TCP Retransmits

TCP retransmits can push a request over its latency budget without showing up clearly in application logs.

Symptom

bank-adapter p95 latency increased
some calls timed out

What kprobe shows

kprobe records TCP send, receive, and retransmit events for the process handling the request.

Example chain:

payment-api calls bank-adapter
  -> tcp_send
  -> tcp_retransmit
  -> delayed tcp_recv
  -> bank response arrives after timeout

Use this page when

• traces show a slow network dependency
• logs show intermittent timeout
• cloud metrics show no obvious host failure
• only some requests are affected