Network latency in distributed systems can originate from many sources: congested links, DNS resolution delays, TCP handshake overhead, and application-level serialization. A systematic troubleshooting approach is essential for isolating the root cause.
Diagnostic Tools and Techniques
Start with ping and traceroute to identify where latency spikes occur in the network path. MTR combines both tools into a continuous display that reveals intermittent issues missed by single-point measurements.
For application-layer latency, tools like tcpdump and Wireshark provide packet-level visibility. Analyzing TCP retransmissions, window sizes, and connection establishment times often reveals the true source of perceived slowness.
Implement distributed tracing with tools like Jaeger or Zipkin to track requests across microservices. These traces reveal which service calls contribute most to end-to-end latency, guiding optimization efforts to where they will have the greatest impact.