Patent Publication Number: US-2023164534-A1

Title: Service-Based User Plane Entity for a Wireless Communication Network

Description:
TECHNICAL FIELD 
     The present invention relates to methods for enabling and operating a service-based user plane entity for a wireless communication network and to corresponding network entities. 
     BACKGROUND 
       FIG.  1   a    shows a 5G New Radio, NR, architecture with service based interfaces.  FIG.  1   b    shows the 5GC architecture for policy, charging and analytics. Service Based Interfaces are represented in the format Nxyz, such as Nsmf, and point to point interfaces in the format Nx, such as N4. 
     The 5G core network  100  part comprises a Network Slice Selection Function, NSSF,  101 , a Network Exposure Function, NEF,  102 , a Network Repository Function, NRF,  103 , a Policy Control Function, PCF,  104 , a Unified Data Management, UDM,  106 , an Application Function, AF,  106 , an Authentication Server Function, AUSF,  107 , an Access and Mobility Management Function, AMF,  108 , and a Session Management Function, SMF,  109 . Having service based interfaces in the 5G Core Control Plane, CP, implies that the Network Functions, NFs, in the 5G Core CP provide services that are consumed by other NFs in the 5G Core CP. 
     A User Equipment, UE,  110 , is connected to the Radio Access Network, RAN,  111 , wherein a User Plane Function, UPF,  112  is provided to connect the UE  110  to a Data Network, DN,  113 . 
     The roles of these entities and the interfaces between them are defined, for instance, in the 3GPP TS 23.501 and the procedures are described, for instance, in 3GPP TS 23.502. 
     Relevant 5G System Architecture network aspects and functions for this invention are the following:
         Network Exposure Function, NEF,  102  generally is the entry point for Application Service Providers, ASPs, to the Mobile Network Operator Network a.k.a. Connectivity Service Provider, CSP. NEF  102  generally exposes the Connectivity Service Provider Mobile Network capabilities to the ASPs and translates between information as known by the external Application Functions, AFs, and information as known by the Mobile Network Function/s;   Policy Control Function, PCF,  104 , generally supports unified policy framework to govern the network behaviour. In particular, PCF  104  generally provides Policy and Charging Control, PCC, rules to the Policy and Charging Enforcement Function, PCEF, that is, SMF  109 /UPF  112  that enforces policy and charging decisions according to provisioned PCC rules;   Unified Data Management/Repository, UDM,  105 , and UDR, not illustrated. The UDM generally manages network user data in a single, centralized element and can be paired with the UDR, which generally stores user data such as customer profile information, customer authentication information, encryption keys, etc;   Application Function, AF,  106 , generally interacts with the 3GPP Core Network so as to provide information that will allow network operator to manage application&#39;s traffic in a certain way;   Session Management Function, SMF,  109  is generally responsible for Session establishment, modification and release, including selection and control of the UPF  112  entities. In the known art, SMF  109  interacts with the UPF  112  over N4 Reference point using Packet Flow Central Protocol, PFCP, procedures. Moreover, SMF  109  generally receives PCC rules from PCF  104  and configures the UPF  112  accordingly;   User Plane Function, UPF,  112 , generally supports handling of user plane traffic based on the rules received from SMF  109 , in particular packet inspection and different enforcement actions, such as QoS, Charging, etc.;   Control Plane and User Plane separation, CUPS, in particular between Session Management Function, SMF,  109  and User Plane Function, UPF,  112 , which is further explained below;   Network Data Analytics Function, NWDAF,  114 , is generally used for data collection and data analytics in centralized manner;   Binding Support Function, BSF, not shown in  FIGS.  1   a  and  1   b   , is generally used to find the PCF  104  in charge of the user Packet Data Unit, PDU, connection policy session in scenarios with more than one PCF  104 .       

     In the Packet Core of the 4G System Architecture:
         SCEF (Service Capability Exposure Function) generally plays the role of NEF  102  above, at least for the APIs (Application Programming Interfaces) listed above which are supported also in 4G;   PCRF (Policy and Charging Rules Function) generally plays the role of the PCF  104  above;   network&#39;s Home Subscriber Service, HSS, generally plays the role of UDM  105  above;   SCS/AF (Service Capability Server/Application Function) generally plays the role of AF  106  above;   PGW-C(Control plane of the Packet Data Network Gateway) and/or TDF-C(Control plane of the Traffic Detection Function) generally plays the role of the SMF  109  above;   PGW PGW-U (User plane of the Packet Data Network Gateway) and/or TDF-U (User plane of the Traffic Detection Function) generally plays the role of the UPF  112  above.       

     In the following, Mobile Core will refer to any, the 5G Core or the Packet Core of the 4G System Architecture. Furthermore, CP will refer to any SMF or PGW-C, and UP to any, UPF or PGW-U. 
     Prior to 3GPP Rel-15, the functional distribution within the core network  100  was based on Network Elements exchanging messages over point to point interfaces. With Rel-15 5G, to facilitate cloud native implementations and deployments, a service-based architecture has been introduced, based on the concept of Network Functions, NF, offering and consuming NF Services over Service Based Interfaces. A service-based Network Function, NF, interaction with other network functions can be generally comprising:
         a NF registering in the Network Repository Function, NRF,  103  the list of supported NF services;   other network functions, NFs, can discover the NF services using NRF  103  and selecting a specific instance of the NF;   the network functions NFs consuming NF services of the selected NF instance.       

     Even after Rel-15 5G, some of the interfaces have been kept as point to point interfaces. This is the case, for instance, of the N4 interface between the Session Management Function, SMF,  109  and the User Plane Function, UPF,  112 . 
     In particular, those two entities belong respectively to the Control Plane, CP, and to the User Plane, UP, of the 5G architecture. Control and user plane separation, CUPS, enables a flexible placement of the separated Control Plane and User Plane functions, for supporting diverse deployment scenarios, for instance central or distributed User Plane function. 
     In 5G, CUPS relates to SMF  109  and UPF  112  network functions and to the N4 reference point between them, which is based on Packet Forwarding Control Protocol PFCP. The SMF  109  generally controls the packet processing in the UPF  112  by establishing, modifying or deleting PFCP Session contexts and by provisioning, for instance adding, modifying or deleting, PDRs, FARs, QERs, URRs and/or BAR per PFCP session context, whereby an PFCP session context may correspond to an individual PDU session or a standalone PFCP session not tied to any PDU session. Each PDR can contain a PDI, that is, one or more match fields against which incoming packets are matched, and may be associated to the following rules providing the set of instructions to apply to packets matching the PDI:
         one FAR, which contains instructions related to the processing of the packets, specifically forward, duplicate, drop or buffer the packet with or without notifying the CP function about the arrival of a DL packet. Each FAR includes what forwarding policies to follow when it comes to N6 traffic steering, e.g. what Service Chain (sequence of Service Functions) is to be applied to the packets;   zero, one or more QERs, which contains instructions related to the QoS enforcement of the traffic;   zero, one or more URRs, which contains instructions related to traffic measurement and reporting.       

     In CUPS, UPF  112  reports to SMF  109  the capabilities it supports. The current standardized capabilities are: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Feature 
                   
                   
                   
               
               
                 Octet/ 
               
               
                 Bit 
                 Feature 
                 Interface 
                 Description 
               
               
                   
               
             
            
               
                 5/1 
                 BUCP 
                 Sxa 
                 Downlink Data Buffering in CP function 
               
               
                   
                   
                   
                 is supported by the UP function. 
               
               
                 5/2 
                 DDND 
                 Sxa 
                 The buffering parameter ‘Downlink Data 
               
               
                   
                   
                   
                 Notification Delay’ is supported by the UP 
               
               
                   
                   
                   
                 function. 
               
               
                 5/3 
                 DLBD 
                 Sxa 
                 The buffering parameter ‘DL Buffering 
               
               
                   
                   
                   
                 Duration’ is supported by the UP function. 
               
               
                 5/4 
                 TRST 
                 Sxb, Sxc 
                 Traffic Steering is supported by the UP 
               
               
                   
                   
                   
                 function. 
               
               
                 5/5 
                 FTUP 
                 Sxa, Sxb 
                 F-TEID allocation/release in the UP 
               
               
                   
                   
                   
                 function is supported by the UP function. 
               
               
                 5/6 
                 PFDM 
                 Sxb, Sxc 
                 The PFD Management procedure is 
               
               
                   
                   
                   
                 supported by the UP function. 
               
               
                 5/7 
                 HEEU 
                 Sxb, Sxc 
                 Header Enrichment of Uplink traffic is 
               
               
                   
                   
                   
                 supported by the UP function. 
               
               
                 5/8 
                 TREU 
                 Sxb, Sxc 
                 Traffic Redirection Enforcement in the UP 
               
               
                   
                   
                   
                 function is supported by the UP function. 
               
               
                 6/1 
                 EMPU 
                 Sxa, Sxb 
                 Sending of End Marker packets supported 
               
               
                   
                   
                   
                 by the UP function. 
               
               
                 6/2 
                 PDIU 
                 Sxa, Sxb, 
                 Support of PDI optimised signalling in UP 
               
               
                   
                   
                 Sxc, N4 
                 function (see subclause 5.2.1A.2). 
               
               
                   
               
            
           
         
       
     
     3GPP specifications 23.501, lists in clause 6.2.3 the functionality included in the UPF  112 , but also open the some or all of UPF functionalities to be supported in a single instance of a UPF or distributed over multiple UPF instances. 
     In particular, several examples of such multiple UPF instances are described in TS 23.501. For example, to ensure connectivity between a RAN node  111  and the anchor UPF  112 , an intermediate I-UPF,  112 , as illustrated for instance in  FIG.  1   c   , was introduced. The I-UPF  112  is a UPF only executing one Packet Detection Rule, PDR, and one Forwarding Action Rules, FAR. Alternatively, or in addition, as illustrated for instance in  FIG.  1   d   , in order to support the distribution of the point of interconnect to Data Network for data flows with special requirement, for instance low latency connectivity, an Uplink classifier UPF  112  may be combined with several PDU Session Anchor UPFs  112 . 
     Thus, depending on the use case, there is a need of selecting and chain UPFs  112  with different capabilities so as to realize the connectivity service. 
     3GPP recently launched the “Study on User Plane Function (UPF) enhancement for control and 5G Service Based Architecture (SBA)”, which aims to study the evolution of the UPF  112  as a service-based Network Function integrated with the CP NFs through a Service Based Interface, SBI. 
     Such service-based approach for the UPF  112  introduces a variety of issues, considering the various uses and configurations of the UPF, as described above. 
     In general, a service-based UPF would need to register in NRF the exposed services, in line with Service Based Architecture, SBA, principles. A service-based UPF would expose independent services to be consumed by the other CP NFs. This contrast with today&#39;s solution, which is a point-to-point, P2P, interface with the SMF based on the PFCP protocol. This results in several unsolved problems when it comes to the support of a service-based UPF in the current 5GC network. 
     In particular, in the current PFCP-based approach, the association between UPF and SMF is simple, thanks to the presence of the point-to-point, P2P, N4 interface. When introducing a service-based UPF, it is not known how to associate UPFs and SMFs following SBA principles, that is how to manage the association service in the UPF and/or in the SMF. Moreover, in the presence of various UPF and/or SMF, it is not known how to select the UPF/SMF to associate to. 
     Moreover, in the current PFCP-based approach, the UPF discovery and selection by SMF can be done on a per PDU session basis. When introducing a service-based UPF, it is not known how the SMF can perform service selection on a per PDU session basis. In particular, it is not known what parameters can be considered by the SMF to select the UPF services on a per PDU session basis. It is also not known in what UPFs to do so, for instance considering required capabilities/features coming from PCF, location coming from AMF, UPF location, etc. 
     Still further, in the current PFCP-based approach, the service chaining functionality can be done in the UPF. When introducing a service-based UPF, it is not known how to configure several services for a given traffic payload chained in a certain order, both within a single UPF and across several UPFs. 
     Still additionally, a service-based UPF also poses a problem for UPF services usage by other CP NFs. In particular, it is not known how to find the UPF services associated to a certain user. Still further, it is not known how to request services from the consumer. 
     SUMMARY 
     Accordingly, there is a need for techniques which allow for enabling a service-based UPF implementation. This need is met by the features of the independent claims. Further aspects are described in the dependent claims. 
     According to one aspect, a method for operating a user plane entity in a wireless communication network is provided, the wireless communication network comprising the user plane entity, a plurality of session control entities and a network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the method comprising the steps of:
         transmitting to the network repository entity a discovery message comprising:
           an association request indication, for indicating that the user plane entity can be associated to a session control entity,   filtering criteria for filtering the plurality of session control entities,   
           receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered session control entities, filtered based on the filtering criteria,   
           transmitting to a first filtered session control entity, of the filtered session control entities, an association request message comprising:
           an identifier of the user plane entity.   
               

