Method, apparatus and computer program

Abstract

There is provided an apparatus providing a control plane entity (Cu-CP instance, enodeB-CP instance) of a radio access network, the apparatus comprising means for the control plane entity to perform:

Description

Technical Field Various examples of this disclosure relate to methods, apparatuses, and computer programs for a communication network. Background A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. A communication device may be provided with a service by an application server. Such communication networks operate in accordance with standards such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards are the so-called 5G (5th Generation) standards provided by 3GPP. Summary Some examples of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the embodiments of this disclosure, nor are they intended to be used to limit the scope of thereof. Other features, aspects, and elements will be readily apparent to a person skilled in the art in view of this disclosure. For example, it should be appreciated that further aspects may be provided by the combination of any two or more of the various aspects described below. According to an aspect, there is provided an apparatus providing a control plane entity of a radio access network, the apparatus comprising means for the control plane entity to perform: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and communicating with said instance for performing the user plane network function. In some examples, said instance for performing the user plane network function is one of: a network function instance, or a network function component instance. In some examples, said user plane network function is a gNodeB centralized unit user plane or an eNodeB user plane. In some examples, said instance for performing the user plane function is within one of a master node or a secondary node of the radio access network, wherein said data radio access bearer is terminated, and said user equipment is connected to at least both the master node and secondary node of the radio access network. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the segment routing segment identifier is an SRv6 segment identifier. In some examples, the information is received from an instance for performing a core network function. In some examples, the core network function is an access and mobility management function having selected a session management function for establishing a protocol data unit session, said instance for performing a user plane network function is a gNodeB centralized unit user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a protocol data unit session of the user equipment. In some examples, the core network function is a mobility management entity having selected a serving gateway and a packet data network gateway for establishing an evolved packet system session, said instance for performing a user plane network function being an eNodeB user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for an evolved packet system bearer of the user equipment, the information allowing uplink traffic to reach the serving gateway. In some examples, the core network function is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the information is received from an instance for performing a radio access network function. In some examples, the radio access network function is a gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, the control plane entity is the gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. It is the user plane of the secondary node via which the data radio bearer is forwarded either partially or fully. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is an eNodeB control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is an eNodeB user plane of the secondary node. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is a gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. In some examples, the information of the uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a data radio bearer of the user equipment. In some examples, the radio access network function is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the means for selecting comprises: means for determining, based on the information, a further instance for performing user plane network functions, the further instance having been selected by an entity from which the information was obtained from; and means for, based on the determining, selecting said instance for performing the user plane network function that is associated with the further instance that was selected by the entity. In some examples, the entity is a network entity. In some examples, the entity is one of: the instance for performing a core network function, or the instance for performing a radio access network function. In some examples, the information is received from an access and mobility management function in the core network, having selected a session management function for establishing a protocol data unit session, and the further instance is a core network user plane function for the protocol data unit session of the user equipment. In some examples, the information is received from a mobility management entity in the core network, having selected a serving gateway for establishing an evolved packet system session, and the further instance is a serving gateway for the evolved packet system session of the user equipment. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the gNodeB centralized unit user plane of the secondary node. In some examples, the information is received from the eNodeB control plane of a master node at which a data radio bearer is terminated, and the further instance is an eNodeB user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from a network function of a sixth generation network specified by the third generation partnership project, and the further instance is a network function of a sixth generation network specified by the third generation partnership project. In some examples, said instance for performing the user plane network function is geographically co-located with the further instance that was selected by the entity from which the information was obtained from. In some examples, the means are for the control plane entity to perform: disabling at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing for the data radio bearer. In some examples, the at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing, is disabled at the control plane entity, based on the information. In some examples, the control plane entity is an instance of a centralized unit control plane in a fifth generation next generation radio access network. In some examples, the control plane entity is an instance of an eNodeB control plane in a fourth generation evolved universal terrestrial radio access network. In some examples, the control plane entity is an instance in a sixth generation network. According to an aspect, there is provided a method comprising: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and communicating with said instance for performing the user plane network function. In some examples, said instance for performing the user plane network function is one of: a network function instance, or a network function component instance. In some examples, said user plane network function is a gNodeB centralized unit user plane or an eNodeB user plane. In some examples, said instance for performing the user plane function is within one of a master node or a secondary node of the radio access network, and wherein said data radio access bearer is terminated, and said user equipment is connected to at least both the master node and secondary node of the radio access network. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the segment routing segment identifier is an SRv6 segment identifier. In some examples, the information is received from an instance for performing a core network function. In some examples, the core network function is a mobility management entity, an access and mobility management function or a sixth generation core network control plane function. In some examples, the information is received from an instance for performing a radio access network function. In some examples, the selecting comprises: determining, based on the information, a further instance for performing user plane network functions, the further instance having been selected by an entity from which the information was obtained from; and based on the determining, selecting said instance for performing the user plane network function that is associated with the further instance that was selected by the entity. In some examples, said instance for performing the user plane network function is geographically co-located with the further instance that was selected by the entity. In some examples, the instance selected by the core network function is a user plane function for a protocol data unit session being established. In some examples, the instance selected by the core network function is for a protocol data unit session being established, and said instance for performing a user plane network function is for the protocol data unit session being established. In some examples, the information of the uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a protocol data unit session of the user equipment. In some examples, the method comprises: disabling at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing for the data radio bearer. In some examples, the core network function is an access and mobility management function having selected a session management function for establishing a protocol data unit session, said instance for performing a user plane network function is a gNodeB centralized unit user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a protocol data unit session of the user equipment. In some examples, the core network function is a mobility management entity having selected a serving gateway and a packet data network gateway for establishing an evolved packet system session, said instance for performing a user plane network function being an eNodeB user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for an evolved packet system bearer of the user equipment, the information allowing uplink traffic to reach the serving gateway. In some examples, the core network function is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the radio access network function is a gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, the control plane entity is the gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. It is the user plane of the secondary node via which the data radio bearer is forwarded either partially or fully. