WO2023139410A1

WO2023139410A1 - Method, apparatus and computer program

Info

Publication number: WO2023139410A1
Application number: PCT/IB2022/050552
Authority: WO
Inventors: Thierry Van De Velde
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2023-07-27

Abstract

There is provided an apparatus, said apparatus comprising means for, for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forwarding a payload of frames containing the assigned link layer address or ta payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

Description

METHOD, APPARATUS AND COMPUTER PROGRAM

Field

The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to assigning a Link Layer Address to a mobile User Equipment not communicating a Link Layer Address to a network.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices (also referred to as station or user equipment) and/or application servers. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia, content data, time-sensitive network (TSN) flows and/or data in an industrial application such as critical system messages between an actuator and a controller, critical sensor data (such as measurements, video feed etc.) towards a control system and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session, for example, between at least two stations or between at least one station and at least one application server (e.g. for video), occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN) operating based on 3GPP radio standards such as E-UTRA, New Radio, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) based on the E-UTRAN radio-access technology, and so-called 5G system (5GS) including the 5G or next generation core (NGC) and the 5G Access network based on the New Radio (NR) radio-access technology (NG-RAN). 5GS including NR are being standardized by the 3rd Generation Partnership Project (3GPP).

Summary

In a first aspect there is provided an apparatus, said apparatus comprising means for, for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

In a second aspect there is provided an apparatus said apparatus comprising means for, for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment, providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

The apparatus according to the first aspect or the second aspect may comprise means for providing the assigned link layer address or assigned segment routing label from a control plane function to a user plane function or for providing an indication from the control plane function to the user plane function to assign the link layer address or segment routing label at the user plane.

The apparatus according to the first aspect or the second aspect may comprise means for providing the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function. The apparatus according to the first aspect or the second aspect may comprise means for providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

The user plane function may associate an uplink forwarding action rule to a downlink packet detection rule including the link layer address or segment routing label.

The link layer address or segment routing label may be from a range associated with a group of multiple user equipment or multiple devices reachable through the user equipment

The link layer address or segment routing label may be from a range associated with a slice of the network

The link layer address or segment routing label may be from a range associated with the network

The link layer address or segment routing label may be from a range associated with an instance of the user plane function.

The link layer address or segment routing label may be from a range associated with an instance of a component of the user plane function.

The link layer address may be a Media Access Control, MAC, address.

In a third aspect there is provided a method comprising, for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

In a fourth aspect there is provided a method comprising, for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment, providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus. The method according to the third aspect or the fourth aspect may comprise providing the assigned link layer address or assigned segment routing label from a control plane function to a user plane function or for providing an indication from the control plane function to the user plane function to assign the link layer address or segment routing label at the user plane.

The method according to the third aspect or the fourth aspect may comprise providing the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function.

The method according to the third aspect or the fourth aspect may comprise providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

The link layer address may be a Media Access Control, MAC, address.

In a fifth aspect there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: for a user equipment not having communicated a link layer address to a network, assign a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forward a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

In a sixth aspect there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: for a user equipment having communicated a link layer address to a network, assign a link layer address or segment routing label to a device reachable through the user equipment, provide an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network and forward a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

The apparatus according to the fifth aspect or the sixth aspect may be configured to provide the assigned link layer address or assigned segment routing label from a control plane function to a user plane function or provide an indication from the control plane function to the user plane function to assign the link layer address or segment routing label at the user plane.

The apparatus according to the fifth aspect or the sixth aspect may be configured to provide the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function.

The apparatus according to the fifth aspect or the sixth aspect may be configured to provide an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

The link layer address or segment routing label may be from a range associated with a group of multiple user equipment or multiple devices reachable through the user equipment The link layer address or segment routing label may be from a range associated with a slice of the network

The link layer address may be a Media Access Control, MAC, address.

In a seventh aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following, for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

In an eighth aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following, for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment, providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

The apparatus may be caused to perform providing the assigned link layer address or assigned segment routing label from a control plane function to a user plane function or providing an indication from the control plane function to the user plane function to assign the link layer address or segment routing label at the user plane.