     Another aspect furthermore relates to a user plane entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the user plane entity. 
     According to another aspect, a user plane entity for a wireless communication network is provided, the wireless communication network comprising the user plane entity, a plurality of session control entities and a network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the user plane entity comprising:
         a module for transmitting to the network repository entity a discovery message comprising:
           an association request indication, for indicating that the user plane entity can be associated to a session control entity,   filtering criteria for filtering the plurality of session control entities,   
           a module for receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered session control entities, filtered based on the filtering criteria,   
           a module for transmitting to a first filtered session control entity, of the filtered session control entities, an association request message comprising:
           an identifier of the user plane entity.   
               

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a plurality of session control entities and a network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the method comprising the steps of:
         transmitting to the network repository entity a registration message comprising:
           an association service indication, for indicating that the session control entity can be associated to a user plane entity,   an area indication of the session control entity,   
           receiving from the user plane entity an association request message comprising:
           an identifier of the user plane entity.   
               

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a plurality of session control entities and a network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the session control entity comprising:
         a module for transmitting to the network repository entity a registration message comprising:
           an association service indication, for indicating that the session control entity can be associated to a user plane entity,   an area indication of the session control entity,   
           a module for receiving from the user plane entity an association request message comprising:
           an identifier of the user plane entity.   
               

     According to another aspect, a method for operating a network repository entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a plurality of session control entities and the network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the method comprising the steps of:
         receiving from at least one of the plurality of session control entities a registration message comprising:
           an association service indication, for indicating that the at least one session control entity can be associated to a user plane entity,   an area indication of the at least one session control entity,   
           receiving from the user plane entity a discovery message comprising:
           an association request indication, indicating that the user plane entity can be associated to a session control entities,   filtering criteria for filtering the plurality of session control entities,   
           transmitting to the user plane entity a response message, in response to the discovery message, comprising:
           a list of filtered session control entities, filtered based on the filtering criteria.   
               

     Another aspect furthermore relates to a network repository entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the network repository entity. 
     According to another aspect, a network repository entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a plurality of session control entities and the network repository entity,
         the plurality of session control entities being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the network repository entity comprising:
         a module for receiving from at least one of the plurality of session control entities a registration message comprising:
           an association service indication, for indicating that the at least one session control entity can be associated to a user plane entity,   an area indication of the at least one session control entity,   
           a module for receiving from the user plane entity a discovery message comprising:
           an association request indication, indicating that the user plane entity can be associated to a session control entities,   filtering criteria for filtering the plurality of session control entities,   
           a module for transmitting to the user plane entity a response message, in response to the discovery message, comprising:
           a list of filtered session control entities, filtered based on the filtering criteria.   
               

     According to another aspect, a method for operating a user plane entity in a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, a session control entity and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the method comprising the steps of:
         transmitting to the network repository entity a registration message comprising:
           an association service indication, for indicating that the user plane entity can be associated to a session control entity,   
           receiving from the session control entity an association request message comprising:
           an identifier of the session control entity,   
           transmitting to the session control entity an association confirmation message, in response to the association request message.       

     Another aspect furthermore relates to a user plane entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the user plane entity. 
     According to another aspect, a user plane entity for a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, a session control entity and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the user plane entity comprising:
         a module for transmitting to the network repository entity a registration message comprising:
           an association service indication, for indicating that the user plane entity can be associated to a session control entity,   
           a module for receiving from the session control entity an association request message comprising:
           an identifier of the session control entity,   
           a module for transmitting to the session control entity an association confirmation message, in response to the association request message.       

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, the session control entity and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the method comprising the steps of:
         transmitting to the network repository entity a discovery message comprising:
           an association request indication, for indicating that the session control entity can be associated to a user plane entity,   filtering criteria for filtering the plurality of user plane entities,   
           receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria,   
           transmitting to a first filtered user plane entity, of the filtered user plane entities, an association request message comprising:
           an identifier of the session control entity.   
               

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, the session control entity and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the session control entity comprising:
         a module for transmitting to the network repository entity a discovery message comprising:
           an association request indication, for indicating that the session control entity can be associated to a user plane entity,   filtering criteria for filtering the plurality of user plane entities,   
           a module for receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria,   
           a module for transmitting to a first filtered user plane entity, of the filtered user plane entities, an association request message comprising:
           an identifier of the session control entity.   
               

     According to another aspect, a method for operating a network repository entity in a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, a session control entity and the network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the method comprising the steps of:
         receiving from at least one of the user plane entities a registration message comprising:
           an association service indication, for indicating that the at least one user plane entity can be associated to a session control entity,   
           receiving from the session control entity a discovery message comprising:
           an association request indication, for indicating that the session control entity can be associated to a user plane entity,   filtering criteria for filtering the plurality of user plane entities,   
           transmitting to the session control entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria.   
               

     Another aspect furthermore relates to a network repository entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the network repository entity. 
     According to another aspect, a network repository entity for a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, a session control entity and the network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the network repository entity being configured to register the session control entity and the plurality of user plane entities,       

     the network repository entity comprising:
         a module for receiving from at least one of the user plane entities a registration message comprising:
           an association service indication, for indicating that the at least one user plane entity can be associated to a session control entity,   
           a module for receiving from the session control entity a discovery message comprising:
           an association request indication, for indicating that the session control entity can be associated to a user plane entity,   filtering criteria for filtering the plurality of user plane entities,   
           a module for transmitting to the session control entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria.   
               

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, the session control entity, a policy control entity, and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the policy control entity being configured to handle a policy plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the method comprising the steps of:
         receiving from the policy control entity a policy activation message comprising:
           a list of services to be activated in the plurality of user plane entities,   
           transmitting to the network repository entity a discovery message comprising:
           filtering criteria for filtering the plurality of user plane entities,   
           receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria.   
               

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a plurality of user plane entities, the session control entity, a policy control entity, and a network repository entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the plurality of user plane entities being configured to handle a user plane of the at least one data packet session,   the policy control entity being configured to handle a policy plane of the at least one data packet session,   the network repository entity being configured to register the plurality of session control entities and the user plane entity,       

     the session control entity comprising:
         a module for receiving from the policy control entity a policy activation message comprising:
           a list of services to be activated in the plurality of user plane entities,   
           a module for transmitting to the network repository entity a discovery message comprising:
           filtering criteria for filtering the plurality of user plane entities,   
           a module for receiving from the network repository entity a response message, in response to the discovery message, comprising:
           a list of filtered user plane entities, filtered based on the filtering criteria.   
               

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         receiving from the wireless communication network entity a service discovery message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           transmitting to the wireless communication network entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the session control entity comprising:
         a module for receiving from the wireless communication network entity a service discovery message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           a module for transmitting to the wireless communication network entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     According to another aspect, a method for operating a wireless communication network entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         transmitting to the session control entity a service discovery message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           receiving from the session control entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     Another aspect furthermore relates to a wireless communication network entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the wireless communication network entity. 
     According to another aspect, a wireless communication network entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the wireless communication network entity comprising:
         a module for transmitting to the session control entity a service discovery message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           a module for receiving from the session control entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     According to another aspect, a method for operating a user repository entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, the user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         receiving from the session control entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           receiving from the wireless communication network entity a service discovery message comprising:
           the identifier of the user of the wireless communication network,   
           transmitting to the wireless communication network entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     Another aspect furthermore relates to a user repository entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the user repository entity. 
     According to another aspect, a user repository entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, the user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the user repository entity comprising:
         a module for receiving from the session control entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           a module for receiving from the wireless communication network entity a service discovery message comprising:
           the identifier of the user of the wireless communication network,   
           a module for transmitting to the wireless communication network entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         selecting services provided by the user plane entity;   transmitting to the user repository entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network.   
               

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the session control entity comprising:
         a module for selecting services provided by the user plane entity;   a module for transmitting to the user repository entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network.   
               

     According to another aspect, a method for operating a wireless communication network entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         transmitting to the user repository entity a service discovery message comprising:
           an identifier of a user of the wireless communication network,   
           receiving from the user repository entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     Another aspect furthermore relates to a wireless communication network entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the wireless communication network entity. 
     According to another aspect, a wireless communication network entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the wireless communication network entity comprising:
         a module for transmitting to the user repository entity a service discovery message comprising:
           an identifier of a user of the wireless communication network,   
           a module for receiving from the user repository entity a response message, in response to the service discovery message, comprising:
           an address of the user plane entity.   
               

     According to another aspect, a method for operating a session control entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         receiving from the wireless communication network entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           transmitting to the user plane entity a subscription message, in response to the service registration message, for subscribing the wireless communication network entity to the service indicated by the service indication.       

     Another aspect furthermore relates to a session control entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the session control entity. 
     According to another aspect, a session control entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, the session control entity, a user repository entity, and a wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the session control entity comprising:
         a module for receiving from the wireless communication network entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   an identifier of a user of the wireless communication network,   
           a module for transmitting to the user plane entity a subscription message, in response to the service registration message, for subscribing the wireless communication network entity to the service indicated by the service indication.       

     According to another aspect, a method for operating a wireless communication network entity in a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the method comprising the steps of:
         transmitting to the user repository entity a session control discovery message, comprising:
           an identifier of a user of the wireless communication network,   
           receiving from the user repository entity a session control indication message, in response to the session control discovery message, comprising:
           the address of the session control entity,   
           transmitting to the session control entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   the identifier of the user of the wireless communication network.   
               

