Packet Core 5G Functions
5G/4G Combo Core
AMF and MME – Access & Mobility Management Function, Mobility Management Entity
AMF and MME NFs are designed to support UE authentication, registration, reachability, mobility management and secure NAS signalling procedures with UE terminal, etc. for both 5G and 4G networks. While 5G AN is connected to AMF over N2 interface, LTE RAN connects with the MME node over S1-AP interface. To add on, the AMF function supports rich network slicing definitions essential for a 'Network as a Service' business model. Both AMF and MME integrate with LIMS system using standard procedures and protocols.
SMF/vGW-C – Session Management Function, virtual Gateway Control Plane
SMF/vGW-C (SGW-C+PGW-C) is responsible for session management of individual user session connected through 4G or 5G network. SMF/vGW-C selects and controls the UPF/vGW-U for data transfer, allocates IP addresses to UEs, performs QoS enforcement and policy control, reports usage to Charging function, etc. It also integrates with LIMS system using standard procedures and protocols.
UPF/vGW-U – User Plane Function, virtual Gateway User Plane
3GPP defined UPF/vGW-U (SGW-U+PGW-U) acts as a single data anchoring user plane node that handles all aspects of user plane packet processing between the Radio Access Network (RAN) and the Data Network (DN) through one or multiple instances. UPF, as an open framework, provides flexibility to integrate new SGi-LAN services quickly and offers a solution with zero-copy single hop packet processing.
PCF and PCRF – Policy Control Function, Policy and Charging Rules Function
Converged Policy Solution encompasses the functionality of 4G PCRF as well as 5G PCF as defined by 3GPP standards. These functions are responsible for policy creation, control, and enforcement in the 5G, 4G, IMS, Wi-Fi and FTTX networks. The 5G PCF provides service policy authorisation, control for access and mobility management, session management, and background data transfer policies.
SDM – Subscriber Data Management
SDM solutions authorize access to network services for multiple user types, ensuring service continuity across different access methods. It supports container-based legacy (2G/3G/4G) and 5G network functions for providing subscriber data management, mobility management, user security and authentication (SIM and non-SIM based), access authorization, and service authorization. Jio SDM consists of the following modules:
- UDM – Unified Data Management
- 5G-EIR – 5G Equipment Identity Register
- AUSF – Authentication Server Function
- HSS – Home Subscriber Server
- HLR – Home Location Register
Details of the individual components are described below.
UDM – Unified Data Management
UDM, as part of UE authentication procedures for 3GPP access, generates AKA authentication credentials and provides them to AUSF (Authentication Service Function) for subscriber authentication. Similarly, for non-3GPP access, EAP-AKA is supported. Subscriber identities, e.g. public identity (SUPI) and private identity (SUCI) stored in UDM, are used to perform user identification procedures. Based on the subscription data stored in UDM, service access is granted to UE. UDM also stores dynamic data of subscriber registration and session data to support session continuity.
5G-EIR – Equipment Identity Register
During subscriber identification procedure, 5G Core Network performs Physical Equipment Identity (PEI) check procedure. EIR maintains the devices' blacklist and grey list status and provides the same as and when requested by the consumer NF. 5G-EIR provides features to maintain the equipment status of the entire Type Allocation Code (TAC) as well as of individual PEIs. Additionally, it also supports the binding of subscriber identity with PEI/TAC.
AUSF – Authentication Server Function
AUSF supports authentication for 3GPP access and trusted/untrusted non-3GPP access. It provides UE authentication service to AMF. It supports both 5G AKA and EAP AKA procedures. On receiving the authentication request from AMF, AUSF triggers the request to fetch the authentication data from UDM. Jio AUSF supports features to recover from synchronization failure of security contexts. Protection of SoR (Steering of Roaming) information service is hosted on AUSF to update SoR information on UE through secured procedures.
HSS and HLR – Home Subscriber Server, Home Location Register
The HSS is one of the key network entity in 4G network which helps to perform UE authentication, access authorization, service authorization, subscriber data management, etc. for LTE, IMS and trusted/untrusted non-3GPP networks. The HSS has an inbuilt HLR to support 2G/3G global roaming subscriber and interconnect SMS services within the visited network.