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is an eNodeB control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is an eNodeB user plane of the secondary node. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is a gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. In some examples, the entity is a network entity. In some examples, the entity is one of: the instance for performing a core network function, or the instance for performing a radio access network function. In some examples, the information is received from an access and mobility management function in the core network, having selected a session management function for establishing a protocol data unit session, and the further instance is a core network user plane function for the protocol data unit session of the user equipment. In some examples, the information is received from a mobility management entity in the core network, having selected a serving gateway for establishing an evolved packet system session, and the further instance is a serving gateway for the evolved packet system session of the user equipment. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the gNodeB centralized unit user plane of the secondary node. In some examples, the information is received from the eNodeB control plane of a master node at which a data radio bearer is terminated, and the further instance is an eNodeB user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from a network function of a sixth generation network specified by the third generation partnership project, and the further instance is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing, is disabled at the control plane entity, based on the information. In some examples, the method is performed by a control plane entity. In some examples, the control plane entity is an instance of a centralized unit control plane in a fifth generation next generation radio access network. In some examples, the control plane entity is an instance of an eNodeB control plane in a fourth generation evolved universal terrestrial radio access network. In some examples, the control plane entity is an instance in a sixth generation network. According to an aspect, there is provided an apparatus providing a control plane entity of a radio access network, the apparatus comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the control plane entity to perform: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and communicating with said instance for performing the user plane network function. In some examples, said instance for performing the user plane network function is one of: a network function instance, or a network function component instance. In some examples, said user plane network function is a gNodeB centralized unit user plane or an eNodeB user plane. In some examples, said instance for performing the user plane function is within one of a master node or a secondary node of the radio access network, and wherein said data radio access bearer is terminated, and said user equipment is connected to at least both the master node and secondary node of the radio access network. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the segment routing segment identifier is an SRv6 segment identifier. In some examples, the information is received from an instance for performing a core network function. In some examples, the core network function is a mobility management entity, an access and mobility management function or a sixth generation core network control plane function. In some examples, the information is received from an instance for performing a radio access network function. In some examples, the selecting comprises: determining, based on the information, a further instance for performing user plane network functions, the further instance having been selected by an entity from which the information was obtained from; and based on the determining, selecting said instance for performing the user plane network function that is associated with the further instance that was selected by the entity. In some examples, said instance for performing the user plane network function is geographically co-located with the further instance that was selected by the entity. In some examples, the instance selected by the core network function is a user plane function for a protocol data unit session being established. In some examples, the instance selected by the core network function is for a protocol data unit session being established, and said instance for performing a user plane network function is for the protocol data unit session being established. In some examples, the information of the uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a protocol data unit session of the user equipment. In some examples, the control plane entity is caused to perform: disabling at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing for the data radio bearer. In some examples, the at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing, is disabled at the control plane entity, based on the information. In some examples, the core network function is an access and mobility management function having selected a session management function for establishing a protocol data unit session, said instance for performing a user plane network function is a gNodeB centralized unit user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for a protocol data unit session of the user equipment. In some examples, the core network function is a mobility management entity having selected a serving gateway and a packet data network gateway for establishing an evolved packet system session, said instance for performing a user plane network function being an eNodeB user plane. In some examples, the information of an uplink user plane transport network layer, the information being associated with user plane traffic of the user equipment comprises: uplink user plane transport network layer information for an evolved packet system bearer of the user equipment, the information allowing uplink traffic to reach the serving gateway. In some examples, the core network function is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the radio access network function is a gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, the control plane entity is the gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. It is the user plane of the secondary node via which the data radio bearer is forwarded either partially or fully. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is an eNodeB control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is an eNodeB user plane of the secondary node. In some examples, the radio access network function is an eNodeB control plane of a master node at which a data radio bearer is terminated, the control plane entity is a gNodeB centralized unit control plane of a secondary node via which the data radio bearer is forwarded either partially or fully, and the instance for performing a user plane network function is a gNodeB centralized unit user plane of the secondary node. In some examples, the entity is a network entity. In some examples, the entity is one of: the instance for performing a core network function, or the instance for performing a radio access network function. In some examples, the information is received from an access and mobility management function in the core network, having selected a session management function for establishing a protocol data unit session, and the further instance is a core network user plane function for the protocol data unit session of the user equipment. In some examples, the information is received from a mobility management entity in the core network, having selected a serving gateway for establishing an evolved packet system session, and the further instance is a serving gateway for the evolved packet system session of the user equipment. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the gNodeB centralized unit user plane of the secondary node. In some examples, the information is received from the eNodeB control plane of a master node at which a data radio bearer is terminated, and the further instance is an eNodeB user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from the gNodeB centralized unit control plane of a master node at which a data radio bearer is terminated, and the further instance is a gNodeB centralized unit user plane of the master node for that bearer data radio bearer, the bearer being forwarded either partially or fully to the eNodeB user plane of the secondary node. In some examples, the information is received from a network function of a sixth generation network specified by the third generation partnership project, and the further instance is a network function of a sixth generation network specified by the third generation partnership project. In some examples, the control plane entity is an instance of a centralized unit control plane in a fifth generation next generation radio access network. In some examples, the control plane entity is an instance of an eNodeB control plane in a fourth generation evolved universal terrestrial radio access network. In some examples, the control plane entity is an instance in a sixth generation network. According to an aspect, there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform at least the following: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and communicating with said instance for performing the user plane network function. According to an aspect, there is provided an apparatus comprising: circuitry configured to perform: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; circuitry configured to perform: selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and circuitry configured to perform: communicating with said instance for performing the user plane network function. According to an aspect, there is provided an apparatus providing a user plane entity of a radio access network, the apparatus comprising means for the user plane entity to perform: receiving information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of a user equipment; and copying at least part of the information into further information related to a downlink user plane transport network layer. In some examples, the apparatus comprises: means for disabling, at the user plane entity, at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing based on the information. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching segment routing label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the information of the uplink user plane transport network layer is received from a control plane entity. In some examples, the user plane entity is one of: an instance of a centralized unit user plane, or an instance of a distributed unit. According to an aspect, there is provided a method comprising: receiving information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of a user equipment; and copying at least part of the information into further information related to a downlink user plane transport network layer. In some examples, the method comprises: disabling, at the user plane entity, at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing based on the information. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching segment routing label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the information of the uplink user plane transport network layer is received from a control plane entity. In some examples, the user plane entity is one of: an instance of a centralized unit user plane, or an instance of a distributed unit. In some examples, the method is performed by a user plane entity of a radio access network. According to an aspect, there is provided an apparatus providing a user plane entity of a radio access network, the apparatus comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user plane entity to perform: receiving information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of a user equipment; and copying at least part of the information into further information related to a downlink user plane transport network layer. In some examples, the apparatus is caused to perform: disabling, at the user plane entity, at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing based on the information. In some examples, the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching segment routing label associated with a user plane function, or a segment routing segment identifier associated with a user plane function. In some examples, the information of the uplink user plane transport network layer is received from a control plane entity. In some examples, the user plane entity is one of: an instance of a centralized unit user plane, or an instance of a distributed unit. According to an aspect, there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform at least the following: receiving information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of a user equipment; and copying at least part of the information into further information related to a downlink user plane transport network layer. A computer product stored on a medium may cause an apparatus to perform the 5 methods as described herein. A non-transitory computer readable medium comprising program instructions, that, when executed by an apparatus, cause the apparatus to perform the methods as described herein. An electronic device may comprise apparatus as described herein. 10 Various other aspects and further examples are also described in the following detailed description and in the attached claims. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The examples that do not fall under the scope of the claims are to be interpreted as examples useful for understanding 15 the disclosure. List of Abbreviations: AF: AMF: Application Function Access and Mobility Management Function 20 AN: Access Network AUPF: Access &User Plane Function BS: Base Station CaaS: Containers as a service CN: Core Network 25 CP: Control plane CU: Centralized unit DL: Downlink DNN: Data network name DU: Distributed unit 30 eNB: eNodeB F-TEID: Fully qualified tunnel endpoint identity gNB: gNodeB GPRS: General Packet Radio Service GTP: GPRS Tunnelling Protocol 35 laaS: Infrastructure as a service lloT: Industrial Internet of Things IPSec: Internet protocol security K8: LTE: MAC: MS: Kubernetes Long Term Evolution Medium access control Mobile Station 5 MPLS: Multiprotocol label switching NEF: Network Exposure Function NG-RAN: Next Generation Radio Access Network NG-U: NG user plane (N3) NF: Network Function 10 NR: New Radio NRF: Network Repository Function NW: Network PaaS: Platform as a service PDCP: Packet data convergence protocol 15 PDU: Protocol data unit PCF Policy Control Function PLMN: Public Land Mobile Network RAN: Radio Access Network RLC: Radio link control 20 RRC: Radio resource control RF: Radio Frequency SDAP: Service data adaptation protocol SMF: Session Management Function SRv6: Segment routing version 6 25 TEID: Tunnel endpoint identity TNL: Transport network layer UE: User Equipment UDR: Unified Data Repository UDM: Unified Data Management 30 UL: Uplink UP: User plane UPF: User Plane Function 3GPP: 3rd Generation Partnership Project 5G: 5th Generation 35 5GC: 5G Core network 5G-AN: 5G Radio Access Network 5GS: 5G System Brief Description of Drawings Some examples will now be described, by way of illustrative and non-limiting example only, with reference to the accompanying drawings in which: FIG. 1 shows a schematic representation of a 5G communication system; FIG. 2 shows a schematic representation of an apparatus for the 5G communication system of FIG. 1; FIG. 3 shows a schematic representation of a communication device; FIG. 4 shows a schematic representation of a 5G RAN comprising a centralized unit and a distributed unit; FIG. 5 shows a schematic representation of an access and user plane function within a 5G communication system; FIG. 6 shows a schematic representation of a co-Iocation of a RAN centralized unit user plane instance with a user plane function instance within a 5G communication system; FIG. 7 shows an example signalling and operations diagram for a PDU session establishment in a 5G communications system with a co-Iocation of a RAN centralized unit user plane instance with a user plane function instance; FIG. 8 shows an example method flow diagram performed by an apparatus; and FIG. 9 shows a schematic representation of a non-volatile memory medium storing instructions which when executed by a processor allow a processor to perform one or more of the steps of the method of FIG. 8. Detailed Description In some communication systems, such as for example 5G and 6G systems, a radio access network (RAN) node is split into a centralized unit (CU) and a distributed unit (DU). In 5G, a RAN node (or base station) is referred to as a gNodeB (gNB). Each gNB is logically divided into two distinct physical entities known as the CU and the DU. The CU supports upper layers of a protocol stack, including components such as service data adaptation protocol (SDAP), packet data convergence protocol (PDCP), and radio resource control (RRC). The DU is responsible for handling lower layers of the protocol stack, such as radio link control (RLC), medium access control (MAC), and the physical layer. Typically, a single CU is associated with each gNB. The single CU may manage (or oversee) a plurality of DUs. A communication interface between the CU and DU is referred to as the F1 interface. Both NG and Xn-C interfaces for a gNB terminate at the gNB-CU. The F1 interface supports signalling exchange and data transmission between these endpoints, effectively segregating a radio network layer from a transport network layer. An NGAP (Next Gen Application Part) protocol is provided for the control plane between the 5G core (5GC) and the 5G RAN. A gNB CU may be divided into its control plane (CP) and its user plane (UP) parts, which results in the gNB-CU-CP and gNB-CU-UP, respectively. Often these network functions are referred to as CU-CP and CU-UP, respectively. The interface between CU-CP and CU-UP is known as the E1 interface, which is primarily dedicated to control plane operations. A gNB may comprise a plurality of instances of CU-UPs. Therefore, a selection of an instance of a gNB-CU-UP may occur, e.g., when establishing a protocol data unit (PDU) session. For certain implementations, it may be suitable to merge the gNB-CU-UP with the UPF (of the 5GC) in some communication systems, to form an AUPF (Access &User Plane Function). This merging may include one or more of the following benefits: avoiding NG-U (N3-U) encoding and decoding between the RAN and the CN, avoiding internet protocol security (IPSec) tunnels protecting NG-U (N3-U) traffic between the RAN and the Security Gateway (SeGW), using a common buffer for downlink traffic to be acknowledged rather than a buffer in the gNB-CU-UP, for PDCP retransmissions and to permit lossless handover and another buffer in the UPF (during downlink