Patent Description:
Especially in an industrial environment, safety critical functions or operational impact systems require redundant implementations. This includes protection from issues such as power outages, lightning strikes, tornadoes, earthquakes, and more. The risk of a general failure can be reduced by having components split over different locations and/or platforms. An example is the distribution of cloud servers (e.g. for providing web services) over multiple regions such that they are physically separated.

Within a <NUM> communication system, redundant paths between a radio access network and a user plane function may be established. Packets are duplicated and sent via the redundant paths. This is transparent to the mobile terminal. Another redundancy mechanism is that the mobile terminal establishes redundant paths and duplicates packets itself.

With the introduction of edge computing, in particular Multi-Access Edge Computing, redundancy mechanisms for protection against failure are similarly desirable in an edge scenario.

<CIT> discloses a mobile telecommunications network includes a core and a radio access network including control means operable to control the use of network resources by the mobile terminals. The control means may be provided at an access node site and/or a gateway site.

<CIT> discloses an Application Function (AF) influenced routing for peer-to-peer (P2P) communications is provided. Core network elements correlate PDU sessions and optimize the UP path for peer-to-peer traffic.

<CIT> discloses a data management and storage (DMS) cluster of peer DMS nodes manages data backup and disaster recovery using a service level agreement.

According to a first aspect of the present invention, a server computer of an arrangement of server computers according to claim <NUM> is provided.

According to a second aspect of the present invention, a method for providing an application to one or more mobile communication terminals according to claim <NUM> is provided.

According to a third aspect of the present invention, a mobile communication network according to claim <NUM> is provided.

According to a fourth aspect of the present invention, a method for providing one or more mobile communication terminals with access to a server computer of an arrangement of server computers according to claim <NUM> is provided.

Additional features for advantageous embodiments of the present invention are provided in the dependent claims.

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects of this disclosure in which the invention may be practiced. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention.

In the invention according to the first aspect, the notification interface may be configured to notify a user plane component of the mobile communication network (e.g. a user plane function or a radio access network (user plane) component) or a control plane component (e.g. an Operations, Administration and Maintenance component, a Unified Data Repository, a Unified Data Management, a Session Management Function and/or a Policy Control Function) of the mobile communication network about the other server computer.

In the invention according to the first aspect, the notification interface may be configured to notify the mobile communication network about an address, a location and/or quality of service information of the other server computer.

In the invention according to the first aspect, the predetermined quality level may be that the server computer can provide the application to the one or more mobile communication terminals at a predetermined quality of service.

In the invention according to the first aspect, the server computers of the arrangement of server computers are multi access edge computing hosts.

In the invention according to the first aspect, the server computers of the arrangement of server computers may be part of the mobile communication network.

In the invention according to the first aspect, the server computers of the arrangement of server computers may be part of the Internet.

The invention according to the second aspect may include notifying a core network component of the mobile communication network about another application server provided by the other server computer, wherein the mobile communication network may use the other application server as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at the predetermined quality level.

The invention according to the second aspect may include notifying a user plane component of the mobile communication network about the other server computer which the mobile communication network may use as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at a predetermined quality level.

The invention according to the second aspect may include notifying the mobile communication network that the other server computer may be synchronized with the server computer to be able to serve as backup for providing the application to the one or more mobile communication terminals.

The invention according to the second aspect may include notifying the mobile communication network that another application server of the other server computer may be synchronized with the application server to be able to serve as backup for providing the application to the one or more mobile communication terminals.

The invention according to the second aspect may include notifying a user plane component of the mobile communication network (e.g. a user plane function or a radio access network (user plane) component) or a control plane component (e.g. an Operations, Administration and Maintenance component, a Unified Data Repository, a Unified Data Management, a Session Management Function and/or a Policy Control Function) of the mobile communication network about the other server computer.

The invention according to the second aspect may include notifying the mobile communication network about an address, a location and/or quality of service information of the other server computer.

In the invention according to the second aspect, the predetermined quality level may be that the server computer can provide the application to the one or more mobile communication terminals at all.

In the invention according to the second aspect, the predetermined quality level may be that the server computer can provide the application to the one or more mobile communication terminals at a predetermined quality of service.

