WO2020212642A1

WO2020212642A1 - Data centre management

Info

Publication number: WO2020212642A1
Application number: PCT/FI2019/050310
Authority: WO
Inventors: Kirsi Rotsten; Raija TIMONEN; Alexander Milinski
Original assignee: Nokia Technologies Oy
Priority date: 2019-04-16
Filing date: 2019-04-16
Publication date: 2020-10-22

Abstract

According to an example aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive a re-balancing instruction relating to sessions served by the apparatus, determine a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and trigger releasing of at least some sessions in the subset.

Description

DATA CENTRE MANAGEMENT

FIELD

[0001] The present disclosure relates to the field of data centre management.

BACKGROUND

[0002] Cellular communication networks comprise radio access networks, RANs, wherein base stations or other access nodes are comprised, and core networks, CNs, where nodes are comprised which have network-wide effects. For example, switches, subscriber registers, gateways and billing systems are examples of nodes which may be located in core networks.

[0003] In a traditional cellular communication network, core network nodes may be distinct physical nodes, such that the nodes may be configured to perform as one or more core network functionalities. For example, a physical computational substrate configured to act as a switch may also have a lawful interception functionality therein, although the switch and lawful interception functionality may architecturally be distinct elements of a core network.

[0004] More recently, core networks have been implemented in increasingly virtualized form, by which it is meant that a computational substrate is programmed to function as a range of virtualized core network functionalities.

SUMMARY [0005] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. [0006] According to a first aspect of the present disclosure, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive a re- balancing instruction relating to sessions served by the apparatus, determine a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and trigger releasing of at least some sessions in the subset.

[0007] According to a second aspect of the present disclosure, there is provided a method comprising receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus, determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and triggering releasing of at least some sessions in the subset.

[0008] According to a third aspect of the present disclosure, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive a de- registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities, determine a set of user identities based on the set of cell identities, and trigger releasing sessions of users whose identities are comprised in the set of user identities.

[0009] According to a fourth aspect of the present disclosure, there is provided a method, comprising receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities, determining a set of user identities based on the set of cell identities, and triggering releasing sessions of users whose identities are comprised in the set of user identities.

[0010] According to a fifth aspect of the present disclosure, there is provided an apparatus comprising means for receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus, means for determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and means for triggering releasing of at least some sessions in the subset. [0011] According to a sixth aspect of the present disclosure, there is provided an apparatus comprising means for receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities, means for determining a set of user identities based on the set of cell identities, and means for triggering releasing sessions of users whose identities are comprised in the set of user identities.

[0012] According to a seventh aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least receive, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus, determine a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and trigger releasing of at least some sessions in the subset.

[0013] According to an eighth aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least receive a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities, determine a set of user identities based on the set of cell identities, and trigger releasing sessions of users whose identities are comprised in the set of user identities.

[0014] According to a ninth aspect of the present disclosure, there is provided a computer program configured to cause a computer to perform at least the following, when run: receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus, determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and triggering releasing of at least some sessions in the subset.

[0015] According to a tenth aspect of the present disclosure, there is provided a computer program configured to cause a computer to perform at least the following, when run: receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities, determining a set of user identities based on the set of cell identities, and triggering releasing sessions of users whose identities are comprised in the set of user identities. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention; [0017] FIGURE 2 illustrates signalling in accordance with at least some embodiments of the present invention;

[0018] FIGURE 3 illustrates signalling in accordance with at least some embodiments of the present invention;

[0019] FIGURE 4 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0020] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention, and

[0021] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. EMBODIMENTS

[0022] Disclosed herein are methods to load balance offloaded sessions back to data centres which have been brought back on-line following an outage, for example an outage due to software or hardware updating. In brief, a geographical region of origin of the sessions may be used as a criterion, whereby following the outage the sessions will once more be handled in data centres in accordance with routing solutions similar to those preceding the outage. While primarily disclosed herein as onloading following outage, more generally also other reasons for load balancing may be behind the moving of sessions. Other examples include the introduction of a new data centre, or the increasing of a capacity of a data centre.

[0023] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. The system comprises plural radio access networks, RANs 102, 104 and 106. The RANs may be configured to operate in accordance with a cellular or non-cellular radio access technology, RAT, for example. Examples of cellular RATs include wideband code division multiple access, WCDMA, long term evolution, LTE, and fifth generation, 5G, which is also known as new radio, NR. Examples of non- cellular RATs include wireless local area network, WLAN, and worldwide interoperability for microwave access, WiMAX. The RANs 102, 104, 106 may comprise base stations, or access nodes, as they may be known, depending on the specific technology used.

[0024] RAN 102 is operably connected by connection 102A to data centre 110. Data centre 110 is arranged to run a virtualized core network, CN, comprising plural core network functionalities, such as gateways, switches, mobility management entities, MMEs, and/or call session control functions, CSCFs. Examples of CSCFs include serving CSCF, S-CSCF and proxy CSCF, P-CSCF. A specific example of a gateway is a packet data network, PDN, gateway. Such a gateway may be referred to as a P-GW or PGW, known in 5G as UPF, for example. The core network functionalities are illustrated schematically in FIGURE 1 as unlabelled boxes in data centre 110. Core network functionalities may further include serving gateways, SGWs, known in 5G as SMF, configured to route and forward user data packets and to act as a mobility anchor for the user plane during handovers. A mobility management entity, MME, known in 5G as an AMF, is configured to control access networks and manage idle-mode UE paging, among other tasks.

[0025] For each subscriber, there may be assigned exactly one SGW, and one or more PGWs carrying bearers of the subscriber. The SGW may be aware of all the PGWs of the subscriber. While discussed herein, in part, as being performed by a PGW, aspects of the present disclosure may be understood as being undertaken in co-operation among a group of virtualized PGWs (or UPFs in 5G) and, possibly, also a virtualized SGW (or SMF in 5G). [0026] RAN 104 is operably connected by connection 104 A to data centre 120. Data centre 120 is arranged to run a virtualized core network, CN, comprising plural core network functionalities. RAN 106 is operably connected by connection 106 A to data centre 130. Data centre 130 is arranged to run a virtualized core network, CN, comprising plural core network functionalities. The core network functionalities in data centres 120 and 130 may be similar to those described above in connection with data centre 110.

[0027] Data centres 110, 120 and 130 are operably connected with each other via an interconnection network 140, enabling exchanging information between the data centres. Naturally, the specific number of RANs and data centres in FIGURE 1 is merely an example, to which this disclosure is not limited. For example, there may be a system of two data centres, or a system of four data centres.

[0028] Data centres 110, 120 and 130 are used to run virtualized networks, in detail, functional elements of core networks are run in the data centres as software functionalities. Thus the virtualized core network run by data centre 110, for example, performs in a similar way as a conventional core network composed of plural distinct nodes. Using a virtualized core network provides benefits in terms of using standard computing substrates and less, or no, specialized hardware. The network function virtualization, NFV, architecture used includes hardware resources in data centres 110, 120, 130 includes computing hardware, storage hardware, and communication hardware. The computing hardware may be implemented using one or more processors, the storage hardware may be implemented using one or more memories, and the communication hardware may be implemented using one or more transceivers, transmitters, receivers, interfaces, and the like. The virtualized core network functionalities of data centre 110 are run as so-called virtualized network functions, VNFs. The VNFs have interfaces with other VNFs which replicate logically the internal interfaces of a normal core network, such that a VNF can perform logically in a similar way to a core network functionality implemented as a standalone node. The VNFs may run on virtualization software which presents a logical cloud computing resource for the use of the VNFs. A logical cloud computing resource may run on hardware computational substrates which are on one server or more than one server.

[0029] Data centres such as data centres 110, 120 and 130 require occasional maintenance tasks. Such tasks may relate to the computational frameworks of the centres themselves, such as updates to hardware or the virtualization software, or such maintenance tasks may relate to the VNFs. For example, software may be patched to correct errors and the VNFs may be updated to newer versions, which support new features, for example as a response to establishment of a new version of a relevant technical standard. [0030] During maintenance tasks, the VNFs of a data centre may need to be deactivated. This results in the data centre being in an outage state, where it is unable to offer core network functionality. Despite maintenance tasks typically being scheduled for night time, there will in practice nonetheless be users with active sessions run through the VNFs which are to be deactivated. The sessions may be offloaded, that is, transferred to other data centres, or in general to at least one other data centre, to avoid interruption to service the user of the session is experiencing. In general the sessions may comprise packet data traffic and voice over LTE, VoLTE, or voice over WLAN, VoWiFi, user and control planes, for example. In general, while described herein in terms of, for example, LTE and VoLTE, principles of this disclosure are applicable also to future technologies, such as voice over NR/5G, VoNR, including splitting PGW and SGW VNFs into control plane and user planes and where a functional split may be slightly changed. Further, network entities may have different names in different technologies.

[0031] To perform offloading, for example from data centre 110 to data centres 120 and 130, a passive solution is to allow all sessions to complete, while routing new sessions to the other data centres. Thus as even the last ones of the original sessions eventually end, the data centre will be empty of sessions and thus ready for the maintenance work. Such offloading takes time. On the other hand, an active offloading comprises actively re routing, handing over or re-establishing the active sessions to other data centres. Active offloading may also be used with a threshold time, for example, ten minutes may be waited during which new sessions are already routed to the other data centres, and many sessions of short duration are allowed to naturally end in the data centre that is to be placed into outage. This reduces a signalling burden involved in actively transferring sessions.

[0032] After the maintenance tasks are completed and outage ends, it would be beneficial from the network point of view to rebalance the traffic load caused by the sessions between the data centres as soon as possible. Moving the relevant sessions back may be referred to as onloading, that is, reversing the offloading. [0033] The onloading may be performed passively or actively, as was the case for offloading. Passively, the normal routing configuration is restored, for example in domain name server, DNS, systems, to cause new sessions from a geographic region relevant to the data centre 110, which is once more online, to be routed to it. For example, this may occur when new VoLTE/VoWiFi registrations take place or whenever the end user switches on her user equipment, UE. Such a passive method leaves existing sessions and their data bearers and IP multimedia subsystem, IMS, registrations in the data centres into which they were offloaded until they expire or are tom down. As in the offloading case, an active solution produces faster results than a passive one. An active onloading method should decide, which sessions in the active data centres should be moved to VNFs of the updated data centre 110, and then to perform this moving.

[0034] The onloading may be performed by contacting the data centres to which sessions were offloaded in connection with entering data centre 110 into outage, to provide a re-balancing instruction relating to sessions active in those data centres into which session were offloaded. In response, data centres 120 and 130 determine a subset of their active sessions, the subset being defined as those sessions which originate in a geographic region from where sessions are not normally routed, at least not as a primary choice, to data centres 120 and 130, and trigger releasing of at least some sessions in the subset. For example, the subset may comprise those sessions, which originate in a geographic region from where sessions are, under normal routing configuration, provided to data centre 110. As the released sessions are re-established, the restored routing configuration causes the sessions to be routed to VNFs of data centre 110. The re-balancing instruction may be triggered from a user interface, for example, and/or it may be communicated from data centre 110 to data centres 120 and 130 via interconnection network 140. The re-balancing instruction may comprise an indication of the geographic region.

[0035] While primarily disclosed herein as onloading following outage, more generally also other reasons for load balancing may be behind the moving of sessions and the sending of the re-balancing instruction. Other examples include the introduction of a new data centre, or the increasing or decreasing of a capacity of a data centre. Further, a high load in a data centre may be a trigger for re-defining the geographic area from which sessions are routed to that data centre, for example, the geographic area may be reduced in size and the re-balancing instruction may be sent to enforce the new geographic area. [0036] Releasing a session may comprise tearing down packet data traffic of the session. Releasing a session may comprise causing IMS deregistration. Releasing a session may comprise causing packet data network, PDN, connection release. Releasing a session may comprise all of tearing down packet data traffic, IMS deregistration and PDN connection release. In some embodiments, emergency-type sessions are not released. Avoiding emergency-type session release may be accomplished by using a quality of service, QoS, class identifier, QCI, which indicates a session is of the emergency type. Thus voice calls to an emergency dispatcher station, for example, are not interrupted. After session release, the UE should perform an attachment procedure, which will be routed to the data centre 110 being onloaded.

