It disables some of the network card's hardware offloading. Some have occasional faults, as low as every 4TB of data. The corrupt packets has valid TCP CRC. Commonly first spotted with an ssh error of "Corrupted MAC on input"

Example of an OpenStack vendor guide recommending turning the offloading off: http://clouddoc.stratus.com/1.5.1.0/en-us/Content/Help/P03_S...

Downside is you may have slightly higher CPU usage and/or slightly lower network throughput, I personally have not noticed a significant drop in performance.