In the invention according to the second aspect, the server computers of the arrangement of server computers implement edge nodes.

In the invention according to the second aspect, the server computers of the arrangement of server computers may be multi access edge computing hosts.

In the invention according to the second aspect, the server computers of the arrangement of server computers may be part of the mobile communication network.

In the invention according to the second aspect, the server computers of the arrangement of server computers are part of the Internet.

In the invention according to the third aspect, the radio access network may be configured to store information from the notification about the other server computer of the arrangement of server computers as part of session context information of the one or more mobile communication terminals.

The invention according to the third aspect may include a detector configured to detect whether the server computer fails to provide the application at the predetermined quality level.

The invention according to the fourth aspect may include storing information from the notification about the other server computer of the arrangement of server computers as part of session context information of the one or more mobile communication terminals.

The invention according to the fourth aspect may include detecting whether the server computer fails to provide the application at the predetermined quality level.

In the invention according to the fourth aspect, the predetermined quality level may be that the server computer can provide the application to the one or more mobile communication terminals at all and wherein the method includes detecting whether the server computer can provide the application to the one or more mobile communication terminals at all by exchanging health check messages and health acknowledge messages with the server computer.

In the invention according to the fourth aspect, the predetermined quality level may be that the server computer can provide the application to the one or more mobile communication terminals at a predetermined quality of service and wherein the method includes detecting whether the server computer may provide the application to the one or more mobile communication terminals at the predetermine quality of service by exchanging quality of service status messages with the server computer.

The invention according to the fourth aspect may include controlling the radio access network to establish an inactive backup path to the other server computer for providing the application to the one or more mobile communication terminals and switching the backup path to active in case the server computer fails to provide the application at the predetermined quality level.

In the invention according to the fourth aspect, the notification may include information that the other server computer should be synchronized with the server computer to be able to serve as backup for providing the application to the one or more mobile communication terminals and the method may include synchronizing the server computer with the other server computer if the other server computer should be synchronized with the server computer to be able to serve as backup for providing the application to the one or more mobile communication terminals.

According to further aspects of the invention, a computer program and a computer readable medium including instructions, which, when executed by a computer, make the computer perform methods of claim <NUM> or <NUM> are provided.

In the following, various embodiments will be described in more detail.

<FIG> shows a radio communication system <NUM>, e.g. a <NUM> communication network as specified by 3GPP (Third Generation Partnership Project).

The radio communication system <NUM> includes a mobile radio terminal device <NUM> such as a UE (user equipment), a nano equipment (NE), and the like. The mobile radio terminal device <NUM>, also referred to as subscriber terminal, forms the terminal side while the other components of the radio communication system <NUM> described in the following are part of the mobile radio communication network side, i.e. part of a mobile (radio) communication network (e.g. a Public Land Mobile communication network PLMN). Furthermore, the radio communication system <NUM> includes a radio access network <NUM>, which may include a plurality of radio access network nodes, i.e. base stations configured to provide radio access in accordance with a <NUM> (Fifth Generation) radio access technology (<NUM> New Radio). It should be noted that the radio communication system <NUM> may also be configured in accordance with LTE (Long Term Evolution) or another radio communication standard (e.g. Wi-Fi) but <NUM> is herein used as an example. Each radio access network node may provide a radio communication with the mobile radio terminal device <NUM> over an air interface. It should be noted that the radio access network <NUM> may include any number of radio access network nodes.

The radio communication system <NUM> further includes a core network <NUM> including an Access and Mobility Management Function (AMF) <NUM> connected to the RAN <NUM>, a Unified Data Management (UDM) <NUM> (which may be paired with a Unified Data Repository (UDR)) and a Network Slice Selection Function (NSSF) <NUM>. Here and in the following examples, the UDM may further consist of the actual UE's subscription database, which is known as, for example, the UDR (Unified Data Repository). The core network <NUM> further includes an AUSF (Authentication Server Function) <NUM> and a PCF (Policy Control Function) <NUM>.

The core network <NUM> may have multiple network slices <NUM>, <NUM> and for each network slice <NUM>, <NUM>, the operator may create multiple network slice instances (NSIs) <NUM>, <NUM>. For example, the core network <NUM> includes a first core network slice <NUM> with three core network slice instances (CNIs) <NUM> for providing Enhanced Mobile Broadband (eMBB) and a second core network slice <NUM> with three core network slice instances (CNIs) <NUM> for providing Vehicle-to-Everything (V2X).

Typically, when a network slice is deployed, network functions (NFs) are instantiated, or (if already instantiated) referenced to form a network slice instance (NSI) and network functions that belong to a network slice instance are configured with a network slice instance identification.

Specifically, in the shown example, each instance <NUM> of the first core network slice <NUM> includes a first Session Management Function (SMF) <NUM> and a first User Plane Function (UPF) <NUM> and each instance <NUM> of the second core network slice <NUM> includes a second Session Management Function (SMF) <NUM> and a second User Plane Function (UPF) <NUM>.

The core network <NUM> may further include an NRF (Network Repository Function) <NUM>, which provides network function/network function service registration, network function/network function service discovery. The NRF may have an interface to any network function in the mobile radio communication network side, e.g. have an interface to the AMF <NUM>, the SMFs <NUM>, <NUM>. For simplicity, only the interface between the NRF <NUM> and the AMF <NUM> is depicted.

The radio communication system <NUM> may further include an OAM (Operation, Administration and Maintenance) function (or entity) <NUM>, e.g. implemented by one or more OAM servers which is connected to the RAN <NUM> and the core network <NUM> (connections are not shown for simplicity).

Further, the radio communication system <NUM> may include a NWDAF (Network Data and Analytics Function) <NUM>.

Edge Computing (EC) is a paradigm that allows distributing the computing power, networking and storage capabilities across the cellular network and closer to the mobile terminal. One example to realize the EC is via Multi-access edge computing (MEC) technology, formerly mobile edge computing, which is an ETSI-defined network architecture concept that enables cloud computing capabilities and an IT service environment at the edge of a cellular network such as the radio communication system <NUM>. The basic idea behind MEC is that by running applications and performing related processing tasks closer to a UE <NUM>, network congestion and latency are reduced and applications perform better. MEC technology may be implemented at cellular base stations (e.g. of RAN <NUM>) or other edge nodes, and enables flexible and rapid deployment of new applications and services for customers. Combining elements of information technology and telecommunications networking, MEC also allows cellular operators to open their radio access network (e.g. RAN <NUM>) to authorized third parties, such as application developers and content providers. Here, MEC is taken as an example, however, other technologies are available to implement edge computing mechanism e.g. KubeEdge.

<FIG> shows a communication arrangement <NUM> illustrating edge computing.

The communication arrangement <NUM> includes edge devices <NUM>, e.g. being each implemented by a UE corresponding to UE <NUM>.

The edge devices <NUM> are coupled via one or more RANs <NUM> (e.g. corresponding to RAN <NUM>) and via one or more UPFs <NUM> (e.g. corresponding to UPFs <NUM>, <NUM>) to an edge <NUM>, i.e. an arrangement of one or more edge nodes <NUM>.

Communication between a UE <NUM> and an edge node <NUM> is controlled and managed by the mobile communication network control plane, e.g. including an AMF <NUM>, an SMF <NUM>, <NUM>, a PCF <NUM> as well as a NEF (Network Exposure Function).

The edge <NUM> may be part of the mobile communication network including the RAN(s) <NUM> and UPF(s) <NUM> or may be separate from it. This may in particular mean that the edge <NUM> may be maintained by the same operator as the operator of the mobile communication network or may be maintained by another edge provider.

In any case, the edge nodes <NUM> are typically arranged geographically close to the RAN(s) <NUM>, e.g. closer than one or more cloud servers <NUM> (which may be part of the Internet). Nevertheless, the edge <NUM> may include multiple edge nodes <NUM> which are placed in different geographical locations (i.e. which are implemented by computers which are at different locations).

As illustrated for one of the edge nodes <NUM>, each edge node <NUM> implements a hosting environment <NUM> which embeds both an hosting platform (e.g. MEC platform) <NUM> and application servers <NUM> (also referred to as application functions, in particular according to <NUM> terminology). This means that an edge node <NUM> can be a MEC host environment. Each edge node <NUM> is for example identified by an N6 interface (interface between UPF and data network) and/or a DNAI (Data Network Access Identifier). Each edge node <NUM> is connected to a UPF <NUM> (e.g. an Anchor UPF or an Intermediate UPF). The UEs <NUM> may consume application services hosted on the edge nodes <NUM> (i.e. applications provided by application servers <NUM>) by means of a corresponding application client. Specifically, for consuming an application (i.e. using the application by means of a corresponding client on the UE), a UE <NUM> establishes a session with the corresponding (server-side) application <NUM>. So, the application server is communicating with mobile network components.

In case one application server <NUM> fails only one application will be impacted. In case the MEC platform <NUM> fails, all applications handled by the platform will be impacted.

For ensuring that a UE <NUM> may continue using an application (i.e. consuming the respective application service) even if an application server <NUM> or a MEC platform <NUM> fails, e.g. based on a business agreement, each edge node <NUM> may have one or more redundant edge nodes as illustrated in <FIG>.

<FIG> shows an edge node arrangement <NUM> where an edge node E2 (e.g. running a redundant application server A1') acts as redundant edge node for edge node E1 (e.g. running an application server A1) and edge nodes E2 acts as redundant edge nodes for edge node E3.

<FIG> shows a communication arrangement <NUM> where a UE <NUM>, e.g. corresponding to a UE <NUM>, may be connected via a RAN <NUM>, e.g. corresponding to a RAN <NUM>, with a first edge node E1 <NUM> and a second edge node E2 <NUM> which provide redundant application servers A1 <NUM> and A1' <NUM>.

The application server A1 <NUM> (hosted by the first edge node E1) and the application server A1' <NUM> (hosted by the second edge node E2) are redundant instances of an application server for an application client in the UE <NUM>. The edge nodes E1 and E2 are placed in different locations connected by a communication network.

In the following, approaches are described how the mobile communication network (e.g. a RAN <NUM> or a UPF <NUM>) detects that an application server (e.g. application server A1 <NUM>) has failed. Further, actions are described which are performed to swap the traffic (related to the application) after failure detection, e.g. from application server A1 <NUM> to application server A1' <NUM>.

It should be noted that a failure of an application server (e.g. A1) may be originated by a failure of the hosting platform or the whole edge node E1 <NUM>. In any case, from the mobile communication network viewpoint, the subject of the failure detection is the application server.

According to an embodiment, when an edge node (e.g. E1 in <FIG>) has a redundant edge node (e.g. E2), the edge node (e.g. an application server of the edge node) provides redundant edge details to the mobile communication network, in particular the mobile communication network's core network, as it is illustrated in <FIG>.

<FIG> shows a message flow diagram <NUM>.

A core network component <NUM> of a mobile communication network, e.g. the mobile communication network including RAN(s) <NUM> and UPF(s) <NUM>, and an application function <NUM>, e.g. of edge node E1 <NUM> or application server A1 <NUM> of <FIG>, are involved in the flow.

In <NUM>, the application function <NUM> (or generally the edge node, e.g. E1) sends an edge node profile "E1 profile" or an application profile "A1 profile" during the registering of the edge node or application with the mobile communication network.

The edge node profile includes one or more following:.

The application server profile includes one or more following:.

It should be noted that the mobile communication network pay perform discovery of a redundance edge node (e.g. E2 in case E1 or A1 fails) based on the other application server (e.g. A1') address (using domain name service (DNS)). Further, the interface between mobile communication network and application server can be transparent to the edge like a virtual point two point link.

In <NUM>, the core network component <NUM> acknowledges the registration.

<FIG> illustrates the fallback from an edge node E1 <NUM> to a redundancy edge node <NUM> in case of failure of the edge node E1 (e.g. a platform failure or an AF failure).

A UE <NUM> has a communication session with the application server A1 in the edge node E1 via a RAN <NUM> and a first UPF <NUM> for consuming an application provided by an AF A1 <NUM> of the edge node E1. The redundancy edge node <NUM> includes a corresponding AF A1' <NUM> for providing the application.

The UE <NUM> for example corresponds to UE <NUM>, the RAN <NUM> for example corresponds to RAN <NUM> and the edge nodes <NUM>, <NUM> for example correspond to edge nodes <NUM>, <NUM>.

The UE <NUM> has for example a PDU session with the application server A1 in the edge node E1 <NUM>.

During the establishment of the PDU session, the corresponding SMF (i.e. session controller) determines that the PDU session requires redundancy and thus that it needs to create active and backup paths for the session. The determination is for example based on the policies provided by PCF for the PDU Session, local redundant policy for DNN or alternatively DNAI or information provided by the OAM (e.g. configured policy in the SMF). For example, a PCF (i.e. policy manager) determines the session policy and charging policy based on the reliability profile of an edge or A1 profiles, after provides the reliability policy to the SMF (which it itself can be for example knows from the flow of <FIG>). Thus, based on E1's edge node profile or A1's profile, the SMF selects both the active UPF <NUM> as well as a backup UPF <NUM>. The SMF indicates the redundancy policy to the RAN <NUM> so that the RAN can create active and backup path tunnel information.

Thus, the SMF and the RAN <NUM> allocate both an active path (via UPF <NUM>) and a backup path (vie backup UPF <NUM>) for the session. The backup path is only established and is in sleep mode (not active) to save network resources until the edge node E1 fails. This situation, before failure of the edge node E1 (or AF A1 <NUM>) <NUM>, is illustrated on the top half of <FIG>.

The SMF may for example provide a reliability priority list to the RAN <NUM> during the PDU Session Establishment. An example is given in table <NUM>, wherein ARP refers to Allocation and Retention Policy.

The RAN <NUM> may store this reliability priority list as part of the UE PDU Session context. The reliability priority list includes multiple priority orders with N3 interface information. In case of handover, this list is forwarded to the target RAN.

If the RAN <NUM> detects that the edge node E1 (or the respective AF A1 <NUM>) has failed, the RAN switches to the backup path to route the traffic to the redundancy edge node E2 (i.e. specifically to A1' <NUM>). This situation is illustrated in the bottom half of <FIG>. In this case, all downlink and uplink traffic, the RAN can perform Network Address Translation (NAT) for backup path traffic. For example, RAN can spoof A1 address for downlink traffic and/or replace A1 address with A1' address for uplink traffic.

<FIG> shows a message flow diagram <NUM> illustrating a first option how a RAN <NUM>, e.g. corresponding to RAN <NUM>, may detect that it needs to switch to a backup path for an application function <NUM>, e.g. corresponding to application function <NUM>.

In this embodiment, the RAN <NUM> and the application function <NUM> (e.g. A1) periodically exchange health check/acknowledge messages (like Echo (request) messages or keep-alive messages) <NUM>, <NUM>. If the RAN <NUM> determines that the application function <NUM> is down, because it does not send a health check/acknowledge message or does not response with a health check acknowledgement, then a respective node (component) of the RAN <NUM> activates the backup path and exchanges traffic between the one or more UEs using the application function <NUM> and the application function over the backup path.

<FIG> shows a message flow diagram <NUM> illustrating a second option how a RAN <NUM>, e.g. corresponding to RAN <NUM>, may detect that it needs to switch to a backup path for an application function <NUM>, e.g. corresponding to application function <NUM>.

In this embodiment, the RAN <NUM> and the application function <NUM> periodically exchange QoS status messages (like path measurement message and messages related to AF (e.g. A1) conditions (e.g. congestions)).

If the RAN <NUM> determines that the application function <NUM> cannot meet the required SLA, because its QoS status is not sufficient, then a respective node (component) of the RAN <NUM> activates the backup path and exchanges traffic between the one or more UEs using the application function <NUM> and the application function over the backup path.

For example, similarly to a QoS Monitoring Packet (QMP) indicator in GTP-U (GPRS Tunnelling Protocol-User), the edge node containing the application function <NUM> sends a QoS packet to the RAN <NUM>.

