Nokia 5G Core Network KPI Optimization

V1 – 5G Core Network Architecture (3GPP TS 23.501)

The 5G Core (5GC) network implements a Service-Based Architecture (SBA) with cloud-native principles, separating user plane and control plane functions for enhanced scalability and flexibility.

3GPP Release 16+ Architecture Principles

Architecture Principle	3GPP Specification	Key Features	Nokia Implementation
Service-Based Architecture (SBA)	TS 23.501 §5.2	RESTful APIs, HTTP/2, JSON, Stateless NFs	Cloud-native, microservices-based
Control-User Plane Separation (CUPS)	TS 23.501 §5.8	Independent scaling, Distributed UPF	Centralized CP, Distributed UPF
Network Slicing	TS 23.501 §5.15	Logical networks, Slice-specific NFs	End-to-end slice orchestration
Edge Computing	TS 23.501 §5.13	Local UPF deployment, Low latency	Multi-tier UPF deployment
Network Exposure	TS 23.501 §5.20	NEF, API exposure to 3rd parties	Secure API framework

3GPP Compliance Note: This architecture follows 3GPP TS 23.501 Release 16 specifications. Nokia's 5G Core implements all mandatory Network Functions and reference points as defined in 3GPP standards, with additional optimizations for cloud-native deployment and network slicing.

V1 – Reference Points & Interfaces

5GC defines reference points (point-to-point) and service-based interfaces between network functions. Nokia implements these interfaces with specific protocols and optimizations.

Interface	Protocol	Endpoints	Primary Function	Nokia Implementation
N1	NAS over N1	UE ↔ AMF	Registration, Session Management, Mobility	5G NAS (TS 24.501)
N2	NGAP	gNB ↔ AMF	N2AP signaling, UE context transfer	NGAP over SCTP
N3	GTP-U	gNB ↔ UPF	User plane data tunneling	GTP-U v1 over UDP/IP
N4	PFCP	SMF ↔ UPF	Session control, QoS enforcement	PFCP (3GPP TS 29.244)
N6	IP	UPF ↔ DN	Connection to external data networks	IPv4/IPv6 with optional NAT
N11	HTTP/2	AMF ↔ SMF	Session management services	Service-Based Interface
N7	HTTP/2	SMF ↔ PCF	Policy control services	RESTful API with JSON
N8	HTTP/2	AMF ↔ UDM	Subscription data retrieval	Nudm services
N10	HTTP/2	SMF ↔ UDM	Session data management	Nudm services
N12	HTTP/2	AMF ↔ AUSF	Authentication services	Nausf services
N13	HTTP/2	UDM ↔ AUSF	Authentication data retrieval	Nudm services
N14	HTTP/2	AMF ↔ AMF	Inter-AMF communication	Namf services
N15	HTTP/2	AMF ↔ PCF	Policy control for AMF	Npcf services

Interface Monitoring Points

N2/N3: Monitored at gNB-UPF boundary for RAN-Core correlation
N4: Critical for session state synchronization
N6: External interface requiring security monitoring
SBI Interfaces: Monitored via HTTP/2 metrics and API analytics

V1 – Network Functions & Responsibilities

Network Function	Primary Responsibilities	Key Interfaces	Nokia Implementation	Scalability Consideration
AMF Access and Mobility Management Function	• UE registration, authentication • Connection and mobility management • NAS signaling termination • SMF selection	N1, N2, N8, N11, N12, N14, N15	Cloud-native, stateless with external UDSF	Horizontal scaling based on UE count
SMF Session Management Function	• PDU session establishment/modification • IP address allocation • UPF selection and control • QoS policy enforcement	N4, N7, N10, N11	Per-slice deployment, integrated with PCSCF	Scales with active sessions
UPF User Plane Function	• Packet routing and forwarding • QoS handling, packet inspection • Traffic usage reporting • Anchor point for mobility	N3, N4, N6, N9	Distributed, edge-optimized variants	Scales with throughput requirements
UDM Unified Data Management	• Subscription data management • Authentication credential handling • Service authorization	N8, N10, N13	Integrated with UDR (Unified Data Repository)	Highly available, read-intensive
PCF Policy Control Function	• Policy rules generation • QoS control, charging control • Network slice selection	N5, N7, N15, N28	Real-time policy engine with analytics	Scales with policy decision rate
AUSF Authentication Server Function	• 5G AKA authentication • EAP-AKA' procedures • Security anchor function	N12, N13	Integrated authentication framework	Scales with authentication requests
NRF NF Repository Function	• NF service registration • NF discovery and selection • NF profile maintenance	All SBI interfaces	High-availability cluster	Centralized, highly available
NSSF Network Slice Selection Function	• Network slice selection • Allowed NSSAI determination • AMF set selection	N22, N31	Slice management and orchestration	Scales with network slice complexity

Nokia 5GC Deployment Options

Centralized Deployment: All functions in central data center
Distributed Deployment: UPF at edge, control plane centralized
Hybrid Deployment: Multiple UPF tiers (national, regional, edge)
Network Slice-Specific: Dedicated functions per slice

V1 – Service-Based Communication (SBI) - 3GPP TS 29.500

Service-Based Architecture uses RESTful principles with HTTP/2, JSON, and OpenAPI specifications for communication between Network Functions. All SBI communications follow 3GPP TS 29.500 specifications.

3GPP SBI Specifications & Standards

Specification	Title	Key Requirements	Nokia Implementation
TS 29.500	5G System; Technical Realization of Service Based Architecture	SBI principles, HTTP/2 usage, API structure	Full compliance with SBA requirements
TS 29.501	5G System; Principles and Guidelines for Services Definition	API definitions, Data models, Error handling	OpenAPI 3.0 compliant APIs
TS 29.502	5G System; Session Management Services	Nsmf service operations	Complete SMF service implementation
TS 29.503	5G System; Unified Data Management Services	Nudm service operations	Full UDM service implementation
TS 29.504	5G System; Unified Data Repository Services	Nudr service operations	Integrated UDR services
TS 29.505	5G System; Policy Control Services	Npcf service operations	Complete PCF service implementation
TS 29.510	5G System; Network Function Repository Services	Nnrf service operations	NRF with service discovery
TS 29.518	5G System; Access and Mobility Management Services	Namf service operations	Complete AMF service implementation

SBI Communication Characteristics

Characteristic	3GPP Requirement	Protocol Details	Performance Impact
Transport Protocol	HTTP/2 (RFC 7540)	Multiplexing, header compression, server push	Reduced latency, efficient connection usage
Security	TLS 1.3 (RFC 8446)	Mutual authentication, forward secrecy	Secure communication with minimal handshake
Data Format	JSON (RFC 8259)	UTF-8 encoded, schema validation	Human readable, efficient parsing
API Definition	OpenAPI 3.0	YAML/JSON API specifications	Auto-generated clients, documentation
Service Discovery	Via NRF	Dynamic discovery, load balancing	Flexible deployment, high availability
Authentication	OAuth 2.0 / Mutual TLS	JWT tokens, NF-specific credentials	Secure inter-NF communication

3GPP Compliance: Nokia's SBI implementation strictly follows 3GPP TS 29.500 series specifications. All Network Functions expose services according to 3GPP-defined API specifications with HTTP/2 transport, TLS 1.3 security, and JSON payloads. Performance targets align with 3GPP TS 28.554 requirements.

V2 – Registration Procedure (3GPP TS 23.502 §4.2.2)

The Registration procedure establishes UE context in the 5G Core and provides the UE with access to network services. This procedure follows 3GPP TS 23.502 specifications for both initial registration and mobility registration scenarios.

