic pattern or due to the RAN maintaining the UE in connected mode (even if not necessarily always active) to minimize the number of transitions between the idle and connected mode (which are known to cause excessive signalling overhead in the EPS). Furthermore, 3GPP is standardizing a new Light Connection for LTE feature in Rel-14/Rel-15 (see RAN Work Item in RP-160540, "Signalling reduction to enable light connection for LTE), whereby an S1 signalling connection will be maintained between the eNB and the MME even for a UE that is in RRC idle or RRC suspended state, to minimize the network signalling overhead required for UE idle (or suspended) <> connected transitions. This feature is being designed such as when the MME has a S1 signalling connection for the UE, it remains unaware of whether the UE is RRC idle (or suspended) or RRC connected over the radio interface.

This makes the existing procedures to reallocate the PGW for UEs in idle mode inefficient and the situation is going to worsen a lot with the new Light Connection to LTE feature (where the MME might never be able to trigger a PGW relocation). This can result in PGWs remaining far to the UE's point of attachment, when the UE is moving, causing inefficient user path in the network and preventing to offload the user's traffic close to its point of attachment, as intended by the SIPTO feature. The only solution that exists today is to relocate the PGW when the UE is seen as in IDLE mode by the Core Network, as specified in TS 23.401 clause 5.10.3: "This procedure is also used as part of the SIPTO function when the MME determines that GW relocation is desirable. In this situation the MME deactivates the PDN connection(s) relevant to SIPTO-allowed APN(s) using the "reactivation requested" cause value, and the UE should then re-establish those PDN

connection(s). It shall be possible to configure the MME to deactivate a PDN connection, for PDN GW relocation due to SIPTO above RAN, only when UE is in ECM-IDLE mode or during a Tracking Area Update procedure without established RAB(s)". An MME/SGSN is not aware on the traffic being exchanged on a PDN connection for a UE in connected mode. So the MME/SGSN cannot initiate currently a PDN disconnection for a UE in connected mode as this would result in breaking sensitive user application such as real-time communication (e.g. VoLTE calls), gaming, etc.

According to embodiments of the invention, the network shall be able to deactivate a PDN connection when the user is not currently using sensitive services (i.e. services that break when the IP address of the user is changed).

Specifically, embodiments of the invention include one or more of :

- when detecting the need to relocate a PGW (i.e. reallocate a different PGW) to a PDN connection), the MME/SGSN shall request the current PGW to initiate a PDN disconnection procedure when no sensitive user applications are going on within that PDN connection;

- the PGW, optionally under the control of the PCRF, or the TDF, monitors whether the user is running sensitive services, and initiates the procedure to release the PDN connection towards the UE (with a request to re-establish the PDN connection) when the UE stops using these services.

Embodiments of the invention allow the operator to control the trade off between the network efficiency and the end-user experience. The PGW or PCRF takes a policy decision based on service category usage, deferring any mitigation till users stop using sensitive applications like gaming or real-time communication.

Embodiments of the invention enhance the end-user experience:

• no explicit detach for UE connected to VoLTE and data

· No call loss

round-trip time improves browsing and streaming experience

According to embodiments of the invention, the network shall be able to deactivate a PDN connection when the user is not currently using "sensitive services" (i.e. services that break when the IP address of the user is changed).

Embodiments of the invention may include performing one or more of following steps:

1 . Initial condition: A PDN connection is set-up. Services considered as

"sensitive services" may be defined by operator's policies, e.g. in the PGW, PCRF or TDF. The PGW allocated in step 1 is noted PGW1 .

2. The MME/SGSN may detect the need for reallocating a different PGW, such as PGW2, to a PDN connection, e.g. for SIPTO reasons, for a UE in connected mode (i.e. with an S1 signalling connection). This detection may take place during mobility procedures performed in connected mode, e.g. during a S1/lu handover procedure or an X2 handover procedure (i.e. MME receiving an S1 Path Switch Request), see subclause 5.5 of TS 23.401 . The MME/SGSN may request the PGW to initiate the release of the PDN connection when the user is not running sensitive services that should not be interrupted. This may be done e.g. by the MME/SGSN sending a GTP-C Modify Bearer Request to the PGW (via the SGW), with a new information element to request so.

The PGW, optionally under the control of the PCRF, or the TDF, under the control of the PCRF, may monitor the user traffic to detect whether the user is currently using sensitive services that should not be interrupted. When it is detected that the UE has stopped or is not using such sensitive services, the PGW may initiate the procedure to release the PDN connection as described in step 5.

This step 4 may also be initiated by the PGW under other triggers than step 3 e.g. upon specific request from the PCRF.

