Bug ID 517393: Spurious RTO Detection Triggers Early Exit from Fast Recovery.

Last Modified: Apr 28, 2025

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
11.4.0, 11.4.1, 11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.1 HF10, 11.5.1 HF11, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 11.5.4 HF2, 11.5.4 HF3, 11.5.4 HF4, 11.5.5, 11.5.6, 11.5.7, 11.5.8, 11.5.9, 11.5.10, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 11.6.1 HF1, 11.6.1 HF2, 11.6.2, 11.6.2 HF1, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3

Opened: Apr 09, 2015

Severity: 3-Major

Related Article: K17507

Symptoms

When Fast Retransmit follows a spurious RTO, detection of the spurious RTO can overwrite Fast Recovery state and trigger premature exit. Spurious RTO detection can trigger crashes. Otherwise, in certain configurations, there can be an very slight decrease in performance.

Impact

Possible crashes. Otherwise, a very small decrease in performance in certain configurations.

Conditions

A step change in delay causes a spurious TCP RTO, accompanied by significant packet reordering and additional packet loss.

Workaround

Disable Early Retransmit.

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips