Bug ID 455553: ICMP PMTU handling causes multiple retransmissions

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP All(all modules)

Known Affected Versions:
10.2.4, 11.0.0, 11.1.0, 11.2.0, 11.2.1, 11.3.0, 11.4.0, 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

Fixed In:
11.6.0, 11.5.4 HF3, 11.5.1 HF5, 11.4.1 HF6, 11.2.1 HF15, 10.2.4 HF12

Opened: Apr 03, 2014
Severity: 3-Major
Related AskF5 Article:


When an improperly large TCP Maximum Segment Size (MSS) triggers ICMP PMTU messages, TCP responds by resending the entire send queue with the new MSS.


Large amounts of duplicate retransmission.


This occurs when you configure a path with an MTU less than 1500 Bytes and attempt a file transfer with initcwnd greater than 1.



Fix Information

No multiple retransmission of the entire send queue when the MSS size is improperly large.

Behavior Change