Bug ID 421948: BIG-IP keeps sending ICAP request after server response is done.

Last Modified: Apr 10, 2019

Bug Tracker

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

Known Affected Versions:
11.3.0, 11.4.0, 11.4.1

Fixed In:
11.5.0, 11.4.1 HF6

Opened: May 28, 2013
Severity: 3-Major
Related AskF5 Article:
K15593

Symptoms

If after receiving the preview the ICAP server returns 200-ok with an encapsulaed HTTP 302 redirect response, the BIG-IP system would continue sending the request body until its outgoing TCP window is drained as a result of the connection closing. The superfluous data flow to the server consumes resources longer than necessary which can cause performance loss.

Impact

Superfluous data flow from BIG-IP system to ICAP server, resulting in some performance degradation.

Conditions

ICAP server with preview returns HTTP 302 redirect.

Workaround

The ICAP server can ignore any trailing request data.

Fix Information

BigIP stops sending the ICAP request body immediately it sees the end of the ICAP server's response. If the end of the response is in the same frame as the 200-ok (which is normally the case for a short HTTP response like 302 redirect), no more bytes are sent beyond what was sent in the preview and the performance impact is eliminated (otherwise data might resume very briefly with less performance impact than before).

Behavior Change