data notifications aka paging), avoiding PDCP sequence resets upon handover, avoiding ROHCP process resets upon handover, registration of the combined entity to the Service Based Architecture (more specifically the NRF, notifying the NRF of availability, load and overload), sharing a common PaaS, CaaS, laaS, Life Cycle Manager, Element Manager, CI-CD chain, SW release cycle, Product Management, R&D, Validation, Delivery, Operations and other product synergies. The next generation (NG) user plane interface (NG-U) is defined between a 5G RAN node and a UPF. An AUPF may be deployed as a decentralized network function at an appropriate ‘Far Edge’ distributed cloud compute data center. Alternatively, an AUPF may be concentrated in large centralized cloud compute data centres benefiting from economy of scale. In this case, the AUPF may be owned by mobile network operators (MNOs), enterprises or hyperscalers. A hyperscaler is a type of large-scale data center that offers massive computing resources, typically in the form of an elastic cloud platform. In some examples, an apparatus is providing a control plane entity of a radio access network, the apparatus comprising means for the control plane entity to perform: obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment; selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and communicating with said instance for performing the user plane network function. These examples will be discussed in more detail below with reference to a 5G communication system that comprises a 5G RAN connected to a 5G Core network (e.g., as seen in FIG. 1). A detailed illustrative example of a 5G RAN with a CU, which also be decomposed into a CU-CP and a plurality of CU-UP, and a plurality of DU network functions is also discussed below (e.g., as seen in FIG. 4). A detailed illustrative example of an AUPF within a communication system is also discussed below (e.g., as seen in FIG. 5). In the following, various example embodiments of this disclosure are explained with reference to communication devices capable of communication via a wireless cellular system and communication systems serving such communication devices. Before explaining in detail the various example embodiments, certain general aspects of a wireless communication system and communication devices are briefly explained with reference to FIGS. 1 to 5 to assist in understanding the technology underlying the described examples. It should be understood that, even though some of the following FIGS, are related to 5G systems, examples of the present disclosure are also applicable to other standards, such as for example, 5G-advanced, 6G, etc. FIG. 1 shows a schematic representation of a 5G communication system 100. The wireless communication system 100 comprises one more communication devices 102 such as user equipments (UEs), or terminals. The wireless communication system 100 comprises a 5G system (5GS). The 5GS comprises a 5G radio access network (5G-RAN) 106, a 5G core network (5GC) 104 comprising one or more network functions (NF), one or more application functions (AFs) 108, and one or more data networks (DNs) 110. The 5G-RAN 106 may comprise one or more gNodeB (gNB) distributed unit (DU) functions connected to one or more gNodeB (gNB) centralized unit (CU) functions. The 5GC 104 comprises an access and mobility management function (AMF) 112, a session management function (SMF) 114, an authentication server function (AUSF) 116, a user data management (UDM) 118, a user plane function (UPF) 120, a network exposure function (NEF) 122 and / or other NFs. Some of the examples as shown below may be applicable to 3GPP 5G standards. However, some examples may also be applicable to 5G-advanced, 4G, 3G and other 3GPP standards. In a wireless communication system 100, such as that shown in FIG. 1, communication devices 102, such as for example, terminals, user apparatuses, user equipments (UE), and / or machine-type communication devices are provided with wireless access via at least one base station or similar wireless transmitting and / or receiving node or point. The communication device 102 is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other devices. The communication device 102 may access a carrier provided by a base station or access point, and transmit and / or receive communications on the carrier. FIG. 2 illustrates an example of an apparatus 200. The apparatus 200 may be for the 5G communication system of FIG. 1. The apparatus 200 may be for controlling a function of one or more network entities and / or network functions, such as the entities of the 5G-RAN or the 5GC as illustrated on FIG. 1. The apparatus 200 comprises at least one random access memory (RAM) 211a, at least one read only memory (ROM) 211b, at least one processor 212, 213 and an input / output interface 214. The at least one processor 212, 213 is coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may for example allow to perform one or more steps to perform one or more of the present aspects or examples. The software code 215 may be stored in the ROM 211b. The apparatus 200 may be interconnected with another apparatus 200 controlling another entity / function of the 5G-AN or the 5GC. In some examples, apparatus 200 may be configured to provide one or more functions of the 5G-AN or the 5GC. For example, apparatus 200 may be configured to perform at least some functionality of a particular function of the 5G-AN or the 5GC. For example, apparatus 200 may be configured to operate as a particular function of the 5G-AN or the 5GC. In alternative examples, apparatus 200 may be configured to perform at least some functionality of two or more functions of the 5G-AN and / or the 5GC. For example, apparatus 200 may be configured to operate as two or more functions of the 5G-AN and / or the 5GC. The apparatus 200 may comprise one or more circuits, or circuitry (not shown) which may be configured to perform one or more of the present aspects or examples. FIG. 3 illustrates an example of a communication device 300. The communication device 300 may be similar to the communication device 102 illustrated in FIG. 1. The communication device 300 may be provided by any device capable of sending and receiving radio signals. Non-limiting and illustrative examples of a communication device 300 are a user equipment, a terminal, a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, a Cellular Internet of Things (CloT) device, or a terrestrial / maritime / aerial vehicle such as a car, a truck, a boat, an air plane, or a drone, or any combinations of these or the like. The communication device 300 may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on. The communication device 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In FIG. 3, a transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided, for example, by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device. The communication device 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute appropriate software code 308. The software code 308 may, for example, allow to perform one or more of the present aspects. The software code 308 may be stored in the ROM 302a. The communication device 300 may comprise one or more circuits, or circuitry (not shown), which may be configured to perform one or more of the aspects or examples described herein. The processor, storage and other relevant control apparatus may be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 304. The communication device may optionally have a user interface, such as keypad 305, touch sensitive screen or pad, combinations thereof or the like. Optionally, one or more of a display, a speaker and a microphone may be provided depending on the type of the device. FIG. 4 shows a schematic representation of a 5G RAN comprising a centralized unit and a distributed unit. There is provided a 5G RAN 401, which may be referred to as a gNB 401. The gNB 401 may be similar to the 5G RAN 106 of FIG. 1. The gNB 401 comprises a gNB-CU-CP 403 and a plurality of gNB-CU-UPs 405. Each of the plurality of gNB-CU-UPs 405 may be referred to as an instance of a gNB-CU-UP. The gNB 401 also comprises a first gNB-DU 407 and a second gNB-DU 409. In the example of FIG. 4, there are two gNB-DUs. In other examples, there may be more or less than two gNB-DUs. The interface between the gNB-CU-CP 403 and each of the plurality of gNB-CU-UPs 405 is referred to as an E1 interface. The E1 interface is primarily dedicated to control plane operations. The interface between the gNB-CU-CP 403 and the first and second gNB-DUs 407, 409 is referred to as an F1-C (F1-Control Function) interface. The respective interfaces between the gNB-DUs 407, 409 and the plurality of gNB-CU-UPs 405 are individually referred to as an F1-U (F1-User Function) interface. Both the NG and Xn-C interfaces (not shown) for the gNB 401 terminate at the gNB-CU. The F1 interfaces support signalling exchange and data transmission between these endpoints, effectively segregating the radio network layer from the transport network layer. The gNB-CU-CP 403 hosts the radio resource control (RRC) and the control plane part of the PDCP protocol. The gNB-CU-CP 403 also terminates the E1 interface connected with the gNB-CU-UP 405 and the F1-C interface connected with the gNB-DUs 407, 409. Each gNB-CU-UP 405 hosts the user plane part of the PDCP protocol of the gNB-CU for the gNB 401. Each gNB-CU-UP 405 also hosts the SDAP protocol of the gNB-CU for a gNB. When establishing a protocol data unit (PDU) session, the gNB-CU-CP 403 receives information from the CN through an N2 PDU session resource setup request. Within the request, there may be an inclusion of information of an uplink (UL) user plane (UP) transport network layer (TNL) (e.g., uplink user plane transport network layer information I an uplink user plane transport network information element (IE)). For each PDU session, the gNB 401 (e.g., the gNB-CU-CP 