[0037] The geographic region used in determining the subset of sessions in data centre 120, for example, may be based on a suitable geographic indication. The subset comprises sessions served by VNFs of data centre 120 (or 130) which are apparently offloaded to this data centre from another data centre, since a normal routing configuration would not provide these sessions to VNFs of this data centre. The geographic region may be defined based on an inverse of the normal routing configuration, such that sessions from geographic regions other than the one or ones from where sessions are normally routed to data centre 120 are placed in the subset. Tracking area(s) and/or cell identities, or ranges of cell identities, are examples of suitable ways to define the geographical area. Thus the re balancing instruction may comprise at least one of: at least one tracking area, at least one cell identity and at least one cell identity range as the indication of the geographic region.

[0038] Releasing sessions in the subset may be performed in batches, for example a set number of sessions per every predefined space of time, such as, for example, a hundred sessions every ten seconds, or every minute, to prevent a sudden signalling flood in the data centre(s) and the interconnection network 140.

[0039] The releasing may be performed separately for sessions with IMS registrations and sessions without an IMS registration. In detail, a PGW VNF may comprise functions for controlling a control plane, wherein such functions may be referred to as a PGW-C VNF. Fikewise, a PGW VNF may comprise functions for controlling a user plane, wherein such functions may be referred to as a PGW-U VNF. Such separation of control and user planes may be referred to as Control and User Plane Separation, CUPS. In some embodiments, the session handling described here is performed in whole or mostly in a PGW-C VNF. In specifically 5G technology, an 5G Session Management Function, SMF, VNF may be configured to perform functions described herein as performed by a PGW VNF. This may be seen as a terminological issue.

[0040] A PGW VNF is well placed to act in determining the subset of sessions for release and onloading, since it is aware of existing packet data traffic, whether IMS registrations are involved, whether a session has an emergency-type QCI, and it also has information on the UE location, which may be based on RAN information, such as the afore-mentioned tracking area or cell identity, or a combination thereof, for example. In 3GPP networks, base stations may be required to provide UE location information to the core network, for example to facilitate emergency responders in case of an emergency call. Based on the geographic region, the PGW may compile a list of sessions to be released and/or of subscribers whose sessions are to be released. This list may be compiled based on comparing the UE locations of active sessions to the geographic region used in determining the subset of sessions, for example.

[0041] For IMS registered sessions (such as VoLTE related SIP sessions, for example), an S-CSCF VNF may obtain a de-registration instruction relating to sessions served by a server or data centre and the definition of the geographic area, for example from the HSS VNF. The S-CSCF VNF may be configured to query from a subscriber register, such as a home subscriber server, HSS, or a unified data management function, UDM, for user identities of sessions originating from the geographic area (or, as noted above, outside the geographic area). This query may be for plural subscribers, that is, the query may request several, or all, user identities which fulfil the geographic criterion. The geographic area may, in this querying, be expressed based on cell identities or on at least one other suitable geographic indication, such as geo-fence(s), area code(s) or on at least one administrative area such as at least one city and/or at least one country. Once the S- CSCF VNF obtains in response the users or user identities, it may trigger releasing sessions of these users, as will be laid out in more detail herein below. [0042] In detail, the S-CSCF VNF may issue a query message to the HSS, the query message comprising a definition of the geographic area, expressed for example as at least one tracking area, at least one cell identity and/or at least one range of cell identities. The HSS may respond to the query message with the set of user identities the sessions of which originate in the geographic area. The query may be issued over a Cx interface, for example. The S-CSCF VNF may request de-registration of these identities from a P-CSCF, for example, thus triggering a process that leads to teardown of the sessions, and subsequent re-establishment with VNFs of the onloaded data centre.

[0043] FIGURE 2 illustrates signalling in accordance with at least some embodiments of the present invention. The method of FIGURE 2 is a PGW based method for release of sessions. On the vertical axes are disposed, from the left to the right, the user equipment UE, a MME or serving GPRS support node (SGSN), the PGW, the onloading- data centre PGW, a P-CSCF, the onloading-data centre P-CSCF, an S-CSCF and, on the right, a HSS. These functions may be virtualized as VNFs. Time advances from the top toward the bottom. In place of a HSS, in 5G terminology there may be a unified data management function, UDM.

[0044] In phase 210, responsive to a re-balancing instruction, the PGW determines the subset of its sessions which are from the geographic area not usually providing sessions to this data centre. Release of those ones of these sessions which have no IMS registration is triggered in phase 210, and they are re-established with the new PGW in the onloading data centre in phase 220.

[0045] As to sessions in the determined subset which do have IMS registrations, their re-registration is requested in phase 230. This method will be described in more detail in connection with FIGURE 3. In phase 240, the IMS-associated sessions are re-registered with VNFs of the onloading data centre.

[0046] FIGURE 3 illustrates signalling in accordance with at least some embodiments of the present invention. The method of FIGURE 3 is a method for release of sessions with IMS registrations. On the vertical axes are disposed, from the left to the right, the user equipment UE, a MME or serving GPRS support node (SGSN), the PGW, the onloading-data centre PGW, a P-CSCF, the onloading-data centre P-CSCF, an S-CSCF and, on the right, a HSS. These functions may be virtualized as VNFs. Time advances from the top toward the bottom. [0047] In phase 310, the S-CSCF determines to act regarding de-registration of identities associated with sessions which do not originate from a geographic area from which sessions are normally routed to this data centre. In phase 320, the S-CSCF queries for a set of user identities fulfilling the geographic indication from the HSS. The request, as noted above, may comprise information defining the geographic indication, for example in the form of cell identities.

[0048] The HSS provides the set of user identities in phase 330, as a response to the query of phase 320. The S-CSCF may request from the HSS de-registration of the set of user identities (not illustrated in FIGURE 3).

[0049] In phase 340, the HSS may request the MME or SGSN (in general, a node where an international mobile subscriber identity, IMSI, associated with the user identity is registered) to select a new P-CSCF for each of the user identities in the set of user identities. The new P-CSCF may be a VNF in the onloading data centre, for example. This message may comprise an interface S6a/ interface S6d insert-subscription-data request / insert-subscription-data answer, IDR/IDA, request, for example. Phase 350 is the corresponding response, which may comprise an identity or address of the new P-CSCF, for example. The HSS may indicate this to the S-CSCF (not illustrated).

[0050] In phase 360, the S-CSCF requests de-registering of the (each) user identity in the set from the P-CSCF, which indicates the de-registering to the UEs, phase 370. The UEs may, optionally, respond with a de-registration acknowledgement such as SIP OK, for example, phase 380, which may be conveyed to the S-CSCF, phase 390, and the HSS (not illustrated). The de-registration will also clear the IMS related PDN connections.

[0051] In phase 3100, the MMS/SGSN may release the PDNs, both IMS and data related PDNs.

[0052] Subsequently, phase 3110, the data/PDNs are re-established with the onloading data centre, restoring service to the UE. A REGISTER message may be issued from the UE to the P-CSCF VNF in the onloading data centre, phase 3120. This may be passed onward from the P-CSCF VNF to a corresponding S-CSCF VNF (not illustrated).

[0053] FIGURE 4 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 400, which may comprise, for example, a computational substrate of a data centre or a UE, as applicable. Comprised in device 400 is processor 410, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 410 may comprise, in general, a control device. Processor 410 may comprise more than one processor. Processor 410 may be a control device. A processing core may comprise, for example, a Cortex- A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. Processor 410 may comprise at least one Qualcomm Snapdragon and/or Intel Xeon processor. Processor 410 may comprise at least one application-specific integrated circuit, ASIC. Processor 410 may comprise at least one field-programmable gate array, FPGA. Processor 410 may be means for performing method steps in device 400. Processor 410 may be configured, at least in part by computer instructions, to perform actions. [0054] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, 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.

[0055] This definition of circuitry applies to all uses of this term 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, 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.