The apparatus may be caused to perform providing the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function. The apparatus may be caused to perform providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

The link layer address may be a Media Access Control, MAC, address.

In a ninthaspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the third aspect or the fourth aspect.

In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system; Figure 2 shows a schematic diagram of an example mobile communication device;

Figure 3 shows a schematic diagram of an example control apparatus;

Figure 4 shows a flowchart of a method according to an example embodiment;

Figure 5 shows a flowchart of a method according to an example embodiment;

Figure 6 shows a schematic diagram of an example communication system where a UE is re-anchored at a new UPF or UPF component instance;

Figure 7 shows a schematic diagram of an example EPS and 5GS communication system where a MAC address is allocated according to an example embodiment;

Figure 8 shows a schematic diagram of a control plane function and user plane function.

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

An example of a suitable communications system is the 5G System (5GS). Network architecture in 5GS may be similar to that of LTE-advanced. Base stations of NR systems may be known as next generation Node Bs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer QoS support, and some on-demand requirements for e.g. QoS levels to support QoE of user point of view. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

5G networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

Figure 1 shows a schematic representation of a 5G system (5GS) 100. The 5GS may comprise a user equipment (UE) 102 (which may also be referred to as a communication device or a terminal), a 5G radio access network (5GRAN) 104, a 5G core network (5GCN) 106, one or more application functions (AF) 108 and one or more data networks (DN) 110.

An example 5G core network (CN) comprises functional entities. The 5GCN 106 may comprise one or more access and mobility management functions (AMF) 112, one or more session management functions (SMF) 114, an authentication server function (AUSF) 116, a unified data management (UDM) 118, one or more user plane functions (UPF) 120, a unified data repository (UDR) 122 and/or a network exposure function (NEF) 124. The UPF is controlled by the SMF (Session Management Function) that receives policies from a PCF (Policy Control Function).

The CN is connected to a terminal device via the radio access network (RAN). The 5GRAN may comprise one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions. The RAN may comprise one or more access nodes.

A UPF (User Plane Function) whose role is called PSA (PDU (Protocol Data Unit) Session Anchor) may be responsible for forwarding frames back and forth between the DN (data network) and the tunnels established over the 5G towards the UE(s) exchanging traffic with the DN.

A possible terminal device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE). An appropriate communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples 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), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Nonlimiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

A device is typically provided with at least one data processing entity 201, at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

Figure 3 shows an example embodiment of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, eNB or gNB, a relay node or a core network node such as an MME or S-GW or P-GW, or a core network function such as AMF/SMF, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301, at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head.

There are, in existing standards, 3GPP techniques to re-anchor the UE at a new UPF-PSA (PDU Session Anchor). In the EPS, re-anchoring of a UE at a new PGW-U during the EPS session is not supported.

It may be desirable to re-anchor the UE at a new UPF (or serving PGW-U (SPGW-U)) as the UE moves through the 5GS, without changing the UE’s IPv6 Prefix, thus without breaking ongoing IP flows (e.g., conversational audio/video, drone control, etc.).

3GPP Release 15 has introduced the Ethernet PDU Type in the 5G System (5GS, TS 23.501/502), besides the PDU Session Types “IPv4”, “IPv6”, “IPv4v6” and “Unstructured”. In the Evolved Packet System (EPS, TS 23.401/402) the PDN Types Types “IPv4”, “IPv6”, “IPv4v6” and “Unstructured” are defined in Release 15, and “Ethernet” is defined in Release 16.

Upon mobility and handover within the 5GS the UE may be re-anchored at a new intermediate UPF (I- UPF: Source-UPF or Target-UPF) but not at a new UPF PDU Session Anchor (UPF-PSA), cf. 23.502 §4.9.

If the UPF-PSA is to be changed, for example to a new UPF-PSA geographically closer to the UE, to lower the latency to the Data Network, either Session & Service Continuity (SSC) modes 2 or 3 are used (23.501 §5.6.9, 23.502 §4.3.5). SSC modes are supported for IPv6 PDU Session Type.

In SSC mode 2, the PDU session is released and a new PDU session is established with the new UPF- PSA to the same Data Network (DN). In SSC mode 2, the PDU session is interrupted, leading to the interruption of real-time applications (for example, conversational audio, live video etc.).