     Another aspect furthermore relates to a wireless communication network entity for a wireless communication network comprising a processing unit and a memory, the memory comprising instructions configured to cause the processing unit to carry out the steps described above for the method for operating the wireless communication network entity. 
     According to another aspect, a wireless communication network entity for a wireless communication network is provided, the wireless communication network comprising a user plane entity, a session control entity, a user repository entity, and the wireless communication network entity,
         the session control entity being configured to handle at least one data packet session in the wireless communication network,   the user plane entity being configured to handle a user plane of the at least one data packet session,   the user repository entity being configured to register subscriber information for users of the wireless communication network,   the wireless communication network entity being an entity of the wireless communication network accessing services of at least the user plane entity,       

     the wireless communication network entity comprising:
         a module for transmitting to the user repository entity a session control discovery message, comprising:
           an identifier of a user of the wireless communication network,   
           a module for receiving from the user repository entity a session control indication message, in response to the session control discovery message, comprising:
           the address of the session control entity,   
           a module for transmitting to the session control entity a service registration message comprising:
           a service indication, for indicating a service provided by the user plane entity,   the identifier of the user of the wireless communication network.   
               

     It is to be understood that the features mentioned above and features yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the present invention. Features of the above-mentioned aspects and embodiments described below may be combined with each other in other embodiments unless explicitly mentioned otherwise. 
     Other devices, systems, methods, features and advantages will be or will become apparent to one with skill in the art upon examination of the following detailed description and figures. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention and be protected by the following claims. 
    
    
     
       DETAILED DESCRIPTION OF DRAWINGS 
       Various features of embodiments will become more apparent when read in conjunction with the accompanying drawings. In these drawings: 
         FIG.  1   a    schematically illustrates the 5G NR reference architecture as currently defined by 3GPP; 
         FIG.  1   b    schematically illustrates 5GC architecture for policy, charging and analytics; 
         FIG.  1   c    schematically illustrates an implementation including an intermediate I-UPF between a RAN node and the anchor UPF; 
         FIG.  1   d    schematically illustrates an implementation including an Uplink classifier UPF  112 , combined with several PDU Session Anchor UPFs  112 ; 
         FIG.  2    shows an example flowchart of a method for operating entities of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  2   a    shows an example flowchart of a method for operating a user plane entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  2   b    shows an example flowchart of a method for operating a session control entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  2   c    shows an example flowchart of a method for operating a network repository entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  3    shows an example flowchart of a method for operating entities of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  3   a    shows an example flowchart of a method for operating a user plane entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  3   b    shows an example flowchart of a method for operating a session control entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  3   c    shows an example flowchart of a method for operating a network repository entity of a wireless communication network for associating a service-based user plane entity and a session control entity; 
         FIG.  4    shows an example flowchart of a method for operating entities of a wireless communication network for establishing a PDU session; 
         FIG.  4   a    shows an example flowchart of a method for operating a session control entity of a wireless communication network for establishing a PDU session; 
         FIG.  5    shows an example flowchart of a method for operating entities of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  5   a    shows an example flowchart of a method for operating a session control entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  5   b    shows an example flowchart of a method for operating a wireless communication network entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  6    shows an example flowchart of a method for operating entities of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  6   a    shows an example flowchart of a method for operating a user repository entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  6   b    shows an example flowchart of a method for operating a session control entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  6   c    shows an example flowchart of a method for operating a wireless communication network entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  7    shows an example flowchart of a method for operating entities of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  7   a    shows an example flowchart of a method for operating a session control entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  7   b    shows an example flowchart of a method for operating a wireless communication network entity of a wireless communication network for accessing services of a service-based user plane entity; 
         FIG.  8    shows an example schematic of various entities of a wireless communication network allowing implementation of a service-based user plane entity; 
         FIG.  9   a    shows an example user plane entity of a wireless communication network; 
         FIG.  9   b    shows an example session control entity of a wireless communication network; 
         FIG.  9   c    shows an example network repository entity of a wireless communication network; 
         FIG.  10   a    shows an example user plane entity of a wireless communication network; 
         FIG.  10   b    shows an example session control entity of a wireless communication network; 
         FIG.  10   c    shows an example network repository entity of a wireless communication network; 
         FIG.  11   a    shows an example session control entity of a wireless communication network; 
         FIG.  12   a    shows an example session control entity of a wireless communication network; 
         FIG.  12   b    shows an example wireless communication network entity of a wireless communication network; 
         FIG.  13   a    shows an example user repository entity of a wireless communication network; 
         FIG.  13   b    shows an example session control entity of a wireless communication network; 
         FIG.  13   c    shows an example wireless communication network entity of a wireless communication network; 
         FIG.  14   a    shows an example session control entity of a wireless communication network; 
         FIG.  14   b    shows an example wireless communication network entity of a wireless communication network; 
         FIG.  15    shows an example session control entity of a wireless communication network; 
         FIG.  16    shows an example network repository entity of a wireless communication network; 
         FIG.  17    shows an example session control entity of a wireless communication network; 
         FIG.  18    shows an example network repository entity of a wireless communication network; 
         FIG.  19    shows an example session control entity of a wireless communication network; 
         FIG.  20    shows an example wireless communication network entity of a wireless communication network; 
         FIG.  21    shows an example session control entity of a wireless communication network; 
         FIG.  22    shows an example wireless communication network entity of a wireless communication network. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of embodiments is not to be taken in a limiting sense. The scope of the invention is not intended to be limited by the embodiments described hereinafter or by the drawings, which are to be illustrative only. 
     The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose becomes apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components of physical or functional units shown in the drawings and described hereinafter may also be implemented by an indirect connection or coupling. A coupling between components may be established over a wired or wireless connection. Functional blocks may be implemented in hardware, software, firmware, or a combination thereof. 
     Within the context of the present application, the term “mobile entity” or “user equipment” (UE)  110  refers to a device for instance used by a person (i.e. a user) for his or her personal communication. It can be a telephone type of device, for example a telephone or a Session Initiating Protocol (SIP) or Voice over IP (VoIP) phone, cellular telephone, a mobile station, cordless phone, or a personal digital assistant type of device like laptop, notebook, notepad, tablet equipped with a wireless data connection. The UE may also be associated with non-humans like animals, plants, or machines. A UE may be equipped with a SIM (Subscriber Identity Module) or electronic-SIM comprising unique identities such as IMSI (International Mobile Subscriber Identity), TMSI (Temporary Mobile Subscriber Identity), or GUTI (Globally Unique Temporary UE Identity) associated with the user using the UE. The presence of a SIM within a UE customizes the UE uniquely with a subscription of the user. The wireless communication network is generally any communication network which allows a wireless communications with the user equipment  110 . In some embodiments, the wireless communication network can be an LTE network or a 5G NR network. 
       FIG.  2    shows an example flowchart of a method for operating a user plane entity  21 , a session control entity  22  and a network repository entity  23  in a wireless communication network. In particular the method allows the association of a service-based user plane entity  21  with a session control entity  22 . In the embodiments of  FIG.  2   , the association is generally triggered by the user plane entity  21 . 
     The method generally allows the association between the user plane entity  21  and the session control entity  22 . The association can then be used to exchange node level messages, including the exchange of Node Capabilities. Moreover, the association can allow initiating node level operation, for instance if a user plane entity  21  is being decommissioned, it may request the session control entity  22  to terminate all its PDU sessions. 
       FIG.  2    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  2    will be described first. 
     At step S 2 - 1  the user plane entity can  21  generally register itself with network repository entity  23 . In some embodiments the registration can also include registering the list of supported capabilities of the user plane entity  21 . That is, the message sent at step S 2 - 1  can also comprise a list of capabilities of the user plane entity  21 , for instance capabilities which can be accessed by other entities in the wireless communication network. 
     At step S 2 - 2 , the session control entity  22  can generally register itself with network repository entity  23 . The details of the message sent at step S 2 - 2  will be described in the following. In general, in some embodiments, the message sent at step S 2 - 2  can provide an indication that the session control entity  22  supports an association service, and/or an area indication of the session control entity  22 . 
     Thanks to S 2 - 1  and S 2 - 2 , both the user plane entity  21  and the session control entity  22  can thus be registered with the network repository entity  23 . Moreover, the information concerning the association service offered by the session control entity  22  can be accessed at the network repository entity  23 , for an association between the user plane entity  21  and the session control entity  22 . 
     At step S 2 - 3 , the user plane entity  21  can generally send to network repository entity  23  a discovery request allowing the identification of one or more session control entity  22 , to which the user plane entity  21  can associate to. The details of the message sent at step S 2 - 3  will be described in the following. 
     At step S 2 - 4 , the network repository entity  23  can generally respond with one or more selected session control entity  22 , based on the indications provided at step S 2 - 3 . The details of the message sent at step S 2 - 4  will be described in the following. 
     Thanks to S 2 - 3  and S 2 - 4  the user plane entity  21  can thus be provided with one or more session control entity  22  to which the user plane entity  21  can associate to. 
     At step S 2 - 5 , the user plane entity  21  can generally send a message to a session control entity  22  for carrying out the association. The details of the message sent at step S 2 - 5  will be described in the following. 
     In general it will be understood that at step S 2 - 5  the user plane entity  21  could also send, together with the association message, a list of its capabilities. This could be particularly advantageous, for instance, if the list of capabilities of the user plane entity  21  was not transmitted to the network repository entity  23  at step S 2 - 1 . Moreover, even if the list of capabilities were transmitted to the network repository entity  23  at step S 2 - 1 , by transmitting it directly to the session control entity  22  at step S 2 - 5 , the session control entity  22  could be provided with the list of capabilities in a faster manner, during the association. Still further, this allows the possibility of sending different capabilities in steps S 2 - 1  and S 2 - 5 . 
     In those embodiments in which the list of capabilities is not sent at step S 2 - 5 , optional step S 2 - 6  can generally allow the session control entity  22  to request those capabilities to the network repository entity  23 , while optional step S 2 - 7  can generally allow the session control entity  22  to receive the requested list of capabilities from the network repository entity  23 . The details of the messages sent at steps S 2 - 6  and S 2 - 7  will be described in the following. 
     At step S 2 - 8 , the session control entity  22  can generally respond acknowledging the association with the user plane entity  21 . 
     Thanks to this approach it is possible for the user plane entity  21  and the session control entity  22  to be associated with each other and for the session control entity  22  to make use of the capabilities, or services, offered by the user plane entity  21 , in a manner compatible with a service-based user plane entity  21 . 
     In the following specific embodiments relating to the method described with reference to  FIG.  2    will be described in details. It will be understood that, as described in the following, not all steps illustrated in  FIG.  2    are necessary for the implementation of every embodiment. 
     In particular, as illustrated for instance in  FIG.  2   a   , an embodiment of the invention can relate to a method for operating a user plane entity  21  in a wireless communication network. The wireless communication network can comprise the user plane entity  21 , a plurality of session control entities  22  and a network repository entity  23 . 
     The plurality of session control entities  22  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  21  can be configured to handle a user plane of the at least one data packet session. The network repository entity  23  can be configured to register the plurality of session control entities  22  and the user plane entity  21 . 
     The method can comprise a step S 2 - 3  of transmitting to the network repository entity  23  a discovery message comprising:
         an association request indication, for indicating that the user plane entity  21  can be associated to a session control entity  22 ,   filtering criteria for filtering the plurality of session control entities  22 .       

     In some embodiments, the filtering criteria can comprise one or more of:
         an area of the session control entity  22 ;   an identifier of the user plane entity  21 ;   an identifier of a slice of the wireless communication network, for instance, in particular within a 5G implementation, a Network Slice Instance, NSI ID;   a location of the user plane entity  21 .       

