ETCP Packet Core and Service Continuity 2 — Questions and Answers
Question 1: What is the role of the CHF (Charging Function) in Ericsson's 5G core?
- Charging the hardware components with firmware updates
- Collecting online/offline charging data from SMF/PCF and interfacing with the billing system (Correct answer)
- Managing CPU resource allocation for NF containers
- Providing secure boot for cloud-native NFs
Correct answer: Collecting online/offline charging data from SMF/PCF and interfacing with the billing system
The CHF (Charging Function) is the 5GC network function that processes charging triggers from the SMF and PCF, converging online (real-time credit control) and offline (CDR-based) charging.
Question 2: In Ericsson's EPC, what is the Gx interface used for?
- Carrying user plane data between SGW and PGW
- Carrying policy and charging control messages between the PCRF and PGW (PCEF) (Correct answer)
- Providing authentication between MME and HSS
- Synchronizing time between core nodes
Correct answer: Carrying policy and charging control messages between the PCRF and PGW (PCEF)
The Gx interface is a Diameter-based interface between the PCRF and the PGW's PCEF, used to push QoS rules and charging policies per session.
Question 3: What does 'CUPS' (Control and User Plane Separation) enable in Ericsson's evolved packet core?
- Separating SGW and PGW control plane functions from their user plane functions, allowing them to scale independently (Correct answer)
- Physically separating the MME from the HSS for redundancy
- Separating the RAN control plane from the transport layer
- Isolating billing data from subscriber management data
Correct answer: Separating SGW and PGW control plane functions from their user plane functions, allowing them to scale independently
CUPS decouples the control plane (SGW-C, PGW-C) from the user plane (SGW-U, PGW-U), enabling the user plane to be distributed closer to the network edge while control remains centralized.
Question 4: In Ericsson's 5G, what is the LADN (Local Area Data Network) feature?
- A low-power access technology for IoT devices
- A PDU session type that gives UEs access to a local data network only when within a specific geographic area (Correct answer)
- A link aggregation feature for the N3 interface
- A private network slice for enterprise customers
Correct answer: A PDU session type that gives UEs access to a local data network only when within a specific geographic area
LADN allows UEs to connect to local data networks (e.g., factory systems) only when physically within the LADN service area, supporting MEC and Industry 4.0 use cases.
Question 5: Which Ericsson feature supports handing off a VoLTE call from LTE to the PSTN when the subscriber moves out of LTE coverage?
- SRVCC (Single Radio Voice Call Continuity) (Correct answer)
- eSRVCC only for IMS-centralized services
- VoWiFi roaming anchor
- Direct Tunnel optimization
Correct answer: SRVCC (Single Radio Voice Call Continuity)
SRVCC (Single Radio Voice Call Continuity) allows an active IMS voice call to be transferred from the LTE/IMS packet domain to the circuit-switched WCDMA/GSM domain without dropping the call.
Question 6: In Ericsson's multi-access edge computing (MEC) deployments, where is the UPF typically placed?
- In the centralized data center only
- At or near the RAN edge (e.g., in the DU/CU site) to minimize latency for local applications (Correct answer)
- At the internet exchange point
- Co-located with the HSS/UDM for authentication proximity
Correct answer: At or near the RAN edge (e.g., in the DU/CU site) to minimize latency for local applications
For MEC use cases, the UPF is deployed at the RAN edge so that user plane traffic is offloaded locally without traversing the central core, achieving ultra-low latency.
ETCP Packet Core and Service Continuity 2
What is the role of the CHF (Charging Function) in Ericsson's 5G core?