How does a Client Verify if the DNS server is Alive or down

[Mark Andrews]

In message <20151020064204.GA13681 at fantomas.sk>, Matus UHLAR - fantomas writes:
> On 20.10.15 11:56, Harshith Mulky wrote:
> >How can a Client verify if the DNS Server is Running(named service is Runnin
> g) or Down?
> 
> Why should client know such info?
> The clients needs to have the answer - it sends message and if the server
> replies properly, it's up and running.
> 
> >Does it periodically send any messages to the server. What Kind of messages
> > are required by the client to be sent towards server to determine if the
> > DNS IP is reachable or not?
> 
> what is your problem?

My bet this a question from some course that Harshith has been
requested to answer.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org