Bug ID 629412: BIG-IP closes a connection when a maximum size window is attempted

Last Modified: Mar 17, 2021

Bug Tracker

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

Known Affected Versions:
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,,,,, 11.6.4, 11.6.5,,,, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2

Fixed In:
13.0.0, 12.1.2 HF1

Opened: Nov 18, 2016
Severity: 3-Major
Related AskF5 Article:


HTTP2 provides flow control options which allow you to limit the amount of data on flight. A client can send an increment for a window size to an initial value set by standard to 65,535 bytes. BIG-IP used 64K value inherited from SPDY, causing overflow when the client tried to increment the value to its maximum.


BIG-IP considers the window size overflow as a protocol violation thus it shuts the connection down not serving any request.


HTTP2 profile is configured on a virtual, and client sends a WINDOW_UPDATE frame to increment the value to its maximum.



Fix Information

With a correct value for initial window size (for both a connection and a stream) BIG-IP correctly processes an increment request of the window size to its maximum.

Behavior Change