3GPP Registration Procedure Details (TS 23.502 §4.2.2)

Step	Procedure Name	3GPP Interface	Key Information Elements	Condition
1-2	Registration Request	N1 (NAS) → N2 (NGAP)	SUCI/5G-GUTI, Registration Type, NSSAI	Mandatory
3-4	Identity Request/Response	N1 (NAS)	SUCI, SUPI, Identity Type	Conditional (if SUCI not provided)
5-9	Primary Authentication	N12 (AMF-AUSF) → N13 (AUSF-UDM)	Authentication Vector, RES, XRES	Mandatory for initial registration
10-11	NAS Security Mode Control	N1 (NAS)	Selected algorithms, ngKSI, NAS COUNT	Mandatory
12	Network Slice Selection	N22 (AMF-NSSF)	Requested NSSAI, Subscribed S-NSSAIs	Conditional (if slice selection needed)
13	AMF Registration to UDM	N8 (AMF-UDM)	AMF address, UE context, Access Type	Mandatory
14	AM Policy Association	N15 (AMF-PCF)	UE policy, Access Type, PRA info	Conditional (if AM policies needed)
15-16	Registration Accept/Complete	N1 (NAS) → N2 (NGAP)	5G-GUTI, Allowed NSSAI, TAI List	Mandatory
17	PDU Session Update	N11 (AMF-SMF)	UE location, AMF change indicator	Conditional (if existing PDU sessions)

Registration Parameters (3GPP TS 24.501)

NAS Timer	3GPP Default Value	Range	Purpose
T3510 (Registration)	15 seconds	5-30 seconds	Registration procedure timeout
T3512 (Periodic Registration)	54 minutes	6-310 minutes	Periodic registration update timer
T3517 (Mobile Initiated)	10 seconds	5-30 seconds	Mobile initiated registration
T3519 (Emergency Registration)	6 seconds	2-10 seconds	Emergency registration timer
T3520 (Authentication)	30 seconds	10-60 seconds	Authentication procedure timeout
T3521 (Security Mode)	6 seconds	3-10 seconds	Security mode control timeout

Registration Failure Causes (3GPP TS 24.501 §5.5.1.6)

5GMM Cause	Description	AMF Action	UE Action
#3 (Illegal UE)	UE identity not valid	Reject with cause, no retry allowed	Enter RM-DEREGISTERED
#6 (Illegal ME)	ME not allowed	Reject, notify UDM/EIR	No further attempts
#9 (UE identity cannot be derived)	SUCI decryption failure	Reject, check UDM connectivity	May retry with new SUCI
#11 (PLMN not allowed)	PLMN not in allowed list	Reject with PLMN list	Select other PLMN
#12 (Tracking area not allowed)	TA not in allowed list	Reject with new TAI list	Move to allowed TA
#13 (Roaming not allowed)	Roaming restriction	Reject, update UDM	Return to home PLMN
#15 (No suitable cells)	No appropriate RAT/cell	Reject with wait time	Wait before retry
#22 (Congestion)	Network congestion	Reject with back-off timer	Wait for timer expiry

3GPP Compliance Note: This registration procedure follows 3GPP TS 23.502 §4.2.2 for initial registration. All steps, timers, and failure causes are based on 3GPP TS 24.501 (5G NAS specification). Nokia's implementation includes optimizations for parallel processing where allowed by 3GPP specifications to reduce registration latency.

V2 – PDU Session Establishment

PDU Session Establishment creates a data connection between UE and Data Network through the 5G Core. Nokia's implementation supports multiple PDU session types and optimized path selection.

Step	Procedure	Key Parameters	Nokia Optimization	Failure Points
1	UE initiates PDU Session Establishment Request	PDU Session ID, DNN, S-NSSAI	Fast DNN validation, cached policies	Invalid DNN, unsupported S-NSSAI
2	SMF Selection by AMF	DNN, S-NSSAI, UE location	Weighted SMF selection based on load	SMF unavailable, load imbalance
3	SMF retrieves subscription data	SUPI, DNN, S-NSSAI	Cached subscription data, batch retrieval	UDM unreachable, invalid subscription
4	PCF policy decision	Session rules, QoS policies	Local policy cache, fallback policies	PCF overload, policy conflicts
5	UPF selection and N4 session establishment	UE location, DNN, required capabilities	Edge UPF selection for low latency	UPF unavailable, N4 setup failure
6	N2/N1 session establishment	QoS rules, PDU session info	Parallel N2/N1 signaling	gNB unreachable, QoS mismatch
7	Data path activation	UL/DL forwarding rules	Fast path activation, buffer management	Path setup timeout, resource exhaustion

PDU Session Types Supported

IPv4: Traditional IPv4 connectivity
IPv6: IPv6-only connectivity
IPv4v6: Dual-stack connectivity
Ethernet: Layer 2 Ethernet PDU
Unstructured: For non-IP applications

Performance Target: Nokia 5GC aims for PDU Session Establishment time < 500ms under normal load conditions, including all authentication and policy procedures.

V3 – Network Availability KPIs

Network Availability measures the readiness of 5GC network functions to serve UEs. Nokia provides comprehensive availability monitoring across all network functions.

KPI Category	KPI Name	Formula	Target	Measurement Method
NF Availability	AMF Service Availability	(Total Time - Downtime) / Total Time	99.999%	Heartbeat monitoring, service probes
	SMF Service Availability	(Available Sessions / Total Session Capacity)	99.99%	Session establishment attempts
	UPF Forwarding Availability	(Forwarded Packets / Received Packets)	99.999%	Packet counters, continuity checks
Interface Availability	N2 Interface Availability	(1 - NGAP Failure Rate)	99.99%	NGAP message success rate
Interface Availability	SBI Interface Availability	(Successful HTTP Requests / Total Requests)	99.95%	HTTP/2 request monitoring
Database Availability	UDR/UDSF Availability	(Successful Queries / Total Queries)	99.995%	Database query success rate
Geographic Redundancy	Geo-Redundant Availability	1 - (Site1 Downtime × Site2 Downtime)	99.9999%	Multi-site failure correlation

Availability Monitoring Points

NF Level: Process health, memory usage, CPU utilization
Service Level: API response time, success rate
Interface Level: Message success rate, latency
Database Level: Query performance, replication lag
Geographic Level: Site connectivity, disaster recovery

V3 – Registration Success Rate KPIs

Registration Success Rate measures the percentage of successful UE registrations against total registration attempts. This KPI is critical for network accessibility.

KPI Name	Counter Formula	Acceptable Threshold	Degraded Threshold	Root Cause Analysis
Initial Registration Success Rate	Successful Initial Registrations / Total Initial Registration Attempts	> 99.5%	< 98%	Authentication failures, AMF overload
Mobility Registration Success Rate	Successful Mobility Registrations / Total Mobility Registration Attempts	> 99.7%	< 99%	Inter-AMF handover issues, context transfer failures
Periodic Registration Success Rate	Successful Periodic Registrations / Total Periodic Registration Attempts	> 99.9%	< 99.5%	Timer mismatches, network instability
Emergency Registration Success Rate	Successful Emergency Registrations / Total Emergency Registration Attempts	> 99.99%	< 99.9%	Priority handling failures, resource allocation issues
Registration Failure by Cause	Count per Failure Cause / Total Failures	N/A	N/A	Categorized analysis for targeted optimization

Registration Failure Causes (3GPP TS 24.501)

Cause Value	Description	Common Root Cause	Corrective Action
#3	Illegal UE	Invalid IMSI/SUPI, blacklisted UE	Verify subscription data, update blacklists
#6	Illegal ME	Non-compliant UE equipment	Update EIR database, equipment validation
#9	UE identity cannot be derived	SUCI decryption failure	Check UDM connectivity, key synchronization
#11	PLMN not allowed	Roaming restrictions, invalid PLMN	Update roaming agreements, PLMN configuration
#12	Tracking area not allowed	TA not in allowed list	Update TA configuration, mobility settings
#13	Roaming not allowed	Roaming disabled for subscriber	Update subscription profile
#15	No suitable cells	No compatible RAT or frequency	Check RAT/frequency configuration
#22	Congestion	AMF/SMF overload	Scale resources, implement load balancing

V3 – Session Establishment KPIs (5GC)

Session Establishment KPIs measure the success, latency, and quality of PDU session setup in 5G Core. These KPIs are critical for user experience and network performance monitoring.

KPI Category	KPI Name	Formula	Target (Nokia 5GC)	Degraded Threshold	3GPP Reference
Success Rate	PDU Session Establishment Success Rate (Overall)	(Successful PDU Session Establishments / Total Attempts) × 100%	≥ 99.5%	< 98%	TS 28.552
	Initial PDU Session Success Rate	(Successful Initial PDU Sessions / Total Initial Attempts) × 100%	≥ 99.2%	< 97.5%	TS 28.552
	Handover PDU Session Success Rate	(Successful HO PDU Sessions / Total HO Attempts) × 100%	≥ 99.7%	< 99%	TS 28.552
	Emergency PDU Session Success Rate	(Successful Emergency Sessions / Total Emergency Attempts) × 100%	≥ 99.99%	< 99.9%	TS 28.552
Latency	PDU Session Establishment Time (50th Percentile)	Time from UE request to session ready	≤ 500 ms	> 800 ms	TS 28.554
	PDU Session Establishment Time (95th Percentile)	P95 of establishment time	≤ 800 ms	> 1200 ms	TS 28.554
	Service Request Time (Idle→Active)	Time from service request to data ready	≤ 100 ms	> 200 ms	TS 28.554
	SMF Decision Time	Time for SMF to make session decisions	≤ 50 ms	> 100 ms	Nokia Internal
Quality & Stability	Session Drop Rate (Abnormal Release)	(Abnormally Released Sessions / Total Active Sessions) × 100%	≤ 0.1%	> 0.5%	TS 28.552
	Session Modification Success Rate	(Successful Modifications / Total Modification Attempts) × 100%	≥ 99.8%	< 99%	TS 28.552
	Session Continuity During Handover	(Sessions Maintained During HO / Total HO Sessions) × 100%	≥ 99.9%	< 99.5%	TS 28.552
	QoS Flow Establishment Success Rate	(Successful QoS Flows / Total QoS Flow Attempts) × 100%	≥ 99.7%	< 99%	TS 28.552
Resource Utilization	SMF Session Capacity Utilization	(Active Sessions / Maximum Capacity) × 100%	≤ 80%	> 90%	Nokia Internal
	UPF Session Capacity Utilization	(Active UPF Sessions / UPF Capacity) × 100%	≤ 75%	> 85%	Nokia Internal
	PDU Session Setup Rate	Sessions established per second	≤ 1000/s	> 1500/s (capacity)	TS 28.552

Critical Failure Causes (3GPP TS 24.501)

Cause Code	Description	Common Root Causes	Resolution Priority
#26	Insufficient resources	UPF overload, SMF capacity exceeded	HIGH
#27	Missing or unknown DNN	DNN not configured, APN mismatch	MEDIUM
#28	Unknown PDU session type	UE requested unsupported PDU type	LOW
#29	User authentication or authorization failed	Policy rejection, subscription issue	HIGH
#31	Request rejected, unspecified	Generic rejection, often from SMF	MEDIUM
#35	Session establishment rejected due to network slice not available	Slice not allowed, NSSF failure	HIGH
#36	Session establishment rejected due to single-network slice selection only	UE limited to single slice	MEDIUM

Monitoring Strategy: Session establishment performance should be monitored by DNN, slice (S-NSSAI), and UE type. Different services have different latency requirements: eMBB (≤ 500ms), URLLC (≤ 50ms), and mMTC (≤ 2000ms).

V3 – Core Throughput KPIs (5GC)

Core Throughput KPIs measure data transfer performance through the 5G Core network, including user plane throughput, interface utilization, and packet processing efficiency.

KPI Category	KPI Name	Formula	Target (Nokia 5GC)	Degraded Threshold	Measurement Method
User Plane Throughput	Average Downlink Throughput per UE	Total DL Bytes / (Active UEs × Time)	≥ 100 Mbps	< 50 Mbps	UPF counters, per-UE measurement
	Average Uplink Throughput per UE	Total UL Bytes / (Active UEs × Time)	≥ 50 Mbps	< 20 Mbps	UPF counters, per-UE measurement
	Peak Cell Throughput (DL)	Maximum DL throughput in measurement period	≥ 2 Gbps	< 1 Gbps	UPF N3 interface counters
	Peak Cell Throughput (UL)	Maximum UL throughput in measurement period	≥ 1 Gbps	< 500 Mbps	UPF N3 interface counters
Interface Utilization	N3 Interface Utilization (DL)	(DL Throughput / N3 Link Capacity) × 100%	≤ 70%	> 85%	Interface counters, port monitoring
	N6 Interface Utilization (Total)	(Total Throughput / N6 Link Capacity) × 100%	≤ 60%	> 80%	Interface counters, port monitoring
	N4 Interface Message Rate	PFCP messages per second	≤ 1000 msg/s	> 2000 msg/s	SMF/UPF PFCP counters
	SBI Interface Throughput	HTTP/2 request rate	≤ 5000 req/s	> 10000 req/s	HTTP/2 monitoring, API analytics
Packet Processing	UPF Packet Processing Rate	Packets processed per second	≥ 10 Mpps	< 5 Mpps	UPF hardware/software counters
	Packet Drop Rate (UPF)	(Dropped Packets / Total Packets) × 100%	≤ 0.01%	> 0.1%	UPF buffer monitoring
	Buffer Utilization (UPF)	(Used Buffer / Total Buffer) × 100%	≤ 70%	> 90%	UPF memory monitoring
	Packet Reordering Rate	(Reordered Packets / Total Packets) × 100%	≤ 0.1%	> 1%	UPF sequence number checking
QoS-based Throughput	GBR Throughput Compliance	(Actual GBR Throughput / Required GBR) × 100%	≥ 95%	< 90%	Per-5QI throughput monitoring
	Non-GBR Throughput Fairness Index	Jain's Fairness Index across UEs	≥ 0.9	< 0.7	Statistical analysis of UE throughput
	5QI-1 (Voice) Packet Loss Rate	(Lost Packets / Total Packets) × 100%	≤ 0.1%	> 1%	Voice service monitoring
	5QI-6 (URLLC) Throughput Guarantee	(URLLC Sessions Meeting SLA / Total URLLC) × 100%	≥ 99.9%	< 99%	URLLC service monitoring
Throughput Distribution	Cell Edge Throughput (10th Percentile)	10th percentile of UE throughput	≥ 10 Mbps DL ≥ 5 Mbps UL	< 5 Mbps DL < 2 Mbps UL	Geographic throughput analysis
	Cell Center Throughput (90th Percentile)	90th percentile of UE throughput	≥ 500 Mbps DL ≥ 200 Mbps UL	< 200 Mbps DL < 100 Mbps UL	Geographic throughput analysis
	Throughput Standard Deviation	Std. Dev. of UE throughput distribution	≤ 50 Mbps	> 100 Mbps	Statistical analysis

Throughput Optimization: Core throughput issues are often misdiagnosed as RAN problems. Always verify UPF performance, buffer utilization, and QoS configuration before concluding RAN is the bottleneck. Nokia recommends monitoring throughput by 5QI to identify service-specific issues.

V3 – Core Latency KPIs (5GC)

Core Latency KPIs measure end-to-end delay through the 5G Core network, including control plane signaling, user plane data transfer, and QoS-specific latency targets.

KPI Category	KPI Name	Formula	Target (Nokia 5GC)	URLLC Target	Measurement Method
Control Plane Latency	Registration Time (Idle→Connected)	Time from Registration Request to Registration Complete	≤ 500 ms	≤ 100 ms	NAS message timestamps
	Service Request Time (Inactive→Active)	Time from Service Request to Data Ready	≤ 100 ms	≤ 20 ms	RRC/NAS timestamps
	AMF Processing Delay	AMF internal processing time per message	≤ 10 ms	≤ 5 ms	AMF internal timers
	SMF Policy Decision Time	Time for SMF to make policy decisions	≤ 50 ms	≤ 10 ms	SMF internal timers
	SBI Response Time (P95)	95th percentile of HTTP/2 response time	≤ 100 ms	≤ 50 ms	HTTP/2 monitoring
User Plane Latency	UE↔UPF Round Trip Time (RTT)	Packet round trip time between UE and UPF	≤ 20 ms	≤ 5 ms	Ping/ICMP measurements
	UPF Processing Delay	UPF packet processing time (per packet)	≤ 100 μs	≤ 50 μs	UPF hardware counters
	N3 Interface Delay (gNB↔UPF)	One-way delay on N3 interface	≤ 5 ms	≤ 2 ms	Interface timestamping
	N6 Interface Delay (UPF↔DN)	One-way delay on N6 interface	≤ 10 ms	≤ 5 ms	Interface timestamping
	End-to-End Latency (UE↔Server)	Complete path latency including internet	≤ 50 ms	≤ 10 ms	Application layer measurements
QoS-Specific Latency	5QI-1 (Voice) Packet Delay	One-way delay for voice packets	≤ 20 ms	N/A	Voice service monitoring
	5QI-2 (Video) Packet Delay	One-way delay for video packets	≤ 40 ms	N/A	Video service monitoring
	5QI-3 (Gaming) Packet Delay	One-way delay for gaming packets	≤ 30 ms	N/A	Gaming service monitoring
	5QI-6 (URLLC) Packet Delay	One-way delay for URLLC packets	≤ 10 ms	≤ 1 ms	Industrial IoT monitoring
Latency Variability	Packet Delay Variation (PDV) - 5QI-1	Jitter for voice services	≤ 5 ms	≤ 1 ms	Statistical analysis of delay
	Packet Delay Variation (PDV) - 5QI-6	Jitter for URLLC services	≤ 2 ms	≤ 0.5 ms	Statistical analysis of delay
	Latency Standard Deviation	Standard deviation of RTT measurements	≤ 5 ms	≤ 1 ms	Statistical analysis
	99th Percentile Latency	P99 of latency measurements	≤ 2 × P50 Latency	≤ 1.5 × P50 Latency	Statistical analysis
Mobility Latency	Handover Interruption Time	Time during which data cannot be transferred	≤ 50 ms	≤ 10 ms	Handover procedure timestamps
	Path Switch Delay (N2-based)	Time to switch user plane path	≤ 30 ms	≤ 5 ms	N2 message timestamps
	UPF Re-anchoring Time	Time to change UPF anchor point	≤ 100 ms	≤ 20 ms	N4 session modification time

Latency Optimization Techniques (Nokia 5GC)

Optimization Area	Technique	Expected Improvement	Complexity
UPF Processing	Fast path processing, hardware acceleration	50-80% reduction	HIGH (hardware upgrade)
Buffer Management	Smaller buffers, early congestion detection	20-40% reduction	MEDIUM (parameter tuning)
QoS Configuration	Priority queuing, expedited forwarding	10-30% reduction	LOW (configuration change)
SBI Optimization	HTTP/2 multiplexing, connection pooling	5-15% reduction	MEDIUM (NF configuration)
Edge Deployment	Place UPF closer to RAN	60-90% reduction	HIGH (architecture change)

Latency Monitoring Best Practice: Always measure latency in both directions (UL and DL) and at different percentiles (P50, P95, P99). Different applications have different latency requirements: interactive voice/video (< 150ms), online gaming (< 50ms), and industrial control (< 10ms).

V3 – Core Mobility KPIs (5GC)

Core Mobility KPIs measure handover success, interruption time, and service continuity during UE movement. These KPIs are critical for voice calls, real-time services, and seamless user experience.

KPI Category	KPI Name	Formula	Target (Nokia 5GC)	Degraded Threshold	3GPP Reference
Handover Success	Intra-gNB Handover Success Rate	(Successful Intra-gNB HOs / Total Attempts) × 100%	≥ 99.9%	< 99%	TS 28.552
	Inter-gNB Handover Success Rate	(Successful Inter-gNB HOs / Total Attempts) × 100%	≥ 99.7%	< 98.5%	TS 28.552
	Inter-AMF Handover Success Rate	(Successful Inter-AMF HOs / Total Attempts) × 100%	≥ 99.5%	< 98%	TS 28.552
	Inter-UPF Handover Success Rate	(Successful Inter-UPF HOs / Total Attempts) × 100%	≥ 99%	< 95%	TS 28.552
	Conditional Handover (CHO) Success Rate	(Successful CHOs / Total CHO Attempts) × 100%	≥ 99.8%	< 99%	TS 28.552
Handover Quality	Handover Interruption Time (P95)	95th percentile of data interruption during HO	≤ 50 ms	> 100 ms	TS 28.554
	Handover Preparation Time	Time from measurement report to HO command	≤ 100 ms	> 200 ms	TS 28.554
	Handover Execution Time	Time from HO command to HO complete	≤ 30 ms	> 60 ms	TS 28.554
	Path Switch Delay	Time to switch user plane path in core	≤ 20 ms	> 40 ms	TS 28.554
Mobility Robustness	Radio Link Failure (RLF) After Handover	(RLFs within 2s after HO / Total HOs) × 100%	≤ 0.5%	> 2%	TS 28.552
	Ping-Pong Handover Rate	(Ping-pong HOs / Total HOs) × 100%	≤ 1%	> 5%	TS 28.552
	Late Handover Rate	(Late HOs / Total HOs) × 100%	≤ 0.5%	> 2%	TS 28.552
	Early Handover Rate	(Early HOs / Total HOs) × 100%	≤ 0.5%	> 2%	TS 28.552
Service Continuity	Voice Call Drop Rate During HO	(Voice drops during HO / Total Voice HOs) × 100%	≤ 0.1%	> 0.5%	TS 28.552
	Video Streaming Interruption During HO	(Video interruptions during HO / Total Video HOs) × 100%	≤ 1%	> 5%	TS 28.552
	TCP Session Survival During HO	(TCP sessions surviving HO / Total TCP HOs) × 100%	≥ 99.9%	< 99%	TS 28.552
	QoS Flow Continuity During HO	(QoS flows maintained during HO / Total QoS HOs) × 100%	≥ 99.5%	< 98%	TS 28.552
Mobility Efficiency	Handover Frequency (per UE per hour)	Average number of HOs per UE per hour	≤ 5	> 10	TS 28.552
	Handover Signaling Load	N2 messages per handover	≤ 10 messages	> 20 messages	TS 28.552
	Mobility Registration Success Rate	(Successful Mobility Registrations / Total Attempts) × 100%	≥ 99.8%	< 99%	TS 28.552
	TAU/RAU Success Rate	(Successful TAUs/RAUs / Total Attempts) × 100%	≥ 99.9%	< 99.5%	TS 28.552
Advanced Mobility	Dual Connectivity (EN-DC) Success Rate	(Successful EN-DC setups / Total Attempts) × 100%	≥ 99%	< 95%	TS 28.552
	Network Slice Mobility Success	(Successful slice changes during mobility / Total) × 100%	≥ 98%	< 90%	TS 28.552
	Inter-RAT Mobility Success Rate	(Successful Inter-RAT HOs / Total Attempts) × 100%	≥ 99%	< 95%	TS 28.552

Handover Failure Causes (3GPP TS 38.413)

Cause Group	Specific Causes	Core Network Impact	Resolution Approach
Radio Network Layer	• Target cell not available • Radio link failure • Measurement reporting issues	Low (RAN issue)	RAN optimization, parameter tuning
Transport Network Layer	• N2 interface failure • Xn interface failure • Transport network congestion	Medium	Transport network optimization
Core Network Resources	• AMF overload • UPF resource exhaustion • SMF unavailable	High	Core capacity scaling, load balancing
Protocol Errors	• NGAP protocol error • NAS security mismatch • Timer expiry	Medium	Protocol stack debugging
Miscellaneous	• Handover cancellation • Invalid target cell • Unknown UE context	Variable	Root cause analysis per case

Mobility Optimization Strategy: Handover performance requires coordinated optimization between RAN and Core. Monitor both success rate AND interruption time. Use conditional handover for challenging scenarios and consider DAPS HO for mission-critical services requiring near-zero interruption.

V4 – AMF Configuration Parameters (Nokia 5GC)

AMF parameters control registration, mobility management, and NAS signaling behavior. Nokia provides extensive parameter tuning for performance optimization.

Parameter Category	Parameter Name	Default Value	Range	Optimization Impact
Registration Management	registrationTimer	54 min	6-310 min	Longer reduces signaling, shorter improves security
	implicitDeregistrationTimer	12 hours	1-24 hours	Controls stale UE context cleanup
	maxRegistrationRetransmission	5	3-10	More retries increase success but delay failure detection
	registrationGuardTimer	6 s	2-10 s	Protects against registration storms
Mobility Management	t3512 (Periodic RAU Timer)	54 min	6-310 min	Balances signaling load vs mobility tracking
	mobilityRestrictionTimer	12 s	5-30 s	Prevents ping-pong during handovers
	ueInactivityTimer	10 s	5-60 s	Shorter conserves resources, longer improves user experience
Security	nasIntegrityAlgorithm	NIA2	NIA0/1/2/3	NIA2 recommended for balance of security and performance
	nasCipheringAlgorithm	NEA2	NEA0/1/2/3	NEA2 provides good security with moderate overhead
	authFailureThreshold	3	1-10	Higher threshold reduces false blocks but increases risk
Load Management	maxUePerAmf	100,000	10,000-1,000,000	Scales based on AMF capacity and hardware
	maxPduSessionsPerUe	16	1-64	Limits per-UE resource consumption
	loadBalancingThreshold	80%	60-95%	Triggers load balancing to other AMFs
NAS Signaling	nasTimerT3510	15 s	5-30 s	Controls NAS message retransmission
NAS Signaling	nasTimerT3520	30 s	10-60 s	Security procedure timeout

Best Practice: Nokia recommends different parameter sets for different deployment scenarios: urban dense (shorter timers, higher capacity), rural (longer timers), and industrial (optimized for latency).

V4 – SMF Configuration Parameters (Nokia 5GC)

SMF parameters control session management, UPF selection, QoS enforcement, charging, and policy application. Nokia provides extensive parameter tuning for session optimization and resource management.

