Bug ID 458872: Check SACK report before treating as dupack

Last Modified: Oct 17, 2023

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

Known Affected Versions:
10.2.1, 10.2.2, 10.2.3, 10.2.4, 11.2.1, 11.4.1

Fixed In:
11.6.0, 11.5.4 HF2, 11.4.1 HF10

Opened: Apr 24, 2014

Severity: 4-Minor


TCP uses duplicate acks as a sign that data has left the network. When SACK is enabled, the SACK contains better information about this. When SACK indicates no data has left, do not execute duplicate ACK processing.


TCP sends data in excess of what is authorized by the congestion window.


SACK is enabled and duplicate ACKs arrive.


It's a mild performance impact, so no workaround is necessary.

Fix Information

Consider SACK information before dupack processing.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips