Bug ID 686190: LRO performance impact with BWC and FastL4 virtual server

Last Modified: Jul 12, 2023

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

Known Affected Versions:

Fixed In:

Opened: Sep 28, 2017

Severity: 2-Critical


Using Bandwidth controller (BWC) might result in a very large drop in performance of up to 75%. In this release, Large receive offload (LRO) is enabled by default.


Very large performance impact to the BWC policy (up to 75%). For example, if the BWC policy rate limit is set to 100Mb, the actual rate limit could be 25Mb.


-- BWC is configured. -- Virtual server has a FastL4 profile assigned. -- LRO is enabled (enabled by default in 13.1.0).


Disabling LRO recaptures most of the performance degradation related to using FastL4. To disable LRO (this is a system-wide setting), run the following command: tmsh modify sys db tm.tcplargereceiveoffload value disable Important note: Although you can disable LRO to recapture much of the 13.0.0-level performance, you will likely still experience some impact: 2-5% for small files, 17-22% degradation for the '10 requests per connection' benchmark. The only guaranteed way to avoid performance degradation is to remain on version 13.0.0.

Fix Information


Behavior Change

Guides & references

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