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Content for  TS 23.501  Word version:  18.0.0

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3  Definitions and abbreviationsp. 25

3.1  Definitionsp. 25

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
5G VN Group:
A set of UEs using private communication for 5G LAN-type service.
5G Access Network:
An access network comprising a NG-RAN and/or non-3GPP AN connecting to a 5G Core Network.
5G Access Stratum-based Time Distribution:
A time synchronization distribution method that is used by an NG-RAN to provide the 5GS time to the UE(s) over the radio interface using procedures specified in TS 38.331.
5G Core Network:
The core network specified in the present document. It connects to a 5G Access Network.
5G LAN-Type Service:
A service over the 5G system offering private communication using IP and/or non-IP type communications.
5G LAN-Virtual Network:
A virtual network over the 5G system capable of supporting 5G LAN-type service.
The 5G NSWO is the capability provided by 5G system and by UE to enable the connection to a WLAN access network using 5GS credentials without registration to 5GS.
5G QoS Flow or QoS Flow:
The finest granularity for QoS forwarding treatment in the 5G System. All traffic mapped to the same 5G QoS Flow receive the same forwarding treatment (e.g. scheduling policy, queue management policy, rate shaping policy, RLC configuration, etc.). Providing different QoS forwarding treatment requires separate 5G QoS Flow.
5G QoS Identifier:
A scalar that is used as a reference to a specific QoS forwarding behaviour (e.g. packet loss rate, packet delay budget) to be provided to a 5G QoS Flow. This may be implemented in the access network by the 5QI referencing node specific parameters that control the QoS forwarding treatment (e.g. scheduling weights, admission thresholds, queue management thresholds, link layer protocol configuration, etc.).
5G System:
3GPP system consisting of 5G Access Network (AN), 5G Core Network and UE.
The 5G-BRG is a 5G-RG defined in BBF.
The 5G-CRG is a 5G-RG specified in DOCSIS MULPI [89].
A 5G-RG is a RG capable of connecting to 5GC playing the role of a UE with regard to the 5G core. It supports secure element and exchanges N1 signalling with 5GC. The 5G-RG can be either a 5G-BRG or 5G-CRG.
Access Traffic Steering:
The procedure that selects an access network for a new data flow and transfers the traffic of this data flow over the selected access network. Access traffic steering is applicable between one 3GPP access and one non-3GPP access.
Access Traffic Switching:
The procedure that moves all traffic of an ongoing data flow from one access network to another access network in a way that maintains the continuity of the data flow. Access traffic switching is applicable between one 3GPP access and one non-3GPP access.
Access Traffic Splitting:
The procedure that splits the traffic of a data flow across multiple access networks. When traffic splitting is applied to a data flow, some traffic of the data flow is transferred via one access and some other traffic of the same data flow is transferred via another access. Access traffic splitting is applicable between one 3GPP access and one non-3GPP access.
Allowed NSSAI:
Indicating the S-NSSAIs values the UE could use in the Serving PLMN in the current Registration Area.
Allowed Area:
Area where the UE is allowed to initiate communication as specified in clause
AMF Region:
An AMF Region consists of one or multiple AMF Sets.
AMF Set:
An AMF Set consists of some AMFs that serve a given area and Network Slice(s). AMF Set is unique within an AMF Region and it comprises of AMFs that support the same Network Slice(s). Multiple AMF Sets may be defined per AMF Region. The AMF instances in the same AMF Set may be geographically distributed but have access to the same context data.
Application Identifier:
An identifier that can be mapped to a specific application traffic detection rule.
AUSF Group ID:
This refers to one or more AUSF instances managing a specific set of SUPIs. An AUSF Group consists of one or multiple AUSF Sets.