Parameter Category	Parameter Name	Default Value	Range	Optimization Impact
Session Management	sessionEstablishmentTimeout	5 s	1-30 s	Shorter timeout fails fast, longer accommodates network latency
	maxPduSessionsPerUe	16	1-64	Limits per-UE resource consumption, prevents overload
	defaultSessionType	IPv4	IPv4/IPv6/IPv4v6/Ethernet	Determines PDU session type for non-requesting UEs
	sessionInactivityTimer	10 s	5-3600 s	Shorter conserves UPF resources, longer maintains sessions
	emergencySessionPriority	Highest	Low/Medium/High/Highest	Ensures emergency sessions get resources first
UPF Selection	upfSelectionAlgorithm	RoundRobin	RoundRobin/LeastLoaded/Geographic/LowestLatency	Affects load distribution and latency optimization
	preferredUpfSet	All	UPF list	Directs traffic to specific UPFs for service requirements
	edgeUpfThreshold	20 ms	5-100 ms	Defines maximum latency for edge UPF selection
	upfFailureRetryCount	3	1-10	Number of retries before marking UPF as unavailable
QoS & Policy	default5Qi	9	1-254	Default QoS for non-specified sessions (9=best effort)
	qosEnforcementMode	Enforce	Monitor/Enforce/Strict	Controls how strictly QoS rules are applied
	arpPreemptionCapability	Enabled	Enabled/Disabled	Allows high-priority sessions to preempt resources
	maxBitRateEnforcement	Shaping	Shaping/Policing/Drop	How to handle sessions exceeding MBR
	gbrGuaranteePercentage	95%	80-100%	Target percentage of GBR to guarantee
Charging Configuration	chargingTriggerFunction	SMF	SMF/PCF/External	Determines which entity triggers charging events
	chargingDataCollectionInterval	300 s	60-3600 s	Frequency of charging data record generation
	quotaExhaustionAction	Terminate	Terminate/Throttle/Notify	Action when user quota is exhausted
	offlineChargingBufferSize	1000	100-10000	Number of CDRs to buffer before sending to CGF
N4 Interface (PFCP)	pfcpHeartbeatInterval	30 s	10-300 s	Frequency of PFCP heartbeat messages
	pfcpAssociationTimeout	60 s	30-300 s	Timeout for PFCP association responses
	pfcpMaxRetransmissions	3	1-10	Maximum PFCP message retransmissions
	pfcpResponseTimeout	5 s	1-30 s	Timeout for PFCP response messages
Load Balancing	smfLoadThreshold	80%	50-95%	Triggers load balancing to other SMFs
	sessionDistributionWeight	50	1-100	Weight for session distribution algorithm
	maxSessionsPerSmf	100000	1000-1000000	Maximum sessions per SMF instance
DNS & Addressing	dnsSelectionMethod	RoundRobin	RoundRobin/Priority/GeoBased	How to select DNS servers for UE
	ipAddressPoolExhaustionAction	Reject	Reject/Warn/Recycle	Action when IP address pool is exhausted
	ipAddressLeaseTime	86400 s	3600-2592000 s	Duration for which IP address is leased to UE

Optimization Tip: SMF parameters should be tuned based on service mix. For example, IoT deployments benefit from longer session timers and efficient IP address recycling, while enterprise deployments require strict QoS enforcement and low latency.

V4 – UPF Configuration Parameters (Nokia 5GC)

UPF parameters control packet processing, QoS enforcement, buffering, traffic management, and interface behavior. Nokia provides extensive tuning for throughput optimization and latency reduction.

Parameter Category	Parameter Name	Default Value	Range	Optimization Impact
Packet Processing	packetProcessingMode	FastPath	FastPath/SlowPath/Hybrid	FastPath for throughput, SlowPath for deep inspection
	maxPacketSize	1500 bytes	128-9600 bytes	Maximum packet size for processing (affects jumbo frames)
	packetReorderingBuffer	64 packets	16-1024 packets	Buffer size for packet reordering (critical for multi-path)
	fragmentationMode	Disabled	Disabled/Enabled/MTU-based	Enables packet fragmentation for path MTU issues
	checksumVerification	Enabled	Enabled/Disabled	Verifies packet checksums (CPU overhead vs error detection)
Buffer Management	bufferSizePerSession	1 MB	64 KB-100 MB	Buffer allocated per session (affects burst handling)
	sharedBufferSize	1 GB	100 MB-100 GB	Shared buffer pool for all sessions
	bufferWatermarkHigh	90%	70-95%	High watermark for buffer congestion control
	bufferWatermarkLow	50%	30-70%	Low watermark for buffer recovery
	earlyPacketDrop	Enabled	Enabled/Disabled	Drops packets early when buffer is full (RED-like)
QoS Enforcement	qosSchedulingAlgorithm	WFQ	FIFO/WFQ/SPQ/DWRR	Scheduling algorithm for QoS classes
	gbrGuaranteeAlgorithm	StrictPriority	StrictPriority/Weighted/Proportional	How GBR sessions are guaranteed their bandwidth
	mbrEnforcementMode	Shaping	Shaping/Policing/Drop	How to handle sessions exceeding MBR
	qosMarkingMode	TrustDSCP	TrustDSCP/Override/MarkBasedOn5Qi	How to mark packets for QoS
	congestionAvoidance	Enabled	Enabled/Disabled	Enables congestion avoidance algorithms (ECN, etc.)
Traffic Management	trafficShapingRate	Unlimited	1 Mbps-100 Gbps	Overall traffic shaping rate
	rateLimitingMode	PerSession	PerSession/PerUPF/PerQoS	Granularity of rate limiting
	burstSizeAllowance	200%	100-500%	Allowance for traffic bursts above average rate
	trafficMeasurementInterval	1 s	100 ms-10 s	Interval for traffic measurement and reporting
Interface Configuration	n3InterfaceMTU	1500 bytes	128-9600 bytes	MTU for N3 interface (gNB-UPF)
	n6InterfaceMTU	1500 bytes	128-9600 bytes	MTU for N6 interface (UPF-DN)
	tcpOptimization	Enabled	Enabled/Disabled	Enables TCP optimization (window scaling, etc.)
	interfaceQueueDepth	1000 packets	100-10000 packets	Depth of interface transmit queues
	linkAggregationMode	Disabled	Disabled/LACP/Static	Link aggregation for interface redundancy
Session Management	maxSessionsPerUpf	100000	1000-1000000	Maximum sessions supported by UPF
	sessionSetupRateLimit	1000/s	10-10000/s	Maximum session setup rate per second
	sessionInactivityTimer	30 s	5-3600 s	Time after which inactive sessions are cleaned up
	sessionCleanupBatchSize	100	10-1000	Number of sessions cleaned up in one batch
Statistics & Reporting	statsCollectionInterval	15 s	1-300 s	Interval for collecting statistics
	usageReportingThreshold	1 MB	64 KB-1 GB	Volume threshold for triggering usage reports
	qosMonitoringInterval	1 s	100 ms-10 s	Interval for QoS monitoring and reporting
	detailedLoggingLevel	Error	Error/Warning/Info/Verbose	Level of detail in UPF logs

Performance Tip: UPF buffer configuration significantly impacts latency and throughput. For low-latency applications, use smaller buffers with aggressive congestion control. For high-throughput applications, use larger buffers with intelligent scheduling.

V4 – Policy Control Parameters (Nokia 5GC)

PCF parameters control policy decision making, QoS rule generation, charging control, and network slice selection. Nokia provides sophisticated policy control with real-time analytics and dynamic rule adjustment.

Parameter Category	Parameter Name	Default Value	Range	Optimization Impact
Policy Decision	policyDecisionTimeout	2 s	1-10 s	Timeout for policy decision requests
	policyCacheTTL	300 s	60-3600 s	Time-to-live for cached policy decisions
	policyFallbackMode	DefaultRules	DefaultRules/LastKnown/Reject	Behavior when PCF is unavailable
	policyValidationMode	Strict	Strict/Lenient/Disabled	How strictly to validate policy rules
	dynamicPolicyAdjustment	Enabled	Enabled/Disabled	Enables dynamic policy adjustment based on network conditions
QoS Control	defaultSessionAmbrDl	1 Gbps	1 Mbps-100 Gbps	Default downlink AMBR for sessions
	defaultSessionAmbrUl	500 Mbps	1 Mbps-100 Gbps	Default uplink AMBR for sessions
	qosMappingTable	3GPP Default	Custom/3GPP Default/Operator Specific	Mapping between external QoS and 5QI
	arpPreemptionVulnerability	Enabled	Enabled/Disabled	Whether sessions can be preempted by higher ARP
	gbrAdjustmentFactor	1.0	0.5-2.0	Factor to adjust GBR based on network load
Charging Control	chargingTriggerDefault	VolumeAndTime	Volume/Time/VolumeAndTime/Event	Default charging trigger condition
	quotaManagementMode	Centralized	Centralized/Distributed/Hybrid	How quota is managed and enforced
	quotaValidityTime	3600 s	60-86400 s	Default validity time for granted quota
	lowBalanceThreshold	10%	1-50%	Threshold for low balance notifications
	chargingGracePeriod	30 s	0-300 s	Grace period after quota exhaustion
Network Slicing	sliceSelectionAlgorithm	SubscriptionBased	SubscriptionBased/ServiceBased/LocationBased	Algorithm for network slice selection
	defaultSliceSst	1	1-255	Default Slice/Service Type
	sliceIsolationLevel	ResourceLevel	None/PolicyLevel/ResourceLevel/Full	Level of isolation between network slices
	sliceFallbackEnabled	Enabled	Enabled/Disabled	Allows fallback to default slice if requested slice unavailable
	sliceCapacityThreshold	80%	50-95%	Threshold for slice capacity alerts
Access Control	accessControlMode	SubscriptionBased	SubscriptionBased/TimeBased/LocationBased	Mode for access control decisions
	roamingRestrictionLevel	None	None/HomeOnly/EmergencyOnly	Restrictions applied to roaming UEs
	dnnAccessControl	AllowAll	AllowAll/AllowList/BlockList	Access control for DNNs
	ratTypeRestriction	None	None/NROnly/NonNROnly	Restrictions based on RAT type
	emergencyAccessPriority	Highest	High/Highest	Priority for emergency access
Analytics & Optimization	analyticsCollectionInterval	60 s	10-3600 s	Interval for collecting analytics data
	predictivePolicyAdjustment	Enabled	Enabled/Disabled	Enables predictive policy adjustment based on analytics
	policyOptimizationCycle	3600 s	300-86400 s	Cycle time for policy optimization algorithms
	anomalyDetectionSensitivity	Medium	Low/Medium/High/VeryHigh	Sensitivity for anomaly detection in policy usage
Interface Configuration	n7InterfaceTimeout	5 s	1-30 s	Timeout for N7 interface (PCF-SMF)
	n5InterfaceTimeout	5 s	1-30 s	Timeout for N5 interface (PCF-AF)
	http2MaxConcurrentStreams	100	10-1000	Maximum concurrent HTTP/2 streams
	tlsSessionResumption	Enabled	Enabled/Disabled	Enables TLS session resumption for performance