NRF – Network Repository Function
NRF (Network Repository Function) is a central repository containing information of all network functions. It helps different NFs to discover and fetch information about other peer NFs available in the network. The discovery and authentication interfaces are implemented as per OAuth2 standards. It supports the registration and de-registration of NF instances. It maintains unique profiles and offered services for each NFs.
NSSF – Network Slice Selection Function
NSSF is a 3GPP defined NF which is one of the key components of 5G Core Network. NSSF selects different slice and service type as per the requirement of different networks/services.
BSF – Binding Support Function
BSF is a standard 3GPP entity, responsible for storing binding information of the connected subscribers and mapping PCF instances to manage the sessions. It is a 3GPP compliant solution placed inside the 5G Core Network to support PDU session binding for SMF sessions. BSF maintains a PDU session for each SMF Session being created for the Application Function and ensures that all relevant communication for that session goes to the same instance of PCF.
SMSF – Short Message Service Function
SMSF enables the transfer of SMS over NAS. It relay the message between UE and Short Message Service Centre (SMSC) through AMF. SMSF serves as the interface and bridge between 5G core network and the traditional SMSC for receiving and sending 5G NAS messages. SMSF also supports SMS related CDR and Lawful Interception.
Converged NEF and SCEF – Network Exposure Function, Service Capability Exposure Function
Converged NEF+SCEF facilitates secure, robust, developer-friendly access to network services and capabilities. This access is provided by a set of northbound RESTful (or web-style) APIs from the network domain to both internal (i.e., within the network operator’s trust domain) and external applications for enabling IoT services both in 4G and 5G networks. External exposure can be categorized as Monitoring capability, Provisioning capability, and Policy/Charging capability.
Additionally the NEF has appeared in the 5G standards as an intelligent, service-aware ‘border gateway’ that will enable the external AFs to communicate with the 5G Network Functions in a secure manner. The NEF exposes unified APIs to any other external business applications for interaction with the 5G network functions. It provides interfaces for monitoring, provisioning, and policy/charging functionalities in the 5G network. It allows the identification of the 5G network function suitable for configuring, detecting, and reporting the monitoring events to the authorised external party. Additionally, this capability can be used for exposing a UE’s mobility management context such as UE location, reachability, roaming status, and loss of connectivity.
CHF-PC – Charging Function Protocol Converter
CHF-PC acts as a protocol converter for interactions of 5G core with the existing diameter protocol-based OCS. The solution converts the HTTP/2 messages received from SMF and PCF in the 5G network, to diameter messages before forwarding them to OCS and vice versa. It is a bridge to use the existing OCS in 5GC without the support of HTTP/2 at the OCS end.
SCP – Service Communication Proxy
SCP resolves the challenges introduced by the 5G Service Based Architecture and provides features like congestion/overload control, traffic prioritisation, optimised routing, etc. It enables a service provider to get better visibility into the core network. The NF Service consumer may be configured to perform discovery of the target NF service producer directly or delegate the discovery of the target NF service producer to the SCP used for indirect communication.
DRA+SLF – Diameter Routing Agent, Subscriber Location Function
DRA is a 3GPP defined network function, introduced to address the handling of increased diameter traffic from multiple network functions of Evolved Packet Core (EPC) and IP Multimedia Subsystem (IMS). DRA implements an intelligent diameter relay agent functionality to handle distribution as well as load balancing of diameter traffic to destined diameter nodes in diverse requirement scenarios.
SLF functionality is included as part of DRA solution. This function is required to identify the Home Subscriber Server (HSS) serving specific subscribers. For all the 3GPP applications hosted on HSS, SLF determines the cluster/pseudo FQDN of the HSS based on subscriber’s identity e.g., IMSI/MSISDN/IMPI/IMPU etc.