In SSC mode 3, the network allows the establishment of UE connectivity via a new UPF-PSA to the same DN before connectivity between the UE and the previous UPF-PSA is released. In SSC mode 3 as the UE is re-anchored at the new UPF-PSA, the UE IPv6 prefix must be changed. In the case of dynamic routing each UPF-PSA must advertise the UE IPv6 Prefix Subnet (e.g. a /48 Subnet) of the UEs which can be reached via this UPF-PSA. In case of static routing the routers in the Data Network must be configured with static routes to each UE IPv6 subnet. The same is true for IPv4 PDU Session Type and for EPS sessions with PDN Type IPv4, IPv6 and IPv4v6 (dual stack).

An IPv4 /32 or IPv6 /64 host route may be advertised for each PDU session, which requires a routing table in the Data Network routers. In practice Mobile Operators avoid host routes (IPv6 /64 and IPv4 Z32) since their leaf switches or data center gateways (to which the UPF is connected) may not have sufficient space in the routing table for millions of UEs. Host routes are only announced at modest scale in private DNs (onto which Private Access Point Names (APN)/Data Network Names (DNN) are mapped but not Public APN/DNNs such as “Internet” or “IMS (IP Multimedia Subsystem)”).

When in SSC mode 3 a new /64 Prefix is therefore assigned to the UE. 3GPP does not specify the mechanisms through which existing IP flows could be moved to the new UPF-PSA. The current state of affairs is that they are dropped.

Further, in SSC mode 3, a UPF-BP (Branching Point) is inserted in the communication, which does may increase latency to the DN, since the UPF-BP will be selected between the source area and the target area.

In summary, SSC modes 2 and 3 do not re-anchor a UE at a new UPF-PSA without interrupting ongoing IP flows.

One solution to re-anchor a UE at a new UPF-PSA without interrupting ongoing IP flows involves the Ethernet PDU Type which has been incorporated in the 3GPP standards (TS 23.501 §5.6.10.2). In the Ethernet PDU type, each MAC (Media Access Control) address representing the UE is bound to a tunnel towards the RAN. The DN no longer needs to route traffic to the IP address (IPv4/IPv6) of the UE, hence the UE can keep its IPv4 address and/or IPv6 prefix while being re-anchored to a new UPF-PSA. To deliver downstream traffic to a UE, the Layer 2 bridged DN may, for example, broadcast an Address Resolution Protocol (ARP) request or IPv6 Neighbour Discovery protocol message to all UPF-PSAs, and the UE will respond with its MAC address. The MAC address is the MAC address of the Data Terminal Equipment (DTE) behind the UE (or Data Communication Equipment, DCE), since the 3GPP UE itself (DCE) has no MAC address. The IP packet is then delivered by the bridged DN via the correct UPF-PSA MAC address to the MAC address behind the UE. This solution requires that the Layer 2 DN switches learn the UPF-PSA MAC address for each MAC-address-behind-UE. This solution does not scale. Various UEs attach to various UPF-PSAs randomly, and each UE moves in between different UPF-PSAs.

RFC 8415 DHCPv6 Reconfigure and RFC 8947 allow a new Link Layer address (MAC address) to be assigned to the DHCP (Dynamic Host Configuration Protocol) clients behind the UE as the UE with Ethernet PDU Type is re-anchored at the new UPF-PSA. These techniques allow the L2 DN interconnecting the UPF-PSAs to scale. A dedicated range of MAC-address-behind-UE can now be assigned to each UPF-PSA instance, and even to VMs or Kubernetes PODs composing such UPF-PSA. The L2 network is then configured with the UPF-PSA-MAC-address for each MAC-address-behind- UE range. The DN may learn these ranges by inspecting upstream frames. The number of L2 forwarding entries is reduced.

While the case has been considered in which a virtual MAC address is used to represent the 3GPP UE itself, as well as the case in which it is the MAC address of an equipment behind the UE (i.e. a device reachable through the UE), for example a laptop connected to the UE’s personal hotspot, 3GPP assumes only the latter for its TS 23.501 §5.6.10.2 Ethernet PDU Type. In the following we will refer to both cases as “User Device MAC address”.