Policy Strategy: PCF parameters should align with business policies. Consider different parameter sets for different customer segments: consumer (fair usage, quota management), enterprise (guaranteed QoS, SLAs), and IoT (efficient resource usage, bulk policy application).

V4 – Security Configuration Parameters (Nokia 5GC)

Security parameters control authentication, encryption, integrity protection, access control, and security monitoring across all 5GC network functions. Nokia implements comprehensive security with configurable protection levels.

Parameter Category	Parameter Name	Default Value	Range	Security Impact
Authentication	authenticationMethod	5G-AKA	5G-AKA/EAP-AKA'/EAP-TLS	Primary authentication method
	akaAuthenticationVectorLifetime	300 s	60-3600 s	Lifetime of AKA authentication vectors
	maxAuthFailures	3	1-10	Maximum authentication failures before blocking
	authFailureBlockTime	300 s	60-3600 s	Time to block UE after auth failures
	suciDecryptionKeyRotation	30 days	1-365 days	Frequency of SUCI decryption key rotation
NAS Security	nasIntegrityAlgorithm	NIA2	NIA0/NIA1/NIA2/NIA3	Integrity algorithm for NAS messages
	nasCipheringAlgorithm	NEA2	NEA0/NEA1/NEA2/NEA3	Ciphering algorithm for NAS messages
	nasSecurityCapability	NIA2,NEA2	Algorithm list	Supported NAS security capabilities
	nasKeyDerivationFunction	KDF2	KDF1/KDF2/KDF3	Key derivation function for NAS security
	nasSecurityIndication	Required	Required/Preferred/NotNeeded	Whether NAS security indication is required
User Plane Security	upIntegrityProtection	Preferred	Required/Preferred/NotNeeded	Integrity protection for user plane
	upConfidentialityProtection	Preferred	Required/Preferred/NotNeeded	Confidentiality protection for user plane
	upSecurityPolicy	Standard	Standard/Strict/Relaxed	Overall user plane security policy
	upKeyRefreshInterval	3600 s	300-86400 s	Interval for user plane key refresh
	upSecurityIndication	Enabled	Enabled/Disabled	Whether to indicate UP security to UE
TLS/HTTPS Security	tlsVersion	TLS 1.3	TLS 1.2/TLS 1.3	TLS version for SBI interfaces
	tlsCipherSuites	Strong	Strong/Medium/Compatible	Cipher suites for TLS connections
	tlsCertificateValidityCheck	Strict	Strict/Lenient/Disabled	How strictly to check TLS certificates
	tlsSessionResumptionTimeout	3600 s	300-86400 s	Timeout for TLS session resumption
	http2SecurityHeaders	Enabled	Enabled/Disabled	Security headers for HTTP/2 connections
Access Control	nfAccessControlMode	CertificateBased	CertificateBased/IPBased/TokenBased	Access control mode for NF interactions
	nfCertificateValidation	Strict	Strict/Lenient	How strictly to validate NF certificates
	ipWhitelistEnabled	Enabled	Enabled/Disabled	Enables IP whitelist for NF access
	accessTokenLifetime	3600 s	300-86400 s	Lifetime of OAuth 2.0 access tokens
	maxConcurrentSessionsPerNF	1000	10-10000	Maximum concurrent sessions per NF
Encryption & Key Management	encryptionAlgorithm	AES-256-GCM	AES-128/AES-256/ChaCha20	Encryption algorithm for sensitive data
	keyRotationInterval	24 hours	1-720 hours	Interval for key rotation
	keyStorageMode	HSM	HSM/Software/CloudKMS	Storage mode for cryptographic keys
	keyBackupEnabled	Enabled	Enabled/Disabled	Whether to backup encryption keys
	keyRecoveryMechanism	ShamirSecretSharing	ShamirSecretSharing/MultipleCopies	Mechanism for key recovery
Security Monitoring	securityLogLevel	Warning	Error/Warning/Info/Verbose	Log level for security events
	intrusionDetectionSensitivity	Medium	Low/Medium/High	Sensitivity for intrusion detection
	securityEventRetention	90 days	1-365 days	Retention period for security events
	anomalyDetectionEnabled	Enabled	Enabled/Disabled	Enables anomaly detection for security
	securityAlertThreshold	10 events/min	1-100 events/min	Threshold for security alerts
Audit & Compliance	auditLogEnabled	Enabled	Enabled/Disabled	Enables audit logging
	auditLogRetention	180 days	30-730 days	Retention period for audit logs
	complianceCheckInterval	24 hours	1-168 hours	Interval for compliance checks
	regulatoryComplianceMode	GDPR,CCPA	GDPR/CCPA/HIPAA/PCI-DSS	Regulatory compliance modes enabled

Security Best Practices: Nokia recommends different security profiles based on deployment: Standard (balanced security and performance), High Security (maximum protection with performance impact), and Regulated (compliance-focused with specific controls). Always align security parameters with organizational security policies and regulatory requirements.

V5 – AMF Performance Counters (Nokia 5GC)

AMF counters provide visibility into registration success, mobility events, NAS signaling, and resource utilization. These counters are essential for performance monitoring and troubleshooting.

Counter Category	Counter Name	Object	Description	Critical Threshold
Registration Counters	amfRegAttemptsInitial	AMF	Initial registration attempts	N/A
	amfRegSuccessInitial	AMF	Successful initial registrations	Success Rate < 99%
	amfRegAttemptsMobility	AMF	Mobility registration attempts	N/A
	amfRegSuccessMobility	AMF	Successful mobility registrations	Success Rate < 99.5%
	amfRegFailureCause[X]	AMF	Registration failures by cause code	Any cause > 1% of attempts
Mobility Counters	amfHandoverAttempts	AMF	Handover attempts	N/A
	amfHandoverSuccess	AMF	Successful handovers	Success Rate < 99.5%
	amfPathSwitchAttempts	AMF	Path switch attempts	N/A
	amfPathSwitchSuccess	AMF	Successful path switches	Success Rate < 99.7%
Session Counters	amfPduSessionAttempts	AMF	PDU session establishment attempts	N/A
	amfPduSessionSuccess	AMF	Successful PDU session establishments	Success Rate < 99%
	amfActivePduSessions	AMF	Currently active PDU sessions	> 90% of capacity
NAS Signaling	amfNasMessagesRx	AMF	NAS messages received	N/A
	amfNasMessagesTx	AMF	NAS messages transmitted	N/A
	amfNasMessagesDropped	AMF	NAS messages dropped	> 0.1% of total
Resource Utilization	amfCpuUtilization	AMF	CPU utilization percentage	> 80% sustained
	amfMemoryUtilization	AMF	Memory utilization percentage	> 85% sustained
	amfActiveUes	AMF	Currently active UEs	> 90% of capacity
	amfRegisteredUes	AMF	Currently registered UEs	> 95% of capacity
Interface Counters	amfN2MessagesRx	AMF	N2 messages received	N/A
	amfN2MessagesTx	AMF	N2 messages transmitted	N/A
	amfN2MessageErrors	AMF	N2 message errors	> 0.5% of total

V5 – SMF Performance Counters (Nokia 5GC)

SMF counters monitor session establishment success, policy enforcement, UPF control, and charging functionality. These counters are critical for session management performance and troubleshooting.

