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5G Core Overview

5G Core Overview

hemraj3k
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5G Core Overview

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  1. Prepared: Hemraj Kumar Senior 5G Technology Consultant 5G Core Overview

  2. 5G Core Network Overview 2

  3. 3GPP 5GC (the only specification for a 5G mobile packet core) 3GPP’s 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. 3

  4. 3GPP 5GC (the only specification for a 5G mobile packet core) 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 access to local 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. The 5G architecture is defined as service-based and the interaction between network functions is represented in the following two ways: A service-based representation(SBA), 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). 4

  5. 3GPP 5G Core Network Standard Rel-15 5GS Phase1 Features Feature Category Detailed Function Service based architecture with service-based interfaces Data Storage architecture enabling Compute and Storage separation Support for AMF resiliency (e.g., AMF change with no service disruption) E2E Network Slicing Support for edge computing and URLLC services Local Area Data Network for specialized service § § Architectural enablers for virtualized deployment Network Architecture § § § § Enablers for new business opportunity New Enhancement Synergy with pre- installed LTE/Wi-Fi Multi-RAT Support Interworking with LTE/EPC Common interface for 3GPP and non-3GPP access § § Dynamic and finer control of QoS Differentiated mobility control for variety of devices Flow-based QoS framework Reflective QoS § § QoS Control Mobility Management Mobility restriction per UE Support for RRC inactive and MICO* mode § § Session model supporting ‘Session and Service Continuity’ modes Concurrent (e.g. local and central) access to a data network Application influence on traffic routing § Flexible and optimized network utilization Session Management § § 5

  6. 5G Core Implementation Unlike previous cellular generations, 5G implementation is based on:- • Cloud-native applications. • REST services-based integration. • Virtualized Network Functions. • Softwarization of Network & IT. • Support for Stateless Network functions by decoupling Compute and Storage. • Microservices based design patterns. • DevOps, CI/CD methodologies for faster time-to-market offerings. • Network slice-based approach of utilizing the physical network resources. • Mobile access edge computing for delivering & processing low latency contents & data. • Providing cellular connections to things & devices and supporting very high density. • Handling advanced analytics. • Separation of Control & User planes. • Network capability exposure via APIs and Service Bus. • Support for Centralized and Distributed processing. • etc. 6

  7. 5G Core Evolution 7

  8. 5G Core Evolution 5G Service Based (SBA/SBI/NAPS) Virtualization & Slicing Functional entities Softwarization/ Cloudification Single Core Application Programming Interfaces Dedicated protocols Harmonized protocols (HTTP …) Exposure to 3rdParties Backward & Forward Compatibility 8

  9. Deployment Scenario in South Korea Operator(KT and SK) The 5G NSA core network can be 2 or 3 in the figure below. In case of KT, it corresponds to 3. SK Telecom and LG U+ correspond to 2. 32

  10. Functional blocks within 5G Core Network Architecture AUSF = Authentication Server Function UDM = Unified Data Management NSSF = Network Slice Selection Function NEF = Network Exposure Function NRF = Network Repository Function AMF = Core Access and Mobility Management Function SMF = Session Management Function PCF = Policy Control Function AF = Application Function UE = User Equipment RAN = Radio Access Network CU = Centralised Unit DU = Distributed Unit UPF = User Plane Function DN = Data Network, e.g. operator services, Internet or 3rd party services 10

  11. NR Reference Point System Architecture AMF : - Core Access and Mobility Management Function UPF : - User plane Function SMF : - Session Management Control Function . DN : - Data Network (DN) NSSF : - Network Slice Selection Function. AUSF : - Authentication Server Function UDM : - Unified Data Management. PCF : - Policy Control Function. AF : - Application Function. Control Plane Entities User Plane Entities The Reference point Architecture is based upon a set of Network Elements. Reference Point Architecture uses point to point interfaces to interconnect those Network Elements. Signaling Procedures are specified between each point to point interface. LTE NW Architecture is an example of Reference Point Architecture. Network Function Spit for Flexible Network § Flexibility : AMF-SMF Split, CP-UP Separation § New I/F’s : AMF/SMF - Policy Function, AMF/SMF - Subscription DB § New NF’s : NSSF for Slice Selection, AUSF for EAP framework 11

