Apparatus, methods and computer programs relating to application server relocation

Abstract

A user equipment, UE 300 comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least: receiving an

Description

Field This disclosure generally relates to communication systems and in particular but not exclusively to apparatus, methods and computer programs relating to application server relocation. Background A communication system 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 network is one example of a communication system. A communication device may be provided with a service by an application server. Such communication systems operate in according 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 According to one aspect, there is provided a user equipment comprising: means for receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to the user equipment to the second application server providing the service to the user equipment; and means for communicating with the second application server at a time, wherein the time is dependent on the relocation time. The means for receiving may be for receiving one or more of: information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from the user equipment to the first application server; or information relating to an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server providing the service to the user equipment to the second application server providing the service to the user equipment. The user equipment may comprise means for stopping sending traffic to the first application server at the relocation time at or a time prior to the relocation time. The user equipment may comprise means for determining the time prior to the relocation time based on the relocation time and the uplink traffic transmission delay. The user equipment may comprise means for causing the traffic which has been stopped from being sent to be subsequently sent to the second application server. The user equipment may comprise means for buffering the traffic which the user equipment has stopped from being sent to the first application server and means for causing the traffic which has been buffered to be sent to the second application server at or after the relocation time. The traffic which has been buffered to be sent to the second application server may be sent at a time based on the relocation time and the application context relocation duration. The user equipment may comprise means for stopping uplink communication with the first application server at a time based on the relocation time and the application context relocation duration, and to start uplink communication with the second application server at the time based on the relocation time and the application context relocation duration. The communicating with the second application server may be is at the relocation time. The application server and the relocation time may be received in a protocol data unit session modification command. According to another aspect, there is provided a user equipment comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to perform at least: receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to the user equipment to the second application server providing the service to the user equipment; and communicating with the second application server at a time, wherein the time is dependent on the relocation time. According to another aspect, there is provided a method comprising: receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to a user equipment to the second application server providing the service to the user equipment; and communicating with the second application server at a time, wherein the time is dependent on the relocation time. The method may comprise receiving one or more of: information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from the user equipment to the first application server; or information relating to an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server providing the service to the user equipment to the second application server providing the service to the user equipment. The method may comprise stopping sending traffic to the first application server at the relocation time at or a time prior to the relocation time. The method may comprise determining the time prior to the relocation time based on the relocation time and the uplink traffic transmission delay. The method may comprise causing the traffic which has been stopped from being sent to be subsequently sent to the second application server. The method may comprise buffering the traffic which the user equipment has stopped from being sent to the first application server and means for causing the traffic which has been buffered to be sent to the second application server at or after the relocation time. The traffic which has been buffered to be sent to the second application server may be sent at a time based on the relocation time and the application context relocation duration. The method may comprise stopping uplink communication with the first application server at a time based on the relocation time and the application context relocation duration, and to start uplink communication with the second application server at the time based on the relocation time and the application context relocation duration. The communicating with the second application server may be is at the relocation time. The application server and the relocation time may be received in a protocol data unit session modification command. The method may be performed by an apparatus. The apparatus may comprises a user equipment. According to another aspect, there is provided a control apparatus comprising: means for determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment; and means for causing the relocation time and an address of the second application server to be provided to at least one of: the one or more user equipment; or a session management function of a core network of a wireless communication system. The control apparatus may comprise means for determining one or more of: information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted between a respective user equipment and the first application server; or information relating to an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server providing the service to the one or more user equipment to the second application server providing the service to one or more user equipment. The control apparatus may comprise means for determining the relocation time in advance for a planned relocation of the application service from the first application server providing the service to the one or more user equipment. The control apparatus may provide or host an application function. According to another aspect, there is provided a control 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 apparatus at least to perform: determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment; and causing the relocation time and an address of the second application server to be provided to at least one of: the one or more user equipment; or a session management function of a core network of a wireless communication system. According to another aspect, there is provided a method comprising: determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment; and causing the relocation time and an address of the second application server to be provided to at least one of: the one or more user equipment; or a session management function of a core network of a wireless communication system. The method may comprise determining one or more of: information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted between a respective user equipment and the first application server; or information relating to an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server providing the service to the one or more user equipment to the second application server providing the service to one or more user equipment. The method may comprise determining the relocation time in advance for a planned relocation of the application service from the first application server providing the service to the one or more user equipment. The method may be performed by a control apparatus. The control apparatus may provide or host an application function. According to another aspect, there is provided an apparatus, the apparatus comprising: means for receiving information about a second application server and a relocation time, wherein the said relocation time is a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to the one or more user equipment; and means for determining a first action rule, said first action rule being a first uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the second application server with a first uplink forwarding action rule activation time based on the relocation time. The apparatus may comprise means for determining a second action rule, the second action rule being a downlink forwarding action rule for the forwarding downlink traffic received from the second application server to the one or more of the user equipment with a downlink forwarding action rule activation time of the relocation time. The apparatus may comprise means for determining a deactivation time for a third action rule, the third action rule being a second uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the first application server with a deactivation time based on the relocation time. The apparatus may comprise means for receiving an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server to the second application server. One or more of the deactivation time and the first uplink forwarding action rule activation time may be based on the relocation time and the application context relocation duration. The apparatus may comprise means for determining a fourth action rule, the fourth action rule being an uplink buffering action rule for buffering of traffic associated with one or more of the one or more user equipment with an activation time and a deactivation time based on the relocation time. The apparatus may comprise means for sending one or more of the action rules to one or more of apparatus providing a user plane function serving a packet data unit session of one or more of the one or more user equipment. The apparatus may comprise means for sending the one or more of the said determined forwarding action rules to the one or more apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment at the relocation time or prior to the relocation time. The apparatus may comprise means for determining if one or more of the apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment is capable of supporting deferred action rules and when it is determined that one or more of the apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment is not capable of supporting deferred action rules, providing one or more of the one or more deferred action rules to the one or more of the apparatus providing the user plane function serving the packet data unit session, at a respective activation time or deactivation time of the respective deferred action rule. The apparatus may provide a session management function. According to another aspect, there is provided an apparatus, 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 apparatus at least to perform: receiving information about a second application server and a relocation time, wherein the said relocation time is a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to the one or more user equipment; and determining a first action rule, said first action rule being a first uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the second application server with a first uplink forwarding action rule activation time based on the relocation time. According to another aspect, there is provided a method comprising: receiving information about a second application server and a relocation time, wherein the said relocation time is a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to the one or more user equipment; and determining a first action rule, said first action rule being a first uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the second application server with a first uplink forwarding action rule activation time based on the relocation time. The method may comprise determining a second action rule, the second action rule being a downlink forwarding action rule for the forwarding downlink traffic received from the second application server to the one or more of the user equipment with a downlink forwarding action rule activation time of the relocation time. The method may comprise determining a deactivation time for a third action rule, the third action rule being a second uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the first application server with a deactivation time based on the relocation time. The method may comprise receiving an application context relocation duration indicating a time interval required to relocate an application context for the application service from the first application server to the second application server. One or more of the deactivation time and the first uplink forwarding action rule activation time may be based on the relocation time and the application context relocation duration. The method may comprise determining a fourth action rule, the fourth action rule being an uplink buffering action rule for buffering of traffic associated with one or more of the one or more user equipment with an activation time and a deactivation time based on the relocation time. The method may comprise sending one or more of the action rules to one or more of apparatus providing a user plane function serving a packet data unit session of one or more of the one or more user equipment. The method may comprise sending the one or more of the said determined forwarding action rules to the one or more apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment at the relocation time or prior to the relocation time. The method may comprise determining if one or more of the apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment is capable of supporting deferred action rules and when it is determined that one or more of the apparatus providing the user plane function serving the packet data unit session of the one or more of the one or more user equipment is not capable of supporting deferred action rules, providing one or more of the one or more deferred action rules to the one or more of the apparatus providing the user plane function serving the packet data unit session, at a respective activation time or deactivation time of the respective deferred action rule. The method may be performed by an apparatus. The apparatus may provide a session management function. According to another aspect, there is provided an n apparatus, 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 apparatus at least to perform: receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to one or more of the one or more user equipment; and sending the address of the second application server and the relocation time to one or more of the one or more user equipment. According to another aspect, there is provided an apparatus comprising: means for receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to one or more of the one or more user equipment; and means for sending the address of the second application server and the relocation time to one or more of the one or more user equipment. According to another aspect, there is provided a method comprising: receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to one or more of the one or more user equipment; and sending the address of the second application server and the relocation time to one or more of the one or more user equipment. According to a further aspect, there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform any of the methods set out previously. According to a further aspect, there is provided a computer program comprising instructions, which when executed cause any of the methods set out previously to be performed. According to an aspect there is provided a computer program comprising computer executable code which when run cause any of the methods set out previously to be performed. According to an aspect, there is provided a computer readable medium comprising program instructions stored thereon for performing at least one of the above methods. According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions which when executed by an apparatus, cause the apparatus to perform any of the methods set out previously. According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions which when executed cause any of the methods set out previously to be performed. According to an aspect, there is provided a non-volatile tangible memory medium comprising program instructions stored thereon for performing at least one of the above methods. In the above, many different aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above. Various other aspects are also described in the following detailed description and in the attached claims. Description of Figures Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which: Figure 1 shows an overview of some embodiments; Figure 2 shows a schematic representation of a 5G system; Figure 3 shows a schematic representation of an apparatus which may implement a respective network function of Figure 2; Figure 4 shows a schematic representation of a user equipment (UE); Figure 5 shows an example where a first application server and a second application server are provided in an edge data network; Figure 6 shows a first example procedure of some embodiments; Figure 7 shows a second example procedure of some embodiments: Figure 8 shows a third example procedure of some embodiments; Figures 9a and 9b show a fourth example procedure of some embodiments; Figure 10 schematically shows an example of edge application server relocation procedure where a session management function (SMF) sends a command to a UE; Figure 11 shows a first method of some embodiments; Figure 12 shows a second method of some embodiments; Figure 13 shows a third method of some embodiments; and Figure 14 shows a fourth method of some embodiments. Detailed description Some embodiments relate to the providing of a service by an application server. The service may be provided to one or more user equipment. Alternatively or additionally, the service may be provided to one or more network functions in a core network of a communications system. The core network may be a 3GPP core network. The application server may be part of the core network, the application server may be located in an edge data network, or the application server may be deployed in a cloud data network. Relocation of the service from a first application server providing the service to a second application server may be required. This means that the service that was provided by the first application server continues to be provided by the second application server after the relocation, while continuing to ensure continuity of the service wherever possible. Both the first application server and the second application server may be part of the core network. Alternatively, both the first application server and the second application server may be part of the edge data network. Alternatively, both the first application server and the second application server may be part of the cloud data network. Alternatively, the first application server and the second application are part of different ones of the core network, the edge data network, or the cloud data network. Some embodiments relate to relocation from the first application server (e.g., the service being provided by the first application server) to the second application server when the relocation of the service is planned rather than relocating the service reactively to changes in, for example, mobility of a user equipment of the one or more user equipment the first application server is providing the service to, changes in a load of the first application server, or for load balancing reasons. For example, for energy efficiency (EE), the first application server may be planned to be put into an energy-saving mode at time periods where there is low utilization of the first application server to reduce the number of application servers in use at the core network, the data network, or the cloud data network. For example, an edge computing (EC) provider may plan for the relocation of a first edge application servers (EAS) or a first application server (AS) to free up some physical servers at low-utilization time periods and to put those latter servers into an energy-saving mode. In some embodiments, the first application server which uses a brown energy source may be put in an energy saving mode. This may be when the second application server, which is using