Counter Category	Counter Name	Object	Description	Critical Threshold
Session Management	smfPduSessionAttempts	SMF	Total PDU session establishment attempts	N/A
	smfPduSessionSuccess	SMF	Successful PDU session establishments	Success Rate < 99%
	smfPduSessionModifications	SMF	PDU session modification attempts	N/A
	smfPduSessionReleases	SMF	PDU session release attempts	N/A
	smfActivePduSessions	SMF	Currently active PDU sessions	> 90% of capacity
	smfSessionEstablishmentTime	SMF	Average session establishment time (ms)	> 500 ms
UPF Control (N4)	smfN4SessionCreateAttempts	SMF	N4 session creation attempts	N/A
	smfN4SessionCreateSuccess	SMF	Successful N4 session creations	Success Rate < 99.5%
	smfN4SessionModifications	SMF	N4 session modification attempts	N/A
	smfN4SessionDeletions	SMF	N4 session deletion attempts	N/A
	smfN4MessageErrors	SMF	N4 message errors (PFCP errors)	> 0.1% of total
Policy Control	smfPolicyRequests	SMF	Policy decision requests to PCF	N/A
	smfPolicyRequestSuccess	SMF	Successful policy requests	Success Rate < 99%
	smfPolicyUpdateAttempts	SMF	Policy update attempts	N/A
	smfPolicyUpdateSuccess	SMF	Successful policy updates	Success Rate < 99%
Charging	smfChargingRequests	SMF	Charging data requests	N/A
	smfChargingRequestSuccess	SMF	Successful charging requests	Success Rate < 99.5%
	smfChargingRecordsGenerated	SMF	Charging data records generated	N/A
	smfChargingRecordErrors	SMF	Charging record generation errors	> 0.5% of total
Resource Utilization	smfCpuUtilization	SMF	CPU utilization percentage	> 80% sustained
	smfMemoryUtilization	SMF	Memory utilization percentage	> 85% sustained
	smfSessionTableUtilization	SMF	Session table utilization (%)	> 90% sustained
	smfMaxSessionsSupported	SMF	Maximum sessions supported	N/A (capacity limit)
Interface Counters	smfN11MessagesRx	SMF	N11 messages received from AMF	N/A
	smfN11MessagesTx	SMF	N11 messages sent to AMF	N/A
	smfN7MessagesRx	SMF	N7 messages received from PCF	N/A

Monitoring Tip: SMF performance should be correlated with AMF and UPF counters. High session establishment failures at SMF may originate from AMF (N11 issues) or UPF (N4 issues).

V5 – UPF Performance Counters (Nokia 5GC)

UPF counters monitor user plane throughput, packet processing, QoS enforcement, and interface performance. These counters are essential for data plane optimization and capacity planning.

Counter Category	Counter Name	Object	Description	Critical Threshold
Throughput Counters	upfDlThroughputTotal	UPF	Total downlink throughput (Mbps)	> 90% of licensed capacity
	upfUlThroughputTotal	UPF	Total uplink throughput (Mbps)	> 90% of licensed capacity
	upfDlThroughputPerQci[1-9]	UPF	Downlink throughput per 5QI/QCI	Varies per QoS class
	upfUlThroughputPerQci[1-9]	UPF	Uplink throughput per 5QI/QCI	Varies per QoS class
	upfPeakThroughputDl	UPF	Peak downlink throughput (Mbps)	> 95% of licensed capacity
	upfPeakThroughputUl	UPF	Peak uplink throughput (Mbps)	> 95% of licensed capacity
Packet Counters	upfDlPacketsTotal	UPF	Total downlink packets processed	N/A
	upfUlPacketsTotal	UPF	Total uplink packets processed	N/A
	upfDlPacketDropRate	UPF	Downlink packet drop rate (%)	> 0.1%
	upfUlPacketDropRate	UPF	Uplink packet drop rate (%)	> 0.1%
	upfPacketProcessingLatency	UPF	Average packet processing latency (μs)	> 100 μs
Session Counters	upfActiveSessions	UPF	Currently active N4 sessions	> 90% of capacity
	upfSessionCreateAttempts	UPF	N4 session creation attempts	N/A
	upfSessionCreateSuccess	UPF	Successful session creations	Success Rate < 99.5%
	upfSessionModifications	UPF	Session modification attempts	N/A
	upfSessionDeletions	UPF	Session deletion attempts	N/A
QoS Counters	upfQosRuleViolations	UPF	QoS rule violation events	> 0.01% of packets
	upfGbrThroughputCompliance	UPF	GBR throughput compliance (%)	< 95%
	upfMbrEnforcementEvents	UPF	MBR enforcement (shaping) events	N/A (monitor trend)
	upfQosMarkingChanges	UPF	QoS marking/remarking events	N/A
Interface Counters	upfN3PacketsRx	UPF	N3 interface packets received	N/A
	upfN3PacketsTx	UPF	N3 interface packets transmitted	N/A
	upfN6PacketsRx	UPF	N6 interface packets received	N/A
	upfN6PacketsTx	UPF	N6 interface packets transmitted	N/A
	upfN4MessagesRx	UPF	N4 (PFCP) messages received	N/A
Resource Utilization	upfCpuUtilization	UPF	CPU utilization percentage	> 80% sustained
	upfMemoryUtilization	UPF	Memory utilization percentage	> 85% sustained
	upfBufferUtilization	UPF	Packet buffer utilization (%)	> 90% sustained
	upfPpsCapacity	UPF	Packets per second capacity	> 90% of capacity
Error Counters	upfGtpuErrorPackets	UPF	GTP-U error packets received	> 0.01% of total
	upfInvalidPackets	UPF	Invalid/malformed packets	> 0.001% of total
	upfDroppedPacketsBufferFull	UPF	Packets dropped due to buffer full	> 0

Capacity Planning: UPF capacity should be monitored across multiple dimensions: throughput (Gbps), sessions (count), packets per second (PPS), and concurrent bearers. Different applications stress different dimensions.

V5 – NRF Performance Counters (Nokia 5GC)

NRF counters monitor NF registration, service discovery, profile management, and SBI interface performance. As the central repository for NF discovery, NRF performance is critical for overall 5GC stability.

Counter Category	Counter Name	Object	Description	Critical Threshold
NF Registration	nrfNfRegistrationAttempts	NRF	NF registration attempts	N/A
	nrfNfRegistrationSuccess	NRF	Successful NF registrations	Success Rate < 99.9%
	nrfNfDeregistrationAttempts	NRF	NF deregistration attempts	N/A
	nrfNfRegistrationUpdates	NRF	NF registration update attempts	N/A
	nrfRegisteredNfs	NRF	Currently registered NFs	> 90% of capacity
NF Discovery	nrfDiscoveryRequests	NRF	NF discovery requests received	N/A
	nrfDiscoveryRequestSuccess	NRF	Successful discovery requests	Success Rate < 99.5%
	nrfDiscoveryResponseTime	NRF	Average discovery response time (ms)	> 50 ms
	nrfDiscoveryCacheHits	NRF	Discovery cache hits	Cache hit rate < 80%
	nrfDiscoveryCacheMisses	NRF	Discovery cache misses	N/A
NF Profile Management	nrfProfileReads	NRF	NF profile read operations	N/A
	nrfProfileUpdates	NRF	NF profile update operations	N/A
	nrfProfileDeletes	NRF	NF profile delete operations	N/A
	nrfProfileQueryComplexity	NRF	Average query complexity (NF attributes)	> 10 attributes per query
Subscription Management	nrfSubscriptionAttempts	NRF	NF status subscription attempts	N/A
	nrfSubscriptionSuccess	NRF	Successful subscriptions	Success Rate < 99%
	nrfActiveSubscriptions	NRF	Currently active subscriptions	> 80% of capacity
	nrfNotificationAttempts	NRF	NF status notifications sent	N/A
	nrfNotificationSuccess	NRF	Successful notifications	Success Rate < 99%
Resource Utilization	nrfCpuUtilization	NRF	CPU utilization percentage	> 70% sustained
	nrfMemoryUtilization	NRF	Memory utilization percentage	> 80% sustained
	nrfDatabaseConnections	NRF	Active database connections	> 90% of pool size
	nrfDatabaseQueryTime	NRF	Average database query time (ms)	> 20 ms
SBI Interface	nrfHttpRequestsTotal	NRF	Total HTTP requests received	N/A
	nrfHttpRequestsPerSecond	NRF	HTTP requests per second	> 90% of capacity
	nrfHttpErrorResponses	NRF	HTTP error responses (4xx, 5xx)	> 1% of total requests
	nrfHttpResponseTime	NRF	Average HTTP response time (ms)	> 100 ms
Replication & High Availability	nrfReplicationLag	NRF	Replication lag to standby (ms)	> 1000 ms
	nrfFailoverEvents	NRF	Failover events (active to standby)	> 1 per day
	nrfClusterHealth	NRF	Cluster health status (1=healthy, 0=unhealthy)	0 (unhealthy)

Performance Insight: NRF performance directly impacts all SBI communications. High discovery response times or HTTP errors at NRF can cause cascading failures across multiple network functions.