SEPP – Service Edge Protection Proxy
The 5G system architecture introduced SEPP as an entity at the perimeter of the PLMN network to protect control plane traffic that is exchanged between different 5G PLMNs. The SEPP enables operators to achieve end-to-end confidentiality and integrity between source and destination networks. The 5G standards stipulate that a SEPP is a mandatory function for MNO interconnect for roaming between standalone 5G cores. The Security Edge Protection Proxy (SEPP) is a non-transparent proxy to message filtering and policing on inter-PLMN control plane interfaces. The SEPP protects the connection between Service Consumers and Service Producers from a security perspective.
LMF – Location Management Platform
5G LMF provides capabilities to carry out the UE tracking in 5G network. Location platform services facilitate continuous tracking and capturing of the UE’s current and past location details using different location tracking methods like ECID, OTDOA, NRPPa, AGNSS, etc. The LMF provides location information to the application functions by implementing 3GPP defined standard protocols. The location information includes key attributes like geodetic position, civic location, positioning methods, etc. LMF supports Emergency Location Protocols and provides location information to authorised emergency support bodies using MLP and OMA message exchanges.
GMLC – Gateway Mobile Location Centre
GMLC is placed inside the 5G Core Network to facilitate the information exchange related to UE location within the network elements. GMLC enables improved location accuracy by authorising the request coming from the external application related to the device positioning. GMLC is fully complied with the 3GPP standard procedures for periodic, triggered, and UE available location events support. It also provides support for authorisation and password management for the LCS client.
NWDAF – Network Data Analytics Function
NWDAF represents an operator-managed network analytics logical function. It can provide slice-specific network data analytics and network load information to any network function. It includes the capability of ingesting transactions as well as local analytics data of the other network functions into enterprise data lakes and convert this data into valuable insights or policy triggers to other peer nodes using an inbuilt machine learning engine.
UCMF – UE Capability Management Function
UCMF, a standard 3GPP entity, is responsible for storing either PLMN-assigned or manufacturer-assigned UE Radio Capability IDs of the connected user equipment and providing the information to AMF. It is placed inside the 5G Core Network to maintain unique list of UE capabilities. 3GPP has defined interface between UCMF and MME to optimize the radio signalling for UE radio capability over LTE network.
UDR – Unified Data Regulatory
UDR has distributed subscriber data repository, which provides HTTP/2 based interface to retrieve, create, update and delete data of 5G subscribers. It stores subscriptions for change notifications and provides procedures to unsubscribe change notifications. UDR hosts application business logic on the front-end MS, while on backend MS it has high performance, scalable database cluster, which supports both local redundancy and geo-redundancy.
UDSF – Unstructured Data Storage Function
Any data of a Network Function (NF), which is not defined by 3GPP and proprietary to NF vendor implementation, is categorised as unstructured data. UE-Context information, session information, etc., are classified as unstructured data. UDSF provides a REST interface over HTTP/2 to create, retrieve, update and delete unstructured data to the consumer NF. UDSF consists of front-end MS and in-memory data storage as back-end MS. Both front-end and back-end microservices can scale independently to meet the traffic requirements. The data is replicated in real-time on redundant back-end.
ESG - Emergency SMS Gateway
Emergency SMS Gateway (ESG) is a highly optimized, customisable and regulatory compliant solution. It helps carriers to comply with regulatory requirements like Emergency Response Support System (ERSS). It ensures the delivery of Emergency SMS to Public Safety Answering Points (PSAP) of visiting/roaming PLMN (Public Land Mobile Network) of the subscriber. Under an emergency situation, an app on the subscriber’s mobile captures the panic button action of the subscriber and initiate an Emergency SMS containing the GPS coordinates from the subscriber’s mobile. Based on the country specific scenario, this SMS is destined to a specific emergency number and is submitted to the network carrier’s SMSC. From the SMSC, SMS is routed to PSAP of the respective geographical region of the subscriber’s visited PLMN.
OCS - Online Charging System
Online Charging System (OCS) is the heart of a telecommunication network architecture; all the transactions within the system are linked with and processed by the OCS, such as the subscriber’s account balance and charging transactions. The network operator or service provider can use the OCS to enforce credit limits by automatically controlling service access and producing call data records (CDRs) in order to apply the correct charges to the billing platform.