a greener or green energy source, is available. This may be to reduce brown energy usage by switching to the second application server which is using greener energy. This may be predicted or planned for. In some embodiments, the use of brown energy by the first application server may be only at certain times of day and it is planned to switch to the second application server when the first application server is using the brown energy. In some embodiments, the second application server in a different location using greener energy may be predicted to have a lighter load (for example due to a different time zone) at certain periods of time during the day. The service may be switched to the second application server during the periods where the second application server is predicted to have a lighter load. In another example, there may be plans to put the first application server into a maintenance mode at a planned time. This is to free up the first application server for maintenance. In another example, patterns, for example in application server load, can be predicted. Based on the prediction for the load pattern, it can be determined that the service needs to be relocated, at a relocation time, from the first application server to the second application server. Generally, the predictions become more accurate the closer it is to the planned relocation time. Currently, relocation from a first application server to a second application server is carried out when a trigger condition is met, using an asynchronous procedure, that is responsive to the trigger condition. In an asynchronous procedure, two signaling entities are not synchronized in time. Thus, the two signaling entities have to synchronize their respective operations (in time) using signaling messages -e.g. request, acknowledgement. The time of some of the relocations from a first application server to a second application server can be predicted and / or known in advance. However, in some circumstances, the number of planned relocations between different application servers may be relatively high and / or in within a relatively small time window. Using asynchronous procedures for the relocations between different application servers may result in a relatively high number of signaling messages being exchanged between different control plane entities during a relatively small time window. In some embodiments, the relocation from the first application server to the second application server uses a synchronous procedure. In a synchronous procedure, two signaling entities are synchronized in time (i.e. the two signaling entities have the same time epoch and they are syntonized, meaning time advances with the same pace in the two entities). Thus, two signaling entities using a synchronous procedure may not need to synchronize their respective operations (in time) using signaling messages. Some embodiments may reduce the signaling message exchanges required for the relocation from the first application server to the second application server as compared to asynchronous procedures. In general, asynchronous procedures when there is high amount of relocation may not be efficient. In some embodiments, the times of some of the relocations are known in advance, and the relocations may be planned in advance. This may reduce the burden on the network in a given time period or window when the relocations are carried out. For example, in some embodiments, this may reduce the number of signaling messages between the UE and the first and / or second application servers required to relocate the service. For example, in some embodiments, the number of signaling messages required between different administrative domains - for example a 5GS (5G system) and an edge data network (in the case that one or more of the first and second application servers is in the edge data network) may be reduced. In some embodiments, preparation for the relocation can take place prior to the relocation time. This may result in lower latency. In some embodiments, the need for buffering at one or more entities may be avoided. In some embodiments, packet loss during the service relocation may be avoided or reduced. In some embodiments, a common time reference is used by the first and second application servers as well as the core network (e.g., a 5GC (5G core)) such that time synchronization is possible. For example, some embodiments may use the time distribution of GPS (global position system) to provide a common time reference. This may provide a time synchronisation of sub-microsecond accuracy (e.g., from 1 to 10 ns accuracy). Some embodiments may be used with a less accurate time synchronization. Some embodiments may be used with any suitable common time reference providing time synchronization. Reference is made to Figure 1 which shows a simplified overview of some embodiments. A UE 300 is provided with an application client 402 for a service provided by a first application server 404. The application client 402 is provided by least one processor and at least one memory storing instructions that, when executed by the at least one processor provide the application client. The service is to be relocated from the first application server 404 to a second application server 406. Communication between the UE 300 and the first and second application servers 404 and 406 is via a core network 400. The core network may be for example a 3 GPP core network such as 5G core network (5GC). One or more of the first and second application servers may be part of the core network. In other embodiments, one or more of the first and second application servers may be in an edge data network. In other embodiments, one or more of the first and second application servers may be in a cloud data network. In the following, some example embodiments are provided at least in part by a 5G system. However, embodiments may be used in other systems as well as future systems. Figure 2 shows a schematic representation of a communication system operating based on a 5th generation radio access technology (generally referred to as a 5G system (5GS)) and with which some embodiments may be implemented. The 5GS may comprise a (radio) access network (RAN) or more generally a 5G access network that may e.g. correspond to a (radio) access network (RAN), to a wireline access gateway (W-AGF), to a N3IWF (non 3GPP interworking function), etc. The5GS may comprise a 5G core network (5GC), one or more application functions (AF) and one or more data networks (DN). The user equipment (UE) 300 may access or connect to the one or more DNs via the 5GS. The 5GC is one example of the core network 400 of Figure 1. The AF of Figure may be a CP (control plane) part of an application that can request to get information from 5GC or to set information in the 5GC. An enabler application server (E)AS may be the user plane part of the application that interacts with the UE. The same apparatus or different apparatus may provide the EAS and the AF. This will be described in more detail below. The 5G (R)AN may comprise one or more base stations or radio access network (RAN) nodes, such as a gNodeB (gNB). A base station or RAN node may comprise one or more distributed units connected to a central unit. The 5GC may comprise various network functions, such as an access and mobility management function (AMF), a session management function (SMF), an authentication server function (AUSF), a user data management (UDM), a user plane function (UPF), a network repository function (NRF), a network exposure function (NEF), a service communication proxy (SCP), edge application server discovery function (EASDF), policy control function (PCF), network slice access control function (NSACF), network slice specific authentication and authorization function (NSSAAF), and / or network slicing selection function (NSSF). Figure 3 illustrates an example of an apparatus 200. The apparatus 200 may comprise or implement one or more of the network functions shown in Figure 2 or an edge enabler server shown in Figure 5. In this example, the apparatus 200 may comprise at least one random access memory (RAM) 211a, and / or at least one read only memory (ROM) 211b. The apparatus 200 may also comprise at least one processor 212, 213 and / or a network interface 214. The at least one processor 212, 213 may be coupled to the at least one memory which in this example is the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215 (e.g., instructions of the software code 215). The software code 215 may, for example, include software code of one or more of the network functions shown in Figure 2, which allows the apparatus 200 to perform one or more operations of one or more of the present aspects. Execution of the software code (e.g., instructions of the software code 215 causes the apparatus 200 to perform one or more operations of one or more of the present aspects. Figure 4 illustrates an example of a communication device 300 or UE. The communication device 300 may be any device capable of or configured for sending and receiving signals. The communication device may be a wireline device or a wireless device. Where the communication device is a wireless device, the signals may be wireless signals such as radio signals. The communication device 300 may comprise 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, a machine-type communications (MTC) device, a Cellular Internet of things (CIoT) device or any combinations of these or the like. The communication device may be an XR (extended reality) device such as a headset or may be capable of supporting an XR application (e.g., capable of executing or running an XR application). The headset may be a VR headset. The communication device may be or part of a vehicle, a UAV, or a AVV. The communication device 300 may be a user equipment, such as the user equipment shown in Figure 1 or 2. The communication device 300 may be configured to send or receive wireless signals, for example, radio signals carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on. Where the communication device 300 is a wireless device, the communication device may be configured to send and / or receive wireless signals, for example, radio signals, over an air or radio interface 307 via a transceiver apparatus 306. The transceiver apparatus 306 may comprise, for example, a radio part and associated antenna arrangement. The radio part may convert the base band signal to the radio frequency and / or vice versa. The antenna arrangement may be arranged internally or externally to the mobile device and may include a single antenna or multiple antennas. The antenna arrangement may be an antenna array comprising a plurality of antenna elements. The communication device 300 may comprise at least one processor 301, and / or at least one memory. The at least one memory may be at least one ROM 302a, and / or at least one RAM 302b. Other possible components 303 may be provided for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access networks, such as the 5G RAN 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 instructions of software code 308. Execution of the instructions of the software code 308 may for example allow the communication device 300 to perform one or more operations. The software code 308 may be stored in the ROM 302a. It should be appreciated that in other embodiments, any other suitable memory may be alternatively or additionally used. The at least one processor 301, the at least one ROM 302a, and / or the at least one RAM 302b can be provided on an appropriate circuit board, in an integrated circuit, and / or in chipsets. This feature is denoted by reference 304. The communication device 300 may optionally have a user interface such as keypad 305, touch sensitive screen or pad, combinations thereof or the like. Optionally, the communication device may have one or more of a display, a speaker and a microphone. In the following examples, the term UE or user equipment is used. This term encompasses any of the example of communication device 300 previously discussed and / or any other communication device. Reference is made to Figure 5 which shows an example where the first and second application servers 404 and 406 are located in an edge data network 502. The example shown in Figure 5 is based on 3GPP TS 23.558 VI8.2.0 (2023-03) which relates to the enabling of edge applications over 3GPP networks. However, other embodiments may be used with other standards or where the application servers are provided other than in an edge data network. The edge data network comprises one or more edge enabler servers (EES) 504, and one or more edge application servers (EASs) 404 / 406. The first and second application servers are EAS’s in this example. In some embodiments, the first EAS 404 may be associated with a first EES 504 and the second EAS 406 may be associated with a second EES. In other embodiments, the first EAS 404 and the second EAS may be associated with the same EES. The UE 300 comprises the application client 402 and an edge enabler client EEC 500. The EEC 500 is provided by least one processor and at least one memory storing instructions that, when executed by the at least one processor provide the EEC 500. An edge configuration server (ECS) 506 is provided. The address of the ECS may be pre-configured on the UE or communicated to the UE. This may be as described in TS 23.558. The EEC 500 uses the ECS 506, to discover the different EES 504. Application data traffic is provided to the application client 402 from one of the first and second application servers (one of the EASs 404 / 406). Application data traffic is provided by the application client 402 to one of the first and second application servers (one of the EASs 404 / 406) . A first interface EDGE-1 is provided between the EES 504 and the EEC 500. A second interface EDGE-2 is provided between the EES 504 and the core network 400. A third interface EDGE-3 is provided between the EES 504 and the EAS 404 / 406. A fourth interface EDGE-4 is provided between the ECS 506 and the EEC 500. A fifth interface EDGE-5 is provided between the application client 402 and the EEC 500. A sixth interface EDGE-6 is provided between the EES 504 and the ECS 506. A seventh interface EDGE-7 is provided between the EAS 404 / 406 and the core network 400. An eighth interface EDGE-8 is provided between the ECS 506 and the core network 400. A ninth interface EDGE-9 is provided between two EESs 504. These EDGE interfaces are, for example, described in 3GPP TS 23.558 VI8.2.0 (2023-03) clause 6.2. The edge computing service provider of the edge data network via the edge enabler server (EES) 504 synchronizes relocation of a service provided by the edge application server EAS 404 / 406 to. The EES 504 may be regarded as an AF, such as shown in Figure 2. The EES 504 and / or AF may be hosted on an apparatus (e.g., a computing device or computing system), such as the apparatus 200. The edge computing service provider via the EES 504 synchronizes the relocation of a service provided by a first application server both at the application level and at the network level. The EAS 404 is the first application server. The synchronization of the relocation of the service provided by the first application server at both the application level and the network level maintains application service continuity and network service continuity. Thus, there will be a new (i.e., the second) application server that will provide the service, and 5GC will be prepared for the relocation of service provided by the first application server to the new application (i.e., second) application server. Additionally, the context of the session of the UE, which is relevant for the relocation of the service provided by the EAS 404 / 406 at the application level, should be migrated to the second application server. This allows for continuity of the service and the session. At the application level, the EES 504 provides, via the EDGE-1 interface, an application context relocation (ACR) time tl, and optionally other time-related parameters to the edge enabler client EEC 500 of the UE 300. The EEC 500 uses the ACR time tl, and optionally other time-related parameters, to program the ACR in advance of the relocation of the service. The EEC 500 also receives an internet protocol (IP) address of the target EAS (generally referred to as target EAS IP address) from the EES 504. The target EAS (T-EAS) 406 is the second application server. At the network level, the EES 504 sends, e.g., via the EDGE-2 interface, the EAS relocation time tl, optionally other time-related parameters, and the target EAS IP address to the core network 400. The EAS relocation duration (that is the duration or time interval required to relocate from the first application server to the second application server) includes the ACR duration, and optionally the initialization-and-configuration duration of T-EAS 406. As some embodiments relate to planned relocation procedures, the latter duration (i.e., initialization and configuration duration of the T-EAS 406) may be executed in advance. Thus, in this document, the EAS relocation duration may be considered to be the same as the ACR duration (referred to as R). In the following example, the AF and / or EES provides instructions to the UE via the EDGE-1 interface. The instructions are for deferred ACR actions on the UE. These actions are buffering and / or un-buffering actions. In this example, the UE has EDGE-1, EDGE-4 and EDGE-5 interfaces, as previously discussed. In some embodiments, the EDGE-1 interface is configured to allow the EES 504 to provide one or more of the following information to the EEC 500: - target EAS 406 IP address (that is the IP address of the second application server); - optionally the target EES IP address (that is the IP address of the EES 504 in embodiments where the respective EESs of the first and second application servers are different); - optionally an edge computing service provider identifier to differentiate between different 3rd party EES deployments and avoid any IP address conflicts between different EESs associated with different edge computing service providers; - relocation time tl (for example in UTC (coordinated universal time)) indicating a future time tl when the application server needs to be relocated to the target EAS (second application server). The relocation time tl may be later than the current time, for example after the relocation time has been received by the EEC 500; - optionally, an uplink (UL) communication delay dl between the UE and the source EAS (S-EAS) (that is the first application server), or an average uplink (UL) communication delay dl between a group of UEs and the S-EAS, or a maximum uplink (UL) delay dl between a group of UEs and the S-EAS; and - optionally an estimation of the ACR duration R. Based on the received information, the UE (triggered by the EEC 500) relocates the source EAS (S-EAS) (first application server) to the target EAS (T-EAS) (second application server) at the scheduled relocation time tl. This may follow the procedure of the 3GPP SA6 specification (TS 23.558 Figure 8.8.2.3-1: EEC executed Application Context Relocation (ACR)). In some embodiments, the EDGE-6 and / or EDGE-9 interfaces may be modified. The EDGE-6 and / or EDGE-9 interfaces may be configured to allow tl (in UTC) to be conveyed. Reference is made to Figure 6 which illustrates an example procedure of a first example for relocation of a service provided by a first application server to a second application server. The procedure for relocation of a service provided by a first application server to a second application server shown Figure 6 involves Application Context Relocation (ACR). The procedure shown in Figure 6 has a first phase, phase I when an ACR decision is made. As referenced 1, a control entity of the edge data network, such as source EES 504 (S-EES) associated with the first application server (S-EAS 404), plans a relocation of a service provided by the first application server. In this example, the planned relocation of a service provided by the first application server (S-EAS 404) to a second application server (T-EAS 406) to allow for relocation of the application service context in the first application server (S-EAS 404) to the second application server, and the establishment of a session between the UE 300 and the second application server (T-EAS 406). The future time tl when a service provided by the first application server (S-EAS 404) needs to be relocated to the second application server (T-EAS 406) are generally referred to herein as relocation time. Optionally, the S- EES 504 can measure the UL communication delay dl between the UE and the source EAS (S-EAS 404). Optionally, the S- EES 504 can estimate the ACR duration R. The procedure shown in Figure 6 has a second phase, phase II for