Binding Indication:
Information included by a NF service producer to a NF service consumer in request responses or notifications to convey the scope within which selection/reselection of target NF/NF Services may be performed, or information included by the NF service consumer in requests or subscriptions to convey the scope within which selection/reselection of notification targets or the selection of other service(s) that the NF consumer produces for the same data context may be performed. See clause
BSF Group ID:
This refers to one or more BSF instances managing a specific set of SUPIs or GPSIs. A BSF Group consists of one or multiple BSF Sets.
Configured NSSAI:
NSSAI provisioned in the UE applicable to one or more PLMNs.
CHF Group ID:
This refers to one or more CHF instances managing a specific set of SUPIs.
Credentials Holder:
Entity which authenticates and authorizes access to an SNPN separate from the Credentials Holder.
Default UE credentials:
Information configured in the UE to make the UE uniquely identifiable and verifiably secure to perform UE onboarding.
Default Credentials Server (DCS):
An entity that can perform authentication based on the Default UE credentials or provide means for another entity to perform authentication based on the Default UE credentials.
Delegated Discovery:
This refers to delegating the discovery and associated selection of NF instances or NF service instances to an SCP.
Direct Communication:
This refers to the communication between NFs or NF services without using an SCP.
Disaster Condition:
See definition in TS 22.261.
Disaster Inbound Roamer:
See definition in TS 22.261.
Disaster Roaming:
See definition in TS 22.261.
DN Access Identifier (DNAI):
Identifier of a user plane access to one or more DN(s) where applications are deployed.
Emergency Registered:
A UE is considered Emergency Registered over an Access Type in a PLMN when registered for emergency services only over this Access Type in this PLMN.
Endpoint Address:
An address in the format of an IP address or FQDN, which is used to determine the host/authority part of the target URI. This Target URI is used to access an NF service (i.e. to invoke service operations) of an NF service producer or for notifications to an NF service consumer.
as defined in TS 37.340.
Expected UE Behaviour:
Set of parameters provisioned by an external party to 5G network functions on the foreseen or expected UE behaviour, see clause 5.20.
Fixed Network Residential Gateway:
A Fixed Network RG (FN-RG) is a RG that it does not support N1 signalling and it is not 5GC capable.
Fixed Network Broadband Residential Gateway:
A Fixed Network RG (FN-BRG) is a FN-RG specified in BBF TR-124 [90].
Fixed Network Cable Residential Gateway:
A Fixed Network Cable RG (FN-CRG) is a FN-RG with cable modem specified in DOCSIS MULPI [89].
Forbidden Area:
An area where the UE is not allowed to initiate communication as specified in clause
GBR QoS Flow:
A QoS Flow using the GBR resource type or the Delay-critical GBR resource type and requiring guaranteed flow bit rate.
Group ID for Network Selection (GIN):
An identifier used during SNPN selection to enhance the likelihood of selecting a preferred SNPN that supports a Default Credentials Server or a Credentials Holder.
(g)PTP-based Time Distribution:
a method to distribute timing among entities in a (g)PTP domain using PTP messages generated by a GM (in the case the GM is external to 5GS) or by 5GS (in the case the 5GS acts as a GM for a given (g)PTP domain). Possible dependencies between (g)PTP-based Time Distribution and 5G Access Stratum-based Time Distribution are described in clause 5.27.1. The synchronization process is described in clause 5.27.1 and follows the applicable profiles of IEEE Std 802.1AS [104] or IEEE Std 1588 [126].
Home Network Public Key Identifier:
An identifier used to indicate which public/private key pair is used for SUPI protection and de-concealment of the SUCI as specified in TS 23.003.