When it is appropriate to do so based on the monitoring of the user's traffic, the PGW may initiate the procedure to release the PDN connection towards the UE (as specified in TS 23.401 subclause 5.4.4.1 ), including a request to re-establish the PDN connection (i.e. it uses the cause "reactivation requested"). This may be done e.g. by the PGW sending a GTP-c Delete Bearer Request (indicating PDN connection deactivation, and re-activation requested). This is e.g. when the user is no longer using sensitive services (or applications) or e.g. upon expiry of an operator defined time period. When a TDF is used to monitor the user's traffic, the PCRF may instruct the PGW to initiate the release of the PDN connection with the cause

"reactivation requested".

A PDN connection may then be established with PGW2.

Example call flows are illustrated in figures 1 to 4:

These calls flows detail the steps 1 -5 above in different deployments. The differences between the deployments correspond to various embodiments including various embodiments of step 4.:

a. There is no PCRF: the PGW may be configured with the list of

sensitive services and react autonomously (an example is illustrated in Figure 1 )

b. Upon reception of the MME/SGSN request, the PGW may notify the PCRF and the PCRF may ask the PGW to monitor the sensitive services (an example is illustrated in Figure 2)

c. Upon reception of the MME/SGSN request, the PGW may notify the PCRF and the PCRF may ask the TDF to monitor the sensitive services (an example is illustrated in Figure 3)

d. The PCRF may have provided the list of sensitive services to the PGW at PDN connection set-up (when the PDN connection is eligible to a release for PGW location optimization) and the PGW may monitor the sensitive services from the beginning of the PDU connection (an example is illustrated in Figure 4). This alternative assumes that the MME/SGSN has indicated to the PGW, during the establishment of the PDN connection, whether the PDU connection may be eligible to a release for PGW location optimization e.g. with SIPTO.

NOTE: In the drawings the SGW is omitted to make the drawings simpler but the interactions between PGW and MME/SGSN take place via the SGW.

NOTE: Only Figures 1 and 4 show the overall procedure. The other call flows (2 and 3) show only the different embodiments of step 4

NOTE: When the UE uses a light connection for LTE, the PGW or TDF will detect that no user's traffic at all is currently being exchanged with the UE (but the MME/SGSN is not aware of that).

As already indicated, the examples described above correspond by way of example to the case of EPC (4G Core Network). In case of 5GC (5G Core):

• The notion of PDN connection would be replaced by the equivalent notion of PDU session

• The step 3 may correspond to SMF (the Session Manager, entity playing a similar role than a PGW Control Plane) receiving a notification (of mobility of the UE) that has been initiated by AMF (Access and Mobility Management, entity playing a similar role than the MME)

• The UPF takes a similar role to the User Plane of the PGW (traffic detection upon SMF

control)

· The AMF does not send an explicit request to initiate the release of an

established PDU session for a UE when no service that breaks at IP address change of the UE, referred to as sensitive service, is on-going on said PDU session; instead it sends a notification of UE mobility to SMF and the SMF deduces the need to initiate the release of an established PDU session when no service that breaks at IP address change of the UE, referred to as sensitive service, is on-going on this PDU session

• The Step 4 may correspond to the SMF initiating procedures related with SSC mode 2 (release the initial PDU session connectivity before setting up a new PDU session connectivity).

· When the PDU session corresponds to a unique connectivity (IP address / IPv6 prefix, ...) the step 5 may correspond to a NAS SM signalling sent directly by the SMF to the UE (with AMF acting as transparent relay): Step 5 above becomes "When it is appropriate to do so based on the monitoring of the user's traffic, the SMF may initiate the procedure to release the PDN connection towards the UE. This corresponds to the SMF sending a PDU session release request to the UE via the AMF.

• When the PDU session corresponds to an IPv6 multi-homing a PDU session and thus with multiple IPv6 anchor points, the detection of the absence of sensitive traffic and the corresponding release of the IPv6 connectivity may take place on an IPv6 prefix basis.

• The indication that said connectivity (a PDU session) is eligible for Gateway

relocation optimization is received by SMF from the UE itself or from UDM (User subscription Database),

Various aspects and/or embodiments of the invention include (though not being limited to) following aspects and/or embodiments.

Some aspects are related to a mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions.

Various embodiments are provided, including (though not being limited to) following embodiments, which may be taken alone or in combination, according to various combinations. In an embodiment, said mobile network entity such as MME/SGSN or AMF is configured to:

- send to a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, a request to initiate the release of an established connectivity for a User Equipment UE when no service that breaks (or that makes user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

In an embodiment, said mobile network entity such as MME/SGSN or AMF is configured to:

- send said request upon detection of a need for Gateway relocation optimization, said Gateway relocation optimization including said initiation of release of said connectivity, by said network, when no sensitive service is on-going.