ACR preparation. As referenced 2, the S-EES 504 provides to the EEC 500 ACR parameter information, the ACR duration R, the relocation time tl, and the IP address of the target EAS (T-EAS) (generally referred to T-EAS IP address). Optionally, the S-EES 504 provides to the EEC 500 dl. As the T-EAS IP address has been provided, via the EDGE-1 interface, the EEC 500 does not need to perform a discovery procedure to discover the T-EAS 505. As referenced 3, the S-EES 504, having knowledge of the T-EAS IP address and the T-EES 504, communicates (e.g., sends or provides) the ACR parameter information to the T-EAS 406 at the T-EAS IP address. The procedure shown in Figure 6 has a third phase, phase III when ACR is executed (e.g., performed). As referenced 4, at time tl-dl-delta, the UEZEEC 300 / 500 stops sending UL traffic towards the S-EAS 404. The time UEZECC 300 / 500 stops sending UL traffic towards the S-EAS 404 may consider the UL transmission delay from the UE 300 to the S-EAS 404 so that transient packets of UL traffic are not lost before the relocation of the service to the T-EAS 406 occurs at the relocation time tl. The UEZEEC 300 / 500 buffers any unsent packets of UL traffic. Delta may be used in the determination of the time to stop sending UPL traffic towards the S-EAS 404 to account for synchronization inaccuracy between the UE 300 and the EES 504. A value of delta may be a known. In some embodiments, if the UL delay dl is not measured and provided by the S-EES 404 to the UE 300, the UE 300 can estimate UL delay dl by measuring the round-trip-delay to the S-EAS 404 and taking half of (e.g., dividing by two) the round-trip delay that is measured. As referenced 5, at t=tl, the EEC context is relocated from the S-EES 504 to the T-EES 505. Then ACR is performed to relocate the Application Context (AC) from the S-EAS 404 to the T-EAS 406. The EEC context is a set of data about EEC that resides in the EES. The procedure shown in Figure 6 has a fourth phase, phase IV where any clean up operations post ACR occur. The clean up operations include removing the AC from the S-SAS. As referenced 6, an ACR status update procedure is performed between the S-EAS 404 and the S-EES as described TS 23.558, clause 8.8.3.8 V18.3.0 (2023-06).As referenced 7,an ACR status update proceedure is performed between the T-EAS 406 and the T-EES 505. As referenced 8, at time t=tl+R+delta, the UEZEEC 300 / 500 sends UL traffic that has been buffered since the part of the procedure referenced 4. In the example procedure shown in Fig. 6, an amount of signalling (e.g., the number of control plane signalling or messages) sent between the UEZEEC and an AF (represented by the S-EES, the T-EES or and / or ECS) to relocate a service provided by a first application server (e.g., the S-EAS) to a second application server (e.g., T-EAS) may be reduced. In some embodiments, where R is not provided by the AF / S-EES, the UEZEEC will recover UL traffic when an ACR complete notification signal or message is received from AFZEES. The ACR complete notification indicates the completion of ACR. This provides a semi-synchronous procedure for relocation of a service from the S-S. A second example of a procedure for relocation of a service provided by a first application server to a second application server will now be described. In this example, reference is made to an AF, such as shown in Figure 2. The AF provides a similar function as the EES in the previous example. The AF may be part of the edge computing environment. In this example, the AF is configured to provide some information to the 5GC which may be used by the 5GC to determine the deferred actions and / or rules for one or more entities of the 5GC. The AF is provided with and hence has knowledge of one or more of the following: - the relocation time tl (e.g., in UTC); and - the duration of EAS relocation (equal to ACR duration R when the application is stateful). Reference is made to Figure 7 which illustrates a second example procedure for relocation of a service provided by a first application server to a second application server. In particular, the procedure shown in Figure 7 is a synchronous procedure for relocation of a service provided by a first application server to a second application server. In the example procedure shown in Figure 7, the first and second application servers are not shown. In this example, the first and second application servers may be EASs or any other suitable application servers. As referenced 1, the AF communicates (e.g., provides or sends to) the 5GC the relocation time tl and the ACR duration R to the NEF. The relocation time tl and ACR duration R may be as previously described. In this example, the AF communicates (e.g., provides or sends) the relocation time tl and the ACR duration R to the NEF by including the relocation time tl and the ACR duration R in an updated Nnef TrafficInfluence that is sent to the NEF. As referenced 2, the AF communicates (e.g., sends or provides) to UE ACR information including relocation time tl, ACR duration R, dl and the T-EAS address to the UE. This communication of ACR information from the AF to the UE is described in relation to the part of the procedure referenced 2 of Figure 6. As referenced 3-5, the 5GC stores the received time parameters i.e., tl, R and updates this information into the UDR (unified data repository). The information is notified by UDR to the PCF. As referenced 6, PCC (policy and charging control) rules are provided to the SMF by the PCF that includes time parameters tl and R. As referenced 7, the SMF configures a DL deferred FAR (forward action rule) to forward traffic from the T-EAS to the UE. The related activation time for the DL deferred FAR is set to tl. It should be appreciated that the synchronization inaccuracy may not be significant with respect to the EAS location duration. This rule is sent to the UPF. As referenced 8, the SMF configures an UL deferred FAR to forward traffic from the UE to the T-EAS with the activation time being tl+R. This rule is sent to the UPF. As referenced 9, the SMF configures a deferred deactivation of a UL FAR which is forwarding traffic from the UE to the S-EAS with the deactivation time being tl+R. This rule is sent to the UPF. Although not shown, the part of the procedure referenced 4 of Figure 6 will be performed by the UE at time tl-dl-delta. As referenced 10, when the time is time tl, the DL deferred FAR to forward traffic from the T-EAS to the UE is activated on the UPF. As referenced 11, when the time is tl, the relocation from the S-EAS to the T-EAS is started. The part of the procedure referenced 11 and 12 occur (e.g., take place) at the same time. As referenced 12, the EAS relocation is completed. The relocation may be as described in relation to the previous example. As referenced 13, when the time is time tl+R, the UPF activates the UL FAR to forward traffic from the UE to the T-EAS and the UPF deactivates UL FAR which is forwarding traffic from the UE to the S-EAS. Although not shown, the part of the procedure referenced 8 of Figure 6 will be performed by the UE at time tl+R + delta. The parts of the procedure referenced 1 to 9 can be planned by the AF to occur (e.g., take place) well in advance of the parts of the procedure referenced 10 to 13. In some embodiments, the forwarding may not be directly from the UPF that receives rules related to forwarding (e.g., UL and DL FAR) to the respective application server. The forwarding may be from the UPF that receives the rule to another UPF where the other UPF forwards directly to the application server. In this example, buffering rules are not required on the UPF as the stopping of UL traffic is performed by the UE / EEC. There may be buffering of UL traffic on the UE and this may be as described in relation to the first example. In this example, the SMF may need to verify if the UPF can execute deferred actions. This may be based on an indication available in the UPF Profile in the NRF. The SMF may retrieve a list of UPF profiles and select an appropriate UPF. In some embodiments, if the UPF does not support deferred actions, then the SMF may: - manage the different times and time durations. In this latter case, the SMF sends action rules to the UPF at respective time instants in the parts of the procedure referenced 10 and 13; or - perform relocation to an UPF PSA (PDU (protocol data unit) session anchor) with the capability to execute deferred actions. The second example procedure for relocating a service provided by a first application server to a second application server may reduce signalling between the 5GC (represented by the SMF or the NEF) and the edge computing network (represented by the AF) at a relocation time tl. A third example of a procedure for relocation of a service (or services) provided by a first application server to a second application server will now be described. In this example, the AF has knowledge of: - the relocation time instant tl (e.g., in UTC); - the relocation duration R (this duration could include the ACR duration in case the application is stateful - this may be as described in relation to example 1); and - the one-way delays from the UPF to the EAS via the N6 interface - d2. In this example, the SMF configures deferred action rules based on one or more of tl, R and d2 as will be described in more detail below. Reference is made to Figure 8 which illustrates an example procedure of the third example for relocation of a service provided by a first application server to a second application server. In particular, synchronous signalling and operations performed by an AF and a UPF of a 5GC for relocation of a service provided by the first application server to the second applcation server are shown in Figure 8. In the example procedure shown in Figure 8, the first and second application servers are not shown. In this example, the first and second application servers may be EASs or any other suitable application servers. As referenced 1, the AF communicates to the 5GC tl, R, and d2. In this example, the AF provides tl, R, and d2 to the NEF. As referenced 2 to 4, the 5GC stores tl, R, d2 and updates the subscriber database in the UDR and the policy rules in PCF with adding pre-determined service relocation information (e.g., tl, R, d2). As referenced 5, PCC (policy and charging control) rules generated by the PCF and sent to the SMF. The PCC rules incudestl, R and d2. As referenced 6, the SMF configures an UL BAR (buffering action rule) with an activation time t=tl-d2-delta. The activation time t is the UL transmission delay d2 from the UPF to the S-EAS via the N6 interface so as to not have UL transient packets dropped before the relocation time tl. The delta value is introduced to address synchronization inaccuracy between the 5GC and the AF. As referenced 7, the SMF configures a DL deferred FAR (forward action rule) to forward traffic from the T-EAS to the UE. The related activation time for the DL deferred FAR is set to tl. It should be appreciated that the synchronization inaccuracy may not be significant with respect to the EAS location duration. This rule is sent to the UPF. As referenced 8, the SMF generates an UL deferred FAR to forward traffic from the UE to the T-EAS with the activation time being tl+R. The UL deferred FAR rule is sent by the SMF to the UPF. As referenced 9, the SMF configures a deferred deactivation of a UL FAR which is forwarding traffic from the UE to the S-EAS with the deactivation time being tl+R. This rule is sent to the UPF. As referenced 10, the SMF configures the deferred deactivation of the previous UL BAR (of the part of the procedure referenced 6) at time (tl+R+delta). Alternatively, the SMF may program or configure, a validity timer for the deactivation time of the UL BAR as: (tl+R+delta)-(tl-d2-delta) = R+d2+2*delta. As referenced 11, at time t=tl-d2-delta, UL buffering is activated on the UPF. As referenced 12, at time tl, the DL deferred FAR to forward traffic from the T-EAS to the UE is activated by the UPF. As referenced 13, when the time is tl, the relocation of a service provided by the S-EAS to the T-EAS is started. The parts of the procedure referenced 13 and 14 occur (e.g., take place) at the same time. As referenced 14, the EAS relocation is completed. The relocation of a service provided by the first application server to the second application server may be as described in relation to the previous examples. As referenced 15, when the time is time tl+R, the UL FAR to forward traffic from the UE to the T-EAS is activated on the UPF and the UL FAR which is forwarding traffic from the UE to the S-EAS is deactivated on the UPF. As referenced 16, at time t=tl+R+delta or time+tl+R+2*delta, the uplink buffering is deactivated by the UPF. The parts of the procedure referenced 1 to 11 may take well in advance of the later parts of the procedure. If R is not provided to the SMF, then the UL buffering deactivation may be performed when an end of relocation notification is received from the AF. For example, there may be a signaling message (e.g., a message sent) from the AF to the NEF to stop the buffering. For example, the signaling message (e.g., the message sent) may be a TrafficInfluence AppRelocationlnfo (Buffering off) message. The procedure would be then semi - synchronous. In this example, the SMF may need to verify if the UPF can execute deferred actions. This may be based on an indication available in the UPF Profile in the NRF. The SMF may retrieve a list of UPF profiles and select an appropriate UPF. In some embodiments, if the UPF does not support deferred actions, then the SMF may: - manage the different time instants and time durations. In this latter case, the SMF sends action rules to the UPF at respective time instants in steps 12 and 15. This is for example to activate and / or deactivate the UL buffering by the UPF, as required by the respective rule; or - perform relocation to an UPF PSA (PDU (protocol data unit) session anchor) with the capability to execute deferred actions. A fourth example will now be described. In this example, the AF provides information to the 5GC and UE (via 5GC). The AF may provide information to the 5GC either directly or via a NEF. This example is described with reference to Figures 9 and 10. To enable the AF to interact with the 5GC in order to relocate the application server at a pre-determined time, may require specific functionalities to be supported by one or more of the AF, the NEF, the SMF and the UDM and / or or UDR. Figures 9a and 9b show an example where the EAS relocation is triggered by the AF. In the example shown in Figure 9a and 9b, the AF interacts with the NEF to get access to the 5GC. The AF decides to relocate a service (or services) provided by a source EAS to the target EAS (e.g., due to associated data centre energy costs, a prediction of source EAS overload or to ensure running only some of the instances of the EAS (generally referred to as EAS instances) (e.g., during non-peak hours such as early-morning hours). The AF may in other embodiments decide to relocate a service provided by a source EAS to the target EAS based on different criteria. The AF may subscribe to the SMF by sending a subscription request to receive a notification when the SMF supports pre-determined EAS relocation (e.g., when the SMF is capable of or is configured for predetermined relocation) by sending a subscription request to the SMF. As described herein, relocation of a service provided by a first application server to a second application server includes EAS relocation and ACR. The AF may provide this subscription request to receive a notification from SMF to be applicable to any or all UEs served by source EAS. As referenced 900, the SMF subscribes to receive AF influence traffic routing request information. As referenced 1, the AF, based on internal trigger conditions, creates a request for EAS relocation. The request for EAS relocation comprises the target EAS IP address and a relocation time (in UTC) indicative of a time of relocation of a service (or services) provided by the EAS. As referenced 2, the request created by the AF includes information of an indication of a pre-determined EAS relocation, target DNAI (data network access identifier), traffic descriptor information and N6 routing information at the target DNAI, the target EAS IP address and the relocation time. The request is for example, provided to the NEF. The request may be a Nnef TrafficInfluence Create Request and / or the Nnef TrafficInfluence Update Request sent to the NEF, or NpcfPolicyAuthorizationCreate and / or Npcf PolicyAuthorization Update Request sent to the PCF. The information sent to NEF are the information elements specified in TS 23.501, TS 23.501, clause 5.6.7, table 5.6.7-1 V18.1.0 (2023-03) and includes additional information elements including an indication of pre-determined EAS Relocation, a time of relocation, a target EAS IP specified in the table below. The table below shows a portion of the information elements specified in table 5.6.7- 1 of clause 5.6.7 of V18.1.0 of TS 23.501 and new information elements including an indication of a pre-determined EAS relocation, target DNAI (data network access identifier), traffic descriptor information and N6 routing information at the target DNAI, the target EAS IP address and the relocation time. Information Name Applicable for PCF or NEF (NOTE 1) Applicable for NEF only Category Traffic Description Defines the target traffic to be influenced, represented by the combination of DNN and optionally S-NSSAI, and application identifier or traffic filtering information. The target traffic can be represented by AF- Service-Identifier, instead of combination of DNN and optionally S-NSSAI. Mandatory Potential Locations of Applications Indicates potential locations of applications, represented by a list of DNAI(s). The potential locations of applications can be represented by AF- Service-Identifier. Conditional (NOTE 2) ..... Indication of predetermined EAS Relocation Indicates that the target EAS needs to be used at time T (in UTC) Yes Added Time of relocation Time at which service provided by target EAS is to be relocated Yes added Target EAS IP Address of Target EAS IP address, to which the service provided by the application server is to be relocated, at the indicated time of relocation Yes added As referenced 3a, the NEF stores the traffic influence information with the indication of pre-determined EAS Relocation, the target EAS IP address and the relocation time (in UTC), together with other received information, in the UDR and the UDR provides a response to the request to NEF as referenced 3a. As referenced 3b, the NEF provides a response to the AF. The response provided by the NEF is a response to the request discussed in the part of the procedure referenced 2. Due to their respective subscriptions e.g., as discussed in relation to the part of the procedure referenced 900, the SMF and PCF receive notifications from UDR that includes information provided by AF. This is referenced as 902. As referenced 4a, 4b, 5a and 5b, these are same as explained in clause 4.3.6 of TS 23.502 i.e. notification messages corresponding to the subscriptions as referenced 0a, 0b-l, Ob-2 in figure 9a. As reference 4b, the UDR provides PCC rule information to PCF by for example, sending a Nudr DM Notify message to the PCF. The PCC rule information, shown in the table below, includes information elements specified TS 23.503, Table 6.3.1, which is referred to as a PCC rule information in 5GC and the following: an indication of predetermined EAS relocation; a time of relocation of the EAS; and a target EAS IP address (e.g., IP address of the target EAS). AF influenced Traffic Steering Enforcement Control This part describes information required for AF influenced Traffic Steering. Data Network Access Identifier Identifier(s) of the target Data Network Access (DNAI). It is defined in clause 5.6.7 of TS 23.501 [2], Yes Added Per DNAI: Traffic steering policy identifier Reference to a pre-configured traffic steering policy at the SMF Yes Added Per DNAI: N6 traffic routing information Describes the information necessary for traffic steering to the DNAI. It is described in clause 5.6.7 of TS 23.501 [2], Yes Added ..... Indication of predetermined EAS Relocation Indicates that the target EAS needs to be used at time T (in UTC) Yes Added Time of relocation Time at which service provided by target EAS is to be relocated Yes added Target EAS IP Address of Target EAS IP address, to which the service provided by the application server is to be relocated, at the indicated time of relocation Yes added As referenced 6a, the SMF can decide to send the target EAS IP address and relocation time to the UE via ePCO (extended protocol configuration options) as part of PDU Session update procedure. This