Regarding health check/acknowledge messages, to realize in the <NUM> network, the current GTP specification defines an Extension Header field to transmit control messages. According to one embodiment, this extension header is used for exchanging health checks messages between UE and RAN e.g. as PDU Session Container.

<FIG> shows a message flow diagram <NUM> illustrating the exchange of health check/acknowledge messages <NUM>, <NUM> between a RAN <NUM> and an application function <NUM> via a UPF <NUM> using GTP-U.

Between the RAN <NUM> and the UPF <NUM> the health check/acknowledge messages <NUM>, <NUM> are exchanged using GTP-U, i.e. with a GTP header <NUM>. Between the UPF <NUM> and the application function <NUM>, the health check/acknowledge messages <NUM>, <NUM> are exchanged without GTP header (but still on the user plane).

The respective SMF provides a Packet Detection Rule and a Forwarding Action Rule to the UPF <NUM> for the health check/acknowledge messages <NUM>, <NUM>.

In the above examples, it was assumed that the application provided by the application function is a context independent application. This means that in order to compute the result or send the response to a query by a UE, the application server does not need to rely on the past context or data. For example, a real-time application like a safety monitoring application does not require past context or data, the application server can compute a video frame by frame and notify any safety information (without knowledge from the past). Another application is a website (accessed by a browser application on the client side).

However, an application function of an edge node may also provide an application which is of the category of context-dependent applications. For providing the result or send the response to a query of a UE regarding such an application, the application function has to rely on past context or data. For example, manoeuvre coordination in autonomous driving requires location context and data of surrounding vehicles.

<FIG> shows a massage flow diagram <NUM> illustrating an approach for providing a backup of an application server providing a context-dependent application.

Similarly to <FIG>, there is an edge node E1 <NUM> associated with a redundancy edge node <NUM> to serve as backup in case of failure of the edge node E1 (e.g. a platform failure or an AF failure). A UE <NUM> has a communication session with the application server A1 via a RAN <NUM> and a first UPF <NUM> for consuming an application provided by an AF A1 <NUM> of the edge node E1. The redundancy edge node <NUM> includes a corresponding AF A1' <NUM> for providing the application.

In contrast to the approach of <FIG> (which is for a context-independent application), the application is assumed to be a context-dependent application. Therefore, in this approach, the edge nodes E1, E2 have a dedicated link <NUM> for context synchronization i.e. A1 and A1' use this link for context synchronization. In other word, A1 and A1' have a dedicated link via E1 and E2.

The edge node E1 or application server A1 may provide whether it requires a dedicated link <NUM> with its reliability cluster node (i.e. its redundancy edge node E2) in its edge node profile or application profile as explained with reference to <FIG>.

For example, its edge node profile includes, as part of redundancy type information, that it requires a dedicated link with edge serer E2.

The other elements of the fallback procedure may be similar as the one of the approach for context-independent applications described above (in particular with reference to <FIG>).

It should be noted that in all approaches (irrespective of whether for context-dependent or context-independent applications) the UE does not have an impact on the reliability mechanism, i.e. the mechanism for providing a backup application server is transparent to the UE.

In summary, according to various embodiments, a communication server computer is provided as illustrated in <FIG>.

<FIG> shows a server computer <NUM> according to an embodiment.

The server computer <NUM> is a server computer of an arrangement of server computers (e.g. an edge). The server computer may for example implement an edge server and/or an application server. In particular, the server computer may be an edge server computer or an application server computer.

The server computer <NUM> includes at least one application server <NUM> configured to provide an application to one or more mobile communication terminals accessing the application server via a radio access network of a mobile communication network. The server computer <NUM> may include multiple application servers <NUM> configured to provide a respective application in this manner. The application server <NUM> may correspond to an edge node (possibly including further application servers).

The server computer <NUM> further includes a notification interface <NUM> configured to notify the mobile communication network about another server computer of the arrangement of server computers which the mobile communication network may use as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at a predetermined quality level.

According to various embodiments, in other words, a server computer indicates to a mobile communication network another server computer (which is for example at a different geographical location, e.g. in a different building and one or more kilometres away) which can serve as a backup for providing an application to one or more mobile communication terminals.