     The method can further comprise a step S 2 - 4  of receiving from the network repository entity  23  a response message, in response to the discovery message, comprising:
         a list of filtered session control entities  22 , filtered based on the filtering criteria.       

     Moreover, the method can further comprise a step S 2 - 5  of transmitting to a first filtered session control entity  22 , of the filtered session control entities  22 , an association request message comprising:
         an identifier of the user plane entity  21 .       

     Generally, the selection of the first filtered session control entity  22  from the filtered session control entities  22  can be based on different criteria, such as location of the session control entity  22 . 
     Thanks to the method described above, it is thus advantageously possible to operate the user plane entity  21  so as to obtain an association between the user plane entity  21  and one session control entity  22  while operating the user plane entity  21  in a service-based manner. 
     In some embodiments, the association request message can further comprise:
         a list of capabilities of the user plane entity  21 .       

     Thanks to this approach it is advantageously possible to provide the list of capabilities of the user plane entity  21  directly to the associated session control entity  22 , thus avoiding the need for the session control entity  22  to retrieve them from the network repository entity  23  and/or allowing different capabilities to be registered by the user plane entity  21  with the associated session control entity  22  and with the network repository entity  23 . 
     Moreover, as illustrated for instance in  FIG.  2   b   , an embodiment of the invention can relate to a method for operating a session control entity  22  in a wireless communication network. The wireless communication network can comprise a user plane entity  21 , a plurality of session control entities  22  and a network repository entity  23 . 
     The plurality of session control entities  22  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  21  can be generally configured to handle a user plane of the at least one data packet session. The network repository entity  23  can be generally configured to register the plurality of session control entities  22  and the user plane entity  21 . 
     The method can comprise a step S 2 - 2  of transmitting to the network repository entity  23  a registration message comprising:
         an association service indication, for indicating that the session control entity  22  can be associated to a user plane entity  21 ,   an area indication of the session control entity  22 ,       

     The method can further comprise a step S 2 - 5  of receiving from the user plane entity  21  an association request message comprising:
         an identifier of the user plane entity  21 .       

     Thanks to this approach, the information registered at step S 2 - 2  can be advantageously used by the wireless communication network to lead to step S 2 - 5 , resulting in the association of user plane entity  21  and session control entity  22  even in the absence of a point-to-point interface between those entities. 
     In some embodiments, the association request message can further comprise
         a list of capabilities of the user plane entity  21 .       

     In some embodiments, the method can further comprise a step S 2 - 6  of transmitting to the network repository entity  23  a capabilities request message comprising:
         the identifier of the user plane entity  21 .       

     Still further, the method can comprise a step S 2 - 7  of receiving from the network repository entity  23  a capabilities indication message, in response to the capabilities request message, comprising:
         a list of capabilities of the user plane entity  21  identified by the identifier.       

     Thanks to this approach, the list of capabilities of the user plane entity  21  can be advantageously retrieved from the network repository entity  23 . 
     In some embodiments, the step S 2 - 6  of transmitting the capabilities request message, and S 2 - 7  of receiving the capabilities indication message can be carried out if the association request message does not comprise a list of capabilities of the user plane entity  21 . 
     Thanks to this approach, the steps S 2 - 6  and S 2 - 7  can advantageously be avoided if the list of capabilities is already available at the session control entity  22 . 
     Moreover, as illustrated for instance in  FIG.  2   c   , an embodiment of the invention can relate to a method for operating a network repository entity  23  in a wireless communication network. The wireless communication network can comprise a user plane entity  21 , a plurality of session control entities  22  and the network repository entity  23 . 
     The plurality of session control entities  22  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  21  can be generally configured to handle a user plane of the at least one data packet session. The network repository entity  23  can be generally configured to register the plurality of session control entities  22  and the user plane entity  21 . 
     The method can comprise a step S 2 - 2  of receiving S 2 - 2  from at least one of the plurality of session control entities  22  a registration message comprising:
         an association service indication, for indicating that the at least one session control entity  22  can be associated to a user plane entity  21 ,   an area indication of the at least one session control entity  22 .       

     In some embodiments this step can be carried out by a plurality, or all, of the plurality of session control entities  22 . 
     The method can further comprise a step S 2 - 3  of receiving from the user plane entity  21  a discovery message comprising:
         an association request indication, indicating that the user plane entity  21  can be associated to a session control entities  22 ,   filtering criteria for filtering the plurality of session control entities  22 .       

     The method can further comprise a step S 2 - 4  of transmitting to the user plane entity  21  a response message, in response to the discovery message, comprising:
         a list of filtered session control entities  22 , filtered based on the filtering criteria.       

     It will be clear that the network repository entity  23  can be configured to filter, from those session control entity  22  which have registered with the network repository entity  23 , the session control entities  22  which match the filtering criteria provided by the user plane entity  21 . 
     In some embodiments, the method can further comprise a step S 2 - 6  of receiving from the at least one session control entity  22  a capabilities request message comprising:
         an identifier of the user plane entity  21 .       

     The method can further comprise a step S 2 - 7  of transmitting to the at least one session control entity  22  a capabilities indication message, in response to the capabilities request message, comprising:
         a list of capabilities of the user plane entity  21  identified by the identifier.       

     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  2    in a 5G network, one or more of steps S 2 - 1  to S 2 - 8  could be formally formulated as: 
     S 2 - 1 : Nnrf_NFMgmt NFRegister {capabilities} 
     S 2 - 2 : Nnrf_NFMgmt NFRegister {Association service, SMF area} 
     S 2 - 3 . Nnrf_NFMgmt NFDiscovery {NFtype=SMF, Association service, filter criteria: SMF area 
     /UPF-ID/NSI-ID/UPF Location} 
     S 2 - 4 . Response (list of SMF addresses) 
     S 2 - 5 . Nsmf_Association {UPF-ID, (opt) capabilities} 
     S 2 - 6 . Nnrf_AccessToken Get {UPF-ID, capabilities} 
     S 2 - 7 . Response (capabilities) 
     S 2 - 8 . Response 
     Thanks to the methods described above it is possible to operate various network entities so at to allow the association between a user plane entity  21  and a session control entity  22 , in particular allowing triggering of the association by the user plane entity  21 . As an alternative, it is also possible to allow such association to be triggered by the session control entity  22 , as will be explained more in detail with reference to  FIG.  3   . 
       FIG.  3    shows an example flowchart of a method for operating a user plane entity  31 , a session control entity  32  and a network repository entity  33  in a wireless communication network. In particular the method allows the association of a service-based user plane entity  31  with a session control entity  32 . In the embodiments of  FIG.  3   , the association is generally triggered by the session control entity  32 . 
     The method generally allows the association between the user plane entity  31  and the session control entity  32 . The association can then be used to exchange node level messages, including the exchange of Node Capabilities. Moreover, the association can allow initiating node level operation, for instance if a user plane entity  31  is being decommissioned, it may request the session control entity  2  to terminate all its PDU sessions. 
       FIG.  3    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  3    will be described first. 
     At step S 3 - 1 , the user plane entity  31  can generally register itself with network repository entity  33 . The details of the message sent at step S 3 - 1  will be described in the following. In general, in some embodiments, the message sent at step S 3 - 1  can comprise a list of capabilities of the user plane entity  31 , for instance capabilities which can be accessed by other entities in the wireless communication network. Moreover, the message sent at step S 3 - 1  can also provide an indication that the user plane entity  31  supports an association service. Furthermore, the message sent at step S 3 - 1  can also comprise an area indication of a session control entity  32  to which the user plane entity  31  belongs and/or other filtering criteria. 
     At step S 3 - 2 , the session control entity  32  can generally send to network repository entity  33  a discovery request allowing the identification of one or more user plane entity  31 , to which the session control entity  32  can associate to. The details of the message sent at step S 3 - 2  will be described in the following. 
     At step S 3 - 3 , the network repository entity  33  can generally respond with one or more selected user plane entity  31 , based on the indications provided at step S 3 - 2 . The details of the message sent at step S 3 - 3  will be described in the following. 
     At step S 3 - 4 , the session control entity  32  can generally send a message to a user plane entity  31  for carrying out the association. The details of the message sent at step S 3 - 4  will be described in the following. 
     At step S 3 - 5 , the user plane entity  31  can generally respond with a message acknowledging the association with the session control entity  32 . The details of the message sent at step S 3 - 5  will be described in the following. In some embodiments, the message sent at step S 3 - 5  could also comprise an identifier of the user plane entity  31 . 
     In general it will be understood that at step S 3 - 5  the user plane entity  31  could also send, together with the association confirmation message, a list of its capabilities. This could be particularly advantageous, for instance, if the list of capabilities of the user plane entity  31  was not transmitted to the network repository entity  33  at step S 3 - 1 . Moreover, even if the list of capabilities were transmitted to the network repository entity  33  at step S 3 - 1 , by transmitting it directly to the session control entity  32  at step S 3 - 5 , the session control entity  32  could be provided with the list of capabilities in a faster manner, during the confirmation of the association. Still further, this allows the possibility of sending different capabilities in steps S 3 - 1  and S 3 - 5 . 
     In those embodiments in which the list of capabilities is not sent at step S 3 - 5 , optional step S 3 - 6  can generally allow the session control entity  32  to request those capabilities to the network repository entity  33 , while optional step S 3 - 7  can generally allow the session control entity  32  to receive the requested list of capabilities from the network repository entity  33 . The details of the messages sent at steps S 3 - 6  and S 3 - 7  will be described in the following. 
     Thanks to this approach it is possible for the user plane entity  31  and the session control entity  32  to be associated with each other and for the session control entity  32  to make use of the capabilities, or services, offered by the user plane entity  31 , in a manner compatible with a service-based user plane entity  31 . 
     In the following specific embodiments relating to the method described with reference to  FIG.  3    will be described in details. It will be understood that, as described in the following, not all steps illustrated in  FIG.  3    are necessary for the implementation of every embodiment. 
     In particular, as illustrated for instance in  FIG.  3   a   , an embodiment of the invention can relate to a method for operating a user plane entity  31  in a wireless communication network, the wireless communication network comprising a plurality of user plane entities  31 , a session control entity  32  and a network repository entity  33 . 
     The session control entity  32  can be generally configured to handle at least one data packet session in the wireless communication network. The plurality of user plane entities  31  can be generally configured to handle a user plane of the at least one data packet session. The network repository entity  33  can be generally configured to register the session control entity  32  and the plurality of user plane entities  31 . 
     The method can comprise a step S 3 - 1  of transmitting to the network repository entity  33  a registration message comprising:
         an association service indication, for indicating that the user plane entity  31  can be associated to a session control entity  32 .       

     In some embodiments, the registration message can further comprise:
         a list of capabilities of the user plane entity  31 , for instance capabilities which can be accessed by other entities in the wireless communication network, and/or   an area indication of a session control entity  32  to which the user plane entity  31  belongs,   and/or other filtering criteria.       

     The method can further comprise a step S 3 - 4  of receiving from the session control entity  32  an association request message comprising:
         an identifier of the session control entity  32 .       

     The method can further comprise a step S 3 - 5  of transmitting to the session control entity  32  an association confirmation message, in response to the association request message. 
     Thanks to this approach, it is possible to identify the user plane entity  31  to which the session control entity  32  is to be associated to. In particular, the information registered at step S 3 - 1  can be advantageously used by the wireless communication network to lead to step S 3 - 4 , resulting in the association of user plane entity  31  and session control entity  32  even in the absence of a point-to-point interface between those entities. 
     In some embodiments, the association confirmation message can further comprise:
         a list of capabilities of the user plane entity  31 .       