This is a NG-RAN node that supports Integrated access and backhaul (IAB) feature and provides connection to the core network to IAB-nodes. It supports the CU function of the CU/DU architecture for IAB defined in TS 38.401.
A relay node that supports wireless in-band and out-of-band relaying of NR access traffic via NR Uu backhaul links. It supports the UE function and the DU function of the CU/DU architecture for IAB defined in TS 38.401.
Indirect Communication:
This refers to the communication between NFs or NF services via an SCP.
Initial Registration:
UE registration in RM-DEREGISTERED state as specified in clause 5.3.2.
Intermediate SMF (I-SMF):
An SMF that is inserted to support a PDU session as the UE is located in an area which cannot be controlled by the original SMF because the UPF(s) belong to a different SMF Service Area.
Local Area Data Network:
a DN that is accessible by the UE only in specific locations, that provides connectivity to a specific DNN, and whose availability is provided to the UE.
Local Break Out (LBO):
Roaming scenario for a PDU Session where the PDU Session Anchor and its controlling SMF are located in the serving PLMN (VPLMN).
a 3GPP RAT type Identifier used in the Core Network only, which is a sub-type of E-UTRA RAT type, and defined to identify in the Core Network the E-UTRA when used by a UE indicating Category M.
MA PDU Session:
A PDU Session that provides a PDU connectivity service, which can use one access network at a time, or simultaneously one 3GPP access network and one non-3GPP access network.
Mobile Base Station Relay:
A mobile base station acts as a relay between a UE and the 5G network. Such mobile base station relay can for example be mounted on a moving vehicle and serve UEs that can be located inside or outside the vehicle (or entering/leaving the vehicle). See description of TS 22.261. A mobile Base Station Relay is supported in 5GS with the IAB-architecture with mobility as specified in clause 5.35A and that described in TS 38.401.
Mobility Pattern:
Network concept of determining within the AMF the UE mobility parameters as specified in clause
Mobility Registration Update:
UE re-registration when entering new TA outside the TAI List as specified in clause 5.3.2.
MPS-subscribed UE:
A UE having a USIM with MPS subscription.
Multi-USIM UE:
A UE with multiple USIMs, capable of maintaining a separate registration state with a PLMN for each USIM at least over 3GPP Access and supporting one or more of the features described in clause 5.38.
NB-IoT UE Priority:
Numerical value used by the NG-RAN to prioritise between different UEs accessing via NB-IoT.
NGAP UE association:
The logical per UE association between a 5G-AN node and an AMF.
NGAP UE-TNLA-binding:
The binding between a NGAP UE association and a specific TNL association for a given UE.
Network Function:
A 3GPP adopted or 3GPP defined processing function in a network, which has defined functional behaviour and 3GPP defined interfaces.
Network Instance:
Information identifying a domain. Used by the UPF for traffic detection and routing.
Network Slice:
A logical network that provides specific network capabilities and network characteristics.
Network Slice instance:
A set of Network Function instances and the required resources (e.g. compute, storage and networking resources) which form a deployed Network Slice.
Non-GBR QoS Flow:
A QoS Flow using the Non-GBR resource type and not requiring guaranteed flow bit rate.
an identifier for identifying the Core Network part of a Network Slice instance when multiple Network Slice instances of the same Network Slice are deployed, and there is a need to differentiate between them in the 5GC.
NF instance:
an identifiable instance of the NF.
NF service:
a functionality exposed by a NF through a service based interface and consumed by other authorized NFs.
NF service instance:
an identifiable instance of the NF service.
NF service operation:
An elementary unit a NF service is composed of.
NF Service Set:
A group of interchangeable NF service instances of the same service type within an NF instance. The NF service instances in the same NF Service Set have access to the same context data.
NF Set:
A group of interchangeable NF instances of the same type, supporting the same services and the same Network Slice(s). The NF instances in the same NF Set may be geographically distributed but have access to the same context data.
A radio access network that supports one or more of the following options with the common characteristics that it connects to 5GC:
  1. Standalone New Radio.
  2. New Radio is the anchor with E-UTRA extensions.
  3. Standalone E-UTRA.
  4. E-UTRA is the anchor with New Radio extensions.
Non-Allowed Area:
Area where the UE is allowed to initiate Registration procedure but no other communication as specified in clause
Non-Public Network:
See definition in TS 22.261.
Non-Seamless Non-3GPP offload:
The offload of user plane traffic via non-3GPP access without traversing either N3IWF/TNGF or UPF.
Non-Seamless WLAN offload:
Non-Seamless Non-3GPP offload when the non-3GPP access network is WLAN.
Onboarding Network:
Either a PLMN enabling Remote Provisioning for a registered UE, or an Onboarding SNPN.
Onboarding Standalone Non-Public Network:
An SNPN providing Onboarding access and enabling Remote Provisioning for a UE registered for Onboarding as specified in clause of TS 23.502.
PCF Group ID:
This refers to one or more PCF instances managing a specific set of SUPIs. A PCF Group consists of one or multiple PCF Sets.
Pending NSSAI:
NSSAI provided by the Serving PLMN during a Registration procedure, indicating the S-NSSAI(s) for which the network slice-specific authentication and authorization procedure is pending.
PDU Connectivity Service:
A service that provides exchange of PDUs between a UE and a Data Network.
PDU Session:
Association between the UE and a Data Network that provides a PDU connectivity service.
PDU Session Type:
The type of PDU Session which can be IPv4, IPv6, IPv4v6, Ethernet or Unstructured.
Periodic Registration Update:
UE re-registration at expiry of periodic registration timer as specified in clause 5.3.2.
PLMN with Disaster Condition:
A PLMN to which a Disaster Condition applies.
Pre-configured 5QI:
Pre-defined QoS characteristics configured in the AN and 5GC and referenced via a non-standardized 5QI value.
Private communication:
See definition in TS 22.261.
Provisioning Server:
Entity that provisions network credentials and other data in the UE to enable SNPN access.
PTP domain:
As defined in IEEE Std 1588 [126].
Public network integrated NPN:
A non-public network deployed with the support of a PLMN.
(Radio) Access Network:
See 5G Access Network.
RAT type:
Identifies the transmission technology used in the access network for both 3GPP accesses and non-3GPP Accesses, for example, NR, NB-IOT, Untrusted Non-3GPP, Trusted Non-3GPP, Trusted IEEE 802.11 Non-3GPP access, Wireline, Wireline-Cable, Wireline-BBF, etc.
NR RedCap:
a 3GPP RAT type Identifier used in the Core Network only, which is a sub-type of NR RAT type, and defined to identify in the Core Network the NR when used by a UE indicating NR RedCap.
Requested NSSAI:
NSSAI provided by the UE to the Serving PLMN during registration.
Residential Gateway:
The Residential Gateway (RG) is a device providing, for example voice, data, broadcast video, video on demand, to other devices in customer premises.
Routing Binding Indication:
Information included in a request or notification and that can be used by the SCP for discovery and associated selection to of a suitable target. See clauses and 7.1.2
Routing Indicator:
Indicator that allows together with SUCI/SUPI Home Network Identifier to route network signalling to AUSF and UDM instances capable to serve the subscriber.
SCP Domain:
A configured group of one or more SCP(s) and zero or more NF instances(s). An SCP within the group can communicate with any NF instance or SCP within the same group directly, i.e. without passing through an intermediate SCP.
SNPN-enabled UE:
A UE configured to use stand-alone Non-Public Networks.
SNPN access mode:
A UE operating in SNPN access mode only selects stand-alone Non-Public Networks.