403 and the gNB-CU-UP 405) stores the uplink user plane transport network layer IE. The information of the uplink user plane transport network layer IE is subsequently employed as an uplink termination point for routing user plane data to a UPF. FIG. 5 shows a schematic representation of an access and user plane function (AUPF) within a 5G communication system. Even though FIG. 5 depicts a 5G system, it is submitted that the interfaces and functions of the AUPF, as described below, are equally applicable to other 3GPP specifications, such as, e.g., 5G advanced, 6G, etc. There is provided a communication system 500 which has a UE 501 connected to a DU 503 of a gNB. A RAN-CP (or CU-CP) 505 has an interface with the DU 503 and an AUPF 507. As previously discussed, an AUPF is a function that is a combination of a CU-UP with a UPF. In this manner, a UPF is integrated with the CU-UP such that the combination is (logically) part of both the RAN and the mobile core network. In other examples, a UPF and a CU-UP are co-located (or collocated) with each other with each component remaining logically part of the RAN and mobile core network, respectively. In should be understood that in the context of this disclosure the terms co-located and collocated may be used interchangeably. The co-Iocation of a UPF and RAN-CU-CP may mean that these functions share a location or facility, share common compute resources, and / or are in geographical proximity with each other. The CU-CP 505 also has an interface with a core-CP 509. The core-CP may be an AMF and SMF along with other mobile core network control plane functionality in FIG. 1. The core-CP 509 has an N4 interface with the AUPF 507 and may also support an N4 interfaces with a UPF 511 to be used when providing services to a central packet data network (PDN) domain 515. The AUPF 507 has an interface to local (PDN) domains 513, while the UPF 511 has an interface to the (separate) central PDN domain 515. The AUPF may be connected to the local PDN 513 (with e.g., edge computing servers) and the UE 501 may be anchored at the UPF 511 (e.g., the UE has received an internet protocol (IP) address in a sub-net advertised by the UPF 511), for access to the IP multimedia system (IMS) or to another DN. During a PDU session establishment procedure for the UE 501, the UE will provide a request to the DU 503. As part of the PDU session establishment, the core-CP 509 (e.g., an SMF) will select a UPF for the PDU session. For example, the core-CP 509 may select the UPF 511. Subsequent to the selection of the UPF by the core-CP 509, the CU-CP 505 selects a CU-LIP for the PDU session. For example, the CU-CP 505 selects a CU-UP of the AUPF 507. The AUPF 507 and the UPF 511 may not be in close proximity to each other. In this manner, any communications between these functions may introduce latency. In some communication systems, a CU-CP receives information from a core network (CN) in a message, such as an N2 PDU Session Resource Setup Request. The request may comprise at least one of the following: N2 Session Management (SM) information, information of an UL NG-U UP TNL (e.g., Uplink User Plane Transport Network Layer IE) included in a PDU Session Resource Setup Request Transfer IE, an (end-to-end encrypted) NAS message (e.g., PDU Session ID, N1 SM container (PDU Session Establishment Accept)), or CN assisted RAN parameters tuning. The terms 'information of an UL UP TNL’, ‘information of an UL NG-U UP TNL’, ‘UL UP TNL information’, and ‘UL NG-U UP TNL information’ may be used interchangeably. As part of the N2 SM information, for each PDU session, an NG-RAN node (e.g., the gNB-CU-CP and gNB-CU-UP) shall store the UL NG-U UP TNL IE and use the UL NG-U UP TNL IE as an uplink termination point for the user plane data to the CN (e.g., UPF). However, such communication systems do not specify how the gNB-CU-CP should select, for each PDU session, either: 1) a gNB-CU-UP instance co-located with a UPF instance (e.g., deployed on the same container as a service (CaaS) instance, but in a different server on the same site), or 2) a combined AUPF instance which the SMF has already selected, or 3) a femto gateway (GW). A femto GW is a small, low-power cellular base station, typically designed for use in a home or small business. The selection by the gNB-CU-CP of the most suitable gNB-CU-CP / AUPF / femto-GW would help to reduce latencies for the PDU session and improve user experience. FIG. 6 shows a schematic representation of a co-Iocation of a RAN centralized unit user plane instance with a user plane function instance within a 5G communication system. There is provided a UE 601 which is able to communicate with a first RAN 603 and a second RAN 605 (e.g., gNBs). Each of the first and second RANs 603, 605 comprise a DU 607, a CU-CP 609 and a CU-UP 611, which each have respective interfaces therebetween. There is also a core-CP 613, a first UPF 615, and a second UPF 617. The core-CP 613 has interfaces with the CU-CP 609, the first UPF 615 and the second UPF 617. The first UPF 615 and the CU-UPs 611 of the first and second RANs 603, 605 are colocated with each other. Together, the first UPF 615 and the CU-UPs 611 may be referred to as an AUPF 619. The first UPF 615 and the CU-UPs 611 of the first and second RANs 603, 605 have interfaces between them. The first UPF 615 of the AUPF 619 is interfaced with local PDN domains 621. The second UPF 617 is interfaced with central PDN domains 623. There is also an interface between the first UPF 615 and the second UPF 617. The ratio of UPF instances to CU-UP instances within an AUPF is not necessarily 1:2 (e.g., as seen in FIG. 6), or 1:1. In other examples, ‘N’ UPF instances may be co-located with ‘M’ CU-UP NF instances. A selection of a AUPF for a PDU session that is being established, and the resulting benefits, for the co-located UPF and CU-UP scenario, is shown in FIG. 7 below. FIG. 7 shows an example signalling and operations diagram for a PDU session establishment in a 5G communications system. At S701, a UE provides a request for a PDU session establishment to a gNB. In particular, the request is provided to a gNB-CU-CP (or CU-CP) of the gNB. It should be understood that the terms RAN-CU and gNB-CU may be used interchangeably in the following examples. This is also the same for RAN-DU and gNB-DU. The request may be provided in an uplink (UL) radio resource control (RRC) message. The request may comprise non-access stratum (NAS) session management (SM) information associated with the UE. NAS SM supports the handling of Session Management between the UE and an SMF. NAS SM supports user plane PDU session establishment, modification and release. NAS SM is transferred via the gNB, and is transparent to the gNB. The gNB-CU-CP may be referred to as a gNB-CU-CP instance, instance of a gNB-CU-CP, or instance for performing a gNB-CU-CP function. These terms may be used interchangeably in the following examples. The same interchangeable terminology may be used for other network functions, such as for example, gNB-CU-UP, gNB-DU, etc. An instance of a network function may be the result of running a software program installed on a limited number of compute nodes (e.g., servers or virtual machines). For example, for a containerized network function (CNF product), the instance is identified by a Kubernetes (K8s) ‘Namespace’, containing a number of ‘K8s Pods’. Within each ‘K8s Pod’ is a CNF component instance with its own IP address. The CNF instance (e.g., K8s ‘Namespace’) is the result of applying the K8s "kubectl helm install -n $namespace" command on the K8s control plane (master nodes), and results in 'pods’ being deployed on the K8s worker / edge nodes. At S702, the gNB provides the request to an AMF of the 5G core. The AMF is part of the core control plane. The request may be provided in an UL NAS message to the AMF over the N2 interface. The request may comprise the NAS SM provided by the UE. At S703, the AMF performs a selection of an SMF or a combined SMF / serving PDN GW control plane (SPGW-C). The selection of the SMF or SMF / SPGW-C may be based on the request received by the AMF, and / or be the result of consulting an NRF (Network Repository Function). The SMF, SMF / SPGW-C and NRF are also part of the 5G core and the core CP. At S704, the AMF provides a PDU session create request to the SMF that has been selected. The PDU session create request is provided via a service based interface. At S705, the SMF (or combined SMF / SPGW-C) provides a response to the AMF. The response may be a PDU session create response message. At S706, the SMF (or combined SMF / SPGW-C) selects an AUPF instance and / or a UPF instance. The SMF also sets quality of service (QoS) information for the PDU session. Upon establishment of a PDU session, the SMF selects a suitable AUPF instance an / or UPF instance based on at least one of the following: S-NSSAI (Single Network Slice Selection Assistance Information), DNN (Data Network Name) or Tracking Area (TA). At S707, the SMF provides a request associated with session establishment to the selected AUPF or UPF instance (that has been selected by the SMF). The request is a session establishment request message over the N4 interface. The request may comprise information associated with a PDU configuration. At S708, the AUPF or UPF receives the information associated with the PDU configuration. The AUPF or UPF allocates UL NG-U (next generation user plane) Transport Network Layer (TNL) Information (which may also be referred to as information related to an UL UP TNL) to the PDU session. The UL NG-U TNL information may comprise a GTP (GPRS Tunnelling Protocol) fully qualified tunnel endpoint identifier (F-TEID) comprising an IP address and a TEID. In other examples, the AUPF or UPF allocates, as UL NG-U TNL information, a multiprotocol label switching (MPLS) segment routing label / MPLS label associated with the AUPF or UPF, or a segment