[dns-operations] Storm on the DNS

[Stephane Bortzmeyer]

On Tue, Dec 01, 2015 at 11:07:01AM +0800,
 Song Linjian (Davey) <songlinjian at gmail.com> wrote 
 a message of 188 lines which said:

> In the monitoring page the red block means unanswered packets ratio
> >70%, right ?

Yes. The default value of DNSmon is very high, but you can change it.

> I wondering the root server instance in that red region is up or
> down? if it is still up, the queries can not be routed to other
> server where the the probes shows green.

The server is up but unresponsive because of the load. As a result
most resolvers switch to another letter. (A few servers like A never
had a problem or may be were not attacked.)