Windows Server 2019 – tcpip.sys DPC latency spikes degrade throughput – Fix and Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution — Primary Fix
7. Solution — Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Throughput collapses during peak traffic with increased retransmits and delayed response times.

Environment & Reproduction

Observed on multi-NIC hosts with mixed offload settings.

Get-NetAdapterChecksumOffload
Get-NetAdapterLso
Get-NetAdapterRsc

Root Cause Analysis

Conflicting offload features and interrupt coalescing parameters drive high DPC processing overhead.

Quick Triage

Measure processor DPC time and check NIC driver release notes.

Get-Counter 'Processor(_Total)% DPC Time' -SampleInterval 2 -MaxSamples 10
driverquery /v | findstr /I ndis

Step-by-Step Diagnosis

Isolate problematic adapter by toggling advanced offload features one at a time.

Solution — Primary Fix

Disable unstable offloads, update driver, and apply balanced interrupt moderation profile.

Disable-NetAdapterLso -Name 'Ethernet'
Set-NetAdapterAdvancedProperty -Name 'Ethernet' -DisplayName 'Interrupt Moderation' -DisplayValue 'Enabled'
Restart-NetAdapter -Name 'Ethernet'

Solution — Alternative Approaches

Pin latency-sensitive traffic to dedicated adapters while broad tuning is completed.

Verification & Acceptance Criteria

DPC percentage and retransmit rate remain within baseline for one peak cycle.

Get-Counter 'TCPv4Segments Retransmitted/sec','Processor(_Total)% DPC Time' -SampleInterval 5 -MaxSamples 12

Rollback Plan

Restore previous adapter advanced-property export and reboot if regression appears.

Prevention & Hardening

Keep standardized offload profiles per hardware model and audit quarterly.

Related Errors & Cross-Refs

Often linked with NDIS filter conflicts and VMQ packet drops.

Related tutorial: View the step-by-step tutorial for Windows Server 2019.

View all Windows Server 2019 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Microsoft network performance tuning references for Windows Server 2019.