routing (e.g., SRv6) segment identifier associated with the AUPF or UPF. At S709, the AUPF or UPF provides a response associated with the session establishment to the SMF or SMF / SPGW-C. The response may be a session establishment response message over the N4 interface. The response comprises the allocated UL NG-U TNL information which may carry information (e.g., a “flag”) that may be used by the gNB-CU-CP at S713 to recognise that the UPF corresponding to an AUPF or co-located CU-UP and UPF. At S710, the SMF or SMF / SPGW-C provides the UL NG-U TNL Information to the AMF. At S711, the AMF provides an acknowledgement to the SMF of the received UL NG-U TNL Information. At S712, the AMF provides a response message to the gNB-CU-CP. The response message may be a PDU session setup response sent over the N2 interface. The response message comprises information including at least one of the following: the UL NG-U TNL information, the QoS information, or the NAS SM. In this manner, the gNB-CU-CP may obtain (for the UE) the UL NG-U TNL information, wherein the UL NG-U TNL information is associated with user plane traffic of the UE. The UL NG-U TNL information may be for a PDU session for the UE. At S713, the gNB-CU-CP uses the information comprised in the request message from the AMF to modify its default gNB-CU-UP selection criteria. The gNB-CU-CP may determine that the UPF selected by the SMF is associated with the AUPF or UPF, based on the information. In some examples, the gNB-CU-CP determines which UPF / AUPF has been selected based on the information. The gNB-CU-CP then selects the gNB-CU-UP that is associated with the UPF selected by the SMF. In this example, the gNB-CU-UP is associated with the UPF as they are co-located with each other. Examples of being co-located include: in the same city, in the same datacenter, in the same computer rack, or in the same compute node or virtual machine. At S714, the gNB-CU-CP provides a request message to the gNB-CU-UP that has been selected. The request message may be a bearer context setup request message over the E1 interface. The request message may comprise information including at least one of the following: the UL NG-U TNL information, or PDCPu / SDAP config. At S715, the gNB-CU-UP uses the information provided in S714 to set the PDCP and / or SDAP configuration for the PDU session. The gNB-CU-UP performs an UL F1u TEID selection. F1u is the user plane interface between a DU and CU-UP. The gNB-CU-UP sets a downlink (DL) NG-U TEID to an AUPF flag that may be used by the SMF at S726 to confirm that the gNB-CU-UP has been correctly configured as part of AUPF or as a co-located CU-UP and UPF. At S716, the gNB-CU-UP provides a bearer context setup response to the gNB-CU-CP, wherein the response comprises at least one of the following: the UL NG-U TEID, the QoS information, or the NAS SM. The response may also indicate that the DL NG-U TEID has been set to the AUPF flag. At S717, the gNB-CU-CP provides a UE context setup request to a gNB-DU, wherein the request comprises at least one of the following: the UL NG-U TNL information, or a DRB configuration. At S718, the gNB-DU determines a data radio bearer configuration based on the request. The gNB-DU performs a DL F1u TEID selection based on the request. The selected DL F1u TEID is associated with a data radio bearer. At S719, the gNB-DU provides a UE context setup response to the gNB-CU-CP, wherein the response comprises the DL F1u TEID that has been selected. At S720, the gNB-CU-CP provides a bearer context modification request to the gNB-CU-UP / AUPF, wherein the request comprises the DL F1u TEID that has been selected. At S721, the gNB-CU-UP / AUPF provides a bearer context modification response message to the gNB-CU-CP. At S722, the gNB-CU-CP provides an RRC reconfiguration message to the UE. At S723, the UE provides an RRC reconfiguration complete message to the gNB-CU-CP. At S724, the gNB-CU-CP provides a PDU session setup response to the AMF, wherein the response comprises the DL F1u TEID. At S725, the AMF provides a PDU session update request to the SMF. The PDU session update request may indicate the DL NGu TEID. At S726, an AUPF confirmation is performed by the SMF. At S727, the SMF provides a session medication request to the UPF / AUPF. The session modification request may indicate the DL NGu TEID. At S728, the UPF / AUPF provides a session medication response to the SMF. At S729, the SMF provides a PDU session update response to the AMF. Therefore, in some examples, an SMF selects an AUPF or UPF instance for a PDU session being established. Information related to the selection of the UPF instance will then be provided to the gNB / RAN. The gNB / RAN then selects a RAN-CU-UP for the PDU session. However, in some examples (e.g., as shown in FIG. 7), a RAN-CU-CP is co-located with a UPF. Therefore, it is beneficial if a RAN-CU-CP that is selected by the gNB is associated with the UPF that has been selected by the SMF, for reasons such as latency. As shown in example of FIG. 7 above, the RAN-CU-CP receives information from the SMF related to a UPF selection by the SMF. The RAN-CU-CP then determines and selects a RAN-CU-UP that is co-located with the AUPF or UPF selected by the SMF. When there is an integrated RAN-CU-UP and UPF (forming an AUPF), the procedure of FIG. 7 is equally applicable. For an AUPF with an integrated RAN-CU-UP and UPF, the UPF and RAN-CU-UP are associated with each other. During a PDU session establishment, an SMF selects a UPF (e.g., as shown in S706 of FIG. 7) based on, for example, information about a network slice, a data network name (DNN), tracking area identifier (TAI), etc. An instance of a UPF within an AUPF, which may be implemented as a UPF component instance (e.g., UPF pod), may have alternative configurations for how to manage received downlink packets / frames from a data network. For example, the instance of the UPF may: produce N3 GTP-encapsulated traffic, for downlink transport to an external gNB-CU-UP. For example, via a datacentre gateway and / or a mobile backhaul network; or provide the traffic unencapsulated to a co-located CU-UP instance (e.g., a co-located K8s pod) for SDAP / PDCP processing; or perform SDAP and / or PDCP processing and send F1-U GTP-encapsulated traffic to a DU function in a neighbouring network function component (NFC) (e.g., for radio link control (RLC) / medium access control (MAC) processing). A neighbouring network function component is a ‘Pod’ type (for CNFs) or a virtual machine (VM) type (for virtualised NFs (VNFs)). An NFC is the "product" (the program), and the NFC instances are the result of its installation / instantiation on a computer or VM; or perform SDAP and / or PDCP processing and send F1-U GTP-encapsulated traffic to an external gNB-DU. For example, via a datacentre gateway and mobile fronthaul / midhaul network. In some examples, a user plane NF instance receives first information related to a UL UP TNL (e.g., from the CN), and copies at least part of the first information into second information related to a downlink (DL) UP TNL. For example, if a CU-UP determines that an internet protocol (IP) address of the first information (e.g., an UL N3 GTP F-TEID) for uplink transport is unrouteable, the CU-UP selects the same IP address for the second information associated with DL NG-U UP TNL (e.g., DL N3 GTP F-TEID at gNB-CU-UP). In this context, the term unrouteable may mean that there is no IP route in the routing information base (RIB) (which is comprised in the first information), which would be used to reach the (sub-net of) the IP destination address. Alternatively or additionally, in other examples, the same TEID is used, the same UDP port is used, the same nodal MPLS label (representing the AUPF in the N6 Data Network) is used, etc. In some examples, the gNB-DU would select the same IP address for third information related to a DL F1-U UP TNL (e.g., DL F1-U GTP F-TEID at gNB-DU). F1-U is the user plane interface between the CU and DU of the RAN. When the CU-UP receives the unrouteable (or unreachable) first information related to the UL UP TNL, the CU-UP may disable (or enable) SDAP and / or PDCP processing at the CU-UP. With disabled SDAP and / or PDCP processing at the SDAP and / or PDCP processing, DL GTP-U traffic is provided to (or passed on to) the gNB-DU. The manner of receiving the unreachable first information related to the UL UP TNL (e.g., implicitly) indicates that another entity (e.g., the AUPF) is already performing SDAP and / or PDCP processing. As the other entity is already performing the SDAP and / or PDCP processing, the CU-CP does not need to perform such processing and thus disables said processing. In some examples, it may be assumed that SDAP and / or PDCP are disabled (e.g., by default), and the CU-CP enables SDAP and / or PDCP processing accordingly. In some examples whereby an AUPF is performing SDAP and / or PDCP processing, the AUPF may send PDCP-compressed and encrypted traffic to a DL NG-U UP TNL address, which is the TNL address of the gNB-DU. The DL GTP F-TEID may be assigned by a gNB-DU (rather than a RAN-CU-UP. In this manner, in some examples, at least part of received (first) information related to a UL UP TNL is used to disable (or enable) PDCP processing. In some examples, at least part of received (first) information related to a UL UP TNL is used to disable (or enable) SDAP processing. Some examples may be relevant in scenarios of dual connectivity (DC) or multiconnectivity (MC) of a single user equipment to multiple RAN nodes. For RAN bearers terminated at a master node (MN) (e.g., with PDCP and SDAP processing at the MN), a control plane of the MN (e.g., the RAN-CU-CP of the MN, which may be denoted as MN-CU-CP if it is different from an SN-CU-CP) obtains DL UP TNL information from a secondary node. This allows the CP of the MN to forward the bearer to the SN(-CU-UP), either entirely, or