  12. 5G interfaces (reference points) NG1: Reference point between the UE and the Access and Mobility Management function NG2: Reference point between the gNB and the Access and Mobility Management function NG3: Reference point between the gNB and the User plane function (UPF) NG4: Reference point between the Session Management function (SMF) and the User plane function (UPF) NG5: Reference point between the Policy Function (PCF) and an Application Function (AF) NG6: Reference point between the User Plane function (UPF) and a Data Network (DN) NG7: Reference point between the Session Management function (SMF) and the Policy Control function (PCF) NG8: Reference point between Unified Data Management and AMF NG9: Reference point between two Core User plane functions (UPFs) NG10: Reference point between UDM and SMF NG11: Reference point between Access and Mobility Management function (AMF) and Session Management function (SMF) NG12: Reference point between Access and Authentication Server function (AUSF) NG13: Reference point between UDM and Authentication Server function (AUSF) NG14: Reference point between 2 Access and Mobility Management function (AMF) NG15: Reference point between the PCF and the AMF in case of non-roaming scenario, V-PCF and AMF in case of roaming scenario Mobility Management function (AMF) and 12

  13. Service Based Architecture(SBA) Network The most outstanding change in the 5G Core Control plane is induction of Service based Interface (SBI) or Service based Architecture (SBA) from traditional Point-to-Point network architecture. With this new change, except for a few interfaces such as N2 and N4, almost every interface is now defined to use unified interface, using HTTP/2 protocol. Service based architecture is based on a set Network Functions (NFs) NFs provides services to other NFs Service Base Interface (SBI) Reference Point interface is replaced by a common bus to connect all NFs 13

  14. Service Based Architecture(SBA) Network Service Based Architecture is applicable to the control plane only. The user plane still remains Point to Point only. All the functions connect to the Bus- there is no point to point interface defined now. There is a common bus and through this bus all the Network Functions connect. The HOD of all the functions is Network Function Repository Function (NRF).All the Functions give their attendance to NRF saying – that I am a function A and I give this service. If any Function need any service it will ask NRF- who gives this service, so NRF contain details of all Network Elements and what all functions they give. Most likely all the Operators will go for Service Based Architecture and not for Reference Point Architecture. In Service based Architecture we have a common bus. The Nodes are called Network Functions In SBA, Network Functions (NFs) capabilities are exposed via REST APIs and based out of HTTP2.0 protocol. Interconnection between NFs can be based on the Request/Response model or Subscribe/Notify model for availing the different 5G Services. 14

  15. Service Based Architecture Network Network Functions within the 5GC Control Plane (CP) use Service-Based Interfaces (SBI) for their interactions: A CP NF can provide one or more NF Services Network Function(NF) § AF: Application Function § AMF: Access and Mobility Management Function § AUSF: Authentication Server Function § NEF: Network Exposure Function § NRF: Network Repository Function § PCF: Policy Control Function § SMF: Session Management Function § UDM: Unified Data Management § UPF.: User Plane Function UDM NEF AF NRF PCF Naf Nnef Nnrf Nudm Npcf SBI BUS Nausf Namf Nsmf SBI Control Plane AUSF AMF SMF N1 User Plane N2 N4 DataNetwork (e.g. operator or Internet) N6 N3 5G RAN NG UE UPF All interactions are abstracted as: Request-Response, Subscription-Notify procedures are described as a sequence of NF service invocations System 38

