windows_exporter/docs/runbooks/windowsnetworkdiscards.md

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WindowsNetworkDiscards

Meaning

The sum of inbound and outbound discarded packet rates exceeds the configured threshold for 15 minutes. The default is one discard per second per interface. Discards count packets dropped without a packet error, such as buffer exhaustion.

Impact

Dropped packets can cause retransmissions, reduced throughput, and application timeouts. Some drops may be expected under a deliberate traffic policy.

Diagnosis

1. Inspect windows:net_received_discarded:rate and windows:net_outbound_discarded:rate to identify the direction and affected nic.
2. Compare traffic, directional utilization ratios, and windows_net_output_queue_length_packets with the normal baseline.
3. Inspect Get-NetAdapterStatistics, switch-port drops, adapter buffers, virtual switch counters, and network QoS policies.
4. Correlate drops with CPU pressure, traffic bursts, hypervisor contention, and application failures. An unknown or zero bandwidth estimate produces no utilization sample and should not be interpreted as zero traffic.

Mitigation

Relieve congestion, distribute traffic, or add bandwidth. Correct buffer, driver, or virtual switch problems when evidence identifies them. Review intentional drop policies with the network owner before changing thresholds. Confirm discard rates and application retransmissions return to the expected baseline.