Sudden Slowdowns
A path can run fast for minutes and then show a sudden latency spike, a jump in round trip time. Spikes are harder to chase than steady slowness because they come and go, so you must catch them in the act.
Where Spikes Come From
Several mechanisms add sudden delay.
- Queue buildup under a traffic burst makes packets wait in a router buffer.
- A route change can shift traffic onto a longer or busier path mid session.
- A garbage collection pause or a busy host can delay processing at an endpoint.
Telling a network spike from a host spike is the heart of the investigation.
Catching Them
Run a continuous per hop tool and watch which hop the latency appears at, since a spike at one hop that does not propagate may be that router deprioritizing replies. Compare network round trip time against application response time: if the network is steady but responses spike, the delay is in the host or application. Logging timestamps lets you line up a spike with a deploy, a backup job, or a traffic peak.
Key idea
Latency spikes are intermittent jumps in delay, so you catch them with continuous measurement and separate a network cause like queue buildup from a host cause like a pause by comparing network round trip time against application response time.