[0056] Device 400 may comprise memory 420. Memory 420 may comprise random- access memory and/or permanent memory. Memory 420 may comprise at least one RAM chip. Memory 420 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 420 may be at least in part accessible to processor 410. Memory 420 may be at least in part comprised in processor 410. Memory 420 may be means for storing information. Memory 420 may comprise computer instructions that processor 410 is configured to execute. When computer instructions configured to cause processor 410 to perform certain actions are stored in memory 420, and device 400 overall is configured to run under the direction of processor 410 using computer instructions from memory 420, processor 410 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 420 may be at least in part comprised in processor 410. Memory 420 may be at least in part external to device 400 but accessible to device 400.

[0057] Device 400 may comprise a transmitter 430. Device 400 may comprise a receiver 440. Transmitter 430 and receiver 440 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 430 may comprise more than one transmitter. Receiver 440 may comprise more than one receiver. Transmitter 430 and/or receiver 440 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, 5G, long term evolution, LTE, IS-95, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0058] Device 400 may comprise a near-field communication, NFC, transceiver 450. NFC transceiver 450 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies. [0059] Device 400 may comprise user interface, UI, 460. UI 460 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 400 to vibrate, a speaker and a microphone. A user may be able to operate device 400 via UI 460, for example to configure offloading and/or onloading of sessions, as described herein. [0060] Device 400 may comprise or be arranged to accept a user identity module

470. User identity module 470 may comprise, for example, a subscriber identity module, SIM, card installable in device 400. A user identity module 470 may comprise information identifying a subscription of a user of device 400. A user identity module 470 may comprise cryptographic information usable to verify the identity of a user of device 400 and/or to facilitate encryption of communicated information and billing of the user of device 400 for communication effected via device 400.

[0061] Processor 410 may be furnished with a transmitter arranged to output information from processor 410, via electrical leads internal to device 400, to other devices comprised in device 400. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 420 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 410 may comprise a receiver arranged to receive information in processor 410, via electrical leads internal to device 400, from other devices comprised in device 400. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 440 for processing in processor 410. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0062] Device 400 may comprise further devices not illustrated in FIGURE 4. For example, where device 400 comprises a smartphone, it may comprise at least one digital camera. Some devices 400 may comprise a back-facing camera and a front-facing camera, wherein the back- facing camera may be intended for digital photography and the front- facing camera for video telephony. Device 400 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 400. In some embodiments, device 400 lacks at least one device described above. For example, some devices 400 may lack a NFC transceiver 450 and/or user identity module 470. [0063] Processor 410, memory 420, transmitter 430, receiver 440, NFC transceiver

450, UI 460 and/or user identity module 470 may be interconnected by electrical leads internal to device 400 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 400, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0064] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in a PDN GW PGW, or PGW VNF, for example.

[0065] Phase 510 comprises receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus. The apparatus may comprise a data centre, for example. The re-balancing instruction may relate to an onloading of a data centre other than the apparatus, for example. Other examples include the introduction of a new data centre, or the increasing of a capacity of a data centre. Phase 520 comprises determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus. Phase 530 comprises triggering releasing of at least some sessions in the subset. Phase 530 may comprise triggering releasing all the sessions in the subset, for example in batches.

[0066] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in an S-CSCF or S-CSCF VNF, for example.

[0067] Phase 610 comprises receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities. Phase 620 comprises determining a set of user identities based on the set of cell identities. Finally, phase 630 comprises triggering releasing sessions of users whose identities are comprised in the set of user identities.

[0068] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0069] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0070] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0071] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0072] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0073] The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0074] At least some embodiments of the present invention find industrial application in managing sessions in connection with data centre maintenance.

REFERENCE SIGNS LIST

Claims

CLAIMS:

1. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to:

- receive a re-balancing instruction relating to sessions served by the apparatus;

- determine a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and

- trigger releasing of at least some sessions in the subset.

2. The apparatus according to claim 1, wherein the releasing comprises tearing down packet data traffic of the at least some sessions in the subset.

3. The apparatus according to claim 1 or 2, wherein the apparatus is configured to trigger releasing of all sessions in the subset except emergency-type sessions.

4. The apparatus according to claim 3, wherein the apparatus is configured to identify emergency-type sessions based at least partly on a quality of service class identifier.

5. The apparatus according to any of claims 1 - 4, wherein the apparatus is configured to define the geographic region based on at least one tracking area.

6. The apparatus according to any of claims 1 - 5, wherein the apparatus is configured to define the geographic region based on at least one cell identifier of a cellular communication system.