In current 3GPP standards, the 3GPP SMF does not grant any User Device a MAC address; instead the 3GPP SMF requests the UPF to report any Source MAC address found in the ingress upstream (GTP- encapsulated) Ethernet frames, and then creates a DownLink Packet Detection Rule (DL PDR) for that Destination MAC address, referring to the (previously created) Traffic Endpoint ID on the SGi/N6 LAN (Local Area Network).

As a result, 3GPP Ethernet PDU Type does not allow configuring the DN switches with a MAC address range for each UPF. Each UPF has a discontinuous set of MAC addresses “behind” the UEs, and the switches of the DN must use either data-triggered mobility, broadcast ARP or Neighbour Discovery messages to discover the UPF instance for each MAC address.

3GPP has specified the UE address assignment via DHCP, besides via EPS/5GS NAS (Non-Access Stratum).

For any EPS PDN Type (“IPv4”, “IPv6”, “IPv4v6” or “Unstructured”) there’s to date no mechanism to insert the Source MAC address representing the device-behind-the-UE or the UE itself (and allocated by PGW or PGW-C via RFC 8947) in the upstream egress frames towards the SGi-LAN. The Source MAC address transmitted today is the MAC address of the PGW or PGW-U interface itself, not the one representing the UE.

Similarly, for the 5GS PDU Session Types “IPv4”, “IPv6”, “IPv4v6” or “Unstructured”, there’s to date no mechanism to insert the Source MAC address representing the UE (and allocated by SMF) in the upstream egress frames towards the N6-LAN. The Source MAC address transmitted today is the MAC address of the UPF interface itself, not the one representing the UE.

Figure 4 shows a flow chart of a method according to an example embodiment. The method may be performed at a network, e.g., at a control plane function such as a SMF or PGW-C or a user plane function such as a UPF or PGW-U. The method is applicable for IP PDN/PDU Types. In a first step, SI, the method comprises for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment.

In a second step, S2, the method comprises forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

Figure 5 shows a flow chart of a method according to an example embodiment. The method may be performed at a network, e.g., at a control plane function such as a SMF or PGW-C or a user plane function such as a UPF or PGW-U. The method is applicable for Ethernet PDU Types.

In a first step, T1 , the method comprises for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment.

In a second step, T2, the method comprises providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network.

In a third step, T3, the method comprises forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

The Link Layer address may be a MAC address.

For the case where a segment routing label is used, the method may be applicable to a Layer Tree Network.

The payload of frames or the payload of packets is used to indicate the data in the frames or packets after the header, which may be IP or unstructured.

In an example embodiment RFC 4861/8415/8947 may be applied to assign a new Link Layer address as soon as the UE is re-anchored at a new UPF-PSA or component thereof. For example, whenever the UE is re-anchored at a new UPF-PSA, or a new VM/POD therein, IETF RFC 4861 allows the PGW or SMF to send a Router Advertisement message to the UE with the “Managed address configuration” flag set to 1, instructing the UE to contact its DHCPv6 server (RFC 8415). The DHCPv6 server can then use the Reconfigure message and a recent IETF RFC 8947 to assign a Link Layer Address (or a block of link layer addresses) to the UE (MAC addresses).

The PGW or PGW-C could thus, as the idle or active UE moves to a different area where a better PGW or PGW-U exists (better meaning for example with lower latency to the PDN), use this IETF mechanism to grant a new User Device MAC address. The User Device could transmit that MAC address over its E-RAB (DRB + Sl-U tunnel) to the PGW/PGW-U if it is using the 3GPP R16 PDN Type “Ethernet”.

The 5GS SMF may use the same IETF RFC 4861/8415/8947 mechanism. The User Device could only transmit this Source MAC Address if the PDU Session Type is “Ethernet”. And the UPF would only accept downstream traffic to the User Device MAC address if the PDU Session Type is “Ethernet”.

A MAC address representing the UE may be inserted into a User Plane function when the User Device behind the UE cannot transmit any MAC address to the User Plane.

The method may comprise providing the assigned link layer address or assigned segment routing label from a control plane function to a user plane function. The method may comprise providing the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function.