Service based interface:
It represents how a set of services is provided/exposed by a given NF.
Service Continuity:
The uninterrupted user experience of a service, including the cases where the IP address and/or anchoring point change.
Service Data Flow Filter:
A set of packet flow header parameter values/ranges used to identify one or more of the (IP or Ethernet) packet flows constituting a Service Data Flow.
Service Data Flow Template:
The set of Service Data Flow filters in a policy rule or an application identifier in a policy rule referring to an application detection filter, required for defining a Service Data Flow.
Session Continuity:
The continuity of a PDU Session. For PDU Session of IPv4 or IPv6 or IPv4v6 type "session continuity" implies that the IP address is preserved for the lifetime of the PDU Session.
SMF Service Area:
The collection of UPF Service Areas of all UPFs which can be controlled by one SMF.
PLMN ID and NID identifying an SNPN.
Stand-alone Non-Public Network:
A non-public network not relying on network functions provided by a PLMN
Subscribed S-NSSAI:
S-NSSAI based on subscriber information, which a UE is subscribed to use in a PLMN
Subscription Owner Standalone Non-Public Network:
A Standalone Non-Public Network owning the subscription of a UE and providing subscription data to the UE via a Provisioning Server during the onboarding procedure.
Survival Time:
The time that an application consuming a communication service may continue without an anticipated message.
Target NSSAI:
NSSAI provided by the Serving PLMN to the NG-RAN to cause the NG-RAN to attempt to steer the UE to a cell supporting the Network Slices identified by the S-NSSAIs in this NSSAI. See clause for more details.
Time Sensitive Communication (TSC):
A communication service that supports deterministic communication (i.e. which ensures a maximum delay) and/or isochronous communication with high reliability and availability. It is about providing packet transport with QoS characteristics such as bounds on latency, loss, and reliability, where end systems and relay/transmit nodes may or may not be strictly synchronized.
TSN working domain:
Synchronization domain for a localized set of devices collaborating on a specific task or work function in a TSN network, corresponding to a gPTP domain defined in IEEE 802.1AS [104].
UDM Group ID:
This refers to one or more UDM instances managing a specific set of SUPIs. An UDM Group consists of one or multiple UDM Sets.
UDR Group ID:
This refers to one or more UDR instances managing a specific set of SUPIs. An UDR Group consists of one or multiple UDR Sets.
UE-DS-TT Residence Time:
The time taken within the UE and DS-TT to forward a packet, i.e. between the ingress of the UE and the DS-TT port in the DL direction, or between the DS-TT port and the egress of the UE in the UL direction. UE-DS-TT Residence Time is provided at the time of PDU Session Establishment by the UE to the network.
UPF Service Area:
An area consisting of one or more TA(s) within which PDU Session associated with the UPF can be served by (R)AN nodes via a N3 interface between the (R)AN and the UPF without need to add a new UPF in between or to remove/re-allocate the UPF.
Uplink Classifier:
UPF functionality that aims at diverting Uplink traffic, based on filter rules provided by SMF, towards Data Network.
In the RAN, WB-E-UTRA is the part of E-UTRA that excludes NB-IoT. In the Core Network, WB-E-UTRA also excludes LTE-M.
Wireline 5G Access Network:
The Wireline 5G Access Network (W-5GAN) is a wireline AN that connects to a 5GC via N2 and N3 reference points. The W-5GAN can be either a W-5GBAN or W-5GCAN.
Wireline 5G Cable Access Network:
The Wireline 5G Cable Access Network (W-5GCAN) is the Access Network defined in CableLabs.
Wireline BBF Access Network:
The Wireline 5G BBF Access Network (W-5GBAN) is the Access Network defined in BBF.
Wireline Access Gateway Function (W-AGF):
The Wireline Access Gateway Function (W-AGF) is a Network function in W-5GAN that provides connectivity to the 5G Core to 5G-RG and FN-RG.