     Thanks to this approach it is advantageously possible to provide the list of capabilities of the user plane entity  31  directly to the associated session control entity  32 , thus avoiding the need for the session control entity  32  to retrieve them from the network repository entity  33  and/or allowing different capabilities to be registered by the user plane entity  31  with the associated session control entity  32  and with the network repository entity  33 . 
     Moreover, as illustrated for instance in  FIG.  3   b   , an embodiment of the invention can relate to a method for operating a session control entity  32  in a wireless communication network. The wireless communication network can comprise a plurality of user plane entities  31 , the session control entity  32  and a network repository entity  33 . 
     The session control entity  32  can be generally configured to handle at least one data packet session in the wireless communication network. The plurality of user plane entities  31  can be generally configured to handle a user plane of the at least one data packet session. The network repository entity  33  can be generally configured to register the session control entity  32  and the plurality of user plane entities  31 . 
     The method can comprise a step S 3 - 2  of transmitting to the network repository entity  33  a discovery message comprising:
         an association request indication, for indicating that the session control entity  32  can be associated to a user plane entity  31 ,   filtering criteria for filtering the plurality of user plane entities  31 .       

     In some embodiments, the filtering criteria can comprise one or more of:
         an area of the session control entity  32 ;   one or more capabilities of the user plane entity  31 ;   an identifier of a slice of the wireless communication network, for instance, in particular within a 5G implementation, a Network Slice Instance, NSI ID;   a location of the user plane entity  21 .       

     The method can further comprise a step S 3 - 3  of receiving from the network repository entity  33  a response message, in response to the discovery message, comprising:
         a list of filtered user plane entities  31 , filtered based on the filtering criteria.       

     In some embodiments, the list of filtered user plane entities  31  can comprise, for each user plane entity  31 , an identifier of the user plane entity  31  and/or an address of the user plane entity  31 . 
     The method can further comprise a step S 3 - 4  of transmitting to a first filtered user plane entity  31 , of the filtered user plane entities  31 , an association request message comprising:
         an identifier of the session control entity  32 .       

     Generally, the selection of the first filtered user plane entity  31  from the filtered user plane entities  31  can be based on different criteria, such as location of the session control entity  32 . 
     Thanks to the method described above, it is thus advantageously possible to operate the session control entity  32  so as to obtain an association between the user plane entity  31  and one session control entity  32  while operating the user plane entity  31  in a service-based manner. 
     In some embodiments, the method can further comprise a step S 3 - 5  of receiving from the first filtered user plane entity  31  an association confirmation message, in response to the association request message. 
     In some embodiments, the association confirmation message can further comprise:
         a list of capabilities of the first filtered user plane entity ( 31 ).       

     In some embodiments, the method can further comprise a step S 3 - 6  of transmitting to the network repository entity  33  a capabilities request message comprising:
         the identifier of the first filtered user plane entity  31 .       

     Furthermore, the method can further comprise a step S 3 - 7  of receiving from the network repository entity  33  a capabilities indication message, in response to the capabilities request message, comprising:
         a list of capabilities of the first filtered user plane entity  31  identified by the identifier.       

     Thanks to this approach, the list of capabilities of the user plane entity  31  can be advantageously retrieved from the network repository entity  33 . 
     In some embodiments, the step  3 - 6  of transmitting the capabilities request message, and S 3 - 7  of receiving the capabilities indication message can be carried out if the association confirmation message does not comprise a list of capabilities of the user plane entity  31 . 
     Thanks to this approach, the steps S 3 - 6  and S 3 - 7  can advantageously be avoided if the list of capabilities is already available at the session control entity  32 . 
     Moreover, as illustrated for instance in  FIG.  3   c   , an embodiment of the invention can relate to a method for operating a network repository entity  33  in a wireless communication network. The wireless communication network can comprise a plurality of user plane entities  31 , a session control entity  32  and the network repository entity  33 . 
     The session control entity  32  can be generally configured to handle at least one data packet session in the wireless communication network. The plurality of user plane entities  31  can be generally configured to handle a user plane of the at least one data packet session. The network repository entity  33  can be generally configured to register the session control entity  32  and the plurality of user plane entities  31 . 
     The method can comprise a step S 3 - 1  of receiving S 3 - 1  from at least one of the user plane entities  31  a registration message comprising:
         an association service indication, for indicating that the at least one user plane entity  31  can be associated to a session control entity  32 .       

     In some embodiments, the registration message can further comprise:
         a list of capabilities of the user plane entity  31 , for instance capabilities which can be accessed by other entities in the wireless communication network, and/or   an area indication of a session control entity  32  to which the user plane entity  31  belongs,   and/or other filtering criteria.       

     The method can further comprise a step S 3 - 2  of receiving from the session control entity  32  a discovery message comprising:
         an association request indication, for indicating that the session control entity  31  can be associated to a user plane entity  32 ,   filtering criteria for filtering the plurality of user plane entities  31 .       

     The method can further comprise a step S 3 - 3  of transmitting to the session control entity  32  a response message, in response to the discovery message, comprising:
         a list of filtered user plane entities  31 , filtered based on the filtering criteria.       

     It will be clear that the network repository entity  33  can be configured to filter, from those user plane entities  31  which have registered with the network repository entity  33 , the user plane entities  31  which match the filtering criteria provided by the session control entity  32 . 
     In some embodiments, the method can further comprise a step S 3 - 6  of receiving S 3 - 6  from the session control entity  32  a capabilities request message comprising:
         an identifier of a user plane entity  31 .       

     The method can further comprise a step S 3 - 7  of transmitting to the session control entity  32  a capabilities indication message, in response to the capabilities request message, comprising:
         a list of capabilities of the user plane entity  31  identified by the identifier.       

     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  3    in a 5G network, one or more of steps S 3 - 1  to S 3 - 7  could be formally formulated as: 
     S 3 - 1 . Nnrf_NFMgmt NFRegister {capabilities, Association service, SMF area / . . . } 
     S 3 - 2 . Nnrf_NFMgmt NFDiscovery {NFtype=UPF, Association service, filter criteria: SMF area 
     /UPF capabilities, NSI ID, Location, etc.} 
     S 3 - 3 . Response (list of UPF-ID and/or UPF address) 
     S 3 - 4 . Nupf_Association {SMF-ID} 
     S 3 - 5 . Response (opt capabilities) 
     S 3 - 6 . Nnrf_AccessToken Get {UPF-ID, capabilities} 
     S 3 - 7 . Response (capabilities) 
     It will be clear to those skilled in the art that other service operations handled by the association service(s) and targeting all or a group of the PDU sessions handled by the NF, may be defined, in particular in addition to the NF capabilities discovery in the embodiments described above with reference to  FIGS.  2  and  3   . 
       FIG.  4    shows an example flowchart of a method for operating a mobility management entity  41 , user plane entities  42  and  43 , a session control entity  44 , a policy control entity  45  and a network repository entity  46  in a wireless communication network. In particular the method relates to a process taking place at PDU session establishment with service-based user plane entities  42 ,  43 . 
     The method generally allows the one or more session control entity  44 , selected by the mobility management entity  41  to select the specific user plane entity  42 , 43  and the respective services to be appointed for the user plane packet processing of the specific PDU session. 
       FIG.  4    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  4    will be described first. 
     At step S 4 - 1  the mobility management entity  41  generally initiates a session establishment by sending a session establishment request message to the session control entity  44 . Generally, the session establishment request message indicates a request for establishing a PDU session. In some embodiments, the session establishment request message comprises one or more of an identifier of a user of the wireless communication network, in particular of a UE  110 , and/or a location of a UE, preferably of the UE corresponding to the user identifier. 
     At steps S 4 - 2  and S 4 - 3 , the session control entity retrieves policy rules, such as Policy and Charging Control, PCC, corresponding to the UE of the session establishment request message. This is achieved by sending, at step S 4 - 2  a policy request message to the policy control entity  45 . In some embodiments, the policy request message can comprise the user identifier of the session establishment request message. At step S 4 - 3  the policy control entity  45  responds with a policy activation message, which will be described in the following. It will be understood that the policy activation message relates to the policy rules to be activated with respect to the policy request message, that is, for instance, with respect to the user identifier of the session establishment request message. 
     At step S 4 - 4 , the session control entity  44  evaluates whether traffic breakout is needed. That is, it is evaluated if one or more user plane entities  42 ,  43  are needed to implement the policy rules. Depending on the results of the evaluation, the one or more user plane entities  42 ,  43  might also be identified. In some embodiments, the location of each of the one or more user plane entities  42 ,  43  could be determined. In the embodiment illustrates in  FIG.  4   , an example is provided in which the result of step S 4 - 4  consists of two user plane entities  42 ,  43  and the following description will be based on this assumption. It will however be clear that the invention is not limited to this specific implementation and that more or less than two user plane entities  42 ,  43  could be implemented, depending on the result of the step S 4 - 4 . 
     At steps S 4 - 5  and S 4 - 6 , the session control entity  44  generally retrieves further details concerning the one or more user plane entities  42 ,  43  determined at step S 4 - 4 . This is achieved, in particular by sending, at step S 4 - 5 , a discovery message to the network repository entity  46  and by receiving, at step S 4 - 6 , a response message from the network repository entity  46 . The details of those messages are discussed in the following. 
     At step S 4 - 7 , the session control entity  44  generally selects one or more of the user plane entities  42 ,  43  for the PDU session and/or the one or more services to be configured, and/or chained, in each user plane entity  42 ,  43 . In some embodiments, the selection can be done based on one or more of the associated user plane entities, services and location of the user plane entity. It will be clear to those skilled in the art that the specific algorithms used for the selection are implementation specific. 
     Steps S 4 - 8  and S 4 - 9 , which are optional, generally allow the session control entity  44  to configure one or more services in the one or more user plane entities  42 ,  43  based on the results of step S 4 - 7 . In particular, in some embodiments, the session control entity  44  can invoke a generic configuration service of the user plane entity  42 ,  43 , as generally exposed by the service-based user plane entity  42 ,  43  in the wireless communication network. Alternatively, or in addition, the session control entity  44  can invoke and activation and/or configuration function of the specific service required on the user plane entity  42 ,  43 . That is, in the first case, reference is made to a function of the user plane entity  42 ,  43  which allows the configuration of a generic service thereof, and the service can be provided as an object of the request, together with the activation/configuration of the service. In the second case, reference is made to a configuration function of the user plane entity  42 ,  43  specific to the service which needs to be configured, so that only the activation/configuration needs to be provided as an object of the request. 
     Steps S 4 - 8  and S 4 - 9  can be implemented for one or more of the user plane entities  42 ,  43  identified in step S 4 - 7 . It will be clear that steps S 4 - 8  and S 4 - 9  could be optional since, in some cases, it is possible that the desired services at the user plane entity  42 ,  43  are already activated and configured as necessary. In preferred embodiments, steps S 4 - 8 , S 4 - 9  are implemented for each of the user plane entities  42 ,  43  determined at step S 4 - 7 . 
     At steps S 4 - 10 , S 4 - 11 , the session control entity  44  generally establish a packet data session, for instance a PDU session, at one or more of the user plane entities  42 ,  43  determined at step S 4 - 7 . Details of the session establishment message sent to the respective user plane entity are described in the following. In preferred embodiments, steps S 4 - 10 , S 4 - 11  are implemented for each of the user plane entities  42 ,  43  determined at step S 4 - 7 . 
     At steps S 4 - 12 , S 4 - 13 , the user plane entities  42 ,  43  generally confirm receipt of the respective session establishment messages and/or implementation of the session establishment. 
     At step S 4 - 14  the session establishment procedure is completed. In particular, in some embodiments, among the various steps which may be taken to complete the session establishment, the session control entity  44  can transmit a PDU session establishment response to the mobility management entity  41 . 
     In particular, as illustrated for instance in  FIG.  4   a   , an embodiment of the invention can relate to a method for operating a session control entity  44  in a wireless communication network, the wireless communication network comprising a plurality of user plane entities  42 ,  43 , the session control entity  44 , a policy control entity  45 , and a network repository entity  46 . In some further embodiment, the wireless communication network can further comprise a mobility management entity  41 . 
     The session control entity  44  can be generally configured to handle at least one data packet session in the wireless communication network. The plurality of user plane entities  42 ,  43  can be generally configured to handle a user plane of the at least one data packet session. The policy control entity  45  can be generally configured to handle a policy plane of the at least one data packet session. The network repository entity  46  can be generally configured to register the plurality of session control entities  44  and the user plane entity  42 . In some embodiments, the network repository entity  46  can be further generally configured to register the mobility management entity  41  and/or the policy control entity  45 . The mobility management entity  41  can be generally configured to manage the mobility of one or more UE  110  through the wireless communication network. 
     The method can comprise a step S 4 - 3  of receiving from the policy control entity  45  a policy activation message comprising:
         a list of services to be activated in the plurality of user plane entities  42 ,  43 .       