Alternatively, a control plane function may implicitly indicate to a user plane function to assign the link layer address or segment routing label at the user plane. For example, the control plane function may provide an indication, such as e.g., a special slice ID, to a user plane function that the user plane function is to assign the link layer address or segment routing label.

The Packet Flow Control Protocol (PFCP, TS 29.244) allows the Control Plane function (EPS SGW- C/PGW-C or 5GS SMF) to pilot a User Plane function.

In an example embodiment, a Control Plane function (PGW-C or SMF) may instruct the User Plane function (PGW-U or UPF) to insert a MAC address representing the UE (or a Device behind the UE) in its upstream egress frames, forward downstream frames to that MAC address to the correct GTP-U tunnel towards the RAN node (or SGW, or SGSN, or I-UPF, or V-UPF) even when the PDN Type or PDU Type is “IPv4”, “IPv6”, “IPv4v6” or “Unstructured”, and no MAC addresses are thus received from the devices behind the UE. The method may comprise providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type. Thus, 5GS PDU Types “IPv4”, “IPv6”, “IPv4v6” or “Unstructured”, and EPS PDN Types “IPv4”, “IPv6”, “IPv4v6” or “Unstructured”, may establish a 3GPP TS 29.244 PFCP session with PDN Type set to “Ethernet”.

The method may comprise providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

The user plane function may associate an uplink forwarding action rule (FAR) to a downlink packet detection rule (PDR) including the link layer address or segment routing label. The FAR may be associated with the PDR using the Traffic Endpoint ID.

For PFCP PDN Type “Ethernet”, the PFCP Control Plane (CP) function can insert a DownLink Packet Datection Rule (DL PDR) specifying the MAC address representing the UE, and a Traffic Endpoint ID on the SGi/N6 side. For PDU Session Types “IPv4”, “IPv6”, “IPv4v6” and “Unstructured, the UpLink Forwarding Action Rule (FAR) may be correlated with the DL PDR by referring to that same Traffic Endpoint ID in the Forwarding Parameters of the FAR. When that link is established, the User Plane (UP) function uses the MAC address representing the UE as the Source MAC address of upstream egress Ethernet frames towards the SGi-LAN/N6-LAN.

These steps allow the Control Plane function to obtain the desired behaviour in the User Plane, without modifying the Protocol itself (messages & attributes).

The method may provide low-latency EPS and 5GS services and content accessible through a highly scalable PDN interconnecting a large number of distributed PGW-Us or a highly scalable DN interconnecting a large number of distributed UPF-PSAs since the UE can be re-anchored at a better UPF-PSA or PGW-U (e.g., one which provides low latency) without interrupting ongoing IP flows.

Figure 6 shows a schematic diagram of a 5GS in which a UE is re-anchored at a new UPF or UPF component instance. The UE is re-anchored at the UPF or UPF component without an Ethernet PDY Type, UE IP address subnets per UPF, IP host routes to the UEs (/32. /64), 3GPP mode 2 or 3 to change the UE IPv6 prefix upon mobility, the need to move ongoing IP flows to the new IPv6 prefix or 3GPP Branching Point UPF. In this example scenario, the UE is initially in Tracking Area Y and is anchored at UPF1.

A Link Layer Address (MAC Address) is assigned and reassigned to the UE as it moves in between areas of the network, in this case from Tracking Area Y to Tracking Area Z where a more optimal UPF, UPF 2, exists.

Previously, in the 3GPP standard, the SMF would have had to change the UE IPv6 prefix when replacing the UPF-PSA (TS 23.501 §5.6.4.3). The standard does not state how existing IP flows are moved.

In the example scenario shown in Figure 6, the SMF requests the UE to contact its DHCP server, which in this case is a DHCPv6 server within the SMF itself. That DHCPv6 server then selects an unused MAC address representing the UE within a MAC address range that is specific for each UPF instance (in this case MAC@ range 2 is specific to UPF 2). RFC 8947 may also be used to grant a MAC address range to the DHCPv6 client or relay in the UE. For example, the SMF sends a RFC 4861 RA to UE and RFC 8415 DHCPv6 Reconfigure +GTP-U-dependent RFC8947 Link Layer Dares when UPF or N3 RAND F-TEID IP address changes. The SMF uses N4 PFCP with Ethernet PDN Type to bind that MAC address to the N3 GTP-U tunnel. The PFCP UL FAR is linked to the DL PDR with Ethernet Packet Filter in order for the UPF to write the UL Source MAC address.

