Queries aborted due to Quota

[Ben]

Hi,

I am monitoring rndc stats output and got

++ Resolver Statistics ++
[Common]
                82121 queries aborted due to quota
                 5987 failures in opening query sockets

What does it mean by queries aborted due to quota and failing in opening 
query socket ?

Is there any OS resource limitation or ?

BIND 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6


Regards,
Ben