3.2  Abbreviationsp. 31

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
5G Core Network
5G Direct Discovery Name Management Function
5G Local Area Network
5G System
5G Access Network
5G Access Network Packet Delay Budget
5G-Equipment Identity Register
5G Globally Unique Temporary Identifier
5G Broadband Residential Gateway
5G Cable Residential Gateway
5G Grand Master
5G Non-Seamless WLAN offload
5G Residential Gateway
5G S-Temporary Mobile Subscription Identifier
5G Virtual Network
5G QoS Identifier
Analytics Data Repository Function
Application Function
Authentication and Key Management for Applications
Analytics Logical Function
Access and Mobility Management Function
Access Stratum
Access Traffic Steering, Switching, Splitting
ATSSS Low-Layer
Authentication Server Function
Best Master Clock Algorithm
Binding Support Function
Closed Access Group
Common API Framework for 3GPP northbound APIs
Credentials Holder
Charging Function
Core Network Packet Delay Budget
Control Plane
Dual Active Protocol Stacks
Data Collection Coordination Function
Default Credentials Server
Data Network
DN Access Identifier
Data Network Name
Discontinuous Reception
Device-side TSN translator
Early Admission Control
evolved Packet Data Gateway
EPS Bearer Identity
Extended Unique Identifier
Forwarding Action Rule
Fixed Network Broadband RG
Fixed Network Cable RG
Fixed Network RG
Fully Qualified Domain Name
Generic Bootstrapping Architecture
Geostationary Orbit
Guaranteed Flow Bit Rate
Group ID for Network Selection
Gateway Mobile Location Centre
Generic Public Subscription Identifier
Globally Unique AMF Identifier
High-Performance Machine-Type Communications
Home Routed (roaming)
Integrated access and backhaul
IMEI Type Allocation Code
Inter PLMN UP Security
Intermediate SMF
Intermediate UPF
Local Area Data Network
Local Break Out (roaming)
Low Earth Orbit
Location Management Function
Level of Automation
LTE Positioning Protocol
Location Retrieval Function
Multicast/Broadcast Service
Multicast/Broadcast Service Function
Mobile Base Station Relay
Multicast/Broadcast Service Transport Function
Multicast/Broadcast Session Management Function
Multicast/Broadcast User Plane Function
Medium Earth Orbit
Messaging Framework Adaptor Function
Mission Critical Service
Maximum Data Burst Volume
Maximum Flow Bit Rate
Mobile Initiated Connection Only
Minimization of Service Interruption
Machine Learning
Multimedia Priority Service
Multi-Path TCP Protocol
Model Training Logical Function
Non-3GPP InterWorking Function
Non-5G-Capable over WLAN
Network Access Identifier
Network Exposure Function
Network Function
Next Generation Application Protocol
Network identifier
Non-Public Network
New Radio
Network Repository Function
Network Slice Admission Control
Network Slice Admission Control Function
Network Slice AS Group
Network Slice Instance Identifier
Network Slice-Specific Authentication and Authorization
Network Slice-specific and SNPN Authentication and Authorization Function
Network Slice Selection Assistance Information
Network Slice Selection Function
Network Slice Selection Policy
Network-side TSN translator
Network Slice Simultaneous Registration Group
Non-Seamless WLAN offload
Non-Seamless WLAN offload Function
Network Data Analytics Function
Onboarding Network
Onboarding Standalone Non-Public Network
Policy Control Function
Packet Delay Budget
Packet Detection Rule
Protocol Data Unit
Permanent Equipment Identifier
Packet Error Rate
Packet Flow Description
Public Network Integrated Non-Public Network
Paging Policy Differentiation
Paging Proceed Flag
Paging Policy Indicator
PDU Session Anchor
Precision Time Protocol
Provisioning Server
QoS Flow Identifier
Quality of Experience
Radio Capabilities Signalling optimisation
(Radio) Access Network
Residential Gateway
Remote Interference Management
Reflective QoS Attribute
Reflective QoS Indication
Redundancy Sequence Number
Standalone New Radio
Service Based Architecture
Service Based Interface
Service Communication Proxy
Slice Differentiator
Security Anchor Functionality
Security Edge Protection Proxy
Session Management Function
Short Message Service Function
Sequence Number
Stand-alone Non-Public Network
Single Network Slice Selection Assistance Information
Subscription Owner Standalone Non-Public Network
Session and Service Continuity
Session and Service Continuity Mode Selection Policy
Slice/Service Type
Subscription Concealed Identifier
Subscription Permanent Identifier
Software Version
Tracking Area
Tracking Area Identity
Trusted Non-3GPP Access Network
Trusted Non-3GPP Access Point
Trusted Non-3GPP Gateway Function
Transport Network Layer
Transport Network Layer Association
Time Sensitive Communication
TSC Assistance Information
Time Sensitive Communication and Time Synchronization Function
Time Sensitive Networking
TSN Grand Master
Traffic Steering Policy
TSN Translator
Trusted WLAN Interworking Function
Uncrewed Aerial System Network Function
UE radio Capability Management Function
Unified Data Management
Unified Data Repository
Unstructured Data Storage Function
Uplink Classifier
User Plane Function
Ultra Reliable Low Latency Communication
UE Reachability Request Parameter for AMF
UE Route Selection Policy
VLAN Identifier
Virtual Local Area Network
Wireline 5G Access Network
Wireline BBF Access Network
Wireline 5G Cable Access Network
Wireline Access Gateway Function