is discussed in relation to the Figure 10. Alternatively, the EAS 5 replacement procedure may be used with SMF and AF interactions as specified in clause 6.3.3, TS 23.548. As referenced 6, the SMF configures PSA UPF for EAS relocation, at the relocation time. This may be as discussed in relation to the examples of Figures 7 or 8. As referenced 7, the SMF may decide whether it is required to send the target DNAI 10 or the common DNAI to the AMF for triggering SMF / I-SMF (intermediate SMF) (re) sei ection. This may be as defined in TS 23.502. As referenced 8, the SMF sends a PDU Session Modification Command to the UE. This command comprises the target EAS address, and the relocation time. The command indicates to the UE that there will be EAS relocation to target EAS at the provided relocation 15 time. The target EAS address and relocation time may be provided in the ePCO. The command may comprise an impact field which is used to identify for which EAS(s) information need to be replaced. Reference is made to Figure 10 which shows an example of edge application server relocation procedure where the SMF sends a command to the UE. In Figure 10, EAS rediscovery is triggered by AF or 5GC as shown in options referenced la and lb. The options referenced la and lb are alternatives. As referenced la, EAS rediscovery is triggered by 5GC due to the insertion or change or removal of Local-PDU Session Anchor or L-PSA. As referenced lb, EAS rediscovery is triggered by the AF. This may be for a planned relocation of the application servers. As referenced lb, the SMF receives target EAS IP address and time of relocation from the AF. As referenced 2, the SMF sends a PDU session modification command to the UE as described previously. The command comprises an EAS rediscovery indication and impact field to UE. The EAS rediscovery indication indicates to the UE to refresh the cached EAS information. The SMF additionally sends the time of relocation (as received in the AF traffic Influence Request). Some embodiments of the methods and apparatuses described herein allow for periodic or pre-planned relocation of a service provided by a first application server to a second application server. The first and second application servers in the examples previously discussed are EASs. However, this is by way of example only and the first and second application servers may be any other suitable applications servers. Some embodiments have the advantage that preparation steps before the planned relocation of a service (or services) provided by a first application server to a second application server may allow for a shortened actual duration for the relocation of the service (or services) to the second application server. This shortened EAS relocation duration may provide a better QoS (quality of service) to the UEs. The synchronous procedures for relocation of a service (or services) provided by a first application server to a second application server of some embodiments may minimize signaling (e.g., control plane message) exchanged between 5G Core Network Function e.g., SMF and AF and also between UE and EES. When the number of impacted UEs is large (e.g., hundreds of thousands, millions), the SMF may spread the programming of deferred actions over a large-enough time window to smooth out bursts of signalling (e.g., control plane message) to avoid a signaling (e.g., control plane message) avalanche at the relocation time tl. Having signaling (e.g., control plane message exchanges for EAS relocation) phase performed in advance and distributed over time, may ease the signaling burden between the AF and 5GC. Additionally, this allows AF to pre-plan its application server downtime e.g. due to energy saving and / or energy efficiency reasons and provide prior information of the same to 5GC, thus enabling 5GC to prepare in advance for application server relocation. The execution phase (e.g., actual EAS relocations and ACRs) may be performed for a relatively large number of application servers at the same time at the beginning of the maintenance window (i.e., time tl). This may provide good usage of the server resources. For example, physical servers to be put into maintenance mode are used in a normal mode right up to the maintenance window. When UE / EEC is programmed with (e.g., informed of or provided with) relocation time tl, some embodiments may avoid the need for buffering requirements at 5GC (e.g., at PSA UPF) while avoiding packet loss during the EAS relocation procedures. Reference is made to Figure 11 which shows a method of some embodiments. This method may be performed by an apparatus. The apparatus may a user equipment. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to Figure 4. The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced Al, receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to a user equipment to the second application server providing the service to the user equipment. The method may comprise as referenced A2, communicating with the second application server at a time, wherein the time is dependent on the relocation time. It should be appreciated that the method outlined in Figure 11 may be modified to include any of the previously described features. Reference is made to Figure 12 which shows a method of some embodiments. This method may be performed by a control apparatus. The control apparatus may provide an application function or EES function. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to Figure 3. The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced Bl, determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment, The method may comprise as referenced B2, causing the relocation time and an address of the second application server to be provided to at least one of: the one or more user equipment; or a session management function of a core network of a wireless communication system. It should be appreciated that the method outlined in Figure 12 may be modified to include any of the previously described features. Reference is made to Figure 13 which shows a method of some embodiments. This method may be performed by an apparatus. The apparatus may provide a session management function. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to Figure 3 The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced Cl, receiving information about a second application server and a relocation time, wherein the said relocation time is a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to the one or more user equipment. The method may comprise as referenced C2, determining a first action rule, said first action rule being a first uplink forwarding action rule for the forwarding uplink traffic received from one or more of the user equipment towards the second application server with a first uplink forwarding action rule activation time based on the relocation time. It should be appreciated that the method outlined in Figure 13 may be modified to include any of the previously described features. Reference is made to Figure 14 which shows a method of some embodiments. This method may be performed by an apparatus. The apparatus may provide a session management function or a user plane function. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to Figure 3 The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced DI, receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to the second application server providing the service to one or more of the one or more user equipment. The method may comprise as referenced D2, sending the address of the second application server and the relocation time to one or more of the one or more user equipment. It should be appreciated that the method outlined in Figure 14 may be modified to include any of the previously described features. Computer program code may be downloaded and stored in one or more memories of the apparatus described herein. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for communication systems operated by mobile network operators, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. In this example, some embodiments have been described in relation to a 5G system (5GS). As used herein, “at least one of the following: ” and “at least one of ” 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 the elements. In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure 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 the disclosure is not limited thereto. While various aspects of the disclosure 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 examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit(s) (such as only analog and / or digital circuit(s)) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog 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 a mobile phone or server, to perform various functions) 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 all uses of the term “means” in this application, including in any claims. As a further example, as used in this application, 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 and if applicable to the particular claim element, an integrated circuit such as a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device. The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Further in this regard it should be noted that any blocks of the logic flow as in the Figures 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 disks or floppy disks, and optical media such as for example, DVD and the data variants thereof, CD. The physical media is a non-transitory media. 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). 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 comprise one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples. Embodiments of the disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiments of this disclosure. 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 appended claims. Indeed, there are further embodiments comprising a combination of one or more embodiments with any of the other embodiments previously discussed. The scope of protection sought for some embodiments of the disclosure is set out by the claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the claims are to be interpreted as examples, useful for understanding various embodiments of the disclosure. It should be noted that different claims with differing claim scope may be pursued in related applications such as divisional or continuation applications.