V5 – UDM Performance Counters (Nokia 5GC)

UDM counters monitor subscription data access, authentication support, and service authorization. As the central repository for subscriber data, UDM performance affects registration, session establishment, and mobility.

Counter Category	Counter Name	Object	Description	Critical Threshold
Subscription Data	udmSubsDataReadAttempts	UDM	Subscription data read attempts	N/A
	udmSubsDataReadSuccess	UDM	Successful subscription data reads	Success Rate < 99.9%
	udmSubsDataReadResponseTime	UDM	Average read response time (ms)	> 50 ms
	udmSubsDataUpdateAttempts	UDM	Subscription data update attempts	N/A
	udmSubsDataUpdateSuccess	UDM	Successful subscription data updates	Success Rate < 99.5%
	udmActiveSubscribers	UDM	Currently active subscribers	> 90% of capacity
Authentication	udmAuthDataRequests	UDM	Authentication data requests	N/A
	udmAuthDataRequestSuccess	UDM	Successful authentication data requests	Success Rate < 99.9%
	udmAuthDataResponseTime	UDM	Average auth data response time (ms)	> 30 ms
	udmSuciDecryptionAttempts	UDM	SUCI to SUPI decryption attempts	N/A
	udmSuciDecryptionSuccess	UDM	Successful SUCI decryptions	Success Rate < 99.5%
Service Authorization	udmAuthzRequests	UDM	Service authorization requests	N/A
	udmAuthzRequestSuccess	UDM	Successful authorization requests	Success Rate < 99.5%
	udmAuthzResponseTime	UDM	Average authorization response time (ms)	> 40 ms
	udmAuthzDeniedRequests	UDM	Authorization requests denied	> 5% of total (investigate)
Event Exposure	udmEventSubscriptions	UDM	Event subscription requests	N/A
	udmEventNotifications	UDM	Event notifications sent	N/A
	udmEventNotificationSuccess	UDM	Successful event notifications	Success Rate < 99%
	udmActiveEventSubscriptions	UDM	Currently active event subscriptions	> 80% of capacity
	udmEventTypesSupported	UDM	Number of event types supported	N/A
Interface Counters	udmN8MessagesRx	UDM	N8 messages received from AMF	N/A
	udmN8MessagesTx	UDM	N8 messages sent to AMF	N/A
	udmN10MessagesRx	UDM	N10 messages received from SMF	N/A
	udmN10MessagesTx	UDM	N10 messages sent to SMF	N/A
Resource Utilization	udmCpuUtilization	UDM	CPU utilization percentage	> 70% sustained
	udmMemoryUtilization	UDM	Memory utilization percentage	> 80% sustained
	udmDatabaseConnections	UDM	Active database connections	> 90% of pool size
	udmDatabaseQueryTime	UDM	Average database query time (ms)	> 25 ms
	udmCacheHitRate	UDM	Cache hit rate for subscription data (%)	< 80% (too many DB queries)
Error & Rejection Counters	udmInvalidSubscriberRequests	UDM	Requests for invalid/non-existent subscribers	> 1% of total requests
	udmDecryptionFailures	UDM	SUCI decryption failures	> 0.5% of decryption attempts
	udmDataInconsistencyErrors	UDM	Data inconsistency errors detected	> 0
	udmConcurrentRequestLimitExceeded	UDM	Concurrent request limit exceeded events	> 0

Troubleshooting Guidance: UDM performance issues often manifest as registration failures or delays. When troubleshooting, check UDM response times, database connectivity, and cache effectiveness. High invalid subscriber requests may indicate configuration issues in AMF/SMF.

V6 – Common 5GC Issues & Troubleshooting

Issue Category	Symptoms	Root Causes	Troubleshooting Steps	Resolution
Registration Failures	• High registration failure rate • UE stuck in "Registering" • Frequent re-registrations	• Authentication failures • AMF overload • Invalid subscription data • NAS security mismatch	1. Check AMF logs for failure cause 2. Verify UDM connectivity 3. Check NAS security configuration 4. Monitor AMF load	• Update subscription data • Scale AMF capacity • Align NAS security config • Implement load balancing
PDU Session Establishment Failures	• Session setup timeout • No IP address assigned • QoS flow setup failures	• SMF selection failure • UPF unavailable • Policy decision failure • DNN configuration error	1. Check SMF availability 2. Verify UPF connectivity 3. Review PCF logs 4. Validate DNN configuration	• Ensure SMF redundancy • Restore UPF connectivity • Fix policy rules • Correct DNN configuration
Handover Failures	• Call drops during mobility • High handover failure rate • Service interruption	• AMF context transfer failure • SMF not reachable • UPF path switch failure • Timer misconfiguration	1. Check inter-AMF communication 2. Verify SMF availability 3. Monitor N4 interface 4. Review mobility timers	• Fix AMF communication • Ensure SMF reachability • Repair N4 interface • Optimize mobility timers
High Latency	• Slow session establishment • Delayed NAS responses • High HTTP/2 response time	• Database latency • Network congestion • NF overload • Inefficient service discovery	1. Monitor database performance 2. Check network latency 3. Review NF load 4. Analyze SBI performance	• Optimize database queries • Improve network connectivity • Scale NFs • Implement caching
Throughput Degradation	• Reduced user data rates • UPF packet drops • Buffer congestion	• UPF resource exhaustion • QoS misconfiguration • Traffic shaping issues • Backhaul congestion	1. Monitor UPF resources 2. Check QoS enforcement 3. Review traffic policies 4. Analyze backhaul utilization	• Scale UPF capacity • Correct QoS configuration • Adjust traffic policies • Upgrade backhaul
SBI Communication Issues	• HTTP/2 timeouts • Service discovery failures • High API error rates	• NRF unavailable • TLS handshake failures • HTTP/2 connection issues • NF registration problems	1. Check NRF health 2. Verify TLS certificates 3. Monitor HTTP/2 connections 4. Review NF registration	• Restore NRF service • Renew TLS certificates • Fix HTTP/2 configuration • Re-register NFs

V6 – Core Network Interview Q&A

Question	Technical Answer	Follow-up Questions
What are the key differences between 4G EPC and 5G Core?	5GC introduces Service-Based Architecture (SBA), Control-User Plane Separation (CUPS), network slicing, cloud-native design, and enhanced QoS framework. Unlike EPC's point-to-point interfaces, 5GC uses RESTful APIs between NFs.	• How does SBA improve scalability? • What are the benefits of CUPS?
How does 5G Core support network slicing?	Through dedicated network slice instances with isolated resources, slice-specific NF instances, slice selection during registration (NSSAI), and end-to-end QoS differentiation per slice.	• How is slice isolation achieved? • What are the RAN-Core coordination requirements?
Explain the 5G registration procedure	UE initiates with Registration Request, AMF performs authentication via AUSF/UDM, establishes NAS security, retrieves subscription data, and may trigger PDU session establishment. The procedure includes identity verification, security activation, and context setup.	• What causes registration failures? • How is mobility handled during registration?
What is the role of NRF in 5GC?	NRF maintains NF profiles, enables service discovery, supports load balancing, and provides NF status monitoring. It's essential for SBA as NFs discover each other via NRF rather than static configuration.	• How does NRF handle NF failures? • What are the scalability considerations?
How does 5GC achieve low latency?	Through edge UPF deployment, optimized packet processing, reduced signaling steps, QoS framework with 5QI, and fast path activation. User plane latency targets < 10ms for URLLC.	• What are the key latency contributors? • How is latency measured and monitored?
Describe the PDU session establishment procedure	UE requests PDU session, AMF selects SMF, SMF retrieves policies from PCF, selects UPF, establishes N4 session, sets up data path, and configures QoS rules. The procedure creates an end-to-end bearer from UE to DN.	• What factors influence UPF selection? • How are multiple PDU sessions handled?
What are the key 5GC KPIs to monitor?	Registration success rate, PDU session success rate, handover success rate, UPF throughput, control plane latency, NF availability, interface error rates, and resource utilization.	• How are these KPIs collected? • What are typical threshold values?
How does 5GC handle mobility?	Through AMF-based mobility management, N2-based handovers, UPF re-anchoring for inter-UPF mobility, and path switching procedures. 5GC supports both intra- and inter-system mobility.	• What's the difference from 4G mobility? • How is session continuity maintained?

5G Core Network – Index

Nokia 5G Core Network KPI Optimization – Expert LevelV1