Bug ID 458872: Check SACK report before treating as dupack

Last Modified: May 14, 2019

Bug Tracker

Affected Product:  See more info
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, 11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 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, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1

Fixed In:
11.6.0, 11.5.4 HF2, 11.4.1 HF10

Opened: Apr 24, 2014
Severity: 4-Minor

Symptoms

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.

Impact

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

Conditions

SACK is enabled and duplicate ACKs arrive.

Workaround

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

Fix Information

Consider SACK information before dupack processing.

Behavior Change