     In some embodiments, the list of services may be specific for a given user identifier previously provided to the policy control entity  45 . Moreover, in some embodiments, the services may comprise one or more of
         services to activate in user plane entity  42 ,  43  such as, for instance, Firewalling, QoS, DDoS, detection, etc.       

     In some embodiments, the policy activation message can further comprise one or more of:
         an identifier of an application, or type of traffic, to which the policies apply,   traffic steering information and/or routing profiles to apply for the given user identifier.       

     The method can further comprise a step S 4 - 5  of transmitting to the network repository entity  46  a discovery message comprising:
         filtering criteria for filtering the plurality of user plane entities  42 ,  43 .       

     In some embodiments, the filtering criteria may comprise one or more of:
         an area of a session control entity  44 ;   one or more services of a user plane entity  42 ,  43 ;   an identifier of a slice of the wireless communication network, for instance, in particular within a 5G implementation, a Network Slice Instance, NSI ID;   location of the one or more user plane entities  42 ,  43 , preferably as determined at step S 4 - 4 .       

     In some embodiments, discovery message may further comprise:
         an indication that the discovery message relates to the discovery of one or more user plane entities  42 ,  43         

     The method can moreover comprise a step S 4 - 6  of receiving from the network repository entity  46  a response message, in response to the discovery message, comprising:
         a list of filtered user plane entities  42 ,  43 , filtered based on the filtering criteria.       

     In some embodiments, the response message may further comprise, for each of the filtered user plane entities  42 ,  43 , one or more of:
         an identifier of the user plane entity  42 ,  43 ;   services, or capabilities, offered by the user plane entity  42 ,  43 ;   a location of the user plane entity  42 ,  43 , preferably if this was not included in the filtering criteria.       

     In some embodiments, the filtering criteria can comprise:
         the list of services to be activated in the plurality of user plane entities  42 ,  43 .       

     In some embodiments, the method can further comprise the step of:
         transmitting S 4 - 8 ,  4 - 9  to one of the filtered user plane entities  42 ,  43  a service configuration message for activating and/or configuring at least one of the list of services to be activated.       

     In some embodiments, the method can further comprise the step of:
         transmitting S 4 - 10 ,  4 - 11  to one of the filtered user plane entities  42 ,  43  a session establishment message for configuring one of the list of services to be activated.       

     In general, the session control entity  44  can control the packet processing in the user plane entities  42 ,  43  by establishing, modifying or deleting, packet sessions, such as Packet 
     Forwarding Control Protocol, PFCP, sessions. It will be clear that such packet sessions may correspond to an individual PDU session or a standalone PFCP session, not tied to any PDU session. Moreover, the session control entity  44  can control the packet processing in the user plane entities  42 ,  43  by provisioning, for instance by adding, modifying or deleting, parameters of the respective sessions. 
     Those parameters, particularly in the context of a 5G implementation, may comprise in particular Packet Detection Rules, PDRs, comprising a Packet Detection Information, PDI, specifying traffic filters or signatures against which incoming packets are matched. Each PDR can be associated to one or more of the following rules, providing the set of instructions to apply to packets matching the PDI:
         Forwarding Action Rule, FAR, which contains instructions related to the processing of the packets, in particular one or more of forward, duplicate, drop or buffer the packet with or without notifying the control plane function about the arrival of a DL packet;   QoS Enforcement Rule, QER, which contains instructions related to the QoS enforcement of the traffic;   Usage Reporting Rule, URR, which contains instructions related to traffic measurement and reporting;   Buffering Action Rule, BAR, which contains the buffering rules to apply to the matching packets.       

     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  4    in a 5G network, one or more of steps S 4 - 1  to S 4 - 14  could be formally formulated as: 
     S 4 - 1 : PDU session establishment request (User-ID, UE location) 
     S 4 - 2 : Get PCC rules (User-ID) 
     S 4 - 3 : PCC rule {App-ID, List (UP services), Traffic steering info/routing profile} 
     S 4 - 4 : Based on the traffic steering info SMF decides if traffic breakout (several UPFs) is needed and the locations the UPFs should be selected. 
     S 4 - 5 : Nnrf_NFDiscovery (NFType=UPF, location, list (UP services)) 
     S 4 - 6 : Response (list [UPF-ID, services, location]) 
     S 4 - 7 : Based on the associated UPFs, UPF services and location, SMF selects the UPF(s) and selects the services chained per UPF. 
     S 4 - 8 , S 4 - 9 : (Optional) Nupf_ConfigService {activation/config} and/or (Optional) Nupf_X {activation/config}, where X is the service to be activated/configured 
     S 4 - 10 , S 4 - 11 : Nupf_SM {PDR (App-ID), FAR [ordered-list(service-IDs)]} 
     S 4 - 12 , S 4 - 13 : Response 
     S 4 - 14 : 11. PDU session establishment completion 
     Thanks to the method described above it is possible to establish a packed data session in the presence of one or more service-based user plane entities  42 ,  43 . 
     If other network functions, or network entities, need to interact with the one or more service-based user plane entity handling the user plane of a specific packet session, those network entities generally need to obtain the address or identifier of the one or more user plane entities. In the following, various embodiments will be described which enable resolving the address and/or identifier of the one or more user plane entities and/or enable exchanging messages with the one or more user plane entities as well as subscription/notification to one or more service provided by the one or more user plane entities. 
     In the embodiments above, an association service and a session management service have been described for a service-based user plane entity. Those services might be implemented as two independent services. Alternatively, or in addition, the same functionality could be provided as a single service. In this case, the association and the session management functionality could be implemented as independent operations of the same service, instead of independent services. 
       FIG.  5    shows an example flowchart of a method for operating a user plane entity  51 , a session control entity  52 , a user repository entity  53 , and a wireless communication network entity  54  in a wireless communication network. In particular the method allows a generic wireless communication network entity  54  to access services provided by the service-based user plane entity  51 . In the embodiments of  FIG.  5   , the discovery of the services of the user plane entity  51  is generally obtained through the session control entity  52 . 
       FIG.  5    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  5    will be described first. 
     At step S 5 - 1 , the wireless communication network entity  54  generally requires the address of a session control entity  52  associated to a given user of the wireless communication network, for instance an UE  110 . In some embodiments this may be achieved by sending to the user repository entity  53  a user query message. In some embodiments, the user query message can comprise a user identifier, allowing identification of a given user in the wireless communication network. 
     At step S 5 - 2 , the user repository entity  53  generally responds to the wireless communication network entity  54  with an address of the session control entity  52  allocated to the given user. 
     At step S 5 - 3 , the wireless communication network entity  54  generally requests to the session control entity  52 , by using the address obtained at step S 5 - 2 , an address of a user plane entity  51 . In some embodiments, the user plane entity  51  may be the one associated to the given user. Moreover, in some embodiments, the user plane entity  51  may be the one associated to a given service, or capability. Details of the message sent at step S 5 - 3  will be discussed in the following. 
     At step S 5 - 4 , the session control entity  52  generally responds with the address of the user plane entity  51  identified based on the step S 5 - 3 . 
     At step S 5 - 5 , by using the address obtained at step S 5 - 4 , the wireless communication network entity  54  generally requests and/or subscribes to one or more services from user plane entity  51 . 
     At step S 5 - 6  the user plane entity  51  executes the requested service operation and provides the response to the wireless communication network entity  54 . 
     In the following specific embodiments relating to the method described with reference to  FIG.  5    will be described in details. It will be understood that, as described in the following, not all steps illustrated in  FIG.  5    are necessary for the implementation of every embodiment. 
     In particular, as illustrated for instance in  FIG.  5   a   , an embodiment of the invention can relate to a method for operating a session control entity  52  in a wireless communication network, the wireless communication network comprising a user plane entity  51 , the session control entity  52 , a user repository entity  53 , and a wireless communication network entity  54 . 
     The session control entity  52  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  51  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  53  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  54  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  51 . 
     The method can comprise a step S 5 - 3  of receiving from the wireless communication network entity  54  a service discovery message comprising:
         a service indication, for indicating a service provided by the user plane entity  51 ,   an identifier of a user of the wireless communication network.       

     The method can further comprise a step S 5 - 4  of transmitting to the wireless communication network entity  54  a response message, in response to the service discovery message, comprising:
         an address of the user plane entity  51 .       

     It will be clear that the address of the user plane entity  51  can be obtained by the session control entity  52  by filtering the available user plane entities  51  with respect to the user and service indicated in the service discovery message. 
     Moreover, as illustrated for instance in  FIG.  5   b   , an embodiment of the invention can relate to a method for operating a wireless communication network entity  54  in a wireless communication network, the wireless communication network comprising a user plane entity  51 , a session control entity  52 , a user repository entity  53 , and the wireless communication network entity  54 . 
     The session control entity  52  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  51  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  53  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  54  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  51 . 
     The method can comprise a step S 5 - 3  of transmitting to the session control entity  52  a service discovery message comprising:
         a service indication, for indicating a service provided by the user plane entity  51 ,   an identifier of a user of the wireless communication network.       

     The method can further comprise a step S 5 - 4  of receiving from the session control entity  52  a response message, in response to the service discovery message, comprising:
         an address of the user plane entity  51 .       

     Thanks to the methods described above, it is thus advantageously possible to identify a user plane entity  51  through a session control entity  52  while operating the user plane entity  51  in a service-based manner. 
     In some embodiments. the method can further comprise a step S 5 - 5  of transmitting to the user plane entity  51  a service request message comprising:
         the service indication,   the identifier of the user of the wireless communication network.       

