Linux Server / Performance, Capacity & Containers
Use TCP counter deltas to investigate a Linux server network slowdown
Retransmissions can reflect packet loss or congestion, but lifetime totals do not identify the current flow or time window.
Environment and inputs: Linux server baseline · Ubuntu 24.04 LTS / RHEL 9-style systems. Use the specified distribution, init system and installed tool; service names, privileges and supported options can differ.
Start with this check
Confirm the host, shell and access role. Replace sample names, paths, domains and interfaces with approved targets. These are diagnostic commands; assess policy and workload impact before making changes.
nstat -azRead the result
With iproute2 tools, this prints available network protocol counters. Values and reset behavior depend on tool options and network namespace.
Resolve and verify
Take timestamped samples during the incident and correlate deltas with interface and peer evidence. Investigate the actual affected path before changing TCP settings.
Before changing production
Do not infer that the server is at fault from one historical retransmission total or reset evidence before capture.