Claims

1. A user equipment comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to perform at least:receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to the user equipment to the second application server providing the service to the user equipment;receiving information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from the user equipment to the first application server;determining, based on the relocation time and the uplink traffic transmission delay, a time prior to the relocation of the service from the first application server to the second application server;stopping sending uplink traffic to the first application server at the determined time prior to the relocation of the service; andcommunicating with the second application server at a time, wherein the time is dependent on the relocation time.

2. The user equipment as claimed in claim 1, wherein the instructions, when executed by the at least one processor, further cause the user equipment to perform receiving information relating to an application context relocation duration indicating a time interval required to relocate an application context for the service from the first application server providing the service to the user equipment to the second application server providing the service to the user equipment.

3. The user equipment of claim 1 or 2, wherein the instructions, when executed by the at least one processor, further cause the user equipment to perform sending, to the second application server, the uplink traffic which has been stopped from being sent to the first application server.

4. The user equipment of any preceding claim, wherein the instructions, when executed by the at least one processor, further cause the user equipment to perform:buffering uplink traffic which the user equipment has stopped from being sent to the first application server and;causing the uplink traffic which has been buffered to be sent to the second application server at or after the relocation time.

5. The user equipment of claim 4 when dependent on claim 2, wherein the uplink traffic which has been buffered to be sent to the second application server is sent at a time based on the relocation time and the application context relocation duration.

6. The user equipment as claimed in claim 2, wherein the instructions, when executed by the at least one processor, further cause the user equipment to perform: stopping uplink communication with the first application server at a time based on the relocation time and the application context relocation duration and starting uplink communication with the second application server at the time based on the relocation time and the application context relocation duration.

7. The user equipment of claim 1, wherein the communicating with the second applicationserver is at the relocation time.

8. The user equipment as claimed in any preceding claim, wherein the address of the second application server and the relocation time is received in a protocol data unit session modification command.

9. A control 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 apparatus at least to perform:determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment;determining an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from a respective user equipment to the first application server; andcausing information related to the uplink traffic transmission delay, the relocation time and an address of the second application server to be provided to at least one of: the one ormore user equipment; or a session management function of a core network of a wireless communication system.

10. The control apparatus as claimed in claim 9, wherein the instructions, when executed by the at least one processor, further cause the control apparatus to perform determining information relating to an application context relocation duration indicating a time interval required to relocate an application context for the service from the first application server providing the service to the one or more user equipment to the second application server providing the service to one or more user equipment.

11. The control apparatus as claimed in claim 9 or 10, wherein the instructions, when executed by the at least one processor, further cause the control apparatus to perform determining the relocation time in advance for a planned relocation of the application service from the first application server providing the service to the one or more user equipment.

12. A method comprising:receiving an address of a second application server and a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to a user equipment to the second application server providing the service to the user equipment;receiving information relating to an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from the user equipment to the first application server;determining, based on the relocation time and the uplink traffic transmission delay, a time prior to the relocation of the service from the first application server to the second application server;stopping sending uplink traffic to the first application server at the determined time prior to the relocation of the service; andcommunicating with the second application server at a time, wherein the time is dependent on the relocation time.

13. A method comprising:determining a relocation time, said relocation time being a time relating to relocation of a service from a first application server providing the service to one or more user equipment to a second application server selected to provide the service to the one or more user equipment;determining an uplink traffic transmission delay indicating a time for uplink traffic to be transmitted from a respective user equipment to the first application server; andcausing information related to the uplink traffic transmission delay, the relocation time and an address of the second application server to be provided to at least one of: the one or more user equipment; or a session management function of a core network of a wireless communication system.

14. A computer program product comprising computer executable instructions which when run cause the method of any of claims 12 or 13 to be provided.

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