  16. Mapping NG Core and EPC Authentication Server Function (AUSF) and User DataManagement(UDM) PolicyControl Function(PCF) S6a MME HSS S1-MME PCRF N13 AUSF UDM PCF S11 Gx HSS/ AAAN8 PCRF N10 N7 N12 S1-U S5 SGi SGW PGW Access& Mobility managemen N tG11 FunctioAnM(FAMF) Session Management AfterCUPS SMF Function(SMF) S6a HSS MME PCRF S1-MME N15 SGW CP PGW CP Mapping the EPC functions to new 5G CNfunctions MME MME S11 Gx N4 SGW CP PGW CP User Plane FunctioUnPF(UPF) N3 N6 PGW UP SGW UP S1-U SGi PGW UP SGW UP 16

  17. 5GC Network Entities Functions AMF Function : The AMF performs most of the functions that the MME performs in a 4G network. Termination point for RAN CP interfaces (N2) § UE Authentication & Access Security. § Mobility Management (Reachability, Idle/Active Mode mobility state handling) § Registration Area management; § Access Authorization including check of roaming rights; § Session Management Function (SMF) selection § NAS signaling including NAS Ciphering and Integrity protection, termination of MM NAS and forwarding of SM NAS (N1). § AMF obtains information related to MM from UDM. § May include the Network Slice Selection Function (NSSF) § Attach procedure without session management adopted in CIoT defined also in 5GCN (registration management procedure) implemented in EPC is § User Plane (UP) selection and termination of N4 interface (AMF PGW functionality from EPC) has part of the MME and § 17

  18. 5GC Network Entities Functions SMF Function : The SMF performs the session management functions that are handled by the 4G MME, SGW-C, and PGW-C. Allocates IP addresses to UEs NAS signaling for session management (SM) Sends QoS and policy information to RAN via the AMF Downlink data notification Select and control UPF for traffic routing. The UPF selection function enables Mobile Edge Computing (MEC) by selecting a UPF close to the edge of the network. Acts as the interface for all communication related to offered user plane services. SMF determines how the policy and charging for these services is applied. Lawful intercept – control Plane PCF Function : The 5G PCF performs the same function as the PCRF in 4G networks. § Provides policy rules for control plane functions. This includes network slicing, roaming and mobility management. Accesses subscription information for policy decisions taken by the UDR. Supports the new 5G QoS policy and charging control functions. AUSF Function : The AUSF performs the authentication function of 4G HSS. § Implements the EAP authentication server Stores keys § § § § § § § § § 18

  19. 5GC Network Entities Functions UPF Function : The UPF is essentially a fusion of the data plane parts of the SGW and PGW. In the context of the CUPS architecture: EPC SGW-U + EPC PGW-U → 5G UPF . The UPF performs the following functions: Packet routing and forwarding § Packet inspection and QoS handling. The UPF may optionally integrate a Deep Packet Inspection (DPI) for packet inspection and classification. The following figure shows the classification and QoS handling at the UPF § Connecting to the Internet POP (Point of Presence). The UPF may optionally integrate the Firewall and Network Address Translation (NAT) functions. § Mobility anchor for Intra RAT and Inter-RAT handovers Lawful intercept — user plane Maintains and reports traffic statistics UDM Function : The UDM performs parts of the 4G HSS function. § Generation of Authentication and Key Agreement (AKA) credentials § User identification § Access authorization § Subscription management § 19

  20. 5GC CUPS Architecture 20

  21. 5G with CUPS Reconfiguring LTE network functions. Support for native CUPS. Virtualized NFs on commodity hardware based architecture. Distributed UPFs to edge to reduce latency and backhaul traffic. Enabling standard – based MEC by supporting routing to local UPFs located at edge sites. CUPS extended to RAN Enabling E2E network slicing by supporting independent parts for each service. MME MME + GW-C N11 AMF SMF NG RAN N4 N2 5GC NR Uu Data Network (e.g. operator or Internet) N3 N6 UPF gNB NR UE D U C U R U GW-U 21

  22. 5G Functions Synthesis 22

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