no more recursive clients: quota reached

[Stephane Bortzmeyer]

On Wed, Mar 24, 2010 at 05:08:01PM +0000,
 Chris Thompson <cet1 at cam.ac.uk> wrote 
 a message of 46 lines which said:

> It is the length of the queue of all outstanding recursive queries.
> This depends not just on the RATE of queries coming in, but also the
> time it takes to resolve them. (If the queue fills up, BIND gives up
> on the ones that have been outstanding longest.)

Yes, and it is the Baofeng attack 
<https://www.dns-oarc.net/files/workshop-200911/Ziqian_Liu.pdf>