4  Architecture model and conceptsp. 34

4.1  General conceptsp. 34

The 5G System architecture is defined to support data connectivity and services enabling deployments to use techniques such as e.g. Network Function Virtualization and Software Defined Networking. The 5G System architecture shall leverage service-based interactions between Control Plane (CP) Network Functions where identified. Some key principles and concept are to:
  • Separate the User Plane (UP) functions from the Control Plane (CP) functions, allowing independent scalability, evolution and flexible deployments e.g. centralized location or distributed (remote) location.
  • Modularize the function design, e.g. to enable flexible and efficient network slicing.
  • Wherever applicable, define procedures (i.e. the set of interactions between network functions) as services, so that their re-use is possible.
  • Enable each Network Function and its Network Function Services to interact with other NF and its Network Function Services directly or indirectly via a Service Communication Proxy if required. The architecture does not preclude the use of another intermediate function to help route Control Plane messages (e.g. like a DRA).
  • Minimize dependencies between the Access Network (AN) and the Core Network (CN). The architecture is defined with a converged core network with a common AN - CN interface which integrates different Access Types e.g. 3GPP access and non-3GPP access.
  • Support a unified authentication framework.
  • Support "stateless" NFs, where the "compute" resource is decoupled from the "storage" resource.
  • Support capability exposure.
  • Support concurrent access to local and centralized services. To support low latency services and local access to data networks, UP functions can be deployed close to the Access Network.
  • Support roaming with both Home routed traffic as well as Local breakout traffic in the visited PLMN.

4.2  Architecture reference modelp. 35

4.2.1  Generalp. 35

This specification describes the architecture for the 5G System. The 5G architecture is defined as service-based and the interaction between network functions is represented in two ways.
  • A service-based representation, where network functions (e.g. AMF) within the Control Plane enables other authorized network functions to access their services. This representation also includes point-to-point reference points where necessary.
  • A reference point representation, shows the interaction exist between the NF services in the network functions described by point-to-point reference point (e.g. N11) between any two network functions (e.g. AMF and SMF).
Service-based interfaces are listed in clause 4.2.6. Reference points are listed in clause 4.2.7.
Network functions within the 5GC Control Plane shall only use service-based interfaces for their interactions.
NFs and NF services can communicate directly, referred to as Direct Communication, or indirectly via the SCP, referred to as Indirect Communication. For more information on communication options, see Annex E and clauses under clause 6.3.1 and clause 7.1.2.
In addition to the architecture descriptions in clause 4, the following areas are further described in other specifications:

4.2.2  Network Functions and entitiesp. 36

The 5G System architecture consists of the following network functions (NF):
  • Authentication Server Function (AUSF).
  • Access and Mobility Management Function (AMF).
  • Data Network (DN), e.g. operator services, Internet access or 3rd party services.
  • Unstructured Data Storage Function (UDSF).
  • Network Exposure Function (NEF).
  • Network Repository Function (NRF).
  • Network Slice Admission Control Function (NSACF).
  • Network Slice-specific and SNPN Authentication and Authorization Function (NSSAAF).
  • Network Slice Selection Function (NSSF).
  • Policy Control Function (PCF).
  • Session Management Function (SMF).
  • Unified Data Management (UDM).
  • Unified Data Repository (UDR).
  • User Plane Function (UPF).
  • UE radio Capability Management Function (UCMF).
  • Application Function (AF).
  • User Equipment (UE).
  • (Radio) Access Network ((R)AN).
  • 5G-Equipment Identity Register (5G-EIR).
  • Network Data Analytics Function (NWDAF).
  • CHarging Function (CHF).
  • Time Sensitive Networking AF (TSN AF).
  • Time Sensitive Communication and Time Synchronization Function (TSCTSF).
  • Data Collection Coordination Function (DCCF).
  • Analytics Data Repository Function (ADRF).
  • Messaging Framework Adaptor Function (MFAF).
  • Non-Seamless WLAN Offload Function (NSWOF).
  • Edge Application Server Discovery Function (EASDF).
The 5G System architecture also comprises the following network entities:
  • Service Communication Proxy (SCP).
  • Security Edge Protection Proxy (SEPP).
The functional descriptions of these Network Functions and entities are specified in clause 6.
  • Non-3GPP InterWorking Function (N3IWF).
  • Trusted Non-3GPP Gateway Function (TNGF).
  • Wireline Access Gateway Function (W-AGF).
  • Trusted WLAN Interworking Function (TWIF).

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