partially if the bearer is split. The DL UP TNL information is obtained either because the RAN-CU-CP (4G RAN-CP) controls both the MN-CU-UP (4G MN-UP) and SN-CU-UP (4G SN-UP), or because the MN-CU-CP (4G MN-CP) obtains it from the SN-CU-CP (4G SN-CP). For SN-terminated bearers, a RAN-CU-CP (4G RAN-CP) obtains UL TNL information from the MN-CU-UP (4G MN-UP). SN (e.g., SN-CU-UP or SN-UP) selection occurs after the MN (incl. MN-CU-UP or MN-UP) selection. Due to this, it may be beneficial for the SN to perform a ‘smart’ SN-CU-UP (4G SN-UP) selection. For example, to select a SN-CU-UP (4G SN-UP) that is either co-located or integrated / collapsed with the MN-CU-UP (4G MN-UP). In this context, “collapsed” may be the same NF instance, or the same NF component instance (e.g., same K8s Pod). For bearers terminated at the MN, it may be beneficial for the RAN-CU-CP (4G RAN-CP) or SN-CU-CP (4G SN-CP) to select the SN-CU-UP (4G SN-UP) based on the UL UP TNL information allocated by the MN-CU-UP (4G MN-UP). When a bearer is moved to the SN / becomes terminated at the SN, it may be beneficial for the RAN-CU-CP (4G RAN-CP) or MN-CU-CP (4G MN-CP) to select the MN-CU-UP (4G MN-UP) based on the UL UP TNL information allocated by the SN-CU-UP (4G SN-UP), resulting in a MN-CU-UP (4G MN-UP) that is either co-located or integrated / collapsed with the SN-CU-UP (4G SN-UP). In some examples, a RAN node (e.g., a CU-UP co-located or collapsed with a UPF) receives uplink F1-U PDCP traffic and does not send uplink N3 GTP-U traffic, but connects a UE to a DN, another UE or a Multi-Access Edge Computing (MEC) server. In some examples, a RAN node (e.g., DU and CU-UP and UPF) receives uplink RLC-MAC traffic from a radio unit (RU) and does not send uplink F1-U GTP-U traffic, but connects a UE to a DN, another UE or a MEC server. In some examples, a CN node (e.g., gNB-CU-UP and UPF) receives downlink data traffic (e.g. from SGi / N6) and sends downlink PDCP traffic over GTP-U to a gNB-DU In some examples, a CN node (e.g., gNB-DU and gNB-CU-UP and UPF) receives downlink data traffic (e.g., from Sgi / N6) and sends downlink RLC / MAC traffic straight to an RU. One or more of the examples above have the advantage that in some communication systems, 3GPP N4, N2 and E1 protocols have not been modified when introducing a colocated UPF with the RAN node, or a deeply combined AUPF. In this manner, the communication systems have not been able to benefit from the co-located UPF with the RAN node, or a deeply combined AUPF. A UPF passes its identity and whether it performs new functions (e.g., SDAP / PDCP) as indications (e.g., implicit indications) to RAN nodes, over unmodified protocols. eNodeBs, gNodeBs and 6GnodeBs may therefore be developed to include a co-located or deeply integrated UPF function without any modification of the 5G core. This can speed up the introduction of pockets of 5G advanced, as well as 6G for the RU, DU, CU-CP and AUPF. One or more of the examples above may be applied to modernize existing E-UTRANs and NG-RANs, for example as an incentive to containerize them, and to introduce low-latency UE-to-UE and UE-to-MEC services requiring a very distributed UPF at far edge. One or more of the examples may also reduce latencies for PDU sessions, when there is a co-located or collapsed CU-UP and UPF, as a CU-UP is selected based on received information from the 5GC such that the optimum instance of RAN-CU-UP is selected. For example, the latency can be reduced for data traffic going to another UE or to a DN that is attached (via N6) to the AUPF or to the UPF that is collocated with the gNB-DU-UP. For example, the CU-UP is selected that is co-located or integrated with the UPF selected by the 5GC for a PDU session. As the path for communications is shorter, the latency can be reduced. FIG. 8 shows an example method flow performed by an apparatus. In some examples, the apparatus may be configured to provide a control plane entity of a radio access network. For example, the apparatus may be configured to perform at least some functionality of the control plane entity of the radio access network. For example, the apparatus may be configured to operate as the control plane entity of the radio access network. In alternative examples, the apparatus may be configured to perform: at least some functionality of the control plane entity of the radio access network, at least some functionality of one or more other functions of the radio access network, and / or at least some functionality of one or more functions of the core network. For example, apparatus 200 may be configured to operate as: the control plane entity of the radio access network, one or more other functions of the radio access network; and / or one or more functions of the core network. In some examples, the apparatus comprises means for the control plane entity to perform the features of FIG. 8. The apparatus may provide a control plane entity of a radio access network. In some examples, the apparatus comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the features of FIG. 8. The control plane entity may be an instance of a CU-CP in a 5G RAN. The control plane entity may be an instance of an eNodeB control plane in a 4G evolved universal terrestrial radio access network. The control plane entity may be an instance in a 6G network. In S801, the method comprises obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment. In S803, the method comprises selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment. In S805, the method comprises communicating with said instance for performing the user plane network function. FIG. 9 shows a schematic representation of non-volatile memory media 900a (e.g., Blu-ray disc (BD), computer disc (CD) or digital versatile disc (DVD)) and 900b (e.g., flash memory, solid state drive (SSD), universal serial bus (USB) memory stick) storing instructions and / or parameters 902 which when executed by a processor allow the processor to perform one or more of the steps of the methods of FIG. 8. It is noted that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solutions without departing from the scope of this disclosure. The examples may thus vary within the scope of the attached claims. In general, some example embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although embodiments are not limited thereto. While various embodiments may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting and illustrative examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The examples may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any procedures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The term “non-transitory”, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs ROM). As used herein, “at least one of the following: ” and “at least one of: <a list of two or more elements*” and similar wording, where the list of two or more elements are joined by “and”, or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements. Similarly, the expression “and / or” includes any and all combinations of the listed terms, including any one of the elements, any two or more of the elements, and all of the elements. As used herein, the terms “first X” and “second X” include the options that “first X” is the same as “second X” and that “first X” is different from “second X”, unless otherwise specified. These terms are merely used to distinguish one element from another without indicating a temporal relationship, unless otherwise apparent from the disclosure. As used herein, the term "or" refers to a non-exclusive “or” unless otherwise indicated (e.g., use of “or else” or “or in the alternative”). As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included. Analogously, performing a step or functionality “based on A” does not indicate that the step or functionality is performed solely based on “A” as one or more additional conditions may be included. The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. In some examples, the term “means for”, or “means configured to perform” (or similar) may be any means that are suitable for performing the feature. The “means” may be configured to perform one or more of the functions and / or method steps previously described. For example, the “means” may include one or more of: at least one processor, at least one memory, transceiver circuitry, antenna circuitry, etc. It should be understood that these “means” are provided as non-limiting and illustrative examples. Alternatively, or additionally some examples may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and / or method steps previously described. That circuitry may be provided in the base station and / or in the communications device. As used herein, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analogue and / or digital circuitry); (b) combinations of hardware circuits and software, such as: (i) a combination of analogue and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as the communications device or base station to perform the various functions previously described; and c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of “circuitry” applies to uses of the term “means” herein, including in any claims. As a further example, as used herein, the term “circuitry” also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term “circuitry” also covers, for example integrated device. The term “circuitry” also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device. The foregoing description has provided, by way of non-limiting and illustrative examples, a full and informative description of some embodiments. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the claims. However, all such and similar modifications of the teachings will still fall within the scope of this disclosure. For example, further example embodiments may be provided by the combination of any two or more of the various example embodiments described above.