7. The apparatus according to any of claims 1 - 6, wherein the apparatus is configured to trigger releasing of the at least some sessions in the subset in batches.

8. The apparatus according to any of claims 1 - 7, wherein the apparatus comprises a packet data network gateway functionality, and wherein the apparatus is configured to trigger releasing sessions in the subset which do not have IP multimedia subsystem registrations itself, and to trigger releasing sessions in the subset which do have IP multimedia subsystem registrations by requesting their release from a core network functionality.

9. A method comprising:

- receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus;

- determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and

- triggering releasing of at least some sessions in the subset.

10. The method according to claim 9, wherein the releasing comprises tearing down packet data traffic of the at least some sessions in the subset.

11. The method according to claim 9 or 10, comprising triggering releasing of all sessions in the subset except emergency-type sessions.

12. The method according to claim 11, further comprising identifying emergency-type sessions based at least partly on a quality of service class identifier.

13. The method according to any of claims 9 - 12, wherein the geographic region is defined based on at least one tracking area.

14. The method according to any of claims 9 - 13, wherein the geographic region is defined based on at least one cell identifier of a cellular communication system.

15. The method according to any of claims 9 - 14, further comprising triggering releasing of the at least some sessions in the subset in batches.

16. The method according to any of claims 9 - 15, wherein the apparatus comprises a packet data network gateway functionality, and wherein the method comprises triggering releasing by the apparatus sessions in the subset which do not have IP multimedia subsystem registrations itself, and triggering releasing sessions in the subset which do have IP multimedia subsystem registrations by requesting their release from a core network functionality.

17. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to:

- receive a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities;

- determine a set of user identities based on the set of cell identities, and

- trigger releasing sessions of users whose identities are comprised in the set of user identities.

18. The apparatus according to claim 17, wherein the apparatus is configured to determine the set of user identities based on the set of cell identities by querying a subscriber register for the set of user identities, the query comprising the set of cell identities.

19. The apparatus according to claim 18, wherein the subscriber register comprises a home subscriber server functionality or a unified data management function.

20. The apparatus according to any of claims 17 - 19, wherein the apparatus is configured to run a serving call session control function which has IP multimedia subsystem registrations of the sessions.

21. The apparatus according to any of claims 17 - 20, wherein the apparatus is configured to trigger releasing the sessions by issuing de-registration requests relating to the identities comprised in the set of user identities.

22. A method, comprising:

- receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities;

- determining a set of user identities based on the set of cell identities, and

- triggering releasing sessions of users whose identities are comprised in the set of user identities.

23. The method according to claim 22, comprising determining the set of user identities based on the set of cell identities by querying a subscriber register for the set of user identities, the query comprising the set of cell identities.

24. The method according to claim 23, wherein the subscriber register comprises a home subscriber server functionality or a unified data management function.

25. The method according to any of claims 22 - 24, further comprising running a serving call session control function which has IP multimedia subsystem registrations of the sessions.

26. The method according to any of claims 22 - 25, comprising triggering releasing the sessions by issuing de-registration requests relating to the identities comprised in the set of user identities.

27. An apparatus comprising:

- means for receiving, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus;

- means for determining a subset of the sessions, the subset originating in a geographic region from where sessions are not normally routed to the apparatus, and

- means for triggering releasing of at least some sessions in the subset.

28. An apparatus comprising:

- means for receiving a de-registration instruction relating to sessions served by a server, the instruction relating to a sessions from a set of cell identities;

- means for determining a set of user identities based on the set of cell identities, and

- means for triggering releasing sessions of users whose identities are comprised in the set of user identities.

29. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:

- receive, in an apparatus, a re-balancing instruction relating to sessions served by the apparatus;

- trigger releasing of at least some sessions in the subset.

30. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:

- determine a set of user identities based on the set of cell identities, and

31. A computer program configured to cause a computer to perform at least the following, when run:

- triggering releasing of at least some sessions in the subset.

32. A computer program configured to cause a computer to perform at least the following, when run:

- determining a set of user identities based on the set of cell identities, and triggering releasing sessions of users whose identities are comprised in the set of user identities.