Need of caching on bind server

Harshith Mulky harshith.mulky at
Fri Aug 26 05:05:31 UTC 2016

Thank you John, Mukund, Barry and Dave for your insights and answers on this Topic.

@Dave, Lets say we have a Web Page cached(when queried by User 1) and the webpage has either moved the Link ( accessing the same Link from a different user would result in '504 Timeout' as it was cached by the Server)

So do we mean, every other user when querying the web page still gets the same link which was cached and now not reachable?

There should be some way, this should not happen

[P.S: I was trying a web link yesterday, and i got into this issue, but I was still able to open the cached web page link 2 days ago]



From: Woodworth, John R <John.Woodworth at>
Sent: Thursday, August 25, 2016 10:46 AM
To: 'Harshith Mulky'; bind-users at
Cc: Woodworth, John R
Subject: RE: Need of caching on bind server

> From: bind-users [mailto:bind-users-bounces at] On Behalf Of Harshith Mulky
> Sent: Thursday, August 25, 2016 12:47 AM
> To: bind-users at
> Subject: Need of caching on bind server
> Hello,
> I am trying to understand why caching is required on the bind server,
> when the client receiving the responses would be caching based on TTL
>  values.


I had the same question a number of years back and after gathering a fair
amount of statistics found we were seeing roughly 95% to 98% hit rates
for the cache.  This is a huge win when the answers are local to the
caching nameserver vs. recursively hitting the network again and again.

In the end if the site is unpopular (lower than 5% of nameserver traffic)
it does not really matter much but for everything else it will matter a
great deal.

My findings are likely an extreme case and the traffic of your nameservers
will depend greatly on the size of your client base so you may want to
run some tests of your own to see just how valuable the cache is.


> So,
> Is caching required on the server, if the client is not able to cache
> such responses? Isn't it a overhead on both the client and server
> systems to cache the same responses at respective ends
> What are the possible Use cases of caching the responses at the Server?
> What if there is a dynamic updates of Records on Server and Server
> still sends the cached Responses?

BTW: Dynamic or not, caching is an expected part of DNS and implementors
     should take this into careful consideration when implementing
     protocols relying on DNS as a service component.

> Thanks
> Harshith


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