The SMF, having received a Ni l request for a PDU Session Type “IPv4”, “IPv6”, “IPv4v6” or “Unstructured” (or the PGW-C in EPS, or combined SMF/PGW-C), requests the UPF (or PGW-U, or combined UPF/PGW-U) to establish a PFCP Session with PDN Type = “Ethernet”.

Using a method such as in the example embodiment shown in Figures 4 and 5, the UE many be reanchored at the UPF or UPF component without an Ethernet PDU Type, UE IP address subnets per UPF, IP host routes to the UEs (/32, /64), 3GPP mode 2 or 3 to change the UE IPv6 prefix upon mobility, the need to move ongoing IP flows to the new IPv6 prefix or 3GPP Branching point UPF.

Figure 7 is an extension of the example shown in Figure 6 showing the case for both EPS and 5GS and where a UPF change is not always required, the allocation of the MAC address is a decision of the control plane function (SMF or SPGW-C) for a different instance of a UP function or an instance of a component of a user plane function.

Figure 8 shows an example of the step of the SMF requesting the UPF to establish a PFCP session with PDN Type = “Ethernet in more detail. In the example embodiment shown in Figure 8, the CP function instructs the UP function to link the UL FAR 1 to the Traffic Endpoint ID “Y”, the same as for the DL PDR 2. The CP function sends a 3GPP TS 28.244 PFPC Session Establishment Request to the UP function. The Request includes either Ethernet PDU Session Info in Source Interface or N6 Ethernet PDU Session Info in the 3GPP Interface Type.

This allows the UP to determine the MAC address (and other Ethernet attributes such as Ethertype, VLAN tags, etc) to be applied for upstream egress frames to the SGi/N6 LAN.

The method may enable mobility between UP function instances within a single PLMN, but also in between two PLMNs accessing a shared Data Network, such as, for example, a Global IPX network interconnecting MNOs or a Data Network interconnecting a MNO and an Enterprise operating a Network-in-a-Box.

For example, the concept may be applicable to the mobility between the Network Function Component (NFC) instances (VMs, PODs) of a single UPF instance. A MAC address range may be allocated to each Component and the Data Network (e.g., a Data Center Overlay network) can send downstream traffic to the right NFC instance for each UE, without having to learn any IP route to the UE (nor host routes, nor subnets).

The global UE address space (Public IPv4, IPv6) no longer needs to be subnetted and this provides improvements within MNO networks, for international roaming, for mobility between private and public networks, mobility between EPS and 5GS, between 5GS and future 6GS, etc.

Inbound international roamers may, for example, access local content (e.g., Augmented Reality...) through their synthesized User Device MAC address (representing them in a local visited UPF with local N6 Data Network), while they remain anchored at the PGW-U or UPF-PSA in the Home PLMN (where their IPv6 subnet is announced and high-latency content continues to be delivered). Otherwise, all IPv6 content would have to use the high-latency route via the(UPF-PSA in the Home PLMN since NAT66 cannot be used to break out locally from the UPF in the Visited PLMN.

The UE MAC address space may be divided over different UPF/PGW-U instances, different operators, organizations or among the NFC instances of a single UPF/PGW-U.

The UE MAC address may be granted in (sub)ranges with a different purpose than the lowest latency.

A MAC address (sub)range could for example represent a Slice of the network. That is, the link layer address or segment routing label may be from a range associated with a group of multiple user equipment or multiple devices reachable through the user equipment, a range associated with a slice of the network, a range associated with the network, a range associated with an instance of the user plane function or a range associated with an instance of a component of the user plane function (such as a Virtual Machine or Kubernetes Pod).

The method may provide low-latency EPS and 5GS services and content accessible through a highly scalable PDN interconnecting a large number of distributed EPS PGW-Us or a highly scalable DN interconnecting a large number of distributed 5GS UPF-PSAs.

The method may be implemented at a control apparatus as described with reference to Figure 3.