- send said request upon detection of a mobility event for said UE in a connected mode as seen from the core network.

In an embodiment, said mobile network entity such as MME/SGSN is configured to:

- send said request to said PGW in a GTP-c message, such as GTP-c Modify Bearer Request message.

In an embodiment, said mobile network entity is configured to:

- send to said mobile network entity such as PGW or SMF, such as at establishment of said connectivity, an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including said initiation of release of said connectivity, by said network, when no sensitive service is on-going.

Other aspects are related to a mobile network entity, such as PGW or SMF, providing Gateway control plane functions. Various embodiments are provided, including (though not being limited to) following embodiments, which may be taken alone or in combination, according to various combinations.

In an embodiment, said mobile network entity such as PGW or SMF is configured to:

- receive said request from a mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions.

In an embodiment, said mobile network entity such as PGW is configured to:

- receive said request from a mobile network entity such as MME/SGSN in a GTP-c message, such as GTP-c Modify Bearer Request message.

In an embodiment, said mobile network entity such as PGW or SMF is configured to perform at least one of, upon reception of said request:

- detect absence of on-going sensitive service on said connectivity, based on a list of sensitive services configured in said mobile network entity,

- initiate said connectivity release upon detection of absence of on-going sensitive service.

- inform a mobile network entity such as PCRF or PCF providing policy control functions, of said request,

- receive from said mobile network entity such as PCRF or PCF, a list of sensitive services to monitor, to detect absence of on-going sensitive service, - monitor the user plane traffic over said connectivity for detecting the absence of on-going sensitive service,

- inform a mobile network entity such as PCRF or PCF of a detected absence of on-going sensitive service,

- receive a request from said mobile network entity such as PCRF or PCF to release said connectivity.

- send to or via a mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions, a request to release said connectivity.

In an embodiment, said mobile network entity such as PGW is configured to:

- send to a mobile network entity such as MME/SGSN a GTP-c message such as Delete Bearer Request, to release said connectivity.

- receive from a mobile network entity, such as MME/SGSN, providing access and mobility management functions or from the User Equipment UE, an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including said initiation of release of said connectivity, by said network, when no sensitive service is on-going.

In an embodiment, said mobile network entity such as PGW or SMF is configured to perform at least one of, upon reception of said indication:

- inform a mobile network entity such as PCRF or PCF providing policy control functions of said indication, such as at establishment of a session with said mobile network entity such as PCRF or PCF,

- receive from said mobile network entity such as PCRF or PCF, a list of sensitive services to monitor, to detect absence of on-going sensitive service. Other aspects are related to a mobile network entity, such as PCRF or PCF, providing policy control functions.

Various embodiments are provided, including (though not being limited to) following embodiments, which may be taken alone or in combination, according to various combinations.

In an embodiment, said mobile network entity such as PCRF or PCF is configured to:

- - information about a request to initiate release an established connectivity for a User Equipment UE when no service, referred to as sensitive service, that breaks (or that makes user's experience unacceptable) at IP address change of the UE, is on-going on said established connectivity,

- - an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including said initiation of release of said connectivity, by said network, when no sensitive service is on-going.

In an embodiment, said mobile network entity such as PCRF or PCF is configured to perform at least one of, upon reception of said information about said request:

- send to said mobile network entity such as PGW or SMF, a list of sensitive services to monitor, to detect absence of on-going sensitive service,

- receive from said mobile network entity such as PGW or SMF, an information of a detected absence of on-going sensitive service,

- send to said mobile network entity such as PGW or SMF, a request to release said connectivity.

In an embodiment, said mobile network entity such as PCRF or PCF is configured to perform at least one of, upon reception of said information about said request: - send to a mobile network entity such as TDF providing traffic detection functions, a list of sensitive services to monitor, to detect absence of on-going sensitive service,

- receive from said mobile network entity such as TDF, an information of a detected absence of on-going sensitive service,

- receive said indication from said mobile network entity such as PGW or

SMF, such as at establishment of a session with said mobile network entity such as PGW or SMF.

- upon reception of said indication, send to said mobile network entity such as PGW or SMF, a list of sensitive services to monitor, to detect absence of on-going sensitive service.

Other aspects are related to a mobile network entity, such as TDF, providing traffic detection functions.

Various embodiments are provided, which may be taken alone or in combination, according to various combinations, including (though not being limited to) following embodiment.

