Coverage of metrics by OSI levels
<mermaid> graph LR
L1["L1 Physical<br/>NIC counters via system"] L2["L2 Data Link<br/>MAC, VLAN"] L3["L3 Network<br/>IP, IPSec ESP, GTP-U"] L4["L4 Transport<br/>TCP/UDP/SCTP"] L5["L5 Session<br/>GTPv2-C, IKEv2"] L6["L6 Presentation<br/>IKEv2/IPSec encryption, EAP-AKA'"] L7["L7 Application<br/>Diameter, service bearer ops"] Operations["Operations<br/>KPI, SLA, Capacity"] CX["CX Level<br/>Subscriber Experience"]
L1 --> L2 --> L3 --> L4 --> L5 --> L6 --> L7 --> Operations --> CX
style L1 fill:#e74c3c,color:#fff style L2 fill:#e67e22,color:#fff style L3 fill:#f39c12,color:#fff style L4 fill:#2ecc71,color:#fff style L5 fill:#1abc9c,color:#fff style L6 fill:#3498db,color:#fff style L7 fill:#9b59b6,color:#fff style Operations fill:#34495e,color:#fff style CX fill:#2c3e50,color:#fff
</mermaid>
Detailing metrics by level
OSI model:
| Level | Metrics | Examples |
|---|---|---|
| L1/L2 Physical / Data Link | - | Covered by a separate node_exporter or equivalent at the OS level (not included in the ePDG metrics list) |
| L3 Network / IPSec tunnels | 3 | epdg_gtpu_packets_total, epdg_gtpu_bytes_total, epdg_gtpu_errors_total — GTP-U data plane |
| L4 Transport | 1 | epdg_network_connection_status — TCP connections to nodes (PGW/AAA/HSS) |
| L5 Session | 3 | epdg_session_ike_sa_total, epdg_session_child_sa_total, epdg_session_gtp_sessions_total |
| L6 Presentation/Security | 3 | epdg_ikev2_messages_total, epdg_ikev2_request_duration_seconds, epdg_ikev2_errors_total — IKEv2/IPSec encryption and EAP-AKA authentication |
| L7 Application | 9 | epdg_diameter_* (SWm/SWx/S6b, 5 metrics), epdg_gtp_* (GTPv2-C, 4 metrics) |
Operator level:
| Level | Metrics | Examples |
|---|---|---|
| Operations | 11 | epdg_service_availability, epdg_service_uptime_seconds, epdg_app_* (3), epdg_system_* (4), epdg_config_* (2) |
| Customer Experience | 3 | epdg_service_attach_duration_seconds p95, epdg_service_attach_total (success rate), epdg_ikev2_request_duration_seconds p99 |
Level 9: Quality of VoWiFi service perception
| QoE indicator | Source metrics | Interpretation |
|---|---|---|
| VoWiFi connection time | epdg_service_attach_duration_seconds p95 | > 3 seconds — subscriber notices delay when switching to WiFi |
| Continuity of service | epdg_session_ike_sa_total delta | Mass discharge > 50 IKE SA = accessibility issue |
| Authentication success | ePDG_High_Attach_Failure_Rate alert rate | > 5% = HSS/AAA node problem |
| Delayed appointment bearer | epdg_gtp_request_duration_seconds{msg=create-session} p99 | > 500 ms — delayed availability of voice channel |
| GTP-U tunnel | epdg_gtpu_errors_total rate / epdg_gtpu_packets_total | > 0.1% = degradation of voice quality |
| IKEv2-reliability | epdg_ikev2_errors_total by type | NO_PROPOSAL_CHOSEN / AUTHENTICATION_FAILED — problems with certs / UE |
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