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PASSEDnetwork / qos_voice_traffic_misconfig
QoS Misconfiguration — Voice Traffic Not Prioritized
A switch firmware upgrade resets QoS policies on 12 access switches, removing DSCP marking and priority queuing for voice traffic. VoIP call quality degrades severely during business hours when data traffic competes with voice.
Pattern
VOIP_QUALITY
Severity
CRITICAL
Confidence
85%
Remediation
Remote Hands
Test Results
| Metric | Expected | Actual | Result |
|---|---|---|---|
| Pattern Recognition | VOIP_QUALITY | VOIP_QUALITY | |
| Severity Assessment | CRITICAL | CRITICAL | |
| Incident Correlation | Yes | 13 linked | |
| Cascade Escalation | N/A | No | |
| Remediation | — | Remote Hands — Corax contacts on-site support via call, email, or API |
Scenario Conditions
12 access switches upgraded to new firmware. QoS policies reset to default (no DSCP marking). Voice VLAN traffic competing with data on same queue. MOS scores dropping to 2.1 during peak hours. 200 VoIP phones affected. Jitter exceeding 80ms.
Injected Error Messages (2)
VoIP call quality severely degraded — voip jitter exceeding 80ms on calls through access switches, DSCP markings stripped after firmware upgrade, voice traffic no longer prioritized over data, MOS scores dropped to 2.1, voip calls experiencing choppy audio and dropped connections
PBX reporting widespread voip quality issues — 200 phones affected, jitter averaging 85ms during peak hours (threshold: 30ms), packet loss at 4% on voice VLAN, QoS policies missing on 12 access switches after firmware upgrade, voip queue statistics showing zero prioritized packets
Neural Engine Root Cause Analysis
The VoIP quality degradation is directly caused by a recent firmware upgrade on access switches that has stripped DSCP (Differentiated Services Code Point) markings from voice traffic. This has eliminated Quality of Service prioritization for VoIP packets, causing them to compete with data traffic on equal terms, resulting in excessive jitter (>80ms), poor MOS scores (2.1), and degraded call quality. The 8 correlated incidents suggest this is affecting multiple network segments or services simultaneously.
Remediation Plan
1. Immediately identify all access switches that received the recent firmware upgrade. 2. Check QoS configuration on these switches to verify DSCP marking preservation settings. 3. Reconfigure switches to trust and preserve DSCP markings from VoIP endpoints (typically DSCP 46 for voice, DSCP 26 for signaling). 4. Implement priority queuing for voice traffic with appropriate bandwidth allocation. 5. Test VoIP call quality and verify jitter measurements return to acceptable levels (<30ms). 6. If configuration changes don't resolve the issue, consider rolling back firmware to previous stable version. 7. Monitor MOS scores and validate they return above 4.0.
Tested: 2026-03-30Monitors: 2 | Incidents: 2Test ID: cmnck2ycg06cdobqew13prrwv