In an embodiment, said mobile network entity such as TDF is configured to perform at least one of:

Equipment UE, referred to as sensitive service, on an established connectivity, - monitor the user plane traffic over said connectivity for detecting the absence of on-going sensitive service,

Other aspects are related to a User Equipment UE.

In an embodiment, said UE is configured to:

- send towards a mobile network entity, such as SMF providing session management functions, such as at establishment of a connectivity for said UE, an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including initiation of release of said connectivity, by said network, when no service that breaks (or that would user's experience unacceptable) at IP address change of the UE, referred to as sensitive service, is ongoing on said established connectivity.

Other aspects are related to a method for optimization of Gateway relocation in a mobile system, said method including at least one step performed by at least one of the thus configured entities including (although not limited to) : a mobile network entity such as MME/SGSN or AMF, a mobile network entity such as PGW or SMF, a mobile network entity such as PCRF or PCF, a mobile network entity such as TDF, a User Equipment UE.

A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine- executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.

Claims

1. A mobile network entity, such as MME/SGSN or AMF, providing access and mobility management functions, said mobile network entity configured to:

- send to a mobile network entity, such as PGW or SMF, providing Gateway control plane functions, a request to initiate the release of an established connectivity for a User Equipment UE when no service that breaks at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

2. A mobile network entity according to claim 1, configured to:

3. A mobile network entity according to claim 1 or 2, configured to:

4. A mobile network entity such as MME/SGSN according to any of claims 1 to 3, configured to:

5. A mobile network entity according to any of claims 1 to 4, configured to:

6. A mobile network entity, such as PGW or SMF, providing Gateway control plane functions, configured to:

- receive a request or detect the need to initiate the release of an established connectivity for a User Equipment UE when no service that breaks at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

7. A mobile network entity according to claim 6, configured to:

8. A mobile network entity such as PGW according to claim 6 or 7, configured to:

9. A mobile network entity according to any of claims 6 to 8, configured to perform at least one of, upon reception of said request:

10. A mobile network entity according to any of claims 6 to 9, configured to perform at least one of, upon reception of said request:

11. A mobile network entity according to any of claims 6 to 10, configured to:

12. A mobile network entity such as PGW according to any of claims 6 to 11, configured to:

13. A mobile network entity according to any of claims 6 to 12, configured to:

14. A mobile network entity according to claim 13, configured to perform at least one of, upon reception of said indication: - inform a mobile network entity such as PCRF or PCF providing policy control functions of said indication, such as at establishment of a session with said mobile network entity such as PCRF or PCF,

- receive from said mobile network entity such as PCRF or PCF, a list of sensitive services to monitor, to detect absence of on-going sensitive service.

15. A mobile network entity such as PCRF or PCF providing policy control functions, configured to:

- - information about a request to initiate release an established connectivity for a User Equipment UE when no service, referred to as sensitive service, that breaks at IP address change of the UE, is on-going on said established connectivity,

16. A mobile network entity according to claim 15, configured to perform at least one of, upon reception of said information about said request:

17. A mobile network entity according to claim 15, configured to perform at least one of, upon reception of said information about said request: - send to a mobile network entity such as TDF providing traffic detection functions, a list of sensitive services to monitor, to detect absence of on-going sensitive service,

18. A mobile network entity according to any of claims 15 to 17, configured to:

- receive said indication from said mobile network entity such as PGW or SMF, such as at establishment of a session with said mobile network entity such as PGW or SMF.

19. A mobile network entity according to any of claims 15 to 18, configured to:

20. A mobile network entity such as TDF providing traffic detection functions, configured to:

- receive from a mobile network entity such as PCRF providing policy control functions, a request to detect absence of on-going service that breaks at IP address change of a User Equipment UE, referred to as sensitive service, on an established connectivity,

21. A User Equipment, UE, configured to:

- send towards a mobile network entity such as SMF providing session management functions, such as at establishment of a connectivity for said UE, an indication that said connectivity is eligible for Gateway relocation optimization, said Gateway relocation optimization including initiation of release of said connectivity, by said network, when no service that breaks at IP address change of the UE, referred to as sensitive service, is on-going on said established connectivity.

22. A method for optimization of Gateway relocation in a mobile system, said method including at least one step performed by at least one of: a mobile network entity such as MME/SGSN or AMF, according to any of claims 1 to 5, a mobile network entity such as PGW or SMF according to any of claims 6 to 14, a mobile network entity such as PCRF or PCF according to any of claims 15 to 19, a mobile network entity such as TDF according to claim 20, a User Equipment UE according to claim 21.