     In this manner it is possible for the wireless communication network entity  54  to subscribe to the intended service for the intended user. 
     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  5    in a 5G network, one or more of steps S 5 - 1  to S 5 - 6  could be formally formulated as: 
     S 5 - 1 : Nudm_Get SMF (User-ID) 
     S 5 - 2 : SMF address 
     S 5 - 3 : Nsmf_Get Service (User-ID, service-ID) 
     S 5 - 4 : Service address 
     S 5 - 5 : Nupf_Service Request/Subscribe 
     S 5 - 6 : Response 
       FIG.  6    shows an example flowchart of a method for operating a user plane entity  61 , a session control entity  62 , a user repository entity  63 , and a wireless communication network entity  64  in a wireless communication network. In particular the method allows a generic wireless communication network entity  64  to access services provided by the service-based user plane entity  61 . In the embodiments of  FIG.  6   , the discovery of the services of the user plane entity  61  is generally obtained through the user repository entity  63 . 
       FIG.  6    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  6    will be described first. 
     At step S 6 - 1 , the session control entity  62  generally selects a service provided by the user plane entity  61  (step  7  in  FIG.  3   ). In some embodiments this could be done in a manner similar to what previously described for step S 4 - 7 . In some embodiments, the selection can be based on a user identifier and/or on a given service for a given user identifier. 
     At step S 6 - 2 , the session control entity  62  generally registers in the user repository entity  63  the service selected at step S 6 - 1 . In some embodiments this can also comprise sending a user identifier and a service indication. Details of the message sent at step S 6 - 2  will be discussed in the following. 
     At step  6 - 3  the user repository entity  63  generally acknowledges the registration. 
     At step S 6 - 4 , the wireless communication network entity  64  generally requests to the user repository entity  63  an address of a user plane entity  61 . In some embodiments, the user plane entity  61  may be the one associated to a given user. Moreover, in some embodiments, the user plane entity  61  may be the one associated to a given service, or capability. Details of the message sent at step S 6 - 4  will be discussed in the following. 
     At step S 6 - 5 , the session control entity  62  generally responds with the address of the user plane entity  61 , in some embodiments the address can be identified based on the registration of step S 6 - 2 . 
     At step S 6 - 6 , by using the address obtained at step S 6 - 5 , the wireless communication network entity  64  generally requests and/or subscribes to one or more services from user plane entity  61 . 
     At step S 6 - 7  the user plane entity  61  executes the requested service operation and provides the response to the wireless communication network entity  64 . 
     In the following specific embodiments relating to the method described with reference to  FIG.  6    will be described in details. It will be understood that, as described in the following, not all steps illustrated in  FIG.  6    are necessary for the implementation of every embodiment. 
     In particular, as illustrated for instance in  FIG.  6   a   , an embodiment of the invention can relate to a method for operating a user repository entity  63  in a wireless communication network, the wireless communication network comprising a user plane entity  61 , a session control entity  62 , the user repository entity  63 , and a wireless communication network entity  64 . 
     The session control entity  62  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  61  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  63  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  64  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  61 . 
     The method can comprise a step S 6 - 2  of receiving from the session control entity  62  a service registration message comprising:
         a service indication, for indicating a service provided by the user plane entity  61 ,   an identifier of a user of the wireless communication network.       

     This allows to register the service in association with the given user. The method can further comprise a step S 6 - 4  of receiving from the wireless communication network entity  64  a service discovery message comprising:
         the identifier of the user of the wireless communication network,       

     Thanks to this it is possible to retrieve the service associated to the user. The information on the service received at step S 6 - 2  might also comprise the address of the user plane entity  61  providing the service. Alternatively or in addition, it might be possible for the user repository entity  63  to retrieve the address of the user plane entity  61  providing a given service based on the characteristics of the service alone. 
     The method can further comprise a step S 6 - 5  of transmitting to the wireless communication network entity  64  a response message, in response to the service discovery message, comprising:
         an address of the user plane entity  61 .       

     In this manner it is possible for the wireless communication network entity  64  to obtain the address of the user plane entity  61  operating in a service-based manner, thanks to the registration of the service in the user repository entity  63 . 
     Additionally, as illustrated for instance in  FIG.  6   b   , an embodiment of the invention can relate to a method for operating a session control entity  62  in a wireless communication network, the wireless communication network comprising a user plane entity  61 , the session control entity  62 , a user repository entity  63 , and a wireless communication network entity  64 , 
     The session control entity  62  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  61  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  63  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  64  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  61 . 
     The method can comprise a step S 6 - 1  of selecting services provided by the user plane entity  61 . The method can further comprise a step S 6 - 2  of transmitting to the user repository entity  63  a service registration message comprising:
         a service indication, for indicating a service provided by the user plane entity  61 ,   an identifier of a user of the wireless communication network.       

     Further, as illustrated for instance in  FIG.  6   c   , an embodiment of the invention can relate to a method for operating a wireless communication network entity  64  in a wireless communication network, the wireless communication network comprising a user plane entity  61 , a session control entity  62 , a user repository entity  63 , and the wireless communication network entity  64 . 
     The session control entity  62  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  61  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  63  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  64  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  61 . 
     The method can comprise a step S 6 - 4  of transmitting S 6 - 4  to the user repository entity  63  a service discovery message comprising
         an identifier of a user of the wireless communication network,       

     The method can further comprise a step S 6 - 5  of receiving from the user repository entity  63  a response message, in response to the service discovery message, comprising:
         an address of the user plane entity  61 .       

     In this manner it is possible for the wireless communication network entity  64  to subscribe to the intended service for the intended user. 
     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  6    in a 5G network, one or more of steps S 6 - 1  to S 6 - 7  could be formally formulated as: 
     S 6 - 1 : Service selection 
     S 6 - 2 : Nudm_Register Service (User-ID, Service-ID) 
     S 6 - 3 : Response 
     S 6 - 4 : Nudm_Get UPF service (User-ID) 
     S 6 - 5 : Service address 
     S 6 - 6 : Nupf_Service Request 
     S 6 - 7 : Response 
       FIG.  7    shows an example flowchart of a method for operating a user plane entity  71 , a session control entity  72 , a user repository entity  73 , and a wireless communication network entity  74  in a wireless communication network. In particular the method allows a generic wireless communication network entity  74  to access services provided by the service-based user plane entity  71 . In the embodiments of  FIG.  7   , the discovery of the services of the user plane entity  71  is generally obtained through the user repository entity  73 . 
       FIG.  7    generally relates to a plurality of embodiments, which will be defined in the following description. For a better understanding of how those embodiments can cooperate with each other, a brief general description of all steps illustrated in  FIG.  7    will be described first. 
     At step S 7 - 1 , the wireless communication network entity  74  generally requires the address of a session control entity  72  associated to a given user of the wireless communication network, for instance an UE  110 . In some embodiments this may be achieved by sending to the user repository entity  73  a user query message. In some embodiments, the user query message can comprise a user identifier, allowing identification of a given user in the wireless communication network. 
     At step S 7 - 2 , the user repository entity  73  generally responds to the wireless communication network entity  74  with an address of the session control entity  72  allocated to the given user. 
     At step S 7 - 3 , the wireless communication network entity  74  generally requests to the session control entity  72 , by using the address obtained at step S 7 - 2  to subscribe the wireless communication network entity  74  to a service provided by user plane entity  71 . In some embodiments, the user plane entity  71  may be the one associated to the given user. Moreover, in some embodiments, the user plane entity  71  may be the one associated to a given service, or capability. Details of the message sent at step S 7 - 3  will be discussed in the following. 
     At steps S 7 - 4  and S 7 - 5  the session control entity  72  generally subscribes the service provided by user plane entity  71  on behalf of the wireless communication network entity  74 . The user plane entity  71  provides a response and/or output of the service to the session control entity  72 . 
     At step S 7 - 6  the session control entity  72  forwards the response and/or output of the service to the wireless communication network entity  74 . 
     In the following specific embodiments relating to the method described with reference to  FIG.  7    will be described in details. It will be understood that, as described in the following, not all steps illustrated in  FIG.  7    are necessary for the implementation of every embodiment. 
     In particular, as illustrated for instance in  FIG.  7   a   , an embodiment of the invention can relate to a method for operating a session control entity  72  in a wireless communication network, the wireless communication network comprising a user plane entity  71 , the session control entity  72 , a user repository entity  73 , and a wireless communication network entity  74 . 
     The session control entity  72  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  71  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  73  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  74  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  71 . 
     The method can comprise a step S 7 - 3  of receiving from the wireless communication network entity  74  a service registration message comprising:
         a service indication, for indicating a service provided by the user plane entity  71 ,   an identifier of a user of the wireless communication network.       

     In some embodiments, if the service needs parameters for its configuration and/or operation, those parameters can also be included in the service registration message. 
     The method can further comprise a step S 7 - 4  of transmitting to the user plane entity  71  a subscription message, in response to the service registration message, for subscribing the wireless communication network entity  74  to the service indicated by the service indication. 
     Thanks to this approach it is possible to subscribe the wireless communication network entity  74  to the service through the session control entity  72 . 
     In some embodiments. the method can further comprise a step S 7 - 5  of receiving from the user plane entity  71  a first response message, in response to the subscription message. 
     Moreover the method can further comprise a step S 7 - 6  of transmitting to the wireless communication network entity  74 , a second response message, in response to the service registration message, comprising at least part of the content of the first response message. 
     In this manner it is possible to forward the output of the service to the wireless communication network entity  74 . 
     Additionally, as illustrated for instance in  FIG.  7   b   , an embodiment of the invention can relate to a method for operating a wireless communication network entity  74  in a wireless communication network, the wireless communication network comprising a user plane entity  71 , a session control entity  72 , a user repository entity  73 , and the wireless communication network entity  74 . 
     The session control entity  72  can be generally configured to handle at least one data packet session in the wireless communication network. The user plane entity  71  can be generally configured to handle a user plane of the at least one data packet session. The user repository entity  73  can be generally configured to register subscriber information for users of the wireless communication network. The wireless communication network entity  74  can be generally an entity of the wireless communication network accessing services of at least the user plane entity  71 . 
     The method can comprise a step S 7 - 1  of transmitting to the user repository entity  73  a session control discovery message, comprising:
         an identifier of a user of the wireless communication network.       

     The method can further comprise a step S 7 - 2  of receiving from the user repository entity  73  a session control indication message, in response to the session control discovery message, comprising:
         the address of the session control entity  72 .       

     Additionally, the method can further comprise a step S 7 - 3  of transmitting to the session control entity  72  a service registration message comprising:
         a service indication, for indicating a service provided by the user plane entity  71 ,   the identifier of the user of the wireless communication network.       