The component or components of the mobile communication network which the server computer notifies may for example include a core network component of the mobile communication network, e.g. a network function.

The mobile communication network may detect in case the server computer fails to provide this application (at all or at a certain minimum quality level) for any cause, e.g. because the server computer has failed, the application server providing the application in the server computer has failed or the connection to the server computer has failed or has become too bad, and may switch to the other server computer (e.g. reroute traffic related to the application). The mobile communication network may thus perform network-application coordination to handle the application reliability (e.g. edge-to-edge reliability) without mobile communication terminal (e.g. UE) impact. A server computer may be understood as a device, e.g. a device having its own housing (separate from the other server computers). The server computer and the other computers may be separate in the sense that they are functionally complete computers (in particular, they do not share resources such as a system memory or a processor).

For example, a UE has a communication with an application server which runs on top of edge. The application server notifies one or more core network control plane functions about a redundancy application server (i. e an application server which can serves as backup). The core network functions informs the radio access network about two sessions and establish both a backup session and an active session based on the information provided by the application server. The radio access network and the application server exchange health-check messages and detect a failure or QoS failure of the application server. In case of a failure or QoS failure (i.e. QoS not satisfied), the radio access network switches to the redundancy application server.

The server computer for example carries out a method as illustrated in <FIG>.

<FIG> shows a flow diagram <NUM> illustrating a method for providing an application to one or more mobile communication terminals according to an embodiment.

In <NUM>, a server computer of an arrangement of server computers provides an application to one or more mobile communication terminals accessing the application server via a radio access network of a mobile communication network.

In <NUM>, the mobile communication network is notified about another server computer of the arrangement of server computers which the mobile communication network may use as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at a predetermined quality level.

It should be noted that the notification may happen before the application is provided, i.e. <NUM> may take place before (or at the same time) as <NUM>.

The mobile communication network is for example configured as explained in the following with reference to <FIG>.

<FIG> shows a mobile communication network <NUM> according to an embodiment.

The mobile communication network <NUM> includes a radio access network <NUM> configured to provide a connection between one or more mobile communication terminals <NUM> and a server computer <NUM> of an arrangement of server computers for providing of an application to the one or more mobile communication terminals.

The mobile communication network <NUM> further includes a receiver <NUM> configured to receive a notification about another server computer of the arrangement of server computers which the mobile communication network may use as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at a predetermined quality level.

Further, the mobile communication network <NUM> includes a controller <NUM> configured to control the radio access network to provide a connection to the other server computer for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at the predetermined quality level.

The controller <NUM> may be a component of the radio access network but it may also be a network function of the mobile communication network's core network.

The mobile communication network for example carries out a method as illustrated in <FIG>.

<FIG> shows a flow diagram <NUM> illustrating a method for providing one or more mobile communication terminals with access to a server computer of an arrangement of server computers according to an embodiment.

In <NUM>, a connection between the one or more mobile communication terminals and the server computer is provided for providing of an application to the one or more mobile communication terminals by a radio access network.

In <NUM>, a notification is received about another server computer of the arrangement of server computers which the mobile communication network may use as backup for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at a predetermined quality level.

In <NUM>, the radio access network is controlled to provide a connection to the other server computer for providing the application to the one or more mobile communication terminals in case the server computer fails to provide the application at the predetermined quality level.

Claim 1:
A server computer (<NUM>, <NUM>) of an arrangement of server computers, comprising:
at least one application server (<NUM>, <NUM>) configured to provide an application to one or more mobile communication terminals (<NUM>, <NUM>, <NUM>) accessing the application server (<NUM>, <NUM>) via a radio access network (<NUM>, <NUM>, <NUM>) of a mobile communication network (<NUM>); and
a notification interface (<NUM>) configured to notify a core network component (<NUM>) of the mobile communication network (<NUM>) about another server computer of the arrangement of server computers which the mobile communication network (<NUM>) may use as backup for providing the application to the one or more mobile communication terminals (<NUM>, <NUM>, <NUM>) in case the server computer (<NUM>, <NUM>) fails to provide the application to the one or more mobile communication terminals (<NUM>, <NUM>, <NUM>) at a predetermined quality level.