Claims

1. An apparatus configured to provide a control plane entity of a radio access network, the apparatus comprising means for the control plane entity to perform:obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment;selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; andcommunicating with said instance for performing the user plane network function.

2. The apparatus according to claim 1, wherein said instance for performing the user plane network function is one of: a network function instance, or a network function component instance.

3. The apparatus according to claim 1 or claim 2, wherein said user plane network function is a gNodeB centralized unit user plane or an eNodeB user plane.

4. The apparatus according to any of claims 1 to 3, wherein said instance for performing the user plane function is within one of a master node or a secondary node of the radio access network,wherein said data radio access bearer is terminated, and said user equipment is connected to at least both the master node and secondary node of the radio access network.

5. The apparatus according to any of claims 1 to 4, wherein the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching label associated with a user plane function, or a segment routing segment identifier associated with a user plane function.

6. The apparatus according to any of claims 1 to 5, wherein the information is received from an instance for performing a core network function.

7. The apparatus according to any of claims 1 to 5, wherein the information is received from an instance for performing a radio access network function.

8. The apparatus according to any of claims 1 to 7, wherein the means for selecting comprises:means for determining, based on the information, a further instance for performing user plane network functions, the further instance having been selected by an entity from which the information was obtained from; andmeans for selecting, based on the determining, said instance for performing the user plane network function that is associated with the further instance that was selected by the entity.

9. The apparatus according to claim 8, wherein said instance for performing the user plane network function is geographically co-located with the further instance that was selected by the entity from which the information was obtained from.

10. The apparatus according to any of claims 1 to 9, wherein the means are for the control plane entity to perform:disabling at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing for the data radio bearer.

11. The apparatus according to any of claims 1 to 10, wherein the control plane entity is an instance of a centralized unit control plane in a fifth generation next generation radio access network.

12. The apparatus according to any of claims 1 to 10, wherein the control plane entity is an instance of an eNodeB control plane in a fourth generation evolved universal terrestrial radio access network.

13. The apparatus according to any of claims 1 to 10, wherein the control plane entity is an instance in a sixth generation network.

14. A method comprising:obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment;selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; andcommunicating with said instance for performing the user plane network function.

15. The method according to claim 14, wherein said instance for performing the user plane network function is one of: a network function instance, or a network function component instance.

16. The method according to claim 14 or claim 15, wherein said user plane network function is a gNodeB centralized unit user plane or an eNodeB user plane.

17. The method according to any of claims 14 to 16, wherein said instance for performing the user plane function is within one of a master node or a secondary node of the radio access network, andwherein said data radio access bearer is terminated, and said user equipment is connected to at least both the master node and secondary node of the radio access network.

18. The method according to any of claims 14 to 17, wherein the information of the uplink user plane transport network layer comprises at least one of the following: a fully qualified tunnel endpoint identifier associated with a user plane function, a multiprotocol label switching label associated with a user plane function, or a segment routing segment identifier associated with a user plane function.

19. The method according to any of claims 14 to 18, wherein the information is received from an instance for performing a core network function.

20. The method according to any of claims 14 to 19, wherein the information is received from an instance for performing a radio access network function.

21. The method according to any of claims 14 to 20, wherein the selecting comprises: determining, based on the information, a further instance for performing user plane network functions, the further instance having been selected by an entity from which the information was obtained from; andbased on the determining, selecting said instance for performing the user plane network function that is associated with the further instance that was selected by the entity.

22. The method according to claim 21, wherein said instance for performing the user plane network function is geographically co-located with the further instance that was selected by the entity.

23. The method according to any of claims 14 to 22, wherein the method comprises: disabling at least one of the following: service data adaptation protocol processing, or packet data convergence protocol processing for the data radio bearer.

24. The method according to any of claims 14 to 23, wherein the method is performed by a control plane entity.

25. A computer program comprising instructions, which when executed by an apparatus, 5 cause the apparatus to perform at least the following:obtaining, for a user equipment, information of an uplink user plane transport network layer, wherein the information is associated with user plane traffic of the user equipment;selecting, based on the information, an instance for performing a user plane network function that has a data radio bearer to the user equipment; and10 communicating with said instance for performing the user plane network function.

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