     In some embodiments. the method can further comprise a step S 7 - 6  of receiving S 7 - 6  from the session control entity  72 , a response message, in response to the service registration message. 
     In some embodiments, specifically in an implementation of the embodiments described with reference to  FIG.  7    in a 5G network, one or more of steps S 7 - 1  to S 7 - 7  could be formally formulated as: 
     S 7 - 1 : Nudm_Get SMF (User-ID) 
     S 7 - 2 : SMF address 
     S 7 - 3 : Nsmf_UPF Service Request/Subscribe (User-ID, service-ID, params) 
     S 7 - 4 : Nupf_Service Request/Subscribe 
     S 7 - 5 : Response 
     S 7 - 6 : Response 
     Although the methods above have each been described independently with reference to a Figure comprising a plurality of steps implemented by a plurality of nodes, it will be clear that the invention can be implemented by a subset of those steps, carried out by one or more nodes. Moreover, features and advantages of one step described for a given embodiment can also apply to the same step, and/or an analogous step, described for a different embodiment. 
     Moreover, although the description above has been discussed in terms of method steps, it will be clear that the invention can also be implemented by respective devices. 
     In particular,  FIG.  8    shows an example schematic of a:
         user plane entity  21 ,   session control entity  22 ,   network repository entity  23 ,   user plane entity  31 ,   session control entity  32 ,   network repository entity  33 ,   session control entity  44 ,   session control entity  52 ,   wireless communication network entity  54 ,   user repository entity  63 ,   session control entity  62 ,   wireless communication network entity  64 ,   session control entity  72 ,   wireless communication network entity  74 ,       

     each comprising a processing unit  81 , an interface  82  and a memory  83 . The interface  82  is configured to allow communication with other entities in the wireless communication network. The memory  83  can comprise instructions configured to cause the processing unit  81  to carry out any of steps described above with reference to the respective entity. 
     Moreover, the respective devices for implementing the invention can be also defined in terms of modules. 
     In particular,  FIGS.  9 - 14    show example schematics of various modules of the:
         user plane entity  21 ,   session control entity  22 ,   network repository entity  23 ,   user plane entity  31 ,   session control entity  32 ,   network repository entity  33 ,   session control entity  44 ,   session control entity  52 ,   wireless communication network entity  54 ,   user repository entity  63 ,   session control entity  62 ,   wireless communication network entity  64 ,   session control entity  72 ,   wireless communication network entity  74 .       

     The modules generally allow each entity to implement any of the steps previously described in combination with the respective entity. More specifically,  FIG.  9   a    schematically illustrates modules M 2 - 3 , M 2 - 4  and M 2 - 5 , configured for carrying out the functionality of step S 2 - 3 , S 2 - 4  and S 2 - 5 , respectively.  FIG.  9   b    schematically illustrates modules M 2 - 2 , and M 2 - 5 , configured for carrying out the functionality of step S 2 - 2  and S 2 - 5 , respectively.  FIG.  9   c    schematically illustrates modules M 2 - 2 , M 2 - 3  and M 2 - 4 , configured for carrying out the functionality of step S 2 - 2 , S 2 - 3  and S 2 - 4 , respectively.  FIG.  10   a    schematically illustrates modules M 3 - 1 , M 3 - 4  and M 3 - 5 , configured for carrying out the functionality of step S 3 - 1 , S 3 - 4  and S 3 - 5 , respectively.  FIG.  10   b    schematically illustrates modules M 3 - 2 , M 3 - 3  and M 3 - 4 , configured for carrying out the functionality of step S 3 - 2 , S 3 - 3  and S 3 - 4 , respectively.  FIG.  10   c    schematically illustrates modules M 3 - 1 , M 3 - 2  and M 3 - 3 , configured for carrying out the functionality of step S 3 - 1 , S 3 - 2  and S 3 - 3 , respectively.  FIG.  11   a    schematically illustrates modules M 4 - 3 , M 4 - 5  and M 4 - 6 , configured for carrying out the functionality of step S 4 - 3 , S 4 - 5  and S 4 - 6 , respectively.  FIG.  12   a    schematically illustrates modules M 5 - 3  and M 5 - 4 , configured for carrying out the functionality of step S 5 - 3  and S 5 - 4 , respectively.  FIG.  12   b    schematically illustrates modules M 5 - 3  and M 5 - 4 , configured for carrying out the functionality of step S 5 - 3  and S 5 - 4 , respectively.  FIG.  13   a    schematically illustrates modules M 6 - 2 , M 6 - 4  and M 6 - 5 , configured for carrying out the functionality of step S 6 - 2 , S 6 - 4  and S 6 - 5 , respectively.  FIG.  13   b    schematically illustrates modules M 6 - 1  and M 6 - 2 , configured for carrying out the functionality of step S 6 - 1  and S 6 - 2 , respectively.  FIG.  13   b    schematically illustrates modules M 6 - 4  and M 6 - 5 , configured for carrying out the functionality of step S 6 - 4  and S 6 - 5 , respectively.  FIG.  14   a    schematically illustrates modules M 7 - 3  and M 7 - 4 , configured for carrying out the functionality of step S 7 - 3  and S 7 - 4 , respectively.  FIG.  14   b    schematically illustrates modules M 7 - 1 , M 7 - 2  and M 7 - 3 , configured for carrying out the functionality of step S 7 - 1 , S 7 - 2  and S 7 - 3 , respectively. 
     It will be clear that any of those entities can further comprise a module implementation of the other steps previously described. 
     In particular, in some embodiments, the session control entity  22  can further comprise modules M 2 - 6  and M 2 - 7 , configured for carrying out the functionality of step S 2 - 6  and S 2 - 7 , respectively, as illustrated in dashed lines in  FIG.  15    to indicate that those modules are optional the session control entity  22 . 
     Moreover, in some embodiments, the network repository entity  23  can further comprise modules M 2 - 6  and M 2 - 7 , configured for carrying out the functionality of step S 2 - 6  and S 2 - 7 , respectively, as illustrated in dashed lines in  FIG.  16    to indicate that those modules are optional the network repository entity  23 . 
     Moreover, in some embodiments, the session control entity  32  can further comprise one or more of modules M 3 - 5 , M 3 - 6  and M 3 - 7 , configured for carrying out the functionality of step S 3 - 5 , S 3 - 6  and S 3 - 7 , respectively, as illustrated in dashed lines in  FIG.  17    to indicate that those modules are optional the session control entity  32 . 
     Moreover, in some embodiments, the network repository entity  33  can further comprise modules M 3 - 6  and M 3 - 7 , configured for carrying out the functionality of step S 3 - 6  and S 3 - 7 , respectively, as illustrated in dashed lines in  FIG.  18    to indicate that those modules are optional the network repository entity  33 . 
     Moreover, in some embodiments, the session control entity  44  can further comprise one or more of modules M 4 - 8  to M 4 - 10 , configured for carrying out the functionality of step S 4 - 8  to S 4 - 10 , respectively, as illustrated in dashed lines in  FIG.  19    to indicate that those modules are optional the session control entity  44 . 
     Moreover, in some embodiments, the wireless communication network entity  54  can further comprise module M 5 - 5  configured for carrying out the functionality of step M 5 - 5 , as illustrated in dashed lines in  FIG.  20    to indicate that those modules are optional the wireless communication network entity  54 . 
     Moreover, in some embodiments, the session control repository entity  72  can further comprise modules M 7 - 5  and M 7 - 6 , configured for carrying out the functionality of step S 7 - 5  and S 7 - 6 , respectively, as illustrated in dashed lines in  FIG.  21    to indicate that those modules are optional the session control repository entity  72 . 
     Moreover, in some embodiments, the wireless communication network entity  74  can further comprise module M 7 - 6  configured for carrying out the functionality of step S 7 - 6 , as illustrated in dashed lines in  FIG.  22    to indicate that this modules is optional the wireless communication network entity  74 . 
     It will be further clear that any of those entities can further comprise additional module implementations, not illustrated, of the other steps previously described. 
     From the above said some general conclusions can be drawn: in general, the invention allows implementing a service-based user plane entity in a wireless communication network. Specific embodiments have been discussed regarding specific aspects of the implementation of the service-based user plane entity, such as how to associate the service-based user plane entity to other entities in the network, how to initiate a packet session, how to identify and/or subscribe to services offered by the service-based user plane entity. 
     REFERENCE NUMERALS 
     
         
           100 : 5G core network 
           101 : Network Slice Selection Function 
           102 : Network Exposure Function 
           103 : Network Repository Function 
           104 : Policy Control Function 
           105 : Unified Data Management 
           106 : Application Function 
           107 : Authentication Server Function 
           108 : Access and Mobility Management Function 
           109 : Session Management Function 
           110 : User Equipment 
           111 : Radio Access Network 
           112 : User Plane Function 
           113 : Data Network 
           114 : Network Data Analytics Function 
           21 : user plane entity 
           22 : session control entity 
           23 : network repository entity 
         S 2 - 1 : sending/receiving registration message 
         S 2 - 2 : sending/receiving registration message 
         S 2 - 3 : sending/receiving discovery message 
         S 2 - 4 : sending/receiving response message 
         S 2 - 5 : sending/receiving association request message 
         S 2 - 6 : sending/receiving capabilities request message 
         S 2 - 7 : sending/receiving capabilities indication message 
         S 2 - 8 : sending/receiving association confirmation message 
           31 : user plane entity 
           32 : session control entity 
           33 : network repository entity 
         S 3 - 1 : sending/receiving registration message 
         S 3 - 2 : sending/receiving discovery message 
         S 3 - 3 : sending/receiving response message 
         S 3 - 4 : sending/receiving association request message 
         S 3 - 5 : sending/receiving association confirmation message 
         S 3 - 6 : sending/receiving capabilities request message 
         S 3 - 7 : sending/receiving capabilities indication message 
           41 : mobility management entity 
           42 : user plane entity 
           43 : user plane entity 
           44 : session control entity 
           45 : policy control entity 
           46 : network repository entity 
         S 4 - 1 : sending/receiving session establishment request message 
         S 4 - 2 : sending/receiving policy request message 
         S 4 - 3 : sending/receiving policy activation message 
         S 4 - 4 : evaluating traffic breakout 
         S 4 - 5 : sending/receiving discovery message 
         S 4 - 6 : sending/receiving response message 
         S 4 - 7 : selecting user plane entity 
         S 4 - 8 : sending/receiving service configuration message 
         S 4 - 9 : sending/receiving service configuration message 
         S 4 - 10 : sending/receiving session establishment message 
         S 4 - 11 : sending/receiving session establishment message 
         S 4 - 12 : sending/receiving response message 
         S 4 - 13 : sending/receiving response message 
         S 4 - 14 : completing session establishment 
           51 : user plane entity 
           52 : session control entity 
           53 : user repository entity 
           54 : wireless communication network entity 
         S 5 - 1 : sending/receiving session control discovery message 
         S 5 - 2 : sending/receiving response message 
         S 5 - 3 : sending/receiving service discovery message 
         S 5 - 4 : sending/receiving response message 
         S 5 - 5 : sending/receiving service request message 
         S 5 - 6 : sending/receiving response message 
           61 : user plane entity 
           62 : session control entity 
           63 : user repository entity 
           64 : wireless communication network entity 
         S 6 - 1 : selecting service 
         S 6 - 2 : sending/receiving service registration message 
         S 6 - 3 : sending/receiving response message 
         S 6 - 4 : sending/receiving service discovery message 
         S 6 - 5 : sending/receiving response message 
         S 6 - 6 : sending/receiving service request message 
         S 6 - 7 : sending/receiving response message 
           71 : user plane entity 
           72 : session control entity 
           73 : user repository entity 
           74 : wireless communication network entity 
         S 7 - 1 : sending/receiving session control discovery message 
         S 7 - 2 : sending/receiving response message 
         S 7 - 3 : sending/receiving service registration message 
         S 7 - 4 : sending/receiving subscription message 
         S 7 - 5 : sending/receiving response message 
         S 7 - 7 : sending/receiving response message 
           81 : processing unit 
           82 : interface 
           83 : memory