An apparatus may comprise means for, for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

Alternatively or in addition, an apparatus may comprise means for, for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment, providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

It is noted that whilst embodiments have been described in relation to LTE and 5G NR, similar principles can be applied in relation to other networks and communication systems. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

In general, the various example embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention 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 invention is not limited thereto. While various aspects of the invention 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.

The embodiments of this invention 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 disk 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 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. Example embodiments of the inventions 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 embodiment of this invention. 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. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

List of abbreviations

5GC 5G Core

5GS 5G System = NG-RAN + 5GC

CP Control Plane

DHCP Dynamic Host Configuration Protocol (for IPv4)

DHCPv6 DHCP for IPv6

DL Downlink

DN Data Network

DRB Data Radio Bearer

EPC Evolved Packet Core

EPS Evolved Packet System

F-SEID Fully qualified SEID (= IP address + SEID)

F-TEID Fully qualified TEID (= IP address + TEID)

FAR PFCP Forwarding Action Rule

I-UPF Intermediate UPF

NF Network Function

NFC NF Component (VM, POD)

PDN Packet Data Network

PDR PFCP Packet Detection Rule

PFCP Packet Flow Control Protocol

PGW PDN Gateway PGW-CPGW Control plane function

PGW-U PGW User plane function

RA Router Advertisement

SMF Session Management Function SEID (PFCP) Session Endpoint ID

TEID (GTP) Traffic Endpoint ID

UE User Equipment

UL Uplink

UP User Plane UPF User Plane Function

UPF-BP UPF Branching Point

UPF-PSA UPF PDU Session Anchor

VM Virtual Machine

Claims

1. An apparatus, said apparatus comprising means for: for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment; and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.

2. An apparatus, said apparatus comprising means for: for a user equipment having communicated a link layer address to a network, assigning a link layer address or segment routing label to a device reachable through the user equipment; providing an indication from the network to the device to request the assigned link layer address or segment routing label from a server of the network; and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the device via a radio access network directly coupled to said apparatus.

3. An apparatus according to claim 1 or claim 2 comprising means for providing the assigned link layer address or assigned segment routing label from a control plane function to a user plane function or for providing an indication from the control plane function to the user plane function to assign the link layer address or segment routing label at the user plane.

4. An apparatus according to claim 3 comprising means for providing the assigned link layer address or segment routing label via a 3GPP Packet Flow Control Protocol, PFCP, to the user plane function.

5. An apparatus according to claim 4 comprising means for providing an indication from the control plane function to the user plane function that a PFCP packet data network, PDN, type or protocol data unit, PDU, type is Ethernet when the PDN type or PDU is an IP or unstructured PDN or PDU type.

6. An apparatus according to claim 5 where the user plane function associates an uplink forwarding action rule to a downlink packet detection rule including the link layer address or segment routing label. An apparatus according to any of claims 1-6 where the link layer address or segment routing label is from a range associated with a group of multiple user equipment or multiple devices reachable through the user equipment An apparatus according to any of claims 1-6 where the link layer address or segment routing label is from a range associated with a slice of the network An apparatus according to any of claims 1-6 where the link layer address or segment routing label is from a range associated with the network An apparatus according to any of claims 3-6 where the link layer address or segment routing label is from a range associated with an instance of the user plane function. An apparatus according to any of claims 3-6 where the link layer address or segment routing label is from a range associated with an instance of a component of the user plane function. An apparatus according to any of claims 1 to 11, where the link layer address is a Media Access Control, MAC, address. A method comprising: for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment; and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus. An apparatus comprising: at least one processor and at least one memory including a computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the apparatus at least to: for a user equipment not having communicated a link layer address to a network, assign a link layer address or segment routing label to the user equipment or a device reachable through the user equipment; and forward a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus. A computer readable medium comprising program instructions for causing an apparatus to perform at least the following: for a user equipment not having communicated a link layer address to a network, assigning a link layer address or segment routing label to the user equipment or a device reachable through the user equipment; and forwarding a payload of frames containing the assigned link layer address or a payload of packets containing the assigned segment routing label to the user equipment via a radio access network directly coupled to the apparatus.