Bug ID 760050: "cwnd too low" warning message seen in logs

Last Modified: Sep 23, 2022

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

Known Affected Versions:
15.1.0, 15.0.0, 14.1.0, 14.0.0.3, 13.1.1.2, 12.1.4, 11.6.3.3, 11.5.9

Fixed In:
16.0.0, 15.1.4, 14.1.2.7, 13.1.4.1

Opened: Feb 28, 2019

Severity: 3-Major

Symptoms

The following benign message appears in the log: "cwnd too low." The message can be seen in both tmm logs (where it shows as 'notice' severity) and also in the ltm log (where it shows as 'crit' (critical) severity).

Impact

None. TCP resets the congestion window to 1 MSS.

Conditions

The TCP congestion window has dropped below one Maximum Segment Size, which should not happen.

Workaround

This message does not indicate a functional issue, so you can safely ignore this message. There is no action to take, but the presence